move x509 tests into a module (#3889)

* move x509 tests into a module

This is just to make grouping things like test_ocsp, etc a bit simpler
in the future

* fix path

* pep8

1 files changed, 4036 insertions, 0 deletions

diff --git a/tests/x509/test_x509.py b/tests/x509/test_x509.py
new file mode 100644
index 00000000..533862ab
--- /dev/null
+++ b/tests/x509/test_x509.py
@@ -0,0 +1,4036 @@
+# This file is dual licensed under the terms of the Apache License, Version
+# 2.0, and the BSD License. See the LICENSE file in the root of this repository
+# for complete details.
+
+from __future__ import absolute_import, division, print_function
+
+import binascii
+import datetime
+import ipaddress
+import os
+import sys
+
+from asn1crypto.x509 import Certificate
+
+import pytest
+
+import pytz
+
+import six
+
+from cryptography import utils, x509
+from cryptography.exceptions import UnsupportedAlgorithm
+from cryptography.hazmat.backends.interfaces import (
+    DSABackend, EllipticCurveBackend, RSABackend, X509Backend
+)
+from cryptography.hazmat.primitives import hashes, serialization
+from cryptography.hazmat.primitives.asymmetric import dsa, ec, padding, rsa
+from cryptography.hazmat.primitives.asymmetric.utils import (
+    decode_dss_signature
+)
+from cryptography.x509.oid import (
+    AuthorityInformationAccessOID, ExtendedKeyUsageOID, ExtensionOID,
+    NameOID, SignatureAlgorithmOID
+)
+
+from ..hazmat.primitives.fixtures_dsa import DSA_KEY_2048
+from ..hazmat.primitives.fixtures_ec import EC_KEY_SECP256R1
+from ..hazmat.primitives.fixtures_rsa import RSA_KEY_2048, RSA_KEY_512
+from ..hazmat.primitives.test_ec import _skip_curve_unsupported
+from ..utils import load_vectors_from_file
+
+
+@utils.register_interface(x509.ExtensionType)
+class DummyExtension(object):
+    oid = x509.ObjectIdentifier("1.2.3.4")
+
+
+@utils.register_interface(x509.GeneralName)
+class FakeGeneralName(object):
+    def __init__(self, value):
+        self._value = value
+
+    value = utils.read_only_property("_value")
+
+
+def _load_cert(filename, loader, backend):
+    cert = load_vectors_from_file(
+        filename=filename,
+        loader=lambda pemfile: loader(pemfile.read(), backend),
+        mode="rb"
+    )
+    return cert
+
+
+@pytest.mark.requires_backend_interface(interface=X509Backend)
+class TestCertificateRevocationList(object):
+    def test_load_pem_crl(self, backend):
+        crl = _load_cert(
+            os.path.join("x509", "custom", "crl_all_reasons.pem"),
+            x509.load_pem_x509_crl,
+            backend
+        )
+
+        assert isinstance(crl, x509.CertificateRevocationList)
+        fingerprint = binascii.hexlify(crl.fingerprint(hashes.SHA1()))
+        assert fingerprint == b"3234b0cb4c0cedf6423724b736729dcfc9e441ef"
+        assert isinstance(crl.signature_hash_algorithm, hashes.SHA256)
+        assert (
+            crl.signature_algorithm_oid ==
+            SignatureAlgorithmOID.RSA_WITH_SHA256
+        )
+
+    def test_load_der_crl(self, backend):
+        crl = _load_cert(
+            os.path.join("x509", "PKITS_data", "crls", "GoodCACRL.crl"),
+            x509.load_der_x509_crl,
+            backend
+        )
+
+        assert isinstance(crl, x509.CertificateRevocationList)
+        fingerprint = binascii.hexlify(crl.fingerprint(hashes.SHA1()))
+        assert fingerprint == b"dd3db63c50f4c4a13e090f14053227cb1011a5ad"
+        assert isinstance(crl.signature_hash_algorithm, hashes.SHA256)
+
+    def test_invalid_pem(self, backend):
+        with pytest.raises(ValueError):
+            x509.load_pem_x509_crl(b"notacrl", backend)
+
+    def test_invalid_der(self, backend):
+        with pytest.raises(ValueError):
+            x509.load_der_x509_crl(b"notacrl", backend)
+
+    def test_unknown_signature_algorithm(self, backend):
+        crl = _load_cert(
+            os.path.join(
+                "x509", "custom", "crl_md2_unknown_crit_entry_ext.pem"
+            ),
+            x509.load_pem_x509_crl,
+            backend
+        )
+
+        with pytest.raises(UnsupportedAlgorithm):
+                crl.signature_hash_algorithm()
+
+    def test_issuer(self, backend):
+        crl = _load_cert(
+            os.path.join("x509", "PKITS_data", "crls", "GoodCACRL.crl"),
+            x509.load_der_x509_crl,
+            backend
+        )
+
+        assert isinstance(crl.issuer, x509.Name)
+        assert list(crl.issuer) == [
+            x509.NameAttribute(x509.OID_COUNTRY_NAME, u'US'),
+            x509.NameAttribute(
+                x509.OID_ORGANIZATION_NAME, u'Test Certificates 2011'
+            ),
+            x509.NameAttribute(x509.OID_COMMON_NAME, u'Good CA')
+        ]
+        assert crl.issuer.get_attributes_for_oid(x509.OID_COMMON_NAME) == [
+            x509.NameAttribute(x509.OID_COMMON_NAME, u'Good CA')
+        ]
+
+    def test_equality(self, backend):
+        crl1 = _load_cert(
+            os.path.join("x509", "PKITS_data", "crls", "GoodCACRL.crl"),
+            x509.load_der_x509_crl,
+            backend
+        )
+
+        crl2 = _load_cert(
+            os.path.join("x509", "PKITS_data", "crls", "GoodCACRL.crl"),
+            x509.load_der_x509_crl,
+            backend
+        )
+
+        crl3 = _load_cert(
+            os.path.join("x509", "custom", "crl_all_reasons.pem"),
+            x509.load_pem_x509_crl,
+            backend
+        )
+
+        assert crl1 == crl2
+        assert crl1 != crl3
+        assert crl1 != object()
+
+    def test_update_dates(self, backend):
+        crl = _load_cert(
+            os.path.join("x509", "custom", "crl_all_reasons.pem"),
+            x509.load_pem_x509_crl,
+            backend
+        )
+
+        assert isinstance(crl.next_update, datetime.datetime)
+        assert isinstance(crl.last_update, datetime.datetime)
+
+        assert crl.next_update.isoformat() == "2016-01-01T00:00:00"
+        assert crl.last_update.isoformat() == "2015-01-01T00:00:00"
+
+    def test_revoked_cert_retrieval(self, backend):
+        crl = _load_cert(
+            os.path.join("x509", "custom", "crl_all_reasons.pem"),
+            x509.load_pem_x509_crl,
+            backend
+        )
+
+        for r in crl:
+            assert isinstance(r, x509.RevokedCertificate)
+
+        # Check that len() works for CRLs.
+        assert len(crl) == 12
+
+    def test_revoked_cert_retrieval_retain_only_revoked(self, backend):
+        """
+        This test attempts to trigger the crash condition described in
+        https://github.com/pyca/cryptography/issues/2557
+        PyPy does gc at its own pace, so it will only be reliable on CPython.
+        """
+        revoked = _load_cert(
+            os.path.join("x509", "custom", "crl_all_reasons.pem"),
+            x509.load_pem_x509_crl,
+            backend
+        )[11]
+        assert revoked.revocation_date == datetime.datetime(2015, 1, 1, 0, 0)
+        assert revoked.serial_number == 11
+
+    def test_extensions(self, backend):
+        crl = _load_cert(
+            os.path.join("x509", "custom", "crl_ian_aia_aki.pem"),
+            x509.load_pem_x509_crl,
+            backend
+        )
+
+        crl_number = crl.extensions.get_extension_for_oid(
+            ExtensionOID.CRL_NUMBER
+        )
+        aki = crl.extensions.get_extension_for_class(
+            x509.AuthorityKeyIdentifier
+        )
+        aia = crl.extensions.get_extension_for_class(
+            x509.AuthorityInformationAccess
+        )
+        ian = crl.extensions.get_extension_for_class(
+            x509.IssuerAlternativeName
+        )
+        assert crl_number.value == x509.CRLNumber(1)
+        assert crl_number.critical is False
+        assert aki.value == x509.AuthorityKeyIdentifier(
+            key_identifier=(
+                b'yu\xbb\x84:\xcb,\xdez\t\xbe1\x1bC\xbc\x1c*MSX'
+            ),
+            authority_cert_issuer=None,
+            authority_cert_serial_number=None
+        )
+        assert aia.value == x509.AuthorityInformationAccess([
+            x509.AccessDescription(
+                AuthorityInformationAccessOID.CA_ISSUERS,
+                x509.DNSName(b"cryptography.io")
+            )
+        ])
+        assert ian.value == x509.IssuerAlternativeName([
+            x509.UniformResourceIdentifier(b"https://cryptography.io"),
+        ])
+
+    def test_signature(self, backend):
+        crl = _load_cert(
+            os.path.join("x509", "custom", "crl_all_reasons.pem"),
+            x509.load_pem_x509_crl,
+            backend
+        )
+
+        assert crl.signature == binascii.unhexlify(
+            b"536a5a0794f68267361e7bc2f19167a3e667a2ab141535616855d8deb2ba1af"
+            b"9fd4546b1fe76b454eb436af7b28229fedff4634dfc9dd92254266219ae0ea8"
+            b"75d9ff972e9a2da23d5945f073da18c50a4265bfed9ca16586347800ef49dd1"
+            b"6856d7265f4f3c498a57f04dc04404e2bd2e2ada1f5697057aacef779a18371"
+            b"c621edc9a5c2b8ec1716e8fa22feeb7fcec0ce9156c8d344aa6ae8d1a5d99d0"
+            b"9386df36307df3b63c83908f4a61a0ff604c1e292ad63b349d1082ddd7ae1b7"
+            b"c178bba995523ec6999310c54da5706549797bfb1230f5593ba7b4353dade4f"
+            b"d2be13a57580a6eb20b5c4083f000abac3bf32cd8b75f23e4c8f4b3a79e1e2d"
+            b"58a472b0"
+        )
+
+    def test_tbs_certlist_bytes(self, backend):
+        crl = _load_cert(
+            os.path.join("x509", "PKITS_data", "crls", "GoodCACRL.crl"),
+            x509.load_der_x509_crl,
+            backend
+        )
+
+        ca_cert = _load_cert(
+            os.path.join("x509", "PKITS_data", "certs", "GoodCACert.crt"),
+            x509.load_der_x509_certificate,
+            backend
+        )
+
+        verifier = ca_cert.public_key().verifier(
+            crl.signature, padding.PKCS1v15(), crl.signature_hash_algorithm
+        )
+        verifier.update(crl.tbs_certlist_bytes)
+        verifier.verify()
+
+    def test_public_bytes_pem(self, backend):
+        crl = _load_cert(
+            os.path.join("x509", "custom", "crl_empty.pem"),
+            x509.load_pem_x509_crl,
+            backend
+        )
+
+        # Encode it to PEM and load it back.
+        crl = x509.load_pem_x509_crl(crl.public_bytes(
+            encoding=serialization.Encoding.PEM,
+        ), backend)
+
+        assert len(crl) == 0
+        assert crl.last_update == datetime.datetime(2015, 12, 20, 23, 44, 47)
+        assert crl.next_update == datetime.datetime(2015, 12, 28, 0, 44, 47)
+
+    def test_public_bytes_der(self, backend):
+        crl = _load_cert(
+            os.path.join("x509", "custom", "crl_all_reasons.pem"),
+            x509.load_pem_x509_crl,
+            backend
+        )
+
+        # Encode it to DER and load it back.
+        crl = x509.load_der_x509_crl(crl.public_bytes(
+            encoding=serialization.Encoding.DER,
+        ), backend)
+
+        assert len(crl) == 12
+        assert crl.last_update == datetime.datetime(2015, 1, 1, 0, 0, 0)
+        assert crl.next_update == datetime.datetime(2016, 1, 1, 0, 0, 0)
+
+    @pytest.mark.parametrize(
+        ("cert_path", "loader_func", "encoding"),
+        [
+            (
+                os.path.join("x509", "custom", "crl_all_reasons.pem"),
+                x509.load_pem_x509_crl,
+                serialization.Encoding.PEM,
+            ),
+            (
+                os.path.join("x509", "PKITS_data", "crls", "GoodCACRL.crl"),
+                x509.load_der_x509_crl,
+                serialization.Encoding.DER,
+            ),
+        ]
+    )
+    def test_public_bytes_match(self, cert_path, loader_func, encoding,
+                                backend):
+        crl_bytes = load_vectors_from_file(
+            cert_path, lambda pemfile: pemfile.read(), mode="rb"
+        )
+        crl = loader_func(crl_bytes, backend)
+        serialized = crl.public_bytes(encoding)
+        assert serialized == crl_bytes
+
+    def test_public_bytes_invalid_encoding(self, backend):
+        crl = _load_cert(
+            os.path.join("x509", "custom", "crl_empty.pem"),
+            x509.load_pem_x509_crl,
+            backend
+        )
+
+        with pytest.raises(TypeError):
+            crl.public_bytes('NotAnEncoding')
+
+    def test_verify_bad(self, backend):
+        crl = _load_cert(
+            os.path.join("x509", "custom", "invalid_signature.pem"),
+            x509.load_pem_x509_crl,
+            backend
+        )
+        crt = _load_cert(
+            os.path.join("x509", "custom", "invalid_signature.pem"),
+            x509.load_pem_x509_certificate,
+            backend
+        )
+
+        assert not crl.is_signature_valid(crt.public_key())
+
+    def test_verify_good(self, backend):
+        crl = _load_cert(
+            os.path.join("x509", "custom", "valid_signature.pem"),
+            x509.load_pem_x509_crl,
+            backend
+        )
+        crt = _load_cert(
+            os.path.join("x509", "custom", "valid_signature.pem"),
+            x509.load_pem_x509_certificate,
+            backend
+        )
+
+        assert crl.is_signature_valid(crt.public_key())
+
+    def test_verify_argument_must_be_a_public_key(self, backend):
+        crl = _load_cert(
+            os.path.join("x509", "custom", "valid_signature.pem"),
+            x509.load_pem_x509_crl,
+            backend
+        )
+
+        with pytest.raises(TypeError):
+            crl.is_signature_valid("not a public key")
+
+        with pytest.raises(TypeError):
+            crl.is_signature_valid(object)
+
+
+@pytest.mark.requires_backend_interface(interface=X509Backend)
+class TestRevokedCertificate(object):
+    def test_revoked_basics(self, backend):
+        crl = _load_cert(
+            os.path.join("x509", "custom", "crl_all_reasons.pem"),
+            x509.load_pem_x509_crl,
+            backend
+        )
+
+        for i, rev in enumerate(crl):
+            assert isinstance(rev, x509.RevokedCertificate)
+            assert isinstance(rev.serial_number, int)
+            assert isinstance(rev.revocation_date, datetime.datetime)
+            assert isinstance(rev.extensions, x509.Extensions)
+
+            assert rev.serial_number == i
+            assert rev.revocation_date.isoformat() == "2015-01-01T00:00:00"
+
+    def test_revoked_extensions(self, backend):
+        crl = _load_cert(
+            os.path.join("x509", "custom", "crl_all_reasons.pem"),
+            x509.load_pem_x509_crl,
+            backend
+        )
+
+        exp_issuer = [
+            x509.DirectoryName(x509.Name([
+                x509.NameAttribute(x509.OID_COUNTRY_NAME, u"US"),
+                x509.NameAttribute(x509.OID_COMMON_NAME, u"cryptography.io"),
+            ]))
+        ]
+
+        # First revoked cert doesn't have extensions, test if it is handled
+        # correctly.
+        rev0 = crl[0]
+        # It should return an empty Extensions object.
+        assert isinstance(rev0.extensions, x509.Extensions)
+        assert len(rev0.extensions) == 0
+        with pytest.raises(x509.ExtensionNotFound):
+            rev0.extensions.get_extension_for_oid(x509.OID_CRL_REASON)
+        with pytest.raises(x509.ExtensionNotFound):
+            rev0.extensions.get_extension_for_oid(x509.OID_CERTIFICATE_ISSUER)
+        with pytest.raises(x509.ExtensionNotFound):
+            rev0.extensions.get_extension_for_oid(x509.OID_INVALIDITY_DATE)
+
+        # Test manual retrieval of extension values.
+        rev1 = crl[1]
+        assert isinstance(rev1.extensions, x509.Extensions)
+
+        reason = rev1.extensions.get_extension_for_class(
+            x509.CRLReason).value
+        assert reason == x509.CRLReason(x509.ReasonFlags.unspecified)
+
+        issuer = rev1.extensions.get_extension_for_class(
+            x509.CertificateIssuer).value
+        assert issuer == x509.CertificateIssuer(exp_issuer)
+
+        date = rev1.extensions.get_extension_for_class(
+            x509.InvalidityDate).value
+        assert date == x509.InvalidityDate(datetime.datetime(2015, 1, 1, 0, 0))
+
+        # Check if all reason flags can be found in the CRL.
+        flags = set(x509.ReasonFlags)
+        for rev in crl:
+            try:
+                r = rev.extensions.get_extension_for_class(x509.CRLReason)
+            except x509.ExtensionNotFound:
+                # Not all revoked certs have a reason extension.
+                pass
+            else:
+                flags.discard(r.value.reason)
+
+        assert len(flags) == 0
+
+    def test_no_revoked_certs(self, backend):
+        crl = _load_cert(
+            os.path.join("x509", "custom", "crl_empty.pem"),
+            x509.load_pem_x509_crl,
+            backend
+        )
+        assert len(crl) == 0
+
+    def test_duplicate_entry_ext(self, backend):
+        crl = _load_cert(
+            os.path.join("x509", "custom", "crl_dup_entry_ext.pem"),
+            x509.load_pem_x509_crl,
+            backend
+        )
+
+        with pytest.raises(x509.DuplicateExtension):
+            crl[0].extensions
+
+    def test_unsupported_crit_entry_ext(self, backend):
+        crl = _load_cert(
+            os.path.join(
+                "x509", "custom", "crl_md2_unknown_crit_entry_ext.pem"
+            ),
+            x509.load_pem_x509_crl,
+            backend
+        )
+
+        ext = crl[0].extensions.get_extension_for_oid(
+            x509.ObjectIdentifier("1.2.3.4")
+        )
+        assert ext.value.value == b"\n\x01\x00"
+
+    def test_unsupported_reason(self, backend):
+        crl = _load_cert(
+            os.path.join(
+                "x509", "custom", "crl_unsupported_reason.pem"
+            ),
+            x509.load_pem_x509_crl,
+            backend
+        )
+
+        with pytest.raises(ValueError):
+            crl[0].extensions
+
+    def test_invalid_cert_issuer_ext(self, backend):
+        crl = _load_cert(
+            os.path.join(
+                "x509", "custom", "crl_inval_cert_issuer_entry_ext.pem"
+            ),
+            x509.load_pem_x509_crl,
+            backend
+        )
+
+        with pytest.raises(ValueError):
+            crl[0].extensions
+
+    def test_indexing(self, backend):
+        crl = _load_cert(
+            os.path.join("x509", "custom", "crl_all_reasons.pem"),
+            x509.load_pem_x509_crl,
+            backend
+        )
+
+        with pytest.raises(IndexError):
+            crl[-13]
+        with pytest.raises(IndexError):
+            crl[12]
+
+        assert crl[-1].serial_number == crl[11].serial_number
+        assert len(crl[2:4]) == 2
+        assert crl[2:4][0].serial_number == crl[2].serial_number
+        assert crl[2:4][1].serial_number == crl[3].serial_number
+
+
+@pytest.mark.requires_backend_interface(interface=RSABackend)
+@pytest.mark.requires_backend_interface(interface=X509Backend)
+class TestRSACertificate(object):
+    def test_load_pem_cert(self, backend):
+        cert = _load_cert(
+            os.path.join("x509", "custom", "post2000utctime.pem"),
+            x509.load_pem_x509_certificate,
+            backend
+        )
+        assert isinstance(cert, x509.Certificate)
+        assert cert.serial_number == 11559813051657483483
+        fingerprint = binascii.hexlify(cert.fingerprint(hashes.SHA1()))
+        assert fingerprint == b"2b619ed04bfc9c3b08eb677d272192286a0947a8"
+        assert isinstance(cert.signature_hash_algorithm, hashes.SHA1)
+        assert (
+            cert.signature_algorithm_oid == SignatureAlgorithmOID.RSA_WITH_SHA1
+        )
+
+    def test_alternate_rsa_with_sha1_oid(self, backend):
+        cert = _load_cert(
+            os.path.join("x509", "alternate-rsa-sha1-oid.pem"),
+            x509.load_pem_x509_certificate,
+            backend
+        )
+        assert isinstance(cert.signature_hash_algorithm, hashes.SHA1)
+        assert (
+            cert.signature_algorithm_oid ==
+            SignatureAlgorithmOID._RSA_WITH_SHA1
+        )
+
+    def test_cert_serial_number(self, backend):
+        cert = _load_cert(
+            os.path.join("x509", "PKITS_data", "certs", "GoodCACert.crt"),
+            x509.load_der_x509_certificate,
+            backend
+        )
+
+        with pytest.deprecated_call():
+            assert cert.serial == 2
+            assert cert.serial_number == 2
+
+    def test_cert_serial_warning(self, backend):
+        cert = _load_cert(
+            os.path.join("x509", "PKITS_data", "certs", "GoodCACert.crt"),
+            x509.load_der_x509_certificate,
+            backend
+        )
+
+        with pytest.deprecated_call():
+            cert.serial
+
+    def test_load_der_cert(self, backend):
+        cert = _load_cert(
+            os.path.join("x509", "PKITS_data", "certs", "GoodCACert.crt"),
+            x509.load_der_x509_certificate,
+            backend
+        )
+        assert isinstance(cert, x509.Certificate)
+        assert cert.serial_number == 2
+        fingerprint = binascii.hexlify(cert.fingerprint(hashes.SHA1()))
+        assert fingerprint == b"6f49779533d565e8b7c1062503eab41492c38e4d"
+        assert isinstance(cert.signature_hash_algorithm, hashes.SHA256)
+
+    def test_signature(self, backend):
+        cert = _load_cert(
+            os.path.join("x509", "custom", "post2000utctime.pem"),
+            x509.load_pem_x509_certificate,
+            backend
+        )
+        assert cert.signature == binascii.unhexlify(
+            b"8e0f72fcbebe4755abcaf76c8ce0bae17cde4db16291638e1b1ce04a93cdb4c"
+            b"44a3486070986c5a880c14fdf8497e7d289b2630ccb21d24a3d1aa1b2d87482"
+            b"07f3a1e16ccdf8daa8a7ea1a33d49774f513edf09270bd8e665b6300a10f003"
+            b"66a59076905eb63cf10a81a0ca78a6ef3127f6cb2f6fb7f947fce22a30d8004"
+            b"8c243ba2c1a54c425fe12310e8a737638f4920354d4cce25cbd9dea25e6a2fe"
+            b"0d8579a5c8d929b9275be221975479f3f75075bcacf09526523b5fd67f7683f"
+            b"3cda420fabb1e9e6fc26bc0649cf61bb051d6932fac37066bb16f55903dfe78"
+            b"53dc5e505e2a10fbba4f9e93a0d3b53b7fa34b05d7ba6eef869bfc34b8e514f"
+            b"d5419f75"
+        )
+        assert len(cert.signature) == cert.public_key().key_size // 8
+
+    def test_tbs_certificate_bytes(self, backend):
+        cert = _load_cert(
+            os.path.join("x509", "custom", "post2000utctime.pem"),
+            x509.load_pem_x509_certificate,
+            backend
+        )
+        assert cert.tbs_certificate_bytes == binascii.unhexlify(
+            b"308202d8a003020102020900a06cb4b955f7f4db300d06092a864886f70d010"
+            b"10505003058310b3009060355040613024155311330110603550408130a536f"
+            b"6d652d53746174653121301f060355040a1318496e7465726e6574205769646"
+            b"769747320507479204c74643111300f0603550403130848656c6c6f20434130"
+            b"1e170d3134313132363231343132305a170d3134313232363231343132305a3"
+            b"058310b3009060355040613024155311330110603550408130a536f6d652d53"
+            b"746174653121301f060355040a1318496e7465726e657420576964676974732"
+            b"0507479204c74643111300f0603550403130848656c6c6f2043413082012230"
+            b"0d06092a864886f70d01010105000382010f003082010a0282010100b03af70"
+            b"2059e27f1e2284b56bbb26c039153bf81f295b73a49132990645ede4d2da0a9"
+            b"13c42e7d38d3589a00d3940d194f6e6d877c2ef812da22a275e83d8be786467"
+            b"48b4e7f23d10e873fd72f57a13dec732fc56ab138b1bb308399bb412cd73921"
+            b"4ef714e1976e09603405e2556299a05522510ac4574db5e9cb2cf5f99e8f48c"
+            b"1696ab3ea2d6d2ddab7d4e1b317188b76a572977f6ece0a4ad396f0150e7d8b"
+            b"1a9986c0cb90527ec26ca56e2914c270d2a198b632fa8a2fda55079d3d39864"
+            b"b6fb96ddbe331cacb3cb8783a8494ccccd886a3525078847ca01ca5f803e892"
+            b"14403e8a4b5499539c0b86f7a0daa45b204a8e079d8a5b03db7ba1ba3d7011a"
+            b"70203010001a381bc3081b9301d0603551d0e04160414d8e89dc777e4472656"
+            b"f1864695a9f66b7b0400ae3081890603551d23048181307f8014d8e89dc777e"
+            b"4472656f1864695a9f66b7b0400aea15ca45a3058310b300906035504061302"
+            b"4155311330110603550408130a536f6d652d53746174653121301f060355040"
+            b"a1318496e7465726e6574205769646769747320507479204c74643111300f06"
+            b"03550403130848656c6c6f204341820900a06cb4b955f7f4db300c0603551d1"
+            b"3040530030101ff"
+        )
+        verifier = cert.public_key().verifier(
+            cert.signature, padding.PKCS1v15(), cert.signature_hash_algorithm
+        )
+        verifier.update(cert.tbs_certificate_bytes)
+        verifier.verify()
+
+    def test_issuer(self, backend):
+        cert = _load_cert(
+            os.path.join(
+                "x509", "PKITS_data", "certs",
+                "Validpre2000UTCnotBeforeDateTest3EE.crt"
+            ),
+            x509.load_der_x509_certificate,
+            backend
+        )
+        issuer = cert.issuer
+        assert isinstance(issuer, x509.Name)
+        assert list(issuer) == [
+            x509.NameAttribute(NameOID.COUNTRY_NAME, u'US'),
+            x509.NameAttribute(
+                NameOID.ORGANIZATION_NAME, u'Test Certificates 2011'
+            ),
+            x509.NameAttribute(NameOID.COMMON_NAME, u'Good CA')
+        ]
+        assert issuer.get_attributes_for_oid(NameOID.COMMON_NAME) == [
+            x509.NameAttribute(NameOID.COMMON_NAME, u'Good CA')
+        ]
+
+    def test_all_issuer_name_types(self, backend):
+        cert = _load_cert(
+            os.path.join(
+                "x509", "custom",
+                "all_supported_names.pem"
+            ),
+            x509.load_pem_x509_certificate,
+            backend
+        )
+        issuer = cert.issuer
+
+        assert isinstance(issuer, x509.Name)
+        assert list(issuer) == [
+            x509.NameAttribute(NameOID.COUNTRY_NAME, u'US'),
+            x509.NameAttribute(NameOID.COUNTRY_NAME, u'CA'),
+            x509.NameAttribute(NameOID.STATE_OR_PROVINCE_NAME, u'Texas'),
+            x509.NameAttribute(NameOID.STATE_OR_PROVINCE_NAME, u'Illinois'),
+            x509.NameAttribute(NameOID.LOCALITY_NAME, u'Chicago'),
+            x509.NameAttribute(NameOID.LOCALITY_NAME, u'Austin'),
+            x509.NameAttribute(NameOID.ORGANIZATION_NAME, u'Zero, LLC'),
+            x509.NameAttribute(NameOID.ORGANIZATION_NAME, u'One, LLC'),
+            x509.NameAttribute(NameOID.COMMON_NAME, u'common name 0'),
+            x509.NameAttribute(NameOID.COMMON_NAME, u'common name 1'),
+            x509.NameAttribute(NameOID.ORGANIZATIONAL_UNIT_NAME, u'OU 0'),
+            x509.NameAttribute(NameOID.ORGANIZATIONAL_UNIT_NAME, u'OU 1'),
+            x509.NameAttribute(NameOID.DN_QUALIFIER, u'dnQualifier0'),
+            x509.NameAttribute(NameOID.DN_QUALIFIER, u'dnQualifier1'),
+            x509.NameAttribute(NameOID.SERIAL_NUMBER, u'123'),
+            x509.NameAttribute(NameOID.SERIAL_NUMBER, u'456'),
+            x509.NameAttribute(NameOID.TITLE, u'Title 0'),
+            x509.NameAttribute(NameOID.TITLE, u'Title 1'),
+            x509.NameAttribute(NameOID.SURNAME, u'Surname 0'),
+            x509.NameAttribute(NameOID.SURNAME, u'Surname 1'),
+            x509.NameAttribute(NameOID.GIVEN_NAME, u'Given Name 0'),
+            x509.NameAttribute(NameOID.GIVEN_NAME, u'Given Name 1'),
+            x509.NameAttribute(NameOID.PSEUDONYM, u'Incognito 0'),
+            x509.NameAttribute(NameOID.PSEUDONYM, u'Incognito 1'),
+            x509.NameAttribute(NameOID.GENERATION_QUALIFIER, u'Last Gen'),
+            x509.NameAttribute(NameOID.GENERATION_QUALIFIER, u'Next Gen'),
+            x509.NameAttribute(NameOID.DOMAIN_COMPONENT, u'dc0'),
+            x509.NameAttribute(NameOID.DOMAIN_COMPONENT, u'dc1'),
+            x509.NameAttribute(NameOID.EMAIL_ADDRESS, u'test0@test.local'),
+            x509.NameAttribute(NameOID.EMAIL_ADDRESS, u'test1@test.local'),
+        ]
+
+    def test_subject(self, backend):
+        cert = _load_cert(
+            os.path.join(
+                "x509", "PKITS_data", "certs",
+                "Validpre2000UTCnotBeforeDateTest3EE.crt"
+            ),
+            x509.load_der_x509_certificate,
+            backend
+        )
+        subject = cert.subject
+        assert isinstance(subject, x509.Name)
+        assert list(subject) == [
+            x509.NameAttribute(NameOID.COUNTRY_NAME, u'US'),
+            x509.NameAttribute(
+                NameOID.ORGANIZATION_NAME, u'Test Certificates 2011'
+            ),
+            x509.NameAttribute(
+                NameOID.COMMON_NAME,
+                u'Valid pre2000 UTC notBefore Date EE Certificate Test3'
+            )
+        ]
+        assert subject.get_attributes_for_oid(NameOID.COMMON_NAME) == [
+            x509.NameAttribute(
+                NameOID.COMMON_NAME,
+                u'Valid pre2000 UTC notBefore Date EE Certificate Test3'
+            )
+        ]
+
+    def test_unicode_name(self, backend):
+        cert = _load_cert(
+            os.path.join(
+                "x509", "custom",
+                "utf8_common_name.pem"
+            ),
+            x509.load_pem_x509_certificate,
+            backend
+        )
+        assert cert.subject.get_attributes_for_oid(NameOID.COMMON_NAME) == [
+            x509.NameAttribute(
+                NameOID.COMMON_NAME,
+                u'We heart UTF8!\u2122'
+            )
+        ]
+        assert cert.issuer.get_attributes_for_oid(NameOID.COMMON_NAME) == [
+            x509.NameAttribute(
+                NameOID.COMMON_NAME,
+                u'We heart UTF8!\u2122'
+            )
+        ]
+
+    def test_all_subject_name_types(self, backend):
+        cert = _load_cert(
+            os.path.join(
+                "x509", "custom",
+                "all_supported_names.pem"
+            ),
+            x509.load_pem_x509_certificate,
+            backend
+        )
+        subject = cert.subject
+        assert isinstance(subject, x509.Name)
+        assert list(subject) == [
+            x509.NameAttribute(NameOID.COUNTRY_NAME, u'AU'),
+            x509.NameAttribute(NameOID.COUNTRY_NAME, u'DE'),
+            x509.NameAttribute(NameOID.STATE_OR_PROVINCE_NAME, u'California'),
+            x509.NameAttribute(NameOID.STATE_OR_PROVINCE_NAME, u'New York'),
+            x509.NameAttribute(NameOID.LOCALITY_NAME, u'San Francisco'),
+            x509.NameAttribute(NameOID.LOCALITY_NAME, u'Ithaca'),
+            x509.NameAttribute(NameOID.ORGANIZATION_NAME, u'Org Zero, LLC'),
+            x509.NameAttribute(NameOID.ORGANIZATION_NAME, u'Org One, LLC'),
+            x509.NameAttribute(NameOID.COMMON_NAME, u'CN 0'),
+            x509.NameAttribute(NameOID.COMMON_NAME, u'CN 1'),
+            x509.NameAttribute(
+                NameOID.ORGANIZATIONAL_UNIT_NAME, u'Engineering 0'
+            ),
+            x509.NameAttribute(
+                NameOID.ORGANIZATIONAL_UNIT_NAME, u'Engineering 1'
+            ),
+            x509.NameAttribute(NameOID.DN_QUALIFIER, u'qualified0'),
+            x509.NameAttribute(NameOID.DN_QUALIFIER, u'qualified1'),
+            x509.NameAttribute(NameOID.SERIAL_NUMBER, u'789'),
+            x509.NameAttribute(NameOID.SERIAL_NUMBER, u'012'),
+            x509.NameAttribute(NameOID.TITLE, u'Title IX'),
+            x509.NameAttribute(NameOID.TITLE, u'Title X'),
+            x509.NameAttribute(NameOID.SURNAME, u'Last 0'),
+            x509.NameAttribute(NameOID.SURNAME, u'Last 1'),
+            x509.NameAttribute(NameOID.GIVEN_NAME, u'First 0'),
+            x509.NameAttribute(NameOID.GIVEN_NAME, u'First 1'),
+            x509.NameAttribute(NameOID.PSEUDONYM, u'Guy Incognito 0'),
+            x509.NameAttribute(NameOID.PSEUDONYM, u'Guy Incognito 1'),
+            x509.NameAttribute(NameOID.GENERATION_QUALIFIER, u'32X'),
+            x509.NameAttribute(NameOID.GENERATION_QUALIFIER, u'Dreamcast'),
+            x509.NameAttribute(NameOID.DOMAIN_COMPONENT, u'dc2'),
+            x509.NameAttribute(NameOID.DOMAIN_COMPONENT, u'dc3'),
+            x509.NameAttribute(NameOID.EMAIL_ADDRESS, u'test2@test.local'),
+            x509.NameAttribute(NameOID.EMAIL_ADDRESS, u'test3@test.local'),
+        ]
+
+    def test_load_good_ca_cert(self, backend):
+        cert = _load_cert(
+            os.path.join("x509", "PKITS_data", "certs", "GoodCACert.crt"),
+            x509.load_der_x509_certificate,
+            backend
+        )
+
+        assert cert.not_valid_before == datetime.datetime(2010, 1, 1, 8, 30)
+        assert cert.not_valid_after == datetime.datetime(2030, 12, 31, 8, 30)
+        assert cert.serial_number == 2
+        public_key = cert.public_key()
+        assert isinstance(public_key, rsa.RSAPublicKey)
+        assert cert.version is x509.Version.v3
+        fingerprint = binascii.hexlify(cert.fingerprint(hashes.SHA1()))
+        assert fingerprint == b"6f49779533d565e8b7c1062503eab41492c38e4d"
+
+    def test_utc_pre_2000_not_before_cert(self, backend):
+        cert = _load_cert(
+            os.path.join(
+                "x509", "PKITS_data", "certs",
+                "Validpre2000UTCnotBeforeDateTest3EE.crt"
+            ),
+            x509.load_der_x509_certificate,
+            backend
+        )
+
+        assert cert.not_valid_before == datetime.datetime(1950, 1, 1, 12, 1)
+
+    def test_pre_2000_utc_not_after_cert(self, backend):
+        cert = _load_cert(
+            os.path.join(
+                "x509", "PKITS_data", "certs",
+                "Invalidpre2000UTCEEnotAfterDateTest7EE.crt"
+            ),
+            x509.load_der_x509_certificate,
+            backend
+        )
+
+        assert cert.not_valid_after == datetime.datetime(1999, 1, 1, 12, 1)
+
+    def test_post_2000_utc_cert(self, backend):
+        cert = _load_cert(
+            os.path.join("x509", "custom", "post2000utctime.pem"),
+            x509.load_pem_x509_certificate,
+            backend
+        )
+        assert cert.not_valid_before == datetime.datetime(
+            2014, 11, 26, 21, 41, 20
+        )
+        assert cert.not_valid_after == datetime.datetime(
+            2014, 12, 26, 21, 41, 20
+        )
+
+    def test_generalized_time_not_before_cert(self, backend):
+        cert = _load_cert(
+            os.path.join(
+                "x509", "PKITS_data", "certs",
+                "ValidGeneralizedTimenotBeforeDateTest4EE.crt"
+            ),
+            x509.load_der_x509_certificate,
+            backend
+        )
+        assert cert.not_valid_before == datetime.datetime(2002, 1, 1, 12, 1)
+        assert cert.not_valid_after == datetime.datetime(2030, 12, 31, 8, 30)
+        assert cert.version is x509.Version.v3
+
+    def test_generalized_time_not_after_cert(self, backend):
+        cert = _load_cert(
+            os.path.join(
+                "x509", "PKITS_data", "certs",
+                "ValidGeneralizedTimenotAfterDateTest8EE.crt"
+            ),
+            x509.load_der_x509_certificate,
+            backend
+        )
+        assert cert.not_valid_before == datetime.datetime(2010, 1, 1, 8, 30)
+        assert cert.not_valid_after == datetime.datetime(2050, 1, 1, 12, 1)
+        assert cert.version is x509.Version.v3
+
+    def test_invalid_version_cert(self, backend):
+        cert = _load_cert(
+            os.path.join("x509", "custom", "invalid_version.pem"),
+            x509.load_pem_x509_certificate,
+            backend
+        )
+        with pytest.raises(x509.InvalidVersion) as exc:
+            cert.version
+
+        assert exc.value.parsed_version == 7
+
+    def test_eq(self, backend):
+        cert = _load_cert(
+            os.path.join("x509", "custom", "post2000utctime.pem"),
+            x509.load_pem_x509_certificate,
+            backend
+        )
+        cert2 = _load_cert(
+            os.path.join("x509", "custom", "post2000utctime.pem"),
+            x509.load_pem_x509_certificate,
+            backend
+        )
+        assert cert == cert2
+
+    def test_ne(self, backend):
+        cert = _load_cert(
+            os.path.join("x509", "custom", "post2000utctime.pem"),
+            x509.load_pem_x509_certificate,
+            backend
+        )
+        cert2 = _load_cert(
+            os.path.join(
+                "x509", "PKITS_data", "certs",
+                "ValidGeneralizedTimenotAfterDateTest8EE.crt"
+            ),
+            x509.load_der_x509_certificate,
+            backend
+        )
+        assert cert != cert2
+        assert cert != object()
+
+    def test_hash(self, backend):
+        cert1 = _load_cert(
+            os.path.join("x509", "custom", "post2000utctime.pem"),
+            x509.load_pem_x509_certificate,
+            backend
+        )
+        cert2 = _load_cert(
+            os.path.join("x509", "custom", "post2000utctime.pem"),
+            x509.load_pem_x509_certificate,
+            backend
+        )
+        cert3 = _load_cert(
+            os.path.join(
+                "x509", "PKITS_data", "certs",
+                "ValidGeneralizedTimenotAfterDateTest8EE.crt"
+            ),
+            x509.load_der_x509_certificate,
+            backend
+        )
+
+        assert hash(cert1) == hash(cert2)
+        assert hash(cert1) != hash(cert3)
+
+    def test_version_1_cert(self, backend):
+        cert = _load_cert(
+            os.path.join("x509", "v1_cert.pem"),
+            x509.load_pem_x509_certificate,
+            backend
+        )
+        assert cert.version is x509.Version.v1
+
+    def test_invalid_pem(self, backend):
+        with pytest.raises(ValueError):
+            x509.load_pem_x509_certificate(b"notacert", backend)
+
+    def test_invalid_der(self, backend):
+        with pytest.raises(ValueError):
+            x509.load_der_x509_certificate(b"notacert", backend)
+
+    def test_unsupported_signature_hash_algorithm_cert(self, backend):
+        cert = _load_cert(
+            os.path.join("x509", "verisign_md2_root.pem"),
+            x509.load_pem_x509_certificate,
+            backend
+        )
+        with pytest.raises(UnsupportedAlgorithm):
+            cert.signature_hash_algorithm
+
+    def test_public_bytes_pem(self, backend):
+        # Load an existing certificate.
+        cert = _load_cert(
+            os.path.join("x509", "PKITS_data", "certs", "GoodCACert.crt"),
+            x509.load_der_x509_certificate,
+            backend
+        )
+
+        # Encode it to PEM and load it back.
+        cert = x509.load_pem_x509_certificate(cert.public_bytes(
+            encoding=serialization.Encoding.PEM,
+        ), backend)
+
+        # We should recover what we had to start with.
+        assert cert.not_valid_before == datetime.datetime(2010, 1, 1, 8, 30)
+        assert cert.not_valid_after == datetime.datetime(2030, 12, 31, 8, 30)
+        assert cert.serial_number == 2
+        public_key = cert.public_key()
+        assert isinstance(public_key, rsa.RSAPublicKey)
+        assert cert.version is x509.Version.v3
+        fingerprint = binascii.hexlify(cert.fingerprint(hashes.SHA1()))
+        assert fingerprint == b"6f49779533d565e8b7c1062503eab41492c38e4d"
+
+    def test_public_bytes_der(self, backend):
+        # Load an existing certificate.
+        cert = _load_cert(
+            os.path.join("x509", "PKITS_data", "certs", "GoodCACert.crt"),
+            x509.load_der_x509_certificate,
+            backend
+        )
+
+        # Encode it to DER and load it back.
+        cert = x509.load_der_x509_certificate(cert.public_bytes(
+            encoding=serialization.Encoding.DER,
+        ), backend)
+
+        # We should recover what we had to start with.
+        assert cert.not_valid_before == datetime.datetime(2010, 1, 1, 8, 30)
+        assert cert.not_valid_after == datetime.datetime(2030, 12, 31, 8, 30)
+        assert cert.serial_number == 2
+        public_key = cert.public_key()
+        assert isinstance(public_key, rsa.RSAPublicKey)
+        assert cert.version is x509.Version.v3
+        fingerprint = binascii.hexlify(cert.fingerprint(hashes.SHA1()))
+        assert fingerprint == b"6f49779533d565e8b7c1062503eab41492c38e4d"
+
+    def test_public_bytes_invalid_encoding(self, backend):
+        cert = _load_cert(
+            os.path.join("x509", "PKITS_data", "certs", "GoodCACert.crt"),
+            x509.load_der_x509_certificate,
+            backend
+        )
+
+        with pytest.raises(TypeError):
+            cert.public_bytes('NotAnEncoding')
+
+    @pytest.mark.parametrize(
+        ("cert_path", "loader_func", "encoding"),
+        [
+            (
+                os.path.join("x509", "v1_cert.pem"),
+                x509.load_pem_x509_certificate,
+                serialization.Encoding.PEM,
+            ),
+            (
+                os.path.join("x509", "PKITS_data", "certs", "GoodCACert.crt"),
+                x509.load_der_x509_certificate,
+                serialization.Encoding.DER,
+            ),
+        ]
+    )
+    def test_public_bytes_match(self, cert_path, loader_func, encoding,
+                                backend):
+        cert_bytes = load_vectors_from_file(
+            cert_path, lambda pemfile: pemfile.read(), mode="rb"
+        )
+        cert = loader_func(cert_bytes, backend)
+        serialized = cert.public_bytes(encoding)
+        assert serialized == cert_bytes
+
+    def test_certificate_repr(self, backend):
+        cert = _load_cert(
+            os.path.join(
+                "x509", "cryptography.io.pem"
+            ),
+            x509.load_pem_x509_certificate,
+            backend
+        )
+        if six.PY3:
+            assert repr(cert) == (
+                "<Certificate(subject=<Name([<NameAttribute(oid=<ObjectIdentif"
+                "ier(oid=2.5.4.11, name=organizationalUnitName)>, value='GT487"
+                "42965')>, <NameAttribute(oid=<ObjectIdentifier(oid=2.5.4.11, "
+                "name=organizationalUnitName)>, value='See www.rapidssl.com/re"
+                "sources/cps (c)14')>, <NameAttribute(oid=<ObjectIdentifier(oi"
+                "d=2.5.4.11, name=organizationalUnitName)>, value='Domain Cont"
+                "rol Validated - RapidSSL(R)')>, <NameAttribute(oid=<ObjectIde"
+                "ntifier(oid=2.5.4.3, name=commonName)>, value='www.cryptograp"
+                "hy.io')>])>, ...)>"
+            )
+        else:
+            assert repr(cert) == (
+                "<Certificate(subject=<Name([<NameAttribute(oid=<ObjectIdentif"
+                "ier(oid=2.5.4.11, name=organizationalUnitName)>, value=u'GT48"
+                "742965')>, <NameAttribute(oid=<ObjectIdentifier(oid=2.5.4.11,"
+                " name=organizationalUnitName)>, value=u'See www.rapidssl.com/"
+                "resources/cps (c)14')>, <NameAttribute(oid=<ObjectIdentifier("
+                "oid=2.5.4.11, name=organizationalUnitName)>, value=u'Domain C"
+                "ontrol Validated - RapidSSL(R)')>, <NameAttribute(oid=<Object"
+                "Identifier(oid=2.5.4.3, name=commonName)>, value=u'www.crypto"
+                "graphy.io')>])>, ...)>"
+            )
+
+
+@pytest.mark.requires_backend_interface(interface=RSABackend)
+@pytest.mark.requires_backend_interface(interface=X509Backend)
+class TestRSACertificateRequest(object):
+    @pytest.mark.parametrize(
+        ("path", "loader_func"),
+        [
+            [
+                os.path.join("x509", "requests", "rsa_sha1.pem"),
+                x509.load_pem_x509_csr
+            ],
+            [
+                os.path.join("x509", "requests", "rsa_sha1.der"),
+                x509.load_der_x509_csr
+            ],
+        ]
+    )
+    def test_load_rsa_certificate_request(self, path, loader_func, backend):
+        request = _load_cert(path, loader_func, backend)
+        assert isinstance(request.signature_hash_algorithm, hashes.SHA1)
+        assert (
+            request.signature_algorithm_oid ==
+            SignatureAlgorithmOID.RSA_WITH_SHA1
+        )
+        public_key = request.public_key()
+        assert isinstance(public_key, rsa.RSAPublicKey)
+        subject = request.subject
+        assert isinstance(subject, x509.Name)
+        assert list(subject) == [
+            x509.NameAttribute(NameOID.COUNTRY_NAME, u'US'),
+            x509.NameAttribute(NameOID.STATE_OR_PROVINCE_NAME, u'Texas'),
+            x509.NameAttribute(NameOID.LOCALITY_NAME, u'Austin'),
+            x509.NameAttribute(NameOID.ORGANIZATION_NAME, u'PyCA'),
+            x509.NameAttribute(NameOID.COMMON_NAME, u'cryptography.io'),
+        ]
+        extensions = request.extensions
+        assert isinstance(extensions, x509.Extensions)
+        assert list(extensions) == []
+
+    @pytest.mark.parametrize(
+        "loader_func",
+        [x509.load_pem_x509_csr, x509.load_der_x509_csr]
+    )
+    def test_invalid_certificate_request(self, loader_func, backend):
+        with pytest.raises(ValueError):
+            loader_func(b"notacsr", backend)
+
+    def test_unsupported_signature_hash_algorithm_request(self, backend):
+        request = _load_cert(
+            os.path.join("x509", "requests", "rsa_md4.pem"),
+            x509.load_pem_x509_csr,
+            backend
+        )
+        with pytest.raises(UnsupportedAlgorithm):
+            request.signature_hash_algorithm
+
+    def test_duplicate_extension(self, backend):
+        request = _load_cert(
+            os.path.join(
+                "x509", "requests", "two_basic_constraints.pem"
+            ),
+            x509.load_pem_x509_csr,
+            backend
+        )
+        with pytest.raises(x509.DuplicateExtension) as exc:
+            request.extensions
+
+        assert exc.value.oid == ExtensionOID.BASIC_CONSTRAINTS
+
+    def test_unsupported_critical_extension(self, backend):
+        request = _load_cert(
+            os.path.join(
+                "x509", "requests", "unsupported_extension_critical.pem"
+            ),
+            x509.load_pem_x509_csr,
+            backend
+        )
+        ext = request.extensions.get_extension_for_oid(
+            x509.ObjectIdentifier('1.2.3.4')
+        )
+        assert ext.value.value == b"value"
+
+    def test_unsupported_extension(self, backend):
+        request = _load_cert(
+            os.path.join(
+                "x509", "requests", "unsupported_extension.pem"
+            ),
+            x509.load_pem_x509_csr,
+            backend
+        )
+        extensions = request.extensions
+        assert len(extensions) == 1
+        assert extensions[0].oid == x509.ObjectIdentifier("1.2.3.4")
+        assert extensions[0].value == x509.UnrecognizedExtension(
+            x509.ObjectIdentifier("1.2.3.4"), b"value"
+        )
+
+    def test_request_basic_constraints(self, backend):
+        request = _load_cert(
+            os.path.join(
+                "x509", "requests", "basic_constraints.pem"
+            ),
+            x509.load_pem_x509_csr,
+            backend
+        )
+        extensions = request.extensions
+        assert isinstance(extensions, x509.Extensions)
+        assert list(extensions) == [
+            x509.Extension(
+                ExtensionOID.BASIC_CONSTRAINTS,
+                True,
+                x509.BasicConstraints(ca=True, path_length=1),
+            ),
+        ]
+
+    def test_subject_alt_name(self, backend):
+        request = _load_cert(
+            os.path.join("x509", "requests", "san_rsa_sha1.pem"),
+            x509.load_pem_x509_csr,
+            backend,
+        )
+        ext = request.extensions.get_extension_for_oid(
+            ExtensionOID.SUBJECT_ALTERNATIVE_NAME
+        )
+        assert list(ext.value) == [
+            x509.DNSName(b"cryptography.io"),
+            x509.DNSName(b"sub.cryptography.io"),
+        ]
+
+    def test_public_bytes_pem(self, backend):
+        # Load an existing CSR.
+        request = _load_cert(
+            os.path.join("x509", "requests", "rsa_sha1.pem"),
+            x509.load_pem_x509_csr,
+            backend
+        )
+
+        # Encode it to PEM and load it back.
+        request = x509.load_pem_x509_csr(request.public_bytes(
+            encoding=serialization.Encoding.PEM,
+        ), backend)
+
+        # We should recover what we had to start with.
+        assert isinstance(request.signature_hash_algorithm, hashes.SHA1)
+        public_key = request.public_key()
+        assert isinstance(public_key, rsa.RSAPublicKey)
+        subject = request.subject
+        assert isinstance(subject, x509.Name)
+        assert list(subject) == [
+            x509.NameAttribute(NameOID.COUNTRY_NAME, u'US'),
+            x509.NameAttribute(NameOID.STATE_OR_PROVINCE_NAME, u'Texas'),
+            x509.NameAttribute(NameOID.LOCALITY_NAME, u'Austin'),
+            x509.NameAttribute(NameOID.ORGANIZATION_NAME, u'PyCA'),
+            x509.NameAttribute(NameOID.COMMON_NAME, u'cryptography.io'),
+        ]
+
+    def test_public_bytes_der(self, backend):
+        # Load an existing CSR.
+        request = _load_cert(
+            os.path.join("x509", "requests", "rsa_sha1.pem"),
+            x509.load_pem_x509_csr,
+            backend
+        )
+
+        # Encode it to DER and load it back.
+        request = x509.load_der_x509_csr(request.public_bytes(
+            encoding=serialization.Encoding.DER,
+        ), backend)
+
+        # We should recover what we had to start with.
+        assert isinstance(request.signature_hash_algorithm, hashes.SHA1)
+        public_key = request.public_key()
+        assert isinstance(public_key, rsa.RSAPublicKey)
+        subject = request.subject
+        assert isinstance(subject, x509.Name)
+        assert list(subject) == [
+            x509.NameAttribute(NameOID.COUNTRY_NAME, u'US'),
+            x509.NameAttribute(NameOID.STATE_OR_PROVINCE_NAME, u'Texas'),
+            x509.NameAttribute(NameOID.LOCALITY_NAME, u'Austin'),
+            x509.NameAttribute(NameOID.ORGANIZATION_NAME, u'PyCA'),
+            x509.NameAttribute(NameOID.COMMON_NAME, u'cryptography.io'),
+        ]
+
+    def test_signature(self, backend):
+        request = _load_cert(
+            os.path.join("x509", "requests", "rsa_sha1.pem"),
+            x509.load_pem_x509_csr,
+            backend
+        )
+        assert request.signature == binascii.unhexlify(
+            b"8364c86ffbbfe0bfc9a21f831256658ca8989741b80576d36f08a934603a43b1"
+            b"837246d00167a518abb1de7b51a1e5b7ebea14944800818b1a923c804f120a0d"
+            b"624f6310ef79e8612755c2b01dcc7f59dfdbce0db3f2630f185f504b8c17af80"
+            b"cbd364fa5fda68337153930948226cd4638287a0aed6524d3006885c19028a1e"
+            b"e2f5a91d6e77dbaa0b49996ee0a0c60b55b61bd080a08bb34aa7f3e07e91f37f"
+            b"6a11645be2d8654c1570dcda145ed7cc92017f7d53225d7f283f3459ec5bda41"
+            b"cf6dd75d43676c543483385226b7e4fa29c8739f1b0eaf199613593991979862"
+            b"e36181e8c4c270c354b7f52c128db1b70639823324c7ea24791b7bc3d7005f3b"
+        )
+
+    def test_tbs_certrequest_bytes(self, backend):
+        request = _load_cert(
+            os.path.join("x509", "requests", "rsa_sha1.pem"),
+            x509.load_pem_x509_csr,
+            backend
+        )
+        assert request.tbs_certrequest_bytes == binascii.unhexlify(
+            b"308201840201003057310b3009060355040613025553310e300c060355040813"
+            b"055465786173310f300d0603550407130641757374696e310d300b060355040a"
+            b"130450794341311830160603550403130f63727970746f6772617068792e696f"
+            b"30820122300d06092a864886f70d01010105000382010f003082010a02820101"
+            b"00a840a78460cb861066dfa3045a94ba6cf1b7ab9d24c761cffddcc2cb5e3f1d"
+            b"c3e4be253e7039ef14fe9d6d2304f50d9f2e1584c51530ab75086f357138bff7"
+            b"b854d067d1d5f384f1f2f2c39cc3b15415e2638554ef8402648ae3ef08336f22"
+            b"b7ecc6d4331c2b21c3091a7f7a9518180754a646640b60419e4cc6f5c798110a"
+            b"7f030a639fe87e33b4776dfcd993940ec776ab57a181ad8598857976dc303f9a"
+            b"573ca619ab3fe596328e92806b828683edc17cc256b41948a2bfa8d047d2158d"
+            b"3d8e069aa05fa85b3272abb1c4b4422b6366f3b70e642377b145cd6259e5d3e7"
+            b"db048d51921e50766a37b1b130ee6b11f507d20a834001e8de16a92c14f2e964"
+            b"a30203010001a000"
+        )
+        verifier = request.public_key().verifier(
+            request.signature,
+            padding.PKCS1v15(),
+            request.signature_hash_algorithm
+        )
+        verifier.update(request.tbs_certrequest_bytes)
+        verifier.verify()
+
+    def test_public_bytes_invalid_encoding(self, backend):
+        request = _load_cert(
+            os.path.join("x509", "requests", "rsa_sha1.pem"),
+            x509.load_pem_x509_csr,
+            backend
+        )
+
+        with pytest.raises(TypeError):
+            request.public_bytes('NotAnEncoding')
+
+    def test_signature_invalid(self, backend):
+        request = _load_cert(
+            os.path.join("x509", "requests", "invalid_signature.pem"),
+            x509.load_pem_x509_csr,
+            backend
+        )
+        assert not request.is_signature_valid
+
+    def test_signature_valid(self, backend):
+        request = _load_cert(
+            os.path.join("x509", "requests", "rsa_sha256.pem"),
+            x509.load_pem_x509_csr,
+            backend
+        )
+        assert request.is_signature_valid
+
+    @pytest.mark.parametrize(
+        ("request_path", "loader_func", "encoding"),
+        [
+            (
+                os.path.join("x509", "requests", "rsa_sha1.pem"),
+                x509.load_pem_x509_csr,
+                serialization.Encoding.PEM,
+            ),
+            (
+                os.path.join("x509", "requests", "rsa_sha1.der"),
+                x509.load_der_x509_csr,
+                serialization.Encoding.DER,
+            ),
+        ]
+    )
+    def test_public_bytes_match(self, request_path, loader_func, encoding,
+                                backend):
+        request_bytes = load_vectors_from_file(
+            request_path, lambda pemfile: pemfile.read(), mode="rb"
+        )
+        request = loader_func(request_bytes, backend)
+        serialized = request.public_bytes(encoding)
+        assert serialized == request_bytes
+
+    def test_eq(self, backend):
+        request1 = _load_cert(
+            os.path.join("x509", "requests", "rsa_sha1.pem"),
+            x509.load_pem_x509_csr,
+            backend
+        )
+        request2 = _load_cert(
+            os.path.join("x509", "requests", "rsa_sha1.pem"),
+            x509.load_pem_x509_csr,
+            backend
+        )
+
+        assert request1 == request2
+
+    def test_ne(self, backend):
+        request1 = _load_cert(
+            os.path.join("x509", "requests", "rsa_sha1.pem"),
+            x509.load_pem_x509_csr,
+            backend
+        )
+        request2 = _load_cert(
+            os.path.join("x509", "requests", "san_rsa_sha1.pem"),
+            x509.load_pem_x509_csr,
+            backend
+        )
+
+        assert request1 != request2
+        assert request1 != object()
+
+    def test_hash(self, backend):
+        request1 = _load_cert(
+            os.path.join("x509", "requests", "rsa_sha1.pem"),
+            x509.load_pem_x509_csr,
+            backend
+        )
+        request2 = _load_cert(
+            os.path.join("x509", "requests", "rsa_sha1.pem"),
+            x509.load_pem_x509_csr,
+            backend
+        )
+        request3 = _load_cert(
+            os.path.join("x509", "requests", "san_rsa_sha1.pem"),
+            x509.load_pem_x509_csr,
+            backend
+        )
+
+        assert hash(request1) == hash(request2)
+        assert hash(request1) != hash(request3)
+
+    def test_build_cert(self, backend):
+        issuer_private_key = RSA_KEY_2048.private_key(backend)
+        subject_private_key = RSA_KEY_2048.private_key(backend)
+
+        not_valid_before = datetime.datetime(2002, 1, 1, 12, 1)
+        not_valid_after = datetime.datetime(2030, 12, 31, 8, 30)
+
+        builder = x509.CertificateBuilder().serial_number(
+            777
+        ).issuer_name(x509.Name([
+            x509.NameAttribute(NameOID.COUNTRY_NAME, u'US'),
+            x509.NameAttribute(NameOID.STATE_OR_PROVINCE_NAME, u'Texas'),
+            x509.NameAttribute(NameOID.LOCALITY_NAME, u'Austin'),
+            x509.NameAttribute(NameOID.ORGANIZATION_NAME, u'PyCA'),
+            x509.NameAttribute(NameOID.COMMON_NAME, u'cryptography.io'),
+        ])).subject_name(x509.Name([
+            x509.NameAttribute(NameOID.COUNTRY_NAME, u'US'),
+            x509.NameAttribute(NameOID.STATE_OR_PROVINCE_NAME, u'Texas'),
+            x509.NameAttribute(NameOID.LOCALITY_NAME, u'Austin'),
+            x509.NameAttribute(NameOID.ORGANIZATION_NAME, u'PyCA'),
+            x509.NameAttribute(NameOID.COMMON_NAME, u'cryptography.io'),
+        ])).public_key(
+            subject_private_key.public_key()
+        ).add_extension(
+            x509.BasicConstraints(ca=False, path_length=None), True,
+        ).add_extension(
+            x509.SubjectAlternativeName([x509.DNSName(b"cryptography.io")]),
+            critical=False,
+        ).not_valid_before(
+            not_valid_before
+        ).not_valid_after(
+            not_valid_after
+        )
+
+        cert = builder.sign(issuer_private_key, hashes.SHA1(), backend)
+
+        assert cert.version is x509.Version.v3
+        assert cert.not_valid_before == not_valid_before
+        assert cert.not_valid_after == not_valid_after
+        basic_constraints = cert.extensions.get_extension_for_oid(
+            ExtensionOID.BASIC_CONSTRAINTS
+        )
+        assert basic_constraints.value.ca is False
+        assert basic_constraints.value.path_length is None
+        subject_alternative_name = cert.extensions.get_extension_for_oid(
+            ExtensionOID.SUBJECT_ALTERNATIVE_NAME
+        )
+        assert list(subject_alternative_name.value) == [
+            x509.DNSName(b"cryptography.io"),
+        ]
+
+    def test_build_cert_printable_string_country_name(self, backend):
+        issuer_private_key = RSA_KEY_2048.private_key(backend)
+        subject_private_key = RSA_KEY_2048.private_key(backend)
+
+        not_valid_before = datetime.datetime(2002, 1, 1, 12, 1)
+        not_valid_after = datetime.datetime(2030, 12, 31, 8, 30)
+
+        builder = x509.CertificateBuilder().serial_number(
+            777
+        ).issuer_name(x509.Name([
+            x509.NameAttribute(NameOID.COUNTRY_NAME, u'US'),
+            x509.NameAttribute(NameOID.JURISDICTION_COUNTRY_NAME, u'US'),
+            x509.NameAttribute(NameOID.STATE_OR_PROVINCE_NAME, u'Texas'),
+        ])).subject_name(x509.Name([
+            x509.NameAttribute(NameOID.COUNTRY_NAME, u'US'),
+            x509.NameAttribute(NameOID.JURISDICTION_COUNTRY_NAME, u'US'),
+            x509.NameAttribute(NameOID.STATE_OR_PROVINCE_NAME, u'Texas'),
+        ])).public_key(
+            subject_private_key.public_key()
+        ).not_valid_before(
+            not_valid_before
+        ).not_valid_after(
+            not_valid_after
+        )
+
+        cert = builder.sign(issuer_private_key, hashes.SHA256(), backend)
+
+        parsed = Certificate.load(
+            cert.public_bytes(serialization.Encoding.DER))
+
+        # Check that each value was encoded as an ASN.1 PRINTABLESTRING.
+        assert parsed.subject.chosen[0][0]['value'].chosen.tag == 19
+        assert parsed.issuer.chosen[0][0]['value'].chosen.tag == 19
+        if (
+            # This only works correctly in OpenSSL 1.1.0f+ and 1.0.2l+
+            backend._lib.CRYPTOGRAPHY_OPENSSL_110F_OR_GREATER or (
+                backend._lib.CRYPTOGRAPHY_OPENSSL_102L_OR_GREATER and
+                not backend._lib.CRYPTOGRAPHY_OPENSSL_110_OR_GREATER
+            )
+        ):
+            assert parsed.subject.chosen[1][0]['value'].chosen.tag == 19
+            assert parsed.issuer.chosen[1][0]['value'].chosen.tag == 19
+
+
+class TestCertificateBuilder(object):
+    @pytest.mark.requires_backend_interface(interface=RSABackend)
+    @pytest.mark.requires_backend_interface(interface=X509Backend)
+    def test_checks_for_unsupported_extensions(self, backend):
+        private_key = RSA_KEY_2048.private_key(backend)
+        builder = x509.CertificateBuilder().subject_name(x509.Name([
+            x509.NameAttribute(NameOID.COUNTRY_NAME, u'US'),
+        ])).issuer_name(x509.Name([
+            x509.NameAttribute(NameOID.COUNTRY_NAME, u'US'),
+        ])).public_key(
+            private_key.public_key()
+        ).serial_number(
+            777
+        ).not_valid_before(
+            datetime.datetime(1999, 1, 1)
+        ).not_valid_after(
+            datetime.datetime(2020, 1, 1)
+        ).add_extension(
+            DummyExtension(), False
+        )
+
+        with pytest.raises(NotImplementedError):
+            builder.sign(private_key, hashes.SHA1(), backend)
+
+    @pytest.mark.requires_backend_interface(interface=RSABackend)
+    @pytest.mark.requires_backend_interface(interface=X509Backend)
+    def test_encode_nonstandard_aia(self, backend):
+        private_key = RSA_KEY_2048.private_key(backend)
+
+        aia = x509.AuthorityInformationAccess([
+            x509.AccessDescription(
+                x509.ObjectIdentifier("2.999.7"),
+                x509.UniformResourceIdentifier(b"http://example.com")
+            ),
+        ])
+
+        builder = x509.CertificateBuilder().subject_name(x509.Name([
+            x509.NameAttribute(NameOID.COUNTRY_NAME, u'US'),
+        ])).issuer_name(x509.Name([
+            x509.NameAttribute(NameOID.COUNTRY_NAME, u'US'),
+        ])).public_key(
+            private_key.public_key()
+        ).serial_number(
+            777
+        ).not_valid_before(
+            datetime.datetime(1999, 1, 1)
+        ).not_valid_after(
+            datetime.datetime(2020, 1, 1)
+        ).add_extension(
+            aia, False
+        )
+
+        builder.sign(private_key, hashes.SHA256(), backend)
+
+    @pytest.mark.skipif(sys.platform != "win32", reason="Requires windows")
+    @pytest.mark.parametrize(
+        ("not_valid_before", "not_valid_after"),
+        [
+            [datetime.datetime(1999, 1, 1), datetime.datetime(9999, 1, 1)],
+            [datetime.datetime(9999, 1, 1), datetime.datetime(9999, 12, 31)],
+        ]
+    )
+    @pytest.mark.requires_backend_interface(interface=RSABackend)
+    @pytest.mark.requires_backend_interface(interface=X509Backend)
+    def test_invalid_time_windows(self, not_valid_before, not_valid_after,
+                                  backend):
+        private_key = RSA_KEY_2048.private_key(backend)
+        builder = x509.CertificateBuilder().subject_name(x509.Name([
+            x509.NameAttribute(NameOID.COUNTRY_NAME, u'US'),
+        ])).issuer_name(x509.Name([
+            x509.NameAttribute(NameOID.COUNTRY_NAME, u'US'),
+        ])).public_key(
+            private_key.public_key()
+        ).serial_number(
+            777
+        ).not_valid_before(
+            not_valid_before
+        ).not_valid_after(
+            not_valid_after
+        )
+        with pytest.raises(ValueError):
+            builder.sign(private_key, hashes.SHA256(), backend)
+
+    @pytest.mark.requires_backend_interface(interface=RSABackend)
+    @pytest.mark.requires_backend_interface(interface=X509Backend)
+    def test_no_subject_name(self, backend):
+        subject_private_key = RSA_KEY_2048.private_key(backend)
+        builder = x509.CertificateBuilder().serial_number(
+            777
+        ).issuer_name(x509.Name([
+            x509.NameAttribute(NameOID.COUNTRY_NAME, u'US'),
+        ])).public_key(
+            subject_private_key.public_key()
+        ).not_valid_before(
+            datetime.datetime(2002, 1, 1, 12, 1)
+        ).not_valid_after(
+            datetime.datetime(2030, 12, 31, 8, 30)
+        )
+        with pytest.raises(ValueError):
+            builder.sign(subject_private_key, hashes.SHA256(), backend)
+
+    @pytest.mark.requires_backend_interface(interface=RSABackend)
+    @pytest.mark.requires_backend_interface(interface=X509Backend)
+    def test_no_issuer_name(self, backend):
+        subject_private_key = RSA_KEY_2048.private_key(backend)
+        builder = x509.CertificateBuilder().serial_number(
+            777
+        ).subject_name(x509.Name([
+            x509.NameAttribute(NameOID.COUNTRY_NAME, u'US'),
+        ])).public_key(
+            subject_private_key.public_key()
+        ).not_valid_before(
+            datetime.datetime(2002, 1, 1, 12, 1)
+        ).not_valid_after(
+            datetime.datetime(2030, 12, 31, 8, 30)
+        )
+        with pytest.raises(ValueError):
+            builder.sign(subject_private_key, hashes.SHA256(), backend)
+
+    @pytest.mark.requires_backend_interface(interface=RSABackend)
+    @pytest.mark.requires_backend_interface(interface=X509Backend)
+    def test_no_public_key(self, backend):
+        subject_private_key = RSA_KEY_2048.private_key(backend)
+        builder = x509.CertificateBuilder().serial_number(
+            777
+        ).issuer_name(x509.Name([
+            x509.NameAttribute(NameOID.COUNTRY_NAME, u'US'),
+        ])).subject_name(x509.Name([
+            x509.NameAttribute(NameOID.COUNTRY_NAME, u'US'),
+        ])).not_valid_before(
+            datetime.datetime(2002, 1, 1, 12, 1)
+        ).not_valid_after(
+            datetime.datetime(2030, 12, 31, 8, 30)
+        )
+        with pytest.raises(ValueError):
+            builder.sign(subject_private_key, hashes.SHA256(), backend)
+
+    @pytest.mark.requires_backend_interface(interface=RSABackend)
+    @pytest.mark.requires_backend_interface(interface=X509Backend)
+    def test_no_not_valid_before(self, backend):
+        subject_private_key = RSA_KEY_2048.private_key(backend)
+        builder = x509.CertificateBuilder().serial_number(
+            777
+        ).issuer_name(x509.Name([
+            x509.NameAttribute(NameOID.COUNTRY_NAME, u'US'),
+        ])).subject_name(x509.Name([
+            x509.NameAttribute(NameOID.COUNTRY_NAME, u'US'),
+        ])).public_key(
+            subject_private_key.public_key()
+        ).not_valid_after(
+            datetime.datetime(2030, 12, 31, 8, 30)
+        )
+        with pytest.raises(ValueError):
+            builder.sign(subject_private_key, hashes.SHA256(), backend)
+
+    @pytest.mark.requires_backend_interface(interface=RSABackend)
+    @pytest.mark.requires_backend_interface(interface=X509Backend)
+    def test_no_not_valid_after(self, backend):
+        subject_private_key = RSA_KEY_2048.private_key(backend)
+        builder = x509.CertificateBuilder().serial_number(
+            777
+        ).issuer_name(x509.Name([
+            x509.NameAttribute(NameOID.COUNTRY_NAME, u'US'),
+        ])).subject_name(x509.Name([
+            x509.NameAttribute(NameOID.COUNTRY_NAME, u'US'),
+        ])).public_key(
+            subject_private_key.public_key()
+        ).not_valid_before(
+            datetime.datetime(2002, 1, 1, 12, 1)
+        )
+        with pytest.raises(ValueError):
+            builder.sign(subject_private_key, hashes.SHA256(), backend)
+
+    @pytest.mark.requires_backend_interface(interface=RSABackend)
+    @pytest.mark.requires_backend_interface(interface=X509Backend)
+    def test_no_serial_number(self, backend):
+        subject_private_key = RSA_KEY_2048.private_key(backend)
+        builder = x509.CertificateBuilder().issuer_name(x509.Name([
+            x509.NameAttribute(NameOID.COUNTRY_NAME, u'US'),
+        ])).subject_name(x509.Name([
+            x509.NameAttribute(NameOID.COUNTRY_NAME, u'US'),
+        ])).public_key(
+            subject_private_key.public_key()
+        ).not_valid_before(
+            datetime.datetime(2002, 1, 1, 12, 1)
+        ).not_valid_after(
+            datetime.datetime(2030, 12, 31, 8, 30)
+        )
+        with pytest.raises(ValueError):
+            builder.sign(subject_private_key, hashes.SHA256(), backend)
+
+    def test_issuer_name_must_be_a_name_type(self):
+        builder = x509.CertificateBuilder()
+
+        with pytest.raises(TypeError):
+            builder.issuer_name("subject")
+
+        with pytest.raises(TypeError):
+            builder.issuer_name(object)
+
+    def test_issuer_name_may_only_be_set_once(self):
+        name = x509.Name([
+            x509.NameAttribute(NameOID.COUNTRY_NAME, u'US'),
+        ])
+        builder = x509.CertificateBuilder().issuer_name(name)
+
+        with pytest.raises(ValueError):
+            builder.issuer_name(name)
+
+    def test_subject_name_must_be_a_name_type(self):
+        builder = x509.CertificateBuilder()
+
+        with pytest.raises(TypeError):
+            builder.subject_name("subject")
+
+        with pytest.raises(TypeError):
+            builder.subject_name(object)
+
+    def test_subject_name_may_only_be_set_once(self):
+        name = x509.Name([
+            x509.NameAttribute(NameOID.COUNTRY_NAME, u'US'),
+        ])
+        builder = x509.CertificateBuilder().subject_name(name)
+
+        with pytest.raises(ValueError):
+            builder.subject_name(name)
+
+    def test_not_valid_before_after_not_valid_after(self):
+        builder = x509.CertificateBuilder()
+
+        builder = builder.not_valid_after(
+            datetime.datetime(2002, 1, 1, 12, 1)
+        )
+        with pytest.raises(ValueError):
+            builder.not_valid_before(
+                datetime.datetime(2003, 1, 1, 12, 1)
+            )
+
+    def test_not_valid_after_before_not_valid_before(self):
+        builder = x509.CertificateBuilder()
+
+        builder = builder.not_valid_before(
+            datetime.datetime(2002, 1, 1, 12, 1)
+        )
+        with pytest.raises(ValueError):
+            builder.not_valid_after(
+                datetime.datetime(2001, 1, 1, 12, 1)
+            )
+
+    @pytest.mark.requires_backend_interface(interface=RSABackend)
+    @pytest.mark.requires_backend_interface(interface=X509Backend)
+    def test_public_key_must_be_public_key(self, backend):
+        private_key = RSA_KEY_2048.private_key(backend)
+        builder = x509.CertificateBuilder()
+
+        with pytest.raises(TypeError):
+            builder.public_key(private_key)
+
+    @pytest.mark.requires_backend_interface(interface=RSABackend)
+    @pytest.mark.requires_backend_interface(interface=X509Backend)
+    def test_public_key_may_only_be_set_once(self, backend):
+        private_key = RSA_KEY_2048.private_key(backend)
+        public_key = private_key.public_key()
+        builder = x509.CertificateBuilder().public_key(public_key)
+
+        with pytest.raises(ValueError):
+            builder.public_key(public_key)
+
+    def test_serial_number_must_be_an_integer_type(self):
+        with pytest.raises(TypeError):
+            x509.CertificateBuilder().serial_number(10.0)
+
+    def test_serial_number_must_be_non_negative(self):
+        with pytest.raises(ValueError):
+            x509.CertificateBuilder().serial_number(-1)
+
+    def test_serial_number_must_be_positive(self):
+        with pytest.raises(ValueError):
+            x509.CertificateBuilder().serial_number(0)
+
+    @pytest.mark.requires_backend_interface(interface=RSABackend)
+    @pytest.mark.requires_backend_interface(interface=X509Backend)
+    def test_minimal_serial_number(self, backend):
+        subject_private_key = RSA_KEY_2048.private_key(backend)
+        builder = x509.CertificateBuilder().serial_number(
+            1
+        ).subject_name(x509.Name([
+            x509.NameAttribute(NameOID.COUNTRY_NAME, u'RU'),
+        ])).issuer_name(x509.Name([
+            x509.NameAttribute(NameOID.COUNTRY_NAME, u'RU'),
+        ])).public_key(
+            subject_private_key.public_key()
+        ).not_valid_before(
+            datetime.datetime(2002, 1, 1, 12, 1)
+        ).not_valid_after(
+            datetime.datetime(2030, 12, 31, 8, 30)
+        )
+        cert = builder.sign(subject_private_key, hashes.SHA256(), backend)
+        assert cert.serial_number == 1
+
+    @pytest.mark.requires_backend_interface(interface=RSABackend)
+    @pytest.mark.requires_backend_interface(interface=X509Backend)
+    def test_biggest_serial_number(self, backend):
+        subject_private_key = RSA_KEY_2048.private_key(backend)
+        builder = x509.CertificateBuilder().serial_number(
+            (1 << 159) - 1
+        ).subject_name(x509.Name([
+            x509.NameAttribute(NameOID.COUNTRY_NAME, u'RU'),
+        ])).issuer_name(x509.Name([
+            x509.NameAttribute(NameOID.COUNTRY_NAME, u'RU'),
+        ])).public_key(
+            subject_private_key.public_key()
+        ).not_valid_before(
+            datetime.datetime(2002, 1, 1, 12, 1)
+        ).not_valid_after(
+            datetime.datetime(2030, 12, 31, 8, 30)
+        )
+        cert = builder.sign(subject_private_key, hashes.SHA256(), backend)
+        assert cert.serial_number == (1 << 159) - 1
+
+    def test_serial_number_must_be_less_than_160_bits_long(self):
+        with pytest.raises(ValueError):
+            x509.CertificateBuilder().serial_number(1 << 159)
+
+    def test_serial_number_may_only_be_set_once(self):
+        builder = x509.CertificateBuilder().serial_number(10)
+
+        with pytest.raises(ValueError):
+            builder.serial_number(20)
+
+    @pytest.mark.requires_backend_interface(interface=RSABackend)
+    @pytest.mark.requires_backend_interface(interface=X509Backend)
+    def test_aware_not_valid_after(self, backend):
+        time = datetime.datetime(2012, 1, 16, 22, 43)
+        tz = pytz.timezone("US/Pacific")
+        time = tz.localize(time)
+        utc_time = datetime.datetime(2012, 1, 17, 6, 43)
+        private_key = RSA_KEY_2048.private_key(backend)
+        cert_builder = x509.CertificateBuilder().not_valid_after(time)
+        cert_builder = cert_builder.subject_name(
+            x509.Name([x509.NameAttribute(NameOID.COUNTRY_NAME, u'US')])
+        ).issuer_name(
+            x509.Name([x509.NameAttribute(NameOID.COUNTRY_NAME, u'US')])
+        ).serial_number(
+            1
+        ).public_key(
+            private_key.public_key()
+        ).not_valid_before(
+            utc_time - datetime.timedelta(days=365)
+        )
+
+        cert = cert_builder.sign(private_key, hashes.SHA256(), backend)
+        assert cert.not_valid_after == utc_time
+
+    def test_invalid_not_valid_after(self):
+        with pytest.raises(TypeError):
+            x509.CertificateBuilder().not_valid_after(104204304504)
+
+        with pytest.raises(TypeError):
+            x509.CertificateBuilder().not_valid_after(datetime.time())
+
+        with pytest.raises(ValueError):
+            x509.CertificateBuilder().not_valid_after(
+                datetime.datetime(1960, 8, 10)
+            )
+
+    def test_not_valid_after_may_only_be_set_once(self):
+        builder = x509.CertificateBuilder().not_valid_after(
+            datetime.datetime.now()
+        )
+
+        with pytest.raises(ValueError):
+            builder.not_valid_after(
+                datetime.datetime.now()
+            )
+
+    @pytest.mark.requires_backend_interface(interface=RSABackend)
+    @pytest.mark.requires_backend_interface(interface=X509Backend)
+    def test_aware_not_valid_before(self, backend):
+        time = datetime.datetime(2012, 1, 16, 22, 43)
+        tz = pytz.timezone("US/Pacific")
+        time = tz.localize(time)
+        utc_time = datetime.datetime(2012, 1, 17, 6, 43)
+        private_key = RSA_KEY_2048.private_key(backend)
+        cert_builder = x509.CertificateBuilder().not_valid_before(time)
+        cert_builder = cert_builder.subject_name(
+            x509.Name([x509.NameAttribute(NameOID.COUNTRY_NAME, u'US')])
+        ).issuer_name(
+            x509.Name([x509.NameAttribute(NameOID.COUNTRY_NAME, u'US')])
+        ).serial_number(
+            1
+        ).public_key(
+            private_key.public_key()
+        ).not_valid_after(
+            utc_time + datetime.timedelta(days=366)
+        )
+
+        cert = cert_builder.sign(private_key, hashes.SHA256(), backend)
+        assert cert.not_valid_before == utc_time
+
+    def test_invalid_not_valid_before(self):
+        with pytest.raises(TypeError):
+            x509.CertificateBuilder().not_valid_before(104204304504)
+
+        with pytest.raises(TypeError):
+            x509.CertificateBuilder().not_valid_before(datetime.time())
+
+        with pytest.raises(ValueError):
+            x509.CertificateBuilder().not_valid_before(
+                datetime.datetime(1960, 8, 10)
+            )
+
+    def test_not_valid_before_may_only_be_set_once(self):
+        builder = x509.CertificateBuilder().not_valid_before(
+            datetime.datetime.now()
+        )
+
+        with pytest.raises(ValueError):
+            builder.not_valid_before(
+                datetime.datetime.now()
+            )
+
+    def test_add_extension_checks_for_duplicates(self):
+        builder = x509.CertificateBuilder().add_extension(
+            x509.BasicConstraints(ca=False, path_length=None), True,
+        )
+
+        with pytest.raises(ValueError):
+            builder.add_extension(
+                x509.BasicConstraints(ca=False, path_length=None), True,
+            )
+
+    def test_add_invalid_extension_type(self):
+        builder = x509.CertificateBuilder()
+
+        with pytest.raises(TypeError):
+            builder.add_extension(object(), False)
+
+    @pytest.mark.requires_backend_interface(interface=RSABackend)
+    @pytest.mark.requires_backend_interface(interface=X509Backend)
+    def test_sign_with_unsupported_hash(self, backend):
+        private_key = RSA_KEY_2048.private_key(backend)
+        builder = x509.CertificateBuilder()
+        builder = builder.subject_name(
+            x509.Name([x509.NameAttribute(NameOID.COUNTRY_NAME, u'US')])
+        ).issuer_name(
+            x509.Name([x509.NameAttribute(NameOID.COUNTRY_NAME, u'US')])
+        ).serial_number(
+            1
+        ).public_key(
+            private_key.public_key()
+        ).not_valid_before(
+            datetime.datetime(2002, 1, 1, 12, 1)
+        ).not_valid_after(
+            datetime.datetime(2032, 1, 1, 12, 1)
+        )
+
+        with pytest.raises(TypeError):
+            builder.sign(private_key, object(), backend)
+
+    @pytest.mark.requires_backend_interface(interface=RSABackend)
+    @pytest.mark.requires_backend_interface(interface=X509Backend)
+    def test_sign_rsa_with_md5(self, backend):
+        private_key = RSA_KEY_2048.private_key(backend)
+        builder = x509.CertificateBuilder()
+        builder = builder.subject_name(
+            x509.Name([x509.NameAttribute(NameOID.COUNTRY_NAME, u'US')])
+        ).issuer_name(
+            x509.Name([x509.NameAttribute(NameOID.COUNTRY_NAME, u'US')])
+        ).serial_number(
+            1
+        ).public_key(
+            private_key.public_key()
+        ).not_valid_before(
+            datetime.datetime(2002, 1, 1, 12, 1)
+        ).not_valid_after(
+            datetime.datetime(2032, 1, 1, 12, 1)
+        )
+        cert = builder.sign(private_key, hashes.MD5(), backend)
+        assert isinstance(cert.signature_hash_algorithm, hashes.MD5)
+
+    @pytest.mark.requires_backend_interface(interface=DSABackend)
+    @pytest.mark.requires_backend_interface(interface=X509Backend)
+    def test_sign_dsa_with_md5(self, backend):
+        private_key = DSA_KEY_2048.private_key(backend)
+        builder = x509.CertificateBuilder()
+        builder = builder.subject_name(
+            x509.Name([x509.NameAttribute(NameOID.COUNTRY_NAME, u'US')])
+        ).issuer_name(
+            x509.Name([x509.NameAttribute(NameOID.COUNTRY_NAME, u'US')])
+        ).serial_number(
+            1
+        ).public_key(
+            private_key.public_key()
+        ).not_valid_before(
+            datetime.datetime(2002, 1, 1, 12, 1)
+        ).not_valid_after(
+            datetime.datetime(2032, 1, 1, 12, 1)
+        )
+        with pytest.raises(ValueError):
+            builder.sign(private_key, hashes.MD5(), backend)
+
+    @pytest.mark.requires_backend_interface(interface=EllipticCurveBackend)
+    @pytest.mark.requires_backend_interface(interface=X509Backend)
+    def test_sign_ec_with_md5(self, backend):
+        _skip_curve_unsupported(backend, ec.SECP256R1())
+        private_key = EC_KEY_SECP256R1.private_key(backend)
+        builder = x509.CertificateBuilder()
+        builder = builder.subject_name(
+            x509.Name([x509.NameAttribute(NameOID.COUNTRY_NAME, u'US')])
+        ).issuer_name(
+            x509.Name([x509.NameAttribute(NameOID.COUNTRY_NAME, u'US')])
+        ).serial_number(
+            1
+        ).public_key(
+            private_key.public_key()
+        ).not_valid_before(
+            datetime.datetime(2002, 1, 1, 12, 1)
+        ).not_valid_after(
+            datetime.datetime(2032, 1, 1, 12, 1)
+        )
+        with pytest.raises(ValueError):
+            builder.sign(private_key, hashes.MD5(), backend)
+
+    @pytest.mark.parametrize(
+        "cdp",
+        [
+            x509.CRLDistributionPoints([
+                x509.DistributionPoint(
+                    full_name=None,
+                    relative_name=x509.RelativeDistinguishedName([
+                        x509.NameAttribute(
+                            NameOID.COMMON_NAME,
+                            u"indirect CRL for indirectCRL CA3"
+                        ),
+                    ]),
+                    reasons=None,
+                    crl_issuer=[x509.DirectoryName(
+                        x509.Name([
+                            x509.NameAttribute(NameOID.COUNTRY_NAME, u"US"),
+                            x509.NameAttribute(
+                                NameOID.ORGANIZATION_NAME,
+                                u"Test Certificates 2011"
+                            ),
+                            x509.NameAttribute(
+                                NameOID.ORGANIZATIONAL_UNIT_NAME,
+                                u"indirectCRL CA3 cRLIssuer"
+                            ),
+                        ])
+                    )],
+                )
+            ]),
+            x509.CRLDistributionPoints([
+                x509.DistributionPoint(
+                    full_name=[x509.DirectoryName(
+                        x509.Name([
+                            x509.NameAttribute(NameOID.COUNTRY_NAME, u"US"),
+                        ])
+                    )],
+                    relative_name=None,
+                    reasons=None,
+                    crl_issuer=[x509.DirectoryName(
+                        x509.Name([
+                            x509.NameAttribute(
+                                NameOID.ORGANIZATION_NAME,
+                                u"cryptography Testing"
+                            ),
+                        ])
+                    )],
+                )
+            ]),
+            x509.CRLDistributionPoints([
+                x509.DistributionPoint(
+                    full_name=[
+                        x509.UniformResourceIdentifier(
+                            u"http://myhost.com/myca.crl"
+                        ),
+                        x509.UniformResourceIdentifier(
+                            u"http://backup.myhost.com/myca.crl"
+                        )
+                    ],
+                    relative_name=None,
+                    reasons=frozenset([
+                        x509.ReasonFlags.key_compromise,
+                        x509.ReasonFlags.ca_compromise
+                    ]),
+                    crl_issuer=[x509.DirectoryName(
+                        x509.Name([
+                            x509.NameAttribute(NameOID.COUNTRY_NAME, u"US"),
+                            x509.NameAttribute(
+                                NameOID.COMMON_NAME, u"cryptography CA"
+                            ),
+                        ])
+                    )],
+                )
+            ]),
+            x509.CRLDistributionPoints([
+                x509.DistributionPoint(
+                    full_name=[x509.UniformResourceIdentifier(
+                        u"http://domain.com/some.crl"
+                    )],
+                    relative_name=None,
+                    reasons=frozenset([
+                        x509.ReasonFlags.key_compromise,
+                        x509.ReasonFlags.ca_compromise,
+                        x509.ReasonFlags.affiliation_changed,
+                        x509.ReasonFlags.superseded,
+                        x509.ReasonFlags.privilege_withdrawn,
+                        x509.ReasonFlags.cessation_of_operation,
+                        x509.ReasonFlags.aa_compromise,
+                        x509.ReasonFlags.certificate_hold,
+                    ]),
+                    crl_issuer=None
+                )
+            ]),
+            x509.CRLDistributionPoints([
+                x509.DistributionPoint(
+                    full_name=None,
+                    relative_name=None,
+                    reasons=None,
+                    crl_issuer=[x509.DirectoryName(
+                        x509.Name([
+                            x509.NameAttribute(
+                                NameOID.COMMON_NAME, u"cryptography CA"
+                            ),
+                        ])
+                    )],
+                )
+            ]),
+            x509.CRLDistributionPoints([
+                x509.DistributionPoint(
+                    full_name=[x509.UniformResourceIdentifier(
+                        u"http://domain.com/some.crl"
+                    )],
+                    relative_name=None,
+                    reasons=frozenset([x509.ReasonFlags.aa_compromise]),
+                    crl_issuer=None
+                )
+            ])
+        ]
+    )
+    @pytest.mark.requires_backend_interface(interface=RSABackend)
+    @pytest.mark.requires_backend_interface(interface=X509Backend)
+    def test_crl_distribution_points(self, backend, cdp):
+        issuer_private_key = RSA_KEY_2048.private_key(backend)
+        subject_private_key = RSA_KEY_2048.private_key(backend)
+
+        builder = x509.CertificateBuilder().serial_number(
+            4444444
+        ).issuer_name(x509.Name([
+            x509.NameAttribute(NameOID.LOCALITY_NAME, u'Austin'),
+        ])).subject_name(x509.Name([
+            x509.NameAttribute(NameOID.LOCALITY_NAME, u'Austin'),
+        ])).public_key(
+            subject_private_key.public_key()
+        ).add_extension(
+            cdp,
+            critical=False,
+        ).not_valid_before(
+            datetime.datetime(2002, 1, 1, 12, 1)
+        ).not_valid_after(
+            datetime.datetime(2030, 12, 31, 8, 30)
+        )
+
+        cert = builder.sign(issuer_private_key, hashes.SHA1(), backend)
+
+        ext = cert.extensions.get_extension_for_oid(
+            ExtensionOID.CRL_DISTRIBUTION_POINTS
+        )
+        assert ext.critical is False
+        assert ext.value == cdp
+
+    @pytest.mark.requires_backend_interface(interface=DSABackend)
+    @pytest.mark.requires_backend_interface(interface=X509Backend)
+    def test_build_cert_with_dsa_private_key(self, backend):
+        issuer_private_key = DSA_KEY_2048.private_key(backend)
+        subject_private_key = DSA_KEY_2048.private_key(backend)
+
+        not_valid_before = datetime.datetime(2002, 1, 1, 12, 1)
+        not_valid_after = datetime.datetime(2030, 12, 31, 8, 30)
+
+        builder = x509.CertificateBuilder().serial_number(
+            777
+        ).issuer_name(x509.Name([
+            x509.NameAttribute(NameOID.COUNTRY_NAME, u'US'),
+        ])).subject_name(x509.Name([
+            x509.NameAttribute(NameOID.COUNTRY_NAME, u'US'),
+        ])).public_key(
+            subject_private_key.public_key()
+        ).add_extension(
+            x509.BasicConstraints(ca=False, path_length=None), True,
+        ).add_extension(
+            x509.SubjectAlternativeName([x509.DNSName(b"cryptography.io")]),
+            critical=False,
+        ).not_valid_before(
+            not_valid_before
+        ).not_valid_after(
+            not_valid_after
+        )
+
+        cert = builder.sign(issuer_private_key, hashes.SHA1(), backend)
+
+        assert cert.version is x509.Version.v3
+        assert cert.not_valid_before == not_valid_before
+        assert cert.not_valid_after == not_valid_after
+        basic_constraints = cert.extensions.get_extension_for_oid(
+            ExtensionOID.BASIC_CONSTRAINTS
+        )
+        assert basic_constraints.value.ca is False
+        assert basic_constraints.value.path_length is None
+        subject_alternative_name = cert.extensions.get_extension_for_oid(
+            ExtensionOID.SUBJECT_ALTERNATIVE_NAME
+        )
+        assert list(subject_alternative_name.value) == [
+            x509.DNSName(b"cryptography.io"),
+        ]
+
+    @pytest.mark.requires_backend_interface(interface=EllipticCurveBackend)
+    @pytest.mark.requires_backend_interface(interface=X509Backend)
+    def test_build_cert_with_ec_private_key(self, backend):
+        _skip_curve_unsupported(backend, ec.SECP256R1())
+        issuer_private_key = ec.generate_private_key(ec.SECP256R1(), backend)
+        subject_private_key = ec.generate_private_key(ec.SECP256R1(), backend)
+
+        not_valid_before = datetime.datetime(2002, 1, 1, 12, 1)
+        not_valid_after = datetime.datetime(2030, 12, 31, 8, 30)
+
+        builder = x509.CertificateBuilder().serial_number(
+            777
+        ).issuer_name(x509.Name([
+            x509.NameAttribute(NameOID.COUNTRY_NAME, u'US'),
+        ])).subject_name(x509.Name([
+            x509.NameAttribute(NameOID.COUNTRY_NAME, u'US'),
+        ])).public_key(
+            subject_private_key.public_key()
+        ).add_extension(
+            x509.BasicConstraints(ca=False, path_length=None), True,
+        ).add_extension(
+            x509.SubjectAlternativeName([x509.DNSName(b"cryptography.io")]),
+            critical=False,
+        ).not_valid_before(
+            not_valid_before
+        ).not_valid_after(
+            not_valid_after
+        )
+
+        cert = builder.sign(issuer_private_key, hashes.SHA1(), backend)
+
+        assert cert.version is x509.Version.v3
+        assert cert.not_valid_before == not_valid_before
+        assert cert.not_valid_after == not_valid_after
+        basic_constraints = cert.extensions.get_extension_for_oid(
+            ExtensionOID.BASIC_CONSTRAINTS
+        )
+        assert basic_constraints.value.ca is False
+        assert basic_constraints.value.path_length is None
+        subject_alternative_name = cert.extensions.get_extension_for_oid(
+            ExtensionOID.SUBJECT_ALTERNATIVE_NAME
+        )
+        assert list(subject_alternative_name.value) == [
+            x509.DNSName(b"cryptography.io"),
+        ]
+
+    @pytest.mark.requires_backend_interface(interface=RSABackend)
+    @pytest.mark.requires_backend_interface(interface=X509Backend)
+    def test_build_cert_with_rsa_key_too_small(self, backend):
+        issuer_private_key = RSA_KEY_512.private_key(backend)
+        subject_private_key = RSA_KEY_512.private_key(backend)
+
+        not_valid_before = datetime.datetime(2002, 1, 1, 12, 1)
+        not_valid_after = datetime.datetime(2030, 12, 31, 8, 30)
+
+        builder = x509.CertificateBuilder().serial_number(
+            777
+        ).issuer_name(x509.Name([
+            x509.NameAttribute(NameOID.COUNTRY_NAME, u'US'),
+        ])).subject_name(x509.Name([
+            x509.NameAttribute(NameOID.COUNTRY_NAME, u'US'),
+        ])).public_key(
+            subject_private_key.public_key()
+        ).not_valid_before(
+            not_valid_before
+        ).not_valid_after(
+            not_valid_after
+        )
+
+        with pytest.raises(ValueError):
+            builder.sign(issuer_private_key, hashes.SHA512(), backend)
+
+    @pytest.mark.parametrize(
+        "cp",
+        [
+            x509.CertificatePolicies([
+                x509.PolicyInformation(
+                    x509.ObjectIdentifier("2.16.840.1.12345.1.2.3.4.1"),
+                    [u"http://other.com/cps"]
+                )
+            ]),
+            x509.CertificatePolicies([
+                x509.PolicyInformation(
+                    x509.ObjectIdentifier("2.16.840.1.12345.1.2.3.4.1"),
+                    None
+                )
+            ]),
+            x509.CertificatePolicies([
+                x509.PolicyInformation(
+                    x509.ObjectIdentifier("2.16.840.1.12345.1.2.3.4.1"),
+                    [
+                        u"http://example.com/cps",
+                        u"http://other.com/cps",
+                        x509.UserNotice(
+                            x509.NoticeReference(u"my org", [1, 2, 3, 4]),
+                            u"thing"
+                        )
+                    ]
+                )
+            ]),
+            x509.CertificatePolicies([
+                x509.PolicyInformation(
+                    x509.ObjectIdentifier("2.16.840.1.12345.1.2.3.4.1"),
+                    [
+                        u"http://example.com/cps",
+                        x509.UserNotice(
+                            x509.NoticeReference(u"UTF8\u2122'", [1, 2, 3, 4]),
+                            u"We heart UTF8!\u2122"
+                        )
+                    ]
+                )
+            ]),
+            x509.CertificatePolicies([
+                x509.PolicyInformation(
+                    x509.ObjectIdentifier("2.16.840.1.12345.1.2.3.4.1"),
+                    [x509.UserNotice(None, u"thing")]
+                )
+            ]),
+            x509.CertificatePolicies([
+                x509.PolicyInformation(
+                    x509.ObjectIdentifier("2.16.840.1.12345.1.2.3.4.1"),
+                    [
+                        x509.UserNotice(
+                            x509.NoticeReference(u"my org", [1, 2, 3, 4]),
+                            None
+                        )
+                    ]
+                )
+            ])
+        ]
+    )
+    @pytest.mark.requires_backend_interface(interface=RSABackend)
+    @pytest.mark.requires_backend_interface(interface=X509Backend)
+    def test_certificate_policies(self, cp, backend):
+        issuer_private_key = RSA_KEY_2048.private_key(backend)
+        subject_private_key = RSA_KEY_2048.private_key(backend)
+
+        not_valid_before = datetime.datetime(2002, 1, 1, 12, 1)
+        not_valid_after = datetime.datetime(2030, 12, 31, 8, 30)
+
+        cert = x509.CertificateBuilder().subject_name(
+            x509.Name([x509.NameAttribute(x509.OID_COUNTRY_NAME, u'US')])
+        ).issuer_name(
+            x509.Name([x509.NameAttribute(x509.OID_COUNTRY_NAME, u'US')])
+        ).not_valid_before(
+            not_valid_before
+        ).not_valid_after(
+            not_valid_after
+        ).public_key(
+            subject_private_key.public_key()
+        ).serial_number(
+            123
+        ).add_extension(
+            cp, critical=False
+        ).sign(issuer_private_key, hashes.SHA256(), backend)
+
+        ext = cert.extensions.get_extension_for_oid(
+            x509.OID_CERTIFICATE_POLICIES
+        )
+        assert ext.value == cp
+
+    @pytest.mark.requires_backend_interface(interface=RSABackend)
+    @pytest.mark.requires_backend_interface(interface=X509Backend)
+    def test_issuer_alt_name(self, backend):
+        issuer_private_key = RSA_KEY_2048.private_key(backend)
+        subject_private_key = RSA_KEY_2048.private_key(backend)
+
+        not_valid_before = datetime.datetime(2002, 1, 1, 12, 1)
+        not_valid_after = datetime.datetime(2030, 12, 31, 8, 30)
+
+        cert = x509.CertificateBuilder().subject_name(
+            x509.Name([x509.NameAttribute(NameOID.COUNTRY_NAME, u'US')])
+        ).issuer_name(
+            x509.Name([x509.NameAttribute(NameOID.COUNTRY_NAME, u'US')])
+        ).not_valid_before(
+            not_valid_before
+        ).not_valid_after(
+            not_valid_after
+        ).public_key(
+            subject_private_key.public_key()
+        ).serial_number(
+            123
+        ).add_extension(
+            x509.IssuerAlternativeName([
+                x509.DNSName(b"myissuer"),
+                x509.RFC822Name(u"email@domain.com"),
+            ]), critical=False
+        ).sign(issuer_private_key, hashes.SHA256(), backend)
+
+        ext = cert.extensions.get_extension_for_oid(
+            ExtensionOID.ISSUER_ALTERNATIVE_NAME
+        )
+        assert ext.critical is False
+        assert ext.value == x509.IssuerAlternativeName([
+            x509.DNSName(b"myissuer"),
+            x509.RFC822Name(u"email@domain.com"),
+        ])
+
+    @pytest.mark.requires_backend_interface(interface=RSABackend)
+    @pytest.mark.requires_backend_interface(interface=X509Backend)
+    def test_extended_key_usage(self, backend):
+        issuer_private_key = RSA_KEY_2048.private_key(backend)
+        subject_private_key = RSA_KEY_2048.private_key(backend)
+
+        not_valid_before = datetime.datetime(2002, 1, 1, 12, 1)
+        not_valid_after = datetime.datetime(2030, 12, 31, 8, 30)
+
+        cert = x509.CertificateBuilder().subject_name(
+            x509.Name([x509.NameAttribute(NameOID.COUNTRY_NAME, u'US')])
+        ).issuer_name(
+            x509.Name([x509.NameAttribute(NameOID.COUNTRY_NAME, u'US')])
+        ).not_valid_before(
+            not_valid_before
+        ).not_valid_after(
+            not_valid_after
+        ).public_key(
+            subject_private_key.public_key()
+        ).serial_number(
+            123
+        ).add_extension(
+            x509.ExtendedKeyUsage([
+                ExtendedKeyUsageOID.CLIENT_AUTH,
+                ExtendedKeyUsageOID.SERVER_AUTH,
+                ExtendedKeyUsageOID.CODE_SIGNING,
+            ]), critical=False
+        ).sign(issuer_private_key, hashes.SHA256(), backend)
+
+        eku = cert.extensions.get_extension_for_oid(
+            ExtensionOID.EXTENDED_KEY_USAGE
+        )
+        assert eku.critical is False
+        assert eku.value == x509.ExtendedKeyUsage([
+            ExtendedKeyUsageOID.CLIENT_AUTH,
+            ExtendedKeyUsageOID.SERVER_AUTH,
+            ExtendedKeyUsageOID.CODE_SIGNING,
+        ])
+
+    @pytest.mark.requires_backend_interface(interface=RSABackend)
+    @pytest.mark.requires_backend_interface(interface=X509Backend)
+    def test_inhibit_any_policy(self, backend):
+        issuer_private_key = RSA_KEY_2048.private_key(backend)
+        subject_private_key = RSA_KEY_2048.private_key(backend)
+
+        not_valid_before = datetime.datetime(2002, 1, 1, 12, 1)
+        not_valid_after = datetime.datetime(2030, 12, 31, 8, 30)
+
+        cert = x509.CertificateBuilder().subject_name(
+            x509.Name([x509.NameAttribute(NameOID.COUNTRY_NAME, u'US')])
+        ).issuer_name(
+            x509.Name([x509.NameAttribute(NameOID.COUNTRY_NAME, u'US')])
+        ).not_valid_before(
+            not_valid_before
+        ).not_valid_after(
+            not_valid_after
+        ).public_key(
+            subject_private_key.public_key()
+        ).serial_number(
+            123
+        ).add_extension(
+            x509.InhibitAnyPolicy(3), critical=False
+        ).sign(issuer_private_key, hashes.SHA256(), backend)
+
+        ext = cert.extensions.get_extension_for_oid(
+            ExtensionOID.INHIBIT_ANY_POLICY
+        )
+        assert ext.value == x509.InhibitAnyPolicy(3)
+
+    @pytest.mark.parametrize(
+        "pc",
+        [
+            x509.PolicyConstraints(
+                require_explicit_policy=None,
+                inhibit_policy_mapping=1
+            ),
+            x509.PolicyConstraints(
+                require_explicit_policy=3,
+                inhibit_policy_mapping=1
+            ),
+            x509.PolicyConstraints(
+                require_explicit_policy=0,
+                inhibit_policy_mapping=None
+            ),
+        ]
+    )
+    @pytest.mark.requires_backend_interface(interface=RSABackend)
+    @pytest.mark.requires_backend_interface(interface=X509Backend)
+    def test_policy_constraints(self, backend, pc):
+        issuer_private_key = RSA_KEY_2048.private_key(backend)
+        subject_private_key = RSA_KEY_2048.private_key(backend)
+
+        not_valid_before = datetime.datetime(2002, 1, 1, 12, 1)
+        not_valid_after = datetime.datetime(2030, 12, 31, 8, 30)
+
+        cert = x509.CertificateBuilder().subject_name(
+            x509.Name([x509.NameAttribute(NameOID.COUNTRY_NAME, u'US')])
+        ).issuer_name(
+            x509.Name([x509.NameAttribute(NameOID.COUNTRY_NAME, u'US')])
+        ).not_valid_before(
+            not_valid_before
+        ).not_valid_after(
+            not_valid_after
+        ).public_key(
+            subject_private_key.public_key()
+        ).serial_number(
+            123
+        ).add_extension(
+            pc, critical=False
+        ).sign(issuer_private_key, hashes.SHA256(), backend)
+
+        ext = cert.extensions.get_extension_for_class(
+            x509.PolicyConstraints
+        )
+        assert ext.critical is False
+        assert ext.value == pc
+
+    @pytest.mark.requires_backend_interface(interface=RSABackend)
+    @pytest.mark.requires_backend_interface(interface=X509Backend)
+    @pytest.mark.parametrize(
+        "nc",
+        [
+            x509.NameConstraints(
+                permitted_subtrees=[
+                    x509.IPAddress(ipaddress.IPv4Network(u"192.168.0.0/24")),
+                    x509.IPAddress(ipaddress.IPv4Network(u"192.168.0.0/29")),
+                    x509.IPAddress(ipaddress.IPv4Network(u"127.0.0.1/32")),
+                    x509.IPAddress(ipaddress.IPv4Network(u"8.0.0.0/8")),
+                    x509.IPAddress(ipaddress.IPv4Network(u"0.0.0.0/0")),
+                    x509.IPAddress(
+                        ipaddress.IPv6Network(u"FF:0:0:0:0:0:0:0/96")
+                    ),
+                    x509.IPAddress(
+                        ipaddress.IPv6Network(u"FF:FF:0:0:0:0:0:0/128")
+                    ),
+                ],
+                excluded_subtrees=[x509.DNSName(b"name.local")]
+            ),
+            x509.NameConstraints(
+                permitted_subtrees=[
+                    x509.IPAddress(ipaddress.IPv4Network(u"0.0.0.0/0")),
+                ],
+                excluded_subtrees=None
+            ),
+            x509.NameConstraints(
+                permitted_subtrees=None,
+                excluded_subtrees=[x509.DNSName(b"name.local")]
+            ),
+        ]
+    )
+    def test_name_constraints(self, nc, backend):
+        issuer_private_key = RSA_KEY_2048.private_key(backend)
+        subject_private_key = RSA_KEY_2048.private_key(backend)
+
+        not_valid_before = datetime.datetime(2002, 1, 1, 12, 1)
+        not_valid_after = datetime.datetime(2030, 12, 31, 8, 30)
+
+        cert = x509.CertificateBuilder().subject_name(
+            x509.Name([x509.NameAttribute(NameOID.COUNTRY_NAME, u'US')])
+        ).issuer_name(
+            x509.Name([x509.NameAttribute(NameOID.COUNTRY_NAME, u'US')])
+        ).not_valid_before(
+            not_valid_before
+        ).not_valid_after(
+            not_valid_after
+        ).public_key(
+            subject_private_key.public_key()
+        ).serial_number(
+            123
+        ).add_extension(
+            nc, critical=False
+        ).sign(issuer_private_key, hashes.SHA256(), backend)
+
+        ext = cert.extensions.get_extension_for_oid(
+            ExtensionOID.NAME_CONSTRAINTS
+        )
+        assert ext.value == nc
+
+    @pytest.mark.requires_backend_interface(interface=RSABackend)
+    @pytest.mark.requires_backend_interface(interface=X509Backend)
+    def test_key_usage(self, backend):
+        issuer_private_key = RSA_KEY_2048.private_key(backend)
+        subject_private_key = RSA_KEY_2048.private_key(backend)
+
+        not_valid_before = datetime.datetime(2002, 1, 1, 12, 1)
+        not_valid_after = datetime.datetime(2030, 12, 31, 8, 30)
+
+        cert = x509.CertificateBuilder().subject_name(
+            x509.Name([x509.NameAttribute(NameOID.COUNTRY_NAME, u'US')])
+        ).issuer_name(
+            x509.Name([x509.NameAttribute(NameOID.COUNTRY_NAME, u'US')])
+        ).not_valid_before(
+            not_valid_before
+        ).not_valid_after(
+            not_valid_after
+        ).public_key(
+            subject_private_key.public_key()
+        ).serial_number(
+            123
+        ).add_extension(
+            x509.KeyUsage(
+                digital_signature=True,
+                content_commitment=True,
+                key_encipherment=False,
+                data_encipherment=False,
+                key_agreement=False,
+                key_cert_sign=True,
+                crl_sign=False,
+                encipher_only=False,
+                decipher_only=False
+            ),
+            critical=False
+        ).sign(issuer_private_key, hashes.SHA256(), backend)
+
+        ext = cert.extensions.get_extension_for_oid(ExtensionOID.KEY_USAGE)
+        assert ext.critical is False
+        assert ext.value == x509.KeyUsage(
+            digital_signature=True,
+            content_commitment=True,
+            key_encipherment=False,
+            data_encipherment=False,
+            key_agreement=False,
+            key_cert_sign=True,
+            crl_sign=False,
+            encipher_only=False,
+            decipher_only=False
+        )
+
+    @pytest.mark.requires_backend_interface(interface=RSABackend)
+    @pytest.mark.requires_backend_interface(interface=X509Backend)
+    def test_build_ca_request_with_path_length_none(self, backend):
+        private_key = RSA_KEY_2048.private_key(backend)
+
+        request = x509.CertificateSigningRequestBuilder().subject_name(
+            x509.Name([
+                x509.NameAttribute(NameOID.ORGANIZATION_NAME,
+                                   u'PyCA'),
+            ])
+        ).add_extension(
+            x509.BasicConstraints(ca=True, path_length=None), critical=True
+        ).sign(private_key, hashes.SHA1(), backend)
+
+        loaded_request = x509.load_pem_x509_csr(
+            request.public_bytes(encoding=serialization.Encoding.PEM), backend
+        )
+        subject = loaded_request.subject
+        assert isinstance(subject, x509.Name)
+        basic_constraints = request.extensions.get_extension_for_oid(
+            ExtensionOID.BASIC_CONSTRAINTS
+        )
+        assert basic_constraints.value.path_length is None
+
+    @pytest.mark.parametrize(
+        "unrecognized", [
+            x509.UnrecognizedExtension(
+                x509.ObjectIdentifier("1.2.3.4.5"),
+                b"abcdef",
+            )
+        ]
+    )
+    @pytest.mark.requires_backend_interface(interface=RSABackend)
+    @pytest.mark.requires_backend_interface(interface=X509Backend)
+    def test_unrecognized_extension(self, backend, unrecognized):
+        private_key = RSA_KEY_2048.private_key(backend)
+
+        cert = x509.CertificateBuilder().subject_name(
+            x509.Name([x509.NameAttribute(x509.OID_COUNTRY_NAME, u'US')])
+        ).issuer_name(
+            x509.Name([x509.NameAttribute(x509.OID_COUNTRY_NAME, u'US')])
+        ).not_valid_before(
+            datetime.datetime(2002, 1, 1, 12, 1)
+        ).not_valid_after(
+            datetime.datetime(2030, 12, 31, 8, 30)
+        ).public_key(
+            private_key.public_key()
+        ).serial_number(
+            123
+        ).add_extension(
+            unrecognized, critical=False
+        ).sign(private_key, hashes.SHA256(), backend)
+
+        ext = cert.extensions.get_extension_for_oid(unrecognized.oid)
+
+        assert ext.value == unrecognized
+
+
+@pytest.mark.requires_backend_interface(interface=X509Backend)
+class TestCertificateSigningRequestBuilder(object):
+    @pytest.mark.requires_backend_interface(interface=RSABackend)
+    def test_sign_invalid_hash_algorithm(self, backend):
+        private_key = RSA_KEY_2048.private_key(backend)
+
+        builder = x509.CertificateSigningRequestBuilder().subject_name(
+            x509.Name([])
+        )
+        with pytest.raises(TypeError):
+            builder.sign(private_key, 'NotAHash', backend)
+
+    @pytest.mark.requires_backend_interface(interface=RSABackend)
+    def test_sign_rsa_with_md5(self, backend):
+        private_key = RSA_KEY_2048.private_key(backend)
+
+        builder = x509.CertificateSigningRequestBuilder().subject_name(
+            x509.Name([
+                x509.NameAttribute(NameOID.ORGANIZATION_NAME, u'PyCA'),
+            ])
+        )
+        request = builder.sign(private_key, hashes.MD5(), backend)
+        assert isinstance(request.signature_hash_algorithm, hashes.MD5)
+
+    @pytest.mark.requires_backend_interface(interface=DSABackend)
+    def test_sign_dsa_with_md5(self, backend):
+        private_key = DSA_KEY_2048.private_key(backend)
+        builder = x509.CertificateSigningRequestBuilder().subject_name(
+            x509.Name([
+                x509.NameAttribute(NameOID.ORGANIZATION_NAME, u'PyCA'),
+            ])
+        )
+        with pytest.raises(ValueError):
+            builder.sign(private_key, hashes.MD5(), backend)
+
+    @pytest.mark.requires_backend_interface(interface=EllipticCurveBackend)
+    def test_sign_ec_with_md5(self, backend):
+        _skip_curve_unsupported(backend, ec.SECP256R1())
+        private_key = EC_KEY_SECP256R1.private_key(backend)
+        builder = x509.CertificateSigningRequestBuilder().subject_name(
+            x509.Name([
+                x509.NameAttribute(NameOID.ORGANIZATION_NAME, u'PyCA'),
+            ])
+        )
+        with pytest.raises(ValueError):
+            builder.sign(private_key, hashes.MD5(), backend)
+
+    @pytest.mark.requires_backend_interface(interface=RSABackend)
+    def test_no_subject_name(self, backend):
+        private_key = RSA_KEY_2048.private_key(backend)
+
+        builder = x509.CertificateSigningRequestBuilder()
+        with pytest.raises(ValueError):
+            builder.sign(private_key, hashes.SHA256(), backend)
+
+    @pytest.mark.requires_backend_interface(interface=RSABackend)
+    def test_build_ca_request_with_rsa(self, backend):
+        private_key = RSA_KEY_2048.private_key(backend)
+
+        request = x509.CertificateSigningRequestBuilder().subject_name(
+            x509.Name([
+                x509.NameAttribute(NameOID.ORGANIZATION_NAME, u'PyCA'),
+            ])
+        ).add_extension(
+            x509.BasicConstraints(ca=True, path_length=2), critical=True
+        ).sign(private_key, hashes.SHA1(), backend)
+
+        assert isinstance(request.signature_hash_algorithm, hashes.SHA1)
+        public_key = request.public_key()
+        assert isinstance(public_key, rsa.RSAPublicKey)
+        subject = request.subject
+        assert isinstance(subject, x509.Name)
+        assert list(subject) == [
+            x509.NameAttribute(NameOID.ORGANIZATION_NAME, u'PyCA'),
+        ]
+        basic_constraints = request.extensions.get_extension_for_oid(
+            ExtensionOID.BASIC_CONSTRAINTS
+        )
+        assert basic_constraints.value.ca is True
+        assert basic_constraints.value.path_length == 2
+
+    @pytest.mark.requires_backend_interface(interface=RSABackend)
+    def test_build_ca_request_with_unicode(self, backend):
+        private_key = RSA_KEY_2048.private_key(backend)
+
+        request = x509.CertificateSigningRequestBuilder().subject_name(
+            x509.Name([
+                x509.NameAttribute(NameOID.ORGANIZATION_NAME,
+                                   u'PyCA\U0001f37a'),
+            ])
+        ).add_extension(
+            x509.BasicConstraints(ca=True, path_length=2), critical=True
+        ).sign(private_key, hashes.SHA1(), backend)
+
+        loaded_request = x509.load_pem_x509_csr(
+            request.public_bytes(encoding=serialization.Encoding.PEM), backend
+        )
+        subject = loaded_request.subject
+        assert isinstance(subject, x509.Name)
+        assert list(subject) == [
+            x509.NameAttribute(NameOID.ORGANIZATION_NAME, u'PyCA\U0001f37a'),
+        ]
+
+    @pytest.mark.requires_backend_interface(interface=RSABackend)
+    def test_build_ca_request_with_multivalue_rdns(self, backend):
+        private_key = RSA_KEY_2048.private_key(backend)
+        subject = x509.Name([
+            x509.RelativeDistinguishedName([
+                x509.NameAttribute(NameOID.TITLE, u'Test'),
+                x509.NameAttribute(NameOID.COMMON_NAME, u'Multivalue'),
+                x509.NameAttribute(NameOID.SURNAME, u'RDNs'),
+            ]),
+            x509.RelativeDistinguishedName([
+                x509.NameAttribute(NameOID.ORGANIZATION_NAME, u'PyCA')
+            ]),
+        ])
+
+        request = x509.CertificateSigningRequestBuilder().subject_name(
+            subject
+        ).sign(private_key, hashes.SHA1(), backend)
+
+        loaded_request = x509.load_pem_x509_csr(
+            request.public_bytes(encoding=serialization.Encoding.PEM), backend
+        )
+        assert isinstance(loaded_request.subject, x509.Name)
+        assert loaded_request.subject == subject
+
+    @pytest.mark.requires_backend_interface(interface=RSABackend)
+    def test_build_nonca_request_with_rsa(self, backend):
+        private_key = RSA_KEY_2048.private_key(backend)
+
+        request = x509.CertificateSigningRequestBuilder().subject_name(
+            x509.Name([
+                x509.NameAttribute(NameOID.COUNTRY_NAME, u'US'),
+            ])
+        ).add_extension(
+            x509.BasicConstraints(ca=False, path_length=None), critical=True,
+        ).sign(private_key, hashes.SHA1(), backend)
+
+        assert isinstance(request.signature_hash_algorithm, hashes.SHA1)
+        public_key = request.public_key()
+        assert isinstance(public_key, rsa.RSAPublicKey)
+        subject = request.subject
+        assert isinstance(subject, x509.Name)
+        assert list(subject) == [
+            x509.NameAttribute(NameOID.COUNTRY_NAME, u'US'),
+        ]
+        basic_constraints = request.extensions.get_extension_for_oid(
+            ExtensionOID.BASIC_CONSTRAINTS
+        )
+        assert basic_constraints.value.ca is False
+        assert basic_constraints.value.path_length is None
+
+    @pytest.mark.requires_backend_interface(interface=EllipticCurveBackend)
+    def test_build_ca_request_with_ec(self, backend):
+        _skip_curve_unsupported(backend, ec.SECP256R1())
+        private_key = ec.generate_private_key(ec.SECP256R1(), backend)
+
+        request = x509.CertificateSigningRequestBuilder().subject_name(
+            x509.Name([
+                x509.NameAttribute(NameOID.STATE_OR_PROVINCE_NAME, u'Texas'),
+            ])
+        ).add_extension(
+            x509.BasicConstraints(ca=True, path_length=2), critical=True
+        ).sign(private_key, hashes.SHA1(), backend)
+
+        assert isinstance(request.signature_hash_algorithm, hashes.SHA1)
+        public_key = request.public_key()
+        assert isinstance(public_key, ec.EllipticCurvePublicKey)
+        subject = request.subject
+        assert isinstance(subject, x509.Name)
+        assert list(subject) == [
+            x509.NameAttribute(NameOID.STATE_OR_PROVINCE_NAME, u'Texas'),
+        ]
+        basic_constraints = request.extensions.get_extension_for_oid(
+            ExtensionOID.BASIC_CONSTRAINTS
+        )
+        assert basic_constraints.value.ca is True
+        assert basic_constraints.value.path_length == 2
+
+    @pytest.mark.requires_backend_interface(interface=DSABackend)
+    def test_build_ca_request_with_dsa(self, backend):
+        private_key = DSA_KEY_2048.private_key(backend)
+
+        request = x509.CertificateSigningRequestBuilder().subject_name(
+            x509.Name([
+                x509.NameAttribute(NameOID.COUNTRY_NAME, u'US'),
+            ])
+        ).add_extension(
+            x509.BasicConstraints(ca=True, path_length=2), critical=True
+        ).sign(private_key, hashes.SHA1(), backend)
+
+        assert isinstance(request.signature_hash_algorithm, hashes.SHA1)
+        public_key = request.public_key()
+        assert isinstance(public_key, dsa.DSAPublicKey)
+        subject = request.subject
+        assert isinstance(subject, x509.Name)
+        assert list(subject) == [
+            x509.NameAttribute(NameOID.COUNTRY_NAME, u'US'),
+        ]
+        basic_constraints = request.extensions.get_extension_for_oid(
+            ExtensionOID.BASIC_CONSTRAINTS
+        )
+        assert basic_constraints.value.ca is True
+        assert basic_constraints.value.path_length == 2
+
+    def test_add_duplicate_extension(self):
+        builder = x509.CertificateSigningRequestBuilder().add_extension(
+            x509.BasicConstraints(True, 2), critical=True,
+        )
+        with pytest.raises(ValueError):
+            builder.add_extension(
+                x509.BasicConstraints(True, 2), critical=True,
+            )
+
+    def test_set_invalid_subject(self):
+        builder = x509.CertificateSigningRequestBuilder()
+        with pytest.raises(TypeError):
+            builder.subject_name('NotAName')
+
+    def test_add_invalid_extension_type(self):
+        builder = x509.CertificateSigningRequestBuilder()
+
+        with pytest.raises(TypeError):
+            builder.add_extension(object(), False)
+
+    def test_add_unsupported_extension(self, backend):
+        private_key = RSA_KEY_2048.private_key(backend)
+        builder = x509.CertificateSigningRequestBuilder()
+        builder = builder.subject_name(
+            x509.Name([
+                x509.NameAttribute(NameOID.COUNTRY_NAME, u'US'),
+            ])
+        ).add_extension(
+            x509.SubjectAlternativeName([x509.DNSName(b"cryptography.io")]),
+            critical=False,
+        ).add_extension(
+            DummyExtension(), False
+        )
+        with pytest.raises(NotImplementedError):
+            builder.sign(private_key, hashes.SHA256(), backend)
+
+    def test_key_usage(self, backend):
+        private_key = RSA_KEY_2048.private_key(backend)
+        builder = x509.CertificateSigningRequestBuilder()
+        request = builder.subject_name(
+            x509.Name([
+                x509.NameAttribute(NameOID.COUNTRY_NAME, u'US'),
+            ])
+        ).add_extension(
+            x509.KeyUsage(
+                digital_signature=True,
+                content_commitment=True,
+                key_encipherment=False,
+                data_encipherment=False,
+                key_agreement=False,
+                key_cert_sign=True,
+                crl_sign=False,
+                encipher_only=False,
+                decipher_only=False
+            ),
+            critical=False
+        ).sign(private_key, hashes.SHA256(), backend)
+        assert len(request.extensions) == 1
+        ext = request.extensions.get_extension_for_oid(ExtensionOID.KEY_USAGE)
+        assert ext.critical is False
+        assert ext.value == x509.KeyUsage(
+            digital_signature=True,
+            content_commitment=True,
+            key_encipherment=False,
+            data_encipherment=False,
+            key_agreement=False,
+            key_cert_sign=True,
+            crl_sign=False,
+            encipher_only=False,
+            decipher_only=False
+        )
+
+    def test_key_usage_key_agreement_bit(self, backend):
+        private_key = RSA_KEY_2048.private_key(backend)
+        builder = x509.CertificateSigningRequestBuilder()
+        request = builder.subject_name(
+            x509.Name([
+                x509.NameAttribute(NameOID.COUNTRY_NAME, u'US'),
+            ])
+        ).add_extension(
+            x509.KeyUsage(
+                digital_signature=False,
+                content_commitment=False,
+                key_encipherment=False,
+                data_encipherment=False,
+                key_agreement=True,
+                key_cert_sign=True,
+                crl_sign=False,
+                encipher_only=False,
+                decipher_only=True
+            ),
+            critical=False
+        ).sign(private_key, hashes.SHA256(), backend)
+        assert len(request.extensions) == 1
+        ext = request.extensions.get_extension_for_oid(ExtensionOID.KEY_USAGE)
+        assert ext.critical is False
+        assert ext.value == x509.KeyUsage(
+            digital_signature=False,
+            content_commitment=False,
+            key_encipherment=False,
+            data_encipherment=False,
+            key_agreement=True,
+            key_cert_sign=True,
+            crl_sign=False,
+            encipher_only=False,
+            decipher_only=True
+        )
+
+    def test_add_two_extensions(self, backend):
+        private_key = RSA_KEY_2048.private_key(backend)
+        builder = x509.CertificateSigningRequestBuilder()
+        request = builder.subject_name(
+            x509.Name([x509.NameAttribute(NameOID.COUNTRY_NAME, u'US')])
+        ).add_extension(
+            x509.SubjectAlternativeName([x509.DNSName(b"cryptography.io")]),
+            critical=False,
+        ).add_extension(
+            x509.BasicConstraints(ca=True, path_length=2), critical=True
+        ).sign(private_key, hashes.SHA1(), backend)
+
+        assert isinstance(request.signature_hash_algorithm, hashes.SHA1)
+        public_key = request.public_key()
+        assert isinstance(public_key, rsa.RSAPublicKey)
+        basic_constraints = request.extensions.get_extension_for_oid(
+            ExtensionOID.BASIC_CONSTRAINTS
+        )
+        assert basic_constraints.value.ca is True
+        assert basic_constraints.value.path_length == 2
+        ext = request.extensions.get_extension_for_oid(
+            ExtensionOID.SUBJECT_ALTERNATIVE_NAME
+        )
+        assert list(ext.value) == [x509.DNSName(b"cryptography.io")]
+
+    def test_set_subject_twice(self):
+        builder = x509.CertificateSigningRequestBuilder()
+        builder = builder.subject_name(
+            x509.Name([
+                x509.NameAttribute(NameOID.COUNTRY_NAME, u'US'),
+            ])
+        )
+        with pytest.raises(ValueError):
+            builder.subject_name(
+                x509.Name([
+                    x509.NameAttribute(NameOID.COUNTRY_NAME, u'US'),
+                ])
+            )
+
+    def test_subject_alt_names(self, backend):
+        private_key = RSA_KEY_2048.private_key(backend)
+
+        san = x509.SubjectAlternativeName([
+            x509.DNSName(b"example.com"),
+            x509.DNSName(b"*.example.com"),
+            x509.RegisteredID(x509.ObjectIdentifier("1.2.3.4.5.6.7")),
+            x509.DirectoryName(x509.Name([
+                x509.NameAttribute(NameOID.COMMON_NAME, u'PyCA'),
+                x509.NameAttribute(
+                    NameOID.ORGANIZATION_NAME, u'We heart UTF8!\u2122'
+                )
+            ])),
+            x509.IPAddress(ipaddress.ip_address(u"127.0.0.1")),
+            x509.IPAddress(ipaddress.ip_address(u"ff::")),
+            x509.OtherName(
+                type_id=x509.ObjectIdentifier("1.2.3.3.3.3"),
+                value=b"0\x03\x02\x01\x05"
+            ),
+            x509.RFC822Name(u"test@example.com"),
+            x509.RFC822Name(u"email"),
+            x509.RFC822Name(u"email@em\xe5\xefl.com"),
+            x509.UniformResourceIdentifier(
+                u"https://\u043f\u044b\u043a\u0430.cryptography"
+            ),
+            x509.UniformResourceIdentifier(
+                u"gopher://cryptography:70/some/path"
+            ),
+        ])
+
+        csr = x509.CertificateSigningRequestBuilder().subject_name(
+            x509.Name([
+                x509.NameAttribute(NameOID.COMMON_NAME, u"SAN"),
+            ])
+        ).add_extension(
+            san,
+            critical=False,
+        ).sign(private_key, hashes.SHA256(), backend)
+
+        assert len(csr.extensions) == 1
+        ext = csr.extensions.get_extension_for_oid(
+            ExtensionOID.SUBJECT_ALTERNATIVE_NAME
+        )
+        assert not ext.critical
+        assert ext.oid == ExtensionOID.SUBJECT_ALTERNATIVE_NAME
+        assert ext.value == san
+
+    def test_invalid_asn1_othername(self, backend):
+        private_key = RSA_KEY_2048.private_key(backend)
+
+        builder = x509.CertificateSigningRequestBuilder().subject_name(
+            x509.Name([
+                x509.NameAttribute(NameOID.COMMON_NAME, u"SAN"),
+            ])
+        ).add_extension(
+            x509.SubjectAlternativeName([
+                x509.OtherName(
+                    type_id=x509.ObjectIdentifier("1.2.3.3.3.3"),
+                    value=b"\x01\x02\x01\x05"
+                ),
+            ]),
+            critical=False,
+        )
+        with pytest.raises(ValueError):
+            builder.sign(private_key, hashes.SHA256(), backend)
+
+    def test_subject_alt_name_unsupported_general_name(self, backend):
+        private_key = RSA_KEY_2048.private_key(backend)
+
+        builder = x509.CertificateSigningRequestBuilder().subject_name(
+            x509.Name([
+                x509.NameAttribute(NameOID.COMMON_NAME, u"SAN"),
+            ])
+        ).add_extension(
+            x509.SubjectAlternativeName([FakeGeneralName("")]),
+            critical=False,
+        )
+
+        with pytest.raises(ValueError):
+            builder.sign(private_key, hashes.SHA256(), backend)
+
+    def test_extended_key_usage(self, backend):
+        private_key = RSA_KEY_2048.private_key(backend)
+        eku = x509.ExtendedKeyUsage([
+            ExtendedKeyUsageOID.CLIENT_AUTH,
+            ExtendedKeyUsageOID.SERVER_AUTH,
+            ExtendedKeyUsageOID.CODE_SIGNING,
+        ])
+        builder = x509.CertificateSigningRequestBuilder()
+        request = builder.subject_name(
+            x509.Name([x509.NameAttribute(NameOID.COUNTRY_NAME, u'US')])
+        ).add_extension(
+            eku, critical=False
+        ).sign(private_key, hashes.SHA256(), backend)
+
+        ext = request.extensions.get_extension_for_oid(
+            ExtensionOID.EXTENDED_KEY_USAGE
+        )
+        assert ext.critical is False
+        assert ext.value == eku
+
+    @pytest.mark.requires_backend_interface(interface=RSABackend)
+    def test_rsa_key_too_small(self, backend):
+        private_key = rsa.generate_private_key(65537, 512, backend)
+        builder = x509.CertificateSigningRequestBuilder()
+        builder = builder.subject_name(
+            x509.Name([x509.NameAttribute(NameOID.COUNTRY_NAME, u'US')])
+        )
+
+        with pytest.raises(ValueError) as exc:
+            builder.sign(private_key, hashes.SHA512(), backend)
+
+        assert str(exc.value) == "Digest too big for RSA key"
+
+    @pytest.mark.requires_backend_interface(interface=RSABackend)
+    @pytest.mark.requires_backend_interface(interface=X509Backend)
+    def test_build_cert_with_aia(self, backend):
+        issuer_private_key = RSA_KEY_2048.private_key(backend)
+        subject_private_key = RSA_KEY_2048.private_key(backend)
+
+        not_valid_before = datetime.datetime(2002, 1, 1, 12, 1)
+        not_valid_after = datetime.datetime(2030, 12, 31, 8, 30)
+
+        aia = x509.AuthorityInformationAccess([
+            x509.AccessDescription(
+                AuthorityInformationAccessOID.OCSP,
+                x509.UniformResourceIdentifier(b"http://ocsp.domain.com")
+            ),
+            x509.AccessDescription(
+                AuthorityInformationAccessOID.CA_ISSUERS,
+                x509.UniformResourceIdentifier(b"http://domain.com/ca.crt")
+            )
+        ])
+
+        builder = x509.CertificateBuilder().serial_number(
+            777
+        ).issuer_name(x509.Name([
+            x509.NameAttribute(NameOID.COUNTRY_NAME, u'US'),
+        ])).subject_name(x509.Name([
+            x509.NameAttribute(NameOID.COUNTRY_NAME, u'US'),
+        ])).public_key(
+            subject_private_key.public_key()
+        ).add_extension(
+            aia, critical=False
+        ).not_valid_before(
+            not_valid_before
+        ).not_valid_after(
+            not_valid_after
+        )
+
+        cert = builder.sign(issuer_private_key, hashes.SHA1(), backend)
+
+        ext = cert.extensions.get_extension_for_oid(
+            ExtensionOID.AUTHORITY_INFORMATION_ACCESS
+        )
+        assert ext.value == aia
+
+    @pytest.mark.requires_backend_interface(interface=RSABackend)
+    @pytest.mark.requires_backend_interface(interface=X509Backend)
+    def test_build_cert_with_ski(self, backend):
+        issuer_private_key = RSA_KEY_2048.private_key(backend)
+        subject_private_key = RSA_KEY_2048.private_key(backend)
+
+        not_valid_before = datetime.datetime(2002, 1, 1, 12, 1)
+        not_valid_after = datetime.datetime(2030, 12, 31, 8, 30)
+
+        ski = x509.SubjectKeyIdentifier.from_public_key(
+            subject_private_key.public_key()
+        )
+
+        builder = x509.CertificateBuilder().serial_number(
+            777
+        ).issuer_name(x509.Name([
+            x509.NameAttribute(NameOID.COUNTRY_NAME, u'US'),
+        ])).subject_name(x509.Name([
+            x509.NameAttribute(NameOID.COUNTRY_NAME, u'US'),
+        ])).public_key(
+            subject_private_key.public_key()
+        ).add_extension(
+            ski, critical=False
+        ).not_valid_before(
+            not_valid_before
+        ).not_valid_after(
+            not_valid_after
+        )
+
+        cert = builder.sign(issuer_private_key, hashes.SHA1(), backend)
+
+        ext = cert.extensions.get_extension_for_oid(
+            ExtensionOID.SUBJECT_KEY_IDENTIFIER
+        )
+        assert ext.value == ski
+
+    @pytest.mark.parametrize(
+        "aki",
+        [
+            x509.AuthorityKeyIdentifier(
+                b"\xc3\x9c\xf3\xfc\xd3F\x084\xbb\xceF\x7f\xa0|[\xf3\xe2\x08"
+                b"\xcbY",
+                None,
+                None
+            ),
+            x509.AuthorityKeyIdentifier(
+                b"\xc3\x9c\xf3\xfc\xd3F\x084\xbb\xceF\x7f\xa0|[\xf3\xe2\x08"
+                b"\xcbY",
+                [
+                    x509.DirectoryName(
+                        x509.Name([
+                            x509.NameAttribute(
+                                NameOID.ORGANIZATION_NAME, u"PyCA"
+                            ),
+                            x509.NameAttribute(
+                                NameOID.COMMON_NAME, u"cryptography CA"
+                            )
+                        ])
+                    )
+                ],
+                333
+            ),
+            x509.AuthorityKeyIdentifier(
+                None,
+                [
+                    x509.DirectoryName(
+                        x509.Name([
+                            x509.NameAttribute(
+                                NameOID.ORGANIZATION_NAME, u"PyCA"
+                            ),
+                            x509.NameAttribute(
+                                NameOID.COMMON_NAME, u"cryptography CA"
+                            )
+                        ])
+                    )
+                ],
+                333
+            ),
+        ]
+    )
+    @pytest.mark.requires_backend_interface(interface=RSABackend)
+    @pytest.mark.requires_backend_interface(interface=X509Backend)
+    def test_build_cert_with_aki(self, aki, backend):
+        issuer_private_key = RSA_KEY_2048.private_key(backend)
+        subject_private_key = RSA_KEY_2048.private_key(backend)
+
+        not_valid_before = datetime.datetime(2002, 1, 1, 12, 1)
+        not_valid_after = datetime.datetime(2030, 12, 31, 8, 30)
+
+        builder = x509.CertificateBuilder().serial_number(
+            777
+        ).issuer_name(x509.Name([
+            x509.NameAttribute(NameOID.COUNTRY_NAME, u'US'),
+        ])).subject_name(x509.Name([
+            x509.NameAttribute(NameOID.COUNTRY_NAME, u'US'),
+        ])).public_key(
+            subject_private_key.public_key()
+        ).add_extension(
+            aki, critical=False
+        ).not_valid_before(
+            not_valid_before
+        ).not_valid_after(
+            not_valid_after
+        )
+
+        cert = builder.sign(issuer_private_key, hashes.SHA256(), backend)
+
+        ext = cert.extensions.get_extension_for_oid(
+            ExtensionOID.AUTHORITY_KEY_IDENTIFIER
+        )
+        assert ext.value == aki
+
+    def test_ocsp_nocheck(self, backend):
+        issuer_private_key = RSA_KEY_2048.private_key(backend)
+        subject_private_key = RSA_KEY_2048.private_key(backend)
+
+        not_valid_before = datetime.datetime(2002, 1, 1, 12, 1)
+        not_valid_after = datetime.datetime(2030, 12, 31, 8, 30)
+
+        builder = x509.CertificateBuilder().serial_number(
+            777
+        ).issuer_name(x509.Name([
+            x509.NameAttribute(NameOID.COUNTRY_NAME, u'US'),
+        ])).subject_name(x509.Name([
+            x509.NameAttribute(NameOID.COUNTRY_NAME, u'US'),
+        ])).public_key(
+            subject_private_key.public_key()
+        ).add_extension(
+            x509.OCSPNoCheck(), critical=False
+        ).not_valid_before(
+            not_valid_before
+        ).not_valid_after(
+            not_valid_after
+        )
+
+        cert = builder.sign(issuer_private_key, hashes.SHA256(), backend)
+
+        ext = cert.extensions.get_extension_for_oid(
+            ExtensionOID.OCSP_NO_CHECK
+        )
+        assert isinstance(ext.value, x509.OCSPNoCheck)
+
+
+@pytest.mark.requires_backend_interface(interface=DSABackend)
+@pytest.mark.requires_backend_interface(interface=X509Backend)
+class TestDSACertificate(object):
+    def test_load_dsa_cert(self, backend):
+        cert = _load_cert(
+            os.path.join("x509", "custom", "dsa_selfsigned_ca.pem"),
+            x509.load_pem_x509_certificate,
+            backend
+        )
+        assert isinstance(cert.signature_hash_algorithm, hashes.SHA1)
+        public_key = cert.public_key()
+        assert isinstance(public_key, dsa.DSAPublicKey)
+        num = public_key.public_numbers()
+        assert num.y == int(
+            "4c08bfe5f2d76649c80acf7d431f6ae2124b217abc8c9f6aca776ddfa94"
+            "53b6656f13e543684cd5f6431a314377d2abfa068b7080cb8ddc065afc2"
+            "dea559f0b584c97a2b235b9b69b46bc6de1aed422a6f341832618bcaae2"
+            "198aba388099dafb05ff0b5efecb3b0ae169a62e1c72022af50ae68af3b"
+            "033c18e6eec1f7df4692c456ccafb79cc7e08da0a5786e9816ceda651d6"
+            "1b4bb7b81c2783da97cea62df67af5e85991fdc13aff10fc60e06586386"
+            "b96bb78d65750f542f86951e05a6d81baadbcd35a2e5cad4119923ae6a2"
+            "002091a3d17017f93c52970113cdc119970b9074ca506eac91c3dd37632"
+            "5df4af6b3911ef267d26623a5a1c5df4a6d13f1c", 16
+        )
+        assert num.parameter_numbers.g == int(
+            "4b7ced71dc353965ecc10d441a9a06fc24943a32d66429dd5ef44d43e67"
+            "d789d99770aec32c0415dc92970880872da45fef8dd1e115a3e4801387b"
+            "a6d755861f062fd3b6e9ea8e2641152339b828315b1528ee6c7b79458d2"
+            "1f3db973f6fc303f9397174c2799dd2351282aa2d8842c357a73495bbaa"
+            "c4932786414c55e60d73169f5761036fba29e9eebfb049f8a3b1b7cee6f"
+            "3fbfa136205f130bee2cf5b9c38dc1095d4006f2e73335c07352c64130a"
+            "1ab2b89f13b48f628d3cc3868beece9bb7beade9f830eacc6fa241425c0"
+            "b3fcc0df416a0c89f7bf35668d765ec95cdcfbe9caff49cfc156c668c76"
+            "fa6247676a6d3ac945844a083509c6a1b436baca", 16
+        )
+        assert num.parameter_numbers.p == int(
+            "bfade6048e373cd4e48b677e878c8e5b08c02102ae04eb2cb5c46a523a3"
+            "af1c73d16b24f34a4964781ae7e50500e21777754a670bd19a7420d6330"
+            "84e5556e33ca2c0e7d547ea5f46a07a01bf8669ae3bdec042d9b2ae5e6e"
+            "cf49f00ba9dac99ab6eff140d2cedf722ee62c2f9736857971444c25d0a"
+            "33d2017dc36d682a1054fe2a9428dda355a851ce6e6d61e03e419fd4ca4"
+            "e703313743d86caa885930f62ed5bf342d8165627681e9cc3244ba72aa2"
+            "2148400a6bbe80154e855d042c9dc2a3405f1e517be9dea50562f56da93"
+            "f6085f844a7e705c1f043e65751c583b80d29103e590ccb26efdaa0893d"
+            "833e36468f3907cfca788a3cb790f0341c8a31bf", 16
+        )
+        assert num.parameter_numbers.q == int(
+            "822ff5d234e073b901cf5941f58e1f538e71d40d", 16
+        )
+
+    def test_signature(self, backend):
+        cert = _load_cert(
+            os.path.join("x509", "custom", "dsa_selfsigned_ca.pem"),
+            x509.load_pem_x509_certificate,
+            backend
+        )
+        assert cert.signature == binascii.unhexlify(
+            b"302c021425c4a84a936ab311ee017d3cbd9a3c650bb3ae4a02145d30c64b4326"
+            b"86bdf925716b4ed059184396bcce"
+        )
+        r, s = decode_dss_signature(cert.signature)
+        assert r == 215618264820276283222494627481362273536404860490
+        assert s == 532023851299196869156027211159466197586787351758
+
+    def test_tbs_certificate_bytes(self, backend):
+        cert = _load_cert(
+            os.path.join("x509", "custom", "dsa_selfsigned_ca.pem"),
+            x509.load_pem_x509_certificate,
+            backend
+        )
+        assert cert.tbs_certificate_bytes == binascii.unhexlify(
+            b"3082051aa003020102020900a37352e0b2142f86300906072a8648ce3804033"
+            b"067310b3009060355040613025553310e300c06035504081305546578617331"
+            b"0f300d0603550407130641757374696e3121301f060355040a1318496e74657"
+            b"26e6574205769646769747320507479204c7464311430120603550403130b50"
+            b"79434120445341204341301e170d3134313132373035313431375a170d31343"
+            b"13232373035313431375a3067310b3009060355040613025553310e300c0603"
+            b"55040813055465786173310f300d0603550407130641757374696e3121301f0"
+            b"60355040a1318496e7465726e6574205769646769747320507479204c746431"
+            b"1430120603550403130b50794341204453412043413082033a3082022d06072"
+            b"a8648ce380401308202200282010100bfade6048e373cd4e48b677e878c8e5b"
+            b"08c02102ae04eb2cb5c46a523a3af1c73d16b24f34a4964781ae7e50500e217"
+            b"77754a670bd19a7420d633084e5556e33ca2c0e7d547ea5f46a07a01bf8669a"
+            b"e3bdec042d9b2ae5e6ecf49f00ba9dac99ab6eff140d2cedf722ee62c2f9736"
+            b"857971444c25d0a33d2017dc36d682a1054fe2a9428dda355a851ce6e6d61e0"
+            b"3e419fd4ca4e703313743d86caa885930f62ed5bf342d8165627681e9cc3244"
+            b"ba72aa22148400a6bbe80154e855d042c9dc2a3405f1e517be9dea50562f56d"
+            b"a93f6085f844a7e705c1f043e65751c583b80d29103e590ccb26efdaa0893d8"
+            b"33e36468f3907cfca788a3cb790f0341c8a31bf021500822ff5d234e073b901"
+            b"cf5941f58e1f538e71d40d028201004b7ced71dc353965ecc10d441a9a06fc2"
+            b"4943a32d66429dd5ef44d43e67d789d99770aec32c0415dc92970880872da45"
+            b"fef8dd1e115a3e4801387ba6d755861f062fd3b6e9ea8e2641152339b828315"
+            b"b1528ee6c7b79458d21f3db973f6fc303f9397174c2799dd2351282aa2d8842"
+            b"c357a73495bbaac4932786414c55e60d73169f5761036fba29e9eebfb049f8a"
+            b"3b1b7cee6f3fbfa136205f130bee2cf5b9c38dc1095d4006f2e73335c07352c"
+            b"64130a1ab2b89f13b48f628d3cc3868beece9bb7beade9f830eacc6fa241425"
+            b"c0b3fcc0df416a0c89f7bf35668d765ec95cdcfbe9caff49cfc156c668c76fa"
+            b"6247676a6d3ac945844a083509c6a1b436baca0382010500028201004c08bfe"
+            b"5f2d76649c80acf7d431f6ae2124b217abc8c9f6aca776ddfa9453b6656f13e"
+            b"543684cd5f6431a314377d2abfa068b7080cb8ddc065afc2dea559f0b584c97"
+            b"a2b235b9b69b46bc6de1aed422a6f341832618bcaae2198aba388099dafb05f"
+            b"f0b5efecb3b0ae169a62e1c72022af50ae68af3b033c18e6eec1f7df4692c45"
+            b"6ccafb79cc7e08da0a5786e9816ceda651d61b4bb7b81c2783da97cea62df67"
+            b"af5e85991fdc13aff10fc60e06586386b96bb78d65750f542f86951e05a6d81"
+            b"baadbcd35a2e5cad4119923ae6a2002091a3d17017f93c52970113cdc119970"
+            b"b9074ca506eac91c3dd376325df4af6b3911ef267d26623a5a1c5df4a6d13f1"
+            b"ca381cc3081c9301d0603551d0e04160414a4fb887a13fcdeb303bbae9a1dec"
+            b"a72f125a541b3081990603551d2304819130818e8014a4fb887a13fcdeb303b"
+            b"bae9a1deca72f125a541ba16ba4693067310b3009060355040613025553310e"
+            b"300c060355040813055465786173310f300d0603550407130641757374696e3"
+            b"121301f060355040a1318496e7465726e657420576964676974732050747920"
+            b"4c7464311430120603550403130b5079434120445341204341820900a37352e"
+            b"0b2142f86300c0603551d13040530030101ff"
+        )
+        verifier = cert.public_key().verifier(
+            cert.signature, cert.signature_hash_algorithm
+        )
+        verifier.update(cert.tbs_certificate_bytes)
+        verifier.verify()
+
+
+@pytest.mark.requires_backend_interface(interface=DSABackend)
+@pytest.mark.requires_backend_interface(interface=X509Backend)
+class TestDSACertificateRequest(object):
+    @pytest.mark.parametrize(
+        ("path", "loader_func"),
+        [
+            [
+                os.path.join("x509", "requests", "dsa_sha1.pem"),
+                x509.load_pem_x509_csr
+            ],
+            [
+                os.path.join("x509", "requests", "dsa_sha1.der"),
+                x509.load_der_x509_csr
+            ],
+        ]
+    )
+    def test_load_dsa_request(self, path, loader_func, backend):
+        request = _load_cert(path, loader_func, backend)
+        assert isinstance(request.signature_hash_algorithm, hashes.SHA1)
+        public_key = request.public_key()
+        assert isinstance(public_key, dsa.DSAPublicKey)
+        subject = request.subject
+        assert isinstance(subject, x509.Name)
+        assert list(subject) == [
+            x509.NameAttribute(NameOID.COMMON_NAME, u'cryptography.io'),
+            x509.NameAttribute(NameOID.ORGANIZATION_NAME, u'PyCA'),
+            x509.NameAttribute(NameOID.COUNTRY_NAME, u'US'),
+            x509.NameAttribute(NameOID.STATE_OR_PROVINCE_NAME, u'Texas'),
+            x509.NameAttribute(NameOID.LOCALITY_NAME, u'Austin'),
+        ]
+
+    def test_signature(self, backend):
+        request = _load_cert(
+            os.path.join("x509", "requests", "dsa_sha1.pem"),
+            x509.load_pem_x509_csr,
+            backend
+        )
+        assert request.signature == binascii.unhexlify(
+            b"302c021461d58dc028d0110818a7d817d74235727c4acfdf0214097b52e198e"
+            b"ce95de17273f0a924df23ce9d8188"
+        )
+
+    def test_tbs_certrequest_bytes(self, backend):
+        request = _load_cert(
+            os.path.join("x509", "requests", "dsa_sha1.pem"),
+            x509.load_pem_x509_csr,
+            backend
+        )
+        assert request.tbs_certrequest_bytes == binascii.unhexlify(
+            b"3082021802010030573118301606035504030c0f63727970746f677261706879"
+            b"2e696f310d300b060355040a0c0450794341310b300906035504061302555331"
+            b"0e300c06035504080c055465786173310f300d06035504070c0641757374696e"
+            b"308201b63082012b06072a8648ce3804013082011e028181008d7fadbc09e284"
+            b"aafa69154cea24177004909e519f8b35d685cde5b4ecdc9583e74d370a0f88ad"
+            b"a98f026f27762fb3d5da7836f986dfcdb3589e5b925bea114defc03ef81dae30"
+            b"c24bbc6df3d588e93427bba64203d4a5b1687b2b5e3b643d4c614976f89f95a3"
+            b"8d3e4c89065fba97514c22c50adbbf289163a74b54859b35b7021500835de56b"
+            b"d07cf7f82e2032fe78949aed117aa2ef0281801f717b5a07782fc2e4e68e311f"
+            b"ea91a54edd36b86ac634d14f05a68a97eae9d2ef31fb1ef3de42c3d100df9ca6"
+            b"4f5bdc2aec7bfdfb474cf831fea05853b5e059f2d24980a0ac463f1e818af352"
+            b"3e3cb79a39d45fa92731897752842469cf8540b01491024eaafbce6018e8a1f4"
+            b"658c343f4ba7c0b21e5376a21f4beb8491961e038184000281800713f07641f6"
+            b"369bb5a9545274a2d4c01998367fb371bb9e13436363672ed68f82174c2de05c"
+            b"8e839bc6de568dd50ba28d8d9d8719423aaec5557df10d773ab22d6d65cbb878"
+            b"04a697bc8fd965b952f9f7e850edf13c8acdb5d753b6d10e59e0b5732e3c82ba"
+            b"fa140342bc4a3bba16bd0681c8a6a2dbbb7efe6ce2b8463b170ba000"
+        )
+        verifier = request.public_key().verifier(
+            request.signature,
+            request.signature_hash_algorithm
+        )
+        verifier.update(request.tbs_certrequest_bytes)
+        verifier.verify()
+
+
+@pytest.mark.requires_backend_interface(interface=EllipticCurveBackend)
+@pytest.mark.requires_backend_interface(interface=X509Backend)
+class TestECDSACertificate(object):
+    def test_load_ecdsa_cert(self, backend):
+        _skip_curve_unsupported(backend, ec.SECP384R1())
+        cert = _load_cert(
+            os.path.join("x509", "ecdsa_root.pem"),
+            x509.load_pem_x509_certificate,
+            backend
+        )
+        assert isinstance(cert.signature_hash_algorithm, hashes.SHA384)
+        public_key = cert.public_key()
+        assert isinstance(public_key, ec.EllipticCurvePublicKey)
+        num = public_key.public_numbers()
+        assert num.x == int(
+            "dda7d9bb8ab80bfb0b7f21d2f0bebe73f3335d1abc34eadec69bbcd095f"
+            "6f0ccd00bba615b51467e9e2d9fee8e630c17", 16
+        )
+        assert num.y == int(
+            "ec0770f5cf842e40839ce83f416d3badd3a4145936789d0343ee10136c7"
+            "2deae88a7a16bb543ce67dc23ff031ca3e23e", 16
+        )
+        assert isinstance(num.curve, ec.SECP384R1)
+
+    def test_signature(self, backend):
+        cert = _load_cert(
+            os.path.join("x509", "ecdsa_root.pem"),
+            x509.load_pem_x509_certificate,
+            backend
+        )
+        assert cert.signature == binascii.unhexlify(
+            b"3065023100adbcf26c3f124ad12d39c30a099773f488368c8827bbe6888d5085"
+            b"a763f99e32de66930ff1ccb1098fdd6cabfa6b7fa0023039665bc2648db89e50"
+            b"dca8d549a2edc7dcd1497f1701b8c8868f4e8c882ba89aa98ac5d100bdf854e2"
+            b"9ae55b7cb32717"
+        )
+        r, s = decode_dss_signature(cert.signature)
+        assert r == int(
+            "adbcf26c3f124ad12d39c30a099773f488368c8827bbe6888d5085a763f99e32"
+            "de66930ff1ccb1098fdd6cabfa6b7fa0",
+            16
+        )
+        assert s == int(
+            "39665bc2648db89e50dca8d549a2edc7dcd1497f1701b8c8868f4e8c882ba89a"
+            "a98ac5d100bdf854e29ae55b7cb32717",
+            16
+        )
+
+    def test_tbs_certificate_bytes(self, backend):
+        _skip_curve_unsupported(backend, ec.SECP384R1())
+        cert = _load_cert(
+            os.path.join("x509", "ecdsa_root.pem"),
+            x509.load_pem_x509_certificate,
+            backend
+        )
+        assert cert.tbs_certificate_bytes == binascii.unhexlify(
+            b"308201c5a0030201020210055556bcf25ea43535c3a40fd5ab4572300a06082"
+            b"a8648ce3d0403033061310b300906035504061302555331153013060355040a"
+            b"130c446967694365727420496e6331193017060355040b13107777772e64696"
+            b"769636572742e636f6d3120301e06035504031317446967694365727420476c"
+            b"6f62616c20526f6f74204733301e170d3133303830313132303030305a170d3"
+            b"338303131353132303030305a3061310b300906035504061302555331153013"
+            b"060355040a130c446967694365727420496e6331193017060355040b1310777"
+            b"7772e64696769636572742e636f6d3120301e06035504031317446967694365"
+            b"727420476c6f62616c20526f6f742047333076301006072a8648ce3d0201060"
+            b"52b8104002203620004dda7d9bb8ab80bfb0b7f21d2f0bebe73f3335d1abc34"
+            b"eadec69bbcd095f6f0ccd00bba615b51467e9e2d9fee8e630c17ec0770f5cf8"
+            b"42e40839ce83f416d3badd3a4145936789d0343ee10136c72deae88a7a16bb5"
+            b"43ce67dc23ff031ca3e23ea3423040300f0603551d130101ff040530030101f"
+            b"f300e0603551d0f0101ff040403020186301d0603551d0e04160414b3db48a4"
+            b"f9a1c5d8ae3641cc1163696229bc4bc6"
+        )
+        verifier = cert.public_key().verifier(
+            cert.signature, ec.ECDSA(cert.signature_hash_algorithm)
+        )
+        verifier.update(cert.tbs_certificate_bytes)
+        verifier.verify()
+
+    def test_load_ecdsa_no_named_curve(self, backend):
+        _skip_curve_unsupported(backend, ec.SECP256R1())
+        cert = _load_cert(
+            os.path.join("x509", "custom", "ec_no_named_curve.pem"),
+            x509.load_pem_x509_certificate,
+            backend
+        )
+        with pytest.raises(NotImplementedError):
+            cert.public_key()
+
+
+@pytest.mark.requires_backend_interface(interface=X509Backend)
+@pytest.mark.requires_backend_interface(interface=EllipticCurveBackend)
+class TestECDSACertificateRequest(object):
+    @pytest.mark.parametrize(
+        ("path", "loader_func"),
+        [
+            [
+                os.path.join("x509", "requests", "ec_sha256.pem"),
+                x509.load_pem_x509_csr
+            ],
+            [
+                os.path.join("x509", "requests", "ec_sha256.der"),
+                x509.load_der_x509_csr
+            ],
+        ]
+    )
+    def test_load_ecdsa_certificate_request(self, path, loader_func, backend):
+        _skip_curve_unsupported(backend, ec.SECP384R1())
+        request = _load_cert(path, loader_func, backend)
+        assert isinstance(request.signature_hash_algorithm, hashes.SHA256)
+        public_key = request.public_key()
+        assert isinstance(public_key, ec.EllipticCurvePublicKey)
+        subject = request.subject
+        assert isinstance(subject, x509.Name)
+        assert list(subject) == [
+            x509.NameAttribute(NameOID.COMMON_NAME, u'cryptography.io'),
+            x509.NameAttribute(NameOID.ORGANIZATION_NAME, u'PyCA'),
+            x509.NameAttribute(NameOID.COUNTRY_NAME, u'US'),
+            x509.NameAttribute(NameOID.STATE_OR_PROVINCE_NAME, u'Texas'),
+            x509.NameAttribute(NameOID.LOCALITY_NAME, u'Austin'),
+        ]
+
+    def test_signature(self, backend):
+        _skip_curve_unsupported(backend, ec.SECP384R1())
+        request = _load_cert(
+            os.path.join("x509", "requests", "ec_sha256.pem"),
+            x509.load_pem_x509_csr,
+            backend
+        )
+        assert request.signature == binascii.unhexlify(
+            b"306502302c1a9f7de8c1787332d2307a886b476a59f172b9b0e250262f3238b1"
+            b"b45ee112bb6eb35b0fb56a123b9296eb212dffc302310094cf440c95c52827d5"
+            b"56ae6d76500e3008255d47c29f7ee782ed7558e51bfd76aa45df6d999ed5c463"
+            b"347fe2382d1751"
+        )
+
+    def test_tbs_certrequest_bytes(self, backend):
+        _skip_curve_unsupported(backend, ec.SECP384R1())
+        request = _load_cert(
+            os.path.join("x509", "requests", "ec_sha256.pem"),
+            x509.load_pem_x509_csr,
+            backend
+        )
+        assert request.tbs_certrequest_bytes == binascii.unhexlify(
+            b"3081d602010030573118301606035504030c0f63727970746f6772617068792"
+            b"e696f310d300b060355040a0c0450794341310b300906035504061302555331"
+            b"0e300c06035504080c055465786173310f300d06035504070c0641757374696"
+            b"e3076301006072a8648ce3d020106052b8104002203620004de19b514c0b3c3"
+            b"ae9b398ea3e26b5e816bdcf9102cad8f12fe02f9e4c9248724b39297ed7582e"
+            b"04d8b32a551038d09086803a6d3fb91a1a1167ec02158b00efad39c9396462f"
+            b"accff0ffaf7155812909d3726bd59fde001cff4bb9b2f5af8cbaa000"
+        )
+        verifier = request.public_key().verifier(
+            request.signature,
+            ec.ECDSA(request.signature_hash_algorithm)
+        )
+        verifier.update(request.tbs_certrequest_bytes)
+        verifier.verify()
+
+
+@pytest.mark.requires_backend_interface(interface=X509Backend)
+class TestOtherCertificate(object):
+    def test_unsupported_subject_public_key_info(self, backend):
+        cert = _load_cert(
+            os.path.join(
+                "x509", "custom", "unsupported_subject_public_key_info.pem"
+            ),
+            x509.load_pem_x509_certificate,
+            backend,
+        )
+
+        with pytest.raises(ValueError):
+            cert.public_key()
+
+
+class TestNameAttribute(object):
+    def test_init_bad_oid(self):
+        with pytest.raises(TypeError):
+            x509.NameAttribute(None, u'value')
+
+    def test_init_bad_value(self):
+        with pytest.raises(TypeError):
+            x509.NameAttribute(
+                x509.ObjectIdentifier('2.999.1'),
+                b'bytes'
+            )
+
+    def test_init_bad_country_code_value(self):
+        with pytest.raises(ValueError):
+            x509.NameAttribute(
+                NameOID.COUNTRY_NAME,
+                u'United States'
+            )
+
+        # unicode string of length 2, but > 2 bytes
+        with pytest.raises(ValueError):
+            x509.NameAttribute(
+                NameOID.COUNTRY_NAME,
+                u'\U0001F37A\U0001F37A'
+            )
+
+    def test_init_empty_value(self):
+        with pytest.raises(ValueError):
+            x509.NameAttribute(NameOID.ORGANIZATION_NAME, u'')
+
+    def test_eq(self):
+        assert x509.NameAttribute(
+            x509.ObjectIdentifier('2.999.1'), u'value'
+        ) == x509.NameAttribute(
+            x509.ObjectIdentifier('2.999.1'), u'value'
+        )
+
+    def test_ne(self):
+        assert x509.NameAttribute(
+            x509.ObjectIdentifier('2.5.4.3'), u'value'
+        ) != x509.NameAttribute(
+            x509.ObjectIdentifier('2.5.4.5'), u'value'
+        )
+        assert x509.NameAttribute(
+            x509.ObjectIdentifier('2.999.1'), u'value'
+        ) != x509.NameAttribute(
+            x509.ObjectIdentifier('2.999.1'), u'value2'
+        )
+        assert x509.NameAttribute(
+            x509.ObjectIdentifier('2.999.2'), u'value'
+        ) != object()
+
+    def test_repr(self):
+        na = x509.NameAttribute(x509.ObjectIdentifier('2.5.4.3'), u'value')
+        if six.PY3:
+            assert repr(na) == (
+                "<NameAttribute(oid=<ObjectIdentifier(oid=2.5.4.3, name=commo"
+                "nName)>, value='value')>"
+            )
+        else:
+            assert repr(na) == (
+                "<NameAttribute(oid=<ObjectIdentifier(oid=2.5.4.3, name=commo"
+                "nName)>, value=u'value')>"
+            )
+
+
+class TestRelativeDistinguishedName(object):
+    def test_init_empty(self):
+        with pytest.raises(ValueError):
+            x509.RelativeDistinguishedName([])
+
+    def test_init_not_nameattribute(self):
+        with pytest.raises(TypeError):
+            x509.RelativeDistinguishedName(["not-a-NameAttribute"])
+
+    def test_init_duplicate_attribute(self):
+        rdn = x509.RelativeDistinguishedName([
+            x509.NameAttribute(x509.ObjectIdentifier('2.999.1'), u'value1'),
+            x509.NameAttribute(x509.ObjectIdentifier('2.999.1'), u'value1'),
+        ])
+        assert len(rdn) == 1
+
+    def test_hash(self):
+        rdn1 = x509.RelativeDistinguishedName([
+            x509.NameAttribute(x509.ObjectIdentifier('2.999.1'), u'value1'),
+            x509.NameAttribute(x509.ObjectIdentifier('2.999.2'), u'value2'),
+        ])
+        rdn2 = x509.RelativeDistinguishedName([
+            x509.NameAttribute(x509.ObjectIdentifier('2.999.2'), u'value2'),
+            x509.NameAttribute(x509.ObjectIdentifier('2.999.1'), u'value1'),
+        ])
+        rdn3 = x509.RelativeDistinguishedName([
+            x509.NameAttribute(x509.ObjectIdentifier('2.999.1'), u'value1'),
+            x509.NameAttribute(x509.ObjectIdentifier('2.999.2'), u'value3'),
+        ])
+        assert hash(rdn1) == hash(rdn2)
+        assert hash(rdn1) != hash(rdn3)
+
+    def test_eq(self):
+        rdn1 = x509.RelativeDistinguishedName([
+            x509.NameAttribute(x509.ObjectIdentifier('2.999.1'), u'value1'),
+            x509.NameAttribute(x509.ObjectIdentifier('2.999.2'), u'value2'),
+        ])
+        rdn2 = x509.RelativeDistinguishedName([
+            x509.NameAttribute(x509.ObjectIdentifier('2.999.2'), u'value2'),
+            x509.NameAttribute(x509.ObjectIdentifier('2.999.1'), u'value1'),
+        ])
+        assert rdn1 == rdn2
+
+    def test_ne(self):
+        rdn1 = x509.RelativeDistinguishedName([
+            x509.NameAttribute(x509.ObjectIdentifier('2.999.1'), u'value1'),
+            x509.NameAttribute(x509.ObjectIdentifier('2.999.2'), u'value2'),
+        ])
+        rdn2 = x509.RelativeDistinguishedName([
+            x509.NameAttribute(x509.ObjectIdentifier('2.999.1'), u'value1'),
+            x509.NameAttribute(x509.ObjectIdentifier('2.999.2'), u'value3'),
+        ])
+        assert rdn1 != rdn2
+        assert rdn1 != object()
+
+    def test_iter_input(self):
+        attrs = [
+            x509.NameAttribute(x509.ObjectIdentifier('2.999.1'), u'value1')
+        ]
+        rdn = x509.RelativeDistinguishedName(iter(attrs))
+        assert list(rdn) == attrs
+        assert list(rdn) == attrs
+
+    def test_get_attributes_for_oid(self):
+        oid = x509.ObjectIdentifier('2.999.1')
+        attr = x509.NameAttribute(oid, u'value1')
+        rdn = x509.RelativeDistinguishedName([attr])
+        assert rdn.get_attributes_for_oid(oid) == [attr]
+        assert rdn.get_attributes_for_oid(x509.ObjectIdentifier('1.2.3')) == []
+
+
+class TestObjectIdentifier(object):
+    def test_eq(self):
+        oid1 = x509.ObjectIdentifier('2.999.1')
+        oid2 = x509.ObjectIdentifier('2.999.1')
+        assert oid1 == oid2
+
+    def test_ne(self):
+        oid1 = x509.ObjectIdentifier('2.999.1')
+        assert oid1 != x509.ObjectIdentifier('2.999.2')
+        assert oid1 != object()
+
+    def test_repr(self):
+        oid = x509.ObjectIdentifier("2.5.4.3")
+        assert repr(oid) == "<ObjectIdentifier(oid=2.5.4.3, name=commonName)>"
+        oid = x509.ObjectIdentifier("2.999.1")
+        assert repr(oid) == "<ObjectIdentifier(oid=2.999.1, name=Unknown OID)>"
+
+    def test_name_property(self):
+        oid = x509.ObjectIdentifier("2.5.4.3")
+        assert oid._name == 'commonName'
+        oid = x509.ObjectIdentifier("2.999.1")
+        assert oid._name == 'Unknown OID'
+
+    def test_too_short(self):
+        with pytest.raises(ValueError):
+            x509.ObjectIdentifier("1")
+
+    def test_invalid_input(self):
+        with pytest.raises(ValueError):
+            x509.ObjectIdentifier("notavalidform")
+
+    def test_invalid_node1(self):
+        with pytest.raises(ValueError):
+            x509.ObjectIdentifier("7.1.37")
+
+    def test_invalid_node2(self):
+        with pytest.raises(ValueError):
+            x509.ObjectIdentifier("1.50.200")
+
+    def test_valid(self):
+        x509.ObjectIdentifier("0.35.200")
+        x509.ObjectIdentifier("1.39.999")
+        x509.ObjectIdentifier("2.5.29.3")
+        x509.ObjectIdentifier("2.999.37.5.22.8")
+        x509.ObjectIdentifier("2.25.305821105408246119474742976030998643995")
+
+
+class TestName(object):
+    def test_eq(self):
+        ava1 = x509.NameAttribute(x509.ObjectIdentifier('2.999.1'), u'value1')
+        ava2 = x509.NameAttribute(x509.ObjectIdentifier('2.999.2'), u'value2')
+        name1 = x509.Name([ava1, ava2])
+        name2 = x509.Name([
+            x509.RelativeDistinguishedName([ava1]),
+            x509.RelativeDistinguishedName([ava2]),
+        ])
+        name3 = x509.Name([x509.RelativeDistinguishedName([ava1, ava2])])
+        name4 = x509.Name([x509.RelativeDistinguishedName([ava2, ava1])])
+        assert name1 == name2
+        assert name3 == name4
+
+    def test_ne(self):
+        ava1 = x509.NameAttribute(x509.ObjectIdentifier('2.999.1'), u'value1')
+        ava2 = x509.NameAttribute(x509.ObjectIdentifier('2.999.2'), u'value2')
+        name1 = x509.Name([ava1, ava2])
+        name2 = x509.Name([ava2, ava1])
+        name3 = x509.Name([x509.RelativeDistinguishedName([ava1, ava2])])
+        assert name1 != name2
+        assert name1 != name3
+        assert name1 != object()
+
+    def test_hash(self):
+        ava1 = x509.NameAttribute(x509.ObjectIdentifier('2.999.1'), u'value1')
+        ava2 = x509.NameAttribute(x509.ObjectIdentifier('2.999.2'), u'value2')
+        name1 = x509.Name([ava1, ava2])
+        name2 = x509.Name([
+            x509.RelativeDistinguishedName([ava1]),
+            x509.RelativeDistinguishedName([ava2]),
+        ])
+        name3 = x509.Name([ava2, ava1])
+        name4 = x509.Name([x509.RelativeDistinguishedName([ava1, ava2])])
+        name5 = x509.Name([x509.RelativeDistinguishedName([ava2, ava1])])
+        assert hash(name1) == hash(name2)
+        assert hash(name1) != hash(name3)
+        assert hash(name1) != hash(name4)
+        assert hash(name4) == hash(name5)
+
+    def test_iter_input(self):
+        attrs = [
+            x509.NameAttribute(x509.ObjectIdentifier('2.999.1'), u'value1')
+        ]
+        name = x509.Name(iter(attrs))
+        assert list(name) == attrs
+        assert list(name) == attrs
+
+    def test_rdns(self):
+        rdn1 = x509.NameAttribute(x509.ObjectIdentifier('2.999.1'), u'value1')
+        rdn2 = x509.NameAttribute(x509.ObjectIdentifier('2.999.2'), u'value2')
+        name1 = x509.Name([rdn1, rdn2])
+        assert name1.rdns == [
+            x509.RelativeDistinguishedName([rdn1]),
+            x509.RelativeDistinguishedName([rdn2]),
+        ]
+        name2 = x509.Name([x509.RelativeDistinguishedName([rdn1, rdn2])])
+        assert name2.rdns == [x509.RelativeDistinguishedName([rdn1, rdn2])]
+
+    def test_repr(self):
+        name = x509.Name([
+            x509.NameAttribute(NameOID.COMMON_NAME, u'cryptography.io'),
+            x509.NameAttribute(NameOID.ORGANIZATION_NAME, u'PyCA'),
+        ])
+
+        if six.PY3:
+            assert repr(name) == (
+                "<Name([<NameAttribute(oid=<ObjectIdentifier(oid=2.5.4.3, name"
+                "=commonName)>, value='cryptography.io')>, <NameAttribute(oid="
+                "<ObjectIdentifier(oid=2.5.4.10, name=organizationName)>, valu"
+                "e='PyCA')>])>"
+            )
+        else:
+            assert repr(name) == (
+                "<Name([<NameAttribute(oid=<ObjectIdentifier(oid=2.5.4.3, name"
+                "=commonName)>, value=u'cryptography.io')>, <NameAttribute(oid"
+                "=<ObjectIdentifier(oid=2.5.4.10, name=organizationName)>, val"
+                "ue=u'PyCA')>])>"
+            )
+
+    def test_not_nameattribute(self):
+        with pytest.raises(TypeError):
+            x509.Name(["not-a-NameAttribute"])
+
+    @pytest.mark.requires_backend_interface(interface=X509Backend)
+    def test_bytes(self, backend):
+        name = x509.Name([
+            x509.NameAttribute(NameOID.COMMON_NAME, u'cryptography.io'),
+            x509.NameAttribute(NameOID.ORGANIZATION_NAME, u'PyCA'),
+        ])
+        assert name.public_bytes(backend) == binascii.unhexlify(
+            b"30293118301606035504030c0f63727970746f6772617068792e696f310d300"
+            b"b060355040a0c0450794341"
+        )
+
+
+def test_random_serial_number(monkeypatch):
+    sample_data = os.urandom(20)
+
+    def notrandom(size):
+        assert size == len(sample_data)
+        return sample_data
+
+    monkeypatch.setattr(os, "urandom", notrandom)
+
+    serial_number = x509.random_serial_number()
+
+    assert (
+        serial_number == utils.int_from_bytes(sample_data, "big") >> 1
+    )
+    assert utils.bit_length(serial_number) < 160