Refs #3461 -- parse SCTs from x.509 extension (#3480)

* Stub API for SCTs, feedback wanted

* grr, flake8

* finish up the __init__

* Initial implementation and tests

* write a test. it fails because computer

* get the tests passing and fix some TODOs

* changelog entry

* This can go now

* Put a skip in this test

* grump

* Removed unreachable code

* moved changelog to the correct section

* Use the deocrator for expressing requirements

* This needs f for the right entry_type

* coverage

* syntax error

* tests for coverage

* better sct eq tests

* docs

* technically correct, the most useless kind of correct

* typo and more details

* bug

* drop __eq__

1 files changed, 36 insertions, 0 deletions

diff --git a/src/cryptography/x509/extensions.py b/src/cryptography/x509/extensions.py
index aa30f8ff..1b64f4a5 100644
--- a/src/cryptography/x509/extensions.py
+++ b/src/cryptography/x509/extensions.py
@@ -18,6 +18,9 @@ from cryptography import utils
 from cryptography.hazmat.primitives import constant_time, serialization
 from cryptography.hazmat.primitives.asymmetric.ec import EllipticCurvePublicKey
 from cryptography.hazmat.primitives.asymmetric.rsa import RSAPublicKey
+from cryptography.x509.certificate_transparency import (
+    SignedCertificateTimestamp
+)
 from cryptography.x509.general_name import GeneralName, IPAddress, OtherName
 from cryptography.x509.name import RelativeDistinguishedName
 from cryptography.x509.oid import (
@@ -1152,6 +1155,39 @@ class InvalidityDate(object):
 
 
 @utils.register_interface(ExtensionType)
+class PrecertificateSignedCertificateTimestamps(object):
+    oid = ExtensionOID.PRECERT_SIGNED_CERTIFICATE_TIMESTAMPS
+
+    def __init__(self, signed_certificate_timestamps):
+        signed_certificate_timestamps = list(signed_certificate_timestamps)
+        if not all(
+            isinstance(sct, SignedCertificateTimestamp)
+            for sct in signed_certificate_timestamps
+        ):
+            raise TypeError(
+                "Every item in the signed_certificate_timestamps list must be "
+                "a SignedCertificateTimestamp"
+            )
+        self._signed_certificate_timestamps = signed_certificate_timestamps
+
+    def __iter__(self):
+        return iter(self._signed_certificate_timestamps)
+
+    def __len__(self):
+        return len(self._signed_certificate_timestamps)
+
+    def __getitem__(self, idx):
+        return self._signed_certificate_timestamps[idx]
+
+    def __repr__(self):
+        return (
+            "<PrecertificateSignedCertificateTimestamps({0})>".format(
+                list(self)
+            )
+        )
+
+
+@utils.register_interface(ExtensionType)
 class UnrecognizedExtension(object):
     def __init__(self, oid, value):
         if not isinstance(oid, ObjectIdentifier):