Merge pull request #157 from reaperhulk/hmac

HMAC support

10 files changed, 436 insertions, 5 deletions

diff --git a/cryptography/hazmat/bindings/openssl/backend.py b/cryptography/hazmat/bindings/openssl/backend.py
index 494430ba..635d6a0c 100644
--- a/cryptography/hazmat/bindings/openssl/backend.py
+++ b/cryptography/hazmat/bindings/openssl/backend.py
@@ -96,6 +96,7 @@ class Backend(object):
 
         self.ciphers = Ciphers(self)
         self.hashes = Hashes(self)
+        self.hmacs = HMACs(self)
 
     def openssl_version_text(self):
         """
@@ -259,4 +260,43 @@ class Hashes(object):
         return copied_ctx
 
 
+class HMACs(object):
+    def __init__(self, backend):
+        super(HMACs, self).__init__()
+        self._backend = backend
+
+    def create_ctx(self, key, hash_cls):
+        ctx = self._backend.ffi.new("HMAC_CTX *")
+        self._backend.lib.HMAC_CTX_init(ctx)
+        ctx = self._backend.ffi.gc(ctx, self._backend.lib.HMAC_CTX_cleanup)
+        evp_md = self._backend.lib.EVP_get_digestbyname(
+            hash_cls.name.encode('ascii'))
+        assert evp_md != self._backend.ffi.NULL
+        res = self._backend.lib.HMAC_Init_ex(ctx, key, len(key), evp_md,
+                                             self._backend.ffi.NULL)
+        assert res != 0
+        return ctx
+
+    def update_ctx(self, ctx, data):
+        res = self._backend.lib.HMAC_Update(ctx, data, len(data))
+        assert res != 0
+
+    def finalize_ctx(self, ctx, digest_size):
+        buf = self._backend.ffi.new("unsigned char[]", digest_size)
+        buflen = self._backend.ffi.new("unsigned int *", digest_size)
+        res = self._backend.lib.HMAC_Final(ctx, buf, buflen)
+        assert res != 0
+        self._backend.lib.HMAC_CTX_cleanup(ctx)
+        return self._backend.ffi.buffer(buf)[:digest_size]
+
+    def copy_ctx(self, ctx):
+        copied_ctx = self._backend.ffi.new("HMAC_CTX *")
+        self._backend.lib.HMAC_CTX_init(copied_ctx)
+        copied_ctx = self._backend.ffi.gc(copied_ctx,
+                                          self._backend.lib.HMAC_CTX_cleanup)
+        res = self._backend.lib.HMAC_CTX_copy(copied_ctx, ctx)
+        assert res != 0
+        return copied_ctx
+
+
 backend = Backend()
diff --git a/cryptography/hazmat/primitives/hmac.py b/cryptography/hazmat/primitives/hmac.py
new file mode 100644
index 00000000..4da0cc3f
--- /dev/null
+++ b/cryptography/hazmat/primitives/hmac.py
@@ -0,0 +1,59 @@
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+# implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from __future__ import absolute_import, division, print_function
+
+import binascii
+
+import six
+
+
+class HMAC(object):
+    def __init__(self, key, msg=None, digestmod=None, ctx=None, backend=None):
+        super(HMAC, self).__init__()
+        if backend is None:
+            from cryptography.hazmat.bindings import _default_backend
+            backend = _default_backend
+
+        if digestmod is None:
+            raise TypeError("digestmod is a required argument")
+
+        self._backend = backend
+        self.digestmod = digestmod
+        self.key = key
+        if ctx is None:
+            self._ctx = self._backend.hmacs.create_ctx(key, self.digestmod)
+        else:
+            self._ctx = ctx
+
+        if msg is not None:
+            self.update(msg)
+
+    def update(self, msg):
+        if isinstance(msg, six.text_type):
+            raise TypeError("Unicode-objects must be encoded before hashing")
+        self._backend.hmacs.update_ctx(self._ctx, msg)
+
+    def copy(self):
+        return self.__class__(self.key, digestmod=self.digestmod,
+                              backend=self._backend, ctx=self._copy_ctx())
+
+    def digest(self):
+        return self._backend.hmacs.finalize_ctx(self._copy_ctx(),
+                                                self.digestmod.digest_size)
+
+    def hexdigest(self):
+        return str(binascii.hexlify(self.digest()).decode("ascii"))
+
+    def _copy_ctx(self):
+        return self._backend.hmacs.copy_ctx(self._ctx)
diff --git a/docs/hazmat/primitives/hmac.rst b/docs/hazmat/primitives/hmac.rst
new file mode 100644
index 00000000..bfbe3255
--- /dev/null
+++ b/docs/hazmat/primitives/hmac.rst
@@ -0,0 +1,52 @@
+.. danger::
+
+    This is a "Hazardous Materials" module. You should **ONLY** use it if
+    you're 100% absolutely sure that you know what you're doing because this
+    module is full of land mines, dragons, and dinosaurs with laser guns.
+
+
+Hash-based Message Authentication Codes
+=======================================
+
+.. testsetup::
+
+    import binascii
+    key = binascii.unhexlify(b"0" * 32)
+
+Hash-based message authentication codes (or HMACs) are a tool for calculating
+message authentication codes using a cryptographic hash function coupled with a
+secret key. You can use an HMAC to verify integrity as well as authenticate a
+message.
+
+.. class:: cryptography.hazmat.primitives.hmac.HMAC(key, msg=None, digestmod=None)
+
+    HMAC objects take a ``key``, a hash class derived from
+    :class:`~cryptography.primitives.hashes.BaseHash`, and optional message.
+    The ``key`` should be randomly generated bytes and is recommended to be
+    equal in length to the ``digest_size`` of the hash function chosen.
+    You must keep the ``key`` secret.
+
+    .. doctest::
+
+        >>> from cryptography.hazmat.primitives import hashes, hmac
+        >>> h = hmac.HMAC(key, digestmod=hashes.SHA256)
+        >>> h.update(b"message to hash")
+        >>> h.hexdigest()
+        '...'
+
+    .. method:: update(msg)
+
+        :param bytes msg: The bytes to hash and authenticate.
+
+    .. method:: copy()
+
+        :return: a new instance of this object with a copied internal state.
+
+    .. method:: digest()
+
+        :return bytes: The message digest as bytes.
+
+    .. method:: hexdigest()
+
+        :return str: The message digest as hex.
+
diff --git a/docs/hazmat/primitives/index.rst b/docs/hazmat/primitives/index.rst
index 6ae769a6..3927f3f0 100644
--- a/docs/hazmat/primitives/index.rst
+++ b/docs/hazmat/primitives/index.rst
@@ -12,4 +12,5 @@ Primitives
     :maxdepth: 1
 
     cryptographic-hashes
+    hmac
     symmetric-encryption
diff --git a/tests/hazmat/primitives/test_hmac.py b/tests/hazmat/primitives/test_hmac.py
new file mode 100644
index 00000000..42726a7c
--- /dev/null
+++ b/tests/hazmat/primitives/test_hmac.py
@@ -0,0 +1,57 @@
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+# implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from __future__ import absolute_import, division, print_function
+
+import pretend
+
+import pytest
+
+import six
+
+from cryptography.hazmat.primitives import hashes, hmac
+
+from .utils import generate_base_hmac_test
+
+
+class TestHMAC(object):
+    test_copy = generate_base_hmac_test(
+        hashes.MD5,
+        only_if=lambda backend: backend.hashes.supported(hashes.MD5),
+        skip_message="Does not support MD5",
+    )
+
+    def test_hmac_reject_unicode(self, backend):
+        h = hmac.HMAC(key=b"mykey", digestmod=hashes.SHA1, backend=backend)
+        with pytest.raises(TypeError):
+            h.update(six.u("\u00FC"))
+
+    def test_base_hash_hexdigest_string_type(self, backend):
+        h = hmac.HMAC(key=b"mykey", digestmod=hashes.SHA1, backend=backend,
+                      msg=b"")
+        assert isinstance(h.hexdigest(), str)
+
+    def test_hmac_no_digestmod(self):
+        with pytest.raises(TypeError):
+            hmac.HMAC(key=b"shortkey")
+
+
+class TestCopyHMAC(object):
+    def test_copy_backend_object(self):
+        pretend_hmac = pretend.stub(copy_ctx=lambda a: True)
+        pretend_backend = pretend.stub(hmacs=pretend_hmac)
+        pretend_ctx = pretend.stub()
+        h = hmac.HMAC(b"key", digestmod=hashes.SHA1, backend=pretend_backend,
+                      ctx=pretend_ctx)
+        assert h._backend is pretend_backend
+        assert h.copy()._backend is pretend_backend
diff --git a/tests/hazmat/primitives/test_hmac_vectors.py b/tests/hazmat/primitives/test_hmac_vectors.py
new file mode 100644
index 00000000..81fe4d3e
--- /dev/null
+++ b/tests/hazmat/primitives/test_hmac_vectors.py
@@ -0,0 +1,112 @@
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+# implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from __future__ import absolute_import, division, print_function
+
+import os
+
+from cryptography.hazmat.primitives import hashes
+
+from .utils import generate_hmac_test
+from ...utils import load_hash_vectors_from_file
+
+
+class TestHMAC_MD5(object):
+    test_hmac_md5 = generate_hmac_test(
+        load_hash_vectors_from_file,
+        os.path.join("RFC", "HMAC"),
+        [
+            "rfc-2202-md5.txt",
+        ],
+        hashes.MD5,
+        only_if=lambda backend: backend.hashes.supported(hashes.MD5),
+        skip_message="Does not support MD5",
+    )
+
+
+class TestHMAC_SHA1(object):
+    test_hmac_sha1 = generate_hmac_test(
+        load_hash_vectors_from_file,
+        os.path.join("RFC", "HMAC"),
+        [
+            "rfc-2202-sha1.txt",
+        ],
+        hashes.SHA1,
+        only_if=lambda backend: backend.hashes.supported(hashes.SHA1),
+        skip_message="Does not support SHA1",
+    )
+
+
+class TestHMAC_SHA224(object):
+    test_hmac_sha224 = generate_hmac_test(
+        load_hash_vectors_from_file,
+        os.path.join("RFC", "HMAC"),
+        [
+            "rfc-4231-sha224.txt",
+        ],
+        hashes.SHA224,
+        only_if=lambda backend: backend.hashes.supported(hashes.SHA224),
+        skip_message="Does not support SHA224",
+    )
+
+
+class TestHMAC_SHA256(object):
+    test_hmac_sha256 = generate_hmac_test(
+        load_hash_vectors_from_file,
+        os.path.join("RFC", "HMAC"),
+        [
+            "rfc-4231-sha256.txt",
+        ],
+        hashes.SHA256,
+        only_if=lambda backend: backend.hashes.supported(hashes.SHA256),
+        skip_message="Does not support SHA256",
+    )
+
+
+class TestHMAC_SHA384(object):
+    test_hmac_sha384 = generate_hmac_test(
+        load_hash_vectors_from_file,
+        os.path.join("RFC", "HMAC"),
+        [
+            "rfc-4231-sha384.txt",
+        ],
+        hashes.SHA384,
+        only_if=lambda backend: backend.hashes.supported(hashes.SHA384),
+        skip_message="Does not support SHA384",
+    )
+
+
+class TestHMAC_SHA512(object):
+    test_hmac_sha512 = generate_hmac_test(
+        load_hash_vectors_from_file,
+        os.path.join("RFC", "HMAC"),
+        [
+            "rfc-4231-sha512.txt",
+        ],
+        hashes.SHA512,
+        only_if=lambda backend: backend.hashes.supported(hashes.SHA512),
+        skip_message="Does not support SHA512",
+    )
+
+
+class TestHMAC_RIPEMD160(object):
+    test_hmac_ripemd160 = generate_hmac_test(
+        load_hash_vectors_from_file,
+        os.path.join("RFC", "HMAC"),
+        [
+            "rfc-2286-ripemd160.txt",
+        ],
+        hashes.RIPEMD160,
+        only_if=lambda backend: backend.hashes.supported(hashes.RIPEMD160),
+        skip_message="Does not support RIPEMD160",
+    )
diff --git a/tests/hazmat/primitives/test_utils.py b/tests/hazmat/primitives/test_utils.py
index b7fa3d35..d7247e67 100644
--- a/tests/hazmat/primitives/test_utils.py
+++ b/tests/hazmat/primitives/test_utils.py
@@ -1,7 +1,8 @@
 import pytest
 
 from .utils import (
-    base_hash_test, encrypt_test, hash_test, long_string_hash_test
+    base_hash_test, encrypt_test, hash_test, long_string_hash_test,
+    base_hmac_test, hmac_test
 )
 
 
@@ -47,3 +48,25 @@ class TestLongHashTest(object):
                 skip_message="message!"
             )
         assert exc_info.value.args[0] == "message!"
+
+
+class TestHMACTest(object):
+    def test_skips_if_only_if_returns_false(self):
+        with pytest.raises(pytest.skip.Exception) as exc_info:
+            hmac_test(
+                None, None, None,
+                only_if=lambda backend: False,
+                skip_message="message!"
+            )
+        assert exc_info.value.args[0] == "message!"
+
+
+class TestBaseHMACTest(object):
+    def test_skips_if_only_if_returns_false(self):
+        with pytest.raises(pytest.skip.Exception) as exc_info:
+            base_hmac_test(
+                None, None,
+                only_if=lambda backend: False,
+                skip_message="message!"
+            )
+        assert exc_info.value.args[0] == "message!"
diff --git a/tests/hazmat/primitives/utils.py b/tests/hazmat/primitives/utils.py
index fabdca01..c51fef52 100644
--- a/tests/hazmat/primitives/utils.py
+++ b/tests/hazmat/primitives/utils.py
@@ -4,6 +4,7 @@ import os
 import pytest
 
 from cryptography.hazmat.bindings import _ALL_BACKENDS
+from cryptography.hazmat.primitives import hmac
 from cryptography.hazmat.primitives.block import BlockCipher
 
 
@@ -92,11 +93,11 @@ def generate_base_hash_test(hash_cls, digest_size, block_size,
     return test_base_hash
 
 
-def base_hash_test(backend, hash_cls, digest_size, block_size, only_if,
+def base_hash_test(backend, digestmod, digest_size, block_size, only_if,
                    skip_message):
     if only_if is not None and not only_if(backend):
         pytest.skip(skip_message)
-    m = hash_cls(backend=backend)
+    m = digestmod(backend=backend)
     assert m.digest_size == digest_size
     assert m.block_size == block_size
     m_copy = m.copy()
@@ -125,3 +126,57 @@ def long_string_hash_test(backend, hash_factory, md, only_if, skip_message):
     m = hash_factory(backend=backend)
     m.update(b"a" * 1000000)
     assert m.hexdigest() == md.lower()
+
+
+def generate_hmac_test(param_loader, path, file_names, digestmod,
+                       only_if=None, skip_message=None):
+    def test_hmac(self):
+        for backend in _ALL_BACKENDS:
+            for file_name in file_names:
+                for params in param_loader(os.path.join(path, file_name)):
+                    yield (
+                        hmac_test,
+                        backend,
+                        digestmod,
+                        params,
+                        only_if,
+                        skip_message
+                    )
+    return test_hmac
+
+
+def hmac_test(backend, digestmod, params, only_if, skip_message):
+    if only_if is not None and not only_if(backend):
+        pytest.skip(skip_message)
+    msg = params[0]
+    md = params[1]
+    key = params[2]
+    h = hmac.HMAC(binascii.unhexlify(key), digestmod=digestmod)
+    h.update(binascii.unhexlify(msg))
+    assert h.hexdigest() == md
+    digest = hmac.HMAC(binascii.unhexlify(key), digestmod=digestmod,
+                       msg=binascii.unhexlify(msg)).hexdigest()
+    assert digest == md
+
+
+def generate_base_hmac_test(hash_cls, only_if=None, skip_message=None):
+    def test_base_hmac(self):
+        for backend in _ALL_BACKENDS:
+            yield (
+                base_hmac_test,
+                backend,
+                hash_cls,
+                only_if,
+                skip_message,
+            )
+    return test_base_hmac
+
+
+def base_hmac_test(backend, digestmod, only_if, skip_message):
+    if only_if is not None and not only_if(backend):
+        pytest.skip(skip_message)
+    key = b"ab"
+    h = hmac.HMAC(binascii.unhexlify(key), digestmod=digestmod)
+    h_copy = h.copy()
+    assert h != h_copy
+    assert h._ctx != h_copy._ctx
diff --git a/tests/test_utils.py b/tests/test_utils.py
index f96cf004..db9ac085 100644
--- a/tests/test_utils.py
+++ b/tests/test_utils.py
@@ -411,6 +411,22 @@ def test_load_hash_vectors():
     ]
 
 
+def test_load_hmac_vectors():
+    vector_data = textwrap.dedent("""
+Len = 224
+# "Jefe"
+Key = 4a656665
+# "what do ya want for nothing?"
+Msg = 7768617420646f2079612077616e7420666f72206e6f7468696e673f
+MD = 750c783e6ab0b503eaa86e310a5db738
+    """).splitlines()
+    assert load_hash_vectors(vector_data) == [
+        (b"7768617420646f2079612077616e7420666f72206e6f7468696e673f",
+         "750c783e6ab0b503eaa86e310a5db738",
+         b"4a656665"),
+    ]
+
+
 def test_load_hash_vectors_bad_data():
     vector_data = textwrap.dedent("""
         # http://tools.ietf.org/html/rfc1321
diff --git a/tests/utils.py b/tests/utils.py
index 9d01746a..ad676c04 100644
--- a/tests/utils.py
+++ b/tests/utils.py
@@ -127,6 +127,9 @@ def load_openssl_vectors(vector_data):
 
 def load_hash_vectors(vector_data):
     vectors = []
+    key = None
+    msg = None
+    md = None
 
     for line in vector_data:
         line = line.strip()
@@ -136,6 +139,11 @@ def load_hash_vectors(vector_data):
 
         if line.startswith("Len"):
             length = int(line.split(" = ")[1])
+        elif line.startswith("Key"):
+            """
+            HMAC vectors contain a key attribute. Hash vectors do not.
+            """
+            key = line.split(" = ")[1].encode("ascii")
         elif line.startswith("Msg"):
             """
             In the NIST vectors they have chosen to represent an empty
@@ -145,8 +153,16 @@ def load_hash_vectors(vector_data):
             msg = line.split(" = ")[1].encode("ascii") if length > 0 else b""
         elif line.startswith("MD"):
             md = line.split(" = ")[1]
-            # after MD is found the Msg+MD tuple is complete
-            vectors.append((msg, md))
+            # after MD is found the Msg+MD (+ potential key) tuple is complete
+            if key is not None:
+                vectors.append((msg, md, key))
+                key = None
+                msg = None
+                md = None
+            else:
+                vectors.append((msg, md))
+                msg = None
+                md = None
         else:
             raise ValueError("Unknown line in hash vector")
     return vectors