bpo-40645: Implement HMAC in C (GH-20129)

The internal module ``_hashlib`` wraps and exposes OpenSSL's HMAC API. The new code will be used in Python 3.10 after the internal implementation details of the pure Python HMAC module are no longer part of the public API. The code is based on a patch by Petr Viktorin for RHEL and Python 3.6. Co-Authored-By: Petr Viktorin <encukou@gmail.com>

Author: tiran

Lib/test/test_hmac.py

@@ -8,6 +8,13 @@
 
 from test.support import hashlib_helper
 
+try:
+ from _hashlib import HMAC as C_HMAC
+ from _hashlib import hmac_new as c_hmac_new
+except ImportError:
+ C_HMAC = None
+ c_hmac_new = None
+
 
 def ignore_warning(func):
  @functools.wraps(func)
@@ -21,34 +28,91 @@ def wrapper(*args, **kwargs):
 
 class TestVectorsTestCase(unittest.TestCase):
 
- @hashlib_helper.requires_hashdigest('md5', openssl=True)
- def test_md5_vectors(self):
- # Test the HMAC module against test vectors from the RFC.
+ def asssert_hmac(
+ self, key, data, digest, hashfunc, hashname, digest_size, block_size
+ ):
+ h = hmac.HMAC(key, data, digestmod=hashfunc)
+ self.assertEqual(h.hexdigest().upper(), digest.upper())
+ self.assertEqual(h.digest(), binascii.unhexlify(digest))
+ self.assertEqual(h.name, f"hmac-{hashname}")
+ self.assertEqual(h.digest_size, digest_size)
+ self.assertEqual(h.block_size, block_size)
+
+ h = hmac.HMAC(key, data, digestmod=hashname)
+ self.assertEqual(h.hexdigest().upper(), digest.upper())
+ self.assertEqual(h.digest(), binascii.unhexlify(digest))
+ self.assertEqual(h.name, f"hmac-{hashname}")
+ self.assertEqual(h.digest_size, digest_size)
+ self.assertEqual(h.block_size, block_size)
+
+ h = hmac.HMAC(key, digestmod=hashname)
+ h2 = h.copy()
+ h2.update(b"test update")
+ h.update(data)
+ self.assertEqual(h.hexdigest().upper(), digest.upper())
+
+ h = hmac.new(key, data, digestmod=hashname)
+ self.assertEqual(h.hexdigest().upper(), digest.upper())
+ self.assertEqual(h.digest(), binascii.unhexlify(digest))
+ self.assertEqual(h.name, f"hmac-{hashname}")
+ self.assertEqual(h.digest_size, digest_size)
+ self.assertEqual(h.block_size, block_size)
+
+ h = hmac.new(key, None, digestmod=hashname)
+ h.update(data)
+ self.assertEqual(h.hexdigest().upper(), digest.upper())
+
+ h = hmac.new(key, digestmod=hashname)
+ h.update(data)
+ self.assertEqual(h.hexdigest().upper(), digest.upper())
+
+ h = hmac.new(key, data, digestmod=hashfunc)
+ self.assertEqual(h.hexdigest().upper(), digest.upper())
+
+ self.assertEqual(
+ hmac.digest(key, data, digest=hashname),
+ binascii.unhexlify(digest)
+ )
+ self.assertEqual(
+ hmac.digest(key, data, digest=hashfunc),
+ binascii.unhexlify(digest)
+ )
+ with unittest.mock.patch('hmac._openssl_md_meths', {}):
+ self.assertEqual(
+ hmac.digest(key, data, digest=hashname),
+ binascii.unhexlify(digest)
+ )
+ self.assertEqual(
+ hmac.digest(key, data, digest=hashfunc),
+ binascii.unhexlify(digest)
+ )
 
- def md5test(key, data, digest):
- h = hmac.HMAC(key, data, digestmod=hashlib.md5)
+ if c_hmac_new is not None:
+ h = c_hmac_new(key, data, digestmod=hashname)
  self.assertEqual(h.hexdigest().upper(), digest.upper())
  self.assertEqual(h.digest(), binascii.unhexlify(digest))
- self.assertEqual(h.name, "hmac-md5")
- self.assertEqual(h.digest_size, 16)
- self.assertEqual(h.block_size, 64)
+ self.assertEqual(h.name, f"hmac-{hashname}")
+ self.assertEqual(h.digest_size, digest_size)
+ self.assertEqual(h.block_size, block_size)
 
- h = hmac.HMAC(key, data, digestmod='md5')
+ h = c_hmac_new(key, digestmod=hashname)
+ h2 = h.copy()
+ h2.update(b"test update")
+ h.update(data)
  self.assertEqual(h.hexdigest().upper(), digest.upper())
- self.assertEqual(h.digest(), binascii.unhexlify(digest))
- self.assertEqual(h.name, "hmac-md5")
- self.assertEqual(h.digest_size, 16)
- self.assertEqual(h.block_size, 64)
 
- self.assertEqual(
- hmac.digest(key, data, digest='md5'),
- binascii.unhexlify(digest)
+ @hashlib_helper.requires_hashdigest('md5', openssl=True)
+ def test_md5_vectors(self):
+ # Test the HMAC module against test vectors from the RFC.
+
+ def md5test(key, data, digest):
+ self.asssert_hmac(
+ key, data, digest,
+ hashfunc=hashlib.md5,
+ hashname="md5",
+ digest_size=16,
+ block_size=64
  )
- with unittest.mock.patch('hmac._openssl_md_meths', {}):
- self.assertEqual(
- hmac.digest(key, data, digest='md5'),
- binascii.unhexlify(digest)
- )
 
  md5test(b"\x0b" * 16,
  b"Hi There",
@@ -82,26 +146,14 @@ def md5test(key, data, digest):
  @hashlib_helper.requires_hashdigest('sha1', openssl=True)
  def test_sha_vectors(self):
  def shatest(key, data, digest):
- h = hmac.HMAC(key, data, digestmod=hashlib.sha1)
- self.assertEqual(h.hexdigest().upper(), digest.upper())
- self.assertEqual(h.digest(), binascii.unhexlify(digest))
- self.assertEqual(h.name, "hmac-sha1")
- self.assertEqual(h.digest_size, 20)
- self.assertEqual(h.block_size, 64)
-
- h = hmac.HMAC(key, data, digestmod='sha1')
- self.assertEqual(h.hexdigest().upper(), digest.upper())
- self.assertEqual(h.digest(), binascii.unhexlify(digest))
- self.assertEqual(h.name, "hmac-sha1")
- self.assertEqual(h.digest_size, 20)
- self.assertEqual(h.block_size, 64)
-
- self.assertEqual(
- hmac.digest(key, data, digest='sha1'),
- binascii.unhexlify(digest)
+ self.asssert_hmac(
+ key, data, digest,
+ hashfunc=hashlib.sha1,
+ hashname="sha1",
+ digest_size=20,
+ block_size=64
  )
 
-
  shatest(b"\x0b" * 20,
  b"Hi There",
  "b617318655057264e28bc0b6fb378c8ef146be00")
@@ -133,37 +185,15 @@ def shatest(key, data, digest):
 
  def _rfc4231_test_cases(self, hashfunc, hash_name, digest_size, block_size):
  def hmactest(key, data, hexdigests):
- hmac_name = "hmac-" + hash_name
- h = hmac.HMAC(key, data, digestmod=hashfunc)
- self.assertEqual(h.hexdigest().lower(), hexdigests[hashfunc])
- self.assertEqual(h.name, hmac_name)
- self.assertEqual(h.digest_size, digest_size)
- self.assertEqual(h.block_size, block_size)
-
- h = hmac.HMAC(key, data, digestmod=hash_name)
- self.assertEqual(h.hexdigest().lower(), hexdigests[hashfunc])
- self.assertEqual(h.name, hmac_name)
- self.assertEqual(h.digest_size, digest_size)
- self.assertEqual(h.block_size, block_size)
-
- self.assertEqual(
- hmac.digest(key, data, digest=hashfunc),
- binascii.unhexlify(hexdigests[hashfunc])
+ digest = hexdigests[hashfunc]
+
+ self.asssert_hmac(
+ key, data, digest,
+ hashfunc=hashfunc,
+ hashname=hash_name,
+ digest_size=digest_size,
+ block_size=block_size
  )
- self.assertEqual(
- hmac.digest(key, data, digest=hash_name),
- binascii.unhexlify(hexdigests[hashfunc])
- )
-
- with unittest.mock.patch('hmac._openssl_md_meths', {}):
- self.assertEqual(
- hmac.digest(key, data, digest=hashfunc),
- binascii.unhexlify(hexdigests[hashfunc])
- )
- self.assertEqual(
- hmac.digest(key, data, digest=hash_name),
- binascii.unhexlify(hexdigests[hashfunc])
- )
 
  # 4.2. Test Case 1
  hmactest(key = b'\x0b'*20,
@@ -385,6 +415,14 @@ def test_withmodule(self):
  except Exception:
  self.fail("Constructor call with hashlib.sha256 raised exception.")
 
+ @unittest.skipUnless(C_HMAC is not None, 'need _hashlib')
+ def test_internal_types(self):
+ # internal types like _hashlib.C_HMAC are not constructable
+ with self.assertRaisesRegex(
+ TypeError, "cannot create 'HMAC' instance"
+ ):
+ C_HMAC()
+
 
 class SanityTestCase(unittest.TestCase):
 
@@ -395,9 +433,9 @@ def test_exercise_all_methods(self):
  try:
  h = hmac.HMAC(b"my secret key", digestmod="sha256")
  h.update(b"compute the hash of this text!")
- dig = h.digest()
- dig = h.hexdigest()
- h2 = h.copy()
+ h.digest()
+ h.hexdigest()
+ h.copy()
  except Exception:
  self.fail("Exception raised during normal usage of HMAC class.")
 
@@ -450,6 +488,21 @@ def test_equality(self):
  self.assertEqual(h1.hexdigest(), h2.hexdigest(),
  "Hexdigest of copy doesn't match original hexdigest.")
 
+ @hashlib_helper.requires_hashdigest('sha256')
+ def test_equality_new(self):
+ # Testing if the copy has the same digests with hmac.new().
+ h1 = hmac.new(b"key", digestmod="sha256")
+ h1.update(b"some random text")
+ h2 = h1.copy()
+ self.assertTrue(
+ id(h1) != id(h2), "No real copy of the HMAC instance."
+ )
+ self.assertEqual(h1.digest(), h2.digest(),
+ "Digest of copy doesn't match original digest.")
+ self.assertEqual(h1.hexdigest(), h2.hexdigest(),
+ "Hexdigest of copy doesn't match original hexdigest.")
+
+
 class CompareDigestTestCase(unittest.TestCase):
 
  def test_compare_digest(self):

Misc/NEWS.d/next/Library/2020-05-16-17-05-02.bpo-40645.wYSkjT.rst

@@ -0,0 +1 @@
+The internal module ``_hashlib`` wraps and exposes OpenSSL's HMAC API. The new code will be used in Python 3.10 after the internal implementation details of the pure Python HMAC module are no longer part of the public API.