diff options
| -rw-r--r-- | CHANGELOG.rst | 3 | ||||
| -rw-r--r-- | docs/hazmat/primitives/asymmetric/rsa.rst | 21 | ||||
| -rw-r--r-- | src/cryptography/hazmat/backends/openssl/rsa.py | 18 | ||||
| -rw-r--r-- | src/cryptography/hazmat/primitives/asymmetric/padding.py | 12 | ||||
| -rw-r--r-- | tests/hazmat/primitives/test_rsa.py | 4 |
5 files changed, 43 insertions, 15 deletions
diff --git a/CHANGELOG.rst b/CHANGELOG.rst index 65dfebe1..28530853 100644 --- a/CHANGELOG.rst +++ b/CHANGELOG.rst @@ -6,6 +6,9 @@ Changelog .. note:: This version is not yet released and is under active development. +* Added + :func:`~cryptography.hazmat.primitives.asymmetric.padding.calculate_max_pss_salt_length`. + 1.4 - 2016-06-04 ~~~~~~~~~~~~~~~~ diff --git a/docs/hazmat/primitives/asymmetric/rsa.rst b/docs/hazmat/primitives/asymmetric/rsa.rst index 369f857a..93214449 100644 --- a/docs/hazmat/primitives/asymmetric/rsa.rst +++ b/docs/hazmat/primitives/asymmetric/rsa.rst @@ -330,6 +330,20 @@ Padding :class:`OAEP` should be preferred for encryption and :class:`PSS` should be preferred for signatures. + +.. function:: calculate_max_pss_salt_length(key, hash_algorithm) + + .. versionadded:: 1.5 + + :param key: An RSA public or private key. + :param hash_algorithm: A + :class:`cryptography.hazmat.primitives.hashes.HashAlgorithm`. + :returns int: The computed salt length. + + Computes the length of the salt that :class:`PSS` will use if + :data:`PSS.MAX_LENGTH` is used. + + Mask generation functions ------------------------- @@ -341,11 +355,10 @@ Mask generation functions Removed the deprecated ``salt_length`` parameter. MGF1 (Mask Generation Function 1) is used as the mask generation function - in :class:`PSS` padding. It takes a hash algorithm and a salt length. + in :class:`PSS` and :class:`OAEP` padding. It takes a hash algorithm. - :param algorithm: An instance of a - :class:`~cryptography.hazmat.primitives.hashes.HashAlgorithm` - provider. + :param algorithm: An instance of + :class:`~cryptography.hazmat.primitives.hashes.HashAlgorithm`. Numbers ~~~~~~~ diff --git a/src/cryptography/hazmat/backends/openssl/rsa.py b/src/cryptography/hazmat/backends/openssl/rsa.py index 63ba6273..a85f7da1 100644 --- a/src/cryptography/hazmat/backends/openssl/rsa.py +++ b/src/cryptography/hazmat/backends/openssl/rsa.py @@ -15,22 +15,18 @@ from cryptography.hazmat.primitives.asymmetric import ( AsymmetricSignatureContext, AsymmetricVerificationContext, rsa ) from cryptography.hazmat.primitives.asymmetric.padding import ( - AsymmetricPadding, MGF1, OAEP, PKCS1v15, PSS + AsymmetricPadding, MGF1, OAEP, PKCS1v15, PSS, calculate_max_pss_salt_length ) from cryptography.hazmat.primitives.asymmetric.rsa import ( RSAPrivateKeyWithSerialization, RSAPublicKeyWithSerialization ) -def _get_rsa_pss_salt_length(pss, key_size, digest_size): +def _get_rsa_pss_salt_length(pss, key, hash_algorithm): salt = pss._salt_length if salt is MGF1.MAX_LENGTH or salt is PSS.MAX_LENGTH: - # bit length - 1 per RFC 3447 - emlen = int(math.ceil((key_size - 1) / 8.0)) - salt_length = emlen - digest_size - 2 - assert salt_length >= 0 - return salt_length + return calculate_max_pss_salt_length(key, hash_algorithm) else: return salt @@ -220,8 +216,8 @@ class _RSASignatureContext(object): pkey_ctx, _get_rsa_pss_salt_length( self._padding, - self._private_key.key_size, - self._hash_ctx.algorithm.digest_size + self._private_key, + self._hash_ctx.algorithm, ) ) self._backend.openssl_assert(res > 0) @@ -348,8 +344,8 @@ class _RSAVerificationContext(object): pkey_ctx, _get_rsa_pss_salt_length( self._padding, - self._public_key.key_size, - self._hash_ctx.algorithm.digest_size + self._public_key, + self._hash_ctx.algorithm, ) ) self._backend.openssl_assert(res > 0) diff --git a/src/cryptography/hazmat/primitives/asymmetric/padding.py b/src/cryptography/hazmat/primitives/asymmetric/padding.py index c796d8e4..a37c3f90 100644 --- a/src/cryptography/hazmat/primitives/asymmetric/padding.py +++ b/src/cryptography/hazmat/primitives/asymmetric/padding.py @@ -5,11 +5,13 @@ from __future__ import absolute_import, division, print_function import abc +import math import six from cryptography import utils from cryptography.hazmat.primitives import hashes +from cryptography.hazmat.primitives.asymmetric import rsa @six.add_metaclass(abc.ABCMeta) @@ -65,3 +67,13 @@ class MGF1(object): raise TypeError("Expected instance of hashes.HashAlgorithm.") self._algorithm = algorithm + + +def calculate_max_pss_salt_length(key, hash_algorithm): + if not isinstance(key, (rsa.RSAPrivateKey, rsa.RSAPublicKey)): + raise TypeError("key must be an RSA public or private key") + # bit length - 1 per RFC 3447 + emlen = int(math.ceil((key.key_size - 1) / 8.0)) + salt_length = emlen - hash_algorithm.digest_size - 2 + assert salt_length >= 0 + return salt_length diff --git a/tests/hazmat/primitives/test_rsa.py b/tests/hazmat/primitives/test_rsa.py index 9f3008e3..e4e43780 100644 --- a/tests/hazmat/primitives/test_rsa.py +++ b/tests/hazmat/primitives/test_rsa.py @@ -1081,6 +1081,10 @@ class TestRSAPKCS1Verification(object): class TestPSS(object): + def test_calculate_max_pss_salt_length(self): + with pytest.raises(TypeError): + padding.calculate_max_pss_salt_length(object(), hashes.SHA256()) + def test_invalid_salt_length_not_integer(self): with pytest.raises(TypeError): padding.PSS( |