diff options
Diffstat (limited to 'cryptography/hazmat')
| -rw-r--r-- | cryptography/hazmat/backends/openssl/backend.py | 67 |
1 files changed, 51 insertions, 16 deletions
diff --git a/cryptography/hazmat/backends/openssl/backend.py b/cryptography/hazmat/backends/openssl/backend.py index 1495e75c..d7c0f882 100644 --- a/cryptography/hazmat/backends/openssl/backend.py +++ b/cryptography/hazmat/backends/openssl/backend.py @@ -15,6 +15,7 @@ from __future__ import absolute_import, division, print_function import collections import itertools +import math import six @@ -695,11 +696,24 @@ class _HMACContext(object): return self._backend._ffi.buffer(buf)[:outlen[0]] +def _get_rsa_pss_salt_length(mgf, key_size, digest_size): + if mgf._salt_length is MGF1.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 + else: + return mgf._salt_length + + @utils.register_interface(interfaces.AsymmetricSignatureContext) class _RSASignatureContext(object): def __init__(self, backend, private_key, padding, algorithm): self._backend = backend self._private_key = private_key + key_size_bytes = int(math.ceil(private_key.key_size / 8.0)) + if not isinstance(padding, interfaces.AsymmetricPadding): raise TypeError( "Expected provider of interfaces.AsymmetricPadding") @@ -716,6 +730,11 @@ class _RSASignatureContext(object): "Only MGF1 is supported by this backend" ) + # Size of key in bytes - 2 is the maximum + # PSS signature length (salt length is checked later) + if key_size_bytes - algorithm.digest_size - 2 < 0: + raise ValueError("Digest too large for key size.") + if not self._backend.mgf1_hash_supported(padding._mgf._algorithm): raise UnsupportedHash( "When OpenSSL is older than 1.0.1 then only SHA1 is " @@ -773,8 +792,15 @@ class _RSASignatureContext(object): assert res > 0 if isinstance(self._padding, PSS): res = self._backend._lib.EVP_PKEY_CTX_set_rsa_pss_saltlen( - pkey_ctx, self._get_salt_length()) + pkey_ctx, + _get_rsa_pss_salt_length( + self._padding._mgf, + self._private_key.key_size, + self._hash_ctx.algorithm.digest_size + ) + ) assert res > 0 + if self._backend._lib.Cryptography_HAS_MGF1_MD: # MGF1 MD is configurable in OpenSSL 1.0.1+ mgf1_md = self._backend._lib.EVP_get_digestbyname( @@ -834,7 +860,11 @@ class _RSASignatureContext(object): padded, data_to_sign, evp_md, - self._get_salt_length() + _get_rsa_pss_salt_length( + self._padding._mgf, + self._private_key.key_size, + len(data_to_sign) + ) ) if res != 1: errors = self._backend._consume_errors() @@ -854,12 +884,6 @@ class _RSASignatureContext(object): assert sig_len != -1 return self._backend._ffi.buffer(sig_buf)[:sig_len] - def _get_salt_length(self): - if self._padding._mgf._salt_length is MGF1.MAX_LENGTH: - return -2 - else: - return self._padding._mgf._salt_length - @utils.register_interface(interfaces.AsymmetricVerificationContext) class _RSAVerificationContext(object): @@ -867,6 +891,8 @@ class _RSAVerificationContext(object): self._backend = backend self._public_key = public_key self._signature = signature + key_size_bytes = int(math.ceil(public_key.key_size / 8.0)) + if not isinstance(padding, interfaces.AsymmetricPadding): raise TypeError( "Expected provider of interfaces.AsymmetricPadding") @@ -883,6 +909,11 @@ class _RSAVerificationContext(object): "Only MGF1 is supported by this backend" ) + # Size of key in bytes - 2 is the maximum + # PSS signature length (salt length is checked later) + if key_size_bytes - algorithm.digest_size - 2 < 0: + raise ValueError("Digest too large for key size.") + if not self._backend.mgf1_hash_supported(padding._mgf._algorithm): raise UnsupportedHash( "When OpenSSL is older than 1.0.1 then only SHA1 is " @@ -936,7 +967,13 @@ class _RSAVerificationContext(object): assert res > 0 if isinstance(self._padding, PSS): res = self._backend._lib.EVP_PKEY_CTX_set_rsa_pss_saltlen( - pkey_ctx, self._get_salt_length()) + pkey_ctx, + _get_rsa_pss_salt_length( + self._padding._mgf, + self._public_key.key_size, + self._hash_ctx.algorithm.digest_size + ) + ) assert res > 0 if self._backend._lib.Cryptography_HAS_MGF1_MD: # MGF1 MD is configurable in OpenSSL 1.0.1+ @@ -1011,18 +1048,16 @@ class _RSAVerificationContext(object): data_to_verify, evp_md, buf, - self._get_salt_length() + _get_rsa_pss_salt_length( + self._padding._mgf, + self._public_key.key_size, + len(data_to_verify) + ) ) if res != 1: errors = self._backend._consume_errors() assert errors raise InvalidSignature - def _get_salt_length(self): - if self._padding._mgf._salt_length is MGF1.MAX_LENGTH: - return -2 - else: - return self._padding._mgf._salt_length - backend = Backend() |