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openSUSE:Leap:15.3:Update
python-cryptography.27135
disallow_implicit_tag_truncation.patch
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File disallow_implicit_tag_truncation.patch of Package python-cryptography.27135
From 688e0f673bfbf43fa898994326c6877f00ab19ef Mon Sep 17 00:00:00 2001 From: Paul Kehrer <paul.l.kehrer@gmail.com> Date: Tue, 17 Jul 2018 10:47:57 +0800 Subject: [PATCH] disallow implicit tag truncation with finalize_with_tag --- CHANGELOG.rst | 5 +++++ docs/hazmat/primitives/symmetric-encryption.rst | 1 + .../hazmat/backends/openssl/ciphers.py | 5 +++++ .../hazmat/primitives/ciphers/modes.py | 1 + tests/hazmat/primitives/test_aes.py | 16 ++++++++++++++++ 5 files changed, 28 insertions(+) --- a/docs/hazmat/primitives/symmetric-encryption.rst +++ b/docs/hazmat/primitives/symmetric-encryption.rst @@ -670,6 +670,7 @@ Interfaces :raises ValueError: This is raised when the data provided isn't a multiple of the algorithm's block size, if ``min_tag_length`` is less than 4, or if ``len(tag) < min_tag_length``. + ``min_tag_length`` is an argument to the ``GCM`` constructor. :raises NotImplementedError: This is raised if the version of the OpenSSL backend used is 1.0.1 or earlier. --- a/src/cryptography/hazmat/backends/openssl/ciphers.py +++ b/src/cryptography/hazmat/backends/openssl/ciphers.py @@ -202,6 +202,11 @@ class _CipherContext(object): "finalize_with_tag requires OpenSSL >= 1.0.2. To use this " "method please update OpenSSL" ) + if len(tag) < self._mode._min_tag_length: + raise ValueError( + "Authentication tag must be {0} bytes or longer.".format( + self._mode._min_tag_length) + ) res = self._backend._lib.EVP_CIPHER_CTX_ctrl( self._ctx, self._backend._lib.EVP_CTRL_AEAD_SET_TAG, len(tag), tag --- a/src/cryptography/hazmat/primitives/ciphers/modes.py +++ b/src/cryptography/hazmat/primitives/ciphers/modes.py @@ -220,6 +220,7 @@ class GCM(object): min_tag_length) ) self._tag = tag + self._min_tag_length = min_tag_length tag = utils.read_only_property("_tag") initialization_vector = utils.read_only_property("_initialization_vector") --- a/tests/hazmat/primitives/test_aes.py +++ b/tests/hazmat/primitives/test_aes.py @@ -439,3 +439,19 @@ class TestAESModeGCM(object): decryptor.finalize() else: decryptor.finalize_with_tag(tag) + + @pytest.mark.supported( + only_if=lambda backend: ( + not backend._lib.CRYPTOGRAPHY_OPENSSL_LESS_THAN_102 or + backend._lib.CRYPTOGRAPHY_IS_LIBRESSL + ), + skip_message="Not supported on OpenSSL 1.0.1", + ) + def test_gcm_tag_decrypt_finalize_tag_length(self, backend): + decryptor = base.Cipher( + algorithms.AES(b"0" * 16), + modes.GCM(b"0" * 12), + backend=backend + ).decryptor() + with pytest.raises(ValueError): + decryptor.finalize_with_tag(b"tagtooshort")
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