python-cryptography: fix CVE-2018-10903

Signed-off-by: Josef Schlehofer <pepe.schlehofer@gmail.com>

diff --git a/lang/python/python-cryptography/patches/004-fix-CVE-2018-10903.patch b/lang/python/python-cryptography/patches/004-fix-CVE-2018-10903.patch
new file mode 100644 (file)
index 0000000..5608469
--- /dev/null
+++ b/lang/python/python-cryptography/patches/004-fix-CVE-2018-10903.patch
@@ -0,0 +1,78 @@
+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
+
+Pull request: https://github.com/pyca/cryptography/pull/4342
+
+---
+ 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(+)
+
+diff --git a/docs/hazmat/primitives/symmetric-encryption.rst b/docs/hazmat/primitives/symmetric-encryption.rst
+index 5ebcca754d..5b60009027 100644
+--- 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.
+
+diff --git a/src/cryptography/hazmat/backends/openssl/ciphers.py b/src/cryptography/hazmat/backends/openssl/ciphers.py
+index 462ffea251..e0ee06ee26 100644
+--- a/src/cryptography/hazmat/backends/openssl/ciphers.py
++++ b/src/cryptography/hazmat/backends/openssl/ciphers.py
+@@ -199,6 +199,11 @@ def finalize_with_tag(self, tag):
+                 "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
+diff --git a/src/cryptography/hazmat/primitives/ciphers/modes.py b/src/cryptography/hazmat/primitives/ciphers/modes.py
+index 598dfaa4a4..543015fef7 100644
+--- a/src/cryptography/hazmat/primitives/ciphers/modes.py
++++ b/src/cryptography/hazmat/primitives/ciphers/modes.py
+@@ -220,6 +220,7 @@ def __init__(self, initialization_vector, tag=None, min_tag_length=16):
+                         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")
+diff --git a/tests/hazmat/primitives/test_aes.py b/tests/hazmat/primitives/test_aes.py
+index d6f83ebc28..4ceccf1553 100644
+--- a/tests/hazmat/primitives/test_aes.py
++++ b/tests/hazmat/primitives/test_aes.py
+@@ -439,3 +439,19 @@ def test_gcm_tag_decrypt_finalize(self, backend):
+             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")