change approach to EVP_PKEY_size and add changelog

pyca · Jul 20, 2017 · 0be1eee · 0be1eee
1 parent 36f8d81
commit 0be1eee
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diff --git a/CHANGELOG.rst b/CHANGELOG.rst
@@ -27,6 +27,8 @@ Changes:
 
 - Fixed a bug causing ``Context.set_default_verify_paths()`` to not work with cryptography ``manylinux1`` wheels on Python 3.x.
   `#665 <https://github.com/pyca/pyopenssl/pull/665>`_
+- Fixed a crash with (EC)DSA signatures in some cases.
+  `#670 <https://github.com/pyca/pyopenssl/pull/670>`_
 
 
 ----

diff --git a/src/OpenSSL/crypto.py b/src/OpenSSL/crypto.py
@@ -2801,13 +2801,9 @@ def sign(pkey, data, digest):
     _lib.EVP_SignInit(md_ctx, digest_obj)
     _lib.EVP_SignUpdate(md_ctx, data, len(data))
 
-    # obtain the length of the signature.
-    signature_length = _ffi.new("unsigned int[]", 1)
-    len_result = _lib.EVP_SignFinal(
-        md_ctx, _ffi.NULL, signature_length, pkey._pkey)
-    _openssl_assert(len_result == 1)
-
-    signature_buffer = _ffi.new("unsigned char[]", signature_length[0])
+    length = _lib.EVP_PKEY_size(pkey._pkey)
+    signature_buffer = _ffi.new("unsigned char[]", length)
+    signature_length = _ffi.new("unsigned int *")
     final_result = _lib.EVP_SignFinal(
         md_ctx, signature_buffer, signature_length, pkey._pkey)
     _openssl_assert(final_result == 1)