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Improve robustness of DER recoding code

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Add some defensive programming on top of #5634.

This copies the respective OpenSSL code in ECDSA_verify in
OpenSSL pre-1.0.1k (e.g. https://github.com/openssl/openssl/blob/OpenSSL_1_0_1j/crypto/ecdsa/ecs_vrf.c#L89)
more closely.

As reported by @sergiodemianlerner.
This commit is contained in:
Wladimir J. van der Laan 2015-01-11 11:08:53 +01:00
parent 4f73a8f64d
commit c6b7b29f23
1 changed files with 12 additions and 1 deletions
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13
src/ecwrapper.cpp
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@ -124,7 +124,18 @@ bool CECKey::Verify(const uint256 &hash, const std::vector<unsigned char>& vchSi
unsigned char *norm_der = NULL; unsigned char *norm_der = NULL;
ECDSA_SIG *norm_sig = ECDSA_SIG_new(); ECDSA_SIG *norm_sig = ECDSA_SIG_new();
const unsigned char* sigptr = &vchSig[0]; const unsigned char* sigptr = &vchSig[0];
d2i_ECDSA_SIG(&norm_sig, &sigptr, vchSig.size()); assert(norm_sig);
if (d2i_ECDSA_SIG(&norm_sig, &sigptr, vchSig.size()) == NULL)
{
/* As of OpenSSL 1.0.0p d2i_ECDSA_SIG frees and nulls the pointer on
* error. But OpenSSL's own use of this function redundantly frees the
* result. As ECDSA_SIG_free(NULL) is a no-op, and in the absence of a
* clear contract for the function behaving the same way is more
* conservative.
*/
ECDSA_SIG_free(norm_sig);
return false;
}
int derlen = i2d_ECDSA_SIG(norm_sig, &norm_der); int derlen = i2d_ECDSA_SIG(norm_sig, &norm_der);
ECDSA_SIG_free(norm_sig); ECDSA_SIG_free(norm_sig);
if (derlen <= 0) if (derlen <= 0)