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Add and use a constant-time memcmp.

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This change adds CRYPTO_memcmp, which compares two vectors of bytes in
an amount of time that's independent of their contents. It also changes
several MAC compares in the code to use this over the standard memcmp,
which may leak information about the size of a matching prefix.
(cherry picked from commit 2ee798880a)

Conflicts:
	crypto/crypto.h
	ssl/t1_lib.c
This commit is contained in:
Ben Laurie
2013-01-28 17:30:38 +00:00
committed by Dr. Stephen Henson
parent ebc71865f0
commit 9c00a95060
9 changed files with 27 additions and 8 deletions
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2
ssl/t1_lib.c
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@@ -1744,7 +1744,7 @@ static int tls_decrypt_ticket(SSL *s, const unsigned char *etick, int eticklen,
HMAC_Update(&hctx, etick, eticklen);
HMAC_Final(&hctx, tick_hmac, NULL);
HMAC_CTX_cleanup(&hctx);
if (memcmp(tick_hmac, etick + eticklen, mlen))
if (CRYPTO_memcmp(tick_hmac, etick + eticklen, mlen))
goto tickerr;
/* Attempt to decrypt session data */
/* Move p after IV to start of encrypted ticket, update length */