CVE-2013-0169: Make CBC decoding constant time

(cherry-picked from 2c082d25fc3f0dd6e56c45407fe10638b904083c)

Bug: 8017911
Bug: 8095088
Change-Id: I57556e120fd1f585d38739d0d6aaf02bcbe45fbd
diff --git a/crypto/cryptlib.c b/crypto/cryptlib.c
index 50fd492..d47ab55 100644
--- a/crypto/cryptlib.c
+++ b/crypto/cryptlib.c
@@ -924,3 +924,16 @@
 	}
 
 void *OPENSSL_stderr(void)	{ return stderr; }
+
+int CRYPTO_memcmp(const void *in_a, const void *in_b, size_t len)
+	{
+	size_t i;
+	const unsigned char *a = in_a;
+	const unsigned char *b = in_b;
+	unsigned char x = 0;
+
+	for (i = 0; i < len; i++)
+		x |= a[i] ^ b[i];
+
+	return x;
+	}