Commit 6a2f94b3 authored by Andy Polyakov's avatar Andy Polyakov
Browse files

s3_cbc.c: make CBC_MAC_ROTATE_IN_PLACE universal.

(cherry picked from commit f93a4187)
parent 6ba1d561
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+9 −8
Original line number Diff line number Diff line
@@ -225,10 +225,6 @@ int tls1_cbc_remove_padding(const SSL* s,
	return (int)((good & 1) | (~good & -1));
	}

#if defined(_M_AMD64) || defined(__x86_64__)
#define CBC_MAC_ROTATE_IN_PLACE
#endif

/* ssl3_cbc_copy_mac copies |md_size| bytes from the end of |rec| to |out| in
 * constant time (independent of the concrete value of rec->length, which may
 * vary within a 256-byte window).
@@ -242,15 +238,18 @@ int tls1_cbc_remove_padding(const SSL* s,
 *
 * If CBC_MAC_ROTATE_IN_PLACE is defined then the rotation is performed with
 * variable accesses in a 64-byte-aligned buffer. Assuming that this fits into
 * a single cache-line, then the variable memory accesses don't actually affect
 * the timing. This has been tested to be true on Intel amd64 chips.
 * a single or pair of cache-lines, then the variable memory accesses don't
 * actually affect the timing. CPUs with smaller cache-lines [if any] are
 * not multi-core and are not considered vulnerable to cache-timing attacks.
 */
#define CBC_MAC_ROTATE_IN_PLACE

void ssl3_cbc_copy_mac(unsigned char* out,
		       const SSL3_RECORD *rec,
		       unsigned md_size,unsigned orig_len)
	{
#if defined(CBC_MAC_ROTATE_IN_PLACE)
	unsigned char rotated_mac_buf[EVP_MAX_MD_SIZE*2];
	unsigned char rotated_mac_buf[64+EVP_MAX_MD_SIZE];
	unsigned char *rotated_mac;
#else
	unsigned char rotated_mac[EVP_MAX_MD_SIZE];
@@ -270,7 +269,7 @@ void ssl3_cbc_copy_mac(unsigned char* out,
	OPENSSL_assert(md_size <= EVP_MAX_MD_SIZE);

#if defined(CBC_MAC_ROTATE_IN_PLACE)
	rotated_mac = (unsigned char*) (((intptr_t)(rotated_mac_buf + 64)) & ~63);
	rotated_mac = rotated_mac_buf + ((0-(size_t)rotated_mac_buf)&63);
#endif

	/* This information is public so it's safe to branch based on it. */
@@ -302,6 +301,8 @@ void ssl3_cbc_copy_mac(unsigned char* out,
	j = 0;
	for (i = 0; i < md_size; i++)
		{
		/* in case cache-line is 32 bytes, touch second line */
		((volatile unsigned char *)rotated_mac)[rotate_offset^32];
		out[j++] = rotated_mac[rotate_offset++];
		rotate_offset &= constant_time_lt(rotate_offset,md_size);
		}