*
*/
+#include "../crypto/constant_time_locl.h"
#include "ssl_locl.h"
#include <openssl/md5.h>
* supported by TLS.) */
#define MAX_HASH_BLOCK_SIZE 128
-/* Some utility functions are needed:
- *
- * These macros return the given value with the MSB copied to all the other
- * bits. They use the fact that arithmetic shift shifts-in the sign bit.
- * However, this is not ensured by the C standard so you may need to replace
- * them with something else on odd CPUs. */
-#define DUPLICATE_MSB_TO_ALL(x) ( (unsigned)( (int)(x) >> (sizeof(int)*8-1) ) )
-#define DUPLICATE_MSB_TO_ALL_8(x) ((unsigned char)(DUPLICATE_MSB_TO_ALL(x)))
-
-/* constant_time_lt returns 0xff if a<b and 0x00 otherwise. */
-static unsigned constant_time_lt(unsigned a, unsigned b)
- {
- a -= b;
- return DUPLICATE_MSB_TO_ALL(a);
- }
-
-/* constant_time_ge returns 0xff if a>=b and 0x00 otherwise. */
-static unsigned constant_time_ge(unsigned a, unsigned b)
- {
- a -= b;
- return DUPLICATE_MSB_TO_ALL(~a);
- }
-
-/* constant_time_eq_8 returns 0xff if a==b and 0x00 otherwise. */
-static unsigned char constant_time_eq_8(unsigned a, unsigned b)
- {
- unsigned c = a ^ b;
- c--;
- return DUPLICATE_MSB_TO_ALL_8(c);
- }
-
/* ssl3_cbc_remove_padding removes padding from the decrypted, SSLv3, CBC
* record in |rec| by updating |rec->length| in constant time.
*
/* SSLv3 requires that the padding is minimal. */
good &= constant_time_ge(block_size, padding_length+1);
rec->length -= good & (padding_length+1);
- return (int)((good & 1) | (~good & -1));
-}
+ return constant_time_select_int(good, 1, -1);
+ }
/* tls1_cbc_remove_padding removes the CBC padding from the decrypted, TLS, CBC
* record in |rec| in constant time and returns 1 if the padding is valid and
unsigned padding_length, good, to_check, i;
const unsigned overhead = 1 /* padding length byte */ + mac_size;
/* Check if version requires explicit IV */
- if (s->version >= TLS1_1_VERSION || s->version == DTLS1_BAD_VER)
+ if (SSL_USE_EXPLICIT_IV(s))
{
/* These lengths are all public so we can test them in
* non-constant time.
for (i = 0; i < to_check; i++)
{
- unsigned char mask = constant_time_ge(padding_length, i);
+ unsigned char mask = constant_time_ge_8(padding_length, i);
unsigned char b = rec->data[rec->length-1-i];
/* The final |padding_length+1| bytes should all have the value
* |padding_length|. Therefore the XOR should be zero. */
}
/* If any of the final |padding_length+1| bytes had the wrong value,
- * one or more of the lower eight bits of |good| will be cleared. We
- * AND the bottom 8 bits together and duplicate the result to all the
- * bits. */
- good &= good >> 4;
- good &= good >> 2;
- good &= good >> 1;
- good <<= sizeof(good)*8-1;
- good = DUPLICATE_MSB_TO_ALL(good);
-
+ * one or more of the lower eight bits of |good| will be cleared.
+ */
+ good = constant_time_eq(0xff, good & 0xff);
rec->length -= good & (padding_length+1);
- return (int)((good & 1) | (~good & -1));
+ return constant_time_select_int(good, 1, -1);
}
/* ssl3_cbc_copy_mac copies |md_size| bytes from the end of |rec| to |out| in
memset(rotated_mac, 0, md_size);
for (i = scan_start, j = 0; i < rec->orig_len; i++)
{
- unsigned char mac_started = constant_time_ge(i, mac_start);
- unsigned char mac_ended = constant_time_ge(i, mac_end);
+ unsigned char mac_started = constant_time_ge_8(i, mac_start);
+ unsigned char mac_ended = constant_time_ge_8(i, mac_end);
unsigned char b = rec->data[i];
rotated_mac[j++] |= b & mac_started & ~mac_ended;
j &= constant_time_lt(j,md_size);
* md_out: the digest output. At most EVP_MAX_MD_SIZE bytes will be written.
* md_out_size: if non-NULL, the number of output bytes is written here.
* header: the 13-byte, TLS record header.
- * data: the record data itself, less any preceeding explicit IV.
+ * data: the record data itself, less any preceding explicit IV.
* data_plus_mac_size: the secret, reported length of the data and MAC
* once the padding has been removed.
* data_plus_mac_plus_padding_size: the public length of the whole
* the hash. */
unsigned md_length_size = 8;
char length_is_big_endian = 1;
+ int ret;
/* This is a, hopefully redundant, check that allows us to forget about
* many possible overflows later in this function. */
b = data[k-header_length];
k++;
- is_past_c = is_block_a & constant_time_ge(j, c);
- is_past_cp1 = is_block_a & constant_time_ge(j, c+1);
+ is_past_c = is_block_a & constant_time_ge_8(j, c);
+ is_past_cp1 = is_block_a & constant_time_ge_8(j, c+1);
/* If this is the block containing the end of the
* application data, and we are at the offset for the
* 0x80 value, then overwrite b with 0x80. */
- b = (b&~is_past_c) | (0x80&is_past_c);
+ b = constant_time_select_8(is_past_c, 0x80, b);
/* If this the the block containing the end of the
* application data and we're past the 0x80 value then
* just write zero. */
if (j >= md_block_size - md_length_size)
{
/* If this is index_b, write a length byte. */
- b = (b&~is_block_b) | (is_block_b&length_bytes[j-(md_block_size-md_length_size)]);
+ b = constant_time_select_8(
+ is_block_b, length_bytes[j-(md_block_size-md_length_size)], b);
}
block[j] = b;
}
EVP_DigestUpdate(&md_ctx, hmac_pad, md_block_size);
EVP_DigestUpdate(&md_ctx, mac_out, md_size);
}
- EVP_DigestFinal(&md_ctx, md_out, &md_out_size_u);
- if (md_out_size)
+ ret = EVP_DigestFinal(&md_ctx, md_out, &md_out_size_u);
+ if (ret && md_out_size)
*md_out_size = md_out_size_u;
EVP_MD_CTX_cleanup(&md_ctx);
}
projects / openssl.git / blobdiff