diff options
author | Matt Caswell <matt@openssl.org> | 2015-02-01 17:14:43 +0000 |
---|---|---|
committer | Matt Caswell <matt@openssl.org> | 2015-03-26 15:01:57 +0000 |
commit | 02a36fdae8cb503e2f88eac52eb3053431089397 (patch) | |
tree | 51edae5f881d512fc253259157cd635ad6e7b120 /ssl/s3_cbc.c | |
parent | fe589e6175f350a3e83b39ea07a08b0c824ea6fb (diff) |
Move more SSL3_RECORD oriented functions into ssl3_record.c
Reviewed-by: Richard Levitte <levitte@openssl.org>
Diffstat (limited to 'ssl/s3_cbc.c')
-rw-r--r-- | ssl/s3_cbc.c | 220 |
1 files changed, 0 insertions, 220 deletions
diff --git a/ssl/s3_cbc.c b/ssl/s3_cbc.c index 53e3c8764c..b20c564084 100644 --- a/ssl/s3_cbc.c +++ b/ssl/s3_cbc.c @@ -72,227 +72,7 @@ */ #define MAX_HASH_BLOCK_SIZE 128 -/*- - * ssl3_cbc_remove_padding removes padding from the decrypted, SSLv3, CBC - * record in |rec| by updating |rec->length| in constant time. - * - * block_size: the block size of the cipher used to encrypt the record. - * returns: - * 0: (in non-constant time) if the record is publicly invalid. - * 1: if the padding was valid - * -1: otherwise. - */ -int ssl3_cbc_remove_padding(const SSL *s, - SSL3_RECORD *rec, - unsigned block_size, unsigned mac_size) -{ - unsigned padding_length, good; - const unsigned overhead = 1 /* padding length byte */ + mac_size; - - /* - * These lengths are all public so we can test them in non-constant time. - */ - if (overhead > rec->length) - return 0; - - padding_length = rec->data[rec->length - 1]; - good = constant_time_ge(rec->length, padding_length + overhead); - /* SSLv3 requires that the padding is minimal. */ - good &= constant_time_ge(block_size, padding_length + 1); - rec->length -= good & (padding_length + 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 - * -1 otherwise. It also removes any explicit IV from the start of the record - * without leaking any timing about whether there was enough space after the - * padding was removed. - * - * block_size: the block size of the cipher used to encrypt the record. - * returns: - * 0: (in non-constant time) if the record is publicly invalid. - * 1: if the padding was valid - * -1: otherwise. - */ -int tls1_cbc_remove_padding(const SSL *s, - SSL3_RECORD *rec, - unsigned block_size, unsigned mac_size) -{ - unsigned padding_length, good, to_check, i; - const unsigned overhead = 1 /* padding length byte */ + mac_size; - /* Check if version requires explicit IV */ - if (SSL_USE_EXPLICIT_IV(s)) { - /* - * These lengths are all public so we can test them in non-constant - * time. - */ - if (overhead + block_size > rec->length) - return 0; - /* We can now safely skip explicit IV */ - rec->data += block_size; - rec->input += block_size; - rec->length -= block_size; - rec->orig_len -= block_size; - } else if (overhead > rec->length) - return 0; - - padding_length = rec->data[rec->length - 1]; - - /* - * NB: if compression is in operation the first packet may not be of even - * length so the padding bug check cannot be performed. This bug - * workaround has been around since SSLeay so hopefully it is either - * fixed now or no buggy implementation supports compression [steve] - */ - if ((s->options & SSL_OP_TLS_BLOCK_PADDING_BUG) && !s->expand) { - /* First packet is even in size, so check */ - if ((memcmp(s->s3->read_sequence, "\0\0\0\0\0\0\0\0", 8) == 0) && - !(padding_length & 1)) { - s->s3->flags |= TLS1_FLAGS_TLS_PADDING_BUG; - } - if ((s->s3->flags & TLS1_FLAGS_TLS_PADDING_BUG) && padding_length > 0) { - padding_length--; - } - } - - if (EVP_CIPHER_flags(s->enc_read_ctx->cipher) & EVP_CIPH_FLAG_AEAD_CIPHER) { - /* padding is already verified */ - rec->length -= padding_length + 1; - return 1; - } - - good = constant_time_ge(rec->length, overhead + padding_length); - /* - * The padding consists of a length byte at the end of the record and - * then that many bytes of padding, all with the same value as the length - * byte. Thus, with the length byte included, there are i+1 bytes of - * padding. We can't check just |padding_length+1| bytes because that - * leaks decrypted information. Therefore we always have to check the - * maximum amount of padding possible. (Again, the length of the record - * is public information so we can use it.) - */ - to_check = 255; /* maximum amount of padding. */ - if (to_check > rec->length - 1) - to_check = rec->length - 1; - - for (i = 0; i < to_check; 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. - */ - good &= ~(mask & (padding_length ^ b)); - } - - /* - * 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. - */ - good = constant_time_eq(0xff, good & 0xff); - rec->length -= good & (padding_length + 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 - * constant time (independent of the concrete value of rec->length, which may - * vary within a 256-byte window). - * - * ssl3_cbc_remove_padding or tls1_cbc_remove_padding must be called prior to - * this function. - * - * On entry: - * rec->orig_len >= md_size - * md_size <= EVP_MAX_MD_SIZE - * - * 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 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) -{ -#if defined(CBC_MAC_ROTATE_IN_PLACE) - unsigned char rotated_mac_buf[64 + EVP_MAX_MD_SIZE]; - unsigned char *rotated_mac; -#else - unsigned char rotated_mac[EVP_MAX_MD_SIZE]; -#endif - /* - * mac_end is the index of |rec->data| just after the end of the MAC. - */ - unsigned mac_end = rec->length; - unsigned mac_start = mac_end - md_size; - /* - * scan_start contains the number of bytes that we can ignore because the - * MAC's position can only vary by 255 bytes. - */ - unsigned scan_start = 0; - unsigned i, j; - unsigned div_spoiler; - unsigned rotate_offset; - - OPENSSL_assert(rec->orig_len >= md_size); - OPENSSL_assert(md_size <= EVP_MAX_MD_SIZE); - -#if defined(CBC_MAC_ROTATE_IN_PLACE) - 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. */ - if (rec->orig_len > md_size + 255 + 1) - scan_start = rec->orig_len - (md_size + 255 + 1); - /* - * div_spoiler contains a multiple of md_size that is used to cause the - * modulo operation to be constant time. Without this, the time varies - * based on the amount of padding when running on Intel chips at least. - * The aim of right-shifting md_size is so that the compiler doesn't - * figure out that it can remove div_spoiler as that would require it to - * prove that md_size is always even, which I hope is beyond it. - */ - div_spoiler = md_size >> 1; - div_spoiler <<= (sizeof(div_spoiler) - 1) * 8; - rotate_offset = (div_spoiler + mac_start - scan_start) % md_size; - - memset(rotated_mac, 0, md_size); - for (i = scan_start, j = 0; i < rec->orig_len; i++) { - 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); - } - - /* Now rotate the MAC */ -#if defined(CBC_MAC_ROTATE_IN_PLACE) - 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); - } -#else - memset(out, 0, md_size); - rotate_offset = md_size - rotate_offset; - rotate_offset &= constant_time_lt(rotate_offset, md_size); - for (i = 0; i < md_size; i++) { - for (j = 0; j < md_size; j++) - out[j] |= rotated_mac[i] & constant_time_eq_8(j, rotate_offset); - rotate_offset++; - rotate_offset &= constant_time_lt(rotate_offset, md_size); - } -#endif -} /* * u32toLE serialises an unsigned, 32-bit number (n) as four bytes at (p) in |