diff options
Diffstat (limited to 'openssl/ssl/s3_cbc.c')
| -rw-r--r-- | openssl/ssl/s3_cbc.c | 65 |
1 files changed, 15 insertions, 50 deletions
diff --git a/openssl/ssl/s3_cbc.c b/openssl/ssl/s3_cbc.c index 443a31e74..11f13adbf 100644 --- a/openssl/ssl/s3_cbc.c +++ b/openssl/ssl/s3_cbc.c @@ -53,6 +53,7 @@ * */ +#include "../crypto/constant_time_locl.h" #include "ssl_locl.h" #include <openssl/md5.h> @@ -67,37 +68,6 @@ * 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. * @@ -126,8 +96,8 @@ int ssl3_cbc_remove_padding(const SSL* s, padding_length = good & (padding_length+1); rec->length -= padding_length; rec->type |= padding_length<<8; /* kludge: pass padding length */ - 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 @@ -208,7 +178,7 @@ int tls1_cbc_remove_padding(const SSL* s, 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. */ @@ -216,20 +186,14 @@ int tls1_cbc_remove_padding(const SSL* s, } /* 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); padding_length = good & (padding_length+1); rec->length -= padding_length; rec->type |= padding_length<<8; /* kludge: pass padding length */ - 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 @@ -296,8 +260,8 @@ void ssl3_cbc_copy_mac(unsigned char* out, memset(rotated_mac, 0, md_size); for (i = scan_start, j = 0; i < 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); @@ -683,12 +647,12 @@ void ssl3_cbc_digest_record( 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. */ @@ -704,7 +668,8 @@ void ssl3_cbc_digest_record( 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; } |