X-Git-Url: https://git.openssl.org/gitweb/?p=openssl.git;a=blobdiff_plain;f=ssl%2Fs3_cbc.c;h=73e12b6799b3e95d02773ac772f7a81225666b7c;hp=da53a6da3b735fceeeda6d3942d085704580b8eb;hb=4e64f671c97650b060f20b6d930a88f1a2a306f7;hpb=bbb4ee85748743d19576a430034f28026c39903c diff --git a/ssl/s3_cbc.c b/ssl/s3_cbc.c index da53a6da3b..73e12b6799 100644 --- a/ssl/s3_cbc.c +++ b/ssl/s3_cbc.c @@ -76,6 +76,13 @@ #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_ge(unsigned a, unsigned b) { @@ -84,7 +91,7 @@ static unsigned constant_time_ge(unsigned a, unsigned b) } /* constant_time_eq_8 returns 0xff if a==b and 0x00 otherwise. */ -static unsigned char constant_time_eq_8(unsigned char a, unsigned char b) +static unsigned char constant_time_eq_8(unsigned a, unsigned b) { unsigned c = a ^ b; c--; @@ -137,15 +144,22 @@ int tls1_cbc_remove_padding(const SSL* s, unsigned mac_size) { unsigned padding_length, good, to_check, i; - const char has_explicit_iv = - s->version >= TLS1_1_VERSION || s->version == DTLS1_VERSION; - const unsigned overhead = 1 /* padding length byte */ + - mac_size + - (has_explicit_iv ? block_size : 0); - - /* These lengths are all public so we can test them in non-constant - * time. */ - if (overhead > rec->length) + 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]; @@ -170,6 +184,13 @@ int tls1_cbc_remove_padding(const SSL* s, } } + 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 @@ -205,29 +226,9 @@ int tls1_cbc_remove_padding(const SSL* s, rec->length -= good & (padding_length+1); - /* We can always safely skip the explicit IV. We check at the beginning - * of this function that the record has at least enough space for the - * IV, MAC and padding length byte. (These can be checked in - * non-constant time because it's all public information.) So, if the - * padding was invalid, then we didn't change |rec->length| and this is - * safe. If the padding was valid then we know that we have at least - * overhead+padding_length bytes of space and so this is still safe - * because overhead accounts for the explicit IV. */ - if (has_explicit_iv) - { - rec->data += block_size; - rec->input += block_size; - rec->length -= block_size; - rec->orig_len -= block_size; - } - 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). @@ -241,15 +242,18 @@ 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) { #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]; @@ -269,7 +273,7 @@ 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. */ @@ -287,16 +291,13 @@ void ssl3_cbc_copy_mac(unsigned char* out, rotate_offset = (div_spoiler + mac_start - scan_start) % md_size; memset(rotated_mac, 0, md_size); - for (i = scan_start; i < rec->orig_len;) + for (i = scan_start, j = 0; i < rec->orig_len; i++) { - for (j = 0; j < md_size && i < rec->orig_len; i++, j++) - { - unsigned char mac_started = constant_time_ge(i, mac_start); - unsigned char mac_ended = constant_time_ge(i, mac_end); - unsigned char b = 0; - b = rec->data[i]; - rotated_mac[j] |= b & mac_started & ~mac_ended; - } + unsigned char mac_started = constant_time_ge(i, mac_start); + unsigned char mac_ended = constant_time_ge(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 */ @@ -304,30 +305,43 @@ void ssl3_cbc_copy_mac(unsigned char* out, j = 0; for (i = 0; i < md_size; i++) { - unsigned char offset = (div_spoiler + rotate_offset + i) % md_size; - out[j++] = rotated_mac[offset]; + /* 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++) { - unsigned char offset = (div_spoiler + md_size - rotate_offset + i) % md_size; for (j = 0; j < md_size; j++) - out[j] |= rotated_mac[i] & constant_time_eq_8(j, offset); + 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 + * little-endian order. The value of p is advanced by four. */ +#define u32toLE(n, p) \ + (*((p)++)=(unsigned char)(n), \ + *((p)++)=(unsigned char)(n>>8), \ + *((p)++)=(unsigned char)(n>>16), \ + *((p)++)=(unsigned char)(n>>24)) + /* These functions serialize the state of a hash and thus perform the standard * "final" operation without adding the padding and length that such a function * typically does. */ static void tls1_md5_final_raw(void* ctx, unsigned char *md_out) { MD5_CTX *md5 = ctx; - l2n(md5->A, md_out); - l2n(md5->B, md_out); - l2n(md5->C, md_out); - l2n(md5->D, md_out); + u32toLE(md5->A, md_out); + u32toLE(md5->B, md_out); + u32toLE(md5->C, md_out); + u32toLE(md5->D, md_out); } static void tls1_sha1_final_raw(void* ctx, unsigned char *md_out) @@ -379,7 +393,7 @@ char ssl3_cbc_record_digest_supported(const EVP_MD_CTX *ctx) if (FIPS_mode()) return 0; #endif - switch (ctx->digest->type) + switch (EVP_MD_CTX_type(ctx)) { case NID_md5: case NID_sha1: @@ -405,7 +419,7 @@ char ssl3_cbc_record_digest_supported(const EVP_MD_CTX *ctx) * 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 @@ -447,12 +461,14 @@ void ssl3_cbc_digest_record( /* mdLengthSize is the number of bytes in the length field that terminates * 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. */ OPENSSL_assert(data_plus_mac_plus_padding_size < 1024*1024); - switch (ctx->digest->type) + switch (EVP_MD_CTX_type(ctx)) { case NID_md5: MD5_Init((MD5_CTX*)md_state.c); @@ -460,6 +476,7 @@ void ssl3_cbc_digest_record( md_transform = (void(*)(void *ctx, const unsigned char *block)) MD5_Transform; md_size = 16; sslv3_pad_length = 48; + length_is_big_endian = 0; break; case NID_sha1: SHA1_Init((SHA_CTX*)md_state.c); @@ -600,11 +617,22 @@ void ssl3_cbc_digest_record( md_transform(md_state.c, hmac_pad); } - memset(length_bytes,0,md_length_size-4); - length_bytes[md_length_size-4] = (unsigned char)(bits>>24); - length_bytes[md_length_size-3] = (unsigned char)(bits>>16); - length_bytes[md_length_size-2] = (unsigned char)(bits>>8); - length_bytes[md_length_size-1] = (unsigned char)bits; + if (length_is_big_endian) + { + memset(length_bytes,0,md_length_size-4); + length_bytes[md_length_size-4] = (unsigned char)(bits>>24); + length_bytes[md_length_size-3] = (unsigned char)(bits>>16); + length_bytes[md_length_size-2] = (unsigned char)(bits>>8); + length_bytes[md_length_size-1] = (unsigned char)bits; + } + else + { + memset(length_bytes,0,md_length_size); + length_bytes[md_length_size-5] = (unsigned char)(bits>>24); + length_bytes[md_length_size-6] = (unsigned char)(bits>>16); + length_bytes[md_length_size-7] = (unsigned char)(bits>>8); + length_bytes[md_length_size-8] = (unsigned char)bits; + } if (k > 0) { @@ -706,8 +734,8 @@ void ssl3_cbc_digest_record( 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); }