X-Git-Url: https://git.openssl.org/?a=blobdiff_plain;f=ssl%2Fs3_cbc.c;h=0019ee6e228b6432261341c5a49db2c83e31432d;hb=77ff1f3b8bfaa348956c5096a2b829f2e767b4f1;hp=58da5012705ca2fb785388b8531dc9a998e9c1e1;hpb=6b1f7beeee7edd0613a1913c08b4f101c7ea7af7;p=openssl.git diff --git a/ssl/s3_cbc.c b/ssl/s3_cbc.c index 58da501270..0019ee6e22 100644 --- a/ssl/s3_cbc.c +++ b/ssl/s3_cbc.c @@ -53,8 +53,7 @@ * */ -#include - +#include "../crypto/constant_time_locl.h" #include "ssl_locl.h" #include @@ -69,38 +68,16 @@ * 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_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 char a, unsigned char b) - { - unsigned c = a ^ b; - c--; - return DUPLICATE_MSB_TO_ALL_8(c); - } - -/* ssl3_cbc_remove_padding removes padding from the decrypted, SSLv3, CBC +/*- + * 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. */ + * -1: otherwise. + */ int ssl3_cbc_remove_padding(const SSL* s, SSL3_RECORD *rec, unsigned block_size, @@ -119,10 +96,11 @@ int ssl3_cbc_remove_padding(const SSL* s, /* 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 +/*- + * 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 @@ -132,22 +110,30 @@ int ssl3_cbc_remove_padding(const SSL* s, * returns: * 0: (in non-constant time) if the record is publicly invalid. * 1: if the padding was valid - * -1: otherwise. */ + * -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 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]; @@ -172,6 +158,13 @@ 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 @@ -188,7 +181,7 @@ 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. */ @@ -196,41 +189,16 @@ 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); 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)); + return constant_time_select_int(good, 1, -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 +/*- + * 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). * @@ -243,15 +211,18 @@ 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]; @@ -271,7 +242,7 @@ 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. */ @@ -289,16 +260,13 @@ 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_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 */ @@ -306,30 +274,43 @@ 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) @@ -341,7 +322,9 @@ static void tls1_sha1_final_raw(void* ctx, unsigned char *md_out) l2n(sha1->h3, md_out); l2n(sha1->h4, md_out); } +#define LARGEST_DIGEST_CTX SHA_CTX +#ifndef OPENSSL_NO_SHA256 static void tls1_sha256_final_raw(void* ctx, unsigned char *md_out) { SHA256_CTX *sha256 = ctx; @@ -352,7 +335,11 @@ static void tls1_sha256_final_raw(void* ctx, unsigned char *md_out) l2n(sha256->h[i], md_out); } } +#undef LARGEST_DIGEST_CTX +#define LARGEST_DIGEST_CTX SHA256_CTX +#endif +#ifndef OPENSSL_NO_SHA512 static void tls1_sha512_final_raw(void* ctx, unsigned char *md_out) { SHA512_CTX *sha512 = ctx; @@ -363,30 +350,36 @@ static void tls1_sha512_final_raw(void* ctx, unsigned char *md_out) l2n8(sha512->h[i], md_out); } } +#undef LARGEST_DIGEST_CTX +#define LARGEST_DIGEST_CTX SHA512_CTX +#endif /* ssl3_cbc_record_digest_supported returns 1 iff |ctx| uses a hash function * which ssl3_cbc_digest_record supports. */ char ssl3_cbc_record_digest_supported(const EVP_MD_CTX *ctx) { -#ifdef OPENSSL_FIPS if (FIPS_mode()) return 0; -#endif - switch (ctx->digest->type) + switch (EVP_MD_CTX_type(ctx)) { case NID_md5: case NID_sha1: +#ifndef OPENSSL_NO_SHA256 case NID_sha224: case NID_sha256: +#endif +#ifndef OPENSSL_NO_SHA512 case NID_sha384: case NID_sha512: +#endif return 1; default: return 0; } } -/* ssl3_cbc_digest_record computes the MAC of a decrypted, padded SSLv3/TLS +/*- + * ssl3_cbc_digest_record computes the MAC of a decrypted, padded SSLv3/TLS * record. * * ctx: the EVP_MD_CTX from which we take the hash function. @@ -394,7 +387,7 @@ 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 @@ -404,7 +397,8 @@ char ssl3_cbc_record_digest_supported(const EVP_MD_CTX *ctx) * On entry: by virtue of having been through one of the remove_padding * functions, above, we know that data_plus_mac_size is large enough to contain * a padding byte and MAC. (If the padding was invalid, it might contain the - * padding too. ) */ + * padding too. ) + */ void ssl3_cbc_digest_record( const EVP_MD_CTX *ctx, unsigned char* md_out, @@ -417,14 +411,15 @@ void ssl3_cbc_digest_record( unsigned mac_secret_length, char is_sslv3) { - unsigned char md_state[sizeof(SHA512_CTX)]; + union { double align; + unsigned char c[sizeof(LARGEST_DIGEST_CTX)]; } md_state; void (*md_final_raw)(void *ctx, unsigned char *md_out); void (*md_transform)(void *ctx, const unsigned char *block); unsigned md_size, md_block_size = 64; unsigned sslv3_pad_length = 40, header_length, variance_blocks, len, max_mac_bytes, num_blocks, num_starting_blocks, k, mac_end_offset, c, index_a, index_b; - uint64_t bits; + unsigned int bits; /* at most 18 bits */ unsigned char length_bytes[MAX_HASH_BIT_COUNT_BYTES]; /* hmac_pad is the masked HMAC key. */ unsigned char hmac_pad[MAX_HASH_BLOCK_SIZE]; @@ -435,40 +430,46 @@ 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); + MD5_Init((MD5_CTX*)md_state.c); md_final_raw = tls1_md5_final_raw; 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); + SHA1_Init((SHA_CTX*)md_state.c); md_final_raw = tls1_sha1_final_raw; md_transform = (void(*)(void *ctx, const unsigned char *block)) SHA1_Transform; md_size = 20; break; +#ifndef OPENSSL_NO_SHA256 case NID_sha224: - SHA224_Init((SHA256_CTX*)md_state); + SHA224_Init((SHA256_CTX*)md_state.c); md_final_raw = tls1_sha256_final_raw; md_transform = (void(*)(void *ctx, const unsigned char *block)) SHA256_Transform; md_size = 224/8; break; case NID_sha256: - SHA256_Init((SHA256_CTX*)md_state); + SHA256_Init((SHA256_CTX*)md_state.c); md_final_raw = tls1_sha256_final_raw; md_transform = (void(*)(void *ctx, const unsigned char *block)) SHA256_Transform; md_size = 32; break; +#endif +#ifndef OPENSSL_NO_SHA512 case NID_sha384: - SHA384_Init((SHA512_CTX*)md_state); + SHA384_Init((SHA512_CTX*)md_state.c); md_final_raw = tls1_sha512_final_raw; md_transform = (void(*)(void *ctx, const unsigned char *block)) SHA512_Transform; md_size = 384/8; @@ -476,13 +477,14 @@ void ssl3_cbc_digest_record( md_length_size = 16; break; case NID_sha512: - SHA512_Init((SHA512_CTX*)md_state); + SHA512_Init((SHA512_CTX*)md_state.c); md_final_raw = tls1_sha512_final_raw; md_transform = (void(*)(void *ctx, const unsigned char *block)) SHA512_Transform; md_size = 64; md_block_size = 128; md_length_size = 16; break; +#endif default: /* ssl3_cbc_record_digest_supported should have been * called first to check that the hash function is @@ -581,17 +583,25 @@ void ssl3_cbc_digest_record( for (i = 0; i < md_block_size; i++) hmac_pad[i] ^= 0x36; - md_transform(md_state, hmac_pad); + md_transform(md_state.c, hmac_pad); } - j = 0; - if (md_length_size == 16) + if (length_is_big_endian) { - memset(length_bytes, 0, 8); - j = 8; + 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; } - for (i = 0; i < 8; i++) - length_bytes[i+j] = bits >> (8*(7-i)); if (k > 0) { @@ -602,21 +612,21 @@ void ssl3_cbc_digest_record( * block that the header consumes: either 7 bytes * (SHA1) or 11 bytes (MD5). */ unsigned overhang = header_length-md_block_size; - md_transform(md_state, header); + md_transform(md_state.c, header); memcpy(first_block, header + md_block_size, overhang); memcpy(first_block + overhang, data, md_block_size-overhang); - md_transform(md_state, first_block); + md_transform(md_state.c, first_block); for (i = 1; i < k/md_block_size - 1; i++) - md_transform(md_state, data + md_block_size*i - overhang); + md_transform(md_state.c, data + md_block_size*i - overhang); } else { /* k is a multiple of md_block_size. */ memcpy(first_block, header, 13); memcpy(first_block+13, data, md_block_size-13); - md_transform(md_state, first_block); + md_transform(md_state.c, first_block); for (i = 1; i < k/md_block_size; i++) - md_transform(md_state, data + md_block_size*i - 13); + md_transform(md_state.c, data + md_block_size*i - 13); } } @@ -640,12 +650,12 @@ 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. */ @@ -661,13 +671,14 @@ 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; } - md_transform(md_state, block); - md_final_raw(md_state, block); + md_transform(md_state.c, block); + md_final_raw(md_state.c, block); /* If this is index_b, copy the hash value to |mac_out|. */ for (j = 0; j < md_size; j++) mac_out[j] |= block[j]&is_block_b; @@ -693,14 +704,12 @@ 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); } -#ifdef OPENSSL_FIPS - /* Due to the need to use EVP in FIPS mode we can't reimplement digests but * we can ensure the number of blocks processed is equal for all cases * by digesting additional data. @@ -714,7 +723,8 @@ void tls_fips_digest_extra( if (EVP_CIPHER_CTX_mode(cipher_ctx) != EVP_CIPH_CBC_MODE) return; block_size = EVP_MD_CTX_block_size(mac_ctx); - /* We are in FIPS mode if we get this far so we know we have only SHA* + /*- + * We are in FIPS mode if we get this far so we know we have only SHA* * digests and TLS to deal with. * Minimum digest padding length is 17 for SHA384/SHA512 and 9 * otherwise. @@ -744,4 +754,3 @@ void tls_fips_digest_extra( EVP_DigestSignUpdate(mac_ctx, data, (blocks_orig - blocks_data + 1) * block_size); } -#endif