| /* ssl/s3_cbc.c */ |
| /* ==================================================================== |
| * Copyright (c) 2012 The OpenSSL Project. All rights reserved. |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions |
| * are met: |
| * |
| * 1. Redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer. |
| * |
| * 2. Redistributions in binary form must reproduce the above copyright |
| * notice, this list of conditions and the following disclaimer in |
| * the documentation and/or other materials provided with the |
| * distribution. |
| * |
| * 3. All advertising materials mentioning features or use of this |
| * software must display the following acknowledgment: |
| * "This product includes software developed by the OpenSSL Project |
| * for use in the OpenSSL Toolkit. (http://www.openssl.org/)" |
| * |
| * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to |
| * endorse or promote products derived from this software without |
| * prior written permission. For written permission, please contact |
| * openssl-core@openssl.org. |
| * |
| * 5. Products derived from this software may not be called "OpenSSL" |
| * nor may "OpenSSL" appear in their names without prior written |
| * permission of the OpenSSL Project. |
| * |
| * 6. Redistributions of any form whatsoever must retain the following |
| * acknowledgment: |
| * "This product includes software developed by the OpenSSL Project |
| * for use in the OpenSSL Toolkit (http://www.openssl.org/)" |
| * |
| * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY |
| * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
| * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR |
| * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR |
| * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, |
| * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT |
| * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; |
| * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) |
| * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, |
| * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) |
| * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED |
| * OF THE POSSIBILITY OF SUCH DAMAGE. |
| * ==================================================================== |
| * |
| * This product includes cryptographic software written by Eric Young |
| * (eay@cryptsoft.com). This product includes software written by Tim |
| * Hudson (tjh@cryptsoft.com). |
| * |
| */ |
| |
| #include "../crypto/constant_time_locl.h" |
| #include "ssl_locl.h" |
| |
| #include <openssl/md5.h> |
| #include <openssl/sha.h> |
| |
| /* |
| * MAX_HASH_BIT_COUNT_BYTES is the maximum number of bytes in the hash's |
| * length field. (SHA-384/512 have 128-bit length.) |
| */ |
| #define MAX_HASH_BIT_COUNT_BYTES 16 |
| |
| /* |
| * MAX_HASH_BLOCK_SIZE is the maximum hash block size that we'll support. |
| * Currently SHA-384/512 has a 128-byte block size and that's the largest |
| * supported by TLS.) |
| */ |
| #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 |
| * 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; |
| 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) |
| { |
| SHA_CTX *sha1 = ctx; |
| l2n(sha1->h0, md_out); |
| l2n(sha1->h1, md_out); |
| l2n(sha1->h2, 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; |
| unsigned i; |
| |
| for (i = 0; i < 8; i++) { |
| 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; |
| unsigned i; |
| |
| for (i = 0; i < 8; i++) { |
| 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) |
| { |
| if (FIPS_mode()) |
| return 0; |
| 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 |
| * record. |
| * |
| * ctx: the EVP_MD_CTX from which we take the hash function. |
| * ssl3_cbc_record_digest_supported must return true for this EVP_MD_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 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 |
| * record, including padding. |
| * is_sslv3: non-zero if we are to use SSLv3. Otherwise, TLS. |
| * |
| * 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. ) |
| */ |
| void ssl3_cbc_digest_record(const EVP_MD_CTX *ctx, |
| unsigned char *md_out, |
| size_t *md_out_size, |
| const unsigned char header[13], |
| const unsigned char *data, |
| size_t data_plus_mac_size, |
| size_t data_plus_mac_plus_padding_size, |
| const unsigned char *mac_secret, |
| unsigned mac_secret_length, char is_sslv3) |
| { |
| 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; |
| 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]; |
| unsigned char first_block[MAX_HASH_BLOCK_SIZE]; |
| unsigned char mac_out[EVP_MAX_MD_SIZE]; |
| unsigned i, j, md_out_size_u; |
| EVP_MD_CTX md_ctx; |
| /* |
| * 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 (EVP_MD_CTX_type(ctx)) { |
| case NID_md5: |
| 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.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.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.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.c); |
| md_final_raw = tls1_sha512_final_raw; |
| md_transform = |
| (void (*)(void *ctx, const unsigned char *block))SHA512_Transform; |
| md_size = 384 / 8; |
| md_block_size = 128; |
| md_length_size = 16; |
| break; |
| case NID_sha512: |
| 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 supported. |
| */ |
| OPENSSL_assert(0); |
| if (md_out_size) |
| *md_out_size = -1; |
| return; |
| } |
| |
| OPENSSL_assert(md_length_size <= MAX_HASH_BIT_COUNT_BYTES); |
| OPENSSL_assert(md_block_size <= MAX_HASH_BLOCK_SIZE); |
| OPENSSL_assert(md_size <= EVP_MAX_MD_SIZE); |
| |
| header_length = 13; |
| if (is_sslv3) { |
| header_length = mac_secret_length + sslv3_pad_length + 8 /* sequence |
| * number */ + |
| 1 /* record type */ + |
| 2 /* record length */ ; |
| } |
| |
| /* |
| * variance_blocks is the number of blocks of the hash that we have to |
| * calculate in constant time because they could be altered by the |
| * padding value. In SSLv3, the padding must be minimal so the end of |
| * the plaintext varies by, at most, 15+20 = 35 bytes. (We conservatively |
| * assume that the MAC size varies from 0..20 bytes.) In case the 9 bytes |
| * of hash termination (0x80 + 64-bit length) don't fit in the final |
| * block, we say that the final two blocks can vary based on the padding. |
| * TLSv1 has MACs up to 48 bytes long (SHA-384) and the padding is not |
| * required to be minimal. Therefore we say that the final six blocks can |
| * vary based on the padding. Later in the function, if the message is |
| * short and there obviously cannot be this many blocks then |
| * variance_blocks can be reduced. |
| */ |
| variance_blocks = is_sslv3 ? 2 : 6; |
| /* |
| * From now on we're dealing with the MAC, which conceptually has 13 |
| * bytes of `header' before the start of the data (TLS) or 71/75 bytes |
| * (SSLv3) |
| */ |
| len = data_plus_mac_plus_padding_size + header_length; |
| /* |
| * max_mac_bytes contains the maximum bytes of bytes in the MAC, |
| * including * |header|, assuming that there's no padding. |
| */ |
| max_mac_bytes = len - md_size - 1; |
| /* num_blocks is the maximum number of hash blocks. */ |
| num_blocks = |
| (max_mac_bytes + 1 + md_length_size + md_block_size - |
| 1) / md_block_size; |
| /* |
| * In order to calculate the MAC in constant time we have to handle the |
| * final blocks specially because the padding value could cause the end |
| * to appear somewhere in the final |variance_blocks| blocks and we can't |
| * leak where. However, |num_starting_blocks| worth of data can be hashed |
| * right away because no padding value can affect whether they are |
| * plaintext. |
| */ |
| num_starting_blocks = 0; |
| /* |
| * k is the starting byte offset into the conceptual header||data where |
| * we start processing. |
| */ |
| k = 0; |
| /* |
| * mac_end_offset is the index just past the end of the data to be MACed. |
| */ |
| mac_end_offset = data_plus_mac_size + header_length - md_size; |
| /* |
| * c is the index of the 0x80 byte in the final hash block that contains |
| * application data. |
| */ |
| c = mac_end_offset % md_block_size; |
| /* |
| * index_a is the hash block number that contains the 0x80 terminating |
| * value. |
| */ |
| index_a = mac_end_offset / md_block_size; |
| /* |
| * index_b is the hash block number that contains the 64-bit hash length, |
| * in bits. |
| */ |
| index_b = (mac_end_offset + md_length_size) / md_block_size; |
| /* |
| * bits is the hash-length in bits. It includes the additional hash block |
| * for the masked HMAC key, or whole of |header| in the case of SSLv3. |
| */ |
| |
| /* |
| * For SSLv3, if we're going to have any starting blocks then we need at |
| * least two because the header is larger than a single block. |
| */ |
| if (num_blocks > variance_blocks + (is_sslv3 ? 1 : 0)) { |
| num_starting_blocks = num_blocks - variance_blocks; |
| k = md_block_size * num_starting_blocks; |
| } |
| |
| bits = 8 * mac_end_offset; |
| if (!is_sslv3) { |
| /* |
| * Compute the initial HMAC block. For SSLv3, the padding and secret |
| * bytes are included in |header| because they take more than a |
| * single block. |
| */ |
| bits += 8 * md_block_size; |
| memset(hmac_pad, 0, md_block_size); |
| OPENSSL_assert(mac_secret_length <= sizeof(hmac_pad)); |
| memcpy(hmac_pad, mac_secret, mac_secret_length); |
| for (i = 0; i < md_block_size; i++) |
| hmac_pad[i] ^= 0x36; |
| |
| md_transform(md_state.c, hmac_pad); |
| } |
| |
| 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) { |
| if (is_sslv3) { |
| /* |
| * The SSLv3 header is larger than a single block. overhang is |
| * the number of bytes beyond a single block that the header |
| * consumes: either 7 bytes (SHA1) or 11 bytes (MD5). |
| */ |
| unsigned overhang = header_length - md_block_size; |
| 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.c, first_block); |
| for (i = 1; i < k / md_block_size - 1; i++) |
| 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.c, first_block); |
| for (i = 1; i < k / md_block_size; i++) |
| md_transform(md_state.c, data + md_block_size * i - 13); |
| } |
| } |
| |
| memset(mac_out, 0, sizeof(mac_out)); |
| |
| /* |
| * We now process the final hash blocks. For each block, we construct it |
| * in constant time. If the |i==index_a| then we'll include the 0x80 |
| * bytes and zero pad etc. For each block we selectively copy it, in |
| * constant time, to |mac_out|. |
| */ |
| for (i = num_starting_blocks; i <= num_starting_blocks + variance_blocks; |
| i++) { |
| unsigned char block[MAX_HASH_BLOCK_SIZE]; |
| unsigned char is_block_a = constant_time_eq_8(i, index_a); |
| unsigned char is_block_b = constant_time_eq_8(i, index_b); |
| for (j = 0; j < md_block_size; j++) { |
| unsigned char b = 0, is_past_c, is_past_cp1; |
| if (k < header_length) |
| b = header[k]; |
| else if (k < data_plus_mac_plus_padding_size + header_length) |
| b = data[k - header_length]; |
| k++; |
| |
| 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 = 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. |
| */ |
| b = b & ~is_past_cp1; |
| /* |
| * If this is index_b (the final block), but not index_a (the end |
| * of the data), then the 64-bit length didn't fit into index_a |
| * and we're having to add an extra block of zeros. |
| */ |
| b &= ~is_block_b | is_block_a; |
| |
| /* |
| * The final bytes of one of the blocks contains the length. |
| */ |
| if (j >= md_block_size - md_length_size) { |
| /* If this is index_b, write a length byte. */ |
| 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.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; |
| } |
| |
| EVP_MD_CTX_init(&md_ctx); |
| EVP_DigestInit_ex(&md_ctx, ctx->digest, NULL /* engine */ ); |
| if (is_sslv3) { |
| /* We repurpose |hmac_pad| to contain the SSLv3 pad2 block. */ |
| memset(hmac_pad, 0x5c, sslv3_pad_length); |
| |
| EVP_DigestUpdate(&md_ctx, mac_secret, mac_secret_length); |
| EVP_DigestUpdate(&md_ctx, hmac_pad, sslv3_pad_length); |
| EVP_DigestUpdate(&md_ctx, mac_out, md_size); |
| } else { |
| /* Complete the HMAC in the standard manner. */ |
| for (i = 0; i < md_block_size; i++) |
| hmac_pad[i] ^= 0x6a; |
| |
| EVP_DigestUpdate(&md_ctx, hmac_pad, md_block_size); |
| EVP_DigestUpdate(&md_ctx, mac_out, md_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); |
| } |
| |
| /* |
| * 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. |
| */ |
| |
| void tls_fips_digest_extra(const EVP_CIPHER_CTX *cipher_ctx, |
| EVP_MD_CTX *mac_ctx, const unsigned char *data, |
| size_t data_len, size_t orig_len) |
| { |
| size_t block_size, digest_pad, blocks_data, blocks_orig; |
| 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* |
| * digests and TLS to deal with. |
| * Minimum digest padding length is 17 for SHA384/SHA512 and 9 |
| * otherwise. |
| * Additional header is 13 bytes. To get the number of digest blocks |
| * processed round up the amount of data plus padding to the nearest |
| * block length. Block length is 128 for SHA384/SHA512 and 64 otherwise. |
| * So we have: |
| * blocks = (payload_len + digest_pad + 13 + block_size - 1)/block_size |
| * equivalently: |
| * blocks = (payload_len + digest_pad + 12)/block_size + 1 |
| * HMAC adds a constant overhead. |
| * We're ultimately only interested in differences so this becomes |
| * blocks = (payload_len + 29)/128 |
| * for SHA384/SHA512 and |
| * blocks = (payload_len + 21)/64 |
| * otherwise. |
| */ |
| digest_pad = block_size == 64 ? 21 : 29; |
| blocks_orig = (orig_len + digest_pad) / block_size; |
| blocks_data = (data_len + digest_pad) / block_size; |
| /* |
| * MAC enough blocks to make up the difference between the original and |
| * actual lengths plus one extra block to ensure this is never a no op. |
| * The "data" pointer should always have enough space to perform this |
| * operation as it is large enough for a maximum length TLS buffer. |
| */ |
| EVP_DigestSignUpdate(mac_ctx, data, |
| (blocks_orig - blocks_data + 1) * block_size); |
| } |
