/* 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); padding_length = good & (padding_length+1); rec->length -= padding_length; rec->type |= padding_length<<8; /* kludge: pass padding length */ 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 (s->version == DTLS1_VERSION || s->version == DTLS1_BAD_VER) { /* 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; } 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--; } } 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); padding_length = good & (padding_length+1); rec->length -= padding_length; rec->type |= padding_length<<8; /* kludge: pass padding length */ 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,unsigned orig_len) { #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(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 (orig_len > md_size + 255 + 1) scan_start = 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 < 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 *digest) { #ifdef OPENSSL_FIPS if (FIPS_mode()) return 0; #endif switch (EVP_MD_type(digest)) { 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 preceeding 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 *digest, 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; /* 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_type(digest)) { 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, 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); } EVP_DigestFinal(&md_ctx, md_out, &md_out_size_u); if (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. */ void tls_fips_digest_extra( const EVP_CIPHER_CTX *cipher_ctx, const EVP_MD *hash, HMAC_CTX *hctx, 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_block_size(hash); /* 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. */ HMAC_Update(hctx, data, (blocks_orig - blocks_data + 1) * block_size); } #endif