| /* ==================================================================== |
| * 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 <assert.h> |
| |
| #include <openssl/md5.h> |
| #include <openssl/obj.h> |
| #include <openssl/sha.h> |
| |
| #include "ssl_locl.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 |
| |
| /* 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. |
| * |
| * 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 (int)((good & 1) | (~good & -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; |
| } |
| else if (overhead > rec->length) |
| return 0; |
| |
| padding_length = rec->data[rec->length-1]; |
| |
| if (s->options & SSL_OP_TLS_BLOCK_PADDING_BUG) |
| { |
| /* 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 = 256; /* maximum amount of padding, inc length byte. */ |
| if (to_check > rec->length) |
| to_check = rec->length; |
| |
| for (i = 0; i < to_check; i++) |
| { |
| unsigned char mask = constant_time_ge(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. 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); |
| |
| 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)); |
| } |
| |
| /* 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; |
| |
| assert(orig_len >= md_size); |
| 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(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 */ |
| #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) |
| { |
| 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 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_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; |
| |
| /* This is a, hopefully redundant, check that allows us to forget about |
| * many possible overflows later in this function. */ |
| 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. */ |
| assert(0); |
| if (md_out_size) |
| *md_out_size = -1; |
| return; |
| } |
| |
| assert(md_length_size <= MAX_HASH_BIT_COUNT_BYTES); |
| assert(md_block_size <= MAX_HASH_BLOCK_SIZE); |
| 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); |
| 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(j, c); |
| is_past_cp1 = is_block_a & constant_time_ge(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); |
| /* 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 = (b&~is_block_b) | (is_block_b&length_bytes[j-(md_block_size-md_length_size)]); |
| } |
| 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); |
| } |
| 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); |
| } |