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Diffstat (limited to 'openssl/ssl/s3_cbc.c')
| -rw-r--r-- | openssl/ssl/s3_cbc.c | 790 |
1 files changed, 790 insertions, 0 deletions
diff --git a/openssl/ssl/s3_cbc.c b/openssl/ssl/s3_cbc.c new file mode 100644 index 000000000..02edf3f91 --- /dev/null +++ b/openssl/ssl/s3_cbc.c @@ -0,0 +1,790 @@ +/* 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 "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 + +/* 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 (s->version >= TLS1_1_VERSION || s->version == DTLS1_VERSION) + { + /* 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--; + } + } + + 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(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; + + 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(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) + { +#ifdef OPENSSL_FIPS + if (FIPS_mode()) + return 0; +#endif + 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. */ + 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(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); + } + +#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, 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); + } +#endif |