/* 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