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821 lines
30 KiB
821 lines
30 KiB
4 years ago
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/* ssl/s3_cbc.c */
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/* ====================================================================
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* Copyright (c) 2012 The OpenSSL Project. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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*
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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*
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* 3. All advertising materials mentioning features or use of this
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* software must display the following acknowledgment:
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* "This product includes software developed by the OpenSSL Project
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* for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
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*
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* 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
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* endorse or promote products derived from this software without
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* prior written permission. For written permission, please contact
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* openssl-core@openssl.org.
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*
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* 5. Products derived from this software may not be called "OpenSSL"
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* nor may "OpenSSL" appear in their names without prior written
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* permission of the OpenSSL Project.
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*
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* 6. Redistributions of any form whatsoever must retain the following
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* acknowledgment:
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* "This product includes software developed by the OpenSSL Project
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* for use in the OpenSSL Toolkit (http://www.openssl.org/)"
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*
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* THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
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* EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR
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* ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
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* OF THE POSSIBILITY OF SUCH DAMAGE.
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* ====================================================================
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*
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* This product includes cryptographic software written by Eric Young
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* (eay@cryptsoft.com). This product includes software written by Tim
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* Hudson (tjh@cryptsoft.com).
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*
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*/
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#include "../crypto/constant_time_locl.h"
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#include "ssl_locl.h"
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#include <openssl/md5.h>
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#include <openssl/sha.h>
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/*
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* MAX_HASH_BIT_COUNT_BYTES is the maximum number of bytes in the hash's
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* length field. (SHA-384/512 have 128-bit length.)
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*/
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#define MAX_HASH_BIT_COUNT_BYTES 16
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/*
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* MAX_HASH_BLOCK_SIZE is the maximum hash block size that we'll support.
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* Currently SHA-384/512 has a 128-byte block size and that's the largest
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* supported by TLS.)
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*/
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#define MAX_HASH_BLOCK_SIZE 128
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/*-
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* ssl3_cbc_remove_padding removes padding from the decrypted, SSLv3, CBC
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* record in |rec| by updating |rec->length| in constant time.
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*
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* block_size: the block size of the cipher used to encrypt the record.
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* returns:
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* 0: (in non-constant time) if the record is publicly invalid.
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* 1: if the padding was valid
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* -1: otherwise.
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*/
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int ssl3_cbc_remove_padding(const SSL *s,
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SSL3_RECORD *rec,
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unsigned block_size, unsigned mac_size)
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{
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unsigned padding_length, good;
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const unsigned overhead = 1 /* padding length byte */ + mac_size;
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/*
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* These lengths are all public so we can test them in non-constant time.
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*/
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if (overhead > rec->length)
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return 0;
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padding_length = rec->data[rec->length - 1];
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good = constant_time_ge(rec->length, padding_length + overhead);
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/* SSLv3 requires that the padding is minimal. */
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good &= constant_time_ge(block_size, padding_length + 1);
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padding_length = good & (padding_length + 1);
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rec->length -= padding_length;
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rec->type |= padding_length << 8; /* kludge: pass padding length */
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return constant_time_select_int(good, 1, -1);
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}
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/*-
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* tls1_cbc_remove_padding removes the CBC padding from the decrypted, TLS, CBC
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* record in |rec| in constant time and returns 1 if the padding is valid and
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* -1 otherwise. It also removes any explicit IV from the start of the record
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* without leaking any timing about whether there was enough space after the
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* padding was removed.
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*
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* block_size: the block size of the cipher used to encrypt the record.
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* returns:
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* 0: (in non-constant time) if the record is publicly invalid.
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* 1: if the padding was valid
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* -1: otherwise.
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*/
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int tls1_cbc_remove_padding(const SSL *s,
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SSL3_RECORD *rec,
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unsigned block_size, unsigned mac_size)
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{
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unsigned padding_length, good, to_check, i;
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const unsigned overhead = 1 /* padding length byte */ + mac_size;
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/* Check if version requires explicit IV */
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if (s->version >= TLS1_1_VERSION || s->version == DTLS1_BAD_VER) {
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/*
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* These lengths are all public so we can test them in non-constant
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* time.
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*/
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if (overhead + block_size > rec->length)
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return 0;
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/* We can now safely skip explicit IV */
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rec->data += block_size;
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rec->input += block_size;
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rec->length -= block_size;
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} else if (overhead > rec->length)
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return 0;
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padding_length = rec->data[rec->length - 1];
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/*
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* NB: if compression is in operation the first packet may not be of even
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* length so the padding bug check cannot be performed. This bug
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* workaround has been around since SSLeay so hopefully it is either
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* fixed now or no buggy implementation supports compression [steve]
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*/
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if ((s->options & SSL_OP_TLS_BLOCK_PADDING_BUG) && !s->expand) {
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/* First packet is even in size, so check */
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if ((CRYPTO_memcmp(s->s3->read_sequence, "\0\0\0\0\0\0\0\0", 8) == 0) &&
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!(padding_length & 1)) {
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s->s3->flags |= TLS1_FLAGS_TLS_PADDING_BUG;
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}
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if ((s->s3->flags & TLS1_FLAGS_TLS_PADDING_BUG) && padding_length > 0) {
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padding_length--;
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}
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}
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if (EVP_CIPHER_flags(s->enc_read_ctx->cipher) & EVP_CIPH_FLAG_AEAD_CIPHER) {
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/* padding is already verified */
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rec->length -= padding_length + 1;
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return 1;
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}
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good = constant_time_ge(rec->length, overhead + padding_length);
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/*
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* The padding consists of a length byte at the end of the record and
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* then that many bytes of padding, all with the same value as the length
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* byte. Thus, with the length byte included, there are i+1 bytes of
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* padding. We can't check just |padding_length+1| bytes because that
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* leaks decrypted information. Therefore we always have to check the
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* maximum amount of padding possible. (Again, the length of the record
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* is public information so we can use it.)
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*/
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to_check = 255; /* maximum amount of padding. */
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if (to_check > rec->length - 1)
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to_check = rec->length - 1;
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for (i = 0; i < to_check; i++) {
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unsigned char mask = constant_time_ge_8(padding_length, i);
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unsigned char b = rec->data[rec->length - 1 - i];
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/*
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* The final |padding_length+1| bytes should all have the value
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* |padding_length|. Therefore the XOR should be zero.
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*/
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good &= ~(mask & (padding_length ^ b));
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}
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/*
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* If any of the final |padding_length+1| bytes had the wrong value, one
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* or more of the lower eight bits of |good| will be cleared.
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*/
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good = constant_time_eq(0xff, good & 0xff);
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padding_length = good & (padding_length + 1);
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rec->length -= padding_length;
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rec->type |= padding_length << 8; /* kludge: pass padding length */
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return constant_time_select_int(good, 1, -1);
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}
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/*-
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* ssl3_cbc_copy_mac copies |md_size| bytes from the end of |rec| to |out| in
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* constant time (independent of the concrete value of rec->length, which may
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* vary within a 256-byte window).
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*
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* ssl3_cbc_remove_padding or tls1_cbc_remove_padding must be called prior to
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* this function.
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*
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* On entry:
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* rec->orig_len >= md_size
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* md_size <= EVP_MAX_MD_SIZE
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*
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* If CBC_MAC_ROTATE_IN_PLACE is defined then the rotation is performed with
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* variable accesses in a 64-byte-aligned buffer. Assuming that this fits into
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* a single or pair of cache-lines, then the variable memory accesses don't
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* actually affect the timing. CPUs with smaller cache-lines [if any] are
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* not multi-core and are not considered vulnerable to cache-timing attacks.
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*/
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#define CBC_MAC_ROTATE_IN_PLACE
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void ssl3_cbc_copy_mac(unsigned char *out,
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const SSL3_RECORD *rec,
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unsigned md_size, unsigned orig_len)
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{
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#if defined(CBC_MAC_ROTATE_IN_PLACE)
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unsigned char rotated_mac_buf[64 + EVP_MAX_MD_SIZE];
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unsigned char *rotated_mac;
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#else
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unsigned char rotated_mac[EVP_MAX_MD_SIZE];
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#endif
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/*
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* mac_end is the index of |rec->data| just after the end of the MAC.
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*/
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unsigned mac_end = rec->length;
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unsigned mac_start = mac_end - md_size;
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/*
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* scan_start contains the number of bytes that we can ignore because the
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* MAC's position can only vary by 255 bytes.
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*/
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unsigned scan_start = 0;
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unsigned i, j;
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unsigned div_spoiler;
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unsigned rotate_offset;
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OPENSSL_assert(orig_len >= md_size);
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OPENSSL_assert(md_size <= EVP_MAX_MD_SIZE);
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#if defined(CBC_MAC_ROTATE_IN_PLACE)
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rotated_mac = rotated_mac_buf + ((0 - (size_t)rotated_mac_buf) & 63);
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#endif
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/* This information is public so it's safe to branch based on it. */
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if (orig_len > md_size + 255 + 1)
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scan_start = orig_len - (md_size + 255 + 1);
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/*
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* div_spoiler contains a multiple of md_size that is used to cause the
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* modulo operation to be constant time. Without this, the time varies
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* based on the amount of padding when running on Intel chips at least.
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* The aim of right-shifting md_size is so that the compiler doesn't
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* figure out that it can remove div_spoiler as that would require it to
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* prove that md_size is always even, which I hope is beyond it.
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*/
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div_spoiler = md_size >> 1;
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div_spoiler <<= (sizeof(div_spoiler) - 1) * 8;
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rotate_offset = (div_spoiler + mac_start - scan_start) % md_size;
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memset(rotated_mac, 0, md_size);
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for (i = scan_start, j = 0; i < orig_len; i++) {
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unsigned char mac_started = constant_time_ge_8(i, mac_start);
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unsigned char mac_ended = constant_time_ge_8(i, mac_end);
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unsigned char b = rec->data[i];
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rotated_mac[j++] |= b & mac_started & ~mac_ended;
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j &= constant_time_lt(j, md_size);
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}
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/* Now rotate the MAC */
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#if defined(CBC_MAC_ROTATE_IN_PLACE)
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j = 0;
|
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for (i = 0; i < md_size; i++) {
|
||
|
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/* in case cache-line is 32 bytes, touch second line */
|
||
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((volatile unsigned char *)rotated_mac)[rotate_offset ^ 32];
|
||
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out[j++] = rotated_mac[rotate_offset++];
|
||
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rotate_offset &= constant_time_lt(rotate_offset, md_size);
|
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}
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#else
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memset(out, 0, md_size);
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rotate_offset = md_size - rotate_offset;
|
||
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rotate_offset &= constant_time_lt(rotate_offset, md_size);
|
||
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for (i = 0; i < md_size; i++) {
|
||
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for (j = 0; j < md_size; j++)
|
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|
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out[j] |= rotated_mac[i] & constant_time_eq_8(j, rotate_offset);
|
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|
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rotate_offset++;
|
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|
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rotate_offset &= constant_time_lt(rotate_offset, md_size);
|
||
|
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}
|
||
|
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#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), \
|
||
|
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*((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;
|
||
|
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u32toLE(md5->A, md_out);
|
||
|
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u32toLE(md5->B, md_out);
|
||
|
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u32toLE(md5->C, md_out);
|
||
|
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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. )
|
||
|
|
* Returns 1 on success or 0 on error
|
||
|
|
*/
|
||
|
|
int 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:
|
||
|
|
if (MD5_Init((MD5_CTX *)md_state.c) <= 0)
|
||
|
|
return 0;
|
||
|
|
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:
|
||
|
|
if (SHA1_Init((SHA_CTX *)md_state.c) <= 0)
|
||
|
|
return 0;
|
||
|
|
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:
|
||
|
|
if (SHA224_Init((SHA256_CTX *)md_state.c) <= 0)
|
||
|
|
return 0;
|
||
|
|
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:
|
||
|
|
if (SHA256_Init((SHA256_CTX *)md_state.c) <= 0)
|
||
|
|
return 0;
|
||
|
|
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:
|
||
|
|
if (SHA384_Init((SHA512_CTX *)md_state.c) <= 0)
|
||
|
|
return 0;
|
||
|
|
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:
|
||
|
|
if (SHA512_Init((SHA512_CTX *)md_state.c) <= 0)
|
||
|
|
return 0;
|
||
|
|
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 0;
|
||
|
|
}
|
||
|
|
|
||
|
|
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) {
|
||
|
|
unsigned overhang;
|
||
|
|
|
||
|
|
/*
|
||
|
|
* 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). There are no
|
||
|
|
* ciphersuites in SSLv3 that are not SHA1 or MD5 based and
|
||
|
|
* therefore we can be confident that the header_length will be
|
||
|
|
* greater than |md_block_size|. However we add a sanity check just
|
||
|
|
* in case
|
||
|
|
*/
|
||
|
|
if (header_length <= md_block_size) {
|
||
|
|
/* Should never happen */
|
||
|
|
return 0;
|
||
|
|
}
|
||
|
|
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);
|
||
|
|
if (EVP_DigestInit_ex(&md_ctx, ctx->digest, NULL /* engine */ ) <= 0)
|
||
|
|
goto err;
|
||
|
|
if (is_sslv3) {
|
||
|
|
/* We repurpose |hmac_pad| to contain the SSLv3 pad2 block. */
|
||
|
|
memset(hmac_pad, 0x5c, sslv3_pad_length);
|
||
|
|
|
||
|
|
if (EVP_DigestUpdate(&md_ctx, mac_secret, mac_secret_length) <= 0
|
||
|
|
|| EVP_DigestUpdate(&md_ctx, hmac_pad, sslv3_pad_length) <= 0
|
||
|
|
|| EVP_DigestUpdate(&md_ctx, mac_out, md_size) <= 0)
|
||
|
|
goto err;
|
||
|
|
} else {
|
||
|
|
/* Complete the HMAC in the standard manner. */
|
||
|
|
for (i = 0; i < md_block_size; i++)
|
||
|
|
hmac_pad[i] ^= 0x6a;
|
||
|
|
|
||
|
|
if (EVP_DigestUpdate(&md_ctx, hmac_pad, md_block_size) <= 0
|
||
|
|
|| EVP_DigestUpdate(&md_ctx, mac_out, md_size) <= 0)
|
||
|
|
goto err;
|
||
|
|
}
|
||
|
|
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);
|
||
|
|
|
||
|
|
return 1;
|
||
|
|
err:
|
||
|
|
EVP_MD_CTX_cleanup(&md_ctx);
|
||
|
|
return 0;
|
||
|
|
}
|
||
|
|
|
||
|
|
#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
|