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487 lines
18 KiB
C
487 lines
18 KiB
C
/*
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* Copyright 2012-2018 The OpenSSL Project Authors. All Rights Reserved.
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*
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* Licensed under the OpenSSL license (the "License"). You may not use
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* this file except in compliance with the License. You can obtain a copy
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* in the file LICENSE in the source distribution or at
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* https://www.openssl.org/source/license.html
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*/
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#include "internal/constant_time.h"
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#include "ssl_local.h"
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#include "internal/cryptlib.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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* u32toLE serialises an unsigned, 32-bit number (n) as four bytes at (p) in
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* little-endian order. The value of p is advanced by four.
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*/
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#define u32toLE(n, p) \
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(*((p)++)=(unsigned char)(n), \
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*((p)++)=(unsigned char)(n>>8), \
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*((p)++)=(unsigned char)(n>>16), \
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*((p)++)=(unsigned char)(n>>24))
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/*
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* These functions serialize the state of a hash and thus perform the
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* standard "final" operation without adding the padding and length that such
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* a function typically does.
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*/
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static void tls1_md5_final_raw(void *ctx, unsigned char *md_out)
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{
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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);
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}
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static void tls1_sha1_final_raw(void *ctx, unsigned char *md_out)
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{
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SHA_CTX *sha1 = ctx;
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l2n(sha1->h0, md_out);
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l2n(sha1->h1, md_out);
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l2n(sha1->h2, md_out);
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l2n(sha1->h3, md_out);
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l2n(sha1->h4, md_out);
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}
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static void tls1_sha256_final_raw(void *ctx, unsigned char *md_out)
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{
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SHA256_CTX *sha256 = ctx;
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unsigned i;
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for (i = 0; i < 8; i++) {
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l2n(sha256->h[i], md_out);
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}
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}
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static void tls1_sha512_final_raw(void *ctx, unsigned char *md_out)
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{
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SHA512_CTX *sha512 = ctx;
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unsigned i;
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for (i = 0; i < 8; i++) {
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l2n8(sha512->h[i], md_out);
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}
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}
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#undef LARGEST_DIGEST_CTX
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#define LARGEST_DIGEST_CTX SHA512_CTX
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/*
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* ssl3_cbc_record_digest_supported returns 1 iff |ctx| uses a hash function
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* which ssl3_cbc_digest_record supports.
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*/
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char ssl3_cbc_record_digest_supported(const EVP_MD_CTX *ctx)
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{
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switch (EVP_MD_CTX_type(ctx)) {
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case NID_md5:
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case NID_sha1:
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case NID_sha224:
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case NID_sha256:
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case NID_sha384:
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case NID_sha512:
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return 1;
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default:
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return 0;
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}
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}
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/*-
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* ssl3_cbc_digest_record computes the MAC of a decrypted, padded SSLv3/TLS
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* record.
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*
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* ctx: the EVP_MD_CTX from which we take the hash function.
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* ssl3_cbc_record_digest_supported must return true for this EVP_MD_CTX.
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* md_out: the digest output. At most EVP_MAX_MD_SIZE bytes will be written.
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* md_out_size: if non-NULL, the number of output bytes is written here.
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* header: the 13-byte, TLS record header.
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* data: the record data itself, less any preceding explicit IV.
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* data_plus_mac_size: the secret, reported length of the data and MAC
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* once the padding has been removed.
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* data_plus_mac_plus_padding_size: the public length of the whole
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* record, including padding.
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* is_sslv3: non-zero if we are to use SSLv3. Otherwise, TLS.
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*
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* On entry: by virtue of having been through one of the remove_padding
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* functions, above, we know that data_plus_mac_size is large enough to contain
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* a padding byte and MAC. (If the padding was invalid, it might contain the
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* padding too. )
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* Returns 1 on success or 0 on error
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*/
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int ssl3_cbc_digest_record(const EVP_MD_CTX *ctx,
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unsigned char *md_out,
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size_t *md_out_size,
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const unsigned char header[13],
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const unsigned char *data,
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size_t data_plus_mac_size,
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size_t data_plus_mac_plus_padding_size,
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const unsigned char *mac_secret,
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size_t mac_secret_length, char is_sslv3)
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{
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union {
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double align;
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unsigned char c[sizeof(LARGEST_DIGEST_CTX)];
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} md_state;
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void (*md_final_raw) (void *ctx, unsigned char *md_out);
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void (*md_transform) (void *ctx, const unsigned char *block);
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size_t md_size, md_block_size = 64;
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size_t sslv3_pad_length = 40, header_length, variance_blocks,
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len, max_mac_bytes, num_blocks,
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num_starting_blocks, k, mac_end_offset, c, index_a, index_b;
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size_t bits; /* at most 18 bits */
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unsigned char length_bytes[MAX_HASH_BIT_COUNT_BYTES];
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/* hmac_pad is the masked HMAC key. */
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unsigned char hmac_pad[MAX_HASH_BLOCK_SIZE];
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unsigned char first_block[MAX_HASH_BLOCK_SIZE];
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unsigned char mac_out[EVP_MAX_MD_SIZE];
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size_t i, j;
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unsigned md_out_size_u;
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EVP_MD_CTX *md_ctx = NULL;
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/*
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* mdLengthSize is the number of bytes in the length field that
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* terminates * the hash.
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*/
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size_t md_length_size = 8;
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char length_is_big_endian = 1;
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int ret;
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/*
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* This is a, hopefully redundant, check that allows us to forget about
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* many possible overflows later in this function.
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*/
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if (!ossl_assert(data_plus_mac_plus_padding_size < 1024 * 1024))
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return 0;
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switch (EVP_MD_CTX_type(ctx)) {
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case NID_md5:
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if (MD5_Init((MD5_CTX *)md_state.c) <= 0)
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return 0;
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md_final_raw = tls1_md5_final_raw;
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md_transform =
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(void (*)(void *ctx, const unsigned char *block))MD5_Transform;
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md_size = 16;
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sslv3_pad_length = 48;
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length_is_big_endian = 0;
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break;
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case NID_sha1:
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if (SHA1_Init((SHA_CTX *)md_state.c) <= 0)
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return 0;
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md_final_raw = tls1_sha1_final_raw;
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md_transform =
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(void (*)(void *ctx, const unsigned char *block))SHA1_Transform;
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md_size = 20;
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break;
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case NID_sha224:
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if (SHA224_Init((SHA256_CTX *)md_state.c) <= 0)
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return 0;
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md_final_raw = tls1_sha256_final_raw;
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md_transform =
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(void (*)(void *ctx, const unsigned char *block))SHA256_Transform;
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md_size = 224 / 8;
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break;
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case NID_sha256:
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if (SHA256_Init((SHA256_CTX *)md_state.c) <= 0)
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return 0;
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md_final_raw = tls1_sha256_final_raw;
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md_transform =
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(void (*)(void *ctx, const unsigned char *block))SHA256_Transform;
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md_size = 32;
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break;
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case NID_sha384:
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if (SHA384_Init((SHA512_CTX *)md_state.c) <= 0)
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return 0;
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md_final_raw = tls1_sha512_final_raw;
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md_transform =
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(void (*)(void *ctx, const unsigned char *block))SHA512_Transform;
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md_size = 384 / 8;
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md_block_size = 128;
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md_length_size = 16;
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break;
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case NID_sha512:
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if (SHA512_Init((SHA512_CTX *)md_state.c) <= 0)
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return 0;
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md_final_raw = tls1_sha512_final_raw;
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md_transform =
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(void (*)(void *ctx, const unsigned char *block))SHA512_Transform;
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md_size = 64;
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md_block_size = 128;
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md_length_size = 16;
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break;
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default:
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/*
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* ssl3_cbc_record_digest_supported should have been called first to
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* check that the hash function is supported.
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*/
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if (md_out_size != NULL)
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*md_out_size = 0;
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return ossl_assert(0);
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}
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if (!ossl_assert(md_length_size <= MAX_HASH_BIT_COUNT_BYTES)
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|| !ossl_assert(md_block_size <= MAX_HASH_BLOCK_SIZE)
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|| !ossl_assert(md_size <= EVP_MAX_MD_SIZE))
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return 0;
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header_length = 13;
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if (is_sslv3) {
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header_length = mac_secret_length + sslv3_pad_length + 8 /* sequence
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* number */ +
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1 /* record type */ +
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2 /* record length */ ;
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}
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/*
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* variance_blocks is the number of blocks of the hash that we have to
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* calculate in constant time because they could be altered by the
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* padding value. In SSLv3, the padding must be minimal so the end of
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* the plaintext varies by, at most, 15+20 = 35 bytes. (We conservatively
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* assume that the MAC size varies from 0..20 bytes.) In case the 9 bytes
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* of hash termination (0x80 + 64-bit length) don't fit in the final
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* block, we say that the final two blocks can vary based on the padding.
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* TLSv1 has MACs up to 48 bytes long (SHA-384) and the padding is not
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* required to be minimal. Therefore we say that the final |variance_blocks|
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* blocks can
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* vary based on the padding. Later in the function, if the message is
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* short and there obviously cannot be this many blocks then
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* variance_blocks can be reduced.
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*/
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variance_blocks = is_sslv3 ? 2 : ( ((255 + 1 + md_size + md_block_size - 1) / md_block_size) + 1);
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/*
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* From now on we're dealing with the MAC, which conceptually has 13
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* bytes of `header' before the start of the data (TLS) or 71/75 bytes
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* (SSLv3)
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*/
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len = data_plus_mac_plus_padding_size + header_length;
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/*
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* max_mac_bytes contains the maximum bytes of bytes in the MAC,
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* including * |header|, assuming that there's no padding.
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*/
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max_mac_bytes = len - md_size - 1;
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/* num_blocks is the maximum number of hash blocks. */
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num_blocks =
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(max_mac_bytes + 1 + md_length_size + md_block_size -
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1) / md_block_size;
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/*
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* In order to calculate the MAC in constant time we have to handle the
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* final blocks specially because the padding value could cause the end
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* to appear somewhere in the final |variance_blocks| blocks and we can't
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* leak where. However, |num_starting_blocks| worth of data can be hashed
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* right away because no padding value can affect whether they are
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* plaintext.
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*/
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num_starting_blocks = 0;
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/*
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* k is the starting byte offset into the conceptual header||data where
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* we start processing.
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*/
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k = 0;
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/*
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* mac_end_offset is the index just past the end of the data to be MACed.
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*/
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mac_end_offset = data_plus_mac_size + header_length - md_size;
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/*
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* c is the index of the 0x80 byte in the final hash block that contains
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* application data.
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*/
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c = mac_end_offset % md_block_size;
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/*
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* index_a is the hash block number that contains the 0x80 terminating
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* value.
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*/
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index_a = mac_end_offset / md_block_size;
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/*
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* index_b is the hash block number that contains the 64-bit hash length,
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* in bits.
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*/
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index_b = (mac_end_offset + md_length_size) / md_block_size;
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/*
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* bits is the hash-length in bits. It includes the additional hash block
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* for the masked HMAC key, or whole of |header| in the case of SSLv3.
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*/
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/*
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* For SSLv3, if we're going to have any starting blocks then we need at
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* least two because the header is larger than a single block.
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*/
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if (num_blocks > variance_blocks + (is_sslv3 ? 1 : 0)) {
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num_starting_blocks = num_blocks - variance_blocks;
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k = md_block_size * num_starting_blocks;
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}
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bits = 8 * mac_end_offset;
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if (!is_sslv3) {
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/*
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* Compute the initial HMAC block. For SSLv3, the padding and secret
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* bytes are included in |header| because they take more than a
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* single block.
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*/
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bits += 8 * md_block_size;
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memset(hmac_pad, 0, md_block_size);
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if (!ossl_assert(mac_secret_length <= sizeof(hmac_pad)))
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return 0;
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memcpy(hmac_pad, mac_secret, mac_secret_length);
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for (i = 0; i < md_block_size; i++)
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hmac_pad[i] ^= 0x36;
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md_transform(md_state.c, hmac_pad);
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}
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if (length_is_big_endian) {
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memset(length_bytes, 0, md_length_size - 4);
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length_bytes[md_length_size - 4] = (unsigned char)(bits >> 24);
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length_bytes[md_length_size - 3] = (unsigned char)(bits >> 16);
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length_bytes[md_length_size - 2] = (unsigned char)(bits >> 8);
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length_bytes[md_length_size - 1] = (unsigned char)bits;
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} else {
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memset(length_bytes, 0, md_length_size);
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length_bytes[md_length_size - 5] = (unsigned char)(bits >> 24);
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length_bytes[md_length_size - 6] = (unsigned char)(bits >> 16);
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length_bytes[md_length_size - 7] = (unsigned char)(bits >> 8);
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length_bytes[md_length_size - 8] = (unsigned char)bits;
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}
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if (k > 0) {
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if (is_sslv3) {
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size_t overhang;
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/*
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* The SSLv3 header is larger than a single block. overhang is
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* the number of bytes beyond a single block that the header
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* consumes: either 7 bytes (SHA1) or 11 bytes (MD5). There are no
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* ciphersuites in SSLv3 that are not SHA1 or MD5 based and
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* therefore we can be confident that the header_length will be
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* greater than |md_block_size|. However we add a sanity check just
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* in case
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*/
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if (header_length <= md_block_size) {
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/* Should never happen */
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return 0;
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}
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overhang = header_length - md_block_size;
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md_transform(md_state.c, header);
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memcpy(first_block, header + md_block_size, overhang);
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memcpy(first_block + overhang, data, md_block_size - overhang);
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md_transform(md_state.c, first_block);
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for (i = 1; i < k / md_block_size - 1; i++)
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md_transform(md_state.c, data + md_block_size * i - overhang);
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} else {
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/* k is a multiple of md_block_size. */
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memcpy(first_block, header, 13);
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memcpy(first_block + 13, data, md_block_size - 13);
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md_transform(md_state.c, first_block);
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for (i = 1; i < k / md_block_size; i++)
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md_transform(md_state.c, data + md_block_size * i - 13);
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}
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}
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memset(mac_out, 0, sizeof(mac_out));
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/*
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* We now process the final hash blocks. For each block, we construct it
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* in constant time. If the |i==index_a| then we'll include the 0x80
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* bytes and zero pad etc. For each block we selectively copy it, in
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* constant time, to |mac_out|.
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*/
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for (i = num_starting_blocks; i <= num_starting_blocks + variance_blocks;
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i++) {
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unsigned char block[MAX_HASH_BLOCK_SIZE];
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unsigned char is_block_a = constant_time_eq_8_s(i, index_a);
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unsigned char is_block_b = constant_time_eq_8_s(i, index_b);
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for (j = 0; j < md_block_size; j++) {
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unsigned char b = 0, is_past_c, is_past_cp1;
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if (k < header_length)
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b = header[k];
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else if (k < data_plus_mac_plus_padding_size + header_length)
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b = data[k - header_length];
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k++;
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is_past_c = is_block_a & constant_time_ge_8_s(j, c);
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is_past_cp1 = is_block_a & constant_time_ge_8_s(j, c + 1);
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/*
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* If this is the block containing the end of the application
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* data, and we are at the offset for the 0x80 value, then
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* overwrite b with 0x80.
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*/
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b = constant_time_select_8(is_past_c, 0x80, b);
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/*
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* If this block contains the end of the application data
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* and we're past the 0x80 value then just write zero.
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*/
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b = b & ~is_past_cp1;
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/*
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* If this is index_b (the final block), but not index_a (the end
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* of the data), then the 64-bit length didn't fit into index_a
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* and we're having to add an extra block of zeros.
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*/
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b &= ~is_block_b | is_block_a;
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/*
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* The final bytes of one of the blocks contains the length.
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*/
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if (j >= md_block_size - md_length_size) {
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/* If this is index_b, write a length byte. */
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b = constant_time_select_8(is_block_b,
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length_bytes[j -
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(md_block_size -
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md_length_size)], b);
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}
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block[j] = b;
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}
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md_transform(md_state.c, block);
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md_final_raw(md_state.c, block);
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/* If this is index_b, copy the hash value to |mac_out|. */
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for (j = 0; j < md_size; j++)
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mac_out[j] |= block[j] & is_block_b;
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}
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md_ctx = EVP_MD_CTX_new();
|
|
if (md_ctx == NULL)
|
|
goto err;
|
|
if (EVP_DigestInit_ex(md_ctx, EVP_MD_CTX_md(ctx), 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;
|
|
}
|
|
/* TODO(size_t): Convert me */
|
|
ret = EVP_DigestFinal(md_ctx, md_out, &md_out_size_u);
|
|
if (ret && md_out_size)
|
|
*md_out_size = md_out_size_u;
|
|
EVP_MD_CTX_free(md_ctx);
|
|
|
|
return 1;
|
|
err:
|
|
EVP_MD_CTX_free(md_ctx);
|
|
return 0;
|
|
}
|