[331] | 1 | /*
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| 2 | * Copyright 2012-2016 The OpenSSL Project Authors. All Rights Reserved.
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| 3 | *
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| 4 | * Licensed under the OpenSSL license (the "License"). You may not use
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| 5 | * this file except in compliance with the License. You can obtain a copy
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| 6 | * in the file LICENSE in the source distribution or at
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| 7 | * https://www.openssl.org/source/license.html
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| 8 | */
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| 9 |
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| 10 | #include "internal/constant_time_locl.h"
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| 11 | #include "ssl_locl.h"
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| 12 |
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| 13 | #include <openssl/md5.h>
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| 14 | #include <openssl/sha.h>
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| 15 |
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| 16 | /*
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| 17 | * MAX_HASH_BIT_COUNT_BYTES is the maximum number of bytes in the hash's
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| 18 | * length field. (SHA-384/512 have 128-bit length.)
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| 19 | */
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| 20 | #define MAX_HASH_BIT_COUNT_BYTES 16
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| 21 |
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| 22 | /*
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| 23 | * MAX_HASH_BLOCK_SIZE is the maximum hash block size that we'll support.
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| 24 | * Currently SHA-384/512 has a 128-byte block size and that's the largest
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| 25 | * supported by TLS.)
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| 26 | */
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| 27 | #define MAX_HASH_BLOCK_SIZE 128
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| 28 |
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| 29 | /*
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| 30 | * u32toLE serialises an unsigned, 32-bit number (n) as four bytes at (p) in
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| 31 | * little-endian order. The value of p is advanced by four.
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| 32 | */
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| 33 | #define u32toLE(n, p) \
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| 34 | (*((p)++)=(unsigned char)(n), \
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| 35 | *((p)++)=(unsigned char)(n>>8), \
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| 36 | *((p)++)=(unsigned char)(n>>16), \
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| 37 | *((p)++)=(unsigned char)(n>>24))
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| 38 |
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| 39 | /*
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| 40 | * These functions serialize the state of a hash and thus perform the
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| 41 | * standard "final" operation without adding the padding and length that such
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| 42 | * a function typically does.
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| 43 | */
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| 44 | static void tls1_md5_final_raw(void *ctx, unsigned char *md_out)
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| 45 | {
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| 46 | MD5_CTX *md5 = ctx;
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| 47 | u32toLE(md5->A, md_out);
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| 48 | u32toLE(md5->B, md_out);
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| 49 | u32toLE(md5->C, md_out);
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| 50 | u32toLE(md5->D, md_out);
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| 51 | }
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| 52 |
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| 53 | static void tls1_sha1_final_raw(void *ctx, unsigned char *md_out)
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| 54 | {
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| 55 | SHA_CTX *sha1 = ctx;
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| 56 | l2n(sha1->h0, md_out);
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| 57 | l2n(sha1->h1, md_out);
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| 58 | l2n(sha1->h2, md_out);
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| 59 | l2n(sha1->h3, md_out);
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| 60 | l2n(sha1->h4, md_out);
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| 61 | }
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| 62 |
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| 63 | static void tls1_sha256_final_raw(void *ctx, unsigned char *md_out)
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| 64 | {
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| 65 | SHA256_CTX *sha256 = ctx;
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| 66 | unsigned i;
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| 67 |
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| 68 | for (i = 0; i < 8; i++) {
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| 69 | l2n(sha256->h[i], md_out);
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| 70 | }
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| 71 | }
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| 72 |
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| 73 | static void tls1_sha512_final_raw(void *ctx, unsigned char *md_out)
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| 74 | {
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| 75 | SHA512_CTX *sha512 = ctx;
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| 76 | unsigned i;
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| 77 |
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| 78 | for (i = 0; i < 8; i++) {
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| 79 | l2n8(sha512->h[i], md_out);
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| 80 | }
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| 81 | }
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| 82 |
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| 83 | #undef LARGEST_DIGEST_CTX
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| 84 | #define LARGEST_DIGEST_CTX SHA512_CTX
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| 85 |
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| 86 | /*
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| 87 | * ssl3_cbc_record_digest_supported returns 1 iff |ctx| uses a hash function
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| 88 | * which ssl3_cbc_digest_record supports.
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| 89 | */
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| 90 | char ssl3_cbc_record_digest_supported(const EVP_MD_CTX *ctx)
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| 91 | {
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| 92 | if (FIPS_mode())
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| 93 | return 0;
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| 94 | switch (EVP_MD_CTX_type(ctx)) {
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| 95 | case NID_md5:
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| 96 | case NID_sha1:
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| 97 | case NID_sha224:
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| 98 | case NID_sha256:
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| 99 | case NID_sha384:
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| 100 | case NID_sha512:
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| 101 | return 1;
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| 102 | default:
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| 103 | return 0;
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| 104 | }
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| 105 | }
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| 106 |
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| 107 | /*-
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| 108 | * ssl3_cbc_digest_record computes the MAC of a decrypted, padded SSLv3/TLS
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| 109 | * record.
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| 110 | *
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| 111 | * ctx: the EVP_MD_CTX from which we take the hash function.
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| 112 | * ssl3_cbc_record_digest_supported must return true for this EVP_MD_CTX.
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| 113 | * md_out: the digest output. At most EVP_MAX_MD_SIZE bytes will be written.
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| 114 | * md_out_size: if non-NULL, the number of output bytes is written here.
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| 115 | * header: the 13-byte, TLS record header.
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| 116 | * data: the record data itself, less any preceding explicit IV.
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| 117 | * data_plus_mac_size: the secret, reported length of the data and MAC
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| 118 | * once the padding has been removed.
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| 119 | * data_plus_mac_plus_padding_size: the public length of the whole
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| 120 | * record, including padding.
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| 121 | * is_sslv3: non-zero if we are to use SSLv3. Otherwise, TLS.
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| 122 | *
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| 123 | * On entry: by virtue of having been through one of the remove_padding
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| 124 | * functions, above, we know that data_plus_mac_size is large enough to contain
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| 125 | * a padding byte and MAC. (If the padding was invalid, it might contain the
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| 126 | * padding too. )
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| 127 | * Returns 1 on success or 0 on error
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| 128 | */
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| 129 | int ssl3_cbc_digest_record(const EVP_MD_CTX *ctx,
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| 130 | unsigned char *md_out,
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| 131 | size_t *md_out_size,
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| 132 | const unsigned char header[13],
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| 133 | const unsigned char *data,
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| 134 | size_t data_plus_mac_size,
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| 135 | size_t data_plus_mac_plus_padding_size,
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| 136 | const unsigned char *mac_secret,
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| 137 | unsigned mac_secret_length, char is_sslv3)
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| 138 | {
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| 139 | union {
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| 140 | double align;
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| 141 | unsigned char c[sizeof(LARGEST_DIGEST_CTX)];
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| 142 | } md_state;
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| 143 | void (*md_final_raw) (void *ctx, unsigned char *md_out);
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| 144 | void (*md_transform) (void *ctx, const unsigned char *block);
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| 145 | unsigned md_size, md_block_size = 64;
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| 146 | unsigned sslv3_pad_length = 40, header_length, variance_blocks,
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| 147 | len, max_mac_bytes, num_blocks,
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| 148 | num_starting_blocks, k, mac_end_offset, c, index_a, index_b;
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| 149 | unsigned int bits; /* at most 18 bits */
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| 150 | unsigned char length_bytes[MAX_HASH_BIT_COUNT_BYTES];
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| 151 | /* hmac_pad is the masked HMAC key. */
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| 152 | unsigned char hmac_pad[MAX_HASH_BLOCK_SIZE];
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| 153 | unsigned char first_block[MAX_HASH_BLOCK_SIZE];
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| 154 | unsigned char mac_out[EVP_MAX_MD_SIZE];
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| 155 | unsigned i, j, md_out_size_u;
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| 156 | EVP_MD_CTX *md_ctx = NULL;
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| 157 | /*
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| 158 | * mdLengthSize is the number of bytes in the length field that
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| 159 | * terminates * the hash.
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| 160 | */
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| 161 | unsigned md_length_size = 8;
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| 162 | char length_is_big_endian = 1;
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| 163 | int ret;
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| 164 |
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| 165 | /*
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| 166 | * This is a, hopefully redundant, check that allows us to forget about
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| 167 | * many possible overflows later in this function.
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| 168 | */
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| 169 | OPENSSL_assert(data_plus_mac_plus_padding_size < 1024 * 1024);
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| 170 |
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| 171 | switch (EVP_MD_CTX_type(ctx)) {
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| 172 | case NID_md5:
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| 173 | if (MD5_Init((MD5_CTX *)md_state.c) <= 0)
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| 174 | return 0;
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| 175 | md_final_raw = tls1_md5_final_raw;
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| 176 | md_transform =
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| 177 | (void (*)(void *ctx, const unsigned char *block))MD5_Transform;
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| 178 | md_size = 16;
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| 179 | sslv3_pad_length = 48;
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| 180 | length_is_big_endian = 0;
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| 181 | break;
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| 182 | case NID_sha1:
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| 183 | if (SHA1_Init((SHA_CTX *)md_state.c) <= 0)
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| 184 | return 0;
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| 185 | md_final_raw = tls1_sha1_final_raw;
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| 186 | md_transform =
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| 187 | (void (*)(void *ctx, const unsigned char *block))SHA1_Transform;
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| 188 | md_size = 20;
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| 189 | break;
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| 190 | case NID_sha224:
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| 191 | if (SHA224_Init((SHA256_CTX *)md_state.c) <= 0)
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| 192 | return 0;
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| 193 | md_final_raw = tls1_sha256_final_raw;
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| 194 | md_transform =
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| 195 | (void (*)(void *ctx, const unsigned char *block))SHA256_Transform;
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| 196 | md_size = 224 / 8;
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| 197 | break;
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| 198 | case NID_sha256:
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| 199 | if (SHA256_Init((SHA256_CTX *)md_state.c) <= 0)
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| 200 | return 0;
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| 201 | md_final_raw = tls1_sha256_final_raw;
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| 202 | md_transform =
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| 203 | (void (*)(void *ctx, const unsigned char *block))SHA256_Transform;
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| 204 | md_size = 32;
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| 205 | break;
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| 206 | case NID_sha384:
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| 207 | if (SHA384_Init((SHA512_CTX *)md_state.c) <= 0)
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| 208 | return 0;
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| 209 | md_final_raw = tls1_sha512_final_raw;
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| 210 | md_transform =
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| 211 | (void (*)(void *ctx, const unsigned char *block))SHA512_Transform;
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| 212 | md_size = 384 / 8;
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| 213 | md_block_size = 128;
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| 214 | md_length_size = 16;
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| 215 | break;
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| 216 | case NID_sha512:
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| 217 | if (SHA512_Init((SHA512_CTX *)md_state.c) <= 0)
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| 218 | return 0;
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| 219 | md_final_raw = tls1_sha512_final_raw;
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| 220 | md_transform =
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| 221 | (void (*)(void *ctx, const unsigned char *block))SHA512_Transform;
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| 222 | md_size = 64;
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| 223 | md_block_size = 128;
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| 224 | md_length_size = 16;
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| 225 | break;
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| 226 | default:
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| 227 | /*
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| 228 | * ssl3_cbc_record_digest_supported should have been called first to
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| 229 | * check that the hash function is supported.
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| 230 | */
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| 231 | OPENSSL_assert(0);
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| 232 | if (md_out_size)
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| 233 | *md_out_size = 0;
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| 234 | return 0;
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| 235 | }
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| 236 |
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| 237 | OPENSSL_assert(md_length_size <= MAX_HASH_BIT_COUNT_BYTES);
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| 238 | OPENSSL_assert(md_block_size <= MAX_HASH_BLOCK_SIZE);
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| 239 | OPENSSL_assert(md_size <= EVP_MAX_MD_SIZE);
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| 240 |
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| 241 | header_length = 13;
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| 242 | if (is_sslv3) {
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| 243 | header_length = mac_secret_length + sslv3_pad_length + 8 /* sequence
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| 244 | * number */ +
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| 245 | 1 /* record type */ +
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| 246 | 2 /* record length */ ;
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| 247 | }
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| 248 |
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| 249 | /*
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| 250 | * variance_blocks is the number of blocks of the hash that we have to
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| 251 | * calculate in constant time because they could be altered by the
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| 252 | * padding value. In SSLv3, the padding must be minimal so the end of
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| 253 | * the plaintext varies by, at most, 15+20 = 35 bytes. (We conservatively
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| 254 | * assume that the MAC size varies from 0..20 bytes.) In case the 9 bytes
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| 255 | * of hash termination (0x80 + 64-bit length) don't fit in the final
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| 256 | * block, we say that the final two blocks can vary based on the padding.
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| 257 | * TLSv1 has MACs up to 48 bytes long (SHA-384) and the padding is not
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| 258 | * required to be minimal. Therefore we say that the final six blocks can
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| 259 | * vary based on the padding. Later in the function, if the message is
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| 260 | * short and there obviously cannot be this many blocks then
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| 261 | * variance_blocks can be reduced.
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| 262 | */
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| 263 | variance_blocks = is_sslv3 ? 2 : 6;
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| 264 | /*
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| 265 | * From now on we're dealing with the MAC, which conceptually has 13
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| 266 | * bytes of `header' before the start of the data (TLS) or 71/75 bytes
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| 267 | * (SSLv3)
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| 268 | */
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| 269 | len = data_plus_mac_plus_padding_size + header_length;
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| 270 | /*
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| 271 | * max_mac_bytes contains the maximum bytes of bytes in the MAC,
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| 272 | * including * |header|, assuming that there's no padding.
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| 273 | */
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| 274 | max_mac_bytes = len - md_size - 1;
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| 275 | /* num_blocks is the maximum number of hash blocks. */
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| 276 | num_blocks =
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| 277 | (max_mac_bytes + 1 + md_length_size + md_block_size -
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| 278 | 1) / md_block_size;
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| 279 | /*
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| 280 | * In order to calculate the MAC in constant time we have to handle the
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| 281 | * final blocks specially because the padding value could cause the end
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| 282 | * to appear somewhere in the final |variance_blocks| blocks and we can't
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| 283 | * leak where. However, |num_starting_blocks| worth of data can be hashed
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| 284 | * right away because no padding value can affect whether they are
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| 285 | * plaintext.
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| 286 | */
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| 287 | num_starting_blocks = 0;
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| 288 | /*
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| 289 | * k is the starting byte offset into the conceptual header||data where
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| 290 | * we start processing.
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| 291 | */
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| 292 | k = 0;
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| 293 | /*
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| 294 | * mac_end_offset is the index just past the end of the data to be MACed.
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| 295 | */
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| 296 | mac_end_offset = data_plus_mac_size + header_length - md_size;
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| 297 | /*
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| 298 | * c is the index of the 0x80 byte in the final hash block that contains
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| 299 | * application data.
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| 300 | */
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| 301 | c = mac_end_offset % md_block_size;
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| 302 | /*
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| 303 | * index_a is the hash block number that contains the 0x80 terminating
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| 304 | * value.
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| 305 | */
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| 306 | index_a = mac_end_offset / md_block_size;
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| 307 | /*
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| 308 | * index_b is the hash block number that contains the 64-bit hash length,
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| 309 | * in bits.
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| 310 | */
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| 311 | index_b = (mac_end_offset + md_length_size) / md_block_size;
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| 312 | /*
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| 313 | * bits is the hash-length in bits. It includes the additional hash block
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| 314 | * for the masked HMAC key, or whole of |header| in the case of SSLv3.
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| 315 | */
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| 316 |
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| 317 | /*
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| 318 | * For SSLv3, if we're going to have any starting blocks then we need at
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| 319 | * least two because the header is larger than a single block.
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| 320 | */
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| 321 | if (num_blocks > variance_blocks + (is_sslv3 ? 1 : 0)) {
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| 322 | num_starting_blocks = num_blocks - variance_blocks;
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| 323 | k = md_block_size * num_starting_blocks;
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| 324 | }
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| 325 |
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| 326 | bits = 8 * mac_end_offset;
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| 327 | if (!is_sslv3) {
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| 328 | /*
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| 329 | * Compute the initial HMAC block. For SSLv3, the padding and secret
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| 330 | * bytes are included in |header| because they take more than a
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| 331 | * single block.
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| 332 | */
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| 333 | bits += 8 * md_block_size;
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| 334 | memset(hmac_pad, 0, md_block_size);
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| 335 | OPENSSL_assert(mac_secret_length <= sizeof(hmac_pad));
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| 336 | memcpy(hmac_pad, mac_secret, mac_secret_length);
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| 337 | for (i = 0; i < md_block_size; i++)
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| 338 | hmac_pad[i] ^= 0x36;
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| 339 |
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| 340 | md_transform(md_state.c, hmac_pad);
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| 341 | }
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| 342 |
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| 343 | if (length_is_big_endian) {
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| 344 | memset(length_bytes, 0, md_length_size - 4);
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| 345 | length_bytes[md_length_size - 4] = (unsigned char)(bits >> 24);
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| 346 | length_bytes[md_length_size - 3] = (unsigned char)(bits >> 16);
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| 347 | length_bytes[md_length_size - 2] = (unsigned char)(bits >> 8);
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| 348 | length_bytes[md_length_size - 1] = (unsigned char)bits;
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| 349 | } else {
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| 350 | memset(length_bytes, 0, md_length_size);
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| 351 | length_bytes[md_length_size - 5] = (unsigned char)(bits >> 24);
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| 352 | length_bytes[md_length_size - 6] = (unsigned char)(bits >> 16);
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| 353 | length_bytes[md_length_size - 7] = (unsigned char)(bits >> 8);
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| 354 | length_bytes[md_length_size - 8] = (unsigned char)bits;
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| 355 | }
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| 356 |
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| 357 | if (k > 0) {
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| 358 | if (is_sslv3) {
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| 359 | unsigned overhang;
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| 360 |
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| 361 | /*
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| 362 | * The SSLv3 header is larger than a single block. overhang is
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| 363 | * the number of bytes beyond a single block that the header
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| 364 | * consumes: either 7 bytes (SHA1) or 11 bytes (MD5). There are no
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| 365 | * ciphersuites in SSLv3 that are not SHA1 or MD5 based and
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| 366 | * therefore we can be confident that the header_length will be
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| 367 | * greater than |md_block_size|. However we add a sanity check just
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| 368 | * in case
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| 369 | */
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| 370 | if (header_length <= md_block_size) {
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| 371 | /* Should never happen */
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| 372 | return 0;
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| 373 | }
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| 374 | overhang = header_length - md_block_size;
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| 375 | md_transform(md_state.c, header);
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| 376 | memcpy(first_block, header + md_block_size, overhang);
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| 377 | memcpy(first_block + overhang, data, md_block_size - overhang);
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| 378 | md_transform(md_state.c, first_block);
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| 379 | for (i = 1; i < k / md_block_size - 1; i++)
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| 380 | md_transform(md_state.c, data + md_block_size * i - overhang);
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| 381 | } else {
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| 382 | /* k is a multiple of md_block_size. */
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| 383 | memcpy(first_block, header, 13);
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| 384 | memcpy(first_block + 13, data, md_block_size - 13);
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| 385 | md_transform(md_state.c, first_block);
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| 386 | for (i = 1; i < k / md_block_size; i++)
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| 387 | md_transform(md_state.c, data + md_block_size * i - 13);
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| 388 | }
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| 389 | }
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| 390 |
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| 391 | memset(mac_out, 0, sizeof(mac_out));
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| 392 |
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| 393 | /*
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| 394 | * We now process the final hash blocks. For each block, we construct it
|
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| 395 | * in constant time. If the |i==index_a| then we'll include the 0x80
|
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| 396 | * bytes and zero pad etc. For each block we selectively copy it, in
|
---|
| 397 | * constant time, to |mac_out|.
|
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| 398 | */
|
---|
| 399 | for (i = num_starting_blocks; i <= num_starting_blocks + variance_blocks;
|
---|
| 400 | i++) {
|
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| 401 | unsigned char block[MAX_HASH_BLOCK_SIZE];
|
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| 402 | unsigned char is_block_a = constant_time_eq_8(i, index_a);
|
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| 403 | unsigned char is_block_b = constant_time_eq_8(i, index_b);
|
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| 404 | for (j = 0; j < md_block_size; j++) {
|
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| 405 | unsigned char b = 0, is_past_c, is_past_cp1;
|
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| 406 | if (k < header_length)
|
---|
| 407 | b = header[k];
|
---|
| 408 | else if (k < data_plus_mac_plus_padding_size + header_length)
|
---|
| 409 | b = data[k - header_length];
|
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| 410 | k++;
|
---|
| 411 |
|
---|
| 412 | is_past_c = is_block_a & constant_time_ge_8(j, c);
|
---|
| 413 | is_past_cp1 = is_block_a & constant_time_ge_8(j, c + 1);
|
---|
| 414 | /*
|
---|
| 415 | * If this is the block containing the end of the application
|
---|
| 416 | * data, and we are at the offset for the 0x80 value, then
|
---|
| 417 | * overwrite b with 0x80.
|
---|
| 418 | */
|
---|
| 419 | b = constant_time_select_8(is_past_c, 0x80, b);
|
---|
| 420 | /*
|
---|
| 421 | * If this the the block containing the end of the application
|
---|
| 422 | * data and we're past the 0x80 value then just write zero.
|
---|
| 423 | */
|
---|
| 424 | b = b & ~is_past_cp1;
|
---|
| 425 | /*
|
---|
| 426 | * If this is index_b (the final block), but not index_a (the end
|
---|
| 427 | * of the data), then the 64-bit length didn't fit into index_a
|
---|
| 428 | * and we're having to add an extra block of zeros.
|
---|
| 429 | */
|
---|
| 430 | b &= ~is_block_b | is_block_a;
|
---|
| 431 |
|
---|
| 432 | /*
|
---|
| 433 | * The final bytes of one of the blocks contains the length.
|
---|
| 434 | */
|
---|
| 435 | if (j >= md_block_size - md_length_size) {
|
---|
| 436 | /* If this is index_b, write a length byte. */
|
---|
| 437 | b = constant_time_select_8(is_block_b,
|
---|
| 438 | length_bytes[j -
|
---|
| 439 | (md_block_size -
|
---|
| 440 | md_length_size)], b);
|
---|
| 441 | }
|
---|
| 442 | block[j] = b;
|
---|
| 443 | }
|
---|
| 444 |
|
---|
| 445 | md_transform(md_state.c, block);
|
---|
| 446 | md_final_raw(md_state.c, block);
|
---|
| 447 | /* If this is index_b, copy the hash value to |mac_out|. */
|
---|
| 448 | for (j = 0; j < md_size; j++)
|
---|
| 449 | mac_out[j] |= block[j] & is_block_b;
|
---|
| 450 | }
|
---|
| 451 |
|
---|
| 452 | md_ctx = EVP_MD_CTX_new();
|
---|
| 453 | if (md_ctx == NULL)
|
---|
| 454 | goto err;
|
---|
| 455 | if (EVP_DigestInit_ex(md_ctx, EVP_MD_CTX_md(ctx), NULL /* engine */ ) <= 0)
|
---|
| 456 | goto err;
|
---|
| 457 | if (is_sslv3) {
|
---|
| 458 | /* We repurpose |hmac_pad| to contain the SSLv3 pad2 block. */
|
---|
| 459 | memset(hmac_pad, 0x5c, sslv3_pad_length);
|
---|
| 460 |
|
---|
| 461 | if (EVP_DigestUpdate(md_ctx, mac_secret, mac_secret_length) <= 0
|
---|
| 462 | || EVP_DigestUpdate(md_ctx, hmac_pad, sslv3_pad_length) <= 0
|
---|
| 463 | || EVP_DigestUpdate(md_ctx, mac_out, md_size) <= 0)
|
---|
| 464 | goto err;
|
---|
| 465 | } else {
|
---|
| 466 | /* Complete the HMAC in the standard manner. */
|
---|
| 467 | for (i = 0; i < md_block_size; i++)
|
---|
| 468 | hmac_pad[i] ^= 0x6a;
|
---|
| 469 |
|
---|
| 470 | if (EVP_DigestUpdate(md_ctx, hmac_pad, md_block_size) <= 0
|
---|
| 471 | || EVP_DigestUpdate(md_ctx, mac_out, md_size) <= 0)
|
---|
| 472 | goto err;
|
---|
| 473 | }
|
---|
| 474 | ret = EVP_DigestFinal(md_ctx, md_out, &md_out_size_u);
|
---|
| 475 | if (ret && md_out_size)
|
---|
| 476 | *md_out_size = md_out_size_u;
|
---|
| 477 | EVP_MD_CTX_free(md_ctx);
|
---|
| 478 |
|
---|
| 479 | return 1;
|
---|
| 480 | err:
|
---|
| 481 | EVP_MD_CTX_free(md_ctx);
|
---|
| 482 | return 0;
|
---|
| 483 | }
|
---|
| 484 |
|
---|
| 485 | /*
|
---|
| 486 | * Due to the need to use EVP in FIPS mode we can't reimplement digests but
|
---|
| 487 | * we can ensure the number of blocks processed is equal for all cases by
|
---|
| 488 | * digesting additional data.
|
---|
| 489 | */
|
---|
| 490 |
|
---|
| 491 | int tls_fips_digest_extra(const EVP_CIPHER_CTX *cipher_ctx,
|
---|
| 492 | EVP_MD_CTX *mac_ctx, const unsigned char *data,
|
---|
| 493 | size_t data_len, size_t orig_len)
|
---|
| 494 | {
|
---|
| 495 | size_t block_size, digest_pad, blocks_data, blocks_orig;
|
---|
| 496 | if (EVP_CIPHER_CTX_mode(cipher_ctx) != EVP_CIPH_CBC_MODE)
|
---|
| 497 | return 1;
|
---|
| 498 | block_size = EVP_MD_CTX_block_size(mac_ctx);
|
---|
| 499 | /*-
|
---|
| 500 | * We are in FIPS mode if we get this far so we know we have only SHA*
|
---|
| 501 | * digests and TLS to deal with.
|
---|
| 502 | * Minimum digest padding length is 17 for SHA384/SHA512 and 9
|
---|
| 503 | * otherwise.
|
---|
| 504 | * Additional header is 13 bytes. To get the number of digest blocks
|
---|
| 505 | * processed round up the amount of data plus padding to the nearest
|
---|
| 506 | * block length. Block length is 128 for SHA384/SHA512 and 64 otherwise.
|
---|
| 507 | * So we have:
|
---|
| 508 | * blocks = (payload_len + digest_pad + 13 + block_size - 1)/block_size
|
---|
| 509 | * equivalently:
|
---|
| 510 | * blocks = (payload_len + digest_pad + 12)/block_size + 1
|
---|
| 511 | * HMAC adds a constant overhead.
|
---|
| 512 | * We're ultimately only interested in differences so this becomes
|
---|
| 513 | * blocks = (payload_len + 29)/128
|
---|
| 514 | * for SHA384/SHA512 and
|
---|
| 515 | * blocks = (payload_len + 21)/64
|
---|
| 516 | * otherwise.
|
---|
| 517 | */
|
---|
| 518 | digest_pad = block_size == 64 ? 21 : 29;
|
---|
| 519 | blocks_orig = (orig_len + digest_pad) / block_size;
|
---|
| 520 | blocks_data = (data_len + digest_pad) / block_size;
|
---|
| 521 | /*
|
---|
| 522 | * MAC enough blocks to make up the difference between the original and
|
---|
| 523 | * actual lengths plus one extra block to ensure this is never a no op.
|
---|
| 524 | * The "data" pointer should always have enough space to perform this
|
---|
| 525 | * operation as it is large enough for a maximum length TLS buffer.
|
---|
| 526 | */
|
---|
| 527 | return EVP_DigestSignUpdate(mac_ctx, data,
|
---|
| 528 | (blocks_orig - blocks_data + 1) * block_size);
|
---|
| 529 | }
|
---|