- /* ====================================================================
- * Copyright (c) 2012 The OpenSSL Project. All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions
- * are met:
- *
- * 1. Redistributions of source code must retain the above copyright
- * notice, this list of conditions and the following disclaimer.
- *
- * 2. Redistributions in binary form must reproduce the above copyright
- * notice, this list of conditions and the following disclaimer in
- * the documentation and/or other materials provided with the
- * distribution.
- *
- * 3. All advertising materials mentioning features or use of this
- * software must display the following acknowledgment:
- * "This product includes software developed by the OpenSSL Project
- * for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
- *
- * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
- * endorse or promote products derived from this software without
- * prior written permission. For written permission, please contact
- * openssl-core@openssl.org.
- *
- * 5. Products derived from this software may not be called "OpenSSL"
- * nor may "OpenSSL" appear in their names without prior written
- * permission of the OpenSSL Project.
- *
- * 6. Redistributions of any form whatsoever must retain the following
- * acknowledgment:
- * "This product includes software developed by the OpenSSL Project
- * for use in the OpenSSL Toolkit (http://www.openssl.org/)"
- *
- * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
- * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
- * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
- * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR
- * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
- * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
- * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
- * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
- * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
- * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
- * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
- * OF THE POSSIBILITY OF SUCH DAMAGE.
- * ====================================================================
- *
- * This product includes cryptographic software written by Eric Young
- * (eay@cryptsoft.com). This product includes software written by Tim
- * Hudson (tjh@cryptsoft.com). */
-
- #include <assert.h>
- #include <string.h>
-
- #include <openssl/digest.h>
- #include <openssl/nid.h>
- #include <openssl/sha.h>
-
- #include "../internal.h"
- #include "internal.h"
-
-
- /* MAX_HASH_BIT_COUNT_BYTES is the maximum number of bytes in the hash's length
- * field. (SHA-384/512 have 128-bit length.) */
- #define MAX_HASH_BIT_COUNT_BYTES 16
-
- /* MAX_HASH_BLOCK_SIZE is the maximum hash block size that we'll support.
- * Currently SHA-384/512 has a 128-byte block size and that's the largest
- * supported by TLS.) */
- #define MAX_HASH_BLOCK_SIZE 128
-
- int EVP_tls_cbc_remove_padding(crypto_word_t *out_padding_ok, size_t *out_len,
- const uint8_t *in, size_t in_len,
- size_t block_size, size_t mac_size) {
- const size_t overhead = 1 /* padding length byte */ + mac_size;
-
- /* These lengths are all public so we can test them in non-constant time. */
- if (overhead > in_len) {
- return 0;
- }
-
- size_t padding_length = in[in_len - 1];
-
- crypto_word_t good = constant_time_ge_w(in_len, overhead + padding_length);
- /* The padding consists of a length byte at the end of the record and
- * then that many bytes of padding, all with the same value as the
- * length byte. Thus, with the length byte included, there are i+1
- * bytes of padding.
- *
- * We can't check just |padding_length+1| bytes because that leaks
- * decrypted information. Therefore we always have to check the maximum
- * amount of padding possible. (Again, the length of the record is
- * public information so we can use it.) */
- size_t to_check = 256; /* maximum amount of padding, inc length byte. */
- if (to_check > in_len) {
- to_check = in_len;
- }
-
- for (size_t i = 0; i < to_check; i++) {
- uint8_t mask = constant_time_ge_8(padding_length, i);
- uint8_t b = in[in_len - 1 - i];
- /* The final |padding_length+1| bytes should all have the value
- * |padding_length|. Therefore the XOR should be zero. */
- good &= ~(mask & (padding_length ^ b));
- }
-
- /* If any of the final |padding_length+1| bytes had the wrong value,
- * one or more of the lower eight bits of |good| will be cleared. */
- good = constant_time_eq_w(0xff, good & 0xff);
-
- /* Always treat |padding_length| as zero on error. If, assuming block size of
- * 16, a padding of [<15 arbitrary bytes> 15] treated |padding_length| as 16
- * and returned -1, distinguishing good MAC and bad padding from bad MAC and
- * bad padding would give POODLE's padding oracle. */
- padding_length = good & (padding_length + 1);
- *out_len = in_len - padding_length;
- *out_padding_ok = good;
- return 1;
- }
-
- void EVP_tls_cbc_copy_mac(uint8_t *out, size_t md_size, const uint8_t *in,
- size_t in_len, size_t orig_len) {
- uint8_t rotated_mac1[EVP_MAX_MD_SIZE], rotated_mac2[EVP_MAX_MD_SIZE];
- uint8_t *rotated_mac = rotated_mac1;
- uint8_t *rotated_mac_tmp = rotated_mac2;
-
- /* mac_end is the index of |in| just after the end of the MAC. */
- size_t mac_end = in_len;
- size_t mac_start = mac_end - md_size;
-
- assert(orig_len >= in_len);
- assert(in_len >= md_size);
- assert(md_size <= EVP_MAX_MD_SIZE);
-
- /* scan_start contains the number of bytes that we can ignore because
- * the MAC's position can only vary by 255 bytes. */
- size_t scan_start = 0;
- /* This information is public so it's safe to branch based on it. */
- if (orig_len > md_size + 255 + 1) {
- scan_start = orig_len - (md_size + 255 + 1);
- }
-
- size_t rotate_offset = 0;
- uint8_t mac_started = 0;
- OPENSSL_memset(rotated_mac, 0, md_size);
- for (size_t i = scan_start, j = 0; i < orig_len; i++, j++) {
- if (j >= md_size) {
- j -= md_size;
- }
- crypto_word_t is_mac_start = constant_time_eq_w(i, mac_start);
- mac_started |= is_mac_start;
- uint8_t mac_ended = constant_time_ge_8(i, mac_end);
- rotated_mac[j] |= in[i] & mac_started & ~mac_ended;
- /* Save the offset that |mac_start| is mapped to. */
- rotate_offset |= j & is_mac_start;
- }
-
- /* Now rotate the MAC. We rotate in log(md_size) steps, one for each bit
- * position. */
- for (size_t offset = 1; offset < md_size; offset <<= 1, rotate_offset >>= 1) {
- /* Rotate by |offset| iff the corresponding bit is set in
- * |rotate_offset|, placing the result in |rotated_mac_tmp|. */
- const uint8_t skip_rotate = (rotate_offset & 1) - 1;
- for (size_t i = 0, j = offset; i < md_size; i++, j++) {
- if (j >= md_size) {
- j -= md_size;
- }
- rotated_mac_tmp[i] =
- constant_time_select_8(skip_rotate, rotated_mac[i], rotated_mac[j]);
- }
-
- /* Swap pointers so |rotated_mac| contains the (possibly) rotated value.
- * Note the number of iterations and thus the identity of these pointers is
- * public information. */
- uint8_t *tmp = rotated_mac;
- rotated_mac = rotated_mac_tmp;
- rotated_mac_tmp = tmp;
- }
-
- OPENSSL_memcpy(out, rotated_mac, md_size);
- }
-
- /* u32toBE serialises an unsigned, 32-bit number (n) as four bytes at (p) in
- * big-endian order. The value of p is advanced by four. */
- #define u32toBE(n, p) \
- do { \
- *((p)++) = (uint8_t)((n) >> 24); \
- *((p)++) = (uint8_t)((n) >> 16); \
- *((p)++) = (uint8_t)((n) >> 8); \
- *((p)++) = (uint8_t)((n)); \
- } while (0)
-
- /* u64toBE serialises an unsigned, 64-bit number (n) as eight bytes at (p) in
- * big-endian order. The value of p is advanced by eight. */
- #define u64toBE(n, p) \
- do { \
- *((p)++) = (uint8_t)((n) >> 56); \
- *((p)++) = (uint8_t)((n) >> 48); \
- *((p)++) = (uint8_t)((n) >> 40); \
- *((p)++) = (uint8_t)((n) >> 32); \
- *((p)++) = (uint8_t)((n) >> 24); \
- *((p)++) = (uint8_t)((n) >> 16); \
- *((p)++) = (uint8_t)((n) >> 8); \
- *((p)++) = (uint8_t)((n)); \
- } while (0)
-
- typedef union {
- SHA_CTX sha1;
- SHA256_CTX sha256;
- SHA512_CTX sha512;
- } HASH_CTX;
-
- static void tls1_sha1_transform(HASH_CTX *ctx, const uint8_t *block) {
- SHA1_Transform(&ctx->sha1, block);
- }
-
- static void tls1_sha256_transform(HASH_CTX *ctx, const uint8_t *block) {
- SHA256_Transform(&ctx->sha256, block);
- }
-
- static void tls1_sha512_transform(HASH_CTX *ctx, const uint8_t *block) {
- SHA512_Transform(&ctx->sha512, block);
- }
-
- /* 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_sha1_final_raw(HASH_CTX *ctx, uint8_t *md_out) {
- SHA_CTX *sha1 = &ctx->sha1;
- u32toBE(sha1->h[0], md_out);
- u32toBE(sha1->h[1], md_out);
- u32toBE(sha1->h[2], md_out);
- u32toBE(sha1->h[3], md_out);
- u32toBE(sha1->h[4], md_out);
- }
-
- static void tls1_sha256_final_raw(HASH_CTX *ctx, uint8_t *md_out) {
- SHA256_CTX *sha256 = &ctx->sha256;
- for (unsigned i = 0; i < 8; i++) {
- u32toBE(sha256->h[i], md_out);
- }
- }
-
- static void tls1_sha512_final_raw(HASH_CTX *ctx, uint8_t *md_out) {
- SHA512_CTX *sha512 = &ctx->sha512;
- for (unsigned i = 0; i < 8; i++) {
- u64toBE(sha512->h[i], md_out);
- }
- }
-
- int EVP_tls_cbc_record_digest_supported(const EVP_MD *md) {
- switch (EVP_MD_type(md)) {
- case NID_sha1:
- case NID_sha256:
- case NID_sha384:
- return 1;
-
- default:
- return 0;
- }
- }
-
- int EVP_tls_cbc_digest_record(const EVP_MD *md, uint8_t *md_out,
- size_t *md_out_size, const uint8_t header[13],
- const uint8_t *data, size_t data_plus_mac_size,
- size_t data_plus_mac_plus_padding_size,
- const uint8_t *mac_secret,
- unsigned mac_secret_length) {
- HASH_CTX md_state;
- void (*md_final_raw)(HASH_CTX *ctx, uint8_t *md_out);
- void (*md_transform)(HASH_CTX *ctx, const uint8_t *block);
- unsigned md_size, md_block_size = 64;
- /* md_length_size is the number of bytes in the length field that terminates
- * the hash. */
- unsigned md_length_size = 8;
-
- /* Bound the acceptable input so we can forget about many possible overflows
- * later in this function. This is redundant with the record size limits in
- * TLS. */
- if (data_plus_mac_plus_padding_size >= 1024 * 1024) {
- assert(0);
- return 0;
- }
-
- switch (EVP_MD_type(md)) {
- case NID_sha1:
- SHA1_Init(&md_state.sha1);
- md_final_raw = tls1_sha1_final_raw;
- md_transform = tls1_sha1_transform;
- md_size = SHA_DIGEST_LENGTH;
- break;
-
- case NID_sha256:
- SHA256_Init(&md_state.sha256);
- md_final_raw = tls1_sha256_final_raw;
- md_transform = tls1_sha256_transform;
- md_size = SHA256_DIGEST_LENGTH;
- break;
-
- case NID_sha384:
- SHA384_Init(&md_state.sha512);
- md_final_raw = tls1_sha512_final_raw;
- md_transform = tls1_sha512_transform;
- md_size = SHA384_DIGEST_LENGTH;
- md_block_size = 128;
- md_length_size = 16;
- break;
-
- default:
- /* EVP_tls_cbc_record_digest_supported should have been called first to
- * check that the hash function is supported. */
- assert(0);
- *md_out_size = 0;
- return 0;
- }
-
- assert(md_length_size <= MAX_HASH_BIT_COUNT_BYTES);
- assert(md_block_size <= MAX_HASH_BLOCK_SIZE);
- assert(md_size <= EVP_MAX_MD_SIZE);
-
- static const size_t kHeaderLength = 13;
-
- /* kVarianceBlocks 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.
- *
- * 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. */
- static const size_t kVarianceBlocks = 6;
-
- /* From now on we're dealing with the MAC, which conceptually has 13
- * bytes of `header' before the start of the data. */
- size_t len = data_plus_mac_plus_padding_size + kHeaderLength;
- /* max_mac_bytes contains the maximum bytes of bytes in the MAC, including
- * |header|, assuming that there's no padding. */
- size_t max_mac_bytes = len - md_size - 1;
- /* num_blocks is the maximum number of hash blocks. */
- size_t 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 |kVarianceBlocks| 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. */
- size_t num_starting_blocks = 0;
- /* k is the starting byte offset into the conceptual header||data where
- * we start processing. */
- size_t k = 0;
- /* mac_end_offset is the index just past the end of the data to be
- * MACed. */
- size_t mac_end_offset = data_plus_mac_size + kHeaderLength - md_size;
- /* c is the index of the 0x80 byte in the final hash block that
- * contains application data. */
- size_t c = mac_end_offset % md_block_size;
- /* index_a is the hash block number that contains the 0x80 terminating
- * value. */
- size_t index_a = mac_end_offset / md_block_size;
- /* index_b is the hash block number that contains the 64-bit hash
- * length, in bits. */
- size_t index_b = (mac_end_offset + md_length_size) / md_block_size;
-
- if (num_blocks > kVarianceBlocks) {
- num_starting_blocks = num_blocks - kVarianceBlocks;
- k = md_block_size * num_starting_blocks;
- }
-
- /* bits is the hash-length in bits. It includes the additional hash
- * block for the masked HMAC key. */
- size_t bits = 8 * mac_end_offset; /* at most 18 bits to represent */
-
- /* Compute the initial HMAC block. */
- bits += 8 * md_block_size;
- /* hmac_pad is the masked HMAC key. */
- uint8_t hmac_pad[MAX_HASH_BLOCK_SIZE];
- OPENSSL_memset(hmac_pad, 0, md_block_size);
- assert(mac_secret_length <= sizeof(hmac_pad));
- OPENSSL_memcpy(hmac_pad, mac_secret, mac_secret_length);
- for (size_t i = 0; i < md_block_size; i++) {
- hmac_pad[i] ^= 0x36;
- }
-
- md_transform(&md_state, hmac_pad);
-
- /* The length check means |bits| fits in four bytes. */
- uint8_t length_bytes[MAX_HASH_BIT_COUNT_BYTES];
- OPENSSL_memset(length_bytes, 0, md_length_size - 4);
- length_bytes[md_length_size - 4] = (uint8_t)(bits >> 24);
- length_bytes[md_length_size - 3] = (uint8_t)(bits >> 16);
- length_bytes[md_length_size - 2] = (uint8_t)(bits >> 8);
- length_bytes[md_length_size - 1] = (uint8_t)bits;
-
- if (k > 0) {
- /* k is a multiple of md_block_size. */
- uint8_t first_block[MAX_HASH_BLOCK_SIZE];
- OPENSSL_memcpy(first_block, header, 13);
- OPENSSL_memcpy(first_block + 13, data, md_block_size - 13);
- md_transform(&md_state, first_block);
- for (size_t i = 1; i < k / md_block_size; i++) {
- md_transform(&md_state, data + md_block_size * i - 13);
- }
- }
-
- uint8_t mac_out[EVP_MAX_MD_SIZE];
- OPENSSL_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 (size_t i = num_starting_blocks;
- i <= num_starting_blocks + kVarianceBlocks; i++) {
- uint8_t block[MAX_HASH_BLOCK_SIZE];
- uint8_t is_block_a = constant_time_eq_8(i, index_a);
- uint8_t is_block_b = constant_time_eq_8(i, index_b);
- for (size_t j = 0; j < md_block_size; j++) {
- uint8_t b = 0;
- if (k < kHeaderLength) {
- b = header[k];
- } else if (k < data_plus_mac_plus_padding_size + kHeaderLength) {
- b = data[k - kHeaderLength];
- }
- k++;
-
- uint8_t is_past_c = is_block_a & constant_time_ge_8(j, c);
- uint8_t 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, block);
- md_final_raw(&md_state, block);
- /* If this is index_b, copy the hash value to |mac_out|. */
- for (size_t j = 0; j < md_size; j++) {
- mac_out[j] |= block[j] & is_block_b;
- }
- }
-
- EVP_MD_CTX md_ctx;
- EVP_MD_CTX_init(&md_ctx);
- if (!EVP_DigestInit_ex(&md_ctx, md, NULL /* engine */)) {
- EVP_MD_CTX_cleanup(&md_ctx);
- return 0;
- }
-
- /* Complete the HMAC in the standard manner. */
- for (size_t i = 0; i < md_block_size; i++) {
- hmac_pad[i] ^= 0x6a;
- }
-
- EVP_DigestUpdate(&md_ctx, hmac_pad, md_block_size);
- EVP_DigestUpdate(&md_ctx, mac_out, md_size);
- unsigned md_out_size_u;
- EVP_DigestFinal(&md_ctx, md_out, &md_out_size_u);
- *md_out_size = md_out_size_u;
- EVP_MD_CTX_cleanup(&md_ctx);
-
- return 1;
- }
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