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- /* ====================================================================
- * 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"
-
-
- /* TODO(davidben): unsigned should be size_t. The various constant_time
- * functions need to be switched to size_t. */
-
- /* 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(unsigned *out_padding_ok, unsigned *out_len,
- const uint8_t *in, unsigned in_len,
- unsigned block_size, unsigned mac_size) {
- unsigned padding_length, good, to_check, i;
- const unsigned overhead = 1 /* padding length byte */ + mac_size;
-
- /* These lengths are all public so we can test them in non-constant time. */
- if (overhead > in_len) {
- return 0;
- }
-
- padding_length = in[in_len - 1];
-
- good = constant_time_ge(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.) */
- to_check = 256; /* maximum amount of padding, inc length byte. */
- if (to_check > in_len) {
- to_check = in_len;
- }
-
- for (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(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, unsigned md_size,
- const uint8_t *in, unsigned in_len,
- unsigned 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. */
- unsigned mac_end = in_len;
- unsigned mac_start = mac_end - md_size;
- /* scan_start contains the number of bytes that we can ignore because
- * the MAC's position can only vary by 255 bytes. */
- unsigned scan_start = 0;
- unsigned i, j;
- unsigned rotate_offset;
-
- assert(orig_len >= in_len);
- assert(in_len >= md_size);
- assert(md_size <= EVP_MAX_MD_SIZE);
-
- /* 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);
- }
-
- /* Ideally the next statement would be:
- *
- * rotate_offset = (mac_start - scan_start) % md_size;
- *
- * However, division is not a constant-time operation (at least on Intel
- * chips). Thus we enumerate the possible values of md_size and handle each
- * separately. The value of |md_size| is public information (it's determined
- * by the cipher suite in the ServerHello) so our timing can vary based on
- * its value. */
-
- rotate_offset = mac_start - scan_start;
- /* rotate_offset can be, at most, 255 (bytes of padding) + 1 (padding length)
- * + md_size = 256 + 48 (since SHA-384 is the largest hash) = 304. */
- assert(rotate_offset <= 304);
-
- /* Below is an SMT-LIB2 verification that the Barrett reductions below are
- * correct within this range:
- *
- * (define-fun barrett (
- * (x (_ BitVec 32))
- * (mul (_ BitVec 32))
- * (shift (_ BitVec 32))
- * (divisor (_ BitVec 32)) ) (_ BitVec 32)
- * (let ((q (bvsub x (bvmul divisor (bvlshr (bvmul x mul) shift))) ))
- * (ite (bvuge q divisor)
- * (bvsub q divisor)
- * q)))
- *
- * (declare-fun x () (_ BitVec 32))
- *
- * (assert (or
- * (let (
- * (divisor (_ bv20 32))
- * (mul (_ bv25 32))
- * (shift (_ bv9 32))
- * (limit (_ bv853 32)))
- *
- * (and (bvule x limit) (not (= (bvurem x divisor)
- * (barrett x mul shift divisor)))))
- *
- * (let (
- * (divisor (_ bv48 32))
- * (mul (_ bv10 32))
- * (shift (_ bv9 32))
- * (limit (_ bv768 32)))
- *
- * (and (bvule x limit) (not (= (bvurem x divisor)
- * (barrett x mul shift divisor)))))
- * ))
- *
- * (check-sat)
- * (get-model)
- */
-
- if (md_size == 16) {
- rotate_offset &= 15;
- } else if (md_size == 20) {
- /* 1/20 is approximated as 25/512 and then Barrett reduction is used.
- * Analytically, this is correct for 0 <= rotate_offset <= 853. */
- unsigned q = (rotate_offset * 25) >> 9;
- rotate_offset -= q * 20;
- rotate_offset -=
- constant_time_select(constant_time_ge(rotate_offset, 20), 20, 0);
- } else if (md_size == 32) {
- rotate_offset &= 31;
- } else if (md_size == 48) {
- /* 1/48 is approximated as 10/512 and then Barrett reduction is used.
- * Analytically, this is correct for 0 <= rotate_offset <= 768. */
- unsigned q = (rotate_offset * 10) >> 9;
- rotate_offset -= q * 48;
- rotate_offset -=
- constant_time_select(constant_time_ge(rotate_offset, 48), 48, 0);
- } else {
- /* This should be impossible therefore this path doesn't run in constant
- * time. */
- assert(0);
- rotate_offset = rotate_offset % md_size;
- }
-
- memset(rotated_mac, 0, md_size);
- for (i = scan_start, j = 0; i < orig_len; i++) {
- uint8_t mac_started = constant_time_ge_8(i, mac_start);
- uint8_t mac_ended = constant_time_ge_8(i, mac_end);
- uint8_t b = in[i];
- rotated_mac[j++] |= b & mac_started & ~mac_ended;
- j &= constant_time_lt(j, md_size);
- }
-
- /* Now rotate the MAC. We rotate in log(md_size) steps, one for each bit
- * position. */
- for (unsigned 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 (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;
- }
-
- 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)
-
- /* 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(void *ctx, uint8_t *md_out) {
- SHA_CTX *sha1 = ctx;
- 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);
- }
- #define LARGEST_DIGEST_CTX SHA_CTX
-
- static void tls1_sha256_final_raw(void *ctx, uint8_t *md_out) {
- SHA256_CTX *sha256 = ctx;
- unsigned i;
-
- for (i = 0; i < 8; i++) {
- u32toBE(sha256->h[i], md_out);
- }
- }
- #undef LARGEST_DIGEST_CTX
- #define LARGEST_DIGEST_CTX SHA256_CTX
-
- static void tls1_sha512_final_raw(void *ctx, uint8_t *md_out) {
- SHA512_CTX *sha512 = ctx;
- unsigned i;
-
- for (i = 0; i < 8; i++) {
- u64toBE(sha512->h[i], md_out);
- }
- }
- #undef LARGEST_DIGEST_CTX
- #define LARGEST_DIGEST_CTX SHA512_CTX
-
- 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) {
- union {
- double align;
- uint8_t c[sizeof(LARGEST_DIGEST_CTX)];
- } md_state;
- void (*md_final_raw)(void *ctx, uint8_t *md_out);
- void (*md_transform)(void *ctx, const uint8_t *block);
- unsigned md_size, md_block_size = 64;
- unsigned len, max_mac_bytes, num_blocks, num_starting_blocks, k,
- mac_end_offset, c, index_a, index_b;
- unsigned int bits; /* at most 18 bits */
- uint8_t length_bytes[MAX_HASH_BIT_COUNT_BYTES];
- /* hmac_pad is the masked HMAC key. */
- uint8_t hmac_pad[MAX_HASH_BLOCK_SIZE];
- uint8_t first_block[MAX_HASH_BLOCK_SIZE];
- uint8_t mac_out[EVP_MAX_MD_SIZE];
- unsigned i, j, md_out_size_u;
- EVP_MD_CTX md_ctx;
- /* mdLengthSize is the number of bytes in the length field that terminates
- * the hash. */
- unsigned md_length_size = 8;
-
- /* This is a, hopefully redundant, check that allows us to forget about
- * many possible overflows later in this function. */
- assert(data_plus_mac_plus_padding_size < 1024 * 1024);
-
- switch (EVP_MD_type(md)) {
- case NID_sha1:
- SHA1_Init((SHA_CTX *)md_state.c);
- md_final_raw = tls1_sha1_final_raw;
- md_transform =
- (void (*)(void *ctx, const uint8_t *block))SHA1_Transform;
- md_size = 20;
- break;
-
- case NID_sha256:
- SHA256_Init((SHA256_CTX *)md_state.c);
- md_final_raw = tls1_sha256_final_raw;
- md_transform =
- (void (*)(void *ctx, const uint8_t *block))SHA256_Transform;
- md_size = 32;
- break;
-
- case NID_sha384:
- SHA384_Init((SHA512_CTX *)md_state.c);
- md_final_raw = tls1_sha512_final_raw;
- md_transform =
- (void (*)(void *ctx, const uint8_t *block))SHA512_Transform;
- md_size = 384 / 8;
- 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 unsigned 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 unsigned kVarianceBlocks = 6;
-
- /* From now on we're dealing with the MAC, which conceptually has 13
- * bytes of `header' before the start of the data. */
- 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. */
- max_mac_bytes = len - md_size - 1;
- /* num_blocks is the maximum number of hash blocks. */
- num_blocks =
- (max_mac_bytes + 1 + md_length_size + md_block_size - 1) / md_block_size;
- /* In order to calculate the MAC in constant time we have to handle
- * the final blocks specially because the padding value could cause the
- * end to appear somewhere in the final |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. */
- num_starting_blocks = 0;
- /* k is the starting byte offset into the conceptual header||data where
- * we start processing. */
- k = 0;
- /* mac_end_offset is the index just past the end of the data to be
- * MACed. */
- mac_end_offset = data_plus_mac_size + kHeaderLength - md_size;
- /* c is the index of the 0x80 byte in the final hash block that
- * contains application data. */
- c = mac_end_offset % md_block_size;
- /* index_a is the hash block number that contains the 0x80 terminating
- * value. */
- index_a = mac_end_offset / md_block_size;
- /* index_b is the hash block number that contains the 64-bit hash
- * length, in bits. */
- index_b = (mac_end_offset + md_length_size) / md_block_size;
- /* bits is the hash-length in bits. It includes the additional hash
- * block for the masked HMAC key. */
-
- if (num_blocks > kVarianceBlocks) {
- num_starting_blocks = num_blocks - kVarianceBlocks;
- k = md_block_size * num_starting_blocks;
- }
-
- bits = 8 * mac_end_offset;
-
- /* Compute the initial HMAC block. */
- bits += 8 * md_block_size;
- memset(hmac_pad, 0, md_block_size);
- assert(mac_secret_length <= sizeof(hmac_pad));
- memcpy(hmac_pad, mac_secret, mac_secret_length);
- for (i = 0; i < md_block_size; i++) {
- hmac_pad[i] ^= 0x36;
- }
-
- md_transform(md_state.c, hmac_pad);
-
- 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. */
- memcpy(first_block, header, 13);
- memcpy(first_block + 13, data, md_block_size - 13);
- md_transform(md_state.c, first_block);
- for (i = 1; i < k / md_block_size; i++) {
- md_transform(md_state.c, data + md_block_size * i - 13);
- }
- }
-
- memset(mac_out, 0, sizeof(mac_out));
-
- /* We now process the final hash blocks. For each block, we construct
- * it in constant time. If the |i==index_a| then we'll include the 0x80
- * bytes and zero pad etc. For each block we selectively copy it, in
- * constant time, to |mac_out|. */
- for (i = num_starting_blocks; i <= num_starting_blocks + 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 (j = 0; j < md_block_size; j++) {
- uint8_t b = 0, is_past_c, is_past_cp1;
- if (k < kHeaderLength) {
- b = header[k];
- } else if (k < data_plus_mac_plus_padding_size + kHeaderLength) {
- b = data[k - kHeaderLength];
- }
- k++;
-
- is_past_c = is_block_a & constant_time_ge_8(j, c);
- is_past_cp1 = is_block_a & constant_time_ge_8(j, c + 1);
- /* If this is the block containing the end of the
- * application data, and we are at the offset for the
- * 0x80 value, then overwrite b with 0x80. */
- b = constant_time_select_8(is_past_c, 0x80, b);
- /* If this the the block containing the end of the
- * application data and we're past the 0x80 value then
- * just write zero. */
- b = b & ~is_past_cp1;
- /* If this is index_b (the final block), but not
- * index_a (the end of the data), then the 64-bit
- * length didn't fit into index_a and we're having to
- * add an extra block of zeros. */
- b &= ~is_block_b | is_block_a;
-
- /* The final bytes of one of the blocks contains the
- * length. */
- if (j >= md_block_size - md_length_size) {
- /* If this is index_b, write a length byte. */
- b = constant_time_select_8(
- is_block_b, length_bytes[j - (md_block_size - md_length_size)], b);
- }
- block[j] = b;
- }
-
- md_transform(md_state.c, block);
- md_final_raw(md_state.c, block);
- /* If this is index_b, copy the hash value to |mac_out|. */
- for (j = 0; j < md_size; j++) {
- mac_out[j] |= block[j] & is_block_b;
- }
- }
-
- EVP_MD_CTX_init(&md_ctx);
- if (!EVP_DigestInit_ex(&md_ctx, md, NULL /* engine */)) {
- EVP_MD_CTX_cleanup(&md_ctx);
- return 0;
- }
-
- /* Complete the HMAC in the standard manner. */
- for (i = 0; i < md_block_size; i++) {
- hmac_pad[i] ^= 0x6a;
- }
-
- EVP_DigestUpdate(&md_ctx, hmac_pad, md_block_size);
- EVP_DigestUpdate(&md_ctx, mac_out, md_size);
- EVP_DigestFinal(&md_ctx, md_out, &md_out_size_u);
- *md_out_size = md_out_size_u;
- EVP_MD_CTX_cleanup(&md_ctx);
-
- return 1;
- }
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