ref: 98c1cd7ae022efe276123898af6b892eade0732c
dir: /third_party/boringssl/src/crypto/cipher_extra/tls_cbc.c/
/* ====================================================================
* 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
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*
* 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
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* 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)
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* 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"
#include "../fipsmodule/cipher/internal.h"
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);
assert(md_size > 0);
// 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);
}
int EVP_sha1_final_with_secret_suffix(SHA_CTX *ctx,
uint8_t out[SHA_DIGEST_LENGTH],
const uint8_t *in, size_t len,
size_t max_len) {
// Bound the input length so |total_bits| below fits in four bytes. This is
// redundant with TLS record size limits. This also ensures |input_idx| below
// does not overflow.
size_t max_len_bits = max_len << 3;
if (ctx->Nh != 0 ||
(max_len_bits >> 3) != max_len || // Overflow
ctx->Nl + max_len_bits < max_len_bits ||
ctx->Nl + max_len_bits > UINT32_MAX) {
return 0;
}
// We need to hash the following into |ctx|:
//
// - ctx->data[:ctx->num]
// - in[:len]
// - A 0x80 byte
// - However many zero bytes are needed to pad up to a block.
// - Eight bytes of length.
size_t num_blocks = (ctx->num + len + 1 + 8 + SHA_CBLOCK - 1) >> 6;
size_t last_block = num_blocks - 1;
size_t max_blocks = (ctx->num + max_len + 1 + 8 + SHA_CBLOCK - 1) >> 6;
// The bounds above imply |total_bits| fits in four bytes.
size_t total_bits = ctx->Nl + (len << 3);
uint8_t length_bytes[4];
length_bytes[0] = (uint8_t)(total_bits >> 24);
length_bytes[1] = (uint8_t)(total_bits >> 16);
length_bytes[2] = (uint8_t)(total_bits >> 8);
length_bytes[3] = (uint8_t)total_bits;
// We now construct and process each expected block in constant-time.
uint8_t block[SHA_CBLOCK] = {0};
uint32_t result[5] = {0};
// input_idx is the index into |in| corresponding to the current block.
// However, we allow this index to overflow beyond |max_len|, to simplify the
// 0x80 byte.
size_t input_idx = 0;
for (size_t i = 0; i < max_blocks; i++) {
// Fill |block| with data from the partial block in |ctx| and |in|. We copy
// as if we were hashing up to |max_len| and then zero the excess later.
size_t block_start = 0;
if (i == 0) {
OPENSSL_memcpy(block, ctx->data, ctx->num);
block_start = ctx->num;
}
if (input_idx < max_len) {
size_t to_copy = SHA_CBLOCK - block_start;
if (to_copy > max_len - input_idx) {
to_copy = max_len - input_idx;
}
OPENSSL_memcpy(block + block_start, in + input_idx, to_copy);
}
// Zero any bytes beyond |len| and add the 0x80 byte.
for (size_t j = block_start; j < SHA_CBLOCK; j++) {
// input[idx] corresponds to block[j].
size_t idx = input_idx + j - block_start;
// The barriers on |len| are not strictly necessary. However, without
// them, GCC compiles this code by incorporating |len| into the loop
// counter and subtracting it out later. This is still constant-time, but
// it frustrates attempts to validate this.
uint8_t is_in_bounds = constant_time_lt_8(idx, value_barrier_w(len));
uint8_t is_padding_byte = constant_time_eq_8(idx, value_barrier_w(len));
block[j] &= is_in_bounds;
block[j] |= 0x80 & is_padding_byte;
}
input_idx += SHA_CBLOCK - block_start;
// Fill in the length if this is the last block.
crypto_word_t is_last_block = constant_time_eq_w(i, last_block);
for (size_t j = 0; j < 4; j++) {
block[SHA_CBLOCK - 4 + j] |= is_last_block & length_bytes[j];
}
// Process the block and save the hash state if it is the final value.
SHA1_Transform(ctx, block);
for (size_t j = 0; j < 5; j++) {
result[j] |= is_last_block & ctx->h[j];
}
}
// Write the output.
for (size_t i = 0; i < 5; i++) {
CRYPTO_store_u32_be(out + 4 * i, result[i]);
}
return 1;
}
int EVP_tls_cbc_record_digest_supported(const EVP_MD *md) {
return EVP_MD_type(md) == NID_sha1;
}
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_size,
size_t data_plus_mac_plus_padding_size,
const uint8_t *mac_secret,
unsigned mac_secret_length) {
if (EVP_MD_type(md) != NID_sha1) {
// 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;
}
if (mac_secret_length > SHA_CBLOCK) {
// HMAC pads small keys with zeros and hashes large keys down. This function
// should never reach the large key case.
assert(0);
return 0;
}
// Compute the initial HMAC block.
uint8_t hmac_pad[SHA_CBLOCK];
OPENSSL_memset(hmac_pad, 0, sizeof(hmac_pad));
OPENSSL_memcpy(hmac_pad, mac_secret, mac_secret_length);
for (size_t i = 0; i < SHA_CBLOCK; i++) {
hmac_pad[i] ^= 0x36;
}
SHA_CTX ctx;
SHA1_Init(&ctx);
SHA1_Update(&ctx, hmac_pad, SHA_CBLOCK);
SHA1_Update(&ctx, header, 13);
// There are at most 256 bytes of padding, so we can compute the public
// minimum length for |data_size|.
size_t min_data_size = 0;
if (data_plus_mac_plus_padding_size > SHA_DIGEST_LENGTH + 256) {
min_data_size = data_plus_mac_plus_padding_size - SHA_DIGEST_LENGTH - 256;
}
// Hash the public minimum length directly. This reduces the number of blocks
// that must be computed in constant-time.
SHA1_Update(&ctx, data, min_data_size);
// Hash the remaining data without leaking |data_size|.
uint8_t mac_out[SHA_DIGEST_LENGTH];
if (!EVP_sha1_final_with_secret_suffix(
&ctx, mac_out, data + min_data_size, data_size - min_data_size,
data_plus_mac_plus_padding_size - min_data_size)) {
return 0;
}
// Complete the HMAC in the standard manner.
SHA1_Init(&ctx);
for (size_t i = 0; i < SHA_CBLOCK; i++) {
hmac_pad[i] ^= 0x6a;
}
SHA1_Update(&ctx, hmac_pad, SHA_CBLOCK);
SHA1_Update(&ctx, mac_out, SHA_DIGEST_LENGTH);
SHA1_Final(md_out, &ctx);
*md_out_size = SHA_DIGEST_LENGTH;
return 1;
}