/* ====================================================================

 * 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"

#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;

  declassify_assert(orig_len >= in_len);

  declassify_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_sha256_final_with_secret_suffix(SHA256_CTX *ctx,

                                        uint8_t out[SHA256_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 + SHA256_CBLOCK - 1) >> 6;

  size_t last_block = num_blocks - 1;

  size_t max_blocks = (ctx->num + max_len + 1 + 8 + SHA256_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[SHA256_CBLOCK] = {0};

  uint32_t result[8] = {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 = SHA256_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 < SHA256_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 += SHA256_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[SHA256_CBLOCK - 4 + j] |= is_last_block & length_bytes[j];

    }

    // Process the block and save the hash state if it is the final value.

    SHA256_Transform(ctx, block);

    for (size_t j = 0; j < 8; j++) {

      result[j] |= is_last_block & ctx->h[j];

    }

  }

  // Write the output.

  for (size_t i = 0; i < 8; i++) {

    CRYPTO_store_u32_be(out + 4 * i, result[i]);

  }

  return 1;

}

int EVP_tls_cbc_record_digest_supported(const EVP_MD *md) {

  switch (EVP_MD_type(md)) {

    case NID_sha1:

    case NID_sha256:

      return 1;

    default:

      return 0;

  }

}

static int tls_cbc_digest_record_sha1(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 (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;

}

static int tls_cbc_digest_record_sha256(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 (mac_secret_length > SHA256_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[SHA256_CBLOCK];

  OPENSSL_memset(hmac_pad, 0, sizeof(hmac_pad));

  OPENSSL_memcpy(hmac_pad, mac_secret, mac_secret_length);

  for (size_t i = 0; i < SHA256_CBLOCK; i++) {

    hmac_pad[i] ^= 0x36;

  }

  SHA256_CTX ctx;

  SHA256_Init(&ctx);

  SHA256_Update(&ctx, hmac_pad, SHA256_CBLOCK);

  SHA256_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 > SHA256_DIGEST_LENGTH + 256) {

    min_data_size =

        data_plus_mac_plus_padding_size - SHA256_DIGEST_LENGTH - 256;

  }

  // Hash the public minimum length directly. This reduces the number of blocks

  // that must be computed in constant-time.

  SHA256_Update(&ctx, data, min_data_size);

  // Hash the remaining data without leaking |data_size|.

  uint8_t mac_out[SHA256_DIGEST_LENGTH];

  if (!EVP_sha256_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.

  SHA256_Init(&ctx);

  for (size_t i = 0; i < SHA256_CBLOCK; i++) {

    hmac_pad[i] ^= 0x6a;

  }

  SHA256_Update(&ctx, hmac_pad, SHA256_CBLOCK);

  SHA256_Update(&ctx, mac_out, SHA256_DIGEST_LENGTH);

  SHA256_Final(md_out, &ctx);

  *md_out_size = SHA256_DIGEST_LENGTH;

  return 1;

}

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) {

  switch (EVP_MD_type(md)) {

    case NID_sha1:

      return tls_cbc_digest_record_sha1(

          md_out, md_out_size, header, data, data_size,

          data_plus_mac_plus_padding_size, mac_secret, mac_secret_length);

    case NID_sha256:

      return tls_cbc_digest_record_sha256(

          md_out, md_out_size, header, data, data_size,

          data_plus_mac_plus_padding_size, mac_secret, mac_secret_length);

    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;

  }

}