// Copyright 1995-2016 The OpenSSL Project Authors. All Rights Reserved.

//

// Licensed under the Apache License, Version 2.0 (the "License");

// you may not use this file except in compliance with the License.

// You may obtain a copy of the License at

//

//     https://www.apache.org/licenses/LICENSE-2.0

//

// Unless required by applicable law or agreed to in writing, software

// distributed under the License is distributed on an "AS IS" BASIS,

// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

// See the License for the specific language governing permissions and

// limitations under the License.

#include <assert.h>

#include <openssl/bytestring.h>

#include <openssl/digest.h>

#include <openssl/hkdf.h>

#include <openssl/hmac.h>

#include <openssl/mem.h>

#include <openssl/tls_prf.h>

#include "../../internal.h"

#include "../service_indicator/internal.h"

#include "internal.h"

using namespace bssl;

// tls1_P_hash computes the TLS P_<hash> function as described in RFC 5246,

// section 5. It XORs `out_len` bytes to `out`, using `md` as the hash and

// `secret` as the secret. `label`, `seed1`, and `seed2` are concatenated to

// form the seed parameter. It returns true on success and false on failure.

static int tls1_P_hash(uint8_t *out, size_t out_len, const EVP_MD *md,

                       const uint8_t *secret, size_t secret_len,

                       const uint8_t *label, size_t label_len,

                       const uint8_t *seed1, size_t seed1_len,

                       const uint8_t *seed2, size_t seed2_len) {

  HMAC_CTX ctx, ctx_tmp, ctx_init;

  uint8_t A1[EVP_MAX_MD_SIZE];

  unsigned A1_len;

  int ret = 0;

  const size_t chunk = EVP_MD_size(md);

  HMAC_CTX_init(&ctx);

  HMAC_CTX_init(&ctx_tmp);

  HMAC_CTX_init(&ctx_init);

  if (!HMAC_Init_ex(&ctx_init, secret, secret_len, md, nullptr) ||

      !HMAC_CTX_copy_ex(&ctx, &ctx_init) ||

      !HMAC_Update(&ctx, label, label_len) ||

      !HMAC_Update(&ctx, seed1, seed1_len) ||

      !HMAC_Update(&ctx, seed2, seed2_len) ||  //

      !HMAC_Final(&ctx, A1, &A1_len)) {

    goto err;

  }

  for (;;) {

    unsigned len_u;

    uint8_t hmac[EVP_MAX_MD_SIZE];

    if (!HMAC_CTX_copy_ex(&ctx, &ctx_init) || !HMAC_Update(&ctx, A1, A1_len) ||

        // Save a copy of `ctx` to compute the next A1 value below.

        (out_len > chunk && !HMAC_CTX_copy_ex(&ctx_tmp, &ctx)) ||

        !HMAC_Update(&ctx, (const uint8_t *)label, label_len) ||

        !HMAC_Update(&ctx, seed1, seed1_len) ||

        !HMAC_Update(&ctx, seed2, seed2_len) ||

        !HMAC_Final(&ctx, hmac, &len_u)) {

      goto err;

    }

    size_t len = len_u;

    assert(len == chunk);

    // XOR the result into `out`.

    if (len > out_len) {

      len = out_len;

    }

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

      out[i] ^= hmac[i];

    }

    out += len;

    out_len -= len;

    if (out_len == 0) {

      break;

    }

    // Calculate the next A1 value.

    if (!HMAC_Final(&ctx_tmp, A1, &A1_len)) {

      goto err;

    }

  }

  ret = 1;

err:

  OPENSSL_cleanse(A1, sizeof(A1));

  HMAC_CTX_cleanup(&ctx);

  HMAC_CTX_cleanup(&ctx_tmp);

  HMAC_CTX_cleanup(&ctx_init);

  return ret;

}

int CRYPTO_tls1_prf(const EVP_MD *digest, uint8_t *out, size_t out_len,

                    const uint8_t *secret, size_t secret_len,

                    const uint8_t *label, size_t label_len,

                    const uint8_t *seed1, size_t seed1_len,

                    const uint8_t *seed2, size_t seed2_len) {

  if (out_len == 0) {

    return 1;

  }

  OPENSSL_memset(out, 0, out_len);

  const EVP_MD *const original_digest = digest;

  FIPS_service_indicator_lock_state();

  int ret = 0;

  if (digest == EVP_md5_sha1()) {

    // If using the MD5/SHA1 PRF, `secret` is partitioned between MD5 and SHA-1.

    size_t secret_half = secret_len - (secret_len / 2);

    if (!tls1_P_hash(out, out_len, EVP_md5(), secret, secret_half, label,

                     label_len, seed1, seed1_len, seed2, seed2_len)) {

      goto end;

    }

    // Note that, if `secret_len` is odd, the two halves share a byte.

    secret += secret_len - secret_half;

    secret_len = secret_half;

    digest = EVP_sha1();

  }

  ret = tls1_P_hash(out, out_len, digest, secret, secret_len, label, label_len,

                    seed1, seed1_len, seed2, seed2_len);

end:

  FIPS_service_indicator_unlock_state();

  if (ret) {

    TLSKDF_verify_service_indicator(original_digest);

  }

  return ret;

}

int bssl::CRYPTO_tls13_hkdf_expand_label(uint8_t *out, size_t out_len,

                                         const EVP_MD *digest,  //

                                         const uint8_t *secret,

                                         size_t secret_len,

                                         const uint8_t *label, size_t label_len,

                                         const uint8_t *hash, size_t hash_len) {

  static const uint8_t kProtocolLabel[] = "tls13 ";

  CBB cbb, child;

  uint8_t *hkdf_label = nullptr;

  size_t hkdf_label_len;

  FIPS_service_indicator_lock_state();

  CBB_zero(&cbb);

  if (!CBB_init(&cbb, 2 + 1 + sizeof(kProtocolLabel) - 1 + label_len + 1 +

                          hash_len) ||

      !CBB_add_u16(&cbb, out_len) ||

      !CBB_add_u8_length_prefixed(&cbb, &child) ||

      !CBB_add_bytes(&child, kProtocolLabel, sizeof(kProtocolLabel) - 1) ||

      !CBB_add_bytes(&child, label, label_len) ||

      !CBB_add_u8_length_prefixed(&cbb, &child) ||

      !CBB_add_bytes(&child, hash, hash_len) ||

      !CBB_finish(&cbb, &hkdf_label, &hkdf_label_len)) {

    CBB_cleanup(&cbb);

    FIPS_service_indicator_unlock_state();

    return 0;

  }

  const int ret = HKDF_expand(out, out_len, digest, secret, secret_len,

                              hkdf_label, hkdf_label_len);

  OPENSSL_free(hkdf_label);

  FIPS_service_indicator_unlock_state();

  if (ret) {

    TLSKDF_verify_service_indicator(digest);

  }

  return ret;

}