/* Copyright (c) 2017, Google Inc.

 *

 * Permission to use, copy, modify, and/or distribute this software for any

 * purpose with or without fee is hereby granted, provided that the above

 * copyright notice and this permission notice appear in all copies.

 *

 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES

 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF

 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY

 * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES

 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION

 * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN

 * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */

#include <openssl/aead.h>

#include <assert.h>

#include <openssl/cipher.h>

#include <openssl/crypto.h>

#include <openssl/err.h>

#include <openssl/sha.h>

#include "../fipsmodule/cipher/internal.h"

#define EVP_AEAD_AES_CTR_HMAC_SHA256_TAG_LEN SHA256_DIGEST_LENGTH

#define EVP_AEAD_AES_CTR_HMAC_SHA256_NONCE_LEN 12

struct aead_aes_ctr_hmac_sha256_ctx {

  union {

    double align;

    AES_KEY ks;

  } ks;

  ctr128_f ctr;

  block128_f block;

  SHA256_CTX inner_init_state;

  SHA256_CTX outer_init_state;

};

static_assert(sizeof(((EVP_AEAD_CTX *)NULL)->state) >=

                  sizeof(struct aead_aes_ctr_hmac_sha256_ctx),

              "AEAD state is too small");

static_assert(alignof(union evp_aead_ctx_st_state) >=

                  alignof(struct aead_aes_ctr_hmac_sha256_ctx),

              "AEAD state has insufficient alignment");

static void hmac_init(SHA256_CTX *out_inner, SHA256_CTX *out_outer,

                      const uint8_t hmac_key[32]) {

  static const size_t hmac_key_len = 32;

  uint8_t block[SHA256_CBLOCK];

  OPENSSL_memcpy(block, hmac_key, hmac_key_len);

  OPENSSL_memset(block + hmac_key_len, 0x36, sizeof(block) - hmac_key_len);

  unsigned i;

  for (i = 0; i < hmac_key_len; i++) {

    block[i] ^= 0x36;

  }

  SHA256_Init(out_inner);

  SHA256_Update(out_inner, block, sizeof(block));

  OPENSSL_memset(block + hmac_key_len, 0x5c, sizeof(block) - hmac_key_len);

  for (i = 0; i < hmac_key_len; i++) {

    block[i] ^= (0x36 ^ 0x5c);

  }

  SHA256_Init(out_outer);

  SHA256_Update(out_outer, block, sizeof(block));

}

static int aead_aes_ctr_hmac_sha256_init(EVP_AEAD_CTX *ctx, const uint8_t *key,

                                         size_t key_len, size_t tag_len) {

  struct aead_aes_ctr_hmac_sha256_ctx *aes_ctx =

      (struct aead_aes_ctr_hmac_sha256_ctx *)&ctx->state;

  static const size_t hmac_key_len = 32;

  if (key_len < hmac_key_len) {

    OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_BAD_KEY_LENGTH);

    return 0;  // EVP_AEAD_CTX_init should catch this.

  }

  const size_t aes_key_len = key_len - hmac_key_len;

  if (aes_key_len != 16 && aes_key_len != 32) {

    OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_BAD_KEY_LENGTH);

    return 0;  // EVP_AEAD_CTX_init should catch this.

  }

  if (tag_len == EVP_AEAD_DEFAULT_TAG_LENGTH) {

    tag_len = EVP_AEAD_AES_CTR_HMAC_SHA256_TAG_LEN;

  }

  if (tag_len > EVP_AEAD_AES_CTR_HMAC_SHA256_TAG_LEN) {

    OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_TAG_TOO_LARGE);

    return 0;

  }

  aes_ctx->ctr =

      aes_ctr_set_key(&aes_ctx->ks.ks, NULL, &aes_ctx->block, key, aes_key_len);

  ctx->tag_len = tag_len;

  hmac_init(&aes_ctx->inner_init_state, &aes_ctx->outer_init_state,

            key + aes_key_len);

  return 1;

}

static void aead_aes_ctr_hmac_sha256_cleanup(EVP_AEAD_CTX *ctx) {}

static void hmac_update_uint64(SHA256_CTX *sha256, uint64_t value) {

  unsigned i;

  uint8_t bytes[8];

  for (i = 0; i < sizeof(bytes); i++) {

    bytes[i] = value & 0xff;

    value >>= 8;

  }

  SHA256_Update(sha256, bytes, sizeof(bytes));

}

static void hmac_calculate(uint8_t out[SHA256_DIGEST_LENGTH],

                           const SHA256_CTX *inner_init_state,

                           const SHA256_CTX *outer_init_state,

                           const uint8_t *ad, size_t ad_len,

                           const uint8_t *nonce, const uint8_t *ciphertext,

                           size_t ciphertext_len) {

  SHA256_CTX sha256;

  OPENSSL_memcpy(&sha256, inner_init_state, sizeof(sha256));

  hmac_update_uint64(&sha256, ad_len);

  hmac_update_uint64(&sha256, ciphertext_len);

  SHA256_Update(&sha256, nonce, EVP_AEAD_AES_CTR_HMAC_SHA256_NONCE_LEN);

  SHA256_Update(&sha256, ad, ad_len);

  // Pad with zeros to the end of the SHA-256 block.

  const unsigned num_padding =

      (SHA256_CBLOCK - ((sizeof(uint64_t)*2 +

                         EVP_AEAD_AES_CTR_HMAC_SHA256_NONCE_LEN + ad_len) %

                        SHA256_CBLOCK)) %

      SHA256_CBLOCK;

  uint8_t padding[SHA256_CBLOCK];

  OPENSSL_memset(padding, 0, num_padding);

  SHA256_Update(&sha256, padding, num_padding);

  SHA256_Update(&sha256, ciphertext, ciphertext_len);

  uint8_t inner_digest[SHA256_DIGEST_LENGTH];

  SHA256_Final(inner_digest, &sha256);

  OPENSSL_memcpy(&sha256, outer_init_state, sizeof(sha256));

  SHA256_Update(&sha256, inner_digest, sizeof(inner_digest));

  SHA256_Final(out, &sha256);

}

static void aead_aes_ctr_hmac_sha256_crypt(

    const struct aead_aes_ctr_hmac_sha256_ctx *aes_ctx, uint8_t *out,

    const uint8_t *in, size_t len, const uint8_t *nonce) {

  // Since the AEAD operation is one-shot, keeping a buffer of unused keystream

  // bytes is pointless. However, |CRYPTO_ctr128_encrypt| requires it.

  uint8_t partial_block_buffer[AES_BLOCK_SIZE];

  unsigned partial_block_offset = 0;

  OPENSSL_memset(partial_block_buffer, 0, sizeof(partial_block_buffer));

  uint8_t counter[AES_BLOCK_SIZE];

  OPENSSL_memcpy(counter, nonce, EVP_AEAD_AES_CTR_HMAC_SHA256_NONCE_LEN);

  OPENSSL_memset(counter + EVP_AEAD_AES_CTR_HMAC_SHA256_NONCE_LEN, 0, 4);

  if (aes_ctx->ctr) {

    CRYPTO_ctr128_encrypt_ctr32(in, out, len, &aes_ctx->ks.ks, counter,

                                partial_block_buffer, &partial_block_offset,

                                aes_ctx->ctr);

  } else {

    CRYPTO_ctr128_encrypt(in, out, len, &aes_ctx->ks.ks, counter,

                          partial_block_buffer, &partial_block_offset,

                          aes_ctx->block);

  }

}

static int aead_aes_ctr_hmac_sha256_seal_scatter(

    const EVP_AEAD_CTX *ctx, uint8_t *out, uint8_t *out_tag,

    size_t *out_tag_len, size_t max_out_tag_len, const uint8_t *nonce,

    size_t nonce_len, const uint8_t *in, size_t in_len, const uint8_t *extra_in,

    size_t extra_in_len, const uint8_t *ad, size_t ad_len) {

  const struct aead_aes_ctr_hmac_sha256_ctx *aes_ctx =

      (struct aead_aes_ctr_hmac_sha256_ctx *) &ctx->state;

  const uint64_t in_len_64 = in_len;

  if (in_len_64 >= (UINT64_C(1) << 32) * AES_BLOCK_SIZE) {

     // This input is so large it would overflow the 32-bit block counter.

    OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_TOO_LARGE);

    return 0;

  }

  if (max_out_tag_len < ctx->tag_len) {

    OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_BUFFER_TOO_SMALL);

    return 0;

  }

  if (nonce_len != EVP_AEAD_AES_CTR_HMAC_SHA256_NONCE_LEN) {

    OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_UNSUPPORTED_NONCE_SIZE);

    return 0;

  }

  aead_aes_ctr_hmac_sha256_crypt(aes_ctx, out, in, in_len, nonce);

  uint8_t hmac_result[SHA256_DIGEST_LENGTH];

  hmac_calculate(hmac_result, &aes_ctx->inner_init_state,

                 &aes_ctx->outer_init_state, ad, ad_len, nonce, out, in_len);

  OPENSSL_memcpy(out_tag, hmac_result, ctx->tag_len);

  *out_tag_len = ctx->tag_len;

  return 1;

}

static int aead_aes_ctr_hmac_sha256_open_gather(

    const EVP_AEAD_CTX *ctx, uint8_t *out, const uint8_t *nonce,

    size_t nonce_len, const uint8_t *in, size_t in_len, const uint8_t *in_tag,

    size_t in_tag_len, const uint8_t *ad, size_t ad_len) {

  const struct aead_aes_ctr_hmac_sha256_ctx *aes_ctx =

      (struct aead_aes_ctr_hmac_sha256_ctx *) &ctx->state;

  if (in_tag_len != ctx->tag_len) {

    OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_BAD_DECRYPT);

    return 0;

  }

  if (nonce_len != EVP_AEAD_AES_CTR_HMAC_SHA256_NONCE_LEN) {

    OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_UNSUPPORTED_NONCE_SIZE);

    return 0;

  }

  uint8_t hmac_result[SHA256_DIGEST_LENGTH];

  hmac_calculate(hmac_result, &aes_ctx->inner_init_state,

                 &aes_ctx->outer_init_state, ad, ad_len, nonce, in,

                 in_len);

  if (CRYPTO_memcmp(hmac_result, in_tag, ctx->tag_len) != 0) {

    OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_BAD_DECRYPT);

    return 0;

  }

  aead_aes_ctr_hmac_sha256_crypt(aes_ctx, out, in, in_len, nonce);

  return 1;

}

static const EVP_AEAD aead_aes_128_ctr_hmac_sha256 = {

    16 /* AES key */ + 32 /* HMAC key */,

    12,                                    // nonce length

    EVP_AEAD_AES_CTR_HMAC_SHA256_TAG_LEN,  // overhead

    EVP_AEAD_AES_CTR_HMAC_SHA256_TAG_LEN,  // max tag length

    0,                                     // seal_scatter_supports_extra_in

    aead_aes_ctr_hmac_sha256_init,

    NULL /* init_with_direction */,

    aead_aes_ctr_hmac_sha256_cleanup,

    NULL /* open */,

    aead_aes_ctr_hmac_sha256_seal_scatter,

    aead_aes_ctr_hmac_sha256_open_gather,

    NULL /* get_iv */,

    NULL /* tag_len */,

};

static const EVP_AEAD aead_aes_256_ctr_hmac_sha256 = {

    32 /* AES key */ + 32 /* HMAC key */,

    12,                                    // nonce length

    EVP_AEAD_AES_CTR_HMAC_SHA256_TAG_LEN,  // overhead

    EVP_AEAD_AES_CTR_HMAC_SHA256_TAG_LEN,  // max tag length

    0,                                     // seal_scatter_supports_extra_in

    aead_aes_ctr_hmac_sha256_init,

    NULL /* init_with_direction */,

    aead_aes_ctr_hmac_sha256_cleanup,

    NULL /* open */,

    aead_aes_ctr_hmac_sha256_seal_scatter,

    aead_aes_ctr_hmac_sha256_open_gather,

    NULL /* get_iv */,

    NULL /* tag_len */,

};

const EVP_AEAD *EVP_aead_aes_128_ctr_hmac_sha256(void) {

  return &aead_aes_128_ctr_hmac_sha256;

}

const EVP_AEAD *EVP_aead_aes_256_ctr_hmac_sha256(void) {

  return &aead_aes_256_ctr_hmac_sha256;

}