text: /* Copyright (c) 2014, 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 <string.h>
  
  #include <openssl/chacha.h>
  #include <openssl/cipher.h>
  #include <openssl/err.h>
  #include <openssl/mem.h>
  #include <openssl/poly1305.h>
  #include <openssl/type_check.h>
  
  #include "internal.h"
  #include "../chacha/internal.h"
  #include "../fipsmodule/cipher/internal.h"
  #include "../internal.h"
  
  struct aead_chacha20_poly1305_ctx {
    uint8_t key[32];
  };
  
  OPENSSL_STATIC_ASSERT(sizeof(((EVP_AEAD_CTX *)NULL)->state) >=
                            sizeof(struct aead_chacha20_poly1305_ctx),
                        AEAD_state_is_too_small)
  #if defined(__GNUC__) || defined(__clang__)
  OPENSSL_STATIC_ASSERT(alignof(union evp_aead_ctx_st_state) >=
                            alignof(struct aead_chacha20_poly1305_ctx),
                        AEAD_state_has_insufficient_alignment)
  #endif
  
  static int aead_chacha20_poly1305_init(EVP_AEAD_CTX *ctx, const uint8_t *key,
                                         size_t key_len, size_t tag_len) {
    struct aead_chacha20_poly1305_ctx *c20_ctx =
        (struct aead_chacha20_poly1305_ctx *)&ctx->state;
  
    if (tag_len == 0) {
      tag_len = POLY1305_TAG_LEN;
    }
  
    if (tag_len > POLY1305_TAG_LEN) {
      OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_TOO_LARGE);
      return 0;
    }
  
    if (key_len != sizeof(c20_ctx->key)) {
      return 0;  // internal error - EVP_AEAD_CTX_init should catch this.
    }
  
    OPENSSL_memcpy(c20_ctx->key, key, key_len);
    ctx->tag_len = tag_len;
  
    return 1;
  }
  
  static void aead_chacha20_poly1305_cleanup(EVP_AEAD_CTX *ctx) {}
  
  static void poly1305_update_length(poly1305_state *poly1305, size_t data_len) {
    uint8_t length_bytes[8];
  
    for (unsigned i = 0; i < sizeof(length_bytes); i++) {
      length_bytes[i] = data_len;
      data_len >>= 8;
    }
  
    CRYPTO_poly1305_update(poly1305, length_bytes, sizeof(length_bytes));
  }
  
  // calc_tag fills |tag| with the authentication tag for the given inputs.
  static void calc_tag(uint8_t tag[POLY1305_TAG_LEN], const uint8_t *key,
                       const uint8_t nonce[12], const uint8_t *ad, size_t ad_len,
                       const uint8_t *ciphertext, size_t ciphertext_len,
                       const uint8_t *ciphertext_extra,
                       size_t ciphertext_extra_len) {
    alignas(16) uint8_t poly1305_key[32];
    OPENSSL_memset(poly1305_key, 0, sizeof(poly1305_key));
    CRYPTO_chacha_20(poly1305_key, poly1305_key, sizeof(poly1305_key), key, nonce,
                     0);
  
    static const uint8_t padding[16] = { 0 };  // Padding is all zeros.
    poly1305_state ctx;
    CRYPTO_poly1305_init(&ctx, poly1305_key);
    CRYPTO_poly1305_update(&ctx, ad, ad_len);
    if (ad_len % 16 != 0) {
      CRYPTO_poly1305_update(&ctx, padding, sizeof(padding) - (ad_len % 16));
    }
    CRYPTO_poly1305_update(&ctx, ciphertext, ciphertext_len);
    CRYPTO_poly1305_update(&ctx, ciphertext_extra, ciphertext_extra_len);
    const size_t ciphertext_total = ciphertext_len + ciphertext_extra_len;
    if (ciphertext_total % 16 != 0) {
      CRYPTO_poly1305_update(&ctx, padding,
                             sizeof(padding) - (ciphertext_total % 16));
    }
    poly1305_update_length(&ctx, ad_len);
    poly1305_update_length(&ctx, ciphertext_total);
    CRYPTO_poly1305_finish(&ctx, tag);
  }
  
  static int chacha20_poly1305_seal_scatter(
      const uint8_t *key, 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, size_t tag_len) {
    if (extra_in_len + tag_len < tag_len) {
      OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_TOO_LARGE);
      return 0;
    }
    if (max_out_tag_len < tag_len + extra_in_len) {
      OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_BUFFER_TOO_SMALL);
      return 0;
    }
    if (nonce_len != 12) {
      OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_UNSUPPORTED_NONCE_SIZE);
      return 0;
    }
  
    // |CRYPTO_chacha_20| uses a 32-bit block counter. Therefore we disallow
    // individual operations that work on more than 256GB at a time.
    // |in_len_64| is needed because, on 32-bit platforms, size_t is only
    // 32-bits and this produces a warning because it's always false.
    // Casting to uint64_t inside the conditional is not sufficient to stop
    // the warning.
    const uint64_t in_len_64 = in_len;
    if (in_len_64 >= (UINT64_C(1) << 32) * 64 - 64) {
      OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_TOO_LARGE);
      return 0;
    }
  
    if (max_out_tag_len < tag_len) {
      OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_BUFFER_TOO_SMALL);
      return 0;
    }
  
    // The the extra input is given, it is expected to be very short and so is
    // encrypted byte-by-byte first.
    if (extra_in_len) {
      static const size_t kChaChaBlockSize = 64;
      uint32_t block_counter = 1 + (in_len / kChaChaBlockSize);
      size_t offset = in_len % kChaChaBlockSize;
      uint8_t block[64 /* kChaChaBlockSize */];
  
      for (size_t done = 0; done < extra_in_len; block_counter++) {
        memset(block, 0, sizeof(block));
        CRYPTO_chacha_20(block, block, sizeof(block), key, nonce,
                         block_counter);
        for (size_t i = offset; i < sizeof(block) && done < extra_in_len;
             i++, done++) {
          out_tag[done] = extra_in[done] ^ block[i];
        }
        offset = 0;
      }
    }
  
    union chacha20_poly1305_seal_data data;
    if (chacha20_poly1305_asm_capable()) {
      OPENSSL_memcpy(data.in.key, key, 32);
      data.in.counter = 0;
      OPENSSL_memcpy(data.in.nonce, nonce, 12);
      data.in.extra_ciphertext = out_tag;
      data.in.extra_ciphertext_len = extra_in_len;
      chacha20_poly1305_seal(out, in, in_len, ad, ad_len, &data);
    } else {
      CRYPTO_chacha_20(out, in, in_len, key, nonce, 1);
      calc_tag(data.out.tag, key, nonce, ad, ad_len, out, in_len, out_tag,
               extra_in_len);
    }
  
    OPENSSL_memcpy(out_tag + extra_in_len, data.out.tag, tag_len);
    *out_tag_len = extra_in_len + tag_len;
    return 1;
  }
  
  static int aead_chacha20_poly1305_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_chacha20_poly1305_ctx *c20_ctx =
        (struct aead_chacha20_poly1305_ctx *)&ctx->state;
  
    return chacha20_poly1305_seal_scatter(
        c20_ctx->key, out, out_tag, out_tag_len, max_out_tag_len, nonce,
        nonce_len, in, in_len, extra_in, extra_in_len, ad, ad_len, ctx->tag_len);
  }
  
  static int aead_xchacha20_poly1305_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_chacha20_poly1305_ctx *c20_ctx =
        (struct aead_chacha20_poly1305_ctx *)&ctx->state;
  
    if (nonce_len != 24) {
      OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_UNSUPPORTED_NONCE_SIZE);
      return 0;
    }
  
    alignas(4) uint8_t derived_key[32];
    alignas(4) uint8_t derived_nonce[12];
    CRYPTO_hchacha20(derived_key, c20_ctx->key, nonce);
    OPENSSL_memset(derived_nonce, 0, 4);
    OPENSSL_memcpy(&derived_nonce[4], &nonce[16], 8);
  
    return chacha20_poly1305_seal_scatter(
        derived_key, out, out_tag, out_tag_len, max_out_tag_len,
        derived_nonce, sizeof(derived_nonce), in, in_len, extra_in, extra_in_len,
        ad, ad_len, ctx->tag_len);
  }
  
  static int chacha20_poly1305_open_gather(
      const uint8_t *key, 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, size_t tag_len) {
    if (nonce_len != 12) {
      OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_UNSUPPORTED_NONCE_SIZE);
      return 0;
    }
  
    if (in_tag_len != tag_len) {
      OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_BAD_DECRYPT);
      return 0;
    }
  
    // |CRYPTO_chacha_20| uses a 32-bit block counter. Therefore we disallow
    // individual operations that work on more than 256GB at a time.
    // |in_len_64| is needed because, on 32-bit platforms, size_t is only
    // 32-bits and this produces a warning because it's always false.
    // Casting to uint64_t inside the conditional is not sufficient to stop
    // the warning.
    const uint64_t in_len_64 = in_len;
    if (in_len_64 >= (UINT64_C(1) << 32) * 64 - 64) {
      OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_TOO_LARGE);
      return 0;
    }
  
    union chacha20_poly1305_open_data data;
    if (chacha20_poly1305_asm_capable()) {
      OPENSSL_memcpy(data.in.key, key, 32);
      data.in.counter = 0;
      OPENSSL_memcpy(data.in.nonce, nonce, 12);
      chacha20_poly1305_open(out, in, in_len, ad, ad_len, &data);
    } else {
      calc_tag(data.out.tag, key, nonce, ad, ad_len, in, in_len, NULL, 0);
      CRYPTO_chacha_20(out, in, in_len, key, nonce, 1);
    }
  
    if (CRYPTO_memcmp(data.out.tag, in_tag, tag_len) != 0) {
      OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_BAD_DECRYPT);
      return 0;
    }
  
    return 1;
  }
  
  static int aead_chacha20_poly1305_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_chacha20_poly1305_ctx *c20_ctx =
        (struct aead_chacha20_poly1305_ctx *)&ctx->state;
  
    return chacha20_poly1305_open_gather(c20_ctx->key, out, nonce, nonce_len, in,
                                         in_len, in_tag, in_tag_len, ad, ad_len,
                                         ctx->tag_len);
  }
  
  static int aead_xchacha20_poly1305_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_chacha20_poly1305_ctx *c20_ctx =
        (struct aead_chacha20_poly1305_ctx *)&ctx->state;
  
    if (nonce_len != 24) {
      OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_UNSUPPORTED_NONCE_SIZE);
      return 0;
    }
  
    alignas(4) uint8_t derived_key[32];
    alignas(4) uint8_t derived_nonce[12];
    CRYPTO_hchacha20(derived_key, c20_ctx->key, nonce);
    OPENSSL_memset(derived_nonce, 0, 4);
    OPENSSL_memcpy(&derived_nonce[4], &nonce[16], 8);
  
    return chacha20_poly1305_open_gather(
        derived_key, out, derived_nonce, sizeof(derived_nonce), in, in_len,
        in_tag, in_tag_len, ad, ad_len, ctx->tag_len);
  }
  
  static const EVP_AEAD aead_chacha20_poly1305 = {
      32,                // key len
      12,                // nonce len
      POLY1305_TAG_LEN,  // overhead
      POLY1305_TAG_LEN,  // max tag length
      1,                 // seal_scatter_supports_extra_in
  
      aead_chacha20_poly1305_init,
      NULL,  // init_with_direction
      aead_chacha20_poly1305_cleanup,
      NULL /* open */,
      aead_chacha20_poly1305_seal_scatter,
      aead_chacha20_poly1305_open_gather,
      NULL,  // get_iv
      NULL,  // tag_len
  };
  
  static const EVP_AEAD aead_xchacha20_poly1305 = {
      32,                // key len
      24,                // nonce len
      POLY1305_TAG_LEN,  // overhead
      POLY1305_TAG_LEN,  // max tag length
      1,                 // seal_scatter_supports_extra_in
  
      aead_chacha20_poly1305_init,
      NULL,  // init_with_direction
      aead_chacha20_poly1305_cleanup,
      NULL /* open */,
      aead_xchacha20_poly1305_seal_scatter,
      aead_xchacha20_poly1305_open_gather,
      NULL,  // get_iv
      NULL,  // tag_len
  };
  
  const EVP_AEAD *EVP_aead_chacha20_poly1305(void) {
    return &aead_chacha20_poly1305;
  }
  
  const EVP_AEAD *EVP_aead_xchacha20_poly1305(void) {
    return &aead_xchacha20_poly1305;
  }
  