crypto/cipher_extra/e_tls.c - boringssl - Git at Google

 /* 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 <assert.h>
 #include <limits.h>
 #include <string.h>

 #include <openssl/aead.h>
 #include <openssl/cipher.h>
 #include <openssl/err.h>
 #include <openssl/hmac.h>
 #include <openssl/md5.h>
 #include <openssl/mem.h>
 #include <openssl/sha.h>

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


 typedef struct {
   EVP_CIPHER_CTX cipher_ctx;
   HMAC_CTX hmac_ctx;
   // mac_key is the portion of the key used for the MAC. It is retained
   // separately for the constant-time CBC code.
   uint8_t mac_key[EVP_MAX_MD_SIZE];
   uint8_t mac_key_len;
   // implicit_iv is one iff this is a pre-TLS-1.1 CBC cipher without an explicit
   // IV.
   char implicit_iv;
 } AEAD_TLS_CTX;

 static_assert(EVP_MAX_MD_SIZE < 256, "mac_key_len does not fit in uint8_t");

 static_assert(sizeof(((EVP_AEAD_CTX *)NULL)->state) >= sizeof(AEAD_TLS_CTX),
               "AEAD state is too small");
 static_assert(alignof(union evp_aead_ctx_st_state) >= alignof(AEAD_TLS_CTX),
               "AEAD state has insufficient alignment");

 static void aead_tls_cleanup(EVP_AEAD_CTX *ctx) {
   AEAD_TLS_CTX *tls_ctx = (AEAD_TLS_CTX *)&ctx->state;
   EVP_CIPHER_CTX_cleanup(&tls_ctx->cipher_ctx);
   HMAC_CTX_cleanup(&tls_ctx->hmac_ctx);
 }

 static int aead_tls_init(EVP_AEAD_CTX *ctx, const uint8_t *key, size_t key_len,
                          size_t tag_len, enum evp_aead_direction_t dir,
                          const EVP_CIPHER *cipher, const EVP_MD *md,
                          char implicit_iv) {
   if (tag_len != EVP_AEAD_DEFAULT_TAG_LENGTH &&
       tag_len != EVP_MD_size(md)) {
     OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_UNSUPPORTED_TAG_SIZE);
     return 0;
   }

   if (key_len != EVP_AEAD_key_length(ctx->aead)) {
     OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_BAD_KEY_LENGTH);
     return 0;
   }

   size_t mac_key_len = EVP_MD_size(md);
   size_t enc_key_len = EVP_CIPHER_key_length(cipher);
   assert(mac_key_len + enc_key_len +
          (implicit_iv ? EVP_CIPHER_iv_length(cipher) : 0) == key_len);

   AEAD_TLS_CTX *tls_ctx = (AEAD_TLS_CTX *)&ctx->state;
   EVP_CIPHER_CTX_init(&tls_ctx->cipher_ctx);
   HMAC_CTX_init(&tls_ctx->hmac_ctx);
   assert(mac_key_len <= EVP_MAX_MD_SIZE);
   OPENSSL_memcpy(tls_ctx->mac_key, key, mac_key_len);
   tls_ctx->mac_key_len = (uint8_t)mac_key_len;
   tls_ctx->implicit_iv = implicit_iv;

   if (!EVP_CipherInit_ex(&tls_ctx->cipher_ctx, cipher, NULL, &key[mac_key_len],
                          implicit_iv ? &key[mac_key_len + enc_key_len] : NULL,
                          dir == evp_aead_seal) ||
       !HMAC_Init_ex(&tls_ctx->hmac_ctx, key, mac_key_len, md, NULL)) {
     aead_tls_cleanup(ctx);
     return 0;
   }
   EVP_CIPHER_CTX_set_padding(&tls_ctx->cipher_ctx, 0);

   return 1;
 }

 static size_t aead_tls_tag_len(const EVP_AEAD_CTX *ctx, const size_t in_len,
                                const size_t extra_in_len) {
   assert(extra_in_len == 0);
   const AEAD_TLS_CTX *tls_ctx = (AEAD_TLS_CTX *)&ctx->state;

   const size_t hmac_len = HMAC_size(&tls_ctx->hmac_ctx);
   if (EVP_CIPHER_CTX_mode(&tls_ctx->cipher_ctx) != EVP_CIPH_CBC_MODE) {
     // The NULL cipher.
     return hmac_len;
   }

   const size_t block_size = EVP_CIPHER_CTX_block_size(&tls_ctx->cipher_ctx);
   // An overflow of |in_len + hmac_len| doesn't affect the result mod
   // |block_size|, provided that |block_size| is a smaller power of two.
   assert(block_size != 0 && (block_size & (block_size - 1)) == 0);
   const size_t pad_len = block_size - (in_len + hmac_len) % block_size;
   return hmac_len + pad_len;
 }

 static int aead_tls_seal_scatter(const EVP_AEAD_CTX *ctx, uint8_t *out,
                                  uint8_t *out_tag, size_t *out_tag_len,
                                  const size_t max_out_tag_len,
                                  const uint8_t *nonce, const size_t nonce_len,
                                  const uint8_t *in, const size_t in_len,
                                  const uint8_t *extra_in,
                                  const size_t extra_in_len, const uint8_t *ad,
                                  const size_t ad_len) {
   AEAD_TLS_CTX *tls_ctx = (AEAD_TLS_CTX *)&ctx->state;

   if (!tls_ctx->cipher_ctx.encrypt) {
     // Unlike a normal AEAD, a TLS AEAD may only be used in one direction.
     OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_INVALID_OPERATION);
     return 0;
   }

   if (in_len > INT_MAX) {
     // EVP_CIPHER takes int as input.
     OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_TOO_LARGE);
     return 0;
   }

   if (max_out_tag_len < aead_tls_tag_len(ctx, in_len, extra_in_len)) {
     OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_BUFFER_TOO_SMALL);
     return 0;
   }

   if (nonce_len != EVP_AEAD_nonce_length(ctx->aead)) {
     OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_INVALID_NONCE_SIZE);
     return 0;
   }

   if (ad_len != 13 - 2 /* length bytes */) {
     OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_INVALID_AD_SIZE);
     return 0;
   }

   // To allow for CBC mode which changes cipher length, |ad| doesn't include the
   // length for legacy ciphers.
   uint8_t ad_extra[2];
   ad_extra[0] = (uint8_t)(in_len >> 8);
   ad_extra[1] = (uint8_t)(in_len & 0xff);

   // Compute the MAC. This must be first in case the operation is being done
   // in-place.
   uint8_t mac[EVP_MAX_MD_SIZE];
   unsigned mac_len;
   if (!HMAC_Init_ex(&tls_ctx->hmac_ctx, NULL, 0, NULL, NULL) ||
       !HMAC_Update(&tls_ctx->hmac_ctx, ad, ad_len) ||
       !HMAC_Update(&tls_ctx->hmac_ctx, ad_extra, sizeof(ad_extra)) ||
       !HMAC_Update(&tls_ctx->hmac_ctx, in, in_len) ||
       !HMAC_Final(&tls_ctx->hmac_ctx, mac, &mac_len)) {
     return 0;
   }

   // Configure the explicit IV.
   if (EVP_CIPHER_CTX_mode(&tls_ctx->cipher_ctx) == EVP_CIPH_CBC_MODE &&
       !tls_ctx->implicit_iv &&
       !EVP_EncryptInit_ex(&tls_ctx->cipher_ctx, NULL, NULL, NULL, nonce)) {
     return 0;
   }

   // Encrypt the input.
   int len;
   if (!EVP_EncryptUpdate(&tls_ctx->cipher_ctx, out, &len, in, (int)in_len)) {
     return 0;
   }

   unsigned block_size = EVP_CIPHER_CTX_block_size(&tls_ctx->cipher_ctx);

   // Feed the MAC into the cipher in two steps. First complete the final partial
   // block from encrypting the input and split the result between |out| and
   // |out_tag|. Then feed the rest.

   const size_t early_mac_len = (block_size - (in_len % block_size)) % block_size;
   if (early_mac_len != 0) {
     assert(len + block_size - early_mac_len == in_len);
     uint8_t buf[EVP_MAX_BLOCK_LENGTH];
     int buf_len;
     if (!EVP_EncryptUpdate(&tls_ctx->cipher_ctx, buf, &buf_len, mac,
                            (int)early_mac_len)) {
       return 0;
     }
     assert(buf_len == (int)block_size);
     OPENSSL_memcpy(out + len, buf, block_size - early_mac_len);
     OPENSSL_memcpy(out_tag, buf + block_size - early_mac_len, early_mac_len);
   }
   size_t tag_len = early_mac_len;

   if (!EVP_EncryptUpdate(&tls_ctx->cipher_ctx, out_tag + tag_len, &len,
                          mac + tag_len, mac_len - tag_len)) {
     return 0;
   }
   tag_len += len;

   if (block_size > 1) {
     assert(block_size <= 256);
     assert(EVP_CIPHER_CTX_mode(&tls_ctx->cipher_ctx) == EVP_CIPH_CBC_MODE);

     // Compute padding and feed that into the cipher.
     uint8_t padding[256];
     unsigned padding_len = block_size - ((in_len + mac_len) % block_size);
     OPENSSL_memset(padding, padding_len - 1, padding_len);
     if (!EVP_EncryptUpdate(&tls_ctx->cipher_ctx, out_tag + tag_len, &len,
                            padding, (int)padding_len)) {
       return 0;
     }
     tag_len += len;
   }

   if (!EVP_EncryptFinal_ex(&tls_ctx->cipher_ctx, out_tag + tag_len, &len)) {
     return 0;
   }
   assert(len == 0);  // Padding is explicit.
   assert(tag_len == aead_tls_tag_len(ctx, in_len, extra_in_len));

   *out_tag_len = tag_len;
   return 1;
 }

 static int aead_tls_open(const EVP_AEAD_CTX *ctx, uint8_t *out, size_t *out_len,
                          size_t max_out_len, const uint8_t *nonce,
                          size_t nonce_len, const uint8_t *in, size_t in_len,
                          const uint8_t *ad, size_t ad_len) {
   AEAD_TLS_CTX *tls_ctx = (AEAD_TLS_CTX *)&ctx->state;

   if (tls_ctx->cipher_ctx.encrypt) {
     // Unlike a normal AEAD, a TLS AEAD may only be used in one direction.
     OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_INVALID_OPERATION);
     return 0;
   }

   if (in_len < HMAC_size(&tls_ctx->hmac_ctx)) {
     OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_BAD_DECRYPT);
     return 0;
   }

   if (max_out_len < in_len) {
     // This requires that the caller provide space for the MAC, even though it
     // will always be removed on return.
     OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_BUFFER_TOO_SMALL);
     return 0;
   }

   if (nonce_len != EVP_AEAD_nonce_length(ctx->aead)) {
     OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_INVALID_NONCE_SIZE);
     return 0;
   }

   if (ad_len != 13 - 2 /* length bytes */) {
     OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_INVALID_AD_SIZE);
     return 0;
   }

   if (in_len > INT_MAX) {
     // EVP_CIPHER takes int as input.
     OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_TOO_LARGE);
     return 0;
   }

   // Configure the explicit IV.
   if (EVP_CIPHER_CTX_mode(&tls_ctx->cipher_ctx) == EVP_CIPH_CBC_MODE &&
       !tls_ctx->implicit_iv &&
       !EVP_DecryptInit_ex(&tls_ctx->cipher_ctx, NULL, NULL, NULL, nonce)) {
     return 0;
   }

   // Decrypt to get the plaintext + MAC + padding.
   size_t total = 0;
   int len;
   if (!EVP_DecryptUpdate(&tls_ctx->cipher_ctx, out, &len, in, (int)in_len)) {
     return 0;
   }
   total += len;
   if (!EVP_DecryptFinal_ex(&tls_ctx->cipher_ctx, out + total, &len)) {
     return 0;
   }
   total += len;
   assert(total == in_len);

   CONSTTIME_SECRET(out, total);

   // Remove CBC padding. Code from here on is timing-sensitive with respect to
   // |padding_ok| and |data_plus_mac_len| for CBC ciphers.
   size_t data_plus_mac_len;
   crypto_word_t padding_ok;
   if (EVP_CIPHER_CTX_mode(&tls_ctx->cipher_ctx) == EVP_CIPH_CBC_MODE) {
     if (!EVP_tls_cbc_remove_padding(
             &padding_ok, &data_plus_mac_len, out, total,
             EVP_CIPHER_CTX_block_size(&tls_ctx->cipher_ctx),
             HMAC_size(&tls_ctx->hmac_ctx))) {
       // Publicly invalid. This can be rejected in non-constant time.
       OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_BAD_DECRYPT);
       return 0;
     }
   } else {
     padding_ok = CONSTTIME_TRUE_W;
     data_plus_mac_len = total;
     // |data_plus_mac_len| = |total| = |in_len| at this point. |in_len| has
     // already been checked against the MAC size at the top of the function.
     assert(data_plus_mac_len >= HMAC_size(&tls_ctx->hmac_ctx));
   }
   size_t data_len = data_plus_mac_len - HMAC_size(&tls_ctx->hmac_ctx);

   // At this point, if the padding is valid, the first |data_plus_mac_len| bytes
   // after |out| are the plaintext and MAC. Otherwise, |data_plus_mac_len| is
   // still large enough to extract a MAC, but it will be irrelevant.

   // To allow for CBC mode which changes cipher length, |ad| doesn't include the
   // length for legacy ciphers.
   uint8_t ad_fixed[13];
   OPENSSL_memcpy(ad_fixed, ad, 11);
   ad_fixed[11] = (uint8_t)(data_len >> 8);
   ad_fixed[12] = (uint8_t)(data_len & 0xff);
   ad_len += 2;

   // Compute the MAC and extract the one in the record.
   uint8_t mac[EVP_MAX_MD_SIZE];
   size_t mac_len;
   uint8_t record_mac_tmp[EVP_MAX_MD_SIZE];
   uint8_t *record_mac;
   if (EVP_CIPHER_CTX_mode(&tls_ctx->cipher_ctx) == EVP_CIPH_CBC_MODE &&
       EVP_tls_cbc_record_digest_supported(tls_ctx->hmac_ctx.md)) {
     if (!EVP_tls_cbc_digest_record(tls_ctx->hmac_ctx.md, mac, &mac_len,
                                    ad_fixed, out, data_len, total,
                                    tls_ctx->mac_key, tls_ctx->mac_key_len)) {
       OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_BAD_DECRYPT);
       return 0;
     }
     assert(mac_len == HMAC_size(&tls_ctx->hmac_ctx));

     record_mac = record_mac_tmp;
     EVP_tls_cbc_copy_mac(record_mac, mac_len, out, data_plus_mac_len, total);
   } else {
     // We should support the constant-time path for all CBC-mode ciphers
     // implemented.
     assert(EVP_CIPHER_CTX_mode(&tls_ctx->cipher_ctx) != EVP_CIPH_CBC_MODE);

     unsigned mac_len_u;
     if (!HMAC_Init_ex(&tls_ctx->hmac_ctx, NULL, 0, NULL, NULL) ||
         !HMAC_Update(&tls_ctx->hmac_ctx, ad_fixed, ad_len) ||
         !HMAC_Update(&tls_ctx->hmac_ctx, out, data_len) ||
         !HMAC_Final(&tls_ctx->hmac_ctx, mac, &mac_len_u)) {
       return 0;
     }
     mac_len = mac_len_u;

     assert(mac_len == HMAC_size(&tls_ctx->hmac_ctx));
     record_mac = &out[data_len];
   }

   // Perform the MAC check and the padding check in constant-time. It should be
   // safe to simply perform the padding check first, but it would not be under a
   // different choice of MAC location on padding failure. See
   // EVP_tls_cbc_remove_padding.
   crypto_word_t good =
       constant_time_eq_int(CRYPTO_memcmp(record_mac, mac, mac_len), 0);
   good &= padding_ok;
   CONSTTIME_DECLASSIFY(&good, sizeof(good));
   if (!good) {
     OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_BAD_DECRYPT);
     return 0;
   }

   CONSTTIME_DECLASSIFY(&data_len, sizeof(data_len));
   CONSTTIME_DECLASSIFY(out, data_len);

   // End of timing-sensitive code.

   *out_len = data_len;
   return 1;
 }

 static int aead_aes_128_cbc_sha1_tls_init(EVP_AEAD_CTX *ctx, const uint8_t *key,
                                           size_t key_len, size_t tag_len,
                                           enum evp_aead_direction_t dir) {
   return aead_tls_init(ctx, key, key_len, tag_len, dir, EVP_aes_128_cbc(),
                        EVP_sha1(), 0);
 }

 static int aead_aes_128_cbc_sha1_tls_implicit_iv_init(
     EVP_AEAD_CTX *ctx, const uint8_t *key, size_t key_len, size_t tag_len,
     enum evp_aead_direction_t dir) {
   return aead_tls_init(ctx, key, key_len, tag_len, dir, EVP_aes_128_cbc(),
                        EVP_sha1(), 1);
 }

 static int aead_aes_256_cbc_sha1_tls_init(EVP_AEAD_CTX *ctx, const uint8_t *key,
                                           size_t key_len, size_t tag_len,
                                           enum evp_aead_direction_t dir) {
   return aead_tls_init(ctx, key, key_len, tag_len, dir, EVP_aes_256_cbc(),
                        EVP_sha1(), 0);
 }

 static int aead_aes_256_cbc_sha1_tls_implicit_iv_init(
     EVP_AEAD_CTX *ctx, const uint8_t *key, size_t key_len, size_t tag_len,
     enum evp_aead_direction_t dir) {
   return aead_tls_init(ctx, key, key_len, tag_len, dir, EVP_aes_256_cbc(),
                        EVP_sha1(), 1);
 }

 static int aead_des_ede3_cbc_sha1_tls_init(EVP_AEAD_CTX *ctx,
                                            const uint8_t *key, size_t key_len,
                                            size_t tag_len,
                                            enum evp_aead_direction_t dir) {
   return aead_tls_init(ctx, key, key_len, tag_len, dir, EVP_des_ede3_cbc(),
                        EVP_sha1(), 0);
 }

 static int aead_des_ede3_cbc_sha1_tls_implicit_iv_init(
     EVP_AEAD_CTX *ctx, const uint8_t *key, size_t key_len, size_t tag_len,
     enum evp_aead_direction_t dir) {
   return aead_tls_init(ctx, key, key_len, tag_len, dir, EVP_des_ede3_cbc(),
                        EVP_sha1(), 1);
 }

 static int aead_tls_get_iv(const EVP_AEAD_CTX *ctx, const uint8_t **out_iv,
                            size_t *out_iv_len) {
   const AEAD_TLS_CTX *tls_ctx = (AEAD_TLS_CTX *)&ctx->state;
   const size_t iv_len = EVP_CIPHER_CTX_iv_length(&tls_ctx->cipher_ctx);
   if (iv_len <= 1) {
     return 0;
   }

   *out_iv = tls_ctx->cipher_ctx.iv;
   *out_iv_len = iv_len;
   return 1;
 }

 static int aead_null_sha1_tls_init(EVP_AEAD_CTX *ctx, const uint8_t *key,
                                    size_t key_len, size_t tag_len,
                                    enum evp_aead_direction_t dir) {
   return aead_tls_init(ctx, key, key_len, tag_len, dir, EVP_enc_null(),
                        EVP_sha1(), 1 /* implicit iv */);
 }

 static const EVP_AEAD aead_aes_128_cbc_sha1_tls = {
     SHA_DIGEST_LENGTH + 16,  // key len (SHA1 + AES128)
     16,                      // nonce len (IV)
     16 + SHA_DIGEST_LENGTH,  // overhead (padding + SHA1)
     SHA_DIGEST_LENGTH,       // max tag length
     0,                       // seal_scatter_supports_extra_in

     NULL,  // init
     aead_aes_128_cbc_sha1_tls_init,
     aead_tls_cleanup,
     aead_tls_open,
     aead_tls_seal_scatter,
     NULL,  // open_gather
     NULL,  // get_iv
     aead_tls_tag_len,
 };

 static const EVP_AEAD aead_aes_128_cbc_sha1_tls_implicit_iv = {
     SHA_DIGEST_LENGTH + 16 + 16,  // key len (SHA1 + AES128 + IV)
     0,                            // nonce len
     16 + SHA_DIGEST_LENGTH,       // overhead (padding + SHA1)
     SHA_DIGEST_LENGTH,            // max tag length
     0,                            // seal_scatter_supports_extra_in

     NULL,  // init
     aead_aes_128_cbc_sha1_tls_implicit_iv_init,
     aead_tls_cleanup,
     aead_tls_open,
     aead_tls_seal_scatter,
     NULL,             // open_gather
     aead_tls_get_iv,  // get_iv
     aead_tls_tag_len,
 };

 static const EVP_AEAD aead_aes_256_cbc_sha1_tls = {
     SHA_DIGEST_LENGTH + 32,  // key len (SHA1 + AES256)
     16,                      // nonce len (IV)
     16 + SHA_DIGEST_LENGTH,  // overhead (padding + SHA1)
     SHA_DIGEST_LENGTH,       // max tag length
     0,                       // seal_scatter_supports_extra_in

     NULL,  // init
     aead_aes_256_cbc_sha1_tls_init,
     aead_tls_cleanup,
     aead_tls_open,
     aead_tls_seal_scatter,
     NULL,  // open_gather
     NULL,  // get_iv
     aead_tls_tag_len,
 };

 static const EVP_AEAD aead_aes_256_cbc_sha1_tls_implicit_iv = {
     SHA_DIGEST_LENGTH + 32 + 16,  // key len (SHA1 + AES256 + IV)
     0,                            // nonce len
     16 + SHA_DIGEST_LENGTH,       // overhead (padding + SHA1)
     SHA_DIGEST_LENGTH,            // max tag length
     0,                            // seal_scatter_supports_extra_in

     NULL,  // init
     aead_aes_256_cbc_sha1_tls_implicit_iv_init,
     aead_tls_cleanup,
     aead_tls_open,
     aead_tls_seal_scatter,
     NULL,             // open_gather
     aead_tls_get_iv,  // get_iv
     aead_tls_tag_len,
 };

 static const EVP_AEAD aead_des_ede3_cbc_sha1_tls = {
     SHA_DIGEST_LENGTH + 24,  // key len (SHA1 + 3DES)
     8,                       // nonce len (IV)
     8 + SHA_DIGEST_LENGTH,   // overhead (padding + SHA1)
     SHA_DIGEST_LENGTH,       // max tag length
     0,                       // seal_scatter_supports_extra_in

     NULL,  // init
     aead_des_ede3_cbc_sha1_tls_init,
     aead_tls_cleanup,
     aead_tls_open,
     aead_tls_seal_scatter,
     NULL,  // open_gather
     NULL,  // get_iv
     aead_tls_tag_len,
 };

 static const EVP_AEAD aead_des_ede3_cbc_sha1_tls_implicit_iv = {
     SHA_DIGEST_LENGTH + 24 + 8,  // key len (SHA1 + 3DES + IV)
     0,                           // nonce len
     8 + SHA_DIGEST_LENGTH,       // overhead (padding + SHA1)
     SHA_DIGEST_LENGTH,           // max tag length
     0,                           // seal_scatter_supports_extra_in

     NULL,  // init
     aead_des_ede3_cbc_sha1_tls_implicit_iv_init,
     aead_tls_cleanup,
     aead_tls_open,
     aead_tls_seal_scatter,
     NULL,             // open_gather
     aead_tls_get_iv,  // get_iv
     aead_tls_tag_len,
 };

 static const EVP_AEAD aead_null_sha1_tls = {
     SHA_DIGEST_LENGTH,  // key len
     0,                  // nonce len
     SHA_DIGEST_LENGTH,  // overhead (SHA1)
     SHA_DIGEST_LENGTH,  // max tag length
     0,                  // seal_scatter_supports_extra_in

     NULL,  // init
     aead_null_sha1_tls_init,
     aead_tls_cleanup,
     aead_tls_open,
     aead_tls_seal_scatter,
     NULL,  // open_gather
     NULL,  // get_iv
     aead_tls_tag_len,
 };

 const EVP_AEAD *EVP_aead_aes_128_cbc_sha1_tls(void) {
   return &aead_aes_128_cbc_sha1_tls;
 }

 const EVP_AEAD *EVP_aead_aes_128_cbc_sha1_tls_implicit_iv(void) {
   return &aead_aes_128_cbc_sha1_tls_implicit_iv;
 }

 const EVP_AEAD *EVP_aead_aes_256_cbc_sha1_tls(void) {
   return &aead_aes_256_cbc_sha1_tls;
 }

 const EVP_AEAD *EVP_aead_aes_256_cbc_sha1_tls_implicit_iv(void) {
   return &aead_aes_256_cbc_sha1_tls_implicit_iv;
 }

 const EVP_AEAD *EVP_aead_des_ede3_cbc_sha1_tls(void) {
   return &aead_des_ede3_cbc_sha1_tls;
 }

 const EVP_AEAD *EVP_aead_des_ede3_cbc_sha1_tls_implicit_iv(void) {
   return &aead_des_ede3_cbc_sha1_tls_implicit_iv;
 }

 const EVP_AEAD *EVP_aead_null_sha1_tls(void) { return &aead_null_sha1_tls; }
	/* 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 <assert.h>
	#include <limits.h>
	#include <string.h>

	#include <openssl/aead.h>
	#include <openssl/cipher.h>
	#include <openssl/err.h>
	#include <openssl/hmac.h>
	#include <openssl/md5.h>
	#include <openssl/mem.h>
	#include <openssl/sha.h>

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


	typedef struct {
	EVP_CIPHER_CTX cipher_ctx;
	HMAC_CTX hmac_ctx;
	// mac_key is the portion of the key used for the MAC. It is retained
	// separately for the constant-time CBC code.
	uint8_t mac_key[EVP_MAX_MD_SIZE];
	uint8_t mac_key_len;
	// implicit_iv is one iff this is a pre-TLS-1.1 CBC cipher without an explicit
	// IV.
	char implicit_iv;
	} AEAD_TLS_CTX;

	static_assert(EVP_MAX_MD_SIZE < 256, "mac_key_len does not fit in uint8_t");

	static_assert(sizeof(((EVP_AEAD_CTX *)NULL)->state) >= sizeof(AEAD_TLS_CTX),
	"AEAD state is too small");
	static_assert(alignof(union evp_aead_ctx_st_state) >= alignof(AEAD_TLS_CTX),
	"AEAD state has insufficient alignment");

	static void aead_tls_cleanup(EVP_AEAD_CTX *ctx) {
	AEAD_TLS_CTX tls_ctx = (AEAD_TLS_CTX )&ctx->state;
	EVP_CIPHER_CTX_cleanup(&tls_ctx->cipher_ctx);
	HMAC_CTX_cleanup(&tls_ctx->hmac_ctx);
	}

	static int aead_tls_init(EVP_AEAD_CTX ctx, const uint8_t key, size_t key_len,
	size_t tag_len, enum evp_aead_direction_t dir,
	const EVP_CIPHER cipher, const EVP_MD md,
	char implicit_iv) {
	if (tag_len != EVP_AEAD_DEFAULT_TAG_LENGTH &&
	tag_len != EVP_MD_size(md)) {
	OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_UNSUPPORTED_TAG_SIZE);
	return 0;
	}

	if (key_len != EVP_AEAD_key_length(ctx->aead)) {
	OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_BAD_KEY_LENGTH);
	return 0;
	}

	size_t mac_key_len = EVP_MD_size(md);
	size_t enc_key_len = EVP_CIPHER_key_length(cipher);
	assert(mac_key_len + enc_key_len +
	(implicit_iv ? EVP_CIPHER_iv_length(cipher) : 0) == key_len);

	AEAD_TLS_CTX tls_ctx = (AEAD_TLS_CTX )&ctx->state;
	EVP_CIPHER_CTX_init(&tls_ctx->cipher_ctx);
	HMAC_CTX_init(&tls_ctx->hmac_ctx);
	assert(mac_key_len <= EVP_MAX_MD_SIZE);
	OPENSSL_memcpy(tls_ctx->mac_key, key, mac_key_len);
	tls_ctx->mac_key_len = (uint8_t)mac_key_len;
	tls_ctx->implicit_iv = implicit_iv;

	if (!EVP_CipherInit_ex(&tls_ctx->cipher_ctx, cipher, NULL, &key[mac_key_len],
	implicit_iv ? &key[mac_key_len + enc_key_len] : NULL,
	dir == evp_aead_seal) \|\|
	!HMAC_Init_ex(&tls_ctx->hmac_ctx, key, mac_key_len, md, NULL)) {
	aead_tls_cleanup(ctx);
	return 0;
	}
	EVP_CIPHER_CTX_set_padding(&tls_ctx->cipher_ctx, 0);

	return 1;
	}

	static size_t aead_tls_tag_len(const EVP_AEAD_CTX *ctx, const size_t in_len,
	const size_t extra_in_len) {
	assert(extra_in_len == 0);
	const AEAD_TLS_CTX tls_ctx = (AEAD_TLS_CTX )&ctx->state;

	const size_t hmac_len = HMAC_size(&tls_ctx->hmac_ctx);
	if (EVP_CIPHER_CTX_mode(&tls_ctx->cipher_ctx) != EVP_CIPH_CBC_MODE) {
	// The NULL cipher.
	return hmac_len;
	}

	const size_t block_size = EVP_CIPHER_CTX_block_size(&tls_ctx->cipher_ctx);
	// An overflow of \|in_len + hmac_len\| doesn't affect the result mod
	// \|block_size\|, provided that \|block_size\| is a smaller power of two.
	assert(block_size != 0 && (block_size & (block_size - 1)) == 0);
	const size_t pad_len = block_size - (in_len + hmac_len) % block_size;
	return hmac_len + pad_len;
	}

	static int aead_tls_seal_scatter(const EVP_AEAD_CTX ctx, uint8_t out,
	uint8_t out_tag, size_t out_tag_len,
	const size_t max_out_tag_len,
	const uint8_t *nonce, const size_t nonce_len,
	const uint8_t *in, const size_t in_len,
	const uint8_t *extra_in,
	const size_t extra_in_len, const uint8_t *ad,
	const size_t ad_len) {
	AEAD_TLS_CTX tls_ctx = (AEAD_TLS_CTX )&ctx->state;

	if (!tls_ctx->cipher_ctx.encrypt) {
	// Unlike a normal AEAD, a TLS AEAD may only be used in one direction.
	OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_INVALID_OPERATION);
	return 0;
	}

	if (in_len > INT_MAX) {
	// EVP_CIPHER takes int as input.
	OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_TOO_LARGE);
	return 0;
	}

	if (max_out_tag_len < aead_tls_tag_len(ctx, in_len, extra_in_len)) {
	OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_BUFFER_TOO_SMALL);
	return 0;
	}

	if (nonce_len != EVP_AEAD_nonce_length(ctx->aead)) {
	OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_INVALID_NONCE_SIZE);
	return 0;
	}

	if (ad_len != 13 - 2 /* length bytes */) {
	OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_INVALID_AD_SIZE);
	return 0;
	}

	// To allow for CBC mode which changes cipher length, \|ad\| doesn't include the
	// length for legacy ciphers.
	uint8_t ad_extra[2];
	ad_extra[0] = (uint8_t)(in_len >> 8);
	ad_extra[1] = (uint8_t)(in_len & 0xff);

	// Compute the MAC. This must be first in case the operation is being done
	// in-place.
	uint8_t mac[EVP_MAX_MD_SIZE];
	unsigned mac_len;
	if (!HMAC_Init_ex(&tls_ctx->hmac_ctx, NULL, 0, NULL, NULL) \|\|
	!HMAC_Update(&tls_ctx->hmac_ctx, ad, ad_len) \|\|
	!HMAC_Update(&tls_ctx->hmac_ctx, ad_extra, sizeof(ad_extra)) \|\|
	!HMAC_Update(&tls_ctx->hmac_ctx, in, in_len) \|\|
	!HMAC_Final(&tls_ctx->hmac_ctx, mac, &mac_len)) {
	return 0;
	}

	// Configure the explicit IV.
	if (EVP_CIPHER_CTX_mode(&tls_ctx->cipher_ctx) == EVP_CIPH_CBC_MODE &&
	!tls_ctx->implicit_iv &&
	!EVP_EncryptInit_ex(&tls_ctx->cipher_ctx, NULL, NULL, NULL, nonce)) {
	return 0;
	}

	// Encrypt the input.
	int len;
	if (!EVP_EncryptUpdate(&tls_ctx->cipher_ctx, out, &len, in, (int)in_len)) {
	return 0;
	}

	unsigned block_size = EVP_CIPHER_CTX_block_size(&tls_ctx->cipher_ctx);

	// Feed the MAC into the cipher in two steps. First complete the final partial
	// block from encrypting the input and split the result between \|out\| and
	// \|out_tag\|. Then feed the rest.

	const size_t early_mac_len = (block_size - (in_len % block_size)) % block_size;
	if (early_mac_len != 0) {
	assert(len + block_size - early_mac_len == in_len);
	uint8_t buf[EVP_MAX_BLOCK_LENGTH];
	int buf_len;
	if (!EVP_EncryptUpdate(&tls_ctx->cipher_ctx, buf, &buf_len, mac,
	(int)early_mac_len)) {
	return 0;
	}
	assert(buf_len == (int)block_size);
	OPENSSL_memcpy(out + len, buf, block_size - early_mac_len);
	OPENSSL_memcpy(out_tag, buf + block_size - early_mac_len, early_mac_len);
	}
	size_t tag_len = early_mac_len;

	if (!EVP_EncryptUpdate(&tls_ctx->cipher_ctx, out_tag + tag_len, &len,
	mac + tag_len, mac_len - tag_len)) {
	return 0;
	}
	tag_len += len;

	if (block_size > 1) {
	assert(block_size <= 256);
	assert(EVP_CIPHER_CTX_mode(&tls_ctx->cipher_ctx) == EVP_CIPH_CBC_MODE);

	// Compute padding and feed that into the cipher.
	uint8_t padding[256];
	unsigned padding_len = block_size - ((in_len + mac_len) % block_size);
	OPENSSL_memset(padding, padding_len - 1, padding_len);
	if (!EVP_EncryptUpdate(&tls_ctx->cipher_ctx, out_tag + tag_len, &len,
	padding, (int)padding_len)) {
	return 0;
	}
	tag_len += len;
	}

	if (!EVP_EncryptFinal_ex(&tls_ctx->cipher_ctx, out_tag + tag_len, &len)) {
	return 0;
	}
	assert(len == 0); // Padding is explicit.
	assert(tag_len == aead_tls_tag_len(ctx, in_len, extra_in_len));

	*out_tag_len = tag_len;
	return 1;
	}

	static int aead_tls_open(const EVP_AEAD_CTX ctx, uint8_t out, size_t *out_len,
	size_t max_out_len, const uint8_t *nonce,
	size_t nonce_len, const uint8_t *in, size_t in_len,
	const uint8_t *ad, size_t ad_len) {
	AEAD_TLS_CTX tls_ctx = (AEAD_TLS_CTX )&ctx->state;

	if (tls_ctx->cipher_ctx.encrypt) {
	// Unlike a normal AEAD, a TLS AEAD may only be used in one direction.
	OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_INVALID_OPERATION);
	return 0;
	}

	if (in_len < HMAC_size(&tls_ctx->hmac_ctx)) {
	OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_BAD_DECRYPT);
	return 0;
	}

	if (max_out_len < in_len) {
	// This requires that the caller provide space for the MAC, even though it
	// will always be removed on return.
	OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_BUFFER_TOO_SMALL);
	return 0;
	}

	if (nonce_len != EVP_AEAD_nonce_length(ctx->aead)) {
	OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_INVALID_NONCE_SIZE);
	return 0;
	}

	if (ad_len != 13 - 2 /* length bytes */) {
	OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_INVALID_AD_SIZE);
	return 0;
	}

	if (in_len > INT_MAX) {
	// EVP_CIPHER takes int as input.
	OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_TOO_LARGE);
	return 0;
	}

	// Configure the explicit IV.
	if (EVP_CIPHER_CTX_mode(&tls_ctx->cipher_ctx) == EVP_CIPH_CBC_MODE &&
	!tls_ctx->implicit_iv &&
	!EVP_DecryptInit_ex(&tls_ctx->cipher_ctx, NULL, NULL, NULL, nonce)) {
	return 0;
	}

	// Decrypt to get the plaintext + MAC + padding.
	size_t total = 0;
	int len;
	if (!EVP_DecryptUpdate(&tls_ctx->cipher_ctx, out, &len, in, (int)in_len)) {
	return 0;
	}
	total += len;
	if (!EVP_DecryptFinal_ex(&tls_ctx->cipher_ctx, out + total, &len)) {
	return 0;
	}
	total += len;
	assert(total == in_len);

	CONSTTIME_SECRET(out, total);

	// Remove CBC padding. Code from here on is timing-sensitive with respect to
	// \|padding_ok\| and \|data_plus_mac_len\| for CBC ciphers.
	size_t data_plus_mac_len;
	crypto_word_t padding_ok;
	if (EVP_CIPHER_CTX_mode(&tls_ctx->cipher_ctx) == EVP_CIPH_CBC_MODE) {
	if (!EVP_tls_cbc_remove_padding(
	&padding_ok, &data_plus_mac_len, out, total,
	EVP_CIPHER_CTX_block_size(&tls_ctx->cipher_ctx),
	HMAC_size(&tls_ctx->hmac_ctx))) {
	// Publicly invalid. This can be rejected in non-constant time.
	OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_BAD_DECRYPT);
	return 0;
	}
	} else {
	padding_ok = CONSTTIME_TRUE_W;
	data_plus_mac_len = total;
	// \|data_plus_mac_len\| = \|total\| = \|in_len\| at this point. \|in_len\| has
	// already been checked against the MAC size at the top of the function.
	assert(data_plus_mac_len >= HMAC_size(&tls_ctx->hmac_ctx));
	}
	size_t data_len = data_plus_mac_len - HMAC_size(&tls_ctx->hmac_ctx);

	// At this point, if the padding is valid, the first \|data_plus_mac_len\| bytes
	// after \|out\| are the plaintext and MAC. Otherwise, \|data_plus_mac_len\| is
	// still large enough to extract a MAC, but it will be irrelevant.

	// To allow for CBC mode which changes cipher length, \|ad\| doesn't include the
	// length for legacy ciphers.
	uint8_t ad_fixed[13];
	OPENSSL_memcpy(ad_fixed, ad, 11);
	ad_fixed[11] = (uint8_t)(data_len >> 8);
	ad_fixed[12] = (uint8_t)(data_len & 0xff);
	ad_len += 2;

	// Compute the MAC and extract the one in the record.
	uint8_t mac[EVP_MAX_MD_SIZE];
	size_t mac_len;
	uint8_t record_mac_tmp[EVP_MAX_MD_SIZE];
	uint8_t *record_mac;
	if (EVP_CIPHER_CTX_mode(&tls_ctx->cipher_ctx) == EVP_CIPH_CBC_MODE &&
	EVP_tls_cbc_record_digest_supported(tls_ctx->hmac_ctx.md)) {
	if (!EVP_tls_cbc_digest_record(tls_ctx->hmac_ctx.md, mac, &mac_len,
	ad_fixed, out, data_len, total,
	tls_ctx->mac_key, tls_ctx->mac_key_len)) {
	OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_BAD_DECRYPT);
	return 0;
	}
	assert(mac_len == HMAC_size(&tls_ctx->hmac_ctx));

	record_mac = record_mac_tmp;
	EVP_tls_cbc_copy_mac(record_mac, mac_len, out, data_plus_mac_len, total);
	} else {
	// We should support the constant-time path for all CBC-mode ciphers
	// implemented.
	assert(EVP_CIPHER_CTX_mode(&tls_ctx->cipher_ctx) != EVP_CIPH_CBC_MODE);

	unsigned mac_len_u;
	if (!HMAC_Init_ex(&tls_ctx->hmac_ctx, NULL, 0, NULL, NULL) \|\|
	!HMAC_Update(&tls_ctx->hmac_ctx, ad_fixed, ad_len) \|\|
	!HMAC_Update(&tls_ctx->hmac_ctx, out, data_len) \|\|
	!HMAC_Final(&tls_ctx->hmac_ctx, mac, &mac_len_u)) {
	return 0;
	}
	mac_len = mac_len_u;

	assert(mac_len == HMAC_size(&tls_ctx->hmac_ctx));
	record_mac = &out[data_len];
	}

	// Perform the MAC check and the padding check in constant-time. It should be
	// safe to simply perform the padding check first, but it would not be under a
	// different choice of MAC location on padding failure. See
	// EVP_tls_cbc_remove_padding.
	crypto_word_t good =
	constant_time_eq_int(CRYPTO_memcmp(record_mac, mac, mac_len), 0);
	good &= padding_ok;
	CONSTTIME_DECLASSIFY(&good, sizeof(good));
	if (!good) {
	OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_BAD_DECRYPT);
	return 0;
	}

	CONSTTIME_DECLASSIFY(&data_len, sizeof(data_len));
	CONSTTIME_DECLASSIFY(out, data_len);

	// End of timing-sensitive code.

	*out_len = data_len;
	return 1;
	}

	static int aead_aes_128_cbc_sha1_tls_init(EVP_AEAD_CTX ctx, const uint8_t key,
	size_t key_len, size_t tag_len,
	enum evp_aead_direction_t dir) {
	return aead_tls_init(ctx, key, key_len, tag_len, dir, EVP_aes_128_cbc(),
	EVP_sha1(), 0);
	}

	static int aead_aes_128_cbc_sha1_tls_implicit_iv_init(
	EVP_AEAD_CTX ctx, const uint8_t key, size_t key_len, size_t tag_len,
	enum evp_aead_direction_t dir) {
	return aead_tls_init(ctx, key, key_len, tag_len, dir, EVP_aes_128_cbc(),
	EVP_sha1(), 1);
	}

	static int aead_aes_256_cbc_sha1_tls_init(EVP_AEAD_CTX ctx, const uint8_t key,
	size_t key_len, size_t tag_len,
	enum evp_aead_direction_t dir) {
	return aead_tls_init(ctx, key, key_len, tag_len, dir, EVP_aes_256_cbc(),
	EVP_sha1(), 0);
	}

	static int aead_aes_256_cbc_sha1_tls_implicit_iv_init(
	EVP_AEAD_CTX ctx, const uint8_t key, size_t key_len, size_t tag_len,
	enum evp_aead_direction_t dir) {
	return aead_tls_init(ctx, key, key_len, tag_len, dir, EVP_aes_256_cbc(),
	EVP_sha1(), 1);
	}

	static int aead_des_ede3_cbc_sha1_tls_init(EVP_AEAD_CTX *ctx,
	const uint8_t *key, size_t key_len,
	size_t tag_len,
	enum evp_aead_direction_t dir) {
	return aead_tls_init(ctx, key, key_len, tag_len, dir, EVP_des_ede3_cbc(),
	EVP_sha1(), 0);
	}

	static int aead_des_ede3_cbc_sha1_tls_implicit_iv_init(
	EVP_AEAD_CTX ctx, const uint8_t key, size_t key_len, size_t tag_len,
	enum evp_aead_direction_t dir) {
	return aead_tls_init(ctx, key, key_len, tag_len, dir, EVP_des_ede3_cbc(),
	EVP_sha1(), 1);
	}

	static int aead_tls_get_iv(const EVP_AEAD_CTX ctx, const uint8_t *out_iv,
	size_t *out_iv_len) {
	const AEAD_TLS_CTX tls_ctx = (AEAD_TLS_CTX )&ctx->state;
	const size_t iv_len = EVP_CIPHER_CTX_iv_length(&tls_ctx->cipher_ctx);
	if (iv_len <= 1) {
	return 0;
	}

	*out_iv = tls_ctx->cipher_ctx.iv;
	*out_iv_len = iv_len;
	return 1;
	}

	static int aead_null_sha1_tls_init(EVP_AEAD_CTX ctx, const uint8_t key,
	size_t key_len, size_t tag_len,
	enum evp_aead_direction_t dir) {
	return aead_tls_init(ctx, key, key_len, tag_len, dir, EVP_enc_null(),
	EVP_sha1(), 1 /* implicit iv */);
	}

	static const EVP_AEAD aead_aes_128_cbc_sha1_tls = {
	SHA_DIGEST_LENGTH + 16, // key len (SHA1 + AES128)
	16, // nonce len (IV)
	16 + SHA_DIGEST_LENGTH, // overhead (padding + SHA1)
	SHA_DIGEST_LENGTH, // max tag length
	0, // seal_scatter_supports_extra_in

	NULL, // init
	aead_aes_128_cbc_sha1_tls_init,
	aead_tls_cleanup,
	aead_tls_open,
	aead_tls_seal_scatter,
	NULL, // open_gather
	NULL, // get_iv
	aead_tls_tag_len,
	};

	static const EVP_AEAD aead_aes_128_cbc_sha1_tls_implicit_iv = {
	SHA_DIGEST_LENGTH + 16 + 16, // key len (SHA1 + AES128 + IV)
	0, // nonce len
	16 + SHA_DIGEST_LENGTH, // overhead (padding + SHA1)
	SHA_DIGEST_LENGTH, // max tag length
	0, // seal_scatter_supports_extra_in

	NULL, // init
	aead_aes_128_cbc_sha1_tls_implicit_iv_init,
	aead_tls_cleanup,
	aead_tls_open,
	aead_tls_seal_scatter,
	NULL, // open_gather
	aead_tls_get_iv, // get_iv
	aead_tls_tag_len,
	};

	static const EVP_AEAD aead_aes_256_cbc_sha1_tls = {
	SHA_DIGEST_LENGTH + 32, // key len (SHA1 + AES256)
	16, // nonce len (IV)
	16 + SHA_DIGEST_LENGTH, // overhead (padding + SHA1)
	SHA_DIGEST_LENGTH, // max tag length
	0, // seal_scatter_supports_extra_in

	NULL, // init
	aead_aes_256_cbc_sha1_tls_init,
	aead_tls_cleanup,
	aead_tls_open,
	aead_tls_seal_scatter,
	NULL, // open_gather
	NULL, // get_iv
	aead_tls_tag_len,
	};

	static const EVP_AEAD aead_aes_256_cbc_sha1_tls_implicit_iv = {
	SHA_DIGEST_LENGTH + 32 + 16, // key len (SHA1 + AES256 + IV)
	0, // nonce len
	16 + SHA_DIGEST_LENGTH, // overhead (padding + SHA1)
	SHA_DIGEST_LENGTH, // max tag length
	0, // seal_scatter_supports_extra_in

	NULL, // init
	aead_aes_256_cbc_sha1_tls_implicit_iv_init,
	aead_tls_cleanup,
	aead_tls_open,
	aead_tls_seal_scatter,
	NULL, // open_gather
	aead_tls_get_iv, // get_iv
	aead_tls_tag_len,
	};

	static const EVP_AEAD aead_des_ede3_cbc_sha1_tls = {
	SHA_DIGEST_LENGTH + 24, // key len (SHA1 + 3DES)
	8, // nonce len (IV)
	8 + SHA_DIGEST_LENGTH, // overhead (padding + SHA1)
	SHA_DIGEST_LENGTH, // max tag length
	0, // seal_scatter_supports_extra_in

	NULL, // init
	aead_des_ede3_cbc_sha1_tls_init,
	aead_tls_cleanup,
	aead_tls_open,
	aead_tls_seal_scatter,
	NULL, // open_gather
	NULL, // get_iv
	aead_tls_tag_len,
	};

	static const EVP_AEAD aead_des_ede3_cbc_sha1_tls_implicit_iv = {
	SHA_DIGEST_LENGTH + 24 + 8, // key len (SHA1 + 3DES + IV)
	0, // nonce len
	8 + SHA_DIGEST_LENGTH, // overhead (padding + SHA1)
	SHA_DIGEST_LENGTH, // max tag length
	0, // seal_scatter_supports_extra_in

	NULL, // init
	aead_des_ede3_cbc_sha1_tls_implicit_iv_init,
	aead_tls_cleanup,
	aead_tls_open,
	aead_tls_seal_scatter,
	NULL, // open_gather
	aead_tls_get_iv, // get_iv
	aead_tls_tag_len,
	};

	static const EVP_AEAD aead_null_sha1_tls = {
	SHA_DIGEST_LENGTH, // key len
	0, // nonce len
	SHA_DIGEST_LENGTH, // overhead (SHA1)
	SHA_DIGEST_LENGTH, // max tag length
	0, // seal_scatter_supports_extra_in

	NULL, // init
	aead_null_sha1_tls_init,
	aead_tls_cleanup,
	aead_tls_open,
	aead_tls_seal_scatter,
	NULL, // open_gather
	NULL, // get_iv
	aead_tls_tag_len,
	};

	const EVP_AEAD *EVP_aead_aes_128_cbc_sha1_tls(void) {
	return &aead_aes_128_cbc_sha1_tls;
	}

	const EVP_AEAD *EVP_aead_aes_128_cbc_sha1_tls_implicit_iv(void) {
	return &aead_aes_128_cbc_sha1_tls_implicit_iv;
	}

	const EVP_AEAD *EVP_aead_aes_256_cbc_sha1_tls(void) {
	return &aead_aes_256_cbc_sha1_tls;
	}

	const EVP_AEAD *EVP_aead_aes_256_cbc_sha1_tls_implicit_iv(void) {
	return &aead_aes_256_cbc_sha1_tls_implicit_iv;
	}

	const EVP_AEAD *EVP_aead_des_ede3_cbc_sha1_tls(void) {
	return &aead_des_ede3_cbc_sha1_tls;
	}

	const EVP_AEAD *EVP_aead_des_ede3_cbc_sha1_tls_implicit_iv(void) {
	return &aead_des_ede3_cbc_sha1_tls_implicit_iv;
	}

	const EVP_AEAD *EVP_aead_null_sha1_tls(void) { return &aead_null_sha1_tls; }