crypto/cipher/e_aesctrhmac.cc - boringssl - Git at Google

 // Copyright 2017 The BoringSSL Authors
 //
 // 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 <openssl/aead.h>

 #include <assert.h>

 #include <openssl/cipher.h>
 #include <openssl/crypto.h>
 #include <openssl/err.h>
 #include <openssl/sha.h>

 #include "../fipsmodule/aes/internal.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_ctr32| 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);

   CRYPTO_ctr128_encrypt_ctr32(in, out, len, &aes_ctx->ks.ks, counter,
                               partial_block_buffer, &partial_block_offset,
                               aes_ctx->ctr);
 }

 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;
 }
	// Copyright 2017 The BoringSSL Authors
	//
	// 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 <openssl/aead.h>

	#include <assert.h>

	#include <openssl/cipher.h>
	#include <openssl/crypto.h>
	#include <openssl/err.h>
	#include <openssl/sha.h>

	#include "../fipsmodule/aes/internal.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_ctr32\| 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);

	CRYPTO_ctr128_encrypt_ctr32(in, out, len, &aes_ctx->ks.ks, counter,
	partial_block_buffer, &partial_block_offset,
	aes_ctx->ctr);
	}

	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;
	}