crypto/cipher/e_aesctrhmac.cc - boringssl.git - 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/sha2.h>
 #include <openssl/span.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 *)nullptr)->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, nullptr, &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, bssl::Span<const CRYPTO_IVEC> aadvecs,
     const uint8_t *nonce, bssl::Span<const CRYPTO_IOVEC> iovecs, bool encrypt) {
   size_t ad_len = bssl::iovec::TotalLength(aadvecs);
   SHA256_CTX sha256;
   OPENSSL_memcpy(&sha256, inner_init_state, sizeof(sha256));
   hmac_update_uint64(&sha256, ad_len);
   hmac_update_uint64(&sha256, bssl::iovec::TotalLength(iovecs));
   SHA256_Update(&sha256, nonce, EVP_AEAD_AES_CTR_HMAC_SHA256_NONCE_LEN);
   for (const CRYPTO_IVEC &aadvec : aadvecs) {
     SHA256_Update(&sha256, aadvec.in, aadvec.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);

   for (const CRYPTO_IOVEC &iovec : iovecs) {
     SHA256_Update(&sha256, encrypt ? iovec.out : iovec.in, iovec.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,
     bssl::Span<const CRYPTO_IOVEC> iovecs, const uint8_t *nonce) {
   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);

   for (const CRYPTO_IOVEC &iovec : iovecs) {
     CRYPTO_ctr128_encrypt_ctr32(iovec.in, iovec.out, iovec.len, &aes_ctx->ks.ks,
                                 counter, partial_block_buffer,
                                 &partial_block_offset, aes_ctx->ctr);
   }
 }

 static int aead_aes_ctr_hmac_sha256_sealv(
     const EVP_AEAD_CTX *ctx, bssl::Span<const CRYPTO_IOVEC> iovecs,
     bssl::Span<uint8_t> out_tag, size_t *out_tag_len,
     bssl::Span<const uint8_t> nonce, bssl::Span<const CRYPTO_IVEC> aadvecs) {
   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 = bssl::iovec::TotalLength(iovecs);

   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 (out_tag.size() < ctx->tag_len) {
     OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_BUFFER_TOO_SMALL);
     return 0;
   }

   if (nonce.size() != 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, iovecs, nonce.data());

   uint8_t hmac_result[SHA256_DIGEST_LENGTH];
   hmac_calculate(hmac_result, &aes_ctx->inner_init_state,
                  &aes_ctx->outer_init_state, aadvecs, nonce.data(), iovecs,
                  /*encrypt=*/true);
   CopyToPrefix(bssl::Span(hmac_result).first(ctx->tag_len), out_tag);
   *out_tag_len = ctx->tag_len;

   return 1;
 }

 static int aead_aes_ctr_hmac_sha256_openv_detached(
     const EVP_AEAD_CTX *ctx, bssl::Span<const CRYPTO_IOVEC> iovecs,
     bssl::Span<const uint8_t> nonce, bssl::Span<const uint8_t> in_tag,
     bssl::Span<const CRYPTO_IVEC> aadvecs) {
   const struct aead_aes_ctr_hmac_sha256_ctx *aes_ctx =
       (struct aead_aes_ctr_hmac_sha256_ctx *)&ctx->state;

   if (in_tag.size() != ctx->tag_len) {
     OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_BAD_DECRYPT);
     return 0;
   }

   if (nonce.size() != 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, aadvecs, nonce.data(), iovecs,
                  /*encrypt=*/false);
   if (CRYPTO_memcmp(hmac_result, in_tag.data(), ctx->tag_len) != 0) {
     OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_BAD_DECRYPT);
     return 0;
   }

   aead_aes_ctr_hmac_sha256_crypt(aes_ctx, iovecs, nonce.data());

   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

     aead_aes_ctr_hmac_sha256_init,
     nullptr /* init_with_direction */,
     aead_aes_ctr_hmac_sha256_cleanup,
     nullptr /* openv */,
     aead_aes_ctr_hmac_sha256_sealv,
     aead_aes_ctr_hmac_sha256_openv_detached,
     nullptr /* get_iv */,
     nullptr /* 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

     aead_aes_ctr_hmac_sha256_init,
     nullptr /* init_with_direction */,
     aead_aes_ctr_hmac_sha256_cleanup,
     nullptr /* openv */,
     aead_aes_ctr_hmac_sha256_sealv,
     aead_aes_ctr_hmac_sha256_openv_detached,
     nullptr /* get_iv */,
     nullptr /* 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/sha2.h>
	#include <openssl/span.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 *)nullptr)->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, nullptr, &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, bssl::Span<const CRYPTO_IVEC> aadvecs,
	const uint8_t *nonce, bssl::Span<const CRYPTO_IOVEC> iovecs, bool encrypt) {
	size_t ad_len = bssl::iovec::TotalLength(aadvecs);
	SHA256_CTX sha256;
	OPENSSL_memcpy(&sha256, inner_init_state, sizeof(sha256));
	hmac_update_uint64(&sha256, ad_len);
	hmac_update_uint64(&sha256, bssl::iovec::TotalLength(iovecs));
	SHA256_Update(&sha256, nonce, EVP_AEAD_AES_CTR_HMAC_SHA256_NONCE_LEN);
	for (const CRYPTO_IVEC &aadvec : aadvecs) {
	SHA256_Update(&sha256, aadvec.in, aadvec.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);

	for (const CRYPTO_IOVEC &iovec : iovecs) {
	SHA256_Update(&sha256, encrypt ? iovec.out : iovec.in, iovec.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,
	bssl::Span<const CRYPTO_IOVEC> iovecs, const uint8_t *nonce) {
	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);

	for (const CRYPTO_IOVEC &iovec : iovecs) {
	CRYPTO_ctr128_encrypt_ctr32(iovec.in, iovec.out, iovec.len, &aes_ctx->ks.ks,
	counter, partial_block_buffer,
	&partial_block_offset, aes_ctx->ctr);
	}
	}

	static int aead_aes_ctr_hmac_sha256_sealv(
	const EVP_AEAD_CTX *ctx, bssl::Span<const CRYPTO_IOVEC> iovecs,
	bssl::Span<uint8_t> out_tag, size_t *out_tag_len,
	bssl::Span<const uint8_t> nonce, bssl::Span<const CRYPTO_IVEC> aadvecs) {
	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 = bssl::iovec::TotalLength(iovecs);

	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 (out_tag.size() < ctx->tag_len) {
	OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_BUFFER_TOO_SMALL);
	return 0;
	}

	if (nonce.size() != 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, iovecs, nonce.data());

	uint8_t hmac_result[SHA256_DIGEST_LENGTH];
	hmac_calculate(hmac_result, &aes_ctx->inner_init_state,
	&aes_ctx->outer_init_state, aadvecs, nonce.data(), iovecs,
	/encrypt=/true);
	CopyToPrefix(bssl::Span(hmac_result).first(ctx->tag_len), out_tag);
	*out_tag_len = ctx->tag_len;

	return 1;
	}

	static int aead_aes_ctr_hmac_sha256_openv_detached(
	const EVP_AEAD_CTX *ctx, bssl::Span<const CRYPTO_IOVEC> iovecs,
	bssl::Span<const uint8_t> nonce, bssl::Span<const uint8_t> in_tag,
	bssl::Span<const CRYPTO_IVEC> aadvecs) {
	const struct aead_aes_ctr_hmac_sha256_ctx *aes_ctx =
	(struct aead_aes_ctr_hmac_sha256_ctx *)&ctx->state;

	if (in_tag.size() != ctx->tag_len) {
	OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_BAD_DECRYPT);
	return 0;
	}

	if (nonce.size() != 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, aadvecs, nonce.data(), iovecs,
	/encrypt=/false);
	if (CRYPTO_memcmp(hmac_result, in_tag.data(), ctx->tag_len) != 0) {
	OPENSSL_PUT_ERROR(CIPHER, CIPHER_R_BAD_DECRYPT);
	return 0;
	}

	aead_aes_ctr_hmac_sha256_crypt(aes_ctx, iovecs, nonce.data());

	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

	aead_aes_ctr_hmac_sha256_init,
	nullptr /* init_with_direction */,
	aead_aes_ctr_hmac_sha256_cleanup,
	nullptr /* openv */,
	aead_aes_ctr_hmac_sha256_sealv,
	aead_aes_ctr_hmac_sha256_openv_detached,
	nullptr /* get_iv */,
	nullptr /* 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

	aead_aes_ctr_hmac_sha256_init,
	nullptr /* init_with_direction */,
	aead_aes_ctr_hmac_sha256_cleanup,
	nullptr /* openv */,
	aead_aes_ctr_hmac_sha256_sealv,
	aead_aes_ctr_hmac_sha256_openv_detached,
	nullptr /* get_iv */,
	nullptr /* 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;
	}