include/openssl/cmac.h

// Copyright 2015 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.

#ifndef OPENSSL_HEADER_CMAC_H
#define OPENSSL_HEADER_CMAC_H

#include <openssl/base.h>   // IWYU pragma: export

#if defined(__cplusplus)
extern "C" {
#endif


// CMAC.
//
// CMAC is a MAC based on AES-CBC and defined in
// https://tools.ietf.org/html/rfc4493#section-2.3.


// One-shot functions.

// AES_CMAC calculates the 16-byte, CMAC authenticator of `in_len` bytes of
// `in` and writes it to `out`. The `key_len` may be 16 or 32 bytes to select
// between AES-128 and AES-256. It returns one on success or zero on error.
OPENSSL_EXPORT int AES_CMAC(uint8_t out[16], const uint8_t *key, size_t key_len,
                            const uint8_t *in, size_t in_len);


// Incremental interface.

// CMAC_CTX_new allocates a fresh `CMAC_CTX` and returns it, or NULL on
// error.
OPENSSL_EXPORT CMAC_CTX *CMAC_CTX_new(void);

// CMAC_CTX_free frees a `CMAC_CTX`.
OPENSSL_EXPORT void CMAC_CTX_free(CMAC_CTX *ctx);

// CMAC_CTX_copy sets `out` to be a duplicate of the current state `in`. It
// returns one on success and zero on error.
OPENSSL_EXPORT int CMAC_CTX_copy(CMAC_CTX *out, const CMAC_CTX *in);

// CMAC_Init configures `ctx` to use the given `key` and `cipher`. The CMAC RFC
// only specifies the use of AES-128 thus `key_len` should be 16 and `cipher`
// should be `EVP_aes_128_cbc()`. However, this implementation also supports
// AES-256 by setting `key_len` to 32 and `cipher` to `EVP_aes_256_cbc()`. The
// `engine` argument is ignored.
//
// It returns one on success or zero on error.
OPENSSL_EXPORT int CMAC_Init(CMAC_CTX *ctx, const void *key, size_t key_len,
                             const EVP_CIPHER *cipher, ENGINE *engine);


// CMAC_Reset resets `ctx` so that a fresh message can be authenticated.
OPENSSL_EXPORT int CMAC_Reset(CMAC_CTX *ctx);

// CMAC_Update processes `in_len` bytes of message from `in`. It returns one on
// success or zero on error.
OPENSSL_EXPORT int CMAC_Update(CMAC_CTX *ctx, const uint8_t *in, size_t in_len);

// CMAC_Final sets `*out_len` to 16 and, if `out` is not NULL, writes 16 bytes
// of authenticator to it. It returns one on success or zero on error.
OPENSSL_EXPORT int CMAC_Final(CMAC_CTX *ctx, uint8_t *out, size_t *out_len);


#if defined(__cplusplus)
}  // extern C

extern "C++" {

BSSL_NAMESPACE_BEGIN

BORINGSSL_MAKE_DELETER(CMAC_CTX, CMAC_CTX_free)

BSSL_NAMESPACE_END

}  // extern C++

#endif

#endif  // OPENSSL_HEADER_CMAC_H