/usr/include/mbedtls/gcm.h is in libmbedtls-dev 2.2.1-2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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* \file gcm.h
*
* \brief Galois/Counter mode for 128-bit block ciphers
*
* Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
* SPDX-License-Identifier: Apache-2.0
*
* 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
*
* http://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.
*
* This file is part of mbed TLS (https://tls.mbed.org)
*/
#ifndef MBEDTLS_GCM_H
#define MBEDTLS_GCM_H
#include "cipher.h"
#include <stdint.h>
#define MBEDTLS_GCM_ENCRYPT 1
#define MBEDTLS_GCM_DECRYPT 0
#define MBEDTLS_ERR_GCM_AUTH_FAILED -0x0012 /**< Authenticated decryption failed. */
#define MBEDTLS_ERR_GCM_BAD_INPUT -0x0014 /**< Bad input parameters to function. */
#ifdef __cplusplus
extern "C" {
#endif
/**
* \brief GCM context structure
*/
typedef struct {
mbedtls_cipher_context_t cipher_ctx;/*!< cipher context used */
uint64_t HL[16]; /*!< Precalculated HTable */
uint64_t HH[16]; /*!< Precalculated HTable */
uint64_t len; /*!< Total data length */
uint64_t add_len; /*!< Total add length */
unsigned char base_ectr[16];/*!< First ECTR for tag */
unsigned char y[16]; /*!< Y working value */
unsigned char buf[16]; /*!< buf working value */
int mode; /*!< Encrypt or Decrypt */
}
mbedtls_gcm_context;
/**
* \brief Initialize GCM context (just makes references valid)
* Makes the context ready for mbedtls_gcm_setkey() or
* mbedtls_gcm_free().
*
* \param ctx GCM context to initialize
*/
void mbedtls_gcm_init( mbedtls_gcm_context *ctx );
/**
* \brief GCM initialization (encryption)
*
* \param ctx GCM context to be initialized
* \param cipher cipher to use (a 128-bit block cipher)
* \param key encryption key
* \param keybits must be 128, 192 or 256
*
* \return 0 if successful, or a cipher specific error code
*/
int mbedtls_gcm_setkey( mbedtls_gcm_context *ctx,
mbedtls_cipher_id_t cipher,
const unsigned char *key,
unsigned int keybits );
/**
* \brief GCM buffer encryption/decryption using a block cipher
*
* \note On encryption, the output buffer can be the same as the input buffer.
* On decryption, the output buffer cannot be the same as input buffer.
* If buffers overlap, the output buffer must trail at least 8 bytes
* behind the input buffer.
*
* \param ctx GCM context
* \param mode MBEDTLS_GCM_ENCRYPT or MBEDTLS_GCM_DECRYPT
* \param length length of the input data
* \param iv initialization vector
* \param iv_len length of IV
* \param add additional data
* \param add_len length of additional data
* \param input buffer holding the input data
* \param output buffer for holding the output data
* \param tag_len length of the tag to generate
* \param tag buffer for holding the tag
*
* \return 0 if successful
*/
int mbedtls_gcm_crypt_and_tag( mbedtls_gcm_context *ctx,
int mode,
size_t length,
const unsigned char *iv,
size_t iv_len,
const unsigned char *add,
size_t add_len,
const unsigned char *input,
unsigned char *output,
size_t tag_len,
unsigned char *tag );
/**
* \brief GCM buffer authenticated decryption using a block cipher
*
* \note On decryption, the output buffer cannot be the same as input buffer.
* If buffers overlap, the output buffer must trail at least 8 bytes
* behind the input buffer.
*
* \param ctx GCM context
* \param length length of the input data
* \param iv initialization vector
* \param iv_len length of IV
* \param add additional data
* \param add_len length of additional data
* \param tag buffer holding the tag
* \param tag_len length of the tag
* \param input buffer holding the input data
* \param output buffer for holding the output data
*
* \return 0 if successful and authenticated,
* MBEDTLS_ERR_GCM_AUTH_FAILED if tag does not match
*/
int mbedtls_gcm_auth_decrypt( mbedtls_gcm_context *ctx,
size_t length,
const unsigned char *iv,
size_t iv_len,
const unsigned char *add,
size_t add_len,
const unsigned char *tag,
size_t tag_len,
const unsigned char *input,
unsigned char *output );
/**
* \brief Generic GCM stream start function
*
* \param ctx GCM context
* \param mode MBEDTLS_GCM_ENCRYPT or MBEDTLS_GCM_DECRYPT
* \param iv initialization vector
* \param iv_len length of IV
* \param add additional data (or NULL if length is 0)
* \param add_len length of additional data
*
* \return 0 if successful
*/
int mbedtls_gcm_starts( mbedtls_gcm_context *ctx,
int mode,
const unsigned char *iv,
size_t iv_len,
const unsigned char *add,
size_t add_len );
/**
* \brief Generic GCM update function. Encrypts/decrypts using the
* given GCM context. Expects input to be a multiple of 16
* bytes! Only the last call before mbedtls_gcm_finish() can be less
* than 16 bytes!
*
* \note On decryption, the output buffer cannot be the same as input buffer.
* If buffers overlap, the output buffer must trail at least 8 bytes
* behind the input buffer.
*
* \param ctx GCM context
* \param length length of the input data
* \param input buffer holding the input data
* \param output buffer for holding the output data
*
* \return 0 if successful or MBEDTLS_ERR_GCM_BAD_INPUT
*/
int mbedtls_gcm_update( mbedtls_gcm_context *ctx,
size_t length,
const unsigned char *input,
unsigned char *output );
/**
* \brief Generic GCM finalisation function. Wraps up the GCM stream
* and generates the tag. The tag can have a maximum length of
* 16 bytes.
*
* \param ctx GCM context
* \param tag buffer for holding the tag (may be NULL if tag_len is 0)
* \param tag_len length of the tag to generate
*
* \return 0 if successful or MBEDTLS_ERR_GCM_BAD_INPUT
*/
int mbedtls_gcm_finish( mbedtls_gcm_context *ctx,
unsigned char *tag,
size_t tag_len );
/**
* \brief Free a GCM context and underlying cipher sub-context
*
* \param ctx GCM context to free
*/
void mbedtls_gcm_free( mbedtls_gcm_context *ctx );
/**
* \brief Checkup routine
*
* \return 0 if successful, or 1 if the test failed
*/
int mbedtls_gcm_self_test( int verbose );
#ifdef __cplusplus
}
#endif
#endif /* gcm.h */
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