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/**
* \file gcm.h
*
* \brief This file contains GCM definitions and functions.
*
* The Galois/Counter Mode (GCM) for 128-bit block ciphers is defined
* in <em>D. McGrew, J. Viega, The Galois/Counter Mode of Operation
* (GCM), Natl. Inst. Stand. Technol.</em>
*
* For more information on GCM, see <em>NIST SP 800-38D: Recommendation for
* Block Cipher Modes of Operation: Galois/Counter Mode (GCM) and GMAC</em>.
*
*/
/*
* Copyright The Mbed TLS Contributors
* 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.
*/
#ifndef MBEDTLS_GCM_H
#define MBEDTLS_GCM_H
#if !defined(MBEDTLS_CONFIG_FILE)
#include "mbedtls/config.h"
#else
#include MBEDTLS_CONFIG_FILE
#endif
#include "mbedtls/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. */
/* MBEDTLS_ERR_GCM_HW_ACCEL_FAILED is deprecated and should not be used. */
#define MBEDTLS_ERR_GCM_HW_ACCEL_FAILED -0x0013 /**< GCM hardware accelerator failed. */
#define MBEDTLS_ERR_GCM_BAD_INPUT -0x0014 /**< Bad input parameters to function. */
#ifdef __cplusplus
extern "C" {
#endif
#if !defined(MBEDTLS_GCM_ALT)
/**
* \brief The GCM context structure.
*/
typedef struct mbedtls_gcm_context
{
mbedtls_cipher_context_t cipher_ctx; /*!< The cipher context used. */
uint64_t HL[16]; /*!< Precalculated HTable low. */
uint64_t HH[16]; /*!< Precalculated HTable high. */
uint64_t len; /*!< The total length of the encrypted data. */
uint64_t add_len; /*!< The total length of the additional data. */
unsigned char base_ectr[16]; /*!< The first ECTR for tag. */
unsigned char y[16]; /*!< The Y working value. */
unsigned char buf[16]; /*!< The buf working value. */
int mode; /*!< The operation to perform:
#MBEDTLS_GCM_ENCRYPT or
#MBEDTLS_GCM_DECRYPT. */
}
mbedtls_gcm_context;
#else /* !MBEDTLS_GCM_ALT */
#include "gcm_alt.h"
#endif /* !MBEDTLS_GCM_ALT */
/**
* \brief This function initializes the specified GCM context,
* to make references valid, and prepares the context
* for mbedtls_gcm_setkey() or mbedtls_gcm_free().
*
* The function does not bind the GCM context to a particular
* cipher, nor set the key. For this purpose, use
* mbedtls_gcm_setkey().
*
* \param ctx The GCM context to initialize. This must not be \c NULL.
*/
void mbedtls_gcm_init( mbedtls_gcm_context *ctx );
/**
* \brief This function associates a GCM context with a
* cipher algorithm and a key.
*
* \param ctx The GCM context. This must be initialized.
* \param cipher The 128-bit block cipher to use.
* \param key The encryption key. This must be a readable buffer of at
* least \p keybits bits.
* \param keybits The key size in bits. Valid options are:
* <ul><li>128 bits</li>
* <li>192 bits</li>
* <li>256 bits</li></ul>
*
* \return \c 0 on success.
* \return A cipher-specific error code on failure.
*/
int mbedtls_gcm_setkey( mbedtls_gcm_context *ctx,
mbedtls_cipher_id_t cipher,
const unsigned char *key,
unsigned int keybits );
/**
* \brief This function performs GCM encryption or decryption of a buffer.
*
* \note For encryption, the output buffer can be the same as the
* input buffer. For decryption, the output buffer cannot be
* the same as input buffer. If the buffers overlap, the output
* buffer must trail at least 8 Bytes behind the input buffer.
*
* \warning When this function performs a decryption, it outputs the
* authentication tag and does not verify that the data is
* authentic. You should use this function to perform encryption
* only. For decryption, use mbedtls_gcm_auth_decrypt() instead.
*
* \param ctx The GCM context to use for encryption or decryption. This
* must be initialized.
* \param mode The operation to perform:
* - #MBEDTLS_GCM_ENCRYPT to perform authenticated encryption.
* The ciphertext is written to \p output and the
* authentication tag is written to \p tag.
* - #MBEDTLS_GCM_DECRYPT to perform decryption.
* The plaintext is written to \p output and the
* authentication tag is written to \p tag.
* Note that this mode is not recommended, because it does
* not verify the authenticity of the data. For this reason,
* you should use mbedtls_gcm_auth_decrypt() instead of
* calling this function in decryption mode.
* \param length The length of the input data, which is equal to the length
* of the output data.
* \param iv The initialization vector. This must be a readable buffer of
* at least \p iv_len Bytes.
* \param iv_len The length of the IV.
* \param add The buffer holding the additional data. This must be of at
* least that size in Bytes.
* \param add_len The length of the additional data.
* \param input The buffer holding the input data. If \p length is greater
* than zero, this must be a readable buffer of at least that
* size in Bytes.
* \param output The buffer for holding the output data. If \p length is greater
* than zero, this must be a writable buffer of at least that
* size in Bytes.
* \param tag_len The length of the tag to generate.
* \param tag The buffer for holding the tag. This must be a writable
* buffer of at least \p tag_len Bytes.
*
* \return \c 0 if the encryption or decryption was performed
* successfully. Note that in #MBEDTLS_GCM_DECRYPT mode,
* this does not indicate that the data is authentic.
* \return #MBEDTLS_ERR_GCM_BAD_INPUT if the lengths or pointers are
* not valid or a cipher-specific error code if the encryption
* or decryption failed.
*/
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 This function performs a GCM authenticated decryption of a
* buffer.
*
* \note For decryption, the output buffer cannot be the same as
* input buffer. If the buffers overlap, the output buffer
* must trail at least 8 Bytes behind the input buffer.
*
* \param ctx The GCM context. This must be initialized.
* \param length The length of the ciphertext to decrypt, which is also
* the length of the decrypted plaintext.
* \param iv The initialization vector. This must be a readable buffer
* of at least \p iv_len Bytes.
* \param iv_len The length of the IV.
* \param add The buffer holding the additional data. This must be of at
* least that size in Bytes.
* \param add_len The length of the additional data.
* \param tag The buffer holding the tag to verify. This must be a
* readable buffer of at least \p tag_len Bytes.
* \param tag_len The length of the tag to verify.
* \param input The buffer holding the ciphertext. If \p length is greater
* than zero, this must be a readable buffer of at least that
* size.
* \param output The buffer for holding the decrypted plaintext. If \p length
* is greater than zero, this must be a writable buffer of at
* least that size.
*
* \return \c 0 if successful and authenticated.
* \return #MBEDTLS_ERR_GCM_AUTH_FAILED if the tag does not match.
* \return #MBEDTLS_ERR_GCM_BAD_INPUT if the lengths or pointers are
* not valid or a cipher-specific error code if the decryption
* failed.
*/
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 This function starts a GCM encryption or decryption
* operation.
*
* \param ctx The GCM context. This must be initialized.
* \param mode The operation to perform: #MBEDTLS_GCM_ENCRYPT or
* #MBEDTLS_GCM_DECRYPT.
* \param iv The initialization vector. This must be a readable buffer of
* at least \p iv_len Bytes.
* \param iv_len The length of the IV.
* \param add The buffer holding the additional data, or \c NULL
* if \p add_len is \c 0.
* \param add_len The length of the additional data. If \c 0,
* \p add may be \c NULL.
*
* \return \c 0 on success.
*/
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 This function feeds an input buffer into an ongoing GCM
* encryption or decryption operation.
*
* ` The function expects input to be a multiple of 16
* Bytes. Only the last call before calling
* mbedtls_gcm_finish() can be less than 16 Bytes.
*
* \note For decryption, the output buffer cannot be the same as
* input buffer. If the buffers overlap, the output buffer
* must trail at least 8 Bytes behind the input buffer.
*
* \param ctx The GCM context. This must be initialized.
* \param length The length of the input data. This must be a multiple of
* 16 except in the last call before mbedtls_gcm_finish().
* \param input The buffer holding the input data. If \p length is greater
* than zero, this must be a readable buffer of at least that
* size in Bytes.
* \param output The buffer for holding the output data. If \p length is
* greater than zero, this must be a writable buffer of at
* least that size in Bytes.
*
* \return \c 0 on success.
* \return #MBEDTLS_ERR_GCM_BAD_INPUT on failure.
*/
int mbedtls_gcm_update( mbedtls_gcm_context *ctx,
size_t length,
const unsigned char *input,
unsigned char *output );
/**
* \brief This function finishes the GCM operation and generates
* the authentication tag.
*
* It wraps up the GCM stream, and generates the
* tag. The tag can have a maximum length of 16 Bytes.
*
* \param ctx The GCM context. This must be initialized.
* \param tag The buffer for holding the tag. This must be a writable
* buffer of at least \p tag_len Bytes.
* \param tag_len The length of the tag to generate. This must be at least
* four.
*
* \return \c 0 on success.
* \return #MBEDTLS_ERR_GCM_BAD_INPUT on failure.
*/
int mbedtls_gcm_finish( mbedtls_gcm_context *ctx,
unsigned char *tag,
size_t tag_len );
/**
* \brief This function clears a GCM context and the underlying
* cipher sub-context.
*
* \param ctx The GCM context to clear. If this is \c NULL, the call has
* no effect. Otherwise, this must be initialized.
*/
void mbedtls_gcm_free( mbedtls_gcm_context *ctx );
#if defined(MBEDTLS_SELF_TEST)
/**
* \brief The GCM checkup routine.
*
* \return \c 0 on success.
* \return \c 1 on failure.
*/
int mbedtls_gcm_self_test( int verbose );
#endif /* MBEDTLS_SELF_TEST */
#ifdef __cplusplus
}
#endif
#endif /* gcm.h */
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