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* \file chachapoly.h
*
* \brief This file contains the AEAD-ChaCha20-Poly1305 definitions and
* functions.
*
* ChaCha20-Poly1305 is an algorithm for Authenticated Encryption
* with Associated Data (AEAD) that can be used to encrypt and
* authenticate data. It is based on ChaCha20 and Poly1305 by Daniel
* Bernstein and was standardized in RFC 7539.
*
* \author Daniel King <damaki.gh@gmail.com>
*/
/* Copyright (C) 2006-2018, Arm Limited (or its affiliates), 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_CHACHAPOLY_H
#define MBEDTLS_CHACHAPOLY_H
#if !defined(MBEDTLS_CONFIG_FILE)
#include "config.h"
#else
#include MBEDTLS_CONFIG_FILE
#endif
/* for shared error codes */
#include "poly1305.h"
#define MBEDTLS_ERR_CHACHAPOLY_BAD_STATE -0x0054 /**< The requested operation is not permitted in the current state. */
#define MBEDTLS_ERR_CHACHAPOLY_AUTH_FAILED -0x0056 /**< Authenticated decryption failed: data was not authentic. */
#ifdef __cplusplus
extern "C" {
#endif
typedef enum
{
MBEDTLS_CHACHAPOLY_ENCRYPT, /**< The mode value for performing encryption. */
MBEDTLS_CHACHAPOLY_DECRYPT /**< The mode value for performing decryption. */
}
mbedtls_chachapoly_mode_t;
#if !defined(MBEDTLS_CHACHAPOLY_ALT)
#include "chacha20.h"
typedef struct mbedtls_chachapoly_context
{
mbedtls_chacha20_context chacha20_ctx; /**< The ChaCha20 context. */
mbedtls_poly1305_context poly1305_ctx; /**< The Poly1305 context. */
uint64_t aad_len; /**< The length (bytes) of the Additional Authenticated Data. */
uint64_t ciphertext_len; /**< The length (bytes) of the ciphertext. */
int state; /**< The current state of the context. */
mbedtls_chachapoly_mode_t mode; /**< Cipher mode (encrypt or decrypt). */
}
mbedtls_chachapoly_context;
#else /* !MBEDTLS_CHACHAPOLY_ALT */
#include "chachapoly_alt.h"
#endif /* !MBEDTLS_CHACHAPOLY_ALT */
/**
* \brief This function initializes the specified ChaCha20-Poly1305 context.
*
* It must be the first API called before using
* the context. It must be followed by a call to
* \c mbedtls_chachapoly_setkey() before any operation can be
* done, and to \c mbedtls_chachapoly_free() once all
* operations with that context have been finished.
*
* In order to encrypt or decrypt full messages at once, for
* each message you should make a single call to
* \c mbedtls_chachapoly_crypt_and_tag() or
* \c mbedtls_chachapoly_auth_decrypt().
*
* In order to encrypt messages piecewise, for each
* message you should make a call to
* \c mbedtls_chachapoly_starts(), then 0 or more calls to
* \c mbedtls_chachapoly_update_aad(), then 0 or more calls to
* \c mbedtls_chachapoly_update(), then one call to
* \c mbedtls_chachapoly_finish().
*
* \warning Decryption with the piecewise API is discouraged! Always
* use \c mbedtls_chachapoly_auth_decrypt() when possible!
*
* If however this is not possible because the data is too
* large to fit in memory, you need to:
*
* - call \c mbedtls_chachapoly_starts() and (if needed)
* \c mbedtls_chachapoly_update_aad() as above,
* - call \c mbedtls_chachapoly_update() multiple times and
* ensure its output (the plaintext) is NOT used in any other
* way than placing it in temporary storage at this point,
* - call \c mbedtls_chachapoly_finish() to compute the
* authentication tag and compared it in constant time to the
* tag received with the ciphertext.
*
* If the tags are not equal, you must immediately discard
* all previous outputs of \c mbedtls_chachapoly_update(),
* otherwise you can now safely use the plaintext.
*
* \param ctx The ChachaPoly context to initialize. Must not be \c NULL.
*/
void mbedtls_chachapoly_init( mbedtls_chachapoly_context *ctx );
/**
* \brief This function releases and clears the specified
* ChaCha20-Poly1305 context.
*
* \param ctx The ChachaPoly context to clear. This may be \c NULL, in which
* case this function is a no-op.
*/
void mbedtls_chachapoly_free( mbedtls_chachapoly_context *ctx );
/**
* \brief This function sets the ChaCha20-Poly1305
* symmetric encryption key.
*
* \param ctx The ChaCha20-Poly1305 context to which the key should be
* bound. This must be initialized.
* \param key The \c 256 Bit (\c 32 Bytes) key.
*
* \return \c 0 on success.
* \return A negative error code on failure.
*/
int mbedtls_chachapoly_setkey( mbedtls_chachapoly_context *ctx,
const unsigned char key[32] );
/**
* \brief This function starts a ChaCha20-Poly1305 encryption or
* decryption operation.
*
* \warning You must never use the same nonce twice with the same key.
* This would void any confidentiality and authenticity
* guarantees for the messages encrypted with the same nonce
* and key.
*
* \note If the context is being used for AAD only (no data to
* encrypt or decrypt) then \p mode can be set to any value.
*
* \warning Decryption with the piecewise API is discouraged, see the
* warning on \c mbedtls_chachapoly_init().
*
* \param ctx The ChaCha20-Poly1305 context. This must be initialized
* and bound to a key.
* \param nonce The nonce/IV to use for the message.
* This must be a redable buffer of length \c 12 Bytes.
* \param mode The operation to perform: #MBEDTLS_CHACHAPOLY_ENCRYPT or
* #MBEDTLS_CHACHAPOLY_DECRYPT (discouraged, see warning).
*
* \return \c 0 on success.
* \return A negative error code on failure.
*/
int mbedtls_chachapoly_starts( mbedtls_chachapoly_context *ctx,
const unsigned char nonce[12],
mbedtls_chachapoly_mode_t mode );
/**
* \brief This function feeds additional data to be authenticated
* into an ongoing ChaCha20-Poly1305 operation.
*
* The Additional Authenticated Data (AAD), also called
* Associated Data (AD) is only authenticated but not
* encrypted nor included in the encrypted output. It is
* usually transmitted separately from the ciphertext or
* computed locally by each party.
*
* \note This function is called before data is encrypted/decrypted.
* I.e. call this function to process the AAD before calling
* \c mbedtls_chachapoly_update().
*
* You may call this function multiple times to process
* an arbitrary amount of AAD. It is permitted to call
* this function 0 times, if no AAD is used.
*
* This function cannot be called any more if data has
* been processed by \c mbedtls_chachapoly_update(),
* or if the context has been finished.
*
* \warning Decryption with the piecewise API is discouraged, see the
* warning on \c mbedtls_chachapoly_init().
*
* \param ctx The ChaCha20-Poly1305 context. This must be initialized
* and bound to a key.
* \param aad_len The length in Bytes of the AAD. The length has no
* restrictions.
* \param aad Buffer containing the AAD.
* This pointer can be \c NULL if `aad_len == 0`.
*
* \return \c 0 on success.
* \return #MBEDTLS_ERR_POLY1305_BAD_INPUT_DATA
* if \p ctx or \p aad are NULL.
* \return #MBEDTLS_ERR_CHACHAPOLY_BAD_STATE
* if the operations has not been started or has been
* finished, or if the AAD has been finished.
*/
int mbedtls_chachapoly_update_aad( mbedtls_chachapoly_context *ctx,
const unsigned char *aad,
size_t aad_len );
/**
* \brief Thus function feeds data to be encrypted or decrypted
* into an on-going ChaCha20-Poly1305
* operation.
*
* The direction (encryption or decryption) depends on the
* mode that was given when calling
* \c mbedtls_chachapoly_starts().
*
* You may call this function multiple times to process
* an arbitrary amount of data. It is permitted to call
* this function 0 times, if no data is to be encrypted
* or decrypted.
*
* \warning Decryption with the piecewise API is discouraged, see the
* warning on \c mbedtls_chachapoly_init().
*
* \param ctx The ChaCha20-Poly1305 context to use. This must be initialized.
* \param len The length (in bytes) of the data to encrypt or decrypt.
* \param input The buffer containing the data to encrypt or decrypt.
* This pointer can be \c NULL if `len == 0`.
* \param output The buffer to where the encrypted or decrypted data is
* written. This must be able to hold \p len bytes.
* This pointer can be \c NULL if `len == 0`.
*
* \return \c 0 on success.
* \return #MBEDTLS_ERR_CHACHAPOLY_BAD_STATE
* if the operation has not been started or has been
* finished.
* \return Another negative error code on other kinds of failure.
*/
int mbedtls_chachapoly_update( mbedtls_chachapoly_context *ctx,
size_t len,
const unsigned char *input,
unsigned char *output );
/**
* \brief This function finished the ChaCha20-Poly1305 operation and
* generates the MAC (authentication tag).
*
* \param ctx The ChaCha20-Poly1305 context to use. This must be initialized.
* \param mac The buffer to where the 128-bit (16 bytes) MAC is written.
*
* \warning Decryption with the piecewise API is discouraged, see the
* warning on \c mbedtls_chachapoly_init().
*
* \return \c 0 on success.
* \return #MBEDTLS_ERR_CHACHAPOLY_BAD_STATE
* if the operation has not been started or has been
* finished.
* \return Another negative error code on other kinds of failure.
*/
int mbedtls_chachapoly_finish( mbedtls_chachapoly_context *ctx,
unsigned char mac[16] );
/**
* \brief This function performs a complete ChaCha20-Poly1305
* authenticated encryption with the previously-set key.
*
* \note Before using this function, you must set the key with
* \c mbedtls_chachapoly_setkey().
*
* \warning You must never use the same nonce twice with the same key.
* This would void any confidentiality and authenticity
* guarantees for the messages encrypted with the same nonce
* and key.
*
* \param ctx The ChaCha20-Poly1305 context to use (holds the key).
* This must be initialized.
* \param length The length (in bytes) of the data to encrypt or decrypt.
* \param nonce The 96-bit (12 bytes) nonce/IV to use.
* \param aad The buffer containing the additional authenticated
* data (AAD). This pointer can be \c NULL if `aad_len == 0`.
* \param aad_len The length (in bytes) of the AAD data to process.
* \param input The buffer containing the data to encrypt or decrypt.
* This pointer can be \c NULL if `ilen == 0`.
* \param output The buffer to where the encrypted or decrypted data
* is written. This pointer can be \c NULL if `ilen == 0`.
* \param tag The buffer to where the computed 128-bit (16 bytes) MAC
* is written. This must not be \c NULL.
*
* \return \c 0 on success.
* \return A negative error code on failure.
*/
int mbedtls_chachapoly_encrypt_and_tag( mbedtls_chachapoly_context *ctx,
size_t length,
const unsigned char nonce[12],
const unsigned char *aad,
size_t aad_len,
const unsigned char *input,
unsigned char *output,
unsigned char tag[16] );
/**
* \brief This function performs a complete ChaCha20-Poly1305
* authenticated decryption with the previously-set key.
*
* \note Before using this function, you must set the key with
* \c mbedtls_chachapoly_setkey().
*
* \param ctx The ChaCha20-Poly1305 context to use (holds the key).
* \param length The length (in Bytes) of the data to decrypt.
* \param nonce The \c 96 Bit (\c 12 bytes) nonce/IV to use.
* \param aad The buffer containing the additional authenticated data (AAD).
* This pointer can be \c NULL if `aad_len == 0`.
* \param aad_len The length (in bytes) of the AAD data to process.
* \param tag The buffer holding the authentication tag.
* This must be a readable buffer of length \c 16 Bytes.
* \param input The buffer containing the data to decrypt.
* This pointer can be \c NULL if `ilen == 0`.
* \param output The buffer to where the decrypted data is written.
* This pointer can be \c NULL if `ilen == 0`.
*
* \return \c 0 on success.
* \return #MBEDTLS_ERR_CHACHAPOLY_AUTH_FAILED
* if the data was not authentic.
* \return Another negative error code on other kinds of failure.
*/
int mbedtls_chachapoly_auth_decrypt( mbedtls_chachapoly_context *ctx,
size_t length,
const unsigned char nonce[12],
const unsigned char *aad,
size_t aad_len,
const unsigned char tag[16],
const unsigned char *input,
unsigned char *output );
#if defined(MBEDTLS_SELF_TEST)
/**
* \brief The ChaCha20-Poly1305 checkup routine.
*
* \return \c 0 on success.
* \return \c 1 on failure.
*/
int mbedtls_chachapoly_self_test( int verbose );
#endif /* MBEDTLS_SELF_TEST */
#ifdef __cplusplus
}
#endif
#endif /* MBEDTLS_CHACHAPOLY_H */
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