/** * \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 <[email protected]> */ /* * Copyright The Mbed TLS Contributors * SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later */ #ifndef MBEDTLS_CHACHAPOLY_H #define MBEDTLS_CHACHAPOLY_H #include "mbedtls/private_access.h" #include "mbedtls/build_info.h" /* for shared error codes */ #include "mbedtls/poly1305.h" /** The requested operation is not permitted in the current state. */ #define MBEDTLS_ERR_CHACHAPOLY_BAD_STATE … /** Authenticated decryption failed: data was not authentic. */ #define MBEDTLS_ERR_CHACHAPOLY_AUTH_FAILED … #ifdef __cplusplus extern "C" { #endif mbedtls_chachapoly_mode_t; #if !defined(MBEDTLS_CHACHAPOLY_ALT) #include "mbedtls/chacha20.h" 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 readable 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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