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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 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            -0x0054
 /** Authenticated decryption failed: data was not authentic. */
 #define MBEDTLS_ERR_CHACHAPOLY_AUTH_FAILED          -0x0056
 
 #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 "mbedtls/chacha20.h"
 
 typedef struct mbedtls_chachapoly_context {
     mbedtls_chacha20_context MBEDTLS_PRIVATE(chacha20_ctx);  /**< The ChaCha20 context. */
     mbedtls_poly1305_context MBEDTLS_PRIVATE(poly1305_ctx);  /**< The Poly1305 context. */
     uint64_t MBEDTLS_PRIVATE(aad_len);                       /**< The length (bytes) of the Additional Authenticated Data. */
     uint64_t MBEDTLS_PRIVATE(ciphertext_len);                /**< The length (bytes) of the ciphertext. */
     int MBEDTLS_PRIVATE(state);                              /**< The current state of the context. */
     mbedtls_chachapoly_mode_t MBEDTLS_PRIVATE(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 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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