text: /**
   * \file cipher.h
   *
   * \brief Generic cipher wrapper.
   *
   * \author Adriaan de Jong <dejong@fox-it.com>
   *
   *  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)
   *
   *
   *  Modifications copyright (C) 2018 Benjamin Weigl <r0ot@online.de>
   */
  
  #ifndef MBEDTLS_CIPHER_H
  #define MBEDTLS_CIPHER_H
  
  #if !defined(MBEDTLS_CONFIG_FILE)
  #include "config.h"
  #else
  #include MBEDTLS_CONFIG_FILE
  #endif
  
  #include <stddef.h>
  
  #if defined(MBEDTLS_GCM_C) || defined(MBEDTLS_CCM_C) \
    || defined(MBEDTLS_AEGIS_C)
  #define MBEDTLS_CIPHER_MODE_AEAD
  #endif
  
  #if defined(MBEDTLS_CIPHER_MODE_CBC) || defined(MBEDTLS_AEGIS_C)
  #define MBEDTLS_CIPHER_MODE_WITH_PADDING
  #endif
  
  #if defined(MBEDTLS_ARC4_C)
  #define MBEDTLS_CIPHER_MODE_STREAM
  #endif
  
  #if ( defined(__ARMCC_VERSION) || defined(_MSC_VER) ) && \
      !defined(inline) && !defined(__cplusplus)
  #define inline __inline
  #endif
  
  #define MBEDTLS_ERR_CIPHER_FEATURE_UNAVAILABLE            -0x6080  /**< The selected feature is not available. */
  #define MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA                 -0x6100  /**< Bad input parameters to function. */
  #define MBEDTLS_ERR_CIPHER_ALLOC_FAILED                   -0x6180  /**< Failed to allocate memory. */
  #define MBEDTLS_ERR_CIPHER_INVALID_PADDING                -0x6200  /**< Input data contains invalid padding and is rejected. */
  #define MBEDTLS_ERR_CIPHER_FULL_BLOCK_EXPECTED            -0x6280  /**< Decryption of block requires a full block. */
  #define MBEDTLS_ERR_CIPHER_AUTH_FAILED                    -0x6300  /**< Authentication failed (for AEAD modes). */
  #define MBEDTLS_ERR_CIPHER_INVALID_CONTEXT              -0x6380  /**< The context is invalid, eg because it was free()ed. */
  
  #define MBEDTLS_CIPHER_VARIABLE_IV_LEN     0x01    /**< Cipher accepts IVs of variable length */
  #define MBEDTLS_CIPHER_VARIABLE_KEY_LEN    0x02    /**< Cipher accepts keys of variable length */
  
  #ifdef __cplusplus
  extern "C" {
  #endif
  
  typedef enum {
      MBEDTLS_CIPHER_ID_NONE = 0,
      MBEDTLS_CIPHER_ID_NULL,
      MBEDTLS_CIPHER_ID_AES,
      MBEDTLS_CIPHER_ID_AEGIS,
      MBEDTLS_CIPHER_ID_DES,
      MBEDTLS_CIPHER_ID_3DES,
      MBEDTLS_CIPHER_ID_CAMELLIA,
      MBEDTLS_CIPHER_ID_BLOWFISH,
      MBEDTLS_CIPHER_ID_ARC4,
  } mbedtls_cipher_id_t;
  
  typedef enum {
      MBEDTLS_CIPHER_NONE = 0,
      MBEDTLS_CIPHER_NULL,
      MBEDTLS_CIPHER_AES_128_ECB,
      MBEDTLS_CIPHER_AES_192_ECB,
      MBEDTLS_CIPHER_AES_256_ECB,
      MBEDTLS_CIPHER_AES_128_CBC,
      MBEDTLS_CIPHER_AES_192_CBC,
      MBEDTLS_CIPHER_AES_256_CBC,
      MBEDTLS_CIPHER_AES_128_CFB128,
      MBEDTLS_CIPHER_AES_192_CFB128,
      MBEDTLS_CIPHER_AES_256_CFB128,
      MBEDTLS_CIPHER_AES_128_CTR,
      MBEDTLS_CIPHER_AES_192_CTR,
      MBEDTLS_CIPHER_AES_256_CTR,
      MBEDTLS_CIPHER_AES_128_GCM,
      MBEDTLS_CIPHER_AES_192_GCM,
      MBEDTLS_CIPHER_AES_256_GCM,
      MBEDTLS_CIPHER_AEGIS_128_L,
      MBEDTLS_CIPHER_CAMELLIA_128_ECB,
      MBEDTLS_CIPHER_CAMELLIA_192_ECB,
      MBEDTLS_CIPHER_CAMELLIA_256_ECB,
      MBEDTLS_CIPHER_CAMELLIA_128_CBC,
      MBEDTLS_CIPHER_CAMELLIA_192_CBC,
      MBEDTLS_CIPHER_CAMELLIA_256_CBC,
      MBEDTLS_CIPHER_CAMELLIA_128_CFB128,
      MBEDTLS_CIPHER_CAMELLIA_192_CFB128,
      MBEDTLS_CIPHER_CAMELLIA_256_CFB128,
      MBEDTLS_CIPHER_CAMELLIA_128_CTR,
      MBEDTLS_CIPHER_CAMELLIA_192_CTR,
      MBEDTLS_CIPHER_CAMELLIA_256_CTR,
      MBEDTLS_CIPHER_CAMELLIA_128_GCM,
      MBEDTLS_CIPHER_CAMELLIA_192_GCM,
      MBEDTLS_CIPHER_CAMELLIA_256_GCM,
      MBEDTLS_CIPHER_DES_ECB,
      MBEDTLS_CIPHER_DES_CBC,
      MBEDTLS_CIPHER_DES_EDE_ECB,
      MBEDTLS_CIPHER_DES_EDE_CBC,
      MBEDTLS_CIPHER_DES_EDE3_ECB,
      MBEDTLS_CIPHER_DES_EDE3_CBC,
      MBEDTLS_CIPHER_BLOWFISH_ECB,
      MBEDTLS_CIPHER_BLOWFISH_CBC,
      MBEDTLS_CIPHER_BLOWFISH_CFB64,
      MBEDTLS_CIPHER_BLOWFISH_CTR,
      MBEDTLS_CIPHER_ARC4_128,
      MBEDTLS_CIPHER_AES_128_CCM,
      MBEDTLS_CIPHER_AES_192_CCM,
      MBEDTLS_CIPHER_AES_256_CCM,
      MBEDTLS_CIPHER_CAMELLIA_128_CCM,
      MBEDTLS_CIPHER_CAMELLIA_192_CCM,
      MBEDTLS_CIPHER_CAMELLIA_256_CCM,
  } mbedtls_cipher_type_t;
  
  typedef enum {
      MBEDTLS_MODE_NONE = 0,
      MBEDTLS_MODE_ECB,
      MBEDTLS_MODE_CBC,
      MBEDTLS_MODE_CFB,
      MBEDTLS_MODE_OFB, /* Unused! */
      MBEDTLS_MODE_CTR,
      MBEDTLS_MODE_GCM,
      MBEDTLS_MODE_AEAD,
      MBEDTLS_MODE_STREAM,
      MBEDTLS_MODE_CCM,
  } mbedtls_cipher_mode_t;
  
  typedef enum {
      MBEDTLS_PADDING_PKCS7 = 0,     /**< PKCS7 padding (default)        */
      MBEDTLS_PADDING_ONE_AND_ZEROS, /**< ISO/IEC 7816-4 padding         */
      MBEDTLS_PADDING_ZEROS_AND_LEN, /**< ANSI X.923 padding             */
      MBEDTLS_PADDING_ZEROS,         /**< zero padding (not reversible!) */
      MBEDTLS_PADDING_NONE,          /**< never pad (full blocks only)   */
  } mbedtls_cipher_padding_t;
  
  typedef enum {
      MBEDTLS_OPERATION_NONE = -1,
      MBEDTLS_DECRYPT = 0,
      MBEDTLS_ENCRYPT,
  } mbedtls_operation_t;
  
  enum {
      /** Undefined key length */
      MBEDTLS_KEY_LENGTH_NONE = 0,
      /** Key length, in bits (including parity), for DES keys */
      MBEDTLS_KEY_LENGTH_DES  = 64,
      /** Key length, in bits (including parity), for DES in two key EDE */
      MBEDTLS_KEY_LENGTH_DES_EDE = 128,
      /** Key length, in bits (including parity), for DES in three-key EDE */
      MBEDTLS_KEY_LENGTH_DES_EDE3 = 192,
  };
  
  /** Maximum length of any IV, in bytes */
  #define MBEDTLS_MAX_IV_LENGTH      16
  /** Maximum block size of any cipher, in bytes */
  #define MBEDTLS_MAX_BLOCK_LENGTH   32
  
  /**
   * Base cipher information (opaque struct).
   */
  typedef struct mbedtls_cipher_base_t mbedtls_cipher_base_t;
  
  /**
   * CMAC context (opaque struct).
   */
  typedef struct mbedtls_cmac_context_t mbedtls_cmac_context_t;
  
  /**
   * Cipher information. Allows cipher functions to be called in a generic way.
   */
  typedef struct {
      /** Full cipher identifier (e.g. MBEDTLS_CIPHER_AES_256_CBC) */
      mbedtls_cipher_type_t type;
  
      /** Cipher mode (e.g. MBEDTLS_MODE_CBC) */
      mbedtls_cipher_mode_t mode;
  
      /** Cipher key length, in bits (default length for variable sized ciphers)
       *  (Includes parity bits for ciphers like DES) */
      unsigned int key_bitlen;
  
      /** Name of the cipher */
      const char * name;
  
      /** IV/NONCE size, in bytes.
       *  For cipher that accept many sizes: recommended size */
      unsigned int iv_size;
  
      /** Flags for variable IV size, variable key size, etc. */
      int flags;
  
      /** block size, in bytes */
      unsigned int block_size;
  
      /** Base cipher information and functions */
      const mbedtls_cipher_base_t *base;
  
  } mbedtls_cipher_info_t;
  
  /**
   * Generic cipher context.
   */
  typedef struct {
      /** Information about the associated cipher */
      const mbedtls_cipher_info_t *cipher_info;
  
      /** Key length to use */
      int key_bitlen;
  
      /** Operation that the context's key has been initialised for */
      mbedtls_operation_t operation;
  
  #if defined(MBEDTLS_CIPHER_MODE_WITH_PADDING)
      /** Padding functions to use, if relevant for cipher mode */
      void (*add_padding)( unsigned char *output, size_t olen, size_t data_len );
      int (*get_padding)( unsigned char *input, size_t ilen, size_t *data_len );
  #endif
  
      /** Buffer for data that hasn't been encrypted yet */
      unsigned char unprocessed_data[MBEDTLS_MAX_BLOCK_LENGTH];
  
      /** Number of bytes that still need processing */
      size_t unprocessed_len;
  
      /** Current IV or NONCE_COUNTER for CTR-mode */
      unsigned char iv[MBEDTLS_MAX_IV_LENGTH];
  
      /** IV size in bytes (for ciphers with variable-length IVs) */
      size_t iv_size;
  
      /** Cipher-specific context */
      void *cipher_ctx;
  
  #if defined(MBEDTLS_CMAC_C)
      /** CMAC Specific context */
      mbedtls_cmac_context_t *cmac_ctx;
  #endif
  } mbedtls_cipher_context_t;
  
  /**
   * \brief Returns the list of ciphers supported by the generic cipher module.
   *
   * \return              a statically allocated array of ciphers, the last entry
   *                      is 0.
   */
  const int *mbedtls_cipher_list( void );
  
  /**
   * \brief               Returns the cipher information structure associated
   *                      with the given cipher name.
   *
   * \param cipher_name   Name of the cipher to search for.
   *
   * \return              the cipher information structure associated with the
   *                      given cipher_name, or NULL if not found.
   */
  const mbedtls_cipher_info_t *mbedtls_cipher_info_from_string( const char *cipher_name );
  
  /**
   * \brief               Returns the cipher information structure associated
   *                      with the given cipher type.
   *
   * \param cipher_type   Type of the cipher to search for.
   *
   * \return              the cipher information structure associated with the
   *                      given cipher_type, or NULL if not found.
   */
  const mbedtls_cipher_info_t *mbedtls_cipher_info_from_type( const mbedtls_cipher_type_t cipher_type );
  
  /**
   * \brief               Returns the cipher information structure associated
   *                      with the given cipher id, key size and mode.
   *
   * \param cipher_id     Id of the cipher to search for
   *                      (e.g. MBEDTLS_CIPHER_ID_AES)
   * \param key_bitlen    Length of the key in bits
   * \param mode          Cipher mode (e.g. MBEDTLS_MODE_CBC)
   *
   * \return              the cipher information structure associated with the
   *                      given cipher_type, or NULL if not found.
   */
  const mbedtls_cipher_info_t *mbedtls_cipher_info_from_values( const mbedtls_cipher_id_t cipher_id,
                                                int key_bitlen,
                                                const mbedtls_cipher_mode_t mode );
  
  /**
   * \brief               Initialize a cipher_context (as NONE)
   */
  void mbedtls_cipher_init( mbedtls_cipher_context_t *ctx );
  
  /**
   * \brief               Free and clear the cipher-specific context of ctx.
   *                      Freeing ctx itself remains the responsibility of the
   *                      caller.
   */
  void mbedtls_cipher_free( mbedtls_cipher_context_t *ctx );
  
  /**
   * \brief               Initialises and fills the cipher context structure with
   *                      the appropriate values.
   *
   * \note                Currently also clears structure. In future versions you
   *                      will be required to call mbedtls_cipher_init() on the structure
   *                      first.
   *
   * \param ctx           context to initialise. May not be NULL.
   * \param cipher_info   cipher to use.
   *
   * \return              0 on success,
   *                      MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA on parameter failure,
   *                      MBEDTLS_ERR_CIPHER_ALLOC_FAILED if allocation of the
   *                      cipher-specific context failed.
   */
  int mbedtls_cipher_setup( mbedtls_cipher_context_t *ctx, const mbedtls_cipher_info_t *cipher_info );
  
  /**
   * \brief               Returns the block size of the given cipher.
   *
   * \param ctx           cipher's context. Must have been initialised.
   *
   * \return              size of the cipher's blocks, or 0 if ctx has not been
   *                      initialised.
   */
  static inline unsigned int mbedtls_cipher_get_block_size( const mbedtls_cipher_context_t *ctx )
  {
      if( NULL == ctx || NULL == ctx->cipher_info )
          return 0;
  
      return ctx->cipher_info->block_size;
  }
  
  /**
   * \brief               Returns the mode of operation for the cipher.
   *                      (e.g. MBEDTLS_MODE_CBC)
   *
   * \param ctx           cipher's context. Must have been initialised.
   *
   * \return              mode of operation, or MBEDTLS_MODE_NONE if ctx
   *                      has not been initialised.
   */
  static inline mbedtls_cipher_mode_t mbedtls_cipher_get_cipher_mode( const mbedtls_cipher_context_t *ctx )
  {
      if( NULL == ctx || NULL == ctx->cipher_info )
          return MBEDTLS_MODE_NONE;
  
      return ctx->cipher_info->mode;
  }
  
  /**
   * \brief               Returns the size of the cipher's IV/NONCE in bytes.
   *
   * \param ctx           cipher's context. Must have been initialised.
   *
   * \return              If IV has not been set yet: (recommended) IV size
   *                      (0 for ciphers not using IV/NONCE).
   *                      If IV has already been set: actual size.
   */
  static inline int mbedtls_cipher_get_iv_size( const mbedtls_cipher_context_t *ctx )
  {
      if( NULL == ctx || NULL == ctx->cipher_info )
          return 0;
  
      if( ctx->iv_size != 0 )
          return (int) ctx->iv_size;
  
      return (int) ctx->cipher_info->iv_size;
  }
  
  /**
   * \brief               Returns the type of the given cipher.
   *
   * \param ctx           cipher's context. Must have been initialised.
   *
   * \return              type of the cipher, or MBEDTLS_CIPHER_NONE if ctx has
   *                      not been initialised.
   */
  static inline mbedtls_cipher_type_t mbedtls_cipher_get_type( const mbedtls_cipher_context_t *ctx )
  {
      if( NULL == ctx || NULL == ctx->cipher_info )
          return MBEDTLS_CIPHER_NONE;
  
      return ctx->cipher_info->type;
  }
  
  /**
   * \brief               Returns the name of the given cipher, as a string.
   *
   * \param ctx           cipher's context. Must have been initialised.
   *
   * \return              name of the cipher, or NULL if ctx was not initialised.
   */
  static inline const char *mbedtls_cipher_get_name( const mbedtls_cipher_context_t *ctx )
  {
      if( NULL == ctx || NULL == ctx->cipher_info )
          return 0;
  
      return ctx->cipher_info->name;
  }
  
  /**
   * \brief               Returns the key length of the cipher.
   *
   * \param ctx           cipher's context. Must have been initialised.
   *
   * \return              cipher's key length, in bits, or
   *                      MBEDTLS_KEY_LENGTH_NONE if ctx has not been
   *                      initialised.
   */
  static inline int mbedtls_cipher_get_key_bitlen( const mbedtls_cipher_context_t *ctx )
  {
      if( NULL == ctx || NULL == ctx->cipher_info )
          return MBEDTLS_KEY_LENGTH_NONE;
  
      return (int) ctx->cipher_info->key_bitlen;
  }
  
  /**
   * \brief               Returns the operation of the given cipher.
   *
   * \param ctx           cipher's context. Must have been initialised.
   *
   * \return              operation (MBEDTLS_ENCRYPT or MBEDTLS_DECRYPT),
   *                      or MBEDTLS_OPERATION_NONE if ctx has not been
   *                      initialised.
   */
  static inline mbedtls_operation_t mbedtls_cipher_get_operation( const mbedtls_cipher_context_t *ctx )
  {
      if( NULL == ctx || NULL == ctx->cipher_info )
          return MBEDTLS_OPERATION_NONE;
  
      return ctx->operation;
  }
  
  /**
   * \brief               Set the key to use with the given context.
   *
   * \param ctx           generic cipher context. May not be NULL. Must have been
   *                      initialised using cipher_context_from_type or
   *                      cipher_context_from_string.
   * \param key           The key to use.
   * \param key_bitlen    key length to use, in bits.
   * \param operation     Operation that the key will be used for, either
   *                      MBEDTLS_ENCRYPT or MBEDTLS_DECRYPT.
   *
   * \returns             0 on success, MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA if
   *                      parameter verification fails or a cipher specific
   *                      error code.
   */
  int mbedtls_cipher_setkey( mbedtls_cipher_context_t *ctx, const unsigned char *key,
                     int key_bitlen, const mbedtls_operation_t operation );
  
  #if defined(MBEDTLS_CIPHER_MODE_WITH_PADDING)
  /**
   * \brief               Set padding mode, for cipher modes that use padding.
   *                      (Default: PKCS7 padding.)
   *
   * \param ctx           generic cipher context
   * \param mode          padding mode
   *
   * \returns             0 on success, MBEDTLS_ERR_CIPHER_FEATURE_UNAVAILABLE
   *                      if selected padding mode is not supported, or
   *                      MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA if the cipher mode
   *                      does not support padding.
   */
  int mbedtls_cipher_set_padding_mode( mbedtls_cipher_context_t *ctx, mbedtls_cipher_padding_t mode );
  #endif /* MBEDTLS_CIPHER_MODE_WITH_PADDING */
  
  /**
   * \brief               Set the initialization vector (IV) or nonce
   *
   * \param ctx           generic cipher context
   * \param iv            IV to use (or NONCE_COUNTER for CTR-mode ciphers)
   * \param iv_len        IV length for ciphers with variable-size IV;
   *                      discarded by ciphers with fixed-size IV.
   *
   * \returns             0 on success, or MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA
   *
   * \note                Some ciphers don't use IVs nor NONCE. For these
   *                      ciphers, this function has no effect.
   */
  int mbedtls_cipher_set_iv( mbedtls_cipher_context_t *ctx,
                     const unsigned char *iv, size_t iv_len );
  
  /**
   * \brief               Finish preparation of the given context
   *
   * \param ctx           generic cipher context
   *
   * \returns             0 on success, MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA
   *                      if parameter verification fails.
   */
  int mbedtls_cipher_reset( mbedtls_cipher_context_t *ctx );
  
  #if defined(MBEDTLS_GCM_C) || defined(MBEDTLS_AEGIS_C)
  /**
   * \brief               Add additional data (for AEAD ciphers).
   *                      Currently only supported with GCM and AEGIS.
   *                      Must be called exactly once, after mbedtls_cipher_reset().
   *
   * \param ctx           generic cipher context
   * \param ad            Additional data to use.
   * \param ad_len        Length of ad.
   *
   * \return              0 on success, or a specific error code.
   */
  int mbedtls_cipher_update_ad( mbedtls_cipher_context_t *ctx,
                        const unsigned char *ad, size_t ad_len );
  #endif /* MBEDTLS_GCM_C */
  
  /**
   * \brief               Generic cipher update function. Encrypts/decrypts
   *                      using the given cipher context. Writes as many block
   *                      size'd blocks of data as possible to output. Any data
   *                      that cannot be written immediately will either be added
   *                      to the next block, or flushed when cipher_final is
   *                      called.
   *                      Exception: for MBEDTLS_MODE_ECB, expects single block
   *                                 in size (e.g. 16 bytes for AES)
   *
   * \param ctx           generic cipher context
   * \param input         buffer holding the input data
   * \param ilen          length of the input data
   * \param output        buffer for the output data. Should be able to hold at
   *                      least ilen + block_size. Cannot be the same buffer as
   *                      input!
   * \param olen          length of the output data, will be filled with the
   *                      actual number of bytes written.
   *
   * \returns             0 on success, MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA if
   *                      parameter verification fails,
   *                      MBEDTLS_ERR_CIPHER_FEATURE_UNAVAILABLE on an
   *                      unsupported mode for a cipher or a cipher specific
   *                      error code.
   *
   * \note                If the underlying cipher is GCM, all calls to this
   *                      function, except the last one before mbedtls_cipher_finish(),
   *                      must have ilen a multiple of the block size.
   */
  int mbedtls_cipher_update( mbedtls_cipher_context_t *ctx, const unsigned char *input,
                     size_t ilen, unsigned char *output, size_t *olen );
  
  /**
   * \brief               Generic cipher finalisation function. If data still
   *                      needs to be flushed from an incomplete block, data
   *                      contained within it will be padded with the size of
   *                      the last block, and written to the output buffer.
   *
   * \param ctx           Generic cipher context
   * \param output        buffer to write data to. Needs block_size available.
   * \param olen          length of the data written to the output buffer.
   *
   * \returns             0 on success, MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA if
   *                      parameter verification fails,
   *                      MBEDTLS_ERR_CIPHER_FULL_BLOCK_EXPECTED if decryption
   *                      expected a full block but was not provided one,
   *                      MBEDTLS_ERR_CIPHER_INVALID_PADDING on invalid padding
   *                      while decrypting or a cipher specific error code.
   */
  int mbedtls_cipher_finish( mbedtls_cipher_context_t *ctx,
                     unsigned char *output, size_t *olen );
  
  #if defined(MBEDTLS_GCM_C) || defined(MBEDTLS_AEGIS_C)
  /**
   * \brief               Write tag for AEAD ciphers.
   *                      Currently only supported with GCM.
   *                      Must be called after mbedtls_cipher_finish().
   *
   * \param ctx           Generic cipher context
   * \param tag           buffer to write the tag
   * \param tag_len       Length of the tag to write
   *
   * \return              0 on success, or a specific error code.
   */
  int mbedtls_cipher_write_tag( mbedtls_cipher_context_t *ctx,
                        unsigned char *tag, size_t tag_len );
  
  /**
   * \brief               Check tag for AEAD ciphers.
   *                      Currently only supported with GCM.
   *                      Must be called after mbedtls_cipher_finish().
   *
   * \param ctx           Generic cipher context
   * \param tag           Buffer holding the tag
   * \param tag_len       Length of the tag to check
   *
   * \return              0 on success, or a specific error code.
   */
  int mbedtls_cipher_check_tag( mbedtls_cipher_context_t *ctx,
                        const unsigned char *tag, size_t tag_len );
  #endif /* MBEDTLS_GCM_C */
  
  /**
   * \brief               Generic all-in-one encryption/decryption
   *                      (for all ciphers except AEAD constructs).
   *
   * \param ctx           generic cipher context
   * \param iv            IV to use (or NONCE_COUNTER for CTR-mode ciphers)
   * \param iv_len        IV length for ciphers with variable-size IV;
   *                      discarded by ciphers with fixed-size IV.
   * \param input         buffer holding the input data
   * \param ilen          length of the input data
   * \param output        buffer for the output data. Should be able to hold at
   *                      least ilen + block_size. Cannot be the same buffer as
   *                      input!
   * \param olen          length of the output data, will be filled with the
   *                      actual number of bytes written.
   *
   * \note                Some ciphers don't use IVs nor NONCE. For these
   *                      ciphers, use iv = NULL and iv_len = 0.
   *
   * \returns             0 on success, or
   *                      MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA, or
   *                      MBEDTLS_ERR_CIPHER_FULL_BLOCK_EXPECTED if decryption
   *                      expected a full block but was not provided one, or
   *                      MBEDTLS_ERR_CIPHER_INVALID_PADDING on invalid padding
   *                      while decrypting, or
   *                      a cipher specific error code.
   */
  int mbedtls_cipher_crypt( mbedtls_cipher_context_t *ctx,
                    const unsigned char *iv, size_t iv_len,
                    const unsigned char *input, size_t ilen,
                    unsigned char *output, size_t *olen );
  
  #if defined(MBEDTLS_CIPHER_MODE_AEAD)
  /**
   * \brief               Generic autenticated encryption (AEAD ciphers).
   *
   * \param ctx           generic cipher context
   * \param iv            IV to use (or NONCE_COUNTER for CTR-mode ciphers)
   * \param iv_len        IV length for ciphers with variable-size IV;
   *                      discarded by ciphers with fixed-size IV.
   * \param ad            Additional data to authenticate.
   * \param ad_len        Length of ad.
   * \param input         buffer holding the input data
   * \param ilen          length of the input data
   * \param output        buffer for the output data.
   *                      Should be able to hold at least ilen.
   * \param olen          length of the output data, will be filled with the
   *                      actual number of bytes written.
   * \param tag           buffer for the authentication tag
   * \param tag_len       desired tag length
   *
   * \returns             0 on success, or
   *                      MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA, or
   *                      a cipher specific error code.
   */
  int mbedtls_cipher_auth_encrypt( mbedtls_cipher_context_t *ctx,
                           const unsigned char *iv, size_t iv_len,
                           const unsigned char *ad, size_t ad_len,
                           const unsigned char *input, size_t ilen,
                           unsigned char *output, size_t *olen,
                           unsigned char *tag, size_t tag_len );
  
  /**
   * \brief               Generic autenticated decryption (AEAD ciphers).
   *
   * \param ctx           generic cipher context
   * \param iv            IV to use (or NONCE_COUNTER for CTR-mode ciphers)
   * \param iv_len        IV length for ciphers with variable-size IV;
   *                      discarded by ciphers with fixed-size IV.
   * \param ad            Additional data to be authenticated.
   * \param ad_len        Length of ad.
   * \param input         buffer holding the input data
   * \param ilen          length of the input data
   * \param output        buffer for the output data.
   *                      Should be able to hold at least ilen.
   * \param olen          length of the output data, will be filled with the
   *                      actual number of bytes written.
   * \param tag           buffer holding the authentication tag
   * \param tag_len       length of the authentication tag
   *
   * \returns             0 on success, or
   *                      MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA, or
   *                      MBEDTLS_ERR_CIPHER_AUTH_FAILED if data isn't authentic,
   *                      or a cipher specific error code.
   *
   * \note                If the data is not authentic, then the output buffer
   *                      is zeroed out to prevent the unauthentic plaintext to
   *                      be used by mistake, making this interface safer.
   */
  int mbedtls_cipher_auth_decrypt( mbedtls_cipher_context_t *ctx,
                           const unsigned char *iv, size_t iv_len,
                           const unsigned char *ad, size_t ad_len,
                           const unsigned char *input, size_t ilen,
                           unsigned char *output, size_t *olen,
                           const unsigned char *tag, size_t tag_len );
  #endif /* MBEDTLS_CIPHER_MODE_AEAD */
  
  #ifdef __cplusplus
  }
  #endif
  
  #endif /* MBEDTLS_CIPHER_H */
  