text: /**
   * \file cipher.c
   *
   * \brief Generic cipher wrapper for mbed TLS
   *
   * \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)
   */
  
  #if !defined(MBEDTLS_CONFIG_FILE)
  #include "mbedtls/config.h"
  #else
  #include MBEDTLS_CONFIG_FILE
  #endif
  
  #if defined(MBEDTLS_CIPHER_C)
  
  #include "mbedtls/cipher.h"
  #include "mbedtls/cipher_internal.h"
  
  #include <stdlib.h>
  #include <string.h>
  
  #if defined(MBEDTLS_GCM_C)
  #include "mbedtls/gcm.h"
  #endif
  
  #if defined(MBEDTLS_CCM_C)
  #include "mbedtls/ccm.h"
  #endif
  
  #if defined(MBEDTLS_CMAC_C)
  #include "mbedtls/cmac.h"
  #endif
  
  #if defined(MBEDTLS_PLATFORM_C)
  #include "mbedtls/platform.h"
  #else
  #define mbedtls_calloc calloc
  #define mbedtls_free   free
  #endif
  
  #if defined(MBEDTLS_ARC4_C) || defined(MBEDTLS_CIPHER_NULL_CIPHER)
  #define MBEDTLS_CIPHER_MODE_STREAM
  #endif
  
  /* Implementation that should never be optimized out by the compiler */
  static void mbedtls_zeroize( void *v, size_t n ) {
      volatile unsigned char *p = (unsigned char*)v; while( n-- ) *p++ = 0;
  }
  
  static int supported_init = 0;
  
  const int *mbedtls_cipher_list( void )
  {
      const mbedtls_cipher_definition_t *def;
      int *type;
  
      if( ! supported_init )
      {
          def = mbedtls_cipher_definitions;
          type = mbedtls_cipher_supported;
  
          while( def->type != 0 )
              *type++ = (*def++).type;
  
          *type = 0;
  
          supported_init = 1;
      }
  
      return( mbedtls_cipher_supported );
  }
  
  const mbedtls_cipher_info_t *mbedtls_cipher_info_from_type( const mbedtls_cipher_type_t cipher_type )
  {
      const mbedtls_cipher_definition_t *def;
  
      for( def = mbedtls_cipher_definitions; def->info != NULL; def++ )
          if( def->type == cipher_type )
              return( def->info );
  
      return( NULL );
  }
  
  const mbedtls_cipher_info_t *mbedtls_cipher_info_from_string( const char *cipher_name )
  {
      const mbedtls_cipher_definition_t *def;
  
      if( NULL == cipher_name )
          return( NULL );
  
      for( def = mbedtls_cipher_definitions; def->info != NULL; def++ )
          if( !  strcmp( def->info->name, cipher_name ) )
              return( def->info );
  
      return( NULL );
  }
  
  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 )
  {
      const mbedtls_cipher_definition_t *def;
  
      for( def = mbedtls_cipher_definitions; def->info != NULL; def++ )
          if( def->info->base->cipher == cipher_id &&
              def->info->key_bitlen == (unsigned) key_bitlen &&
              def->info->mode == mode )
              return( def->info );
  
      return( NULL );
  }
  
  void mbedtls_cipher_init( mbedtls_cipher_context_t *ctx )
  {
      memset( ctx, 0, sizeof( mbedtls_cipher_context_t ) );
  }
  
  void mbedtls_cipher_free( mbedtls_cipher_context_t *ctx )
  {
      if( ctx == NULL )
          return;
  
  #if defined(MBEDTLS_CMAC_C)
      if( ctx->cmac_ctx )
      {
         mbedtls_zeroize( ctx->cmac_ctx, sizeof( mbedtls_cmac_context_t ) );
         mbedtls_free( ctx->cmac_ctx );
      }
  #endif
  
      if( ctx->cipher_ctx )
          ctx->cipher_info->base->ctx_free_func( ctx->cipher_ctx );
  
      mbedtls_zeroize( ctx, sizeof(mbedtls_cipher_context_t) );
  }
  
  int mbedtls_cipher_setup( mbedtls_cipher_context_t *ctx, const mbedtls_cipher_info_t *cipher_info )
  {
      if( NULL == cipher_info || NULL == ctx )
          return( MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
  
      memset( ctx, 0, sizeof( mbedtls_cipher_context_t ) );
  
      if( NULL == ( ctx->cipher_ctx = cipher_info->base->ctx_alloc_func() ) )
          return( MBEDTLS_ERR_CIPHER_ALLOC_FAILED );
  
      ctx->cipher_info = cipher_info;
  
  #if defined(MBEDTLS_CIPHER_MODE_WITH_PADDING)
      /*
       * Ignore possible errors caused by a cipher mode that doesn't use padding
       */
  #if defined(MBEDTLS_CIPHER_PADDING_PKCS7)
      (void) mbedtls_cipher_set_padding_mode( ctx, MBEDTLS_PADDING_PKCS7 );
  #else
      (void) mbedtls_cipher_set_padding_mode( ctx, MBEDTLS_PADDING_NONE );
  #endif
  #endif /* MBEDTLS_CIPHER_MODE_WITH_PADDING */
  
      return( 0 );
  }
  
  int mbedtls_cipher_setkey( mbedtls_cipher_context_t *ctx, const unsigned char *key,
          int key_bitlen, const mbedtls_operation_t operation )
  {
      if( NULL == ctx || NULL == ctx->cipher_info )
          return( MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
  
      if( ( ctx->cipher_info->flags & MBEDTLS_CIPHER_VARIABLE_KEY_LEN ) == 0 &&
          (int) ctx->cipher_info->key_bitlen != key_bitlen )
      {
          return( MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
      }
  
      ctx->key_bitlen = key_bitlen;
      ctx->operation = operation;
  
      /*
       * For CFB and CTR mode always use the encryption key schedule
       */
      if( MBEDTLS_ENCRYPT == operation ||
          MBEDTLS_MODE_CFB == ctx->cipher_info->mode ||
          MBEDTLS_MODE_CTR == ctx->cipher_info->mode )
      {
          return ctx->cipher_info->base->setkey_enc_func( ctx->cipher_ctx, key,
                  ctx->key_bitlen );
      }
  
      if( MBEDTLS_DECRYPT == operation )
          return ctx->cipher_info->base->setkey_dec_func( ctx->cipher_ctx, key,
                  ctx->key_bitlen );
  
      return( MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
  }
  
  int mbedtls_cipher_set_iv( mbedtls_cipher_context_t *ctx,
                     const unsigned char *iv, size_t iv_len )
  {
      size_t actual_iv_size;
  
      if( NULL == ctx || NULL == ctx->cipher_info || NULL == iv )
          return( MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
  
      /* avoid buffer overflow in ctx->iv */
      if( iv_len > MBEDTLS_MAX_IV_LENGTH )
          return( MBEDTLS_ERR_CIPHER_FEATURE_UNAVAILABLE );
  
      if( ( ctx->cipher_info->flags & MBEDTLS_CIPHER_VARIABLE_IV_LEN ) != 0 )
          actual_iv_size = iv_len;
      else
      {
          actual_iv_size = ctx->cipher_info->iv_size;
  
          /* avoid reading past the end of input buffer */
          if( actual_iv_size > iv_len )
              return( MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
      }
  
      memcpy( ctx->iv, iv, actual_iv_size );
      ctx->iv_size = actual_iv_size;
  
      return( 0 );
  }
  
  int mbedtls_cipher_reset( mbedtls_cipher_context_t *ctx )
  {
      if( NULL == ctx || NULL == ctx->cipher_info )
          return( MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
  
      ctx->unprocessed_len = 0;
  
      return( 0 );
  }
  
  #if defined(MBEDTLS_GCM_C)
  int mbedtls_cipher_update_ad( mbedtls_cipher_context_t *ctx,
                        const unsigned char *ad, size_t ad_len )
  {
      if( NULL == ctx || NULL == ctx->cipher_info )
          return( MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
  
      if( MBEDTLS_MODE_GCM == ctx->cipher_info->mode )
      {
          return mbedtls_gcm_starts( (mbedtls_gcm_context *) ctx->cipher_ctx, ctx->operation,
                             ctx->iv, ctx->iv_size, ad, ad_len );
      }
  
      return( 0 );
  }
  #endif /* MBEDTLS_GCM_C */
  
  int mbedtls_cipher_update( mbedtls_cipher_context_t *ctx, const unsigned char *input,
                     size_t ilen, unsigned char *output, size_t *olen )
  {
      int ret;
      size_t block_size = 0;
  
      if( NULL == ctx || NULL == ctx->cipher_info || NULL == olen )
      {
          return( MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
      }
  
      *olen = 0;
      block_size = mbedtls_cipher_get_block_size( ctx );
  
      if( ctx->cipher_info->mode == MBEDTLS_MODE_ECB )
      {
          if( ilen != block_size )
              return( MBEDTLS_ERR_CIPHER_FULL_BLOCK_EXPECTED );
  
          *olen = ilen;
  
          if( 0 != ( ret = ctx->cipher_info->base->ecb_func( ctx->cipher_ctx,
                      ctx->operation, input, output ) ) )
          {
              return( ret );
          }
  
          return( 0 );
      }
  
      if ( 0 == block_size )
      {
          return MBEDTLS_ERR_CIPHER_INVALID_CONTEXT;
      }
  
      if( input == output &&
         ( ctx->unprocessed_len != 0 || ilen % block_size ) )
      {
          return( MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
      }
  
  #if defined(MBEDTLS_GCM_C)
      if( ctx->cipher_info->mode == MBEDTLS_MODE_GCM )
      {
          size_t copy_len = 0;
  
          /*
           * If there is not enough data for a full block, cache it.
           */
          if( ( ctx->operation == MBEDTLS_DECRYPT && ilen + ctx->unprocessed_len <= block_size ) ||
               ( ctx->operation == MBEDTLS_ENCRYPT && ilen + ctx->unprocessed_len < block_size ) )
          {
              memcpy( &( ctx->unprocessed_data[ctx->unprocessed_len] ), input,
                      ilen );
  
              ctx->unprocessed_len += ilen;
              return( 0 );
          }
  
          /*
           * Process cached data first
           */
          if( ctx->unprocessed_len != 0 )
          {
              copy_len = block_size - ctx->unprocessed_len;
  
              memcpy( &( ctx->unprocessed_data[ctx->unprocessed_len] ), input,
                      copy_len );
  
              ctx->unprocessed_len += copy_len;
  
              if( 0 != ( ret = mbedtls_gcm_update( (mbedtls_gcm_context *) ctx->cipher_ctx,
                      ctx->unprocessed_len, ctx->unprocessed_data, output ) ) )
              {
                  return( ret );
              }
  
              *olen += block_size;
              output += block_size;
              ctx->unprocessed_len = 0;
  
              input += copy_len;
              ilen -= copy_len;
          }
  
          /*
           * Cache final, incomplete block
           */
          if( 0 != ilen )
          {
              copy_len = ilen % block_size;
              if( copy_len == 0 && ctx->operation == MBEDTLS_DECRYPT )
                  copy_len = block_size;
  
              memcpy( ctx->unprocessed_data, &( input[ilen - copy_len] ),
                      copy_len );
  
              ctx->unprocessed_len += copy_len;
              ilen -= copy_len;
          }
  
          /*
           * Process remaining full blocks
           */
          if( ilen )
          {
              if( 0 != ( ret = mbedtls_gcm_update( (mbedtls_gcm_context *) ctx->cipher_ctx,
                      ilen, input, output ) ) )
              {
                  return( ret );
              }
  
              *olen += ilen;
          }
  
          return( 0 );
      }
  #endif /* MBEDTLS_GCM_C */
  
  #if defined(MBEDTLS_CIPHER_MODE_CBC)
      if( ctx->cipher_info->mode == MBEDTLS_MODE_CBC )
      {
          size_t copy_len = 0;
  
          /*
           * If there is not enough data for a full block, cache it.
           */
          if( ( ctx->operation == MBEDTLS_DECRYPT &&
                  ilen <= block_size - ctx->unprocessed_len ) ||
               ( ctx->operation == MBEDTLS_ENCRYPT &&
                  ilen < block_size - ctx->unprocessed_len ) )
          {
              memcpy( &( ctx->unprocessed_data[ctx->unprocessed_len] ), input,
                      ilen );
  
              ctx->unprocessed_len += ilen;
              return( 0 );
          }
  
          /*
           * Process cached data first
           */
          if( 0 != ctx->unprocessed_len )
          {
              copy_len = block_size - ctx->unprocessed_len;
  
              memcpy( &( ctx->unprocessed_data[ctx->unprocessed_len] ), input,
                      copy_len );
  
              if( 0 != ( ret = ctx->cipher_info->base->cbc_func( ctx->cipher_ctx,
                      ctx->operation, block_size, ctx->iv,
                      ctx->unprocessed_data, output ) ) )
              {
                  return( ret );
              }
  
              *olen += block_size;
              output += block_size;
              ctx->unprocessed_len = 0;
  
              input += copy_len;
              ilen -= copy_len;
          }
  
          /*
           * Cache final, incomplete block
           */
          if( 0 != ilen )
          {
              if( 0 == block_size )
              {
                  return MBEDTLS_ERR_CIPHER_INVALID_CONTEXT;
              }
  
              copy_len = ilen % block_size;
              if( copy_len == 0 && ctx->operation == MBEDTLS_DECRYPT )
                  copy_len = block_size;
  
              memcpy( ctx->unprocessed_data, &( input[ilen - copy_len] ),
                      copy_len );
  
              ctx->unprocessed_len += copy_len;
              ilen -= copy_len;
          }
  
          /*
           * Process remaining full blocks
           */
          if( ilen )
          {
              if( 0 != ( ret = ctx->cipher_info->base->cbc_func( ctx->cipher_ctx,
                      ctx->operation, ilen, ctx->iv, input, output ) ) )
              {
                  return( ret );
              }
  
              *olen += ilen;
          }
  
          return( 0 );
      }
  #endif /* MBEDTLS_CIPHER_MODE_CBC */
  
  #if defined(MBEDTLS_CIPHER_MODE_CFB)
      if( ctx->cipher_info->mode == MBEDTLS_MODE_CFB )
      {
          if( 0 != ( ret = ctx->cipher_info->base->cfb_func( ctx->cipher_ctx,
                  ctx->operation, ilen, &ctx->unprocessed_len, ctx->iv,
                  input, output ) ) )
          {
              return( ret );
          }
  
          *olen = ilen;
  
          return( 0 );
      }
  #endif /* MBEDTLS_CIPHER_MODE_CFB */
  
  #if defined(MBEDTLS_CIPHER_MODE_CTR)
      if( ctx->cipher_info->mode == MBEDTLS_MODE_CTR )
      {
          if( 0 != ( ret = ctx->cipher_info->base->ctr_func( ctx->cipher_ctx,
                  ilen, &ctx->unprocessed_len, ctx->iv,
                  ctx->unprocessed_data, input, output ) ) )
          {
              return( ret );
          }
  
          *olen = ilen;
  
          return( 0 );
      }
  #endif /* MBEDTLS_CIPHER_MODE_CTR */
  
  #if defined(MBEDTLS_CIPHER_MODE_STREAM)
      if( ctx->cipher_info->mode == MBEDTLS_MODE_STREAM )
      {
          if( 0 != ( ret = ctx->cipher_info->base->stream_func( ctx->cipher_ctx,
                                                      ilen, input, output ) ) )
          {
              return( ret );
          }
  
          *olen = ilen;
  
          return( 0 );
      }
  #endif /* MBEDTLS_CIPHER_MODE_STREAM */
  
      return( MBEDTLS_ERR_CIPHER_FEATURE_UNAVAILABLE );
  }
  
  #if defined(MBEDTLS_CIPHER_MODE_WITH_PADDING)
  #if defined(MBEDTLS_CIPHER_PADDING_PKCS7)
  /*
   * PKCS7 (and PKCS5) padding: fill with ll bytes, with ll = padding_len
   */
  static void add_pkcs_padding( unsigned char *output, size_t output_len,
          size_t data_len )
  {
      size_t padding_len = output_len - data_len;
      unsigned char i;
  
      for( i = 0; i < padding_len; i++ )
          output[data_len + i] = (unsigned char) padding_len;
  }
  
  static int get_pkcs_padding( unsigned char *input, size_t input_len,
          size_t *data_len )
  {
      size_t i, pad_idx;
      unsigned char padding_len, bad = 0;
  
      if( NULL == input || NULL == data_len )
          return( MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
  
      padding_len = input[input_len - 1];
      *data_len = input_len - padding_len;
  
      /* Avoid logical || since it results in a branch */
      bad |= padding_len > input_len;
      bad |= padding_len == 0;
  
      /* The number of bytes checked must be independent of padding_len,
       * so pick input_len, which is usually 8 or 16 (one block) */
      pad_idx = input_len - padding_len;
      for( i = 0; i < input_len; i++ )
          bad |= ( input[i] ^ padding_len ) * ( i >= pad_idx );
  
      return( MBEDTLS_ERR_CIPHER_INVALID_PADDING * ( bad != 0 ) );
  }
  #endif /* MBEDTLS_CIPHER_PADDING_PKCS7 */
  
  #if defined(MBEDTLS_CIPHER_PADDING_ONE_AND_ZEROS)
  /*
   * One and zeros padding: fill with 80 00 ... 00
   */
  static void add_one_and_zeros_padding( unsigned char *output,
                                         size_t output_len, size_t data_len )
  {
      size_t padding_len = output_len - data_len;
      unsigned char i = 0;
  
      output[data_len] = 0x80;
      for( i = 1; i < padding_len; i++ )
          output[data_len + i] = 0x00;
  }
  
  static int get_one_and_zeros_padding( unsigned char *input, size_t input_len,
                                        size_t *data_len )
  {
      size_t i;
      unsigned char done = 0, prev_done, bad;
  
      if( NULL == input || NULL == data_len )
          return( MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
  
      bad = 0xFF;
      *data_len = 0;
      for( i = input_len; i > 0; i-- )
      {
          prev_done = done;
          done |= ( input[i-1] != 0 );
          *data_len |= ( i - 1 ) * ( done != prev_done );
          bad &= ( input[i-1] ^ 0x80 ) | ( done == prev_done );
      }
  
      return( MBEDTLS_ERR_CIPHER_INVALID_PADDING * ( bad != 0 ) );
  
  }
  #endif /* MBEDTLS_CIPHER_PADDING_ONE_AND_ZEROS */
  
  #if defined(MBEDTLS_CIPHER_PADDING_ZEROS_AND_LEN)
  /*
   * Zeros and len padding: fill with 00 ... 00 ll, where ll is padding length
   */
  static void add_zeros_and_len_padding( unsigned char *output,
                                         size_t output_len, size_t data_len )
  {
      size_t padding_len = output_len - data_len;
      unsigned char i = 0;
  
      for( i = 1; i < padding_len; i++ )
          output[data_len + i - 1] = 0x00;
      output[output_len - 1] = (unsigned char) padding_len;
  }
  
  static int get_zeros_and_len_padding( unsigned char *input, size_t input_len,
                                        size_t *data_len )
  {
      size_t i, pad_idx;
      unsigned char padding_len, bad = 0;
  
      if( NULL == input || NULL == data_len )
          return( MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
  
      padding_len = input[input_len - 1];
      *data_len = input_len - padding_len;
  
      /* Avoid logical || since it results in a branch */
      bad |= padding_len > input_len;
      bad |= padding_len == 0;
  
      /* The number of bytes checked must be independent of padding_len */
      pad_idx = input_len - padding_len;
      for( i = 0; i < input_len - 1; i++ )
          bad |= input[i] * ( i >= pad_idx );
  
      return( MBEDTLS_ERR_CIPHER_INVALID_PADDING * ( bad != 0 ) );
  }
  #endif /* MBEDTLS_CIPHER_PADDING_ZEROS_AND_LEN */
  
  #if defined(MBEDTLS_CIPHER_PADDING_ZEROS)
  /*
   * Zero padding: fill with 00 ... 00
   */
  static void add_zeros_padding( unsigned char *output,
                                 size_t output_len, size_t data_len )
  {
      size_t i;
  
      for( i = data_len; i < output_len; i++ )
          output[i] = 0x00;
  }
  
  static int get_zeros_padding( unsigned char *input, size_t input_len,
                                size_t *data_len )
  {
      size_t i;
      unsigned char done = 0, prev_done;
  
      if( NULL == input || NULL == data_len )
          return( MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
  
      *data_len = 0;
      for( i = input_len; i > 0; i-- )
      {
          prev_done = done;
          done |= ( input[i-1] != 0 );
          *data_len |= i * ( done != prev_done );
      }
  
      return( 0 );
  }
  #endif /* MBEDTLS_CIPHER_PADDING_ZEROS */
  
  /*
   * No padding: don't pad :)
   *
   * There is no add_padding function (check for NULL in mbedtls_cipher_finish)
   * but a trivial get_padding function
   */
  static int get_no_padding( unsigned char *input, size_t input_len,
                                size_t *data_len )
  {
      if( NULL == input || NULL == data_len )
          return( MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
  
      *data_len = input_len;
  
      return( 0 );
  }
  #endif /* MBEDTLS_CIPHER_MODE_WITH_PADDING */
  
  int mbedtls_cipher_finish( mbedtls_cipher_context_t *ctx,
                     unsigned char *output, size_t *olen )
  {
      if( NULL == ctx || NULL == ctx->cipher_info || NULL == olen )
          return( MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
  
      *olen = 0;
  
      if( MBEDTLS_MODE_CFB == ctx->cipher_info->mode ||
          MBEDTLS_MODE_CTR == ctx->cipher_info->mode ||
          MBEDTLS_MODE_STREAM == ctx->cipher_info->mode )
      {
          return( 0 );
      }
  
      if( MBEDTLS_MODE_ECB == ctx->cipher_info->mode )
      {
          if( ctx->unprocessed_len != 0 )
              return( MBEDTLS_ERR_CIPHER_FULL_BLOCK_EXPECTED );
  
          return( 0 );
      }
  
  #if defined(MBEDTLS_GCM_C)
      if( MBEDTLS_MODE_GCM == ctx->cipher_info->mode )
      {
          /* cipher block */
          *olen = ctx->unprocessed_len;
          return mbedtls_gcm_update( (mbedtls_gcm_context *) ctx->cipher_ctx,
                  ctx->unprocessed_len, ctx->unprocessed_data, output );
      }
  #endif /* MBEDTLS_GCM_C */
  
  #if defined(MBEDTLS_CIPHER_MODE_CBC)
      if( MBEDTLS_MODE_CBC == ctx->cipher_info->mode )
      {
          int ret = 0;
  
          if( MBEDTLS_ENCRYPT == ctx->operation )
          {
              /* check for 'no padding' mode */
              if( NULL == ctx->add_padding )
              {
                  if( 0 != ctx->unprocessed_len )
                      return( MBEDTLS_ERR_CIPHER_FULL_BLOCK_EXPECTED );
  
                  return( 0 );
              }
  
              ctx->add_padding( ctx->unprocessed_data, mbedtls_cipher_get_block_size( ctx ),
                      ctx->unprocessed_len );
          }
          else if( mbedtls_cipher_get_block_size( ctx ) != ctx->unprocessed_len )
          {
              /*
               * For decrypt operations, expect a full block,
               * or an empty block if no padding
               */
              if( NULL == ctx->add_padding && 0 == ctx->unprocessed_len )
                  return( 0 );
  
              return( MBEDTLS_ERR_CIPHER_FULL_BLOCK_EXPECTED );
          }
  
          /* cipher block */
          if( 0 != ( ret = ctx->cipher_info->base->cbc_func( ctx->cipher_ctx,
                  ctx->operation, mbedtls_cipher_get_block_size( ctx ), ctx->iv,
                  ctx->unprocessed_data, output ) ) )
          {
              return( ret );
          }
  
          /* Set output size for decryption */
          if( MBEDTLS_DECRYPT == ctx->operation )
              return ctx->get_padding( output, mbedtls_cipher_get_block_size( ctx ),
                                       olen );
  
          /* Set output size for encryption */
          *olen = mbedtls_cipher_get_block_size( ctx );
          return( 0 );
      }
  #endif /* MBEDTLS_CIPHER_MODE_CBC */
  
  #if !defined(MBEDTLS_MODE_CBC) && !defined(MBEDTLS_MODE_GCM)
      ((void) output);
  #endif
      return( MBEDTLS_ERR_CIPHER_FEATURE_UNAVAILABLE );
  }
  
  #if defined(MBEDTLS_CIPHER_MODE_WITH_PADDING)
  int mbedtls_cipher_set_padding_mode( mbedtls_cipher_context_t *ctx, mbedtls_cipher_padding_t mode )
  {
      if( NULL == ctx ||
          MBEDTLS_MODE_CBC != ctx->cipher_info->mode )
      {
          return( MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
      }
  
      switch( mode )
      {
  #if defined(MBEDTLS_CIPHER_PADDING_PKCS7)
      case MBEDTLS_PADDING_PKCS7:
          ctx->add_padding = add_pkcs_padding;
          ctx->get_padding = get_pkcs_padding;
          break;
  #endif
  #if defined(MBEDTLS_CIPHER_PADDING_ONE_AND_ZEROS)
      case MBEDTLS_PADDING_ONE_AND_ZEROS:
          ctx->add_padding = add_one_and_zeros_padding;
          ctx->get_padding = get_one_and_zeros_padding;
          break;
  #endif
  #if defined(MBEDTLS_CIPHER_PADDING_ZEROS_AND_LEN)
      case MBEDTLS_PADDING_ZEROS_AND_LEN:
          ctx->add_padding = add_zeros_and_len_padding;
          ctx->get_padding = get_zeros_and_len_padding;
          break;
  #endif
  #if defined(MBEDTLS_CIPHER_PADDING_ZEROS)
      case MBEDTLS_PADDING_ZEROS:
          ctx->add_padding = add_zeros_padding;
          ctx->get_padding = get_zeros_padding;
          break;
  #endif
      case MBEDTLS_PADDING_NONE:
          ctx->add_padding = NULL;
          ctx->get_padding = get_no_padding;
          break;
  
      default:
          return( MBEDTLS_ERR_CIPHER_FEATURE_UNAVAILABLE );
      }
  
      return( 0 );
  }
  #endif /* MBEDTLS_CIPHER_MODE_WITH_PADDING */
  
  #if defined(MBEDTLS_GCM_C)
  int mbedtls_cipher_write_tag( mbedtls_cipher_context_t *ctx,
                        unsigned char *tag, size_t tag_len )
  {
      if( NULL == ctx || NULL == ctx->cipher_info || NULL == tag )
          return( MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
  
      if( MBEDTLS_ENCRYPT != ctx->operation )
          return( MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
  
      if( MBEDTLS_MODE_GCM == ctx->cipher_info->mode )
          return mbedtls_gcm_finish( (mbedtls_gcm_context *) ctx->cipher_ctx, tag, tag_len );
  
      return( 0 );
  }
  
  int mbedtls_cipher_check_tag( mbedtls_cipher_context_t *ctx,
                        const unsigned char *tag, size_t tag_len )
  {
      int ret;
  
      if( NULL == ctx || NULL == ctx->cipher_info ||
          MBEDTLS_DECRYPT != ctx->operation )
      {
          return( MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
      }
  
      if( MBEDTLS_MODE_GCM == ctx->cipher_info->mode )
      {
          unsigned char check_tag[16];
          size_t i;
          int diff;
  
          if( tag_len > sizeof( check_tag ) )
              return( MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
  
          if( 0 != ( ret = mbedtls_gcm_finish( (mbedtls_gcm_context *) ctx->cipher_ctx,
                                       check_tag, tag_len ) ) )
          {
              return( ret );
          }
  
          /* Check the tag in "constant-time" */
          for( diff = 0, i = 0; i < tag_len; i++ )
              diff |= tag[i] ^ check_tag[i];
  
          if( diff != 0 )
              return( MBEDTLS_ERR_CIPHER_AUTH_FAILED );
  
          return( 0 );
      }
  
      return( 0 );
  }
  #endif /* MBEDTLS_GCM_C */
  
  /*
   * Packet-oriented wrapper for non-AEAD modes
   */
  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 )
  {
      int ret;
      size_t finish_olen;
  
      if( ( ret = mbedtls_cipher_set_iv( ctx, iv, iv_len ) ) != 0 )
          return( ret );
  
      if( ( ret = mbedtls_cipher_reset( ctx ) ) != 0 )
          return( ret );
  
      if( ( ret = mbedtls_cipher_update( ctx, input, ilen, output, olen ) ) != 0 )
          return( ret );
  
      if( ( ret = mbedtls_cipher_finish( ctx, output + *olen, &finish_olen ) ) != 0 )
          return( ret );
  
      *olen += finish_olen;
  
      return( 0 );
  }
  
  #if defined(MBEDTLS_CIPHER_MODE_AEAD)
  /*
   * Packet-oriented encryption for AEAD modes
   */
  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 )
  {
  #if defined(MBEDTLS_GCM_C)
      if( MBEDTLS_MODE_GCM == ctx->cipher_info->mode )
      {
          *olen = ilen;
          return( mbedtls_gcm_crypt_and_tag( ctx->cipher_ctx, MBEDTLS_GCM_ENCRYPT, ilen,
                                     iv, iv_len, ad, ad_len, input, output,
                                     tag_len, tag ) );
      }
  #endif /* MBEDTLS_GCM_C */
  #if defined(MBEDTLS_CCM_C)
      if( MBEDTLS_MODE_CCM == ctx->cipher_info->mode )
      {
          *olen = ilen;
          return( mbedtls_ccm_encrypt_and_tag( ctx->cipher_ctx, ilen,
                                       iv, iv_len, ad, ad_len, input, output,
                                       tag, tag_len ) );
      }
  #endif /* MBEDTLS_CCM_C */
  
      return( MBEDTLS_ERR_CIPHER_FEATURE_UNAVAILABLE );
  }
  
  /*
   * Packet-oriented decryption for AEAD modes
   */
  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 )
  {
  #if defined(MBEDTLS_GCM_C)
      if( MBEDTLS_MODE_GCM == ctx->cipher_info->mode )
      {
          int ret;
  
          *olen = ilen;
          ret = mbedtls_gcm_auth_decrypt( ctx->cipher_ctx, ilen,
                                  iv, iv_len, ad, ad_len,
                                  tag, tag_len, input, output );
  
          if( ret == MBEDTLS_ERR_GCM_AUTH_FAILED )
              ret = MBEDTLS_ERR_CIPHER_AUTH_FAILED;
  
          return( ret );
      }
  #endif /* MBEDTLS_GCM_C */
  #if defined(MBEDTLS_CCM_C)
      if( MBEDTLS_MODE_CCM == ctx->cipher_info->mode )
      {
          int ret;
  
          *olen = ilen;
          ret = mbedtls_ccm_auth_decrypt( ctx->cipher_ctx, ilen,
                                  iv, iv_len, ad, ad_len,
                                  input, output, tag, tag_len );
  
          if( ret == MBEDTLS_ERR_CCM_AUTH_FAILED )
              ret = MBEDTLS_ERR_CIPHER_AUTH_FAILED;
  
          return( ret );
      }
  #endif /* MBEDTLS_CCM_C */
  
      return( MBEDTLS_ERR_CIPHER_FEATURE_UNAVAILABLE );
  }
  #endif /* MBEDTLS_CIPHER_MODE_AEAD */
  
  #endif /* MBEDTLS_CIPHER_C */
  