src/filters/modes/mode_pad/mode_pad.cpp

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/*
* CBC Padding Methods
* (C) 1999-2007 Jack Lloyd
*
* Distributed under the terms of the Botan license
*/

#include <botan/mode_pad.h>
#include <botan/exceptn.h>

namespace Botan {

/*
* Default amount of padding
*/
u32bit BlockCipherModePaddingMethod::pad_bytes(u32bit bs, u32bit pos) const
   {
   return (bs - pos);
   }

/*
* Pad with PKCS #7 Method
*/
void PKCS7_Padding::pad(byte block[], u32bit size, u32bit position) const
   {
   for(u32bit j = 0; j != size; ++j)
      block[j] = (size-position);
   }

/*
* Unpad with PKCS #7 Method
*/
u32bit PKCS7_Padding::unpad(const byte block[], u32bit size) const
   {
   u32bit position = block[size-1];
   if(position > size)
      throw Decoding_Error(name());
   for(u32bit j = size-position; j != size-1; ++j)
      if(block[j] != position)
         throw Decoding_Error(name());
   return (size-position);
   }

/*
* Query if the size is valid for this method
*/
bool PKCS7_Padding::valid_blocksize(u32bit size) const
   {
   if(size > 0 && size < 256)
      return true;
   else
      return false;
   }

/*
* Pad with ANSI X9.23 Method
*/
void ANSI_X923_Padding::pad(byte block[], u32bit size, u32bit position) const
   {
   for(u32bit j = 0; j != size-position; ++j)
      block[j] = 0;
   block[size-position-1] = (size-position);
   }

/*
* Unpad with ANSI X9.23 Method
*/
u32bit ANSI_X923_Padding::unpad(const byte block[], u32bit size) const
   {
   u32bit position = block[size-1];
   if(position > size)
      throw Decoding_Error(name());
   for(u32bit j = size-position; j != size-1; ++j)
      if(block[j] != 0)
         throw Decoding_Error(name());
   return (size-position);
   }

/*
* Query if the size is valid for this method
*/
bool ANSI_X923_Padding::valid_blocksize(u32bit size) const
   {
   if(size > 0 && size < 256)
      return true;
   else
      return false;
   }

/*
* Pad with One and Zeros Method
*/
void OneAndZeros_Padding::pad(byte block[], u32bit size, u32bit) const
   {
   block[0] = 0x80;
   for(u32bit j = 1; j != size; ++j)
      block[j] = 0x00;
   }

/*
* Unpad with One and Zeros Method
*/
u32bit OneAndZeros_Padding::unpad(const byte block[], u32bit size) const
   {
   while(size)
      {
      if(block[size-1] == 0x80)
         break;
      if(block[size-1] != 0x00)
         throw Decoding_Error(name());
      size--;
      }
   if(!size)
      throw Decoding_Error(name());
   return (size-1);
   }

/*
* Query if the size is valid for this method
*/
bool OneAndZeros_Padding::valid_blocksize(u32bit size) const
   {
   return (size > 0);
   }

}

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