Botan::ESP_Padding Class Reference

#include <mode_pad.h>

Inheritance diagram for Botan::ESP_Padding:

Public Member Functions
void	add_padding (secure_vector< uint8_t > &buffer, size_t final_block_bytes, size_t block_size) const override
std::string	name () const override
size_t	unpad (const uint8_t[], size_t) const override
bool	valid_blocksize (size_t bs) const override

Detailed Description

ESP Padding (RFC 4304)

Definition at line 119 of file mode_pad.h.

Member Function Documentation

add_padding()

void Botan::ESP_Padding::add_padding ( secure_vector< uint8_t > &  buffer, size_t  final_block_bytes, size_t  block_size  ) const

overridevirtual

Add padding bytes to buffer.

Parameters

buffer	data to pad
final_block_bytes	size of the final block in bytes
block_size	size of each block in bytes

Implements Botan::BlockCipherModePaddingMethod.

Definition at line 159 of file mode_pad.cpp.

   {
   uint8_t pad_value = 0x01;

   for(size_t i = last_byte_pos; i < block_size; ++i)
      {
      buffer.push_back(pad_value++);
      }
   }

name()

std::string Botan::ESP_Padding::name ( ) const

inlineoverridevirtual

Returns

name of the mode

Implements Botan::BlockCipherModePaddingMethod.

Definition at line 130 of file mode_pad.h.

{ return "ESP"; }

unpad()

size_t Botan::ESP_Padding::unpad ( const uint8_t  block[], size_t  size  ) const

overridevirtual

Remove padding bytes from block

Parameters

block	the last block
size	the size of the block in bytes

Returns

number of padding bytes

Implements Botan::BlockCipherModePaddingMethod.

Definition at line 174 of file mode_pad.cpp.

References Botan::CT::conditional_copy_mem(), Botan::CT::poison(), and Botan::CT::unpoison().

   {
   CT::poison(block,size);

   const size_t last_byte = block[size-1];
   size_t bad_input = 0;
   bad_input |= CT::expand_mask<size_t>(last_byte > size);

   size_t pad_pos = size - last_byte;
   size_t i = size - 1;
   while(i)
      {
      bad_input |= ~CT::is_equal<uint8_t>(size_t(block[i-1]),size_t(block[i])-1) & CT::expand_mask<uint8_t>(i > pad_pos);
      --i;
      }
   CT::conditional_copy_mem(bad_input,&pad_pos,&size,&pad_pos,1);
   CT::unpoison(block, size);
   CT::unpoison(pad_pos);
   return pad_pos;
   }

valid_blocksize()

bool Botan::ESP_Padding::valid_blocksize ( size_t  block_size ) const

inlineoverridevirtual

Parameters

block_size

of the cipher

Returns

valid block size for this padding mode

Implements Botan::BlockCipherModePaddingMethod.

Definition at line 128 of file mode_pad.h.

{ return (bs > 0); }

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The documentation for this class was generated from the following files:

• src/lib/modes/mode_pad/mode_pad.h
• src/lib/modes/mode_pad/mode_pad.cpp