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/*
* CBC Padding Methods
* (C) 1999-2007,2013 Jack Lloyd
* (C) 2016 René Korthaus, Rohde & Schwarz Cybersecurity
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#include <botan/mode_pad.h>
#include <botan/exceptn.h>
namespace Botan {
/**
* Get a block cipher padding method by name
*/
BlockCipherModePaddingMethod* get_bc_pad(const std::string& algo_spec)
{
if(algo_spec == "NoPadding")
return new Null_Padding;
if(algo_spec == "PKCS7")
return new PKCS7_Padding;
if(algo_spec == "OneAndZeros")
return new OneAndZeros_Padding;
if(algo_spec == "X9.23")
return new ANSI_X923_Padding;
if(algo_spec == "ESP")
return new ESP_Padding;
return nullptr;
}
/*
* Pad with PKCS #7 Method
*/
void PKCS7_Padding::add_padding(secure_vector<byte>& buffer,
size_t last_byte_pos,
size_t block_size) const
{
const byte pad_value = static_cast<byte>(block_size - last_byte_pos);
for(size_t i = 0; i != pad_value; ++i)
buffer.push_back(pad_value);
}
/*
* Unpad with PKCS #7 Method
*/
size_t PKCS7_Padding::unpad(const byte block[], size_t size) const
{
size_t position = block[size-1];
if(position > size)
throw Decoding_Error("Bad padding in " + name());
for(size_t j = size-position; j != size-1; ++j)
if(block[j] != position)
throw Decoding_Error("Bad padding in " + name());
return (size-position);
}
/*
* Pad with ANSI X9.23 Method
*/
void ANSI_X923_Padding::add_padding(secure_vector<byte>& buffer,
size_t last_byte_pos,
size_t block_size) const
{
const byte pad_value = static_cast<byte>(block_size - last_byte_pos);
for(size_t i = last_byte_pos; i < block_size-1; ++i)
{
buffer.push_back(0);
}
buffer.push_back(pad_value);
}
/*
* Unpad with ANSI X9.23 Method
*/
size_t ANSI_X923_Padding::unpad(const byte block[], size_t size) const
{
size_t position = block[size-1];
if(position > size)
throw Decoding_Error(name());
for(size_t j = size-position; j != size-1; ++j)
if(block[j] != 0)
throw Decoding_Error(name());
return (size-position);
}
/*
* Pad with One and Zeros Method
*/
void OneAndZeros_Padding::add_padding(secure_vector<byte>& buffer,
size_t last_byte_pos,
size_t block_size) const
{
buffer.push_back(0x80);
for(size_t i = last_byte_pos + 1; i % block_size; ++i)
buffer.push_back(0x00);
}
/*
* Unpad with One and Zeros Method
*/
size_t OneAndZeros_Padding::unpad(const byte block[], size_t 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);
}
/*
* Pad with ESP Padding Method
*/
void ESP_Padding::add_padding(secure_vector<byte>& buffer,
size_t last_byte_pos,
size_t block_size) const
{
byte pad_value = 0x01;
for(size_t i = last_byte_pos; i < block_size; ++i)
{
buffer.push_back(pad_value++);
}
}
/*
* Unpad with ESP Padding Method
*/
size_t ESP_Padding::unpad(const byte block[], size_t size) const
{
const byte last_byte = block[size-1];
if(last_byte > size)
{
throw Decoding_Error(name());
}
// try to do this in const time by looping over the entire block
const size_t pad_pos = size - last_byte;
size_t i = size - 1;
while(i)
{
if(block[i-1] != block[i]-1)
{
if(i > pad_pos)
{
throw Decoding_Error(name());
}
}
--i;
}
return pad_pos;
}
}
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