Botan  2.8.0
Crypto and TLS for C++11
Public Member Functions | List of all members
Botan::ESP_Padding Class Referencefinal

#include <mode_pad.h>

Inheritance diagram for Botan::ESP_Padding:
Botan::BlockCipherModePaddingMethod

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 118 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
bufferdata to pad
final_block_bytessize of the final block in bytes
block_sizesize of each block in bytes

Implements Botan::BlockCipherModePaddingMethod.

Definition at line 163 of file mode_pad.cpp.

166  {
167  uint8_t pad_value = 0x01;
168 
169  for(size_t i = last_byte_pos; i < block_size; ++i)
170  {
171  buffer.push_back(pad_value++);
172  }
173  }

◆ name()

std::string Botan::ESP_Padding::name ( ) const
inlineoverridevirtual
Returns
name of the mode

Implements Botan::BlockCipherModePaddingMethod.

Definition at line 129 of file mode_pad.h.

129 { return "ESP"; }

◆ unpad()

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

Remove padding bytes from block

Parameters
blockthe last block
lenthe size of the block in bytes
Returns
number of data bytes, or if the padding is invalid returns len

Implements Botan::BlockCipherModePaddingMethod.

Definition at line 178 of file mode_pad.cpp.

References Botan::CT::conditional_return(), Botan::CT::is_zero(), Botan::CT::poison(), and Botan::CT::unpoison().

179  {
180  if(input_length <= 2)
181  return input_length;
182 
183  CT::poison(input, input_length);
184 
185  const size_t last_byte = input[input_length-1];
186  uint8_t bad_input = 0;
187  bad_input |= CT::is_zero(last_byte) | CT::expand_mask<uint8_t>(last_byte > input_length);
188 
189  const size_t pad_pos = input_length - last_byte;
190  size_t i = input_length - 1;
191  while(i)
192  {
193  const uint8_t in_range = CT::expand_mask<uint8_t>(i > pad_pos);
194  bad_input |= (~CT::is_equal<uint8_t>(input[i-1], input[i]-1)) & in_range;
195  --i;
196  }
197 
198  CT::unpoison(input, input_length);
199  return CT::conditional_return(bad_input, input_length, pad_pos);
200  }
void poison(const T *p, size_t n)
Definition: ct_utils.h:47
T is_zero(T x)
Definition: ct_utils.h:88
void unpoison(const T *p, size_t n)
Definition: ct_utils.h:58
T conditional_return(C condvar, T left, T right)
Definition: ct_utils.h:153

◆ valid_blocksize()

bool Botan::ESP_Padding::valid_blocksize ( size_t  block_size) const
inlineoverridevirtual
Parameters
block_sizeof the cipher
Returns
valid block size for this padding mode

Implements Botan::BlockCipherModePaddingMethod.

Definition at line 127 of file mode_pad.h.

127 { return (bs > 2 && bs < 256); }

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