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/*
* CBC Mode
* (C) 1999-2007,2013 Jack Lloyd
*
* Distributed under the terms of the Botan license
*/
#include <botan/cbc.h>
#include <botan/loadstor.h>
#include <botan/internal/xor_buf.h>
#include <botan/internal/rounding.h>
namespace Botan {
CBC_Mode::CBC_Mode(BlockCipher* cipher, BlockCipherModePaddingMethod* padding) :
m_cipher(cipher),
m_padding(padding),
m_state(m_cipher->block_size())
{
if(!m_padding->valid_blocksize(cipher->block_size()))
throw std::invalid_argument("Padding " + m_padding->name() +
" cannot be used with " +
cipher->name() + "/CBC");
}
void CBC_Mode::clear()
{
m_cipher->clear();
m_state.clear();
}
std::string CBC_Mode::name() const
{
return cipher().name() + "/CBC";
}
size_t CBC_Mode::update_granularity() const
{
return cipher().parallel_bytes();
}
Key_Length_Specification CBC_Mode::key_spec() const
{
return cipher().key_spec();
}
size_t CBC_Mode::default_nonce_size() const
{
return cipher().block_size();
}
bool CBC_Mode::valid_nonce_length(size_t n) const
{
return (n == 0 || n == cipher().block_size());
}
void CBC_Mode::key_schedule(const byte key[], size_t length)
{
m_cipher->set_key(key, length);
}
secure_vector<byte> CBC_Mode::start(const byte nonce[], size_t nonce_len)
{
if(!valid_nonce_length(nonce_len))
throw Invalid_IV_Length(name(), nonce_len);
/*
* A nonce of zero length means carry the last ciphertext value over
* as the new IV, as unfortunately some protocols require this. If
* this is the first message then we use an IV of all zeros.
*/
if(nonce_len)
m_state.assign(nonce, nonce + nonce_len);
return secure_vector<byte>();
}
size_t CBC_Encryption::minimum_final_size() const
{
return 0;
}
size_t CBC_Encryption::output_length(size_t input_length) const
{
return round_up(input_length, cipher().block_size());
}
void CBC_Encryption::update(secure_vector<byte>& buffer, size_t offset)
{
BOTAN_ASSERT(buffer.size() >= offset, "Offset is sane");
const size_t sz = buffer.size() - offset;
byte* buf = &buffer[offset];
const size_t BS = cipher().block_size();
BOTAN_ASSERT(sz % BS == 0, "CBC input is full blocks");
const size_t blocks = sz / BS;
if(blocks)
{
xor_buf(&buf[0], &state()[0], BS);
cipher().encrypt(&buf[0]);
for(size_t i = 1; i != blocks; ++i)
{
xor_buf(&buf[BS*i], &buf[BS*(i-1)], BS);
cipher().encrypt(&buf[BS*i]);
}
state().assign(&buf[BS*(blocks-1)], &buf[BS*blocks]);
}
}
void CBC_Encryption::finish(secure_vector<byte>& buffer, size_t offset)
{
BOTAN_ASSERT(buffer.size() >= offset, "Offset is sane");
const size_t sz = buffer.size() - offset;
//byte* buf = &buffer[offset];
const size_t BS = cipher().block_size();
const size_t bytes_in_final_block = sz % BS;
const size_t pad_bytes = padding().pad_bytes(BS, bytes_in_final_block);
if((pad_bytes + bytes_in_final_block) % BS)
throw std::runtime_error("Did not pad to full block size in " + name());
#if 0
const size_t pad_offset = buffer.size();
//buffer.resize(checked_add(buffer.size() + pad_bytes));
buffer.resize(buffer.size() + pad_bytes);
padder().pad(&buffer[pad_offset], BS, bytes_in_final_block);
#else
std::vector<byte> pad(BS);
padding().pad(&pad[0], BS, bytes_in_final_block);
buffer.insert(buffer.end(), pad.begin(), pad.begin() + pad_bytes);
#endif
update(buffer, offset);
}
size_t CBC_Decryption::output_length(size_t input_length) const
{
return input_length;
}
size_t CBC_Decryption::minimum_final_size() const
{
return cipher().block_size();
}
void CBC_Decryption::update(secure_vector<byte>& buffer, size_t offset)
{
BOTAN_ASSERT(buffer.size() >= offset, "Offset is sane");
const size_t sz = buffer.size() - offset;
byte* buf = &buffer[offset];
const size_t BS = cipher().block_size();
BOTAN_ASSERT(sz % BS == 0, "Input is full blocks");
size_t blocks = sz / BS;
secure_vector<byte> temp(update_granularity());
while(blocks)
{
const size_t to_proc = std::min(sz, temp.size());
cipher().decrypt_n(buf, &temp[0], to_proc / BS);
xor_buf(&temp[0], state_ptr(), BS);
xor_buf(&temp[BS], buf, to_proc - BS);
copy_mem(state_ptr(), buf + (to_proc - BS), BS);
copy_mem(buf, &temp[0], to_proc);
buf += to_proc;
blocks -= to_proc / BS;
}
}
void CBC_Decryption::finish(secure_vector<byte>& buffer, size_t offset)
{
BOTAN_ASSERT(buffer.size() >= offset, "Offset is sane");
const size_t sz = buffer.size() - offset;
const size_t BS = cipher().block_size();
if(sz == 0 || sz % BS)
throw Decoding_Error(name() + ": Ciphertext not a multiple of block size");
update(buffer, offset);
const size_t pad_bytes = BS - padding().unpad(&buffer[buffer.size()-BS], BS);
buffer.resize(buffer.size() - pad_bytes); // remove padding
}
}
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