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/*
* CBC Mode
* (C) 1999-2007,2013,2017 Jack Lloyd
* (C) 2016 Daniel Neus, Rohde & Schwarz Cybersecurity
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#include <botan/cbc.h>
#include <botan/mode_pad.h>
#include <botan/internal/rounding.h>
namespace Botan {
CBC_Mode::CBC_Mode(BlockCipher* cipher, BlockCipherModePaddingMethod* padding) :
m_cipher(cipher),
m_padding(padding),
m_block_size(cipher->block_size())
{
if(m_padding && !m_padding->valid_blocksize(m_block_size))
throw Invalid_Argument("Padding " + m_padding->name() +
" cannot be used with " +
cipher->name() + "/CBC");
}
void CBC_Mode::clear()
{
m_cipher->clear();
reset();
}
void CBC_Mode::reset()
{
m_state.clear();
}
std::string CBC_Mode::name() const
{
if(m_padding)
return cipher().name() + "/CBC/" + padding().name();
else
return cipher().name() + "/CBC/CTS";
}
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_length() const
{
return block_size();
}
bool CBC_Mode::valid_nonce_length(size_t n) const
{
return (n == 0 || n == block_size());
}
void CBC_Mode::key_schedule(const uint8_t key[], size_t length)
{
m_cipher->set_key(key, length);
}
void CBC_Mode::start_msg(const uint8_t 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);
else if(m_state.empty())
m_state.resize(m_cipher->block_size());
// else leave the state alone
}
size_t CBC_Encryption::minimum_final_size() const
{
return 0;
}
size_t CBC_Encryption::output_length(size_t input_length) const
{
if(input_length == 0)
return block_size();
else
return round_up(input_length, block_size());
}
size_t CBC_Encryption::process(uint8_t buf[], size_t sz)
{
BOTAN_STATE_CHECK(state().empty() == false);
const size_t BS = block_size();
BOTAN_ASSERT(sz % BS == 0, "CBC input is full blocks");
const size_t blocks = sz / BS;
if(blocks > 0)
{
xor_buf(&buf[0], state_ptr(), 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]);
}
return sz;
}
void CBC_Encryption::finish(secure_vector<uint8_t>& buffer, size_t offset)
{
BOTAN_ASSERT(buffer.size() >= offset, "Offset is sane");
const size_t BS = block_size();
const size_t bytes_in_final_block = (buffer.size()-offset) % BS;
padding().add_padding(buffer, bytes_in_final_block, BS);
if((buffer.size()-offset) % BS)
throw Exception("Did not pad to full block size in " + name());
update(buffer, offset);
}
bool CTS_Encryption::valid_nonce_length(size_t n) const
{
return (n == block_size());
}
size_t CTS_Encryption::minimum_final_size() const
{
return block_size() + 1;
}
size_t CTS_Encryption::output_length(size_t input_length) const
{
return input_length; // no ciphertext expansion in CTS
}
void CTS_Encryption::finish(secure_vector<uint8_t>& buffer, size_t offset)
{
BOTAN_ASSERT(buffer.size() >= offset, "Offset is sane");
uint8_t* buf = buffer.data() + offset;
const size_t sz = buffer.size() - offset;
const size_t BS = block_size();
if(sz < BS + 1)
throw Encoding_Error(name() + ": insufficient data to encrypt");
if(sz % BS == 0)
{
update(buffer, offset);
// swap last two blocks
for(size_t i = 0; i != BS; ++i)
std::swap(buffer[buffer.size()-BS+i], buffer[buffer.size()-2*BS+i]);
}
else
{
const size_t full_blocks = ((sz / BS) - 1) * BS;
const size_t final_bytes = sz - full_blocks;
BOTAN_ASSERT(final_bytes > BS && final_bytes < 2*BS, "Left over size in expected range");
secure_vector<uint8_t> last(buf + full_blocks, buf + full_blocks + final_bytes);
buffer.resize(full_blocks + offset);
update(buffer, offset);
xor_buf(last.data(), state_ptr(), BS);
cipher().encrypt(last.data());
for(size_t i = 0; i != final_bytes - BS; ++i)
{
last[i] ^= last[i + BS];
last[i + BS] ^= last[i];
}
cipher().encrypt(last.data());
buffer += last;
}
}
size_t CBC_Decryption::output_length(size_t input_length) const
{
return input_length; // precise for CTS, worst case otherwise
}
size_t CBC_Decryption::minimum_final_size() const
{
return block_size();
}
size_t CBC_Decryption::process(uint8_t buf[], size_t sz)
{
BOTAN_STATE_CHECK(state().empty() == false);
const size_t BS = block_size();
BOTAN_ASSERT(sz % BS == 0, "Input is full blocks");
size_t blocks = sz / BS;
while(blocks)
{
const size_t to_proc = std::min(BS * blocks, m_tempbuf.size());
cipher().decrypt_n(buf, m_tempbuf.data(), to_proc / BS);
xor_buf(m_tempbuf.data(), state_ptr(), BS);
xor_buf(&m_tempbuf[BS], buf, to_proc - BS);
copy_mem(state_ptr(), buf + (to_proc - BS), BS);
copy_mem(buf, m_tempbuf.data(), to_proc);
buf += to_proc;
blocks -= to_proc / BS;
}
return sz;
}
void CBC_Decryption::finish(secure_vector<uint8_t>& buffer, size_t offset)
{
BOTAN_ASSERT(buffer.size() >= offset, "Offset is sane");
const size_t sz = buffer.size() - offset;
const size_t BS = 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
if(pad_bytes == 0 && padding().name() != "NoPadding")
{
throw Decoding_Error(name());
}
}
void CBC_Decryption::reset()
{
zeroise(state());
zeroise(m_tempbuf);
}
bool CTS_Decryption::valid_nonce_length(size_t n) const
{
return (n == block_size());
}
size_t CTS_Decryption::minimum_final_size() const
{
return block_size() + 1;
}
void CTS_Decryption::finish(secure_vector<uint8_t>& buffer, size_t offset)
{
BOTAN_ASSERT(buffer.size() >= offset, "Offset is sane");
const size_t sz = buffer.size() - offset;
uint8_t* buf = buffer.data() + offset;
const size_t BS = block_size();
if(sz < BS + 1)
throw Encoding_Error(name() + ": insufficient data to decrypt");
if(sz % BS == 0)
{
// swap last two blocks
for(size_t i = 0; i != BS; ++i)
std::swap(buffer[buffer.size()-BS+i], buffer[buffer.size()-2*BS+i]);
update(buffer, offset);
}
else
{
const size_t full_blocks = ((sz / BS) - 1) * BS;
const size_t final_bytes = sz - full_blocks;
BOTAN_ASSERT(final_bytes > BS && final_bytes < 2*BS, "Left over size in expected range");
secure_vector<uint8_t> last(buf + full_blocks, buf + full_blocks + final_bytes);
buffer.resize(full_blocks + offset);
update(buffer, offset);
cipher().decrypt(last.data());
xor_buf(last.data(), &last[BS], final_bytes - BS);
for(size_t i = 0; i != final_bytes - BS; ++i)
std::swap(last[i], last[i + BS]);
cipher().decrypt(last.data());
xor_buf(last.data(), state_ptr(), BS);
buffer += last;
}
}
}
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