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/*
* CMAC
* (C) 1999-2007,2014 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#include <botan/cmac.h>
#include <botan/exceptn.h>
#include <botan/internal/poly_dbl.h>
namespace Botan {
/*
* Perform CMAC's multiplication in GF(2^n)
*/
secure_vector<uint8_t> CMAC::poly_double(const secure_vector<uint8_t>& in)
{
secure_vector<uint8_t> out(in.size());
poly_double_n(out.data(), in.data(), out.size());
return out;
}
/*
* Update an CMAC Calculation
*/
void CMAC::add_data(const uint8_t input[], size_t length)
{
const size_t bs = output_length();
buffer_insert(m_buffer, m_position, input, length);
if(m_position + length > bs)
{
xor_buf(m_state, m_buffer, bs);
m_cipher->encrypt(m_state);
input += (bs - m_position);
length -= (bs - m_position);
while(length > bs)
{
xor_buf(m_state, input, bs);
m_cipher->encrypt(m_state);
input += bs;
length -= bs;
}
copy_mem(m_buffer.data(), input, length);
m_position = 0;
}
m_position += length;
}
/*
* Finalize an CMAC Calculation
*/
void CMAC::final_result(uint8_t mac[])
{
xor_buf(m_state, m_buffer, m_position);
if(m_position == output_length())
{
xor_buf(m_state, m_B, output_length());
}
else
{
m_state[m_position] ^= 0x80;
xor_buf(m_state, m_P, output_length());
}
m_cipher->encrypt(m_state);
copy_mem(mac, m_state.data(), output_length());
zeroise(m_state);
zeroise(m_buffer);
m_position = 0;
}
/*
* CMAC Key Schedule
*/
void CMAC::key_schedule(const uint8_t key[], size_t length)
{
clear();
m_cipher->set_key(key, length);
m_cipher->encrypt(m_B);
poly_double_n(m_B.data(), m_B.size());
poly_double_n(m_P.data(), m_B.data(), m_P.size());
}
/*
* Clear memory of sensitive data
*/
void CMAC::clear()
{
m_cipher->clear();
zeroise(m_state);
zeroise(m_buffer);
zeroise(m_B);
zeroise(m_P);
m_position = 0;
}
/*
* Return the name of this type
*/
std::string CMAC::name() const
{
return "CMAC(" + m_cipher->name() + ")";
}
/*
* Return a clone of this object
*/
MessageAuthenticationCode* CMAC::clone() const
{
return new CMAC(m_cipher->clone());
}
/*
* CMAC Constructor
*/
CMAC::CMAC(BlockCipher* cipher) :
m_cipher(cipher),
m_block_size(m_cipher->block_size())
{
if(poly_double_supported_size(m_block_size) == false)
{
throw Invalid_Argument("CMAC cannot use the " +
std::to_string(m_block_size * 8) +
" bit cipher " + m_cipher->name());
}
m_state.resize(output_length());
m_buffer.resize(output_length());
m_B.resize(output_length());
m_P.resize(output_length());
m_position = 0;
}
}