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// cmac.cpp - originally written and placed in the public domain by Wei Dai
#include "pch.h"
#ifndef CRYPTOPP_IMPORTS
#include "cmac.h"
#include "misc.h"
ANONYMOUS_NAMESPACE_BEGIN
using CryptoPP::byte;
using CryptoPP::IsPowerOf2;
void MulU(byte *k, unsigned int len)
{
byte carry = 0;
for (int i=len-1; i>=1; i-=2)
{
byte carry2 = k[i] >> 7;
k[i] += k[i] + carry;
carry = k[i-1] >> 7;
k[i-1] += k[i-1] + carry2;
}
#ifndef CRYPTOPP_CMAC_WIDE_BLOCK_CIPHERS
CRYPTOPP_ASSERT(len == 16);
if (carry)
{
k[15] ^= 0x87;
return;
}
#else
CRYPTOPP_ASSERT(IsPowerOf2(len));
CRYPTOPP_ASSERT(len >= 8);
CRYPTOPP_ASSERT(len <= 128);
if (carry)
{
switch (len)
{
case 8:
k[7] ^= 0x1b;
break;
case 16:
k[15] ^= 0x87;
break;
case 32:
// https://crypto.stackexchange.com/q/9815/10496
// Polynomial x^256 + x^10 + x^5 + x^2 + 1
k[30] ^= 4;
k[31] ^= 0x25;
break;
case 64:
// https://crypto.stackexchange.com/q/9815/10496
// Polynomial x^512 + x^8 + x^5 + x^2 + 1
k[62] ^= 1;
k[63] ^= 0x25;
break;
case 128:
// https://crypto.stackexchange.com/q/9815/10496
// Polynomial x^1024 + x^19 + x^6 + x + 1
k[125] ^= 8;
k[126] ^= 0x00;
k[127] ^= 0x43;
break;
default:
CRYPTOPP_ASSERT(0);
}
}
#endif // CRYPTOPP_CMAC_WIDE_BLOCK_CIPHERS
}
ANONYMOUS_NAMESPACE_END
NAMESPACE_BEGIN(CryptoPP)
void CMAC_Base::UncheckedSetKey(const byte *key, unsigned int length, const NameValuePairs ¶ms)
{
BlockCipher &cipher = AccessCipher();
cipher.SetKey(key, length, params);
unsigned int blockSize = cipher.BlockSize();
m_reg.CleanNew(3*blockSize);
m_counter = 0;
cipher.ProcessBlock(m_reg, m_reg+blockSize);
MulU(m_reg+blockSize, blockSize);
std::memcpy(m_reg+2*blockSize, m_reg+blockSize, blockSize);
MulU(m_reg+2*blockSize, blockSize);
}
void CMAC_Base::Update(const byte *input, size_t length)
{
CRYPTOPP_ASSERT((input && length) || !(input || length));
if (!length)
return;
BlockCipher &cipher = AccessCipher();
unsigned int blockSize = cipher.BlockSize();
if (m_counter > 0)
{
const unsigned int len = UnsignedMin(blockSize - m_counter, length);
if (len)
{
xorbuf(m_reg+m_counter, input, len);
length -= len;
input += len;
m_counter += len;
}
if (m_counter == blockSize && length > 0)
{
cipher.ProcessBlock(m_reg);
m_counter = 0;
}
}
if (length > blockSize)
{
CRYPTOPP_ASSERT(m_counter == 0);
size_t leftOver = 1 + cipher.AdvancedProcessBlocks(m_reg, input, m_reg, length-1, BlockTransformation::BT_DontIncrementInOutPointers|BlockTransformation::BT_XorInput);
input += (length - leftOver);
length = leftOver;
}
if (length > 0)
{
CRYPTOPP_ASSERT(m_counter + length <= blockSize);
xorbuf(m_reg+m_counter, input, length);
m_counter += (unsigned int)length;
}
CRYPTOPP_ASSERT(m_counter > 0);
}
void CMAC_Base::TruncatedFinal(byte *mac, size_t size)
{
ThrowIfInvalidTruncatedSize(size);
BlockCipher &cipher = AccessCipher();
unsigned int blockSize = cipher.BlockSize();
if (m_counter < blockSize)
{
m_reg[m_counter] ^= 0x80;
cipher.AdvancedProcessBlocks(m_reg, m_reg+2*blockSize, m_reg, blockSize, BlockTransformation::BT_DontIncrementInOutPointers|BlockTransformation::BT_XorInput);
}
else
cipher.AdvancedProcessBlocks(m_reg, m_reg+blockSize, m_reg, blockSize, BlockTransformation::BT_DontIncrementInOutPointers|BlockTransformation::BT_XorInput);
// UBsan finding
if (mac)
std::memcpy(mac, m_reg, size);
m_counter = 0;
std::memset(m_reg, 0, blockSize);
}
NAMESPACE_END
#endif
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