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/*
* ChaCha
* (C) 2014,2018 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#include <botan/chacha.h>
#include <botan/exceptn.h>
#include <botan/loadstor.h>
#include <botan/rotate.h>
#include <botan/cpuid.h>
namespace Botan {
namespace {
#define CHACHA_QUARTER_ROUND(a, b, c, d) \
do { \
a += b; d ^= a; d = rotl<16>(d); \
c += d; b ^= c; b = rotl<12>(b); \
a += b; d ^= a; d = rotl<8>(d); \
c += d; b ^= c; b = rotl<7>(b); \
} while(0)
/*
* Generate HChaCha cipher stream (for XChaCha IV setup)
*/
void hchacha(uint32_t output[8], const uint32_t input[16], size_t rounds)
{
BOTAN_ASSERT(rounds % 2 == 0, "Valid rounds");
uint32_t x00 = input[ 0], x01 = input[ 1], x02 = input[ 2], x03 = input[ 3],
x04 = input[ 4], x05 = input[ 5], x06 = input[ 6], x07 = input[ 7],
x08 = input[ 8], x09 = input[ 9], x10 = input[10], x11 = input[11],
x12 = input[12], x13 = input[13], x14 = input[14], x15 = input[15];
for(size_t i = 0; i != rounds / 2; ++i)
{
CHACHA_QUARTER_ROUND(x00, x04, x08, x12);
CHACHA_QUARTER_ROUND(x01, x05, x09, x13);
CHACHA_QUARTER_ROUND(x02, x06, x10, x14);
CHACHA_QUARTER_ROUND(x03, x07, x11, x15);
CHACHA_QUARTER_ROUND(x00, x05, x10, x15);
CHACHA_QUARTER_ROUND(x01, x06, x11, x12);
CHACHA_QUARTER_ROUND(x02, x07, x08, x13);
CHACHA_QUARTER_ROUND(x03, x04, x09, x14);
}
output[0] = x00;
output[1] = x01;
output[2] = x02;
output[3] = x03;
output[4] = x12;
output[5] = x13;
output[6] = x14;
output[7] = x15;
}
}
ChaCha::ChaCha(size_t rounds) : m_rounds(rounds)
{
BOTAN_ARG_CHECK(m_rounds == 8 || m_rounds == 12 || m_rounds == 20,
"ChaCha only supports 8, 12 or 20 rounds");
}
std::string ChaCha::provider() const
{
#if defined(BOTAN_HAS_CHACHA_AVX2)
if(CPUID::has_avx2())
{
return "avx2";
}
#endif
#if defined(BOTAN_HAS_CHACHA_SIMD32)
if(CPUID::has_simd_32())
{
return "simd32";
}
#endif
return "base";
}
//static
void ChaCha::chacha_x8(uint8_t output[64*8], uint32_t input[16], size_t rounds)
{
BOTAN_ASSERT(rounds % 2 == 0, "Valid rounds");
#if defined(BOTAN_HAS_CHACHA_AVX2)
if(CPUID::has_avx2())
{
return ChaCha::chacha_avx2_x8(output, input, rounds);
}
#endif
#if defined(BOTAN_HAS_CHACHA_SIMD32)
if(CPUID::has_simd_32())
{
ChaCha::chacha_simd32_x4(output, input, rounds);
ChaCha::chacha_simd32_x4(output + 4*64, input, rounds);
return;
}
#endif
// TODO interleave rounds
for(size_t i = 0; i != 8; ++i)
{
uint32_t x00 = input[ 0], x01 = input[ 1], x02 = input[ 2], x03 = input[ 3],
x04 = input[ 4], x05 = input[ 5], x06 = input[ 6], x07 = input[ 7],
x08 = input[ 8], x09 = input[ 9], x10 = input[10], x11 = input[11],
x12 = input[12], x13 = input[13], x14 = input[14], x15 = input[15];
for(size_t r = 0; r != rounds / 2; ++r)
{
CHACHA_QUARTER_ROUND(x00, x04, x08, x12);
CHACHA_QUARTER_ROUND(x01, x05, x09, x13);
CHACHA_QUARTER_ROUND(x02, x06, x10, x14);
CHACHA_QUARTER_ROUND(x03, x07, x11, x15);
CHACHA_QUARTER_ROUND(x00, x05, x10, x15);
CHACHA_QUARTER_ROUND(x01, x06, x11, x12);
CHACHA_QUARTER_ROUND(x02, x07, x08, x13);
CHACHA_QUARTER_ROUND(x03, x04, x09, x14);
}
x00 += input[0];
x01 += input[1];
x02 += input[2];
x03 += input[3];
x04 += input[4];
x05 += input[5];
x06 += input[6];
x07 += input[7];
x08 += input[8];
x09 += input[9];
x10 += input[10];
x11 += input[11];
x12 += input[12];
x13 += input[13];
x14 += input[14];
x15 += input[15];
store_le(x00, output + 64 * i + 4 * 0);
store_le(x01, output + 64 * i + 4 * 1);
store_le(x02, output + 64 * i + 4 * 2);
store_le(x03, output + 64 * i + 4 * 3);
store_le(x04, output + 64 * i + 4 * 4);
store_le(x05, output + 64 * i + 4 * 5);
store_le(x06, output + 64 * i + 4 * 6);
store_le(x07, output + 64 * i + 4 * 7);
store_le(x08, output + 64 * i + 4 * 8);
store_le(x09, output + 64 * i + 4 * 9);
store_le(x10, output + 64 * i + 4 * 10);
store_le(x11, output + 64 * i + 4 * 11);
store_le(x12, output + 64 * i + 4 * 12);
store_le(x13, output + 64 * i + 4 * 13);
store_le(x14, output + 64 * i + 4 * 14);
store_le(x15, output + 64 * i + 4 * 15);
input[12]++;
input[13] += (input[12] == 0);
}
}
#undef CHACHA_QUARTER_ROUND
/*
* Combine cipher stream with message
*/
void ChaCha::cipher(const uint8_t in[], uint8_t out[], size_t length)
{
verify_key_set(m_state.empty() == false);
while(length >= m_buffer.size() - m_position)
{
const size_t available = m_buffer.size() - m_position;
xor_buf(out, in, &m_buffer[m_position], available);
chacha_x8(m_buffer.data(), m_state.data(), m_rounds);
length -= available;
in += available;
out += available;
m_position = 0;
}
xor_buf(out, in, &m_buffer[m_position], length);
m_position += length;
}
void ChaCha::write_keystream(uint8_t out[], size_t length)
{
verify_key_set(m_state.empty() == false);
while(length >= m_buffer.size() - m_position)
{
const size_t available = m_buffer.size() - m_position;
copy_mem(out, &m_buffer[m_position], available);
chacha_x8(m_buffer.data(), m_state.data(), m_rounds);
length -= available;
out += available;
m_position = 0;
}
copy_mem(out, &m_buffer[m_position], length);
m_position += length;
}
void ChaCha::initialize_state()
{
static const uint32_t TAU[] =
{ 0x61707865, 0x3120646e, 0x79622d36, 0x6b206574 };
static const uint32_t SIGMA[] =
{ 0x61707865, 0x3320646e, 0x79622d32, 0x6b206574 };
m_state[4] = m_key[0];
m_state[5] = m_key[1];
m_state[6] = m_key[2];
m_state[7] = m_key[3];
if(m_key.size() == 4)
{
m_state[0] = TAU[0];
m_state[1] = TAU[1];
m_state[2] = TAU[2];
m_state[3] = TAU[3];
m_state[8] = m_key[0];
m_state[9] = m_key[1];
m_state[10] = m_key[2];
m_state[11] = m_key[3];
}
else
{
m_state[0] = SIGMA[0];
m_state[1] = SIGMA[1];
m_state[2] = SIGMA[2];
m_state[3] = SIGMA[3];
m_state[8] = m_key[4];
m_state[9] = m_key[5];
m_state[10] = m_key[6];
m_state[11] = m_key[7];
}
m_state[12] = 0;
m_state[13] = 0;
m_state[14] = 0;
m_state[15] = 0;
m_position = 0;
}
/*
* ChaCha Key Schedule
*/
void ChaCha::key_schedule(const uint8_t key[], size_t length)
{
m_key.resize(length / 4);
load_le<uint32_t>(m_key.data(), key, m_key.size());
m_state.resize(16);
const size_t chacha_parallelism = 8; // chacha_x8
const size_t chacha_block = 64;
m_buffer.resize(chacha_parallelism * chacha_block);
set_iv(nullptr, 0);
}
size_t ChaCha::default_iv_length() const
{
return 24;
}
Key_Length_Specification ChaCha::key_spec() const
{
return Key_Length_Specification(16, 32, 16);
}
StreamCipher* ChaCha::clone() const
{
return new ChaCha(m_rounds);
}
bool ChaCha::valid_iv_length(size_t iv_len) const
{
return (iv_len == 0 || iv_len == 8 || iv_len == 12 || iv_len == 24);
}
void ChaCha::set_iv(const uint8_t iv[], size_t length)
{
verify_key_set(m_state.empty() == false);
if(!valid_iv_length(length))
throw Invalid_IV_Length(name(), length);
initialize_state();
if(length == 0)
{
// Treat zero length IV same as an all-zero IV
m_state[14] = 0;
m_state[15] = 0;
}
else if(length == 8)
{
m_state[14] = load_le<uint32_t>(iv, 0);
m_state[15] = load_le<uint32_t>(iv, 1);
}
else if(length == 12)
{
m_state[13] = load_le<uint32_t>(iv, 0);
m_state[14] = load_le<uint32_t>(iv, 1);
m_state[15] = load_le<uint32_t>(iv, 2);
}
else if(length == 24)
{
m_state[12] = load_le<uint32_t>(iv, 0);
m_state[13] = load_le<uint32_t>(iv, 1);
m_state[14] = load_le<uint32_t>(iv, 2);
m_state[15] = load_le<uint32_t>(iv, 3);
secure_vector<uint32_t> hc(8);
hchacha(hc.data(), m_state.data(), m_rounds);
m_state[ 4] = hc[0];
m_state[ 5] = hc[1];
m_state[ 6] = hc[2];
m_state[ 7] = hc[3];
m_state[ 8] = hc[4];
m_state[ 9] = hc[5];
m_state[10] = hc[6];
m_state[11] = hc[7];
m_state[12] = 0;
m_state[13] = 0;
m_state[14] = load_le<uint32_t>(iv, 4);
m_state[15] = load_le<uint32_t>(iv, 5);
}
chacha_x8(m_buffer.data(), m_state.data(), m_rounds);
m_position = 0;
}
void ChaCha::clear()
{
zap(m_key);
zap(m_state);
zap(m_buffer);
m_position = 0;
}
std::string ChaCha::name() const
{
return "ChaCha(" + std::to_string(m_rounds) + ")";
}
void ChaCha::seek(uint64_t offset)
{
verify_key_set(m_state.empty() == false);
// Find the block offset
const uint64_t counter = offset / 64;
uint8_t out[8];
store_le(counter, out);
m_state[12] = load_le<uint32_t>(out, 0);
m_state[13] += load_le<uint32_t>(out, 1);
chacha_x8(m_buffer.data(), m_state.data(), m_rounds);
m_position = offset % 64;
}
}