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/*
* Salsa20 / XSalsa20
* (C) 1999-2010,2014 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#include <botan/salsa20.h>
#include <botan/exceptn.h>
#include <botan/loadstor.h>
#include <botan/rotate.h>
namespace Botan {
#define SALSA20_QUARTER_ROUND(x1, x2, x3, x4) \
do { \
x2 ^= rotl<7>(x1 + x4); \
x3 ^= rotl<9>(x2 + x1); \
x4 ^= rotl<13>(x3 + x2); \
x1 ^= rotl<18>(x4 + x3); \
} while(0)
/*
* Generate HSalsa20 cipher stream (for XSalsa20 IV setup)
*/
//static
void Salsa20::hsalsa20(uint32_t output[8], const uint32_t input[16])
{
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 != 10; ++i)
{
SALSA20_QUARTER_ROUND(x00, x04, x08, x12);
SALSA20_QUARTER_ROUND(x05, x09, x13, x01);
SALSA20_QUARTER_ROUND(x10, x14, x02, x06);
SALSA20_QUARTER_ROUND(x15, x03, x07, x11);
SALSA20_QUARTER_ROUND(x00, x01, x02, x03);
SALSA20_QUARTER_ROUND(x05, x06, x07, x04);
SALSA20_QUARTER_ROUND(x10, x11, x08, x09);
SALSA20_QUARTER_ROUND(x15, x12, x13, x14);
}
output[0] = x00;
output[1] = x05;
output[2] = x10;
output[3] = x15;
output[4] = x06;
output[5] = x07;
output[6] = x08;
output[7] = x09;
}
/*
* Generate Salsa20 cipher stream
*/
//static
void Salsa20::salsa_core(uint8_t output[64], const uint32_t input[16], size_t rounds)
{
BOTAN_ASSERT_NOMSG(rounds % 2 == 0);
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)
{
SALSA20_QUARTER_ROUND(x00, x04, x08, x12);
SALSA20_QUARTER_ROUND(x05, x09, x13, x01);
SALSA20_QUARTER_ROUND(x10, x14, x02, x06);
SALSA20_QUARTER_ROUND(x15, x03, x07, x11);
SALSA20_QUARTER_ROUND(x00, x01, x02, x03);
SALSA20_QUARTER_ROUND(x05, x06, x07, x04);
SALSA20_QUARTER_ROUND(x10, x11, x08, x09);
SALSA20_QUARTER_ROUND(x15, x12, x13, x14);
}
store_le(x00 + input[ 0], output + 4 * 0);
store_le(x01 + input[ 1], output + 4 * 1);
store_le(x02 + input[ 2], output + 4 * 2);
store_le(x03 + input[ 3], output + 4 * 3);
store_le(x04 + input[ 4], output + 4 * 4);
store_le(x05 + input[ 5], output + 4 * 5);
store_le(x06 + input[ 6], output + 4 * 6);
store_le(x07 + input[ 7], output + 4 * 7);
store_le(x08 + input[ 8], output + 4 * 8);
store_le(x09 + input[ 9], output + 4 * 9);
store_le(x10 + input[10], output + 4 * 10);
store_le(x11 + input[11], output + 4 * 11);
store_le(x12 + input[12], output + 4 * 12);
store_le(x13 + input[13], output + 4 * 13);
store_le(x14 + input[14], output + 4 * 14);
store_le(x15 + input[15], output + 4 * 15);
}
#undef SALSA20_QUARTER_ROUND
/*
* Combine cipher stream with message
*/
void Salsa20::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);
salsa_core(m_buffer.data(), m_state.data(), 20);
++m_state[8];
m_state[9] += (m_state[8] == 0);
length -= available;
in += available;
out += available;
m_position = 0;
}
xor_buf(out, in, &m_buffer[m_position], length);
m_position += length;
}
void Salsa20::initialize_state()
{
static const uint32_t TAU[] =
{ 0x61707865, 0x3120646e, 0x79622d36, 0x6b206574 };
static const uint32_t SIGMA[] =
{ 0x61707865, 0x3320646e, 0x79622d32, 0x6b206574 };
m_state[1] = m_key[0];
m_state[2] = m_key[1];
m_state[3] = m_key[2];
m_state[4] = m_key[3];
if(m_key.size() == 4)
{
m_state[0] = TAU[0];
m_state[5] = TAU[1];
m_state[10] = TAU[2];
m_state[15] = TAU[3];
m_state[11] = m_key[0];
m_state[12] = m_key[1];
m_state[13] = m_key[2];
m_state[14] = m_key[3];
}
else
{
m_state[0] = SIGMA[0];
m_state[5] = SIGMA[1];
m_state[10] = SIGMA[2];
m_state[15] = SIGMA[3];
m_state[11] = m_key[4];
m_state[12] = m_key[5];
m_state[13] = m_key[6];
m_state[14] = m_key[7];
}
m_state[6] = 0;
m_state[7] = 0;
m_state[8] = 0;
m_state[9] = 0;
m_position = 0;
}
/*
* Salsa20 Key Schedule
*/
void Salsa20::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);
m_buffer.resize(64);
set_iv(nullptr, 0);
}
/*
* Set the Salsa IV
*/
void Salsa20::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)
{
// Salsa20 null IV
m_state[6] = 0;
m_state[7] = 0;
}
else if(length == 8)
{
// Salsa20
m_state[6] = load_le<uint32_t>(iv, 0);
m_state[7] = load_le<uint32_t>(iv, 1);
}
else
{
// XSalsa20
m_state[6] = load_le<uint32_t>(iv, 0);
m_state[7] = load_le<uint32_t>(iv, 1);
m_state[8] = load_le<uint32_t>(iv, 2);
m_state[9] = load_le<uint32_t>(iv, 3);
secure_vector<uint32_t> hsalsa(8);
hsalsa20(hsalsa.data(), m_state.data());
m_state[ 1] = hsalsa[0];
m_state[ 2] = hsalsa[1];
m_state[ 3] = hsalsa[2];
m_state[ 4] = hsalsa[3];
m_state[ 6] = load_le<uint32_t>(iv, 4);
m_state[ 7] = load_le<uint32_t>(iv, 5);
m_state[11] = hsalsa[4];
m_state[12] = hsalsa[5];
m_state[13] = hsalsa[6];
m_state[14] = hsalsa[7];
}
m_state[8] = 0;
m_state[9] = 0;
salsa_core(m_buffer.data(), m_state.data(), 20);
++m_state[8];
m_state[9] += (m_state[8] == 0);
m_position = 0;
}
bool Salsa20::valid_iv_length(size_t iv_len) const
{
return (iv_len == 0 || iv_len == 8 || iv_len == 24);
}
size_t Salsa20::default_iv_length() const
{
return 24;
}
Key_Length_Specification Salsa20::key_spec() const
{
return Key_Length_Specification(16, 32, 16);
}
StreamCipher* Salsa20::clone() const
{
return new Salsa20;
}
std::string Salsa20::name() const
{
return "Salsa20";
}
/*
* Clear memory of sensitive data
*/
void Salsa20::clear()
{
zap(m_key);
zap(m_state);
zap(m_buffer);
m_position = 0;
}
void Salsa20::seek(uint64_t offset)
{
verify_key_set(m_state.empty() == false);
// Find the block offset
const uint64_t counter = offset / 64;
uint8_t counter8[8];
store_le(counter, counter8);
m_state[8] = load_le<uint32_t>(counter8, 0);
m_state[9] += load_le<uint32_t>(counter8, 1);
salsa_core(m_buffer.data(), m_state.data(), 20);
++m_state[8];
m_state[9] += (m_state[8] == 0);
m_position = offset % 64;
}
}