transmission/libtransmission/peer-mse.cc

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// This file Copyright © 2007-2023 Mnemosyne LLC.
// It may be used under GPLv2 (SPDX: GPL-2.0-only), GPLv3 (SPDX: GPL-3.0-only),
// or any future license endorsed by Mnemosyne LLC.
// License text can be found in the licenses/ folder.
#include <array>
#include <memory>
#include <math/wide_integer/uintwide_t.h>
#include "libtransmission/transmission.h"
#include "libtransmission/crypto-utils.h" // tr_sha1
#include "libtransmission/peer-mse.h"
#include "libtransmission/tr-arc4.h"
using namespace std::literals;
namespace
{
namespace wi
{
using key_t = math::wide_integer::uintwide_t<
tr_message_stream_encryption::DH::KeySize * std::numeric_limits<unsigned char>::digits>;
using private_key_t = math::wide_integer::uintwide_t<
tr_message_stream_encryption::DH::PrivateKeySize * std::numeric_limits<unsigned char>::digits>;
template<typename UIntWide>
auto import_bits(std::array<std::byte, UIntWide::my_width2 / std::numeric_limits<uint8_t>::digits> const& bigend_bin)
{
auto ret = UIntWide{};
static_assert(sizeof(UIntWide) == sizeof(bigend_bin));
for (auto const walk : bigend_bin)
{
ret <<= 8;
ret += static_cast<uint8_t>(walk);
}
return ret;
}
template<typename UIntWide>
auto export_bits(UIntWide i)
{
auto ret = std::array<std::byte, UIntWide::my_width2 / std::numeric_limits<uint8_t>::digits>{};
for (auto walk = std::rbegin(ret), end = std::rend(ret); walk != end; ++walk)
{
*walk = std::byte(static_cast<uint8_t>(i & 0xFF));
i >>= 8;
}
return ret;
}
// NOLINTBEGIN(readability-identifier-naming)
auto WIDE_INTEGER_CONSTEXPR const generator = wi::key_t{ "2" };
auto WIDE_INTEGER_CONSTEXPR const prime = wi::key_t{
"0xFFFFFFFFFFFFFFFFC90FDAA22168C234C4C6628B80DC1CD129024E088A67CC74020BBEA63B139B22514A08798E3404DDEF9519B3CD3A431B302B0A6DF25F14374FE1356D6D51C245E485B576625E7EC6F44C42E9A63A36210000000000090563"
};
// NOLINTEND(readability-identifier-naming)
} // namespace wi
} // namespace
namespace tr_message_stream_encryption
{
// --- DH
[[nodiscard]] DH::private_key_bigend_t DH::randomPrivateKey() noexcept
{
return tr_rand_obj<DH::private_key_bigend_t>();
}
[[nodiscard]] auto generatePublicKey(DH::private_key_bigend_t const& private_key) noexcept
{
auto const private_key_wi = wi::import_bits<wi::private_key_t>(private_key);
auto const public_key_wi = math::wide_integer::powm(wi::generator, private_key_wi, wi::prime);
return wi::export_bits(public_key_wi);
}
DH::key_bigend_t DH::publicKey() noexcept
{
if (public_key_ == key_bigend_t{})
{
public_key_ = generatePublicKey(private_key_);
}
return public_key_;
}
void DH::setPeerPublicKey(key_bigend_t const& peer_public_key)
{
auto const secret = math::wide_integer::powm(
wi::import_bits<wi::key_t>(peer_public_key),
wi::import_bits<wi::private_key_t>(private_key_),
wi::prime);
secret_ = wi::export_bits(secret);
}
// --- Filter
void Filter::decryptInit(bool is_incoming, DH const& dh, tr_sha1_digest_t const& info_hash)
{
auto const key = is_incoming ? "keyA"sv : "keyB"sv;
auto const buf = tr_sha1::digest(key, dh.secret(), info_hash);
dec_active_ = true;
dec_key_.init(std::data(buf), std::size(buf));
dec_key_.discard(1024);
}
void Filter::encryptInit(bool is_incoming, DH const& dh, tr_sha1_digest_t const& info_hash)
{
auto const key = is_incoming ? "keyB"sv : "keyA"sv;
auto const buf = tr_sha1::digest(key, dh.secret(), info_hash);
enc_active_ = true;
enc_key_.init(std::data(buf), std::size(buf));
enc_key_.discard(1024);
}
} // namespace tr_message_stream_encryption