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