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transmission/libtransmission/handshake.cc

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// This file Copyright © 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 <algorithm>
#include <array>
#include <cerrno> // ECONNREFUSED, ETIMEDOUT
#include <cstddef>
#include <cstdint>
#include <string_view>
#include <tuple>
#include <utility>
#include <fmt/core.h>
#include "libtransmission/transmission.h"
#include "libtransmission/bitfield.h"
#include "libtransmission/clients.h"
#include "libtransmission/crypto-utils.h"
#include "libtransmission/error.h"
#include "libtransmission/handshake.h"
#include "libtransmission/log.h"
#include "libtransmission/peer-io.h"
#include "libtransmission/peer-mse.h" // tr_message_stream_encryption::DH
#include "libtransmission/timer.h"
#include "libtransmission/tr-assert.h"
#include "libtransmission/tr-buffer.h"
#include "libtransmission/tr-macros.h" // tr_peer_id_t
#define tr_logAddTraceHand(handshake, msg) \
tr_logAddTrace(msg, fmt::format("handshake {}", (handshake)->peer_io_->display_name()))
using namespace std::literals;
using key_bigend_t = tr_message_stream_encryption::DH::key_bigend_t;
// --- Outgoing Connections
// 1 A->B: our public key (Ya) and some padding (PadA)
void tr_handshake::send_ya(tr_peerIo* io)
{
tr_logAddTraceHand(this, "sending MSE handshake (Ya)");
send_public_key_and_pad<PadaMaxlen>(io);
set_state(tr_handshake::State::AwaitingYb);
}
ReadState tr_handshake::read_yb(tr_peerIo* peer_io)
{
if (peer_io->read_buffer_size() < std::size(HandshakeName))
{
return ReadState::Later;
}
// Jump to plain handshake
if (peer_io->read_buffer_starts_with(HandshakeName))
{
tr_logAddTraceHand(this, "in read_yb... got a plain incoming handshake");
set_state(tr_handshake::State::AwaitingHandshake);
return ReadState::Now;
}
auto peer_public_key = key_bigend_t{};
tr_logAddTraceHand(
this,
fmt::format("in read_yb... need {}, have {}", std::size(peer_public_key), peer_io->read_buffer_size()));
if (peer_io->read_buffer_size() < std::size(peer_public_key))
{
return ReadState::Later;
}
have_read_anything_from_peer_ = true;
// get the peer's public key
peer_io->read_bytes(std::data(peer_public_key), std::size(peer_public_key));
get_dh().setPeerPublicKey(peer_public_key);
/* now send these: HASH('req1', S), HASH('req2', SKEY) xor HASH('req3', S),
* ENCRYPT(VC, crypto_provide, len(PadC), PadC, len(IA)), ENCRYPT(IA) */
static auto constexpr BufSize = std::tuple_size_v<tr_sha1_digest_t> * 2 + std::size(VC) + sizeof(crypto_provide_) +
sizeof(pad_c_len_) + sizeof(ia_len_) + HandshakeSize;
auto outbuf = libtransmission::StackBuffer<BufSize, std::byte>{};
/* HASH('req1', S) */
outbuf.add(tr_sha1::digest("req1"sv, get_dh().secret()));
auto const& info_hash = peer_io->torrent_hash();
TR_ASSERT_MSG(info_hash != tr_sha1_digest_t{}, "readYb requires an info_hash");
/* HASH('req2', SKEY) xor HASH('req3', S) */
{
auto const req2 = tr_sha1::digest("req2"sv, info_hash);
auto const req3 = tr_sha1::digest("req3"sv, get_dh().secret());
auto [x_or, n_x_or] = outbuf.reserve_space(std::tuple_size_v<tr_sha1_digest_t>);
for (size_t i = 0; i < n_x_or; ++i)
{
x_or[i] = req2[i] ^ req3[i];
}
outbuf.commit_space(n_x_or);
}
/* ENCRYPT(VC, crypto_provide, len(PadC), PadC
* PadC is reserved for future extensions to the handshake...
* standard practice at this time is for it to be zero-length */
crypto_provide_ = crypto_provide();
peer_io->write(outbuf, false);
peer_io->encrypt_init(peer_io->is_incoming(), get_dh(), info_hash);
outbuf.add(VC);
outbuf.add_uint32(crypto_provide_);
outbuf.add_uint16(0);
/* ENCRYPT len(IA)), ENCRYPT(IA) */
outbuf.add_uint16(HandshakeSize);
if (build_handshake_message(peer_io, outbuf))
{
have_sent_bittorrent_handshake_ = true;
}
else
{
return done(false);
}
/* send it */
set_state(State::AwaitingVc);
peer_io->write(outbuf, false);
return ReadState::Now;
}
// MSE spec: "Since the length of [PadB is] unknown,
// A will be able to resynchronize on ENCRYPT(VC)"
ReadState tr_handshake::read_vc(tr_peerIo* peer_io)
{
auto const info_hash = peer_io->torrent_hash();
TR_ASSERT_MSG(info_hash != tr_sha1_digest_t{}, "read_vc requires an info_hash");
// We need to find the end of PadB by looking for `ENCRYPT(VC)`,
// so calculate and cache the value of `ENCRYPT(VC)`.
if (!encrypted_vc_)
{
auto filter = tr_message_stream_encryption::Filter{};
filter.encrypt_init(true, get_dh(), info_hash);
encrypted_vc_.emplace();
filter.encrypt(std::data(VC), std::size(VC), std::data(*encrypted_vc_));
}
for (; pad_b_recv_len_ <= PadbMaxlen; ++pad_b_recv_len_)
{
static auto constexpr Needlen = std::size(VC);
if (peer_io->read_buffer_size() < Needlen)
{
tr_logAddTraceHand(
this,
fmt::format("in read_vc... need {}, read {}, have {}", Needlen, pad_b_recv_len_, peer_io->read_buffer_size()));
return ReadState::Later;
}
if (peer_io->read_buffer_starts_with(*encrypted_vc_))
{
tr_logAddTraceHand(this, "found ENCRYPT(VC)!");
// We already know it's a match; now we just need to
// consume it from the read buffer.
peer_io->decrypt_init(peer_io->is_incoming(), get_dh(), info_hash);
peer_io->read_buffer_discard(Needlen);
set_state(tr_handshake::State::AwaitingCryptoSelect);
return ReadState::Now;
}
peer_io->read_buffer_discard(1U);
}
tr_logAddTraceHand(this, "couldn't find ENCRYPT(VC)");
return done(false);
}
ReadState tr_handshake::read_crypto_select(tr_peerIo* peer_io)
{
if (static auto constexpr NeedLen = sizeof(crypto_select_) + sizeof(pad_d_len_); peer_io->read_buffer_size() < NeedLen)
{
return ReadState::Later;
}
peer_io->read_uint32(&crypto_select_);
tr_logAddTraceHand(this, fmt::format("crypto select is {}", crypto_select_));
if ((crypto_select_ & crypto_provide_) == 0U)
{
tr_logAddTraceHand(this, "peer selected an encryption option we didn't offer");
return done(false);
}
peer_io->read_uint16(&pad_d_len_);
tr_logAddTraceHand(this, fmt::format("len(PadD) is {}", pad_d_len_));
if (pad_d_len_ > PaddMaxlen)
{
tr_logAddTraceHand(this, "MSE handshake: len(PadD) is too long");
return done(false);
}
set_state(tr_handshake::State::AwaitingPadD);
return ReadState::Now;
}
ReadState tr_handshake::read_pad_d(tr_peerIo* peer_io)
{
tr_logAddTraceHand(this, fmt::format("PadD: need {}, got {}", pad_d_len_, peer_io->read_buffer_size()));
if (peer_io->read_buffer_size() < pad_d_len_)
{
return ReadState::Later;
}
peer_io->read_buffer_discard(pad_d_len_);
/* maybe de-encrypt our connection */
if (crypto_select_ == CryptoProvidePlaintext)
{
peer_io->encrypt_disable();
peer_io->decrypt_disable();
}
set_state(tr_handshake::State::AwaitingHandshake);
return ReadState::Now;
}
// --- Incoming and Outgoing Connections
ReadState tr_handshake::read_handshake(tr_peerIo* peer_io)
{
static auto constexpr Needlen = IncomingHandshakeLen;
tr_logAddTraceHand(this, fmt::format("read_handshake: need {}, got {}", Needlen, peer_io->read_buffer_size()));
if (peer_io->read_buffer_size() < Needlen)
{
return ReadState::Later;
}
if (ia_len_ > 0U)
{
// do nothing, the check below won't work correctly
}
else if (peer_io->read_buffer_starts_with(HandshakeName)) // unencrypted
{
if (encryption_mode_ == TR_ENCRYPTION_REQUIRED)
{
tr_logAddTraceHand(this, "peer is unencrypted, and we're disallowing that");
return done(false);
}
if (crypto_select_ == CryptoProvideRC4)
{
tr_logAddTraceHand(this, "peer is unencrypted, and that does not agree with our handshake");
return done(false);
}
}
else if (crypto_select_ == CryptoProvidePlaintext) // encrypted
{
tr_logAddTraceHand(this, "peer is encrypted, and that does not agree with our handshake");
return done(false);
}
have_read_anything_from_peer_ = true;
auto name = decltype(HandshakeName){};
peer_io->read_bytes(std::data(name), std::size(name));
if (name != HandshakeName)
{
tr_logAddTraceHand(this, "handshake prefix not correct");
return done(false);
}
// reserved bytes / flags
auto reserved = std::array<uint8_t, HandshakeFlagsBytes>{};
auto flags = tr_bitfield{ HandshakeFlagsBits };
peer_io->read_bytes(std::data(reserved), std::size(reserved));
flags.set_raw(std::data(reserved), std::size(reserved));
peer_io->set_supports_dht(flags.test(DhtFlag));
peer_io->set_supports_ltep(flags.test(LtepFlag));
peer_io->set_supports_fext(flags.test(FextFlag));
/* torrent hash */
auto hash = tr_sha1_digest_t{};
peer_io->read_bytes(std::data(hash), std::size(hash));
if (is_incoming() && peer_io->torrent_hash() == tr_sha1_digest_t{}) // incoming plain handshake
{
if (!mediator_->torrent(hash))
{
tr_logAddTraceHand(this, "peer is trying to connect to us for a torrent we don't have.");
return done(false);
}
peer_io->set_torrent_hash(hash);
}
else // outgoing, or incoming MSE handshake
{
if (peer_io->torrent_hash() != hash)
{
tr_logAddTraceHand(this, "peer returned the wrong hash. wtf?");
return done(false);
}
}
// If it's an incoming message, we need to send a response handshake
if (!have_sent_bittorrent_handshake_)
{
tr_logAddTraceHand(this, "sending handshake in reply");
if (!send_handshake(peer_io))
{
return done(false);
}
}
set_state(State::AwaitingPeerId);
return ReadState::Now;
}
ReadState tr_handshake::read_peer_id(tr_peerIo* peer_io)
{
// read the peer_id
auto peer_id = tr_peer_id_t{};
static auto constexpr Needlen = std::size(peer_id);
tr_logAddTraceHand(this, fmt::format("read_peer_id: need {}, got {}", Needlen, peer_io->read_buffer_size()));
if (peer_io->read_buffer_size() < Needlen)
{
return ReadState::Later;
}
peer_io->read_bytes(std::data(peer_id), Needlen);
set_peer_id(peer_id);
auto client = std::array<char, 128>{};
tr_clientForId(std::data(client), std::size(client), peer_id);
tr_logAddTraceHand(this, fmt::format("peer-id is '{}' ... isIncoming is {}", std::data(client), is_incoming()));
// if we've somehow connected to ourselves, don't keep the connection
auto const info_hash = peer_io_->torrent_hash();
auto const info = mediator_->torrent(info_hash);
auto const connected_to_self = info && info->client_peer_id == peer_id;
return done(!connected_to_self);
}
// --- Incoming Connections
ReadState tr_handshake::read_ya(tr_peerIo* peer_io)
{
if (peer_io->read_buffer_size() < std::size(HandshakeName))
{
return ReadState::Later;
}
// Jump to plain handshake
if (peer_io->read_buffer_starts_with(HandshakeName))
{
tr_logAddTraceHand(this, "in read_ya... got a plain incoming handshake");
set_state(tr_handshake::State::AwaitingHandshake);
return ReadState::Now;
}
auto peer_public_key = key_bigend_t{};
tr_logAddTraceHand(
this,
fmt::format("in read_ya... need {}, have {}", std::size(peer_public_key), peer_io->read_buffer_size()));
if (peer_io->read_buffer_size() < std::size(peer_public_key))
{
return ReadState::Later;
}
have_read_anything_from_peer_ = true;
/* read the incoming peer's public key */
peer_io->read_bytes(std::data(peer_public_key), std::size(peer_public_key));
get_dh().setPeerPublicKey(peer_public_key);
// send our public key to the peer
tr_logAddTraceHand(this, "sending B->A: Diffie Hellman Yb, PadB");
send_public_key_and_pad<PadbMaxlen>(peer_io);
set_state(State::AwaitingPadA);
return ReadState::Now;
}
ReadState tr_handshake::read_pad_a(tr_peerIo* peer_io)
{
// find the end of PadA by looking for HASH('req1', S)
auto const needle = tr_sha1::digest("req1"sv, get_dh().secret());
for (; pad_a_recv_len_ <= PadaMaxlen; ++pad_a_recv_len_)
{
static auto constexpr Needlen = std::size(needle);
if (peer_io->read_buffer_size() < Needlen)
{
tr_logAddTraceHand(
this,
fmt::format(
"in read_pad_a... need {}, read {}, have {}",
Needlen,
pad_a_recv_len_,
peer_io->read_buffer_size()));
return ReadState::Later;
}
if (peer_io->read_buffer_starts_with(needle))
{
tr_logAddTraceHand(this, "found HASH('req1', S)!");
peer_io->read_buffer_discard(Needlen);
set_state(State::AwaitingCryptoProvide);
return ReadState::Now;
}
peer_io->read_buffer_discard(1U);
}
tr_logAddTraceHand(this, "couldn't find HASH('req1', S)");
return done(false);
}
ReadState tr_handshake::read_crypto_provide(tr_peerIo* peer_io)
{
/* HASH('req2', SKEY) xor HASH('req3', S), ENCRYPT(VC, crypto_provide, len(PadC)) */
auto x_or = tr_sha1_digest_t{};
static auto constexpr Needlen = std::size(x_or) + /* HASH('req2', SKEY) xor HASH('req3', S) */
std::size(VC) + sizeof(crypto_provide_) + sizeof(pad_c_len_);
if (peer_io->read_buffer_size() < Needlen)
{
return ReadState::Later;
}
/* This next piece is HASH('req2', SKEY) xor HASH('req3', S) ...
* we can get the first half of that (the obfuscatedTorrentHash)
* by building the latter and xor'ing it with what the peer sent us */
tr_logAddTraceHand(this, "reading obfuscated torrent hash...");
peer_io->read_bytes(std::data(x_or), std::size(x_or));
auto obfuscated_hash = tr_sha1_digest_t{};
auto const req3 = tr_sha1::digest("req3"sv, get_dh().secret());
for (size_t i = 0; i < std::size(obfuscated_hash); ++i)
{
obfuscated_hash[i] = x_or[i] ^ req3[i];
}
if (auto const info = mediator_->torrent_from_obfuscated(obfuscated_hash); info)
{
tr_logAddTraceHand(this, fmt::format("got INCOMING connection's MSE handshake for torrent [{}]", info->id));
peer_io->set_torrent_hash(info->info_hash);
}
else
{
tr_logAddTraceHand(this, "can't find that torrent...");
return done(false);
}
/* next part: ENCRYPT(VC, crypto_provide, len(PadC), */
auto const& info_hash = peer_io->torrent_hash();
TR_ASSERT_MSG(info_hash != tr_sha1_digest_t{}, "read_crypto_provide requires an info_hash");
peer_io->decrypt_init(peer_io->is_incoming(), get_dh(), info_hash);
auto vc_in = vc_t{};
peer_io->read_bytes(std::data(vc_in), std::size(vc_in));
if (vc_in != VC)
{
tr_logAddTraceHand(this, "peer's VC is not all 0");
return done(false);
}
peer_io->read_uint32(&crypto_provide_);
tr_logAddTraceHand(this, fmt::format("crypto_provide is {}", crypto_provide_));
peer_io->read_uint16(&pad_c_len_);
tr_logAddTraceHand(this, fmt::format("len(PadC) is {}", pad_c_len_));
if (pad_c_len_ > PadcMaxlen)
{
tr_logAddTraceHand(this, "peer's PadC is too big");
return done(false);
}
set_state(State::AwaitingPadC);
return ReadState::Now;
}
ReadState tr_handshake::read_pad_c(tr_peerIo* peer_io)
{
if (auto const needlen = pad_c_len_ + sizeof(ia_len_); peer_io->read_buffer_size() < needlen)
{
return ReadState::Later;
}
// read the throwaway padc
peer_io->read_buffer_discard(pad_c_len_);
/* read ia_len */
peer_io->read_uint16(&ia_len_);
tr_logAddTraceHand(this, fmt::format("len(IA) is {}", ia_len_));
set_state(State::AwaitingIa);
return ReadState::Now;
}
ReadState tr_handshake::read_ia(tr_peerIo* peer_io)
{
size_t const needlen = ia_len_;
tr_logAddTraceHand(this, fmt::format("reading IA... have {}, need {}", peer_io->read_buffer_size(), needlen));
if (peer_io->read_buffer_size() < needlen)
{
return ReadState::Later;
}
// B->A: ENCRYPT(VC, crypto_select, len(padD), padD), ENCRYPT2(Payload Stream)
auto const& info_hash = peer_io->torrent_hash();
TR_ASSERT_MSG(info_hash != tr_sha1_digest_t{}, "read_ia requires an info_hash");
static auto constexpr BufSize = std::size(VC) + sizeof(crypto_select_) + sizeof(pad_d_len_) + HandshakeSize;
auto outbuf = libtransmission::StackBuffer<BufSize, std::byte>{};
peer_io->encrypt_init(peer_io->is_incoming(), get_dh(), info_hash);
// send VC
tr_logAddTraceHand(this, "sending vc");
outbuf.add(VC);
/* send crypto_select */
crypto_select_ = get_crypto_select(encryption_mode_, crypto_provide_);
if (crypto_select_ != 0U)
{
tr_logAddTraceHand(this, fmt::format("selecting crypto mode '{}'", crypto_select_));
outbuf.add_uint32(crypto_select_);
}
else
{
tr_logAddTraceHand(this, "peer didn't offer an encryption mode we like.");
return done(false);
}
tr_logAddTraceHand(this, "sending pad d");
/* ENCRYPT(VC, crypto_select, len(PadD), PadD
* PadD is reserved for future extensions to the handshake...
* standard practice at this time is for it to be zero-length */
outbuf.add_uint16(0U);
// send it
peer_io->write(outbuf, false);
/* maybe de-encrypt our connection */
if (crypto_select_ == CryptoProvidePlaintext)
{
TR_ASSERT(std::empty(outbuf));
// All future communications will use ENCRYPT2()
peer_io->encrypt_disable();
peer_io->decrypt_disable(ia_len_);
}
/* now await the handshake */
set_state(State::AwaitingHandshake);
return ReadState::Now;
}
// ---
ReadState tr_handshake::can_read(tr_peerIo* peer_io, void* vhandshake, size_t* piece)
{
auto* handshake = static_cast<tr_handshake*>(vhandshake);
/* no piece data in handshake */
*piece = 0;
tr_logAddTraceHand(handshake, fmt::format("handling can_read; state is [{}]", handshake->state_string()));
auto ret = ReadState::Now;
while (ret == ReadState::Now)
{
switch (handshake->state())
{
case State::AwaitingHandshake:
ret = handshake->read_handshake(peer_io);
break;
case State::AwaitingPeerId:
ret = handshake->read_peer_id(peer_io);
break;
case State::AwaitingYa:
ret = handshake->read_ya(peer_io);
break;
case State::AwaitingPadA:
ret = handshake->read_pad_a(peer_io);
break;
case State::AwaitingCryptoProvide:
ret = handshake->read_crypto_provide(peer_io);
break;
case State::AwaitingPadC:
ret = handshake->read_pad_c(peer_io);
break;
case State::AwaitingIa:
ret = handshake->read_ia(peer_io);
break;
case State::AwaitingYb:
ret = handshake->read_yb(peer_io);
break;
case State::AwaitingVc:
ret = handshake->read_vc(peer_io);
break;
case State::AwaitingCryptoSelect:
ret = handshake->read_crypto_select(peer_io);
break;
case State::AwaitingPadD:
ret = handshake->read_pad_d(peer_io);
break;
default:
TR_ASSERT_MSG(false, fmt::format("unhandled handshake state {:d}", static_cast<int>(handshake->state())));
return ReadState::Err;
}
}
return ret;
}
void tr_handshake::on_error(tr_peerIo* io, tr_error const& error, void* vhandshake)
{
auto* handshake = static_cast<tr_handshake*>(vhandshake);
auto const retry = [&]()
{
handshake->send_handshake(io);
handshake->set_state(State::AwaitingHandshake);
};
auto const fail = [&]()
{
tr_logAddTraceHand(handshake, fmt::format("handshake socket err: {:s} ({:d})", error.message(), error.code()));
handshake->done(false);
};
if (io->is_utp() && !io->is_incoming() && handshake->is_state(State::AwaitingYb))
{
// the peer probably doesn't speak µTP.
auto const info_hash = io->torrent_hash();
auto const info = handshake->mediator_->torrent(info_hash);
/* Don't mark a peer as non-µTP unless it's really a connect failure. */
if ((error.code() == ETIMEDOUT || error.code() == ECONNREFUSED) && info)
{
handshake->mediator_->set_utp_failed(info_hash, io->socket_address());
}
if (handshake->mediator_->allows_tcp() && io->reconnect())
{
retry();
return;
}
fail();
return;
}
/* if the error happened while we were sending a public key, we might
* have encountered a peer that doesn't do encryption... reconnect and
* try a plaintext handshake */
if ((handshake->is_state(State::AwaitingYb) || handshake->is_state(State::AwaitingVc)) &&
handshake->encryption_mode_ != TR_ENCRYPTION_REQUIRED && handshake->mediator_->allows_tcp() && io->reconnect())
{
tr_logAddTraceHand(handshake, "handshake failed, trying plaintext...");
retry();
return;
}
fail();
}
// ---
bool tr_handshake::build_handshake_message(tr_peerIo* io, libtransmission::BufferWriter<std::byte>& buf) const
{
auto const& info_hash = io->torrent_hash();
TR_ASSERT_MSG(info_hash != tr_sha1_digest_t{}, "build_handshake_message requires an info_hash");
auto const info = mediator_->torrent(info_hash);
if (!info)
{
return false;
}
auto flags = tr_bitfield{ HandshakeFlagsBits };
flags.set(LtepFlag);
flags.set(FextFlag);
if (mediator_->allows_dht())
{
flags.set(DhtFlag);
}
auto const flag_bytes = flags.raw();
buf.add(HandshakeName);
buf.add(flag_bytes);
buf.add(info_hash);
buf.add(info->client_peer_id);
return true;
}
bool tr_handshake::send_handshake(tr_peerIo* io)
{
auto msg = libtransmission::StackBuffer<HandshakeSize, std::byte>{};
if (!build_handshake_message(io, msg))
{
return false;
}
TR_ASSERT(std::size(msg) == HandshakeSize);
io->write(msg, false);
have_sent_bittorrent_handshake_ = true;
return true;
}
uint32_t tr_handshake::crypto_provide() const noexcept
{
auto provide = uint32_t{};
switch (encryption_mode_)
{
case TR_ENCRYPTION_REQUIRED:
case TR_ENCRYPTION_PREFERRED:
provide |= CryptoProvideRC4;
break;
case TR_CLEAR_PREFERRED:
provide |= CryptoProvideRC4 | CryptoProvidePlaintext;
break;
}
return provide;
}
[[nodiscard]] uint32_t tr_handshake::get_crypto_select(tr_encryption_mode encryption_mode, uint32_t crypto_provide) noexcept
{
auto choices = std::array<uint32_t, 2>{};
int n_choices = 0;
switch (encryption_mode)
{
case TR_ENCRYPTION_REQUIRED:
choices[n_choices++] = CryptoProvideRC4;
break;
case TR_ENCRYPTION_PREFERRED:
choices[n_choices++] = CryptoProvideRC4;
choices[n_choices++] = CryptoProvidePlaintext;
break;
case TR_CLEAR_PREFERRED:
choices[n_choices++] = CryptoProvidePlaintext;
choices[n_choices++] = CryptoProvideRC4;
break;
}
for (auto const& choice : choices)
{
if ((crypto_provide & choice) != 0)
{
return choice;
}
}
return 0;
}
bool tr_handshake::fire_done(bool is_connected)
{
maybe_recycle_dh();
if (!on_done_)
{
return false;
}
// handshake could get destroyed inside on_done,
// so handle all our housekeeping *before* calling it
auto cb = DoneFunc{};
std::swap(cb, on_done_);
return (cb)(Result{ peer_io_, peer_id_, have_read_anything_from_peer_, is_connected });
}
std::string_view tr_handshake::state_string(State state) noexcept
{
switch (state)
{
case State::AwaitingHandshake:
return "awaiting handshake";
case State::AwaitingPeerId:
return "awaiting peer id";
case State::AwaitingYa:
return "awaiting ya";
case State::AwaitingPadA:
return "awaiting pad a";
case State::AwaitingCryptoProvide:
return "awaiting crypto provide";
case State::AwaitingPadC:
return "awaiting pad c";
case State::AwaitingIa:
return "awaiting ia";
// outgoing
case State::AwaitingYb:
return "awaiting yb";
case State::AwaitingVc:
return "awaiting vc";
case State::AwaitingCryptoSelect:
return "awaiting crypto select";
case State::AwaitingPadD:
return "awaiting pad d";
}
return "unknown state";
}
tr_handshake::tr_handshake(Mediator* mediator, std::shared_ptr<tr_peerIo> peer_io, tr_encryption_mode mode, DoneFunc on_done)
: on_done_{ std::move(on_done) }
, peer_io_{ std::move(peer_io) }
, timeout_timer_{ mediator->timer_maker().create([this]() { fire_done(false); }) }
, mediator_{ mediator }
, encryption_mode_{ mode }
{
timeout_timer_->start_single_shot(HandshakeTimeoutSec);
peer_io_->set_callbacks(&tr_handshake::can_read, nullptr, &tr_handshake::on_error, this);
if (is_incoming())
{
set_state(State::AwaitingYa);
}
else if (encryption_mode_ != TR_CLEAR_PREFERRED)
{
send_ya(peer_io_.get());
}
else
{
tr_logAddTraceHand(this, "sending plain handshake");
send_handshake(peer_io_.get());
set_state(State::AwaitingHandshake);
}
}
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