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SSU2Session.cpp
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/*
* Copyright (c) 2022-2023, The PurpleI2P Project
*
* This file is part of Purple i2pd project and licensed under BSD3
*
* See full license text in LICENSE file at top of project tree
*/
#include <string.h>
#include <openssl/rand.h>
#include "Log.h"
#include "Transports.h"
#include "Gzip.h"
#include "NetDb.hpp"
#include "SSU2.h"
namespace i2p
{
namespace transport
{
void SSU2IncompleteMessage::AttachNextFragment (const uint8_t * fragment, size_t fragmentSize)
{
if (msg->len + fragmentSize > msg->maxLen)
{
LogPrint (eLogInfo, "SSU2: I2NP message size ", msg->maxLen, " is not enough");
auto newMsg = NewI2NPMessage (msg->len + fragmentSize);
*newMsg = *msg;
msg = newMsg;
}
if (msg->Concat (fragment, fragmentSize) < fragmentSize)
LogPrint (eLogError, "SSU2: I2NP buffer overflow ", msg->maxLen);
nextFragmentNum++;
}
bool SSU2IncompleteMessage::ConcatOutOfSequenceFragments ()
{
bool isLast = false;
while (outOfSequenceFragments)
{
if (outOfSequenceFragments->fragmentNum == nextFragmentNum)
{
AttachNextFragment (outOfSequenceFragments->buf, outOfSequenceFragments->len);
isLast = outOfSequenceFragments->isLast;
if (isLast)
outOfSequenceFragments = nullptr;
else
outOfSequenceFragments = outOfSequenceFragments->next;
}
else
break;
}
return isLast;
}
void SSU2IncompleteMessage::AddOutOfSequenceFragment (std::shared_ptr<SSU2IncompleteMessage::Fragment> fragment)
{
if (!fragment || !fragment->fragmentNum) return; // fragment 0 not allowed
if (fragment->fragmentNum < nextFragmentNum) return; // already processed
if (!outOfSequenceFragments)
outOfSequenceFragments = fragment;
else
{
auto frag = outOfSequenceFragments;
std::shared_ptr<Fragment> prev;
do
{
if (fragment->fragmentNum < frag->fragmentNum) break; // found
if (fragment->fragmentNum == frag->fragmentNum) return; // duplicate
prev = frag; frag = frag->next;
}
while (frag);
fragment->next = frag;
if (prev)
prev->next = fragment;
else
outOfSequenceFragments = fragment;
}
lastFragmentInsertTime = i2p::util::GetSecondsSinceEpoch ();
}
SSU2Session::SSU2Session (SSU2Server& server, std::shared_ptr<const i2p::data::RouterInfo> in_RemoteRouter,
std::shared_ptr<const i2p::data::RouterInfo::Address> addr):
TransportSession (in_RemoteRouter, SSU2_CONNECT_TIMEOUT),
m_Server (server), m_Address (addr), m_RemoteTransports (0),
m_DestConnID (0), m_SourceConnID (0), m_State (eSSU2SessionStateUnknown),
m_SendPacketNum (0), m_ReceivePacketNum (0), m_LastDatetimeSentPacketNum (0),
m_IsDataReceived (false), m_WindowSize (SSU2_MIN_WINDOW_SIZE),
m_RTT (SSU2_RESEND_INTERVAL), m_RTO (SSU2_RESEND_INTERVAL*SSU2_kAPPA), m_RelayTag (0),
m_ConnectTimer (server.GetService ()), m_TerminationReason (eSSU2TerminationReasonNormalClose),
m_MaxPayloadSize (SSU2_MIN_PACKET_SIZE - IPV6_HEADER_SIZE - UDP_HEADER_SIZE - 32) // min size
{
m_NoiseState.reset (new i2p::crypto::NoiseSymmetricState);
if (in_RemoteRouter && m_Address)
{
// outgoing
InitNoiseXKState1 (*m_NoiseState, m_Address->s);
m_RemoteEndpoint = boost::asio::ip::udp::endpoint (m_Address->host, m_Address->port);
m_RemoteTransports = in_RemoteRouter->GetCompatibleTransports (false);
RAND_bytes ((uint8_t *)&m_DestConnID, 8);
RAND_bytes ((uint8_t *)&m_SourceConnID, 8);
}
else
{
// incoming
InitNoiseXKState1 (*m_NoiseState, i2p::context.GetSSU2StaticPublicKey ());
}
}
SSU2Session::~SSU2Session ()
{
}
void SSU2Session::Connect ()
{
if (m_State == eSSU2SessionStateUnknown || m_State == eSSU2SessionStateTokenReceived)
{
ScheduleConnectTimer ();
auto token = m_Server.FindOutgoingToken (m_RemoteEndpoint);
if (token)
SendSessionRequest (token);
else
{
m_State = eSSU2SessionStateUnknown;
SendTokenRequest ();
}
}
}
void SSU2Session::ScheduleConnectTimer ()
{
m_ConnectTimer.cancel ();
m_ConnectTimer.expires_from_now (boost::posix_time::seconds(SSU2_CONNECT_TIMEOUT));
m_ConnectTimer.async_wait (std::bind (&SSU2Session::HandleConnectTimer,
shared_from_this (), std::placeholders::_1));
}
void SSU2Session::HandleConnectTimer (const boost::system::error_code& ecode)
{
if (!ecode)
{
// timeout expired
if (m_State == eSSU2SessionStateIntroduced) // WaitForIntroducer
LogPrint (eLogWarning, "SSU2: Session was not introduced after ", SSU2_CONNECT_TIMEOUT, " seconds");
else
LogPrint (eLogWarning, "SSU2: Session with ", m_RemoteEndpoint, " was not established after ", SSU2_CONNECT_TIMEOUT, " seconds");
Terminate ();
}
}
bool SSU2Session::Introduce (std::shared_ptr<SSU2Session> session, uint32_t relayTag)
{
// we are Alice
if (!session || !relayTag) return false;
// find local address to introduce
auto localAddress = session->FindLocalAddress ();
if (!localAddress) return false;
// create nonce
uint32_t nonce;
RAND_bytes ((uint8_t *)&nonce, 4);
auto ts = i2p::util::GetSecondsSinceEpoch ();
// payload
uint8_t payload[SSU2_MAX_PACKET_SIZE];
size_t payloadSize = 0;
payload[0] = eSSU2BlkRelayRequest;
payload[3] = 0; // flag
htobe32buf (payload + 4, nonce);
htobe32buf (payload + 8, relayTag);
htobe32buf (payload + 12, ts);
payload[16] = 2; // ver
size_t asz = CreateEndpoint (payload + 18, m_MaxPayloadSize - 18, boost::asio::ip::udp::endpoint (localAddress->host, localAddress->port));
if (!asz) return false;
payload[17] = asz;
payloadSize += asz + 18;
SignedData s;
s.Insert ((const uint8_t *)"RelayRequestData", 16); // prologue
s.Insert (GetRemoteIdentity ()->GetIdentHash (), 32); // bhash
s.Insert (session->GetRemoteIdentity ()->GetIdentHash (), 32); // chash
s.Insert (payload + 4, 14 + asz); // nonce, relay tag, timestamp, ver, asz and Alice's endpoint
s.Sign (i2p::context.GetPrivateKeys (), payload + payloadSize);
payloadSize += i2p::context.GetIdentity ()->GetSignatureLen ();
htobe16buf (payload + 1, payloadSize - 3); // size
payloadSize += CreatePaddingBlock (payload + payloadSize, m_MaxPayloadSize - payloadSize);
// send
m_RelaySessions.emplace (nonce, std::make_pair (session, ts));
session->m_SourceConnID = htobe64 (((uint64_t)nonce << 32) | nonce);
session->m_DestConnID = ~session->m_SourceConnID;
m_Server.AddSession (session);
SendData (payload, payloadSize);
return true;
}
void SSU2Session::WaitForIntroduction ()
{
m_State = eSSU2SessionStateIntroduced;
ScheduleConnectTimer ();
}
void SSU2Session::ConnectAfterIntroduction ()
{
if (m_State == eSSU2SessionStateIntroduced)
{
// create new connID
uint64_t oldConnID = GetConnID ();
RAND_bytes ((uint8_t *)&m_DestConnID, 8);
RAND_bytes ((uint8_t *)&m_SourceConnID, 8);
// connect
m_State = eSSU2SessionStateTokenReceived;
m_Server.AddPendingOutgoingSession (shared_from_this ());
m_Server.RemoveSession (oldConnID);
Connect ();
}
}
void SSU2Session::SendPeerTest ()
{
// we are Alice
uint32_t nonce;
RAND_bytes ((uint8_t *)&nonce, 4);
auto ts = i2p::util::GetMillisecondsSinceEpoch ();
// session for message 5
auto session = std::make_shared<SSU2Session> (m_Server);
session->SetState (eSSU2SessionStatePeerTest);
m_PeerTests.emplace (nonce, std::make_pair (session, ts/1000));
session->m_SourceConnID = htobe64 (((uint64_t)nonce << 32) | nonce);
session->m_DestConnID = ~session->m_SourceConnID;
m_Server.AddSession (session);
// peer test block
auto packet = m_Server.GetSentPacketsPool ().AcquireShared ();
packet->payloadSize = CreatePeerTestBlock (packet->payload, m_MaxPayloadSize, nonce);
if (packet->payloadSize > 0)
{
packet->payloadSize += CreatePaddingBlock (packet->payload + packet->payloadSize, m_MaxPayloadSize - packet->payloadSize);
uint32_t packetNum = SendData (packet->payload, packet->payloadSize, SSU2_FLAG_IMMEDIATE_ACK_REQUESTED);
packet->sendTime = ts;
m_SentPackets.emplace (packetNum, packet);
LogPrint (eLogDebug, "SSU2: PeerTest msg=1 sent to ", i2p::data::GetIdentHashAbbreviation (GetRemoteIdentity ()->GetIdentHash ()));
}
}
void SSU2Session::SendKeepAlive ()
{
if (IsEstablished ())
{
uint8_t payload[20];
size_t payloadSize = CreatePaddingBlock (payload, 20, 8);
SendData (payload, payloadSize);
}
}
void SSU2Session::Terminate ()
{
if (m_State != eSSU2SessionStateTerminated)
{
m_State = eSSU2SessionStateTerminated;
m_ConnectTimer.cancel ();
m_OnEstablished = nullptr;
if (m_RelayTag)
m_Server.RemoveRelay (m_RelayTag);
m_SentHandshakePacket.reset (nullptr);
m_SessionConfirmedFragment.reset (nullptr);
m_PathChallenge.reset (nullptr);
m_SendQueue.clear ();
m_SendQueueSize = 0;
m_SentPackets.clear ();
m_IncompleteMessages.clear ();
m_RelaySessions.clear ();
m_PeerTests.clear ();
m_ReceivedI2NPMsgIDs.clear ();
m_Server.RemoveSession (m_SourceConnID);
transports.PeerDisconnected (shared_from_this ());
LogPrint (eLogDebug, "SSU2: Session terminated");
}
}
void SSU2Session::RequestTermination (SSU2TerminationReason reason)
{
if (m_State == eSSU2SessionStateEstablished || m_State == eSSU2SessionStateClosing)
{
m_TerminationReason = reason;
SendTermination ();
}
m_State = eSSU2SessionStateClosing;
}
void SSU2Session::Established ()
{
m_State = eSSU2SessionStateEstablished;
m_EphemeralKeys = nullptr;
m_NoiseState.reset (nullptr);
m_SessionConfirmedFragment.reset (nullptr);
m_SentHandshakePacket.reset (nullptr);
m_ConnectTimer.cancel ();
SetTerminationTimeout (SSU2_TERMINATION_TIMEOUT);
transports.PeerConnected (shared_from_this ());
if (m_OnEstablished)
{
m_OnEstablished ();
m_OnEstablished = nullptr;
}
}
void SSU2Session::Done ()
{
m_Server.GetService ().post (std::bind (&SSU2Session::Terminate, shared_from_this ()));
}
void SSU2Session::SendLocalRouterInfo (bool update)
{
if (update || !IsOutgoing ())
{
auto s = shared_from_this ();
m_Server.GetService ().post ([s]()
{
if (!s->IsEstablished ()) return;
uint8_t payload[SSU2_MAX_PACKET_SIZE];
size_t payloadSize = s->CreateRouterInfoBlock (payload, s->m_MaxPayloadSize - 32, i2p::context.GetSharedRouterInfo ());
if (payloadSize)
{
if (payloadSize < s->m_MaxPayloadSize)
payloadSize += s->CreatePaddingBlock (payload + payloadSize, s->m_MaxPayloadSize - payloadSize);
s->SendData (payload, payloadSize);
}
else
s->SendFragmentedMessage (CreateDatabaseStoreMsg ());
});
}
}
void SSU2Session::SendI2NPMessages (const std::vector<std::shared_ptr<I2NPMessage> >& msgs)
{
m_Server.GetService ().post (std::bind (&SSU2Session::PostI2NPMessages, shared_from_this (), msgs));
}
void SSU2Session::PostI2NPMessages (std::vector<std::shared_ptr<I2NPMessage> > msgs)
{
if (m_State == eSSU2SessionStateTerminated) return;
for (auto it: msgs)
m_SendQueue.push_back (std::move (it));
SendQueue ();
if (m_SendQueue.size () > 0) // windows is full
{
if (m_SendQueue.size () <= SSU2_MAX_OUTGOING_QUEUE_SIZE)
Resend (i2p::util::GetMillisecondsSinceEpoch ());
else
{
LogPrint (eLogWarning, "SSU2: Outgoing messages queue size to ",
GetIdentHashBase64(), " exceeds ", SSU2_MAX_OUTGOING_QUEUE_SIZE);
RequestTermination (eSSU2TerminationReasonTimeout);
}
}
m_SendQueueSize = m_SendQueue.size ();
}
bool SSU2Session::SendQueue ()
{
if (!m_SendQueue.empty () && m_SentPackets.size () <= m_WindowSize)
{
auto ts = i2p::util::GetMillisecondsSinceEpoch ();
auto packet = m_Server.GetSentPacketsPool ().AcquireShared ();
size_t ackBlockSize = CreateAckBlock (packet->payload, m_MaxPayloadSize);
bool ackBlockSent = false;
packet->payloadSize += ackBlockSize;
while (!m_SendQueue.empty () && m_SentPackets.size () <= m_WindowSize)
{
auto msg = m_SendQueue.front ();
if (!msg)
{
m_SendQueue.pop_front ();
continue;
}
size_t len = msg->GetNTCP2Length () + 3;
if (len > m_MaxPayloadSize) // message too long
{
m_SendQueue.pop_front ();
if (SendFragmentedMessage (msg))
ackBlockSent = true;
}
else if (packet->payloadSize + len <= m_MaxPayloadSize)
{
m_SendQueue.pop_front ();
packet->payloadSize += CreateI2NPBlock (packet->payload + packet->payloadSize, m_MaxPayloadSize - packet->payloadSize, std::move (msg));
}
else
{
// create new packet and copy ack block
auto newPacket = m_Server.GetSentPacketsPool ().AcquireShared ();
memcpy (newPacket->payload, packet->payload, ackBlockSize);
newPacket->payloadSize = ackBlockSize;
// complete current packet
if (packet->payloadSize > ackBlockSize) // more than just ack block
{
ackBlockSent = true;
// try to add padding
if (packet->payloadSize + 16 < m_MaxPayloadSize)
packet->payloadSize += CreatePaddingBlock (packet->payload + packet->payloadSize, m_MaxPayloadSize - packet->payloadSize);
}
else
{
// reduce ack block
if (len + 8 < m_MaxPayloadSize)
{
// keep Ack block and drop some ranges
ackBlockSent = true;
packet->payloadSize = m_MaxPayloadSize - len;
if (packet->payloadSize & 0x01) packet->payloadSize--; // make it even
htobe16buf (packet->payload + 1, packet->payloadSize - 3); // new block size
}
else // drop Ack block completely
packet->payloadSize = 0;
// msg fits single packet
m_SendQueue.pop_front ();
packet->payloadSize += CreateI2NPBlock (packet->payload + packet->payloadSize, m_MaxPayloadSize - packet->payloadSize, std::move (msg));
}
// send right a way
uint32_t packetNum = SendData (packet->payload, packet->payloadSize);
packet->sendTime = ts;
m_SentPackets.emplace (packetNum, packet);
packet = newPacket; // just ack block
}
};
if (packet->payloadSize > ackBlockSize)
{
// last
ackBlockSent = true;
if (packet->payloadSize + 16 < m_MaxPayloadSize)
packet->payloadSize += CreatePaddingBlock (packet->payload + packet->payloadSize, m_MaxPayloadSize - packet->payloadSize);
uint32_t packetNum = SendData (packet->payload, packet->payloadSize, SSU2_FLAG_IMMEDIATE_ACK_REQUESTED);
packet->sendTime = ts;
m_SentPackets.emplace (packetNum, packet);
}
return ackBlockSent;
}
return false;
}
bool SSU2Session::SendFragmentedMessage (std::shared_ptr<I2NPMessage> msg)
{
if (!msg) return false;
size_t lastFragmentSize = (msg->GetNTCP2Length () + 3 - m_MaxPayloadSize) % (m_MaxPayloadSize - 8);
size_t extraSize = m_MaxPayloadSize - lastFragmentSize;
bool ackBlockSent = false;
uint32_t msgID;
memcpy (&msgID, msg->GetHeader () + I2NP_HEADER_MSGID_OFFSET, 4);
auto ts = i2p::util::GetMillisecondsSinceEpoch ();
auto packet = m_Server.GetSentPacketsPool ().AcquireShared ();
if (extraSize >= 8)
{
packet->payloadSize = CreateAckBlock (packet->payload, extraSize);
ackBlockSent = true;
if (packet->payloadSize + 12 < m_MaxPayloadSize)
{
uint32_t packetNum = SendData (packet->payload, packet->payloadSize);
packet->sendTime = ts;
m_SentPackets.emplace (packetNum, packet);
packet = m_Server.GetSentPacketsPool ().AcquireShared ();
}
else
extraSize -= packet->payloadSize;
}
size_t offset = extraSize > 0 ? (rand () % extraSize) : 0;
if (offset + packet->payloadSize >= m_MaxPayloadSize) offset = 0;
auto size = CreateFirstFragmentBlock (packet->payload + packet->payloadSize, m_MaxPayloadSize - offset - packet->payloadSize, msg);
if (!size) return false;
extraSize -= offset;
packet->payloadSize += size;
uint32_t firstPacketNum = SendData (packet->payload, packet->payloadSize);
packet->sendTime = ts;
m_SentPackets.emplace (firstPacketNum, packet);
uint8_t fragmentNum = 0;
while (msg->offset < msg->len)
{
offset = extraSize > 0 ? (rand () % extraSize) : 0;
packet = m_Server.GetSentPacketsPool ().AcquireShared ();
packet->payloadSize = CreateFollowOnFragmentBlock (packet->payload, m_MaxPayloadSize - offset, msg, fragmentNum, msgID);
extraSize -= offset;
uint8_t flags = 0;
if (msg->offset >= msg->len && packet->payloadSize + 16 < m_MaxPayloadSize) // last fragment
{
packet->payloadSize += CreatePaddingBlock (packet->payload + packet->payloadSize, m_MaxPayloadSize - packet->payloadSize);
if (fragmentNum > 2) // 3 or more fragments
flags |= SSU2_FLAG_IMMEDIATE_ACK_REQUESTED;
}
uint32_t followonPacketNum = SendData (packet->payload, packet->payloadSize, flags);
packet->sendTime = ts;
m_SentPackets.emplace (followonPacketNum, packet);
}
return ackBlockSent;
}
size_t SSU2Session::Resend (uint64_t ts)
{
// resend handshake packet
if (m_SentHandshakePacket && ts >= m_SentHandshakePacket->sendTime + SSU2_HANDSHAKE_RESEND_INTERVAL)
{
LogPrint (eLogDebug, "SSU2: Resending ", (int)m_State);
ResendHandshakePacket ();
m_SentHandshakePacket->sendTime = ts;
return 0;
}
// resend data packets
if (m_SentPackets.empty ()) return 0;
std::map<uint32_t, std::shared_ptr<SSU2SentPacket> > resentPackets;
for (auto it = m_SentPackets.begin (); it != m_SentPackets.end (); )
if (ts >= it->second->sendTime + it->second->numResends*m_RTO)
{
if (it->second->numResends > SSU2_MAX_NUM_RESENDS)
{
LogPrint (eLogInfo, "SSU2: Packet was not Acked after ", it->second->numResends, " attempts. Terminate session");
m_SentPackets.clear ();
m_SendQueue.clear ();
m_SendQueueSize = 0;
RequestTermination (eSSU2TerminationReasonTimeout);
return resentPackets.size ();
}
else
{
uint32_t packetNum = SendData (it->second->payload, it->second->payloadSize);
it->second->numResends++;
it->second->sendTime = ts;
resentPackets.emplace (packetNum, it->second);
it = m_SentPackets.erase (it);
}
}
else
it++;
if (!resentPackets.empty ())
{
#if (__cplusplus >= 201703L) // C++ 17 or higher
m_SentPackets.merge (resentPackets);
#else
m_SentPackets.insert (resentPackets.begin (), resentPackets.end ());
#endif
m_WindowSize >>= 1; // /2
if (m_WindowSize < SSU2_MIN_WINDOW_SIZE) m_WindowSize = SSU2_MIN_WINDOW_SIZE;
return resentPackets.size ();
}
return 0;
}
void SSU2Session::ResendHandshakePacket ()
{
if (m_SentHandshakePacket)
{
m_Server.Send (m_SentHandshakePacket->header.buf, 16, m_SentHandshakePacket->headerX, 48,
m_SentHandshakePacket->payload, m_SentHandshakePacket->payloadSize, m_RemoteEndpoint);
if (m_SessionConfirmedFragment && m_State == eSSU2SessionStateSessionConfirmedSent)
// resend second fragment of SessionConfirmed
m_Server.Send (m_SessionConfirmedFragment->header.buf, 16,
m_SessionConfirmedFragment->payload, m_SessionConfirmedFragment->payloadSize, m_RemoteEndpoint);
}
}
bool SSU2Session::ProcessFirstIncomingMessage (uint64_t connID, uint8_t * buf, size_t len)
{
// we are Bob
m_SourceConnID = connID;
Header header;
header.h.connID = connID;
memcpy (header.buf + 8, buf + 8, 8);
header.ll[1] ^= CreateHeaderMask (i2p::context.GetSSU2IntroKey (), buf + (len - 12));
switch (header.h.type)
{
case eSSU2SessionRequest:
ProcessSessionRequest (header, buf, len);
break;
case eSSU2TokenRequest:
ProcessTokenRequest (header, buf, len);
break;
case eSSU2PeerTest:
{
// TODO: remove later
if (len < 32)
{
LogPrint (eLogWarning, "SSU2: PeerTest message too short ", len);
break;
}
const uint8_t nonce[12] = {0};
uint64_t headerX[2];
i2p::crypto::ChaCha20 (buf + 16, 16, i2p::context.GetSSU2IntroKey (), nonce, (uint8_t *)headerX);
LogPrint (eLogWarning, "SSU2: Unexpected PeerTest message SourceConnID=", connID, " DestConnID=", headerX[0]);
break;
}
case eSSU2HolePunch:
LogPrint (eLogDebug, "SSU2: Late HolePunch for ", connID);
break;
default:
{
LogPrint (eLogWarning, "SSU2: Unexpected message type ", (int)header.h.type, " from ", m_RemoteEndpoint, " of ", len, " bytes");
return false;
}
}
return true;
}
void SSU2Session::SendSessionRequest (uint64_t token)
{
// we are Alice
m_EphemeralKeys = i2p::transport::transports.GetNextX25519KeysPair ();
m_SentHandshakePacket.reset (new HandshakePacket);
auto ts = i2p::util::GetMillisecondsSinceEpoch ();
m_SentHandshakePacket->sendTime = ts;
Header& header = m_SentHandshakePacket->header;
uint8_t * headerX = m_SentHandshakePacket->headerX,
* payload = m_SentHandshakePacket->payload;
// fill packet
header.h.connID = m_DestConnID; // dest id
RAND_bytes (header.buf + 8, 4); // random packet num
header.h.type = eSSU2SessionRequest;
header.h.flags[0] = 2; // ver
header.h.flags[1] = (uint8_t)i2p::context.GetNetID (); // netID
header.h.flags[2] = 0; // flag
memcpy (headerX, &m_SourceConnID, 8); // source id
memcpy (headerX + 8, &token, 8); // token
memcpy (headerX + 16, m_EphemeralKeys->GetPublicKey (), 32); // X
// payload
payload[0] = eSSU2BlkDateTime;
htobe16buf (payload + 1, 4);
htobe32buf (payload + 3, (ts + 500)/1000);
size_t payloadSize = 7;
if (GetRouterStatus () == eRouterStatusFirewalled && m_Address->IsIntroducer ())
{
// relay tag request
payload[payloadSize] = eSSU2BlkRelayTagRequest;
memset (payload + payloadSize + 1, 0, 2); // size = 0
payloadSize += 3;
}
payloadSize += CreatePaddingBlock (payload + payloadSize, 40 - payloadSize, 1);
// KDF for session request
m_NoiseState->MixHash ({ {header.buf, 16}, {headerX, 16} }); // h = SHA256(h || header)
m_NoiseState->MixHash (m_EphemeralKeys->GetPublicKey (), 32); // h = SHA256(h || aepk);
uint8_t sharedSecret[32];
m_EphemeralKeys->Agree (m_Address->s, sharedSecret);
m_NoiseState->MixKey (sharedSecret);
// encrypt
const uint8_t nonce[12] = {0}; // always 0
i2p::crypto::AEADChaCha20Poly1305 (payload, payloadSize, m_NoiseState->m_H, 32, m_NoiseState->m_CK + 32, nonce, payload, payloadSize + 16, true);
payloadSize += 16;
header.ll[0] ^= CreateHeaderMask (m_Address->i, payload + (payloadSize - 24));
header.ll[1] ^= CreateHeaderMask (m_Address->i, payload + (payloadSize - 12));
i2p::crypto::ChaCha20 (headerX, 48, m_Address->i, nonce, headerX);
m_NoiseState->MixHash (payload, payloadSize); // h = SHA256(h || encrypted payload from Session Request) for SessionCreated
m_SentHandshakePacket->payloadSize = payloadSize;
// send
if (m_State == eSSU2SessionStateTokenReceived || m_Server.AddPendingOutgoingSession (shared_from_this ()))
{
m_State = eSSU2SessionStateSessionRequestSent;
m_HandshakeInterval = ts;
m_Server.Send (header.buf, 16, headerX, 48, payload, payloadSize, m_RemoteEndpoint);
}
else
{
LogPrint (eLogWarning, "SSU2: SessionRequest request to ", m_RemoteEndpoint, " already pending");
Terminate ();
}
}
void SSU2Session::ProcessSessionRequest (Header& header, uint8_t * buf, size_t len)
{
// we are Bob
if (len < 88)
{
LogPrint (eLogWarning, "SSU2: SessionRequest message too short ", len);
return;
}
const uint8_t nonce[12] = {0};
uint8_t headerX[48];
i2p::crypto::ChaCha20 (buf + 16, 48, i2p::context.GetSSU2IntroKey (), nonce, headerX);
memcpy (&m_DestConnID, headerX, 8);
uint64_t token;
memcpy (&token, headerX + 8, 8);
if (!token || token != m_Server.GetIncomingToken (m_RemoteEndpoint))
{
LogPrint (eLogDebug, "SSU2: SessionRequest token mismatch. Retry");
SendRetry ();
return;
}
// KDF for session request
m_NoiseState->MixHash ( { {header.buf, 16}, {headerX, 16} } ); // h = SHA256(h || header)
m_NoiseState->MixHash (headerX + 16, 32); // h = SHA256(h || aepk);
uint8_t sharedSecret[32];
i2p::context.GetSSU2StaticKeys ().Agree (headerX + 16, sharedSecret);
m_NoiseState->MixKey (sharedSecret);
// decrypt
uint8_t * payload = buf + 64;
std::vector<uint8_t> decryptedPayload(len - 80);
if (!i2p::crypto::AEADChaCha20Poly1305 (payload, len - 80, m_NoiseState->m_H, 32,
m_NoiseState->m_CK + 32, nonce, decryptedPayload.data (), decryptedPayload.size (), false))
{
LogPrint (eLogWarning, "SSU2: SessionRequest AEAD verification failed ");
return;
}
m_NoiseState->MixHash (payload, len - 64); // h = SHA256(h || encrypted payload from Session Request) for SessionCreated
// payload
m_State = eSSU2SessionStateSessionRequestReceived;
HandlePayload (decryptedPayload.data (), decryptedPayload.size ());
if (m_TerminationReason == eSSU2TerminationReasonNormalClose)
{
m_Server.AddSession (shared_from_this ());
SendSessionCreated (headerX + 16);
}
else
SendRetry ();
}
void SSU2Session::SendSessionCreated (const uint8_t * X)
{
// we are Bob
m_EphemeralKeys = i2p::transport::transports.GetNextX25519KeysPair ();
m_SentHandshakePacket.reset (new HandshakePacket);
auto ts = i2p::util::GetMillisecondsSinceEpoch ();
m_SentHandshakePacket->sendTime = ts;
uint8_t kh2[32];
i2p::crypto::HKDF (m_NoiseState->m_CK, nullptr, 0, "SessCreateHeader", kh2, 32); // k_header_2 = HKDF(chainKey, ZEROLEN, "SessCreateHeader", 32)
// fill packet
Header& header = m_SentHandshakePacket->header;
uint8_t * headerX = m_SentHandshakePacket->headerX,
* payload = m_SentHandshakePacket->payload;
header.h.connID = m_DestConnID; // dest id
RAND_bytes (header.buf + 8, 4); // random packet num
header.h.type = eSSU2SessionCreated;
header.h.flags[0] = 2; // ver
header.h.flags[1] = (uint8_t)i2p::context.GetNetID (); // netID
header.h.flags[2] = 0; // flag
memcpy (headerX, &m_SourceConnID, 8); // source id
memset (headerX + 8, 0, 8); // token = 0
memcpy (headerX + 16, m_EphemeralKeys->GetPublicKey (), 32); // Y
// payload
size_t maxPayloadSize = m_MaxPayloadSize - 48;
payload[0] = eSSU2BlkDateTime;
htobe16buf (payload + 1, 4);
htobe32buf (payload + 3, (ts + 500)/1000);
size_t payloadSize = 7;
payloadSize += CreateAddressBlock (payload + payloadSize, maxPayloadSize - payloadSize, m_RemoteEndpoint);
if (m_RelayTag)
{
payload[payloadSize] = eSSU2BlkRelayTag;
htobe16buf (payload + payloadSize + 1, 4);
htobe32buf (payload + payloadSize + 3, m_RelayTag);
payloadSize += 7;
}
auto token = m_Server.NewIncomingToken (m_RemoteEndpoint);
if (ts + SSU2_TOKEN_EXPIRATION_THRESHOLD > token.second) // not expired?
{
payload[payloadSize] = eSSU2BlkNewToken;
htobe16buf (payload + payloadSize + 1, 12);
htobe32buf (payload + payloadSize + 3, token.second - SSU2_TOKEN_EXPIRATION_THRESHOLD); // expires
memcpy (payload + payloadSize + 7, &token.first, 8); // token
payloadSize += 15;
}
payloadSize += CreatePaddingBlock (payload + payloadSize, maxPayloadSize - payloadSize);
// KDF for SessionCreated
m_NoiseState->MixHash ( { {header.buf, 16}, {headerX, 16} } ); // h = SHA256(h || header)
m_NoiseState->MixHash (headerX + 16, 32); // h = SHA256(h || bepk);
uint8_t sharedSecret[32];
m_EphemeralKeys->Agree (X, sharedSecret);
m_NoiseState->MixKey (sharedSecret);
// encrypt
const uint8_t nonce[12] = {0}; // always zero
i2p::crypto::AEADChaCha20Poly1305 (payload, payloadSize, m_NoiseState->m_H, 32, m_NoiseState->m_CK + 32, nonce, payload, payloadSize + 16, true);
payloadSize += 16;
m_NoiseState->MixHash (payload, payloadSize); // h = SHA256(h || encrypted Noise payload from Session Created)
header.ll[0] ^= CreateHeaderMask (i2p::context.GetSSU2IntroKey (), payload + (payloadSize - 24));
header.ll[1] ^= CreateHeaderMask (kh2, payload + (payloadSize - 12));
i2p::crypto::ChaCha20 (headerX, 48, kh2, nonce, headerX);
m_State = eSSU2SessionStateSessionCreatedSent;
m_SentHandshakePacket->payloadSize = payloadSize;
// send
m_HandshakeInterval = ts;
m_Server.Send (header.buf, 16, headerX, 48, payload, payloadSize, m_RemoteEndpoint);
}
bool SSU2Session::ProcessSessionCreated (uint8_t * buf, size_t len)
{
// we are Alice
Header header;
memcpy (header.buf, buf, 16);
header.ll[0] ^= CreateHeaderMask (m_Address->i, buf + (len - 24));
uint8_t kh2[32];
i2p::crypto::HKDF (m_NoiseState->m_CK, nullptr, 0, "SessCreateHeader", kh2, 32); // k_header_2 = HKDF(chainKey, ZEROLEN, "SessCreateHeader", 32)
header.ll[1] ^= CreateHeaderMask (kh2, buf + (len - 12));
if (header.h.type != eSSU2SessionCreated)
// this situation is valid, because it might be Retry with different encryption
return false;
if (len < 80)
{
LogPrint (eLogWarning, "SSU2: SessionCreated message too short ", len);
return false;
}
m_HandshakeInterval = i2p::util::GetMillisecondsSinceEpoch () - m_HandshakeInterval;
const uint8_t nonce[12] = {0};
uint8_t headerX[48];
i2p::crypto::ChaCha20 (buf + 16, 48, kh2, nonce, headerX);
// KDF for SessionCreated
m_NoiseState->MixHash ( { {header.buf, 16}, {headerX, 16} } ); // h = SHA256(h || header)
m_NoiseState->MixHash (headerX + 16, 32); // h = SHA256(h || bepk);
uint8_t sharedSecret[32];
m_EphemeralKeys->Agree (headerX + 16, sharedSecret);
m_NoiseState->MixKey (sharedSecret);
// decrypt
uint8_t * payload = buf + 64;
std::vector<uint8_t> decryptedPayload(len - 80);
if (!i2p::crypto::AEADChaCha20Poly1305 (payload, len - 80, m_NoiseState->m_H, 32,
m_NoiseState->m_CK + 32, nonce, decryptedPayload.data (), decryptedPayload.size (), false))
{
LogPrint (eLogWarning, "SSU2: SessionCreated AEAD verification failed ");
if (GetRemoteIdentity ())
i2p::data::netdb.SetUnreachable (GetRemoteIdentity ()->GetIdentHash (), true); // assume wrong s key
return false;
}
m_NoiseState->MixHash (payload, len - 64); // h = SHA256(h || encrypted payload from SessionCreated) for SessionConfirmed
// payload
m_State = eSSU2SessionStateSessionCreatedReceived;
HandlePayload (decryptedPayload.data (), decryptedPayload.size ());
m_Server.AddSession (shared_from_this ());
AdjustMaxPayloadSize ();
SendSessionConfirmed (headerX + 16);
KDFDataPhase (m_KeyDataSend, m_KeyDataReceive);
return true;
}
void SSU2Session::SendSessionConfirmed (const uint8_t * Y)
{
// we are Alice
m_SentHandshakePacket.reset (new HandshakePacket);
m_SentHandshakePacket->sendTime = i2p::util::GetMillisecondsSinceEpoch ();
uint8_t kh2[32];
i2p::crypto::HKDF (m_NoiseState->m_CK, nullptr, 0, "SessionConfirmed", kh2, 32); // k_header_2 = HKDF(chainKey, ZEROLEN, "SessionConfirmed", 32)
// fill packet
Header& header = m_SentHandshakePacket->header;
header.h.connID = m_DestConnID; // dest id
header.h.packetNum = 0; // always zero
header.h.type = eSSU2SessionConfirmed;
memset (header.h.flags, 0, 3);
header.h.flags[0] = 1; // frag, total fragments always 1
// payload
size_t maxPayloadSize = m_MaxPayloadSize - 48; // for part 2, 48 is part1
uint8_t * payload = m_SentHandshakePacket->payload;
size_t payloadSize = CreateRouterInfoBlock (payload, maxPayloadSize, i2p::context.GetSharedRouterInfo ());
if (!payloadSize)
{
// split by two fragments
maxPayloadSize += m_MaxPayloadSize;
payloadSize = CreateRouterInfoBlock (payload, maxPayloadSize, i2p::context.GetSharedRouterInfo ());
header.h.flags[0] = 0x02; // frag 0, total fragments 2
// TODO: check if we need more fragments
}
if (payloadSize < maxPayloadSize)
payloadSize += CreatePaddingBlock (payload + payloadSize, maxPayloadSize - payloadSize);
// KDF for Session Confirmed part 1
m_NoiseState->MixHash (header.buf, 16); // h = SHA256(h || header)
// Encrypt part 1
uint8_t * part1 = m_SentHandshakePacket->headerX;
uint8_t nonce[12];
CreateNonce (1, nonce); // always one
i2p::crypto::AEADChaCha20Poly1305 (i2p::context.GetSSU2StaticPublicKey (), 32, m_NoiseState->m_H, 32, m_NoiseState->m_CK + 32, nonce, part1, 48, true);
m_NoiseState->MixHash (part1, 48); // h = SHA256(h || ciphertext);
// KDF for Session Confirmed part 2
uint8_t sharedSecret[32];
i2p::context.GetSSU2StaticKeys ().Agree (Y, sharedSecret);
m_NoiseState->MixKey (sharedSecret);
// Encrypt part2
memset (nonce, 0, 12); // always zero
i2p::crypto::AEADChaCha20Poly1305 (payload, payloadSize, m_NoiseState->m_H, 32, m_NoiseState->m_CK + 32, nonce, payload, payloadSize + 16, true);
payloadSize += 16;
m_NoiseState->MixHash (payload, payloadSize); // h = SHA256(h || ciphertext);
m_SentHandshakePacket->payloadSize = payloadSize;
if (header.h.flags[0] > 1)
{
if (payloadSize > m_MaxPayloadSize - 48)
{
payloadSize = m_MaxPayloadSize - 48 - (rand () % 16);
if (m_SentHandshakePacket->payloadSize - payloadSize < 24)
payloadSize -= 24;
}
else
header.h.flags[0] = 1;
}
// Encrypt header
header.ll[0] ^= CreateHeaderMask (m_Address->i, payload + (payloadSize - 24));
header.ll[1] ^= CreateHeaderMask (kh2, payload + (payloadSize - 12));
m_State = eSSU2SessionStateSessionConfirmedSent;
// send
m_Server.Send (header.buf, 16, part1, 48, payload, payloadSize, m_RemoteEndpoint);
m_SendPacketNum++;
if (m_SentHandshakePacket->payloadSize > payloadSize)
{
// send second fragment
m_SessionConfirmedFragment.reset (new HandshakePacket);
Header& header = m_SessionConfirmedFragment->header;
header.h.connID = m_DestConnID; // dest id
header.h.packetNum = 0;
header.h.type = eSSU2SessionConfirmed;
memset (header.h.flags, 0, 3);
header.h.flags[0] = 0x12; // frag 1, total fragments 2
m_SessionConfirmedFragment->payloadSize = m_SentHandshakePacket->payloadSize - payloadSize;
memcpy (m_SessionConfirmedFragment->payload, m_SentHandshakePacket->payload + payloadSize, m_SessionConfirmedFragment->payloadSize);
m_SentHandshakePacket->payloadSize = payloadSize;
header.ll[0] ^= CreateHeaderMask (m_Address->i, m_SessionConfirmedFragment->payload + (m_SessionConfirmedFragment->payloadSize - 24));
header.ll[1] ^= CreateHeaderMask (kh2, m_SessionConfirmedFragment->payload + (m_SessionConfirmedFragment->payloadSize - 12));
m_Server.Send (header.buf, 16, m_SessionConfirmedFragment->payload, m_SessionConfirmedFragment->payloadSize, m_RemoteEndpoint);
}
}
bool SSU2Session::ProcessSessionConfirmed (uint8_t * buf, size_t len)
{
// we are Bob
Header header;
memcpy (header.buf, buf, 16);
header.ll[0] ^= CreateHeaderMask (i2p::context.GetSSU2IntroKey (), buf + (len - 24));
uint8_t kh2[32];
i2p::crypto::HKDF (m_NoiseState->m_CK, nullptr, 0, "SessionConfirmed", kh2, 32); // k_header_2 = HKDF(chainKey, ZEROLEN, "SessionConfirmed", 32)
header.ll[1] ^= CreateHeaderMask (kh2, buf + (len - 12));
if (header.h.type != eSSU2SessionConfirmed)
{
LogPrint (eLogInfo, "SSU2: Unexpected message type ", (int)header.h.type, " instead ", (int)eSSU2SessionConfirmed);
// TODO: queue up
return true;
}
// packet num must be always zero
if (header.h.packetNum)
{
LogPrint (eLogError, "SSU2: Non zero packet number in SessionConfirmed");
return false;
}
// check if fragmented
uint8_t numFragments = header.h.flags[0] & 0x0F;
if (numFragments > 1)
{
// fragmented
if (numFragments > 2)
{
LogPrint (eLogError, "SSU2: Too many fragments ", (int)numFragments, " in SessionConfirmed from ", m_RemoteEndpoint);
return false;
}
if (len < 32)
{
LogPrint (eLogWarning, "SSU2: SessionConfirmed fragment too short ", len);
if (m_SessionConfirmedFragment) m_SessionConfirmedFragment.reset (nullptr);
return false;
}
if (!(header.h.flags[0] & 0xF0))
{
// first fragment
if (!m_SessionConfirmedFragment)
{
m_SessionConfirmedFragment.reset (new HandshakePacket);
m_SessionConfirmedFragment->header = header;
memcpy (m_SessionConfirmedFragment->payload, buf + 16, len - 16);
m_SessionConfirmedFragment->payloadSize = len - 16;
return true; // wait for second fragment
}
else if (m_SessionConfirmedFragment->isSecondFragment)
{
// we have second fragment
m_SessionConfirmedFragment->header = header;
memmove (m_SessionConfirmedFragment->payload + (len - 16), m_SessionConfirmedFragment->payload, m_SessionConfirmedFragment->payloadSize);
memcpy (m_SessionConfirmedFragment->payload, buf + 16, len - 16);
m_SessionConfirmedFragment->payloadSize += (len - 16);
m_SessionConfirmedFragment->isSecondFragment = false;
buf = m_SessionConfirmedFragment->payload - 16;
len = m_SessionConfirmedFragment->payloadSize + 16;
}
else
return true;
}
else
{
// second fragment
if (!m_SessionConfirmedFragment)
{
// out of sequence, save it
m_SessionConfirmedFragment.reset (new HandshakePacket);
memcpy (m_SessionConfirmedFragment->payload, buf + 16, len - 16);
m_SessionConfirmedFragment->payloadSize = len - 16;
m_SessionConfirmedFragment->isSecondFragment = true;
return true;
}
header = m_SessionConfirmedFragment->header;
if (m_SessionConfirmedFragment->payloadSize + (len - 16) <= SSU2_MAX_PACKET_SIZE*2)
{
memcpy (m_SessionConfirmedFragment->payload + m_SessionConfirmedFragment->payloadSize, buf + 16, len - 16);
m_SessionConfirmedFragment->payloadSize += (len - 16);
}
buf = m_SessionConfirmedFragment->payload - 16;
len = m_SessionConfirmedFragment->payloadSize + 16;
}
}
if (len < 80)
{
LogPrint (eLogWarning, "SSU2: SessionConfirmed message too short ", len);
if (m_SessionConfirmedFragment) m_SessionConfirmedFragment.reset (nullptr);