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i2pd/libi2pd/TunnelEndpoint.cpp

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/*
* Copyright (c) 2013-2024, 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 "I2PEndian.h"
#include <string.h>
#include "Crypto.h"
#include "Log.h"
#include "NetDb.hpp"
#include "I2NPProtocol.h"
#include "Transports.h"
#include "RouterContext.h"
#include "Timestamp.h"
#include "TunnelEndpoint.h"
namespace i2p
{
namespace tunnel
{
void TunnelEndpoint::HandleDecryptedTunnelDataMsg (std::shared_ptr<I2NPMessage> msg)
{
m_NumReceivedBytes += TUNNEL_DATA_MSG_SIZE;
uint8_t * decrypted = msg->GetPayload () + 20; // 4 + 16
uint8_t * zero = (uint8_t *)memchr (decrypted + 4, 0, TUNNEL_DATA_ENCRYPTED_SIZE - 4); // without 4-byte checksum
if (zero)
{
uint8_t * fragment = zero + 1;
// verify checksum
memcpy (msg->GetPayload () + TUNNEL_DATA_MSG_SIZE, msg->GetPayload () + 4, 16); // copy iv to the end
uint8_t hash[32];
SHA256(fragment, TUNNEL_DATA_MSG_SIZE -(fragment - msg->GetPayload ()) + 16, hash); // payload + iv
if (memcmp (hash, decrypted, 4))
{
LogPrint (eLogError, "TunnelMessage: Checksum verification failed");
return;
}
// process fragments
while (fragment < decrypted + TUNNEL_DATA_ENCRYPTED_SIZE)
{
uint8_t flag = fragment[0];
fragment++;
bool isFollowOnFragment = flag & 0x80, isLastFragment = true;
uint32_t msgID = 0;
int fragmentNum = 0;
if (!isFollowOnFragment)
{
// first fragment
if (m_CurrentMsgID)
AddIncompleteCurrentMessage (); // we have got a new message while previous is not complete
m_CurrentMessage.deliveryType = (TunnelDeliveryType)((flag >> 5) & 0x03);
switch (m_CurrentMessage.deliveryType)
{
case eDeliveryTypeLocal: // 0
break;
case eDeliveryTypeTunnel: // 1
m_CurrentMessage.tunnelID = bufbe32toh (fragment);
fragment += 4; // tunnelID
m_CurrentMessage.hash = i2p::data::IdentHash (fragment);
fragment += 32; // hash
break;
case eDeliveryTypeRouter: // 2
m_CurrentMessage.hash = i2p::data::IdentHash (fragment);
fragment += 32; // to hash
break;
default: ;
}
bool isFragmented = flag & 0x08;
if (isFragmented)
{
// Message ID
msgID = bufbe32toh (fragment);
fragment += 4;
m_CurrentMsgID = msgID;
isLastFragment = false;
}
}
else
{
// follow on
msgID = bufbe32toh (fragment); // MessageID
fragment += 4;
fragmentNum = (flag >> 1) & 0x3F; // 6 bits
isLastFragment = flag & 0x01;
}
uint16_t size = bufbe16toh (fragment);
fragment += 2;
// handle fragment
if (isFollowOnFragment)
{
// existing message
if (m_CurrentMsgID && m_CurrentMsgID == msgID && m_CurrentMessage.nextFragmentNum == fragmentNum)
HandleCurrenMessageFollowOnFragment (fragment, size, isLastFragment); // previous
else
{
HandleFollowOnFragment (msgID, isLastFragment, fragmentNum, fragment, size); // another
m_CurrentMsgID = 0; m_CurrentMessage.data = nullptr;
}
}
else
{
// new message
msg->offset = fragment - msg->buf;
msg->len = msg->offset + size;
// check message size
if (msg->len > msg->maxLen)
{
LogPrint (eLogError, "TunnelMessage: Fragment is too long ", (int)size);
m_CurrentMsgID = 0; m_CurrentMessage.data = nullptr;
return;
}
// create new or assign I2NP message
if (fragment + size < decrypted + TUNNEL_DATA_ENCRYPTED_SIZE)
{
// this is not last message. we have to copy it
m_CurrentMessage.data = NewI2NPTunnelMessage (true);
*(m_CurrentMessage.data) = *msg;
}
else
m_CurrentMessage.data = msg;
if (isLastFragment)
{
// single message
HandleNextMessage (m_CurrentMessage);
m_CurrentMsgID = 0; m_CurrentMessage.data = nullptr;
}
else if (msgID)
{
// first fragment of a new message
m_CurrentMessage.nextFragmentNum = 1;
m_CurrentMessage.receiveTime = i2p::util::GetMillisecondsSinceEpoch ();
HandleOutOfSequenceFragments (msgID, m_CurrentMessage);
}
else
{
LogPrint (eLogError, "TunnelMessage: Message is fragmented, but msgID is not presented");
m_CurrentMsgID = 0; m_CurrentMessage.data = nullptr;
}
}
fragment += size;
}
}
else
LogPrint (eLogError, "TunnelMessage: Zero not found");
}
void TunnelEndpoint::HandleFollowOnFragment (uint32_t msgID, bool isLastFragment,
uint8_t fragmentNum, const uint8_t * fragment, size_t size)
{
auto it = m_IncompleteMessages.find (msgID);
if (it != m_IncompleteMessages.end())
{
auto& msg = it->second;
if (fragmentNum == msg.nextFragmentNum)
{
if (ConcatFollowOnFragment (msg, fragment, size))
{
if (isLastFragment)
{
// message complete
HandleNextMessage (msg);
m_IncompleteMessages.erase (it);
}
else
{
msg.nextFragmentNum++;
HandleOutOfSequenceFragments (msgID, msg);
}
}
else
{
LogPrint (eLogError, "TunnelMessage: Fragment ", fragmentNum, " of message ", msgID, "exceeds max I2NP message size, message dropped");
m_IncompleteMessages.erase (it);
}
}
else
{
LogPrint (eLogWarning, "TunnelMessage: Unexpected fragment ", (int)fragmentNum, " instead ", (int)msg.nextFragmentNum, " of message ", msgID, ", saved");
AddOutOfSequenceFragment (msgID, fragmentNum, isLastFragment, fragment, size);
}
}
else
{
LogPrint (eLogDebug, "TunnelMessage: First fragment of message ", msgID, " not found, saved");
AddOutOfSequenceFragment (msgID, fragmentNum, isLastFragment, fragment, size);
}
}
bool TunnelEndpoint::ConcatFollowOnFragment (TunnelMessageBlockEx& msg, const uint8_t * fragment, size_t size) const
{
if (msg.data->len + size < I2NP_MAX_MESSAGE_SIZE) // check if message is not too long
{
if (msg.data->len + size > msg.data->maxLen)
{
// LogPrint (eLogWarning, "TunnelMessage: I2NP message size ", msg.data->maxLen, " is not enough");
auto newMsg = NewI2NPMessage (msg.data->len + size);
*newMsg = *(msg.data);
msg.data = newMsg;
}
if (msg.data->Concat (fragment, size) < size) // concatenate fragment
{
LogPrint (eLogError, "TunnelMessage: I2NP buffer overflow ", msg.data->maxLen);
return false;
}
}
else
return false;
return true;
}
void TunnelEndpoint::HandleCurrenMessageFollowOnFragment (const uint8_t * fragment, size_t size, bool isLastFragment)
{
if (ConcatFollowOnFragment (m_CurrentMessage, fragment, size))
{
if (isLastFragment)
{
// message complete
HandleNextMessage (m_CurrentMessage);
m_CurrentMsgID = 0; m_CurrentMessage.data = nullptr;
}
else
{
m_CurrentMessage.nextFragmentNum++;
HandleOutOfSequenceFragments (m_CurrentMsgID, m_CurrentMessage);
}
}
else
{
LogPrint (eLogError, "TunnelMessage: Fragment ", m_CurrentMessage.nextFragmentNum, " of message ", m_CurrentMsgID, " exceeds max I2NP message size, message dropped");
m_CurrentMsgID = 0; m_CurrentMessage.data = nullptr;
}
}
void TunnelEndpoint::AddIncompleteCurrentMessage ()
{
if (m_CurrentMsgID)
{
auto ret = m_IncompleteMessages.emplace (m_CurrentMsgID, m_CurrentMessage);
if (!ret.second)
LogPrint (eLogError, "TunnelMessage: Incomplete message ", m_CurrentMsgID, " already exists");
m_CurrentMessage.data = nullptr;
m_CurrentMsgID = 0;
}
}
void TunnelEndpoint::AddOutOfSequenceFragment (uint32_t msgID, uint8_t fragmentNum,
bool isLastFragment, const uint8_t * fragment, size_t size)
{
std::unique_ptr<Fragment> f(new Fragment (isLastFragment, i2p::util::GetMillisecondsSinceEpoch (), size));
memcpy (f->data.data (), fragment, size);
if (!m_OutOfSequenceFragments.emplace ((uint64_t)msgID << 32 | fragmentNum, std::move (f)).second)
LogPrint (eLogInfo, "TunnelMessage: Duplicate out-of-sequence fragment ", fragmentNum, " of message ", msgID);
}
void TunnelEndpoint::HandleOutOfSequenceFragments (uint32_t msgID, TunnelMessageBlockEx& msg)
{
while (ConcatNextOutOfSequenceFragment (msgID, msg))
{
if (!msg.nextFragmentNum) // message complete
{
HandleNextMessage (msg);
if (&msg == &m_CurrentMessage)
{
m_CurrentMsgID = 0;
m_CurrentMessage.data = nullptr;
}
else
m_IncompleteMessages.erase (msgID);
LogPrint (eLogDebug, "TunnelMessage: All fragments of message ", msgID, " found");
break;
}
}
}
bool TunnelEndpoint::ConcatNextOutOfSequenceFragment (uint32_t msgID, TunnelMessageBlockEx& msg)
{
auto it = m_OutOfSequenceFragments.find ((uint64_t)msgID << 32 | msg.nextFragmentNum);
if (it != m_OutOfSequenceFragments.end ())
{
LogPrint (eLogDebug, "TunnelMessage: Out-of-sequence fragment ", (int)msg.nextFragmentNum, " of message ", msgID, " found");
size_t size = it->second->data.size ();
if (msg.data->len + size > msg.data->maxLen)
{
LogPrint (eLogWarning, "TunnelMessage: Tunnel endpoint I2NP message size ", msg.data->maxLen, " is not enough");
auto newMsg = NewI2NPMessage (msg.data->len + size);
*newMsg = *(msg.data);
msg.data = newMsg;
}
if (msg.data->Concat (it->second->data.data (), size) < size) // concatenate out-of-sync fragment
LogPrint (eLogError, "TunnelMessage: Tunnel endpoint I2NP buffer overflow ", msg.data->maxLen);
if (it->second->isLastFragment)
// message complete
msg.nextFragmentNum = 0;
else
msg.nextFragmentNum++;
m_OutOfSequenceFragments.erase (it);
return true;
}
return false;
}
void TunnelEndpoint::HandleNextMessage (const TunnelMessageBlock& msg)
{
if (!m_IsInbound && msg.data->IsExpired ())
{
LogPrint (eLogInfo, "TunnelMessage: Message expired");
return;
}
uint8_t typeID = msg.data->GetTypeID ();
LogPrint (eLogDebug, "TunnelMessage: Handle fragment of ", msg.data->GetLength (), " bytes, msg type ", (int)typeID);
switch (msg.deliveryType)
{
case eDeliveryTypeLocal:
i2p::HandleI2NPMessage (msg.data);
break;
case eDeliveryTypeTunnel:
if (!m_IsInbound) // outbound transit tunnel
SendMessageTo (msg.hash, i2p::CreateTunnelGatewayMsg (msg.tunnelID, msg.data));
else
LogPrint (eLogError, "TunnelMessage: Delivery type 'tunnel' arrived from an inbound tunnel, dropped");
break;
case eDeliveryTypeRouter:
if (!m_IsInbound) // outbound transit tunnel
i2p::transport::transports.SendMessage (msg.hash, msg.data); // send right away, because most likely it's single message
else // we shouldn't send this message. possible leakage
LogPrint (eLogError, "TunnelMessage: Delivery type 'router' arrived from an inbound tunnel, dropped");
break;
default:
LogPrint (eLogError, "TunnelMessage: Unknown delivery type ", (int)msg.deliveryType);
};
}
void TunnelEndpoint::Cleanup ()
{
auto ts = i2p::util::GetMillisecondsSinceEpoch ();
// out-of-sequence fragments
for (auto it = m_OutOfSequenceFragments.begin (); it != m_OutOfSequenceFragments.end ();)
{
if (ts > it->second->receiveTime + i2p::I2NP_MESSAGE_EXPIRATION_TIMEOUT)
it = m_OutOfSequenceFragments.erase (it);
else
++it;
}
// incomplete messages
for (auto it = m_IncompleteMessages.begin (); it != m_IncompleteMessages.end ();)
{
if (ts > it->second.receiveTime + i2p::I2NP_MESSAGE_EXPIRATION_TIMEOUT)
it = m_IncompleteMessages.erase (it);
else
++it;
}
}
void TunnelEndpoint::SendMessageTo (const i2p::data::IdentHash& to, std::shared_ptr<i2p::I2NPMessage> msg)
{
if (msg)
{
if (!m_Sender && m_I2NPMsgs.empty ()) // first message
m_CurrentHash = to;
else if (m_CurrentHash != to) // new target router
{
FlushI2NPMsgs (); // flush message to previous
if (m_Sender) m_Sender->Reset (); // reset sender
m_CurrentHash = to; // set new target router
} // otherwise add msg to the list for current target router
m_I2NPMsgs.push_back (msg);
}
}
void TunnelEndpoint::FlushI2NPMsgs ()
{
if (!m_I2NPMsgs.empty ())
{
if (!m_Sender) m_Sender = std::make_unique<TunnelTransportSender>();
m_Sender->SendMessagesTo (m_CurrentHash, m_I2NPMsgs); // send and clear
}
}
const i2p::data::IdentHash * TunnelEndpoint::GetCurrentHash () const
{
return (m_Sender || !m_I2NPMsgs.empty ()) ? &m_CurrentHash : nullptr;
}
}
}