I2P: End-to-End encrypted and anonymous Internet https://i2pd.website/
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#include "I2PEndian.h"
#include <string.h>
#include "Log.h"
#include "I2NPProtocol.h"
#include "Transports.h"
#include "TunnelEndpoint.h"
namespace i2p
{
namespace tunnel
{
void TunnelEndpoint::HandleDecryptedTunnelDataMsg (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); // witout 4-byte checksum
if (zero)
{
LogPrint ("TunnelMessage: zero found at ", (int)(zero-decrypted));
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];
CryptoPP::SHA256().CalculateDigest (hash, fragment, TUNNEL_DATA_MSG_SIZE -(fragment - msg->GetPayload ()) + 16); // payload + iv
if (memcmp (hash, decrypted, 4))
{
LogPrint ("TunnelMessage: checksum verification failed");
i2p::DeleteI2NPMessage (msg);
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;
TunnelMessageBlockEx m;
if (!isFollowOnFragment)
{
// first fragment
m.deliveryType = (TunnelDeliveryType)((flag >> 5) & 0x03);
switch (m.deliveryType)
{
case eDeliveryTypeLocal: // 0
LogPrint ("Delivery type local");
break;
case eDeliveryTypeTunnel: // 1
LogPrint ("Delivery type tunnel");
m.tunnelID = be32toh (*(uint32_t *)fragment);
fragment += 4; // tunnelID
m.hash = i2p::data::IdentHash (fragment);
fragment += 32; // hash
break;
case eDeliveryTypeRouter: // 2
LogPrint ("Delivery type router");
m.hash = i2p::data::IdentHash (fragment);
fragment += 32; // to hash
break;
default:
;
}
bool isFragmented = flag & 0x08;
if (isFragmented)
{
// Message ID
msgID = be32toh (*(uint32_t *)fragment);
fragment += 4;
LogPrint ("Fragmented message ", msgID);
isLastFragment = false;
}
}
else
{
// follow on
msgID = be32toh (*(uint32_t *)fragment); // MessageID
fragment += 4;
fragmentNum = (flag >> 1) & 0x3F; // 6 bits
isLastFragment = flag & 0x01;
LogPrint ("Follow on fragment ", fragmentNum, " of message ", msgID, isLastFragment ? " last" : " non-last");
}
uint16_t size = be16toh (*(uint16_t *)fragment);
fragment += 2;
LogPrint ("Fragment size=", (int)size);
msg->offset = fragment - msg->buf;
msg->len = msg->offset + size;
bool isLastMessage = false;
if (fragment + size < decrypted + TUNNEL_DATA_ENCRYPTED_SIZE)
{
// this is not last message. we have to copy it
m.data = NewI2NPMessage ();
m.data->offset += sizeof (TunnelGatewayHeader); // reserve room for TunnelGateway header
m.data->len += sizeof (TunnelGatewayHeader);
*(m.data) = *msg;
}
else
{
m.data = msg;
isLastMessage = true;
}
if (!isFollowOnFragment && isLastFragment)
HandleNextMessage (m);
else
{
if (msgID) // msgID is presented, assume message is fragmented
{
if (!isFollowOnFragment) // create new incomlete message
{
m.nextFragmentNum = 1;
m_IncompleteMessages[msgID] = m;
}
else
{
auto it = m_IncompleteMessages.find (msgID);
if (it != m_IncompleteMessages.end())
{
if (fragmentNum == it->second.nextFragmentNum)
{
I2NPMessage * incompleteMessage = it->second.data;
memcpy (incompleteMessage->buf + incompleteMessage->len, fragment, size); // concatenate fragment
incompleteMessage->len += size;
if (isLastFragment)
{
// message complete
HandleNextMessage (it->second);
m_IncompleteMessages.erase (it);
}
else
it->second.nextFragmentNum++;
}
else
{
LogPrint ("Unexpected fragment ", fragmentNum, " instead ", it->second.nextFragmentNum, " of message ", msgID, ". Discarded");
m_IncompleteMessages.erase (it); // TODO: store unexpect fragment for a while
}
}
else
LogPrint ("First fragment of message ", msgID, " not found. Discarded");
if (isLastMessage)
// last message is follow-on fragment
// not passed to anywhere because first fragment
i2p::DeleteI2NPMessage (msg);
}
}
else
LogPrint ("Message is fragmented, but msgID is not presented");
}
fragment += size;
}
}
else
{
LogPrint ("TunnelMessage: zero not found");
i2p::DeleteI2NPMessage (msg);
}
}
void TunnelEndpoint::HandleNextMessage (const TunnelMessageBlock& msg)
{
LogPrint ("TunnelMessage: handle fragment of ", msg.data->GetLength ()," bytes. Msg type ", (int)msg.data->GetHeader()->typeID);
switch (msg.deliveryType)
{
case eDeliveryTypeLocal:
i2p::HandleI2NPMessage (msg.data);
break;
case eDeliveryTypeTunnel:
i2p::transports.SendMessage (msg.hash, i2p::CreateTunnelGatewayMsg (msg.tunnelID, msg.data));
break;
case eDeliveryTypeRouter:
i2p::transports.SendMessage (msg.hash, msg.data);
break;
default:
LogPrint ("TunnelMessage: Unknown delivery type ", (int)msg.deliveryType);
};
}
}
}