I2P: End-to-End encrypted and anonymous Internet https://i2pd.website/
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#include <string.h>
#include <endian.h>
#include <cryptopp/sha.h>
#include "Log.h"
#include "RouterContext.h"
#include "Transports.h"
#include "TunnelGateway.h"
namespace i2p
{
namespace tunnel
{
void TunnelGatewayBuffer::PutI2NPMsg (const uint8_t * gwHash, uint32_t gwTunnel, I2NPMessage * msg)
{
TunnelMessageBlockExt * block = new TunnelMessageBlockExt;
block->deliveryInstructionsLen = 1; // flag
if (gwHash)
{
block->deliveryInstructionsLen += 32; // hash
memcpy (block->hash, gwHash, 32);
if (gwTunnel)
{
block->deliveryType = eDeliveryTypeTunnel;
block->deliveryInstructionsLen += 4; // tunnelID
block->tunnelID = gwTunnel;
}
else
block->deliveryType = eDeliveryTypeRouter;
}
else
block->deliveryType = eDeliveryTypeLocal;
block->deliveryInstructionsLen += 2; // size
// we don't reserve 4 bytes for msgID yet
block->totalLen = block->deliveryInstructionsLen + msg->GetLength ();
block->data = msg;
m_I2NPMsgs.push_back (block);
if (!m_Remaining) m_Remaining = TUNNEL_DATA_MAX_PAYLOAD_SIZE;
if (block->totalLen <= m_Remaining) // message fits
{
block->isFragmented = false;
m_Remaining -= block->totalLen;
}
else // message doesn't fit
{
if (block->deliveryInstructionsLen + 4 <= m_Remaining)
{
// delivery instructions of first fragment fits
block->isFragmented = true;
block->deliveryInstructionsLen += 4;
block->totalLen += 4;
m_Remaining = m_Remaining + TUNNEL_DATA_MAX_PAYLOAD_SIZE - block->totalLen - 7; // TODO: handle case if more than two fragments
}
else
{
// delivery instructions of first fragment don't fit
block->isFragmented = false;
m_Remaining = 0;
}
}
}
std::vector<I2NPMessage *> TunnelGatewayBuffer::GetTunnelDataMsgs (uint32_t tunnelID)
{
m_Remaining = 0;
m_NextOffset = 0;
std::vector<I2NPMessage *> res;
int cnt = m_I2NPMsgs.size ();
if (cnt > 0)
{
int ind = 0;
while (ind < cnt)
{
auto tunnelMsg = CreateNextTunnelMessage (tunnelID, ind);
if (!tunnelMsg) break;
res.push_back (tunnelMsg);
}
for (auto msg: m_I2NPMsgs)
delete msg;
m_I2NPMsgs.clear ();
}
return res;
}
size_t TunnelGatewayBuffer::CreateFirstFragment (TunnelMessageBlockExt * block, uint8_t * buf, size_t len)
{
size_t ret = 1;
buf[0] = block->deliveryType << 5; // flag
if (block->deliveryType == eDeliveryTypeTunnel)
{
*(uint32_t *)(buf + ret) = htobe32 (block->tunnelID);
ret += 4;
}
if (block->deliveryType == eDeliveryTypeTunnel || block->deliveryType == eDeliveryTypeRouter)
{
memcpy (buf + ret, block->hash, 32);
ret += 32;
}
size_t size = block->data->GetLength ();
if (block->totalLen > len) // entire message doesn't fit
{
buf[0] |= 0x08; // set fragmented bit
m_NextMsgID = block->data->GetHeader ()->msgID;
*(uint32_t *)(buf + ret) = m_NextMsgID;
ret += 4; // msgID
m_NextSeqn = 1;
size = len - ret - 2; // 2 bytes for size field
m_NextOffset = size;
}
*(uint16_t *)(buf + ret) = htobe16 (size); // size
ret += 2;
memcpy (buf + ret, block->data->GetBuffer (), size);
ret += size;
return ret;
}
size_t TunnelGatewayBuffer::CreateFollowOnFragment (TunnelMessageBlockExt * block, uint8_t * buf, size_t len)
{
int ret = 0;
buf[0] = 0x80 | (m_NextSeqn << 1);// follow-on flag and seqn
size_t fragmentLen = len - 7; // 7 bytes of header
if (fragmentLen >= block->data->GetLength () - m_NextOffset)
{
// fragment fits
fragmentLen = block->data->GetLength () - m_NextOffset;
buf[0] |= 0x01; // last fragment
}
else
m_NextSeqn++;
*(uint32_t *)(buf + 1) = m_NextMsgID; // msgID
*(uint16_t *)(buf + 5) = htobe16 (fragmentLen); // size
memcpy (buf + 7, block->data->GetBuffer () + m_NextOffset, fragmentLen);
m_NextOffset += fragmentLen;
ret += fragmentLen + 7;
return ret;
}
I2NPMessage * TunnelGatewayBuffer::CreateNextTunnelMessage (uint32_t tunnelID, int& ind)
{
int cnt = m_I2NPMsgs.size ();
if (ind > cnt - 1) return nullptr; // no more messages
// calculate payload size
size_t size = 0;
int i = ind;
if (m_NextOffset)
{
size = m_I2NPMsgs[i]->data->GetLength () - m_NextOffset + 7; // including follow-on header
i++;
}
while (i < cnt)
{
auto msg = m_I2NPMsgs[i];
size += msg->totalLen;
if (size >= TUNNEL_DATA_MAX_PAYLOAD_SIZE)
{
size = TUNNEL_DATA_MAX_PAYLOAD_SIZE;
break;
}
if (msg->isFragmented) break;
i++;
}
I2NPMessage * tunnelMsg = NewI2NPMessage ();
uint8_t * buf = tunnelMsg->GetPayload ();
*(uint32_t *)(buf) = htobe32 (tunnelID);
CryptoPP::RandomNumberGenerator& rnd = i2p::context.GetRandomNumberGenerator ();
rnd.GenerateBlock (buf + 4, 16); // original IV
memcpy (buf + TUNNEL_DATA_MSG_SIZE, buf + 4, 16); // copy IV for checksum
size_t zero = TUNNEL_DATA_MSG_SIZE - size -1;
buf[zero] = 0; // zero
size_t s = 0;
while (ind < cnt)
{
auto msg = m_I2NPMsgs[ind];
if (m_NextOffset)
{
s += CreateFollowOnFragment (msg, buf + zero + 1 + s, size - s);
m_NextOffset = 0; // TODO:
}
else
{
s += CreateFirstFragment (msg, buf + zero + 1 + s, size - s);
if (msg->isFragmented) break; // payload is full, but we stay at the same message
}
ind++;
if (s >= size) break; // payload is full but we moved to next message
}
if (s != size)
{
LogPrint ("TunnelData payload size mismatch ", s, "!=", size);
return nullptr;
}
uint8_t hash[32];
CryptoPP::SHA256().CalculateDigest(hash, buf+zero+1, size+16);
memcpy (buf+20, hash, 4); // checksum
if (zero > 24)
memset (buf+24, 1, zero-24); // padding TODO: fill with random data
tunnelMsg->len += TUNNEL_DATA_MSG_SIZE;
// we can't fill message header yet because encryption is required
return tunnelMsg;
}
void TunnelGateway::SendTunnelDataMsg (const uint8_t * gwHash, uint32_t gwTunnel, i2p::I2NPMessage * msg)
{
PutTunnelDataMsg (gwHash, gwTunnel, msg);
SendBuffer ();
}
void TunnelGateway::PutTunnelDataMsg (const uint8_t * gwHash, uint32_t gwTunnel, i2p::I2NPMessage * msg)
{
m_Buffer.PutI2NPMsg (gwHash, gwTunnel, msg);
}
void TunnelGateway::SendBuffer ()
{
auto tunnelMsgs = m_Buffer.GetTunnelDataMsgs (m_Tunnel->GetNextTunnelID ());
for (auto tunnelMsg : tunnelMsgs)
{
m_Tunnel->EncryptTunnelMsg (tunnelMsg);
FillI2NPMessageHeader (tunnelMsg, eI2NPTunnelData);
i2p::transports.SendMessage (m_Tunnel->GetNextIdentHash (), tunnelMsg);
}
}
}
}