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"
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#include "RouterContext.h"
#include "Transports.h"
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#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
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// we don't reserve 4 bytes for msgID because we don't if it fits
block->totalLen = block->deliveryInstructionsLen + msg->GetLength ();
block->data = msg;
m_I2NPMsgs.push_back (block);
}
std::vector<I2NPMessage *> TunnelGatewayBuffer::GetTunnelDataMsgs (uint32_t tunnelID)
{
std::vector<I2NPMessage *> res;
int cnt = m_I2NPMsgs.size ();
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m_NextOffset = 0;
if (cnt > 0)
{
for (auto m: m_I2NPMsgs)
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{
if (m->totalLen <= 1003)
res.push_back (CreateNextTunnelMessage (tunnelID, m, m->totalLen));
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else
{
res.push_back (CreateNextTunnelMessage (tunnelID, m, 1003));
size_t remaining = m->data->GetLength () - m_NextOffset; // remaining payload
remaining += 7; // follow-on header
res.push_back (CreateNextTunnelMessage (tunnelID, m, remaining));
}
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delete m;
}
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m_I2NPMsgs.clear ();
}
return res;
}
size_t TunnelGatewayBuffer::CreateFirstFragment (TunnelMessageBlockExt * block, uint8_t * buf, size_t len)
{
if (block->deliveryInstructionsLen > len) return 0; // can't put even delivery instructions
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
{
if (ret + 4 > len) return 0; // can't put delivery instructions with msgID
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
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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)
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{
// fragment fits
fragmentLen = block->data->GetLength () - m_NextOffset;
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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,
TunnelMessageBlockExt * block, size_t size)
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{
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 + 1028, buf + 4, 16); // copy IV for checksum
size_t zero = 1028 - size -1;
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buf[zero] = 0; // zero
if (m_NextOffset)
{
size_t s = CreateFollowOnFragment (block, buf + zero + 1, 1003);
if (s != size)
LogPrint ("Follow-on fragment size mismatch ", s, "!=", size);
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}
else
CreateFirstFragment (block, buf + zero + 1, 1003);
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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
tunnelMsg->len += 1028;
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// 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)
{
m_Buffer.PutI2NPMsg (gwHash, gwTunnel, msg);
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);
}
}
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}
}