I2P: End-to-End encrypted and anonymous Internet https://i2pd.website/
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#include <string.h>
#include <boost/bind.hpp>
#include <cryptopp/dh.h>
#include <cryptopp/secblock.h>
#include "CryptoConst.h"
#include "Log.h"
#include "Timestamp.h"
#include "RouterContext.h"
#include "hmac.h"
#include "SSU.h"
namespace i2p
{
namespace ssu
{
SSUSession::SSUSession (SSUServer * server, const boost::asio::ip::udp::endpoint& remoteEndpoint,
i2p::data::RouterInfo * router): m_Server (server), m_RemoteEndpoint (remoteEndpoint),
m_RemoteRouter (router), m_State (eSessionStateUnknown)
{
}
void SSUSession::CreateAESKey (uint8_t * pubKey, uint8_t * aesKey) // TODO: move it to base class for NTCP and SSU
{
CryptoPP::DH dh (i2p::crypto::elgp, i2p::crypto::elgg);
CryptoPP::SecByteBlock secretKey(dh.AgreedValueLength());
if (!dh.Agree (secretKey, i2p::context.GetPrivateKey (), pubKey))
{
LogPrint ("Couldn't create shared key");
return;
};
if (secretKey[0] & 0x80)
{
aesKey[0] = 0;
memcpy (aesKey + 1, secretKey, 31);
}
else
memcpy (aesKey, secretKey, 32);
}
void SSUSession::ProcessNextMessage (uint8_t * buf, size_t len, const boost::asio::ip::udp::endpoint& senderEndpoint)
{
switch (m_State)
{
case eSessionStateUnknown:
// session request
ProcessSessionRequest (buf, len, senderEndpoint);
break;
case eSessionStateRequestSent:
// session created
ProcessSessionCreated (buf, len);
break;
default:
LogPrint ("SSU state not implemented yet");
}
}
void SSUSession::ProcessSessionRequest (uint8_t * buf, size_t len, const boost::asio::ip::udp::endpoint& senderEndpoint)
{
LogPrint ("Process session request");
if (ProcessIntroKeyEncryptedMessage (PAYLOAD_TYPE_SESSION_REQUEST, buf, len))
{
m_State = eSessionStateRequestReceived;
LogPrint ("Session request received");
SendSessionCreated (senderEndpoint);
}
}
void SSUSession::ProcessSessionCreated (uint8_t * buf, size_t len)
{
LogPrint ("Process session created");
if (ProcessIntroKeyEncryptedMessage (PAYLOAD_TYPE_SESSION_CREATED, buf, len))
{
m_State = eSessionStateCreatedReceived;
LogPrint ("Session request received");
// TODO:
}
}
void SSUSession::SendSessionRequest ()
{
auto address = m_RemoteRouter ? m_RemoteRouter->GetSSUAddress () : nullptr;
if (!address)
{
LogPrint ("Missing remote SSU address");
return;
}
uint8_t buf[304 + 18]; // 304 bytes for ipv4 (320 for ipv6)
uint8_t * payload = buf + sizeof (SSUHeader);
memcpy (payload, i2p::context.GetRouterIdentity ().publicKey, 256);
payload[256] = 4; // we assume ipv4
*(uint32_t *)(payload + 257) = address->host.to_v4 ().to_ulong (); // network bytes order already
uint8_t iv[16];
CryptoPP::RandomNumberGenerator& rnd = i2p::context.GetRandomNumberGenerator ();
rnd.GenerateBlock (iv, 16); // random iv
FillHeaderAndEncrypt (PAYLOAD_TYPE_SESSION_REQUEST, buf, 304, address->key, iv, address->key);
m_State = eSessionStateRequestSent;
m_Server->Send (buf, 304, m_RemoteEndpoint);
}
void SSUSession::SendSessionCreated (const boost::asio::ip::udp::endpoint& senderEndpoint)
{
auto address = m_RemoteRouter ? m_RemoteRouter->GetSSUAddress () : nullptr;
if (!address)
{
LogPrint ("Missing remote SSU address");
return;
}
uint8_t buf[368 + 18];
uint8_t * payload = buf + sizeof (SSUHeader);
memcpy (payload, i2p::context.GetRouterIdentity ().publicKey, 256);
m_State = eSessionStateRequestSent;
m_Server->Send (buf, 368, m_RemoteEndpoint);
}
bool SSUSession::ProcessIntroKeyEncryptedMessage (uint8_t expectedPayloadType, uint8_t * buf, size_t len)
{
auto address = i2p::context.GetRouterInfo ().GetSSUAddress ();
if (address)
{
// use intro key for verification and decryption
if (Validate (buf, len, address->key))
{
Decrypt (buf, len, address->key);
SSUHeader * header = (SSUHeader *)buf;
if ((header->flag >> 4) == expectedPayloadType)
{
CreateAESKey (buf + sizeof (SSUHeader), m_SessionKey);
return true;
}
else
LogPrint ("Unexpected payload type ", (int)(header->flag >> 4));
}
else
LogPrint ("MAC verifcation failed");
}
else
LogPrint ("SSU is not supported");
return false;
}
void SSUSession::FillHeaderAndEncrypt (uint8_t payloadType, uint8_t * buf, size_t len, uint8_t * aesKey, uint8_t * iv, uint8_t * macKey)
{
if (len < sizeof (SSUHeader))
{
LogPrint ("Unexpected SSU packet length ", len);
return;
}
SSUHeader * header = (SSUHeader *)buf;
memcpy (header->iv, iv, 16);
header->flag = payloadType << 4; // MSB is 0
header->time = htobe32 (i2p::util::GetSecondsSinceEpoch ());
uint8_t * encrypted = &header->flag;
uint16_t encryptedLen = len - (encrypted - buf);
m_Encryption.SetKeyWithIV (aesKey, 32, iv);
m_Encryption.ProcessData (encrypted, encrypted, encryptedLen);
// assume actual buffer size is 18 (16 + 2) bytes more
memcpy (buf + len, iv, 16);
*(uint16_t *)(buf + len + 16) = htobe16 (encryptedLen);
i2p::crypto::HMACMD5Digest (encrypted, encryptedLen + 18, macKey, header->mac);
}
void SSUSession::Decrypt (uint8_t * buf, size_t len, uint8_t * aesKey)
{
if (len < sizeof (SSUHeader))
{
LogPrint ("Unexpected SSU packet length ", len);
return;
}
SSUHeader * header = (SSUHeader *)buf;
uint8_t * encrypted = &header->flag;
uint16_t encryptedLen = len - (encrypted - buf);
m_Decryption.SetKeyWithIV (aesKey, 32, header->iv);
m_Decryption.ProcessData (encrypted, encrypted, encryptedLen);
}
bool SSUSession::Validate (uint8_t * buf, size_t len, uint8_t * macKey)
{
if (len < sizeof (SSUHeader))
{
LogPrint ("Unexpected SSU packet length ", len);
return false;
}
SSUHeader * header = (SSUHeader *)buf;
uint8_t * encrypted = &header->flag;
uint16_t encryptedLen = len - (encrypted - buf);
// assume actual buffer size is 18 (16 + 2) bytes more
memcpy (buf + len, header->iv, 16);
*(uint16_t *)(buf + len + 16) = htobe16 (encryptedLen);
uint8_t digest[16];
i2p::crypto::HMACMD5Digest (encrypted, encryptedLen + 18, macKey, digest);
return !memcmp (header->mac, digest, 16);
}
void SSUSession::Connect ()
{
SendSessionRequest ();
}
void SSUSession::SendI2NPMessage (I2NPMessage * msg)
{
// TODO:
}
SSUServer::SSUServer (boost::asio::io_service& service, int port):
m_Socket (service, boost::asio::ip::udp::endpoint (boost::asio::ip::udp::v4 (), port))
{
}
SSUServer::~SSUServer ()
{
for (auto it: m_Sessions)
delete it.second;
}
void SSUServer::Start ()
{
Receive ();
}
void SSUServer::Stop ()
{
m_Socket.close ();
}
void SSUServer::Send (uint8_t * buf, size_t len, const boost::asio::ip::udp::endpoint& to)
{
m_Socket.send_to (boost::asio::buffer (buf, len), to);
}
void SSUServer::Receive ()
{
m_Socket.async_receive_from (boost::asio::buffer (m_ReceiveBuffer, SSU_MTU), m_SenderEndpoint,
boost::bind (&SSUServer::HandleReceivedFrom, this, boost::asio::placeholders::error, boost::asio::placeholders::bytes_transferred));
}
void SSUServer::HandleReceivedFrom (const boost::system::error_code& ecode, std::size_t bytes_transferred)
{
if (!ecode)
{
LogPrint ("SSU received ", bytes_transferred, " bytes");
SSUSession * session = nullptr;
auto it = m_Sessions.find (m_SenderEndpoint);
if (it != m_Sessions.end ())
session = it->second;
if (!session)
{
session = new SSUSession (this, m_SenderEndpoint);
m_Sessions[m_SenderEndpoint] = session;
LogPrint ("New SSU session from ", m_SenderEndpoint.address ().to_string (), ":", m_SenderEndpoint.port (), " created");
}
session->ProcessNextMessage (m_ReceiveBuffer, bytes_transferred, m_SenderEndpoint);
Receive ();
}
else
LogPrint ("SSU receive error: ", ecode.message ());
}
SSUSession * SSUServer::GetSession (i2p::data::RouterInfo * router)
{
SSUSession * session = nullptr;
if (router)
{
auto address = router->GetSSUAddress ();
if (address)
{
boost::asio::ip::udp::endpoint remoteEndpoint (address->host, address->port);
auto it = m_Sessions.find (remoteEndpoint);
if (it != m_Sessions.end ())
session = it->second;
else
{
// otherwise create new session
session = new SSUSession (this, remoteEndpoint, router);
m_Sessions[remoteEndpoint] = session;
LogPrint ("New SSU session to [", router->GetIdentHashAbbreviation (), "] ",
remoteEndpoint.address ().to_string (), ":", remoteEndpoint.port (), " created");
session->Connect ();
}
}
else
LogPrint ("Router ", router->GetIdentHashAbbreviation (), " doesn't have SSU address");
}
return session;
}
}
}