i2pd/SOCKS.cpp

#include <cstring>
#include <cassert>
#include <string>
#include <atomic>
#include "SOCKS.h"
#include "Identity.h"
#include "Streaming.h"
#include "Destination.h"
#include "ClientContext.h"
#include "I2PEndian.h"
#include "I2PTunnel.h"

namespace i2p
{
namespace proxy
{
	static const size_t socks_buffer_size = 8192;
	static const size_t max_socks_hostname_size = 255; // Limit for socks5 and bad idea to traverse

	struct SOCKSDnsAddress 
	{
		uint8_t size;
		char value[max_socks_hostname_size];
		void FromString (std::string str) 
		{
			size = str.length();
			if (str.length() > max_socks_hostname_size) size = max_socks_hostname_size;
			memcpy(value,str.c_str(),size);
		}
		std::string ToString() { return std::string(value, size); }
		void push_back (char c) { value[size++] = c; }
	};

	class SOCKSServer;
	class SOCKSHandler: public i2p::client::I2PServiceHandler, public std::enable_shared_from_this<SOCKSHandler> 
	{
		private:
			enum state 
			{
				GET_SOCKSV,
				GET_COMMAND,
				GET_PORT,
				GET_IPV4,
				GET4_IDENT,
				GET4A_HOST,
				GET5_AUTHNUM,
				GET5_AUTH,
				GET5_REQUESTV,
				GET5_GETRSV,
				GET5_GETADDRTYPE,
				GET5_IPV6,
				GET5_HOST_SIZE,
				GET5_HOST,
				DONE
			};
			enum authMethods 
			{
				AUTH_NONE = 0, //No authentication, skip to next step
				AUTH_GSSAPI = 1, //GSSAPI authentication
				AUTH_USERPASSWD = 2, //Username and password
				AUTH_UNACCEPTABLE = 0xff //No acceptable method found
			};
			enum addrTypes 
			{
				ADDR_IPV4 = 1, //IPv4 address (4 octets)
				ADDR_DNS = 3, // DNS name (up to 255 octets)
				ADDR_IPV6 = 4 //IPV6 address (16 octets)
			};
			enum errTypes 
			{
				SOCKS5_OK = 0, // No error for SOCKS5
				SOCKS5_GEN_FAIL = 1, // General server failure
				SOCKS5_RULE_DENIED = 2, // Connection disallowed by ruleset
				SOCKS5_NET_UNREACH = 3, // Network unreachable
				SOCKS5_HOST_UNREACH = 4, // Host unreachable
				SOCKS5_CONN_REFUSED = 5, // Connection refused by the peer
				SOCKS5_TTL_EXPIRED = 6, // TTL Expired
				SOCKS5_CMD_UNSUP = 7, // Command unsuported
				SOCKS5_ADDR_UNSUP = 8, // Address type unsuported
				SOCKS4_OK = 90, // No error for SOCKS4
				SOCKS4_FAIL = 91, // Failed establishing connecting or not allowed
				SOCKS4_IDENTD_MISSING = 92, // Couldn't connect to the identd server
				SOCKS4_IDENTD_DIFFER = 93 // The ID reported by the application and by identd differ
			};
			enum cmdTypes 
			{
				CMD_CONNECT = 1, // TCP Connect
				CMD_BIND = 2, // TCP Bind
				CMD_UDP = 3 // UDP associate
			};
			enum socksVersions 
			{
				SOCKS4 = 4, // SOCKS4
				SOCKS5 = 5 // SOCKS5
			};
			union address 
			{
				uint32_t ip;
				SOCKSDnsAddress dns;
				uint8_t ipv6[16];
			};

			void EnterState(state nstate, uint8_t parseleft = 1);
			bool HandleData(uint8_t *sock_buff, std::size_t len);
			bool ValidateSOCKSRequest();
			void HandleSockRecv(const boost::system::error_code & ecode, std::size_t bytes_transfered);
			void Terminate();
			void AsyncSockRead();
			boost::asio::const_buffers_1 GenerateSOCKS5SelectAuth(authMethods method);
			boost::asio::const_buffers_1 GenerateSOCKS4Response(errTypes error, uint32_t ip, uint16_t port);
			boost::asio::const_buffers_1 GenerateSOCKS5Response(errTypes error, addrTypes type, const address &addr, uint16_t port);
			bool Socks5ChooseAuth();
			void SocksRequestFailed(errTypes error);
			void SocksRequestSuccess();
			void SentSocksFailed(const boost::system::error_code & ecode);
			void SentSocksDone(const boost::system::error_code & ecode);
			void SentSocksResponse(const boost::system::error_code & ecode);
			void HandleStreamRequestComplete (std::shared_ptr<i2p::stream::Stream> stream);

			uint8_t m_sock_buff[socks_buffer_size];
			std::shared_ptr<boost::asio::ip::tcp::socket> m_sock;
			std::shared_ptr<i2p::stream::Stream> m_stream;
			uint8_t *m_remaining_data; //Data left to be sent
			uint8_t m_response[7+max_socks_hostname_size];
			address m_address; //Address
			std::size_t m_remaining_data_len; //Size of the data left to be sent
			uint32_t m_4aip; //Used in 4a requests
			uint16_t m_port;
			uint8_t m_command;
			uint8_t m_parseleft; //Octets left to parse
			authMethods m_authchosen; //Authentication chosen
			addrTypes m_addrtype; //Address type chosen
			socksVersions m_socksv; //Socks version
			cmdTypes m_cmd; // Command requested
			state m_state;

		public:
			SOCKSHandler(SOCKSServer * parent, std::shared_ptr<boost::asio::ip::tcp::socket> sock) :
				I2PServiceHandler(parent), m_sock(sock), m_stream(nullptr),
				m_authchosen(AUTH_UNACCEPTABLE), m_addrtype(ADDR_IPV4)
				{ m_address.ip = 0; EnterState(GET_SOCKSV); }
			~SOCKSHandler() { Terminate(); }
			void Handle() { AsyncSockRead(); }
	};

	void SOCKSHandler::AsyncSockRead()
	{
		LogPrint(eLogDebug, "SOCKS: async sock read");
		if (m_sock) {
			m_sock->async_receive(boost::asio::buffer(m_sock_buff, socks_buffer_size),
						std::bind(&SOCKSHandler::HandleSockRecv, shared_from_this(),
								std::placeholders::_1, std::placeholders::_2));
		} else {
			LogPrint(eLogError,"SOCKS: no socket for read");
		}
	}

	void SOCKSHandler::Terminate() 
	{
		if (Kill()) return;
		if (m_sock) 
		{
			LogPrint(eLogDebug, "SOCKS: closing socket");
			m_sock->close();
			m_sock = nullptr;
		}
		if (m_stream) 
		{
			LogPrint(eLogDebug, "SOCKS: closing stream");
			m_stream.reset ();
		}
		Done(shared_from_this());
	}

	boost::asio::const_buffers_1 SOCKSHandler::GenerateSOCKS4Response(SOCKSHandler::errTypes error, uint32_t ip, uint16_t port)
	{
		assert(error >= SOCKS4_OK);
		m_response[0] = '\x00'; //Version
		m_response[1] = error; //Response code
		htobe16buf(m_response+2,port); //Port
		htobe32buf(m_response+4,ip); //IP
		return boost::asio::const_buffers_1(m_response,8);
	}

	boost::asio::const_buffers_1 SOCKSHandler::GenerateSOCKS5Response(SOCKSHandler::errTypes error, SOCKSHandler::addrTypes type, const SOCKSHandler::address &addr, uint16_t port)
	{
		size_t size = 6;
		assert(error <= SOCKS5_ADDR_UNSUP);
		m_response[0] = '\x05'; //Version
		m_response[1] = error; //Response code
		m_response[2] = '\x00'; //RSV
		m_response[3] = type; //Address type
		switch (type) 
		{
			case ADDR_IPV4:
				size = 10;
				htobe32buf(m_response+4,addr.ip);
				break;
			case ADDR_IPV6:
				size = 22;
				memcpy(m_response+4,addr.ipv6, 16);
				break;
			case ADDR_DNS:
				size = 7+addr.dns.size;
				m_response[4] = addr.dns.size;
				memcpy(m_response+5,addr.dns.value, addr.dns.size);
				break;
		}
		htobe16buf(m_response+size-2,port); //Port
		return boost::asio::const_buffers_1(m_response,size);
	}

	bool SOCKSHandler::Socks5ChooseAuth()
	{
		m_response[0] = '\x05'; //Version
		m_response[1] = m_authchosen; //Response code
		boost::asio::const_buffers_1 response(m_response,2);
		if (m_authchosen == AUTH_UNACCEPTABLE) 
		{
			LogPrint(eLogWarning, "SOCKS: v5 authentication negotiation failed");
			boost::asio::async_write(*m_sock, response, std::bind(&SOCKSHandler::SentSocksFailed,
									      shared_from_this(), std::placeholders::_1));
			return false;
		} 
		else 
		{
			LogPrint(eLogDebug, "SOCKS: v5 choosing authentication method: ", m_authchosen);
			boost::asio::async_write(*m_sock, response, std::bind(&SOCKSHandler::SentSocksResponse,
									      shared_from_this(), std::placeholders::_1));
			return true;
		}
	}

	/* All hope is lost beyond this point */
	void SOCKSHandler::SocksRequestFailed(SOCKSHandler::errTypes error)
	{
		boost::asio::const_buffers_1 response(nullptr,0);
		assert(error != SOCKS4_OK && error != SOCKS5_OK);
		switch (m_socksv) 
		{
			case SOCKS4:
				LogPrint(eLogWarning, "SOCKS: v4 request failed: ", error);
				if (error < SOCKS4_OK) error = SOCKS4_FAIL; //Transparently map SOCKS5 errors
				response = GenerateSOCKS4Response(error, m_4aip, m_port);
			break;
			case SOCKS5:
				LogPrint(eLogWarning, "SOCKS: v5 request failed: ", error);
				response = GenerateSOCKS5Response(error, m_addrtype, m_address, m_port);
			break;
		}
		boost::asio::async_write(*m_sock, response, std::bind(&SOCKSHandler::SentSocksFailed,
								      shared_from_this(), std::placeholders::_1));
	}

	void SOCKSHandler::SocksRequestSuccess()
	{
		boost::asio::const_buffers_1 response(nullptr,0);
		//TODO: this should depend on things like the command type and callbacks may change
		switch (m_socksv) 
		{
			case SOCKS4:
				LogPrint(eLogInfo, "SOCKS: v4 connection success");
				response = GenerateSOCKS4Response(SOCKS4_OK, m_4aip, m_port);
			break;
			case SOCKS5:
				LogPrint(eLogInfo, "SOCKS: v5 connection success");
				auto s = i2p::client::context.GetAddressBook().ToAddress(GetOwner()->GetLocalDestination()->GetIdentHash());
				address ad; ad.dns.FromString(s);
				//HACK only 16 bits passed in port as SOCKS5 doesn't allow for more
				response = GenerateSOCKS5Response(SOCKS5_OK, ADDR_DNS, ad, m_stream->GetRecvStreamID());
			break;
		}
		boost::asio::async_write(*m_sock, response, std::bind(&SOCKSHandler::SentSocksDone,
								      shared_from_this(), std::placeholders::_1));
	}

	void SOCKSHandler::EnterState(SOCKSHandler::state nstate, uint8_t parseleft) {
		switch (nstate) 
		{
			case GET_PORT: parseleft = 2; break;
			case GET_IPV4: m_addrtype = ADDR_IPV4; m_address.ip = 0; parseleft = 4; break;
			case GET4_IDENT: m_4aip = m_address.ip; break;
			case GET4A_HOST:
			case GET5_HOST: m_addrtype = ADDR_DNS; m_address.dns.size = 0; break;
			case GET5_IPV6: m_addrtype = ADDR_IPV6; parseleft = 16; break;
			default:;
		}
		m_parseleft = parseleft;
		m_state = nstate;
	}

	bool SOCKSHandler::ValidateSOCKSRequest() 
	{
		if ( m_cmd != CMD_CONNECT ) 
		{
			//TODO: we need to support binds and other shit!
			LogPrint(eLogError, "SOCKS: unsupported command: ", m_cmd);
			SocksRequestFailed(SOCKS5_CMD_UNSUP);
			return false;
		}
		//TODO: we may want to support other address types!
		if ( m_addrtype != ADDR_DNS ) 
		{
			switch (m_socksv) 
			{
				case SOCKS5:
					LogPrint(eLogError, "SOCKS: v5 unsupported address type: ", m_addrtype);
				break;
				case SOCKS4:
					LogPrint(eLogError, "SOCKS: request with v4a rejected because it's actually SOCKS4");
				break;
			}
			SocksRequestFailed(SOCKS5_ADDR_UNSUP);
			return false;
		}
		//TODO: we may want to support other domains
		if(m_addrtype == ADDR_DNS && m_address.dns.ToString().find(".i2p") == std::string::npos) 
		{
			LogPrint(eLogError, "SOCKS: invalid hostname: ", m_address.dns.ToString());
			SocksRequestFailed(SOCKS5_ADDR_UNSUP);
			return false;
		}
		return true;
	}

	bool SOCKSHandler::HandleData(uint8_t *sock_buff, std::size_t len)
	{
		assert(len); // This should always be called with a least a byte left to parse
		while (len > 0) 
		{
			switch (m_state) 
			{
				case GET_SOCKSV:
					m_socksv = (SOCKSHandler::socksVersions) *sock_buff;
					switch (*sock_buff) 
					{
						case SOCKS4:
							EnterState(GET_COMMAND); //Initialize the parser at the right position
						break;
						case SOCKS5:
							EnterState(GET5_AUTHNUM); //Initialize the parser at the right position
						break;
						default:
							LogPrint(eLogError, "SOCKS: rejected invalid version: ", ((int)*sock_buff));
							Terminate();
							return false;
					}
				break;
				case GET5_AUTHNUM:
					EnterState(GET5_AUTH, *sock_buff);
				break;
				case GET5_AUTH:
					m_parseleft --;
					if (*sock_buff == AUTH_NONE)
						m_authchosen = AUTH_NONE;
					if ( m_parseleft == 0 ) 
					{
						if (!Socks5ChooseAuth()) return false;
						EnterState(GET5_REQUESTV);
					}
				break;
				case GET_COMMAND:
					switch (*sock_buff) 
					{
						case CMD_CONNECT:
						case CMD_BIND:
						break;
						case CMD_UDP:
							if (m_socksv == SOCKS5) break;
						default:
							LogPrint(eLogError, "SOCKS: invalid command: ", ((int)*sock_buff));
							SocksRequestFailed(SOCKS5_GEN_FAIL);
							return false;
					}
					m_cmd = (SOCKSHandler::cmdTypes)*sock_buff;
					switch (m_socksv) 
					{
						case SOCKS5: EnterState(GET5_GETRSV); break;
						case SOCKS4: EnterState(GET_PORT); break;
					}
				break;
				case GET_PORT:
					m_port = (m_port << 8)|((uint16_t)*sock_buff);
					m_parseleft--;
					if (m_parseleft == 0) 
					{
						switch (m_socksv) 
						{
							case SOCKS5: EnterState(DONE); break;
							case SOCKS4: EnterState(GET_IPV4); break;
						}
					}
				break;
				case GET_IPV4:
					m_address.ip = (m_address.ip << 8)|((uint32_t)*sock_buff);
					m_parseleft--;
					if (m_parseleft == 0) 
					{
						switch (m_socksv) 
						{
							case SOCKS5: EnterState(GET_PORT); break;
							case SOCKS4: EnterState(GET4_IDENT); m_4aip = m_address.ip; break;
						}
					}
				break;
				case GET4_IDENT:
					if (!*sock_buff) 
					{
						if( m_4aip == 0 || m_4aip > 255 )
							EnterState(DONE);
						else
							EnterState(GET4A_HOST);
					}
				break;
				case GET4A_HOST:
					if (!*sock_buff) 
					{
						EnterState(DONE);
						break;
					}
					if (m_address.dns.size >= max_socks_hostname_size) 
					{
						LogPrint(eLogError, "SOCKS: v4a req failed: destination is too large");
						SocksRequestFailed(SOCKS4_FAIL);
						return false;
					}
					m_address.dns.push_back(*sock_buff);
				break;
				case GET5_REQUESTV:
					if (*sock_buff != SOCKS5) 
					{
						LogPrint(eLogError,"SOCKS: v5 rejected unknown request version: ", ((int)*sock_buff));
						SocksRequestFailed(SOCKS5_GEN_FAIL);
						return false;
					}
					EnterState(GET_COMMAND);
				break;
				case GET5_GETRSV:
					if ( *sock_buff != 0 ) 
					{
						LogPrint(eLogError, "SOCKS: v5 unknown reserved field: ", ((int)*sock_buff));
						SocksRequestFailed(SOCKS5_GEN_FAIL);
						return false;
					}
					EnterState(GET5_GETADDRTYPE);
				break;
				case GET5_GETADDRTYPE:
					switch (*sock_buff) 
					{
						case ADDR_IPV4: EnterState(GET_IPV4); break;
						case ADDR_IPV6: EnterState(GET5_IPV6); break;
						case ADDR_DNS : EnterState(GET5_HOST_SIZE); break;
						default:
							LogPrint(eLogError, "SOCKS: v5 unknown address type: ", ((int)*sock_buff));
							SocksRequestFailed(SOCKS5_GEN_FAIL);
							return false;
					}
				break;
				case GET5_IPV6:
					m_address.ipv6[16-m_parseleft] = *sock_buff;
					m_parseleft--;
					if (m_parseleft == 0) EnterState(GET_PORT);
				break;
				case GET5_HOST_SIZE:
					EnterState(GET5_HOST, *sock_buff);
				break;
				case GET5_HOST:
					m_address.dns.push_back(*sock_buff);
					m_parseleft--;
					if (m_parseleft == 0) EnterState(GET_PORT);
				break;
				default:
					LogPrint(eLogError, "SOCKS: parse state?? ", m_state);
					Terminate();
					return false;
			}
			sock_buff++;
			len--;
			if (m_state == DONE) 
			{
				m_remaining_data_len = len;
				m_remaining_data = sock_buff;
				return ValidateSOCKSRequest();
			}
		}
		return true;
	}

	void SOCKSHandler::HandleSockRecv(const boost::system::error_code & ecode, std::size_t len)
	{
		LogPrint(eLogDebug, "SOCKS: recieved ", len, " bytes");
		if(ecode) 
		{
			LogPrint(eLogWarning, "SOCKS: recv got error: ", ecode);
			Terminate();
			return;
		}

		if (HandleData(m_sock_buff, len)) 
		{
			if (m_state == DONE) 
			{
				LogPrint(eLogInfo, "SOCKS: requested ", m_address.dns.ToString(), ":" , m_port);
				GetOwner()->CreateStream ( std::bind (&SOCKSHandler::HandleStreamRequestComplete,
						shared_from_this(), std::placeholders::_1), m_address.dns.ToString(), m_port);
			} 
			else
				AsyncSockRead();
		}
	}

	void SOCKSHandler::SentSocksFailed(const boost::system::error_code & ecode)
	{
		if (ecode)
			LogPrint (eLogError, "SOCKS: closing socket after sending failure because: ", ecode.message ());
		Terminate();
	}

	void SOCKSHandler::SentSocksDone(const boost::system::error_code & ecode)
	{
		if (!ecode) 
		{
			if (Kill()) return;
			LogPrint (eLogInfo, "SOCKS: new I2PTunnel connection");
			auto connection = std::make_shared<i2p::client::I2PTunnelConnection>(GetOwner(), m_sock, m_stream);
			GetOwner()->AddHandler (connection);
			connection->I2PConnect (m_remaining_data,m_remaining_data_len);
			Done(shared_from_this());
		}
		else
		{
			LogPrint (eLogError, "SOCKS: closing socket after completion reply because: ", ecode.message ());
			Terminate();
		}
	}

	void SOCKSHandler::SentSocksResponse(const boost::system::error_code & ecode)
	{
		if (ecode) 
		{
			LogPrint (eLogError, "SOCKS: closing socket after sending reply because: ", ecode.message ());
			Terminate();
		}
	}

	void SOCKSHandler::HandleStreamRequestComplete (std::shared_ptr<i2p::stream::Stream> stream)
	{
		if (stream) 
		{
			m_stream = stream;
			SocksRequestSuccess();
		} 
		else 
		{
			LogPrint (eLogError, "SOCKS: error when creating the stream, check the previous warnings for more info");
			SocksRequestFailed(SOCKS5_HOST_UNREACH);
		}
	}

	SOCKSServer::SOCKSServer(const std::string& address, int port, const std::string& outAddress, int outPort,
	    std::shared_ptr<i2p::client::ClientDestination> localDestination) : 
		TCPIPAcceptor (address, port, localDestination ? localDestination : i2p::client::context.GetSharedLocalDestination ()) 
	{
	}
	
	std::shared_ptr<i2p::client::I2PServiceHandler> SOCKSServer::CreateHandler(std::shared_ptr<boost::asio::ip::tcp::socket> socket)
	{
		return std::make_shared<SOCKSHandler> (this, socket);
	}

}
}