TCP proxy for tunneling (desperation > 0).

2 files changed, 326 insertions, 0 deletions

diff --git a/tcp-proxy/README.md b/tcp-proxy/README.md
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+TCP Proxy Server
+======
+
+This is the TCP proxy server we run for TCP tunneling from peers behind fascist NATs. Regular users won't have much use for this.
diff --git a/tcp-proxy/tcp-proxy.cpp b/tcp-proxy/tcp-proxy.cpp
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+++ b/tcp-proxy/tcp-proxy.cpp
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+/*
+ * ZeroTier One - Network Virtualization Everywhere
+ * Copyright (C) 2011-2015  ZeroTier, Inc.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * --
+ *
+ * ZeroTier may be used and distributed under the terms of the GPLv3, which
+ * are available at: http://www.gnu.org/licenses/gpl-3.0.html
+ *
+ * If you would like to embed ZeroTier into a commercial application or
+ * redistribute it in a modified binary form, please contact ZeroTier Networks
+ * LLC. Start here: http://www.zerotier.com/
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <time.h>
+#include <stdint.h>
+#include <unistd.h>
+#include <signal.h>
+
+#include <map>
+#include <set>
+#include <string>
+#include <algorithm>
+#include <vector>
+
+#include "../osdep/Phy.hpp"
+
+#define ZT_TCP_PROXY_UDP_POOL_SIZE 1024
+#define ZT_TCP_PROXY_UDP_POOL_START_PORT 10000
+#define ZT_TCP_PROXY_CONNECTION_TIMEOUT_SECONDS 300
+
+using namespace ZeroTier;
+
+/*
+ * This implements a simple packet encapsulation that is designed to look like
+ * a TLS connection. It's not a TLS connection, but it sends TLS format record
+ * headers. It could be extended in the future to implement a fake TLS
+ * handshake.
+ *
+ * At the moment, each packet is just made to look like TLS application data:
+ *   <[1] TLS content type> - currently 0x17 for "application data"
+ *   <[1] TLS major version> - currently 0x03 for TLS 1.2
+ *   <[1] TLS minor version> - currently 0x03 for TLS 1.2
+ *   <[2] payload length> - 16-bit length of payload in bytes
+ *   <[...] payload> - Message payload
+ *
+ * The primary purpose of TCP sockets is to work over ports like HTTPS(443),
+ * allowing users behind particularly fascist firewalls to at least reach
+ * ZeroTier's supernodes. UDP is the preferred method of communication as
+ * encapsulating L2 and L3 protocols over TCP is inherently inefficient
+ * due to double-ACKs. So TCP is only used as a fallback.
+ *
+ * New clients send a HELLO message consisting of a 4-byte message (too small
+ * for a ZT packet) containing:
+ *   <[1] ZeroTier major version>
+ *   <[1] minor version>
+ *   <[2] revision>
+ *
+ * Clients that have send a HELLO and that have a new enough version prepend
+ * each payload with the remote IP the message is destined for. This is in
+ * the same format as the IP portion of ZeroTier HELLO packets.
+ */
+
+struct TcpProxyService;
+struct TcpProxyService
+{
+	Phy<TcpProxyService *> *phy;
+	PhySocket *udpPool[ZT_TCP_PROXY_UDP_POOL_SIZE];
+
+	struct Client
+	{
+		char tcpReadBuf[131072];
+		char tcpWriteBuf[131072];
+		unsigned long tcpWritePtr;
+		unsigned long tcpReadPtr;
+		PhySocket *tcp;
+		PhySocket *assignedUdp;
+		time_t lastActivity;
+		bool newVersion;
+	};
+
+	std::map< PhySocket *,Client > clients;
+
+	struct ReverseMappingKey
+	{
+		uint64_t sourceZTAddress;
+		PhySocket *sendingUdpSocket;
+		uint32_t destIp;
+		unsigned int destPort;
+
+		ReverseMappingKey() {}
+		ReverseMappingKey(uint64_t zt,PhySocket *s,uint32_t ip,unsigned int port) : sourceZTAddress(zt),sendingUdpSocket(s),destIp(ip),destPort(port) {}
+		inline bool operator<(const ReverseMappingKey &k) const throw() { return (memcmp((const void *)this,(const void *)&k,sizeof(ReverseMappingKey)) < 0); }
+		inline bool operator==(const ReverseMappingKey &k) const throw() { return (memcmp((const void *)this,(const void *)&k,sizeof(ReverseMappingKey)) == 0); }
+	};
+
+	std::map< ReverseMappingKey,Client * > reverseMappings;
+
+	void phyOnDatagram(PhySocket *sock,void **uptr,const struct sockaddr *from,void *data,unsigned long len)
+	{
+		if ((from->sa_family == AF_INET)&&(len > 16)&&(len < 2048)) {
+			const uint64_t destZt = (
+				(((uint64_t)(((const unsigned char *)data)[8])) << 32) |
+				(((uint64_t)(((const unsigned char *)data)[9])) << 24) |
+				(((uint64_t)(((const unsigned char *)data)[10])) << 16) |
+				(((uint64_t)(((const unsigned char *)data)[11])) << 8) |
+				((uint64_t)(((const unsigned char *)data)[12])) );
+			const uint32_t fromIp = ((const struct sockaddr_in *)from)->sin_addr.s_addr;
+			const unsigned int fromPort = ntohs(((const struct sockaddr_in *)from)->sin_port);
+
+			std::map< ReverseMappingKey,Client * >::iterator rm(reverseMappings.find(ReverseMappingKey(destZt,sock,fromIp,fromPort)));
+			if (rm != reverseMappings.end()) {
+				Client &c = *(rm->second);
+
+				unsigned long mlen = len;
+				if (c.newVersion)
+					mlen += 7; // new clients get IP info
+
+				if ((c.tcpWritePtr + 5 + mlen) <= sizeof(c.tcpWriteBuf)) {
+					if (!c.tcpWritePtr)
+						phy->tcpSetNotifyWritable(c.tcp,true);
+
+					c.tcpWriteBuf[c.tcpWritePtr++] = 0x17; // look like TLS data
+					c.tcpWriteBuf[c.tcpWritePtr++] = 0x03; // look like TLS 1.2
+					c.tcpWriteBuf[c.tcpWritePtr++] = 0x03; // look like TLS 1.2
+
+					c.tcpWriteBuf[c.tcpWritePtr++] = (char)((mlen >> 8) & 0xff);
+					c.tcpWriteBuf[c.tcpWritePtr++] = (char)(mlen & 0xff);
+
+					if (c.newVersion) {
+						c.tcpWriteBuf[c.tcpWritePtr++] = (char)4; // IPv4
+						*((uint32_t *)(c.tcpWriteBuf + c.tcpWritePtr)) = fromIp;
+						c.tcpWritePtr += 4;
+						c.tcpWriteBuf[c.tcpWritePtr++] = (char)((fromPort >> 8) & 0xff);
+						c.tcpWriteBuf[c.tcpWritePtr++] = (char)(fromPort & 0xff);
+					}
+
+					for(unsigned long i=0;i<len;++i)
+						c.tcpWriteBuf[c.tcpWritePtr++] = ((const char *)data)[i];
+				}
+			}
+		}
+	}
+
+	void phyOnTcpConnect(PhySocket *sock,void **uptr,bool success)
+	{
+		// unused, we don't initiate
+	}
+
+	void phyOnTcpAccept(PhySocket *sockL,PhySocket *sockN,void **uptrL,void **uptrN,const struct sockaddr *from)
+	{
+		Client &c = clients[sockN];
+		c.tcpWritePtr = 0;
+		c.tcpReadPtr = 0;
+		c.tcp = sockN;
+		c.assignedUdp = udpPool[rand() % ZT_TCP_PROXY_UDP_POOL_SIZE];
+		c.lastActivity = time((time_t *)0);
+		c.newVersion = false;
+		*uptrN = (void *)&c;
+	}
+
+	void phyOnTcpClose(PhySocket *sock,void **uptr)
+	{
+		for(std::map< ReverseMappingKey,Client * >::iterator rm(reverseMappings.begin());rm!=reverseMappings.end();) {
+			if (rm->second == (Client *)*uptr)
+				reverseMappings.erase(rm++);
+			else ++rm;
+		}
+		clients.erase(sock);
+	}
+
+	void phyOnTcpData(PhySocket *sock,void **uptr,void *data,unsigned long len)
+	{
+		Client &c = *((Client *)*uptr);
+		c.lastActivity = time((time_t *)0);
+
+		for(unsigned long i=0;i<len;++i) {
+			if (c.tcpReadPtr >= sizeof(c.tcpReadBuf)) {
+				phy->close(sock);
+				return;
+			}
+			c.tcpReadBuf[c.tcpReadPtr++] = ((const char *)data)[i];
+
+			if (c.tcpReadPtr >= 5) {
+				unsigned long mlen = ( ((((unsigned long)c.tcpReadBuf[3]) & 0xff) << 8) | (((unsigned long)c.tcpReadBuf[4]) & 0xff) );
+				if (c.tcpReadPtr >= (mlen + 5)) {
+					if (mlen == 4) {
+						// Right now just sending this means the client is 'new enough' for the IP header
+						c.newVersion = true;
+					} else if (mlen >= 7) {
+						char *payload = c.tcpReadBuf + 5;
+						unsigned long payloadLen = mlen;
+
+						struct sockaddr_in dest;
+						memset(&dest,0,sizeof(dest));
+						if (c.newVersion) {
+							if (*payload == (char)4) {
+								// New clients tell us where their packets go.
+								++payload;
+								dest.sin_family = AF_INET;
+								dest.sin_addr.s_addr = *((uint32_t *)payload);
+								payload += 4;
+								dest.sin_port = *((uint16_t *)payload); // will be in network byte order already
+								payload += 2;
+								payloadLen -= 7;
+							}
+						} else {
+							// For old clients we will just proxy everything to a local ZT instance. The
+							// fact that this will come from 127.0.0.1 will in turn prevent that instance
+							// from doing unite() with us. It'll just forward. There will not be many of
+							// these.
+							dest.sin_family = AF_INET;
+							dest.sin_addr.s_addr = htonl(0x7f000001); // 127.0.0.1
+							dest.sin_port = htons(9993);
+						}
+
+						// Note: we do not relay to privileged ports... just an abuse prevention rule.
+						if ((ntohs(dest.sin_port) > 1024)&&(payloadLen >= 16)) {
+							if ((payloadLen >= 28)&&(payload[13] != (char)0xff)) {
+								// Learn reverse mappings -- we will route replies to these packets
+								// back to their sending TCP socket. They're on a first come first
+								// served basis.
+								const uint64_t sourceZt = (
+									(((uint64_t)(((const unsigned char *)payload)[13])) << 32) |
+									(((uint64_t)(((const unsigned char *)payload)[14])) << 24) |
+									(((uint64_t)(((const unsigned char *)payload)[15])) << 16) |
+									(((uint64_t)(((const unsigned char *)payload)[16])) << 8) |
+									((uint64_t)(((const unsigned char *)payload)[17])) );
+								ReverseMappingKey k(sourceZt,c.assignedUdp,dest.sin_addr.s_addr,ntohl(dest.sin_port));
+								if (reverseMappings.count(k) == 0)
+									reverseMappings[k] = &c;
+							}
+
+							phy->udpSend(c.assignedUdp,(const struct sockaddr *)&dest,payload,payloadLen);
+						}
+					}
+
+					memmove(c.tcpReadBuf,c.tcpReadBuf + (mlen + 5),c.tcpReadPtr -= (mlen + 5));
+				}
+			}
+		}
+	}
+
+	void phyOnTcpWritable(PhySocket *sock,void **uptr)
+	{
+		Client &c = *((Client *)*uptr);
+		if (c.tcpWritePtr) {
+			long n = phy->tcpSend(sock,c.tcpWriteBuf,c.tcpWritePtr);
+			if (n > 0) {
+				memmove(c.tcpWriteBuf,c.tcpWriteBuf + n,c.tcpWritePtr -= (unsigned long)n);
+				if (!c.tcpWritePtr)
+					phy->tcpSetNotifyWritable(sock,false);
+			}
+		} else phy->tcpSetNotifyWritable(sock,false);
+	}
+
+	void doHousekeeping()
+	{
+		std::vector<PhySocket *> toClose;
+		time_t now = time((time_t *)0);
+		for(std::map< PhySocket *,Client >::iterator c(clients.begin());c!=clients.end();++c) {
+			if ((now - c->second.lastActivity) >= ZT_TCP_PROXY_CONNECTION_TIMEOUT_SECONDS)
+				toClose.push_back(c->first);
+		}
+		for(std::vector<PhySocket *>::iterator s(toClose.begin());s!=toClose.end();++s)
+			phy->close(*s); // will call phyOnTcpClose() which does cleanup
+	}
+};
+
+int main(int argc,char **argv)
+{
+	signal(SIGPIPE,SIG_IGN);
+	signal(SIGHUP,SIG_IGN);
+	srand(time((time_t *)0));
+
+	TcpProxyService svc;
+	Phy<TcpProxyService *> phy(&svc,true);
+	svc.phy = &phy;
+
+	{
+		int poolSize = 0;
+		for(unsigned int p=ZT_TCP_PROXY_UDP_POOL_START_PORT;((poolSize<ZT_TCP_PROXY_UDP_POOL_SIZE)&&(p<=65535));++p) {
+			struct sockaddr_in laddr;
+			memset(&laddr,0,sizeof(laddr));
+			laddr.sin_family = AF_INET;
+			laddr.sin_port = htons((uint16_t)p);
+			PhySocket *s = phy.udpBind((const struct sockaddr *)&laddr);
+			if (s)
+				svc.udpPool[poolSize++] = s;
+		}
+		if (poolSize < ZT_TCP_PROXY_UDP_POOL_SIZE) {
+			fprintf(stderr,"%s: fatal error: cannot bind %d UDP ports\n",argv[0],ZT_TCP_PROXY_UDP_POOL_SIZE);
+			return 1;
+		}
+	}
+
+	time_t lastDidHousekeeping = time((time_t *)0);
+	for(;;) {
+		phy.poll(120000);
+		time_t now = time((time_t *)0);
+		if ((now - lastDidHousekeeping) > 120) {
+			lastDidHousekeeping = now;
+			svc.doHousekeeping();
+		}
+	}
+}