From b9f7f75ddfa699b4ced35fa0d2c3b2acde9957f9 Mon Sep 17 00:00:00 2001 From: Adam Ierymenko Date: Sun, 26 Apr 2015 16:38:39 -0700 Subject: [PATCH] TCP proxy for tunneling (desperation > 0). --- tcp-proxy/README.md | 4 + tcp-proxy/tcp-proxy.cpp | 322 ++++++++++++++++++++++++++++++++++++++++ 2 files changed, 326 insertions(+) create mode 100644 tcp-proxy/README.md create mode 100644 tcp-proxy/tcp-proxy.cpp diff --git a/tcp-proxy/README.md b/tcp-proxy/README.md new file mode 100644 index 000000000..6f347d640 --- /dev/null +++ b/tcp-proxy/README.md @@ -0,0 +1,4 @@ +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 new file mode 100644 index 000000000..6837803f2 --- /dev/null +++ b/tcp-proxy/tcp-proxy.cpp @@ -0,0 +1,322 @@ +/* + * 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 . + * + * -- + * + * 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 +#include +#include +#include +#include +#include +#include + +#include +#include +#include +#include +#include + +#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 *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::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= 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 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::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 phy(&svc,true); + svc.phy = &phy; + + { + int poolSize = 0; + for(unsigned int p=ZT_TCP_PROXY_UDP_POOL_START_PORT;((poolSize 120) { + lastDidHousekeeping = now; + svc.doHousekeeping(); + } + } +}