LCX.exe的功能

  • 2017-07-22
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最近在看一本书,其中有一节唤作“LCX端口转发实现内网突破”,我仔细地读了几遍,竟是一头雾水,全然不知在讲些什么,遂百度lcx.exe,又看了几篇文章,依旧不知所云。所幸找到了lcx.exe的源码,读了一遍,所有疑惑都烟消云散。

原本看不懂关于lcx.exe的文章,是由于找到的那些文章都在讲解lcx.exe的用法,对于原理只字未提,功能也只是略作说明。我不了解lcx.exe的功能,不知道它是干什么的,又不满足于生硬地记下lcx.exe的几条命令、几种用法,故而疑惑重重,觉得玄妙难懂。当阅读了源码,知道其原理功能后,再看用法,便清晰明了了。原理、功能和法用有何区别?举例来说,菜刀(此处指切菜的菜刀,不是中国菜刀)的原理是刀身坚固具有刀刃,刃坚硬不易折损,面积小压强大;功能是切割物体;用法是切菜、切肉等。本文将总结lcx.exe的功能,涉及部分原理。lcx.exe的源码附在文末。

lcx.exe的功能是进行端口转发,更具体的讲是进行TCP的端口转发。何为端口转发,我们知道,TCP共有65535个端口,端口转发,便是将一个端口接受到的数据,发送到另一个端口,将另一个端口接受到的数据,发送到这个端口,仅此而已。

lcx.exe有三种工作模式。为何是三种而不是两种或四种?因为TCP协议下,一个端口可处于两种模式之一——客户端模式或服务器模式,而端口转发涉及两个端口,故有三种可能:两个端口都处于服务器模式、一个端口处于服务器模式另一个端口处于客户端模式、两个端口都处于客户端模式。下面按这三种情况分别进行讨论。

1.两个端口都处于服务器模式

这一模式对应的参数是:

  -listen <ConnectPort> <TransmitPort>

简单地讲,就是 -listen 后接两个数字,分别是两个端口号。此模式下,lcx.exe分别监听ConnectPort和TransmitPort这两个端口,也就是说,这两个端口都处于服务器模式下,等待客户端连接。当有两个客户端分别与ConnectPort和TransmitPort建立连接后,端口转发便开始工作,互换ConnectPort和TransmitPort接受/发送的数据。

2.一个端口处于服务器模式另一个端口处于客户端模式

这一模式对应的参数是:

  -tran <ConnectPort> <TransmitHost> <TransmitPort>

此模式下,lcx.exe监听ConnectPort端口,此端口处于服务器模式,等待客户端连接。当有客户端连接到此端口后,lcx.exe会发起到TransmitHost主机的TransmitPort端口的TCP连接,此连接使用的本地端口是随机的某个未使用的端口,假设其为RandomPort,若连接成功,则开始端口转发,互换ConnectPort和RandomPort接受/发送的数据。

3.两个端口都处于客户端模式

这一模式对应的参数是:

  -slave <ConnectHost> <ConnectPort> <TransmitHost> <TransmitPort>

此模式下,lcx.exe会建立到ConnectHost主机的ConnectPort端口的TCP连接,假设使用的本地端口是RandomPort1,若成功,则会接着建立到TransmitHost主机的TransmitPort端口的TCP连接,假设使用的本地端口是RandomPort2,若成功,则开始端口转发,互换RandomPort1和RandomPort2接受/发送的数据。RandomPort1和RandomPort2都是随机的未使用端口。

以上便是lcx.exe的功能与原理,了解这些后,用法便不是问题了。就如同了解菜刀是用于切割物体后,拿菜刀是去切菜还是去砍人都不是问题一般。listen、slave等名字应该来源于lcx.exe最经典的用法——内网突破。当然,有时我们也会想看看别人怎么玩菜刀的:《Lcx的多种用法:3个功能+9个参数,你会怎么玩? 》

附:lcx.exe源码:


/* ************************************************************************************ * * HTran.cpp - HUC Packet Transmit Tool. * * Copyright (C) 2000-2004 HUC All Rights Reserved. * * Author : lion * : lion#cnhonker.net * : [url]http://www.cnhonker.com[/url] * : * Notice : Thx to bkbll (bkbll#cnhonker.net) * : * Date : 2003-10-20 * : * Complie : cl HTran.cpp * : * Usage : E:\>HTran * : ======================== HUC Packet Transmit Tool V1.00 ======================= * : =========== Code by lion & bkbll, Welcome to [url]http://www.cnhonker.com[/url] ========== * : * : [Usage of Packet Transmit:] * : HTran -<listen|tran|slave> <option> [-log logfile] * : * : [option:] * : -listen <ConnectPort> <TransmitPort> * : -tran <ConnectPort> <TransmitHost> <TransmitPort> * : -slave <ConnectHost> <ConnectPort> <TransmitHost> <TransmitPort> * ************************************************************************************ */ #include <stdio.h> #include <stdlib.h> #include <errno.h> #include <winsock2.h> #include <io.h> #include <signal.h> #pragma comment(lib, "ws2_32.lib") #define VERSION "1.00" #define TIMEOUT 300 #define MAXSIZE 20480 #define HOSTLEN 40 #define CONNECTNUM 5 // define 2 socket struct struct transocket { SOCKET fd1; SOCKET fd2; }; // define function void ver(); void usage(char *prog); void transmitdata(LPVOID data); void getctrlc(int j); void closeallfd(); void makelog(char *buffer, int length); void proxy(int port); void bind2bind(int port1, int port2); void bind2conn(int port1, char *host, int port2); void conn2conn(char *host1, int port1, char *host2, int port2); int testifisvalue(char *str); int create_socket(); int create_server(int sockfd, int port); int client_connect(int sockfd, char* server, int port); // define GLOBAL variable here FILE *fp; int method=0; //int connectnum=0; //************************************************************************************ // // function main // //************************************************************************************ VOID main(int argc, char* argv[]) { char **p; char sConnectHost[HOSTLEN], sTransmitHost[HOSTLEN]; int iConnectPort=0, iTransmitPort=0; char *logfile=NULL; ver(); memset(sConnectHost, 0, HOSTLEN); memset(sTransmitHost, 0, HOSTLEN); p=argv; while(*p) { if(stricmp(*p, "-log") == 0) { if(testifisvalue(*(p+1))) { logfile = *(++p); } else { printf("[-] ERROR: Must supply logfile name.\r\n"); return; } p++; continue; } p++; } if(logfile !=NULL) { fp=fopen(logfile,"a"); if(fp == NULL ) { printf("[-] ERROR: open logfile"); return; } makelog("====== Start ======\r\n", 22); } // Win Start Winsock. WSADATA wsadata; WSAStartup(MAKEWORD(1, 1), &wsadata); signal(SIGINT, &getctrlc); if(argc > 2) { if(stricmp(argv[1], "-listen") == 0 && argc >= 4) { iConnectPort = atoi(argv[2]); iTransmitPort = atoi(argv[3]); method = 1; } else if(stricmp(argv[1], "-tran") == 0 && argc >= 5) { iConnectPort = atoi(argv[2]); strncpy(sTransmitHost, argv[3], HOSTLEN); iTransmitPort = atoi(argv[4]); method = 2; } else if(stricmp(argv[1], "-slave") == 0 && argc >= 6) { strncpy(sConnectHost, argv[2], HOSTLEN); iConnectPort = atoi(argv[3]); strncpy(sTransmitHost, argv[4], HOSTLEN); iTransmitPort = atoi(argv[5]); method = 3; } } switch(method) { case 1: bind2bind(iConnectPort, iTransmitPort); break; case 2: bind2conn(iConnectPort, sTransmitHost, iTransmitPort); break; case 3: conn2conn(sConnectHost, iConnectPort, sTransmitHost, iTransmitPort); break; default: usage(argv[0]); break; } if(method) { closeallfd(); } WSACleanup(); return; } //************************************************************************************ // // print version message // //************************************************************************************ VOID ver() { } //************************************************************************************ // // print usage message // //************************************************************************************ VOID usage(char* prog) { printf("[Usage of Packet Transmit:]\r\n"); printf(" %s -<listen|tran|slave> <option> [-log logfile]\n\n", prog); printf("[option:]\n"); printf(" -listen <ConnectPort> <TransmitPort>\n"); printf(" -tran <ConnectPort> <TransmitHost> <TransmitPort>\n"); printf(" -slave <ConnectHost> <ConnectPort> <TransmitHost> <TransmitPort>\n\n"); return; } //************************************************************************************ // // test if is value // //************************************************************************************ int testifisvalue(char *str) { if(str == NULL ) return(0); if(str[0]=='-') return(0); return(1); } //************************************************************************************ // // LocalHost:ConnectPort transmit to LocalHost:TransmitPort // //************************************************************************************ void bind2bind(int port1, int port2) { SOCKET fd1,fd2, sockfd1, sockfd2; struct sockaddr_in client1,client2; int size1,size2; HANDLE hThread=NULL; transocket sock; DWORD dwThreadID; if((fd1=create_socket())==0) return; if((fd2=create_socket())==0) return; printf("[+] Listening port %d ......\r\n",port1); fflush(stdout); if(create_server(fd1, port1)==0) { closesocket(fd1); return; } printf("[+] Listen OK!\r\n"); printf("[+] Listening port %d ......\r\n",port2); fflush(stdout); if(create_server(fd2, port2)==0) { closesocket(fd2); return; } printf("[+] Listen OK!\r\n"); size1=size2=sizeof(struct sockaddr); while(1) { printf("[+] Waiting for Client on port:%d ......\r\n",port1); if((sockfd1 = accept(fd1,(struct sockaddr *)&client1,&size1))<0) { printf("[-] Accept1 error.\r\n"); continue; } printf("[+] Accept a Client on port %d from %s ......\r\n", port1, inet_ntoa(client1.sin_addr)); printf("[+] Waiting another Client on port:%d....\r\n", port2); if((sockfd2 = accept(fd2, (struct sockaddr *)&client2, &size2))<0) { printf("[-] Accept2 error.\r\n"); closesocket(sockfd1); continue; } printf("[+] Accept a Client on port %d from %s\r\n",port2, inet_ntoa(client2.sin_addr)); printf("[+] Accept Connect OK!\r\n"); sock.fd1 = sockfd1; sock.fd2 = sockfd2; hThread = CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE)transmitdata, (LPVOID)&sock, 0, &dwThreadID); if(hThread == NULL) { TerminateThread(hThread, 0); return; } Sleep(1000); printf("[+] CreateThread OK!\r\n\n"); } } //************************************************************************************ // // LocalHost:ConnectPort transmit to TransmitHost:TransmitPort // //************************************************************************************ void bind2conn(int port1, char *host, int port2) { SOCKET sockfd,sockfd1,sockfd2; struct sockaddr_in remote; int size; char buffer[1024]; HANDLE hThread=NULL; transocket sock; DWORD dwThreadID; if (port1 > 65535 || port1 < 1) { printf("[-] ConnectPort invalid.\r\n"); return; } if (port2 > 65535 || port2 < 1) { printf("[-] TransmitPort invalid.\r\n"); return; } memset(buffer,0,1024); if((sockfd=create_socket()) == INVALID_SOCKET) return; if(create_server(sockfd, port1) == 0) { closesocket(sockfd); return; } size=sizeof(struct sockaddr); while(1) { printf("[+] Waiting for Client ......\r\n"); if((sockfd1=accept(sockfd,(struct sockaddr *)&remote,&size))<0) { printf("[-] Accept error.\r\n"); continue; } printf("[+] Accept a Client from %s:%d ......\r\n", inet_ntoa(remote.sin_addr), ntohs(remote.sin_port)); if((sockfd2=create_socket())==0) { closesocket(sockfd1); continue; } printf("[+] Make a Connection to %s:%d ......\r\n",host,port2); fflush(stdout); if(client_connect(sockfd2,host,port2)==0) { closesocket(sockfd2); sprintf(buffer,"[SERVER]connection to %s:%d error\r\n", host, port2); send(sockfd1,buffer,strlen(buffer),0); memset(buffer, 0, 1024); closesocket(sockfd1); continue; } printf("[+] Connect OK!\r\n"); sock.fd1 = sockfd1; sock.fd2 = sockfd2; hThread = CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE)transmitdata, (LPVOID)&sock, 0, &dwThreadID); if(hThread == NULL) { TerminateThread(hThread, 0); return; } Sleep(1000); printf("[+] CreateThread OK!\r\n\n"); } } //************************************************************************************ // // ConnectHost:ConnectPort transmit to TransmitHost:TransmitPort // //************************************************************************************ void conn2conn(char *host1,int port1,char *host2,int port2) { SOCKET sockfd1,sockfd2; HANDLE hThread=NULL; transocket sock; DWORD dwThreadID; fd_set fds; int l; char buffer[MAXSIZE]; while(1) { /* while(connectnum) { if(connectnum < CONNECTNUM) { Sleep(10000); break; } else { Sleep(TIMEOUT*1000); continue; } } */ if((sockfd1=create_socket())==0) return; if((sockfd2=create_socket())==0) return; printf("[+] Make a Connection to %s:%d....\r\n",host1,port1); fflush(stdout); if(client_connect(sockfd1,host1,port1)==0) { closesocket(sockfd1); closesocket(sockfd2); continue; } // fix by bkbll // if host1:port1 recved data, than connect to host2,port2 l=0; memset(buffer,0,MAXSIZE); while(1) { FD_ZERO(&fds); FD_SET(sockfd1, &fds); if (select(sockfd1+1, &fds, NULL, NULL, NULL) == SOCKET_ERROR) { if (errno == WSAEINTR) continue; break; } if (FD_ISSET(sockfd1, &fds)) { l=recv(sockfd1, buffer, MAXSIZE, 0); break; } Sleep(5); } if(l<=0) { printf("[-] There is a error...Create a new connection.\r\n"); continue; } while(1) { printf("[+] Connect OK!\r\n"); printf("[+] Make a Connection to %s:%d....\r\n", host2,port2); fflush(stdout); if(client_connect(sockfd2,host2,port2)==0) { closesocket(sockfd1); closesocket(sockfd2); continue; } if(send(sockfd2,buffer,l,0)==SOCKET_ERROR) { printf("[-] Send failed.\r\n"); continue; } l=0; memset(buffer,0,MAXSIZE); break; } printf("[+] All Connect OK!\r\n"); sock.fd1 = sockfd1; sock.fd2 = sockfd2; hThread = CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE)transmitdata, (LPVOID)&sock, 0, &dwThreadID); if(hThread == NULL) { TerminateThread(hThread, 0); return; } // connectnum++; Sleep(1000); printf("[+] CreateThread OK!\r\n\n"); } } //************************************************************************************ // // Socket Transmit to Socket // //************************************************************************************ void transmitdata(LPVOID data) { SOCKET fd1, fd2; transocket *sock; struct timeval timeset; fd_set readfd,writefd; int result,i=0; char read_in1[MAXSIZE],send_out1[MAXSIZE]; char read_in2[MAXSIZE],send_out2[MAXSIZE]; int read1=0,totalread1=0,send1=0; int read2=0,totalread2=0,send2=0; int sendcount1,sendcount2; int maxfd; struct sockaddr_in client1,client2; int structsize1,structsize2; char host1[20],host2[20]; int port1=0,port2=0; char tmpbuf[100]; sock = (transocket *)data; fd1 = sock->fd1; fd2 = sock->fd2; memset(host1,0,20); memset(host2,0,20); memset(tmpbuf,0,100); structsize1=sizeof(struct sockaddr); structsize2=sizeof(struct sockaddr); if(getpeername(fd1,(struct sockaddr *)&client1,&structsize1)<0) { strcpy(host1, "fd1"); } else { // printf("[+]got, ip:%s, port:%d\r\n",inet_ntoa(client1.sin_addr),ntohs(client1.sin_port)); strcpy(host1, inet_ntoa(client1.sin_addr)); port1=ntohs(client1.sin_port); } if(getpeername(fd2,(struct sockaddr *)&client2,&structsize2)<0) { strcpy(host2,"fd2"); } else { // printf("[+]got, ip:%s, port:%d\r\n",inet_ntoa(client2.sin_addr),ntohs(client2.sin_port)); strcpy(host2, inet_ntoa(client2.sin_addr)); port2=ntohs(client2.sin_port); } printf("[+] Start Transmit (%s:%d <-> %s:%d) ......\r\n\n", host1, port1, host2, port2); maxfd=max(fd1,fd2)+1; memset(read_in1,0,MAXSIZE); memset(read_in2,0,MAXSIZE); memset(send_out1,0,MAXSIZE); memset(send_out2,0,MAXSIZE); timeset.tv_sec=TIMEOUT; timeset.tv_usec=0; while(1) { FD_ZERO(&readfd); FD_ZERO(&writefd); FD_SET((UINT)fd1, &readfd); FD_SET((UINT)fd1, &writefd); FD_SET((UINT)fd2, &writefd); FD_SET((UINT)fd2, &readfd); result=select(maxfd,&readfd,&writefd,NULL,×et); if((result<0) && (errno!=EINTR)) { printf("[-] Select error.\r\n"); break; } else if(result==0) { printf("[-] Socket time out.\r\n"); break; } if(FD_ISSET(fd1, &readfd)) { /* must < MAXSIZE-totalread1, otherwise send_out1 will flow */ if(totalread1<MAXSIZE) { read1=recv(fd1, read_in1, MAXSIZE-totalread1, 0); if((read1==SOCKET_ERROR) || (read1==0)) { printf("[-] Read fd1 data error,maybe close?\r\n"); break; } memcpy(send_out1+totalread1,read_in1,read1); sprintf(tmpbuf,"\r\nRecv %5d bytes from %s:%d\r\n", read1, host1, port1); //printf(" Recv %5d bytes %16s:%d\r\n", read1, host1, port1); makelog(tmpbuf,strlen(tmpbuf)); makelog(read_in1,read1); totalread1+=read1; memset(read_in1,0,MAXSIZE); } } if(FD_ISSET(fd2, &writefd)) { int err=0; sendcount1=0; while(totalread1>0) { send1=send(fd2, send_out1+sendcount1, totalread1, 0); if(send1==0)break; if((send1<0) && (errno!=EINTR)) { printf("[-] Send to fd2 unknow error.\r\n"); err=1; break; } if((send1<0) && (errno==ENOSPC)) break; sendcount1+=send1; totalread1-=send1; //printf(" Send %5d bytes %16s:%d\r\n", send1, host2, port2); } if(err==1) break; if((totalread1>0) && (sendcount1>0)) { /* move not sended data to start addr */ memcpy(send_out1,send_out1+sendcount1,totalread1); memset(send_out1+totalread1,0,MAXSIZE-totalread1); } else memset(send_out1,0,MAXSIZE); } if(FD_ISSET(fd2, &readfd)) { if(totalread2<MAXSIZE) { read2=recv(fd2,read_in2,MAXSIZE-totalread2, 0); if(read2==0)break; if((read2<0) && (errno!=EINTR)) { printf("[-] Read fd2 data error,maybe close?\r\n\r\n"); break; } memcpy(send_out2+totalread2,read_in2,read2); sprintf(tmpbuf, "\r\nRecv %5d bytes from %s:%d\r\n", read2, host2, port2); //printf(" Recv %5d bytes %16s:%d\r\n", read2, host2, port2); makelog(tmpbuf,strlen(tmpbuf)); makelog(read_in2,read2); totalread2+=read2; memset(read_in2,0,MAXSIZE); } } if(FD_ISSET(fd1, &writefd)) { int err2=0; sendcount2=0; while(totalread2>0) { send2=send(fd1, send_out2+sendcount2, totalread2, 0); if(send2==0)break; if((send2<0) && (errno!=EINTR)) { printf("[-] Send to fd1 unknow error.\r\n"); err2=1; break; } if((send2<0) && (errno==ENOSPC)) break; sendcount2+=send2; totalread2-=send2; //printf(" Send %5d bytes %16s:%d\r\n", send2, host1, port1); } if(err2==1) break; if((totalread2>0) && (sendcount2 > 0)) { /* move not sended data to start addr */ memcpy(send_out2, send_out2+sendcount2, totalread2); memset(send_out2+totalread2, 0, MAXSIZE-totalread2); } else memset(send_out2,0,MAXSIZE); } Sleep(5); } closesocket(fd1); closesocket(fd2); // if(method == 3) // connectnum --; printf("\r\n[+] OK! I Closed The Two Socket.\r\n"); } void getctrlc(int j) { printf("\r\n[-] Received Ctrl+C\r\n"); closeallfd(); exit(0); } void closeallfd() { int i; printf("[+] Let me exit ......\r\n"); fflush(stdout); for(i=3; i<256; i++) { closesocket(i); } if(fp != NULL) { fprintf(fp,"\r\n====== Exit ======\r\n"); fclose(fp); } printf("[+] All Right!\r\n"); } int create_socket() { int sockfd; sockfd=socket(AF_INET,SOCK_STREAM,0); if(sockfd<0) { printf("[-] Create socket error.\r\n"); return(0); } return(sockfd); } int create_server(int sockfd,int port) { struct sockaddr_in srvaddr; int on=1; memset(&srvaddr, 0, sizeof(struct sockaddr)); srvaddr.sin_port=htons(port); srvaddr.sin_family=AF_INET; srvaddr.sin_addr.s_addr=htonl(INADDR_ANY); setsockopt(sockfd,SOL_SOCKET,SO_REUSEADDR, (char*)&on,sizeof(on)); //so I can rebind the port if(bind(sockfd,(struct sockaddr *)&srvaddr,sizeof(struct sockaddr))<0) { printf("[-] Socket bind error.\r\n"); return(0); } if(listen(sockfd,CONNECTNUM)<0) { printf("[-] Socket Listen error.\r\n"); return(0); } return(1); } int client_connect(int sockfd,char* server,int port) { struct sockaddr_in cliaddr; struct hostent *host; if(!(host=gethostbyname(server))) { printf("[-] Gethostbyname(%s) error:%s\n",server,strerror(errno)); return(0); } memset(&cliaddr, 0, sizeof(struct sockaddr)); cliaddr.sin_family=AF_INET; cliaddr.sin_port=htons(port); cliaddr.sin_addr=*((struct in_addr *)host->h_addr); if(connect(sockfd,(struct sockaddr *)&cliaddr,sizeof(struct sockaddr))<0) { printf("[-] Connect error.\r\n"); return(0); } return(1); } void makelog(char *buffer,int length) { if(fp !=NULL) { // fprintf(fp, "%s", buffer); // printf("%s",buffer); write(fileno(fp),buffer,length); // fflush(fp); } }

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