Citation :
include <arpa/telnet.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <signal.h>
#include <unistd.h>
#include <fcntl.h>
#include <netdb.h>
#include <netinet/in.h>
#include <sys/socket.h>
#define DEBUG 0
#define TRACKING 0
#define CONN_OK_W_DATA 2
#define CONN_OK 1
#define CONN_FAILED 0
#define PROMPT "tn-gw->"
#define CONN_PROMPT_OK "Connected to"
#define CONN_CLOSED "Remote server has closed connection"
#define PACKET_SIZE 1024
#define MAX(a,b) (a<b?b:a)
#define FSET(a,b,c) (FD_ISSET(a,c)?a:b)
#define NFSET(a,b,c) (FD_ISSET(a,c)?b:a)
int writen(int fd, char *ptr, int n);
int readn(int fd, char *ptr, int n);
int forward(int fin, int fout);
int telnet_init(void);
unsigned short server_port = 12346;
char *proxy_name = "proxy";
unsigned short proxy_port = 23;
char *target_host = "target";
unsigned short target_port = 80;
struct sockaddr_in serverSock, clientSock, proxySock;
int fserver, ftarget, fcurrent, fproxy;
void usage ( void ) {
printf ( "Usage: telnet_proxy [OPTION]\n"
"open a tunnel via a proxy server\n\n"
" -? \t this help\n"
" -l port\t local port to listen ( default 12345 )\n"
" -p host\t proxy hostname ( default proxy )\n"
" -P port\t proxy port ( default 23 )\n"
" -t host\t target hostname ( default target )\n"
" -T port\t target port ( default 80 )\n" );
}
int main(int argc , char *argv[])
{
int ret, len, c;
struct hostent *proxyHostEnt; /* description du host serveur */
unsigned long hostAddr; /* addr du serveur */
fd_set fdsr;
long flags;
while ( ( c = getopt(argc,argv,"?l:p:P:t:T:" ) ) != -1 ) {
switch ( c ) {
case 'l' : server_port = atoi(optarg); break;
case 'P' : proxy_port = atoi(optarg); break;
case 'T' : target_port = atoi(optarg); break;
case 'p' : proxy_name = strdup(optarg); break;
case 't' : target_host = strdup(optarg); break;
case '?' :
default :
usage();
return 0;
}
}
printf("listen port:%d, proxy: %s:%d, target: %s:%d\n",server_port,
proxy_name,proxy_port,target_host,target_port);
fserver = socket(AF_INET, SOCK_STREAM, 0);
if (fserver < 0) {
perror("socket" );
return -1;
} else if ( DEBUG ) {
printf("server : %d\n",fserver);
}
serverSock.sin_family = AF_INET;
serverSock.sin_addr.s_addr = INADDR_ANY;
serverSock.sin_port = htons(server_port);
if (bind(fserver, (struct sockaddr *) &serverSock, sizeof(struct sockaddr_in))
< 0) {
perror("bind" );
return -1;
}
if (listen(fserver, 0) < 0) {
perror("listen" );
return -1;
}
for (;;) {
FD_ZERO(&fdsr);
FD_SET(fserver, &fdsr);
ret = select(fserver + 1, &fdsr, 0, 0, 0);
if (ret <= 0) {
close(fserver);
}
fcurrent = accept(fserver, (struct sockaddr *) &clientSock, &len);
fcntl(fcurrent, F_GETFL, &flags);
flags |= O_NONBLOCK;
fcntl(fcurrent, F_SETFL, &flags);
if (DEBUG) {
printf("current : %d\n", fcurrent);
}
bzero(&proxySock, sizeof(proxySock));
hostAddr = inet_addr(proxy_name);
if ((long) hostAddr != (long) -1)
bcopy(&hostAddr, &proxySock.sin_addr, sizeof(hostAddr));
else { /* si on a donne un nom */
proxyHostEnt = gethostbyname(proxy_name);
if (proxyHostEnt == NULL) {
printf("ca chie gethost\n" );
exit(0);
}
bcopy(proxyHostEnt->h_addr, &proxySock.sin_addr,proxyHostEnt->h_length);
}
proxySock.sin_port = htons(proxy_port); /* host to network port */
proxySock.sin_family = AF_INET; /* AF_*** : INET=internet */
if ((fproxy = socket(AF_INET, SOCK_STREAM, 0)) < 0) {
printf("ca chie creation socket client\n" );
exit(0);
}
if (connect (fproxy, (struct sockaddr *) &proxySock,sizeof(proxySock))<0) {
printf("ca chie demande de connection\n" );
exit(0);
}
if (DEBUG) {
printf("proxy : %d\n", fproxy);
}
if ( telnet_init() == CONN_OK ) {
fcntl(fproxy, F_GETFL, &flags);
flags |= O_NONBLOCK;
fcntl(fproxy, F_SETFL, &flags);
do {
FD_ZERO(&fdsr);
FD_SET(fcurrent, &fdsr);
FD_SET(fproxy, &fdsr);
if (DEBUG) printf("now wait ... \n" );
ret = select(MAX(fcurrent, fproxy) + 1, &fdsr, 0, 0, 0);
if (ret <= 0) {
if (DEBUG) printf("on ferme\n" );
close(fproxy);
close(fcurrent);
break;
}
len = 0;
if ( FD_ISSET(fcurrent,&fdsr) )
len = forward(fcurrent, fproxy);
if ( FD_ISSET(fproxy,&fdsr) )
len = forward(fproxy, fcurrent);
} while (len);
if (DEBUG) printf("on ferme\n" );
close(fcurrent);
close(fproxy);
} else {
if (DEBUG) printf("on ferme\n" );
close(fcurrent);
close(fproxy);
}
}
return 0;
}
int get_prompt(int fd)
{
int nl, nr, n=PACKET_SIZE;
char deb_ptr[PACKET_SIZE];
char *ptr = deb_ptr;
nl = n;
while (nl > 0) {
nr = read(fd, ptr, nl);
if (nr < 0) return nr; /* error */
else if (nr == 0) break;
nl -= nr;
ptr += nr;
if (strstr(ptr-10,PROMPT)) return CONN_OK;
}
return CONN_FAILED;
}
int get_connected(int fd, char *deb_ptr, int n)
{
int nl, nr;
char *ptr = deb_ptr, *ptr2;
char conn_prompt_ok_string[PACKET_SIZE];
sprintf(conn_prompt_ok_string,"%s %s.\r\n",CONN_PROMPT_OK, target_host);
nl = n;
while (nl > 0) {
nr = read(fd, ptr, nl);
ptr[nr] = 0x00;
if ( DEBUG ) printf("->%s<-\n", ptr);
if (nr < 0) return nr; /* error */
else if (nr == 0) break;
nl -= nr;
ptr += nr;
if ( ptr2 = strstr(deb_ptr,conn_prompt_ok_string) ) {
ptr2 += strlen(conn_prompt_ok_string);
if ( DEBUG ) printf("->%s<-",ptr2);
writen(fcurrent, ptr2, strlen(ptr2));
return CONN_OK;
}
if ( strstr(ptr-10,PROMPT) ) return CONN_FAILED;
}
return CONN_FAILED;
}
int telnet_init(void)
{
char option[] = { IAC, WILL, TELOPT_BINARY };
int szo = sizeof(option);
unsigned char buf[PACKET_SIZE + 1];
int n , ret;
/* force binary on the socket */
if (DEBUG) printf("sending options ..." );
writen(fproxy, option, szo);
option[1] = DO;
writen(fproxy, option, szo);
if (DEBUG) printf("reading header ..." );
n = get_prompt(fproxy);
if (DEBUG) printf("connected proxy !!\n" );
sprintf(buf,"connect %s %d\n", target_host, target_port);
writen(fproxy, buf, strlen(buf));
ret = get_connected(fproxy, buf, PACKET_SIZE);
if (DEBUG) printf("connected target ? %s\n",(ret==CONN_OK?"oui":"non" ));
return ret;
}
int writen(int fd, char *ptr, int n)
{
int nl, nw;
nl = n;
while ( nl > 0 ) {
nw = write(fd, ptr, nl);
if ( nw <= 0 )
return nw; /*error*/
nl -= nw;
ptr += nw;
}
return (n-nl);
}
int readn(int fd, char *ptr, int n){
int nl, nr;
nl = n;
while ( nl > 0 ) {
nr = read(fd,ptr,nl);
if (nr < 0 ) {
if ( nr == -1 ) {
*ptr = 0x00;
return (n-nl);
}
return nr; /*error*/
} else {
if ( nr == 0 )
break;
}
nl -= nr;
ptr += nr;
}
*ptr = 0x00;
return (n-nl);
}
int forward(int fin, int fout)
{
int total=0, len=0, i = 0;
char buffer[PACKET_SIZE + 1];
char *ptr;
if (DEBUG) printf ( "^[[31m%d -> %d\n^[[30m",fin,fout);
do {
len = readn(fin, buffer, PACKET_SIZE);
buffer[len] = 0x00;
if ( ptr = strstr(buffer, CONN_CLOSED) ) {
if ( DEBUG ) printf("----> '%s' found\n",CONN_CLOSED);
*ptr=0x00;
}
if ( ( len = strlen(buffer) ) != 0 ) {
if (TRACKING) printf("%d-%d->%s<--\n",i++,len,buffer);
writen(fout, buffer, len);
total += len;
}
} while (len == PACKET_SIZE);
return total;
}
|
