/*
* Sample transparent proxy program.
*
* Sample implementation of a program which intercepts a TCP connectiona and
* just echos all data back to the origin. Written to work via inetd as a
* "nonwait" program running as root; ie.
* tcpmux stream tcp nowait root /usr/local/bin/proxy proxy
* with a NAT rue like this:
* rdr smc0 0/0 port 80 -> 127.0.0.1/32 port 1
*/
#include <stdio.h>
#include <string.h>
#include <fcntl.h>
#include <syslog.h>
#if !defined(__SVR4) && !defined(__svr4__)
#include <strings.h>
#else
#include <sys/byteorder.h>
#endif
#include <sys/types.h>
#include <sys/time.h>
#include <sys/param.h>
#include <stdlib.h>
#include <unistd.h>
#include <stddef.h>
#include <sys/socket.h>
#include <sys/ioctl.h>
#if defined(sun) && (defined(__svr4__) || defined(__SVR4))
# include <sys/ioccom.h>
# include <sys/sysmacros.h>
#endif
#include <netinet/in.h>
#include <netinet/in_systm.h>
#include <netinet/ip.h>
#include <netinet/tcp.h>
#include <net/if.h>
#include <netdb.h>
#include <arpa/nameser.h>
#include <arpa/inet.h>
#include <resolv.h>
#include <ctype.h>
#include "netinet/ip_compat.h"
#include "netinet/ip_fil.h"
#include "netinet/ip_nat.h"
#include "netinet/ip_state.h"
#include "netinet/ip_proxy.h"
#include "netinet/ip_nat.h"
#include "netinet/ipl.h"
main(argc, argv)
int argc;
char *argv[];
{
struct sockaddr_in sin, sloc, sout;
ipfobj_t obj;
natlookup_t natlook;
char buffer[512];
int namelen, fd, n;
/*
* get IP# and port # of the remote end of the connection (at the
* origin).
*/
namelen = sizeof(sin);
if (getpeername(0, (struct sockaddr *)&sin, &namelen) == -1) {
perror("getpeername");
exit(-1);
}
/*
* get IP# and port # of the local end of the connection (at the
* man-in-the-middle).
*/
namelen = sizeof(sin);
if (getsockname(0, (struct sockaddr *)&sloc, &namelen) == -1) {
perror("getsockname");
exit(-1);
}
bzero((char *)&obj, sizeof(obj));
obj.ipfo_rev = IPFILTER_VERSION;
obj.ipfo_size = sizeof(natlook);
obj.ipfo_ptr = &natlook;
obj.ipfo_type = IPFOBJ_NATLOOKUP;
/*
* Build up the NAT natlookup structure.
*/
bzero((char *)&natlook, sizeof(natlook));
natlook.nl_outip = sin.sin_addr;
natlook.nl_inip = sloc.sin_addr;
natlook.nl_flags = IPN_TCP;
natlook.nl_outport = sin.sin_port;
natlook.nl_inport = sloc.sin_port;
/*
* Open the NAT device and lookup the mapping pair.
*/
fd = open(IPNAT_NAME, O_RDONLY);
if (ioctl(fd, SIOCGNATL, &obj) == -1) {
perror("ioctl(SIOCGNATL)");
exit(-1);
}
#define DO_NAT_OUT
#ifdef DO_NAT_OUT
if (argc > 1)
do_nat_out(0, 1, fd, &natlook, argv[1]);
#else
/*
* Log it
*/
syslog(LOG_DAEMON|LOG_INFO, "connect to %s,%d",
inet_ntoa(natlook.nl_realip), ntohs(natlook.nl_realport));
printf("connect to %s,%d\n",
inet_ntoa(natlook.nl_realip), ntohs(natlook.nl_realport));
/*
* Just echo data read in from stdin to stdout
*/
while ((n = read(0, buffer, sizeof(buffer))) > 0)
if (write(1, buffer, n) != n)
break;
close(0);
#endif
}
#ifdef DO_NAT_OUT
do_nat_out(in, out, fd, nlp, extif)
int fd;
natlookup_t *nlp;
char *extif;
{
nat_save_t ns, *nsp = &ns;
struct sockaddr_in usin;
u_32_t sum1, sum2, sumd;
int onoff, ofd, slen;
ipfobj_t obj;
ipnat_t *ipn;
nat_t *nat;
bzero((char *)&ns, sizeof(ns));
nat = &ns.ipn_nat;
nat->nat_p = IPPROTO_TCP;
nat->nat_dir = NAT_OUTBOUND;
if ((extif != NULL) && (*extif != '\0')) {
strncpy(nat->nat_ifnames[0], extif,
sizeof(nat->nat_ifnames[0]));
strncpy(nat->nat_ifnames[1], extif,
sizeof(nat->nat_ifnames[1]));
nat->nat_ifnames[0][sizeof(nat->nat_ifnames[0]) - 1] = '\0';
nat->nat_ifnames[1][sizeof(nat->nat_ifnames[1]) - 1] = '\0';
}
ofd = socket(AF_INET, SOCK_DGRAM, 0);
bzero((char *)&usin, sizeof(usin));
usin.sin_family = AF_INET;
usin.sin_addr = nlp->nl_realip;
usin.sin_port = nlp->nl_realport;
(void) connect(ofd, (struct sockaddr *)&usin, sizeof(usin));
slen = sizeof(usin);
(void) getsockname(ofd, (struct sockaddr *)&usin, &slen);
close(ofd);
printf("local IP# to use: %s\n", inet_ntoa(usin.sin_addr));
if ((ofd = socket(AF_INET, SOCK_STREAM, 0)) == -1)
perror("socket");
usin.sin_port = 0;
if (bind(ofd, (struct sockaddr *)&usin, sizeof(usin)))
perror("bind");
slen = sizeof(usin);
if (getsockname(ofd, (struct sockaddr *)&usin, &slen))
perror("getsockname");
printf("local port# to use: %d\n", ntohs(usin.sin_port));
nat->nat_inip = usin.sin_addr;
nat->nat_outip = nlp->nl_outip;
nat->nat_oip = nlp->nl_realip;
sum1 = LONG_SUM(ntohl(usin.sin_addr.s_addr)) + ntohs(usin.sin_port);
sum2 = LONG_SUM(ntohl(nat->nat_outip.s_addr)) + ntohs(nlp->nl_outport);
CALC_SUMD(sum1, sum2, sumd);
nat->nat_sumd[0] = (sumd & 0xffff) + (sumd >> 16);
nat->nat_sumd[1] = nat->nat_sumd[0];
sum1 = LONG_SUM(ntohl(usin.sin_addr.s_addr));
sum2 = LONG_SUM(ntohl(nat->nat_outip.s_addr));
CALC_SUMD(sum1, sum2, sumd);
nat->nat_ipsumd = (sumd & 0xffff) + (sumd >> 16);
nat->nat_inport = usin.sin_port;
nat->nat_outport = nlp->nl_outport;
nat->nat_oport = nlp->nl_realport;
nat->nat_flags = IPN_TCPUDP;
bzero((char *)&obj, sizeof(obj));
obj.ipfo_rev = IPFILTER_VERSION;
obj.ipfo_size = sizeof(*nsp);
obj.ipfo_ptr = nsp;
obj.ipfo_type = IPFOBJ_NATSAVE;
onoff = 1;
if (ioctl(fd, SIOCSTLCK, &onoff) == 0) {
if (ioctl(fd, SIOCSTPUT, &obj) != 0)
perror("SIOCSTPUT");
onoff = 0;
if (ioctl(fd, SIOCSTLCK, &onoff) != 0)
perror("SIOCSTLCK");
}
usin.sin_addr = nlp->nl_realip;
usin.sin_port = nlp->nl_realport;
printf("remote end for connection: %s,%d\n", inet_ntoa(usin.sin_addr),
ntohs(usin.sin_port));
fflush(stdout);
if (connect(ofd, (struct sockaddr *)&usin, sizeof(usin)))
perror("connect");
relay(in, out, ofd);
}
relay(in, out, net)
int in, out, net;
{
char netbuf[1024], outbuf[1024];
char *nwptr, *nrptr, *owptr, *orptr;
size_t nsz, osz;
fd_set rd, wr;
int i, n, maxfd;
n = 0;
maxfd = in;
if (out > maxfd)
maxfd = out;
if (net > maxfd)
maxfd = net;
nrptr = netbuf;
nwptr = netbuf;
nsz = sizeof(netbuf);
orptr = outbuf;
owptr = outbuf;
osz = sizeof(outbuf);
while (n >= 0) {
FD_ZERO(&rd);
FD_ZERO(&wr);
if (nrptr - netbuf < sizeof(netbuf))
FD_SET(in, &rd);
if (orptr - outbuf < sizeof(outbuf))
FD_SET(net, &rd);
if (nsz < sizeof(netbuf))
FD_SET(net, &wr);
if (osz < sizeof(outbuf))
FD_SET(out, &wr);
n = select(maxfd + 1, &rd, &wr, NULL, NULL);
if ((n > 0) && FD_ISSET(in, &rd)) {
i = read(in, nrptr, sizeof(netbuf) - (nrptr - netbuf));
if (i <= 0)
break;
nsz -= i;
nrptr += i;
n--;
}
if ((n > 0) && FD_ISSET(net, &rd)) {
i = read(net, orptr, sizeof(outbuf) - (orptr - outbuf));
if (i <= 0)
break;
osz -= i;
orptr += i;
n--;
}
if ((n > 0) && FD_ISSET(out, &wr)) {
i = write(out, owptr, orptr - owptr);
if (i <= 0)
break;
osz += i;
if (osz == sizeof(outbuf) || owptr == orptr) {
orptr = outbuf;
owptr = outbuf;
} else
owptr += i;
n--;
}
if ((n > 0) && FD_ISSET(net, &wr)) {
i = write(net, nwptr, nrptr - nwptr);
if (i <= 0)
break;
nsz += i;
if (nsz == sizeof(netbuf) || nwptr == nrptr) {
nrptr = netbuf;
nwptr = netbuf;
} else
nwptr += i;
}
}
close(net);
close(out);
close(in);
}
#endif
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