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/* $Id$
*
* redir - a utility for redirecting tcp connections
*
* Author: Nigel Metheringham
* Nigel.Metheringham@ThePLAnet.net
*
* Based on, but much modified from, code originally written by
* sammy@freenet.akron.oh.us - original header is below.
*
* redir is released under the GNU General Public license,
* version 2, or at your discretion, any later version.
*
*/
/* Redir, the code to which is below, is actually a horrible hack of my
* other cool network utility, daemon, which is actually a horrible hack
* of ora's using C sample code, 12.2.c. But, hey, they do something.
* (and that's the key.)
* -- Sammy (sammy@freenet.akron.oh.us)
*/
/* oh, incidentally, Sammy is now sammy@oh.verio.com */
/* 980601: dl9sau
* added some nice new features:
*
* --bind_addr=my.other.ip.address
* forces to use my.other.ip.address for the outgoing connection
*
* you can also specify, that redir listens not on all IP addresses of
* your system but only for the given one, i.e.:
* if my host has the addresses
* irc.thishost.my.domain and mail.thishost.my.domain
* but you want that your users do connect for the irc redir service
* only on irc.thishost.my.domain, then do it this way:
* redir irc.fu-berlin.de irc.thishost.mydomain:6667 6667
* my need was that:
* addr1.first.domain 6667 redirects to irc.first.net port 6667
* and addr2.second.domain 6667 redirects to irc.second.net port 6667
* while addr1 and addr2 are the same maschine and the ports can be equal.
*
* enjoy it!
* - thomas <thomas@x-berg.in-berlin.de>, <dl9sau@db0tud.ampr.org>
*
* btw: i tried without success implementing code for the following scenario:
* redir --force_addr irc.fu-berlin.de 6667 6667
* if "--force_addr" is given and a user connects to my system, that address
* of my system will be used on the outgoing connection that the user
* connected to.
* i was not successful to determine, to which of my addresses the user
* has connected.
*/
#define VERSION "2.0"
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <signal.h>
#include <getopt.h>
#include <syslog.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/time.h>
#include <sys/wait.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <errno.h>
#ifdef USE_TCP_WRAPPERS
#include <tcpd.h>
#endif
#define debug(x) if (dodebug) fprintf(stderr, x)
#define debug1(x,y) if (dodebug) fprintf(stderr, x, y)
/* let's set up some globals... */
int dodebug = 0;
int dosyslog = 0;
unsigned char reuse_addr = 1;
unsigned char linger_opt = 0;
char * bind_addr = NULL;
struct sockaddr_in addr_out;
int timeout = 0;
int ftp = 0;
int transproxy = 0;
char * ident = NULL;
#ifdef USE_TCP_WRAPPERS
struct request_info request;
int allow_severity = LOG_INFO;
int deny_severity = LOG_WARNING;
#endif /* USE_TCP_WRAPPERS */
#ifdef NEED_STRRCHR
#define strrchr rindex
#endif /* NEED_STRRCHR */
/* prototype anything needing it */
void do_accept(int servsock, struct sockaddr_in *target);
int bindsock(char *addr, int port, int fail);
#ifdef NEED_STRDUP
char *
strdup(char * str)
{
char * result;
if (result = (char *) malloc(strlen(str) + 1))
strcpy(result, str);
return result;
}
#endif /* NEED_STRDUP */
void
redir_usage(char *name)
{
fprintf(stderr,"usage:\n");
fprintf(stderr,
"\t%s --lport=<n> --cport=<n> [options]\n",
name);
fprintf(stderr, "\t%s --inetd --cport=<n>\n", name);
fprintf(stderr, "\n\tOptions are:-\n");
fprintf(stderr, "\t\t--lport=<n>\t\tport to listen on\n");
fprintf(stderr, "\t\t--laddr=IP\t\taddress of interface to listen on\n");
fprintf(stderr, "\t\t--cport=<n>\t\tport to connect to\n");
fprintf(stderr, "\t\t--caddr=<host>\t\tremote host to connect to\n");
fprintf(stderr, "\t\t--inetd\t\trun from inetd\n");
fprintf(stderr, "\t\t--debug\t\toutput debugging info\n");
fprintf(stderr, "\t\t--timeout=<n>\tset timeout to n seconds\n");
fprintf(stderr, "\t\t--syslog\tlog messages to syslog\n");
fprintf(stderr, "\t\t--name=<str>\ttag syslog messages with 'str'\n");
#ifdef USE_TCP_WRAPPERS
fprintf(stderr, "\t\t \tAlso used as service name for TCP wrappers\n");
#endif /* USE_TCP_WRAPPERS */
fprintf(stderr, "\t\t--bind_addr=IP\tbind() outgoing IP to given addr\n");
fprintf(stderr, "\t\t--ftp\t\tredirect passive ftp connections\n");
fprintf(stderr, "\t\t--transproxy\trun in linux's transparent proxy mode\n");
fprintf(stderr, "\n\tVersion %s - $Id$\n", VERSION);
exit(2);
}
void
parse_args(int argc,
char * argv[],
char ** target_addr,
int * target_port,
char ** local_addr,
int * local_port,
int * timeout,
int * dodebug,
int * inetd,
int * dosyslog,
char ** bind_addr,
int * ftp,
int * transproxy)
{
static struct option long_options[] = {
{"lport", required_argument, 0, 'l'},
{"laddr", required_argument, 0, 'a'},
{"cport", required_argument, 0, 'r'},
{"caddr", required_argument, 0, 'c'},
{"bind_addr", required_argument, 0, 'b'},
{"debug", no_argument, 0, 'd'},
{"timeout", required_argument, 0, 't'},
{"inetd", no_argument, 0, 'i'},
{"ident", required_argument, 0, 'n'},
{"name", required_argument, 0, 'n'},
{"syslog", no_argument, 0, 's'},
{"ftp", no_argument, 0, 'f'},
{"transproxy", no_argument, 0, 'p'},
{0,0,0,0} /* End marker */
};
int option_index = 0;
extern int optind;
int opt;
struct servent *portdesc;
char *lport = NULL;
char *tport = NULL;
*local_addr = NULL;
*target_addr = NULL;
*target_port = 0;
*local_port = 0;
while ((opt = getopt_long(argc, argv, "disfpn:t:b:a:l:r:c:",
long_options, &option_index)) != -1) {
switch (opt) {
case 'a':
*local_addr = optarg;
break;
case 'l':
lport = optarg;
break;
case 'r':
tport = optarg;
break;
case 'c':
*target_addr = optarg;
break;
case 'b':
*bind_addr = optarg;
break;
case 'd':
(*dodebug)++;
break;
case 't':
*timeout = atol(optarg);
break;
case 'i':
(*inetd)++;
break;
case 'n':
/* This is the ident which is added to syslog messages */
ident = optarg;
break;
case 's':
(*dosyslog)++;
break;
case 'f':
(*ftp)++;
break;
case 'p':
(*transproxy)++;
break;
default:
redir_usage(argv[0]);
exit(1);
break;
}
}
if(tport == NULL)
{
redir_usage(argv[0]);
exit(1);
}
if ((portdesc = getservbyname(tport, "tcp")) != NULL) {
*target_port = ntohs(portdesc->s_port);
} else {
*target_port = atol(tport);
}
/* only check local port if not running from inetd */
if(!(*inetd)) {
if(lport == NULL)
{
redir_usage(argv[0]);
exit(1);
}
if ((portdesc = getservbyname(lport, "tcp")) != NULL)
*local_port = ntohs(portdesc->s_port);
else
*local_port = atol(lport);
} /* if *inetd */
if (!ident) {
if ((ident = (char *) strrchr(argv[0], '/'))) {
ident++;
} else {
ident = argv[0];
}
}
openlog(ident, LOG_PID, LOG_DAEMON);
return;
}
/* with the --ftp option, this one changes passive mode replies from
the ftp server to point to a new redirector which we spawn */
void ftp_clean(int send, char *buf, unsigned long *bytes)
{
char *port_start;
int rporthi, lporthi;
int lportlo, rportlo;
int lport, rport;
int remip[4];
int localsock;
int socksize = sizeof(struct sockaddr_in);
int i;
struct sockaddr_in newsession;
struct sockaddr_in sockname;
/* is this a passive mode return ? */
if(strncmp(buf, "227", 3)) {
write(send, buf, (*bytes));
return;
}
/* get the outside interface so we can listen */
if(getsockname(send, (struct sockaddr *)&sockname, &socksize) != 0) {
perror("getsockname");
if (dosyslog)
syslog(LOG_ERR, "getsockname failed: %m");
exit(1);
}
/* parse the old address out of the buffer */
port_start = strchr(buf, '(');
sscanf(port_start, "(%d,%d,%d,%d,%d,%d", &remip[0], &remip[1],
&remip[2], &remip[3], &rporthi, &rportlo);
/* we need to listen on a port for the incoming connection.
we'll use this strategy. start at 32768 for hi byte, then
sweep using the low byte of our pid and try to bind 5 times.
if we can't bind to any of those ports, fail */
lporthi = 0x80;
lportlo = getpid() & 0xf0;
rport = (rporthi << 8) | rportlo;
for(i = 0, localsock = -1; ((localsock == -1) && (i < 5));
i++, lportlo++) {
lport = ((lporthi << 8) | lportlo) +1; /* weird off by 1 bug */
localsock = bindsock(inet_ntoa(sockname.sin_addr), lport, 1);
}
/* check to see if we bound */
if(localsock == -1) {
fprintf(stderr, "ftp: unable to bind new listening address\n");
exit(1);
}
(*bytes) = sprintf(buf, "227 Entering Passive Mode (%d,%d,%d,%d,%d,%d)\n",
sockname.sin_addr.s_addr & 0xff,
(sockname.sin_addr.s_addr >> 8) & 0xff,
(sockname.sin_addr.s_addr >> 16) & 0xff,
sockname.sin_addr.s_addr >> 24, lporthi, lportlo);
newsession.sin_port = htons(rport);
newsession.sin_family = AF_INET;
newsession.sin_addr.s_addr = remip[0] | (remip[1] << 8)
| (remip[2] << 16) | (remip[3] << 24);
debug1("ftp server ip: %s\n", inet_ntoa(newsession.sin_addr));
debug1("ftp server port: %d\n", rport);
debug1("listening on port %d\n", lport);
debug1("listening on addr %s\n",
inet_ntoa(sockname.sin_addr));
/* now that we're bound and listening, we can safely send the new
passive string without fear of them getting a connection
refused. */
write(send, buf, (*bytes));
/* turn off ftp checking while the data connection is active */
ftp = 0;
do_accept(localsock, &newsession);
close(localsock);
ftp = 1;
return;
}
void
copyloop(int insock,
int outsock,
int timeout_secs)
{
fd_set iofds;
fd_set c_iofds;
int max_fd; /* Maximum numbered fd used */
struct timeval timeout;
unsigned long bytes;
unsigned long bytes_in = 0;
unsigned long bytes_out = 0;
unsigned int start_time, end_time;
char buf[4096];
/* Record start time */
start_time = (unsigned int) time(NULL);
/* Set up timeout */
timeout.tv_sec = timeout_secs;
timeout.tv_usec = 0;
/* file descriptor bits */
FD_ZERO(&iofds);
FD_SET(insock, &iofds);
FD_SET(outsock, &iofds);
if (insock > outsock) {
max_fd = insock;
} else {
max_fd = outsock;
}
debug1("Entering copyloop() - timeout is %d\n", timeout_secs);
while(1) {
(void) memcpy(&c_iofds, &iofds, sizeof(iofds));
if (select(max_fd + 1,
&c_iofds,
(fd_set *)0,
(fd_set *)0,
(timeout_secs ? &timeout : NULL)) <= 0) {
/* syslog(LLEV,"connection timeout: %d sec",timeout.tv_sec);*/
break;
}
if(FD_ISSET(insock, &c_iofds)) {
if((bytes = read(insock, buf, sizeof(buf))) <= 0)
break;
if(write(outsock, buf, bytes) != bytes)
break;
bytes_out += bytes;
}
if(FD_ISSET(outsock, &c_iofds)) {
if((bytes = read(outsock, buf, sizeof(buf))) <= 0)
break;
/* if we're correcting for PASV on ftp redirections, then
fix buf and bytes to have the new address, among other
things */
if(ftp)
ftp_clean(insock, buf, &bytes);
else
if(write(insock, buf, bytes) != bytes)
break;
bytes_in += bytes;
}
}
debug("Leaving main copyloop\n");
/*
setsockopt(insock, SOL_SOCKET, SO_REUSEADDR, &reuse_addr, sizeof(reuse_addr));
setsockopt(insock, SOL_SOCKET, SO_LINGER, &linger_opt, sizeof(SO_LINGER));
setsockopt(outsock, SOL_SOCKET, SO_REUSEADDR, &reuse_addr, sizeof(reuse_addr));
setsockopt(outsock, SOL_SOCKET, SO_LINGER, &linger_opt, sizeof(SO_LINGER));
*/
shutdown(insock,0);
shutdown(outsock,0);
close(insock);
close(outsock);
debug("copyloop - sockets shutdown and closed\n");
end_time = (unsigned int) time(NULL);
debug1("copyloop - connect time: %8d seconds\n", end_time - start_time);
debug1("copyloop - transfer in: %8ld bytes\n", bytes_in);
debug1("copyloop - transfer out: %8ld bytes\n", bytes_out);
if (dosyslog) {
syslog(LOG_NOTICE, "disconnect %d secs, %ld in %ld out",
(end_time - start_time), bytes_in, bytes_out);
}
return;
}
/* lwait for a connection and move into copyloop... again,
passive ftp's will call this, so we don't dupilcate it. */
void
do_accept(int servsock, struct sockaddr_in *target)
{
int clisock;
int targetsock;
struct sockaddr_in client;
int clientlen = sizeof(client);
debug("top of accept loop\n");
if ((clisock = accept(servsock, (struct sockaddr *) &client,
&clientlen)) < 0) {
perror("server: accept");
if (dosyslog)
syslog(LOG_ERR, "accept failed: %m");
return;
}
debug1("peer IP is %s\n", inet_ntoa(client.sin_addr));
debug1("peer socket is %d\n", ntohs(client.sin_port));
/*
* Double fork here so we don't have to wait later
* This detaches us from our parent so that the parent
* does not need to pick up dead kids later.
*
* This needs to be done before the hosts_access stuff, because
* extended hosts_access options expect to be run from a child.
*/
switch(fork())
{
case -1: /* Error */
perror("(server) fork");
if (dosyslog)
syslog(LOG_ERR, "(server) fork failed: %m");
_exit(1);
case 0: /* Child */
break;
default: /* Parent */
{
int status;
/* Wait for child (who has forked off grandchild) */
(void) wait(&status);
/* Close sockets to prevent confusion */
close(clisock);
return;
}
}
/* We are now the first child. Fork again and exit */
switch(fork())
{
case -1: /* Error */
perror("(child) fork");
if (dosyslog)
syslog(LOG_ERR, "(child) fork failed: %m");
_exit(1);
case 0: /* Child */
break;
default: /* Parent */
_exit(0);
}
/* We are now the grandchild */
#ifdef USE_TCP_WRAPPERS
request_init(&request, RQ_DAEMON, ident, RQ_FILE, clisock, 0);
sock_host(&request);
sock_hostname(&request);
sock_hostaddr(&request);
if (!hosts_access(&request)) {
refuse(&request);
_exit(0);
}
if (dosyslog)
syslog(LOG_INFO, "accepted connect from %s", eval_client(&request));
#endif /* USE_TCP_WRAPPERS */
if ((targetsock = socket(AF_INET, SOCK_STREAM, 0)) < 0) {
perror("target: socket");
if (dosyslog)
syslog(LOG_ERR, "socket failed: %m");
_exit(1);
}
if(transproxy) {
memcpy(&addr_out, &client, sizeof(struct sockaddr_in));
addr_out.sin_port = 0;
}
if (bind_addr || transproxy) {
/* this only makes sense if an outgoing IP addr has been forced;
* at this point, we have a valid targetsock to bind() to.. */
/* also, if we're in transparent proxy mode, this option
never makes sense */
if (bind(targetsock, (struct sockaddr *) &addr_out,
sizeof(struct sockaddr_in)) < 0) {
perror("bind_addr: cannot bind to forcerd outgoing addr");
if (dosyslog)
syslog(LOG_ERR, "bind failed: %m");
_exit(1);
}
debug1("outgoing IP is %s\n", inet_ntoa(addr_out.sin_addr));
}
if (connect(targetsock, (struct sockaddr *) target,
sizeof(struct sockaddr_in)) < 0) {
perror("target: connect");
if (dosyslog)
syslog(LOG_ERR, "bind failed: %m");
_exit(1);
}
debug1("connected to %s\n", inet_ntoa(target->sin_addr));
/* thanks to Anders Vannman for the fix to make proper syslogging
happen here... */
if (dosyslog) {
char tmp1[20], tmp2[20];
strcpy(tmp1, inet_ntoa(client.sin_addr));
strcpy(tmp2, inet_ntoa(target->sin_addr));
syslog(LOG_NOTICE, "connecting %s/%d to %s/%d",
tmp1, ntohs(client.sin_port),
tmp2, ntohs(target->sin_port));
}
copyloop(clisock, targetsock, timeout);
exit(0); /* Exit after copy */
}
/* bind to a new socket, we do this out here because passive-fixups
are going to call it too, and there's no sense dupliciting the
code. */
/* fail is true if we should just return a -1 on error, false if we
should bail. */
int bindsock(char *addr, int port, int fail)
{
int servsock;
struct sockaddr_in server;
/*
* Get a socket to work with. This socket will
* be in the Internet domain, and will be a
* stream socket.
*/
if ((servsock = socket(AF_INET, SOCK_STREAM, 0)) < 0) {
if(fail) {
return -1;
}
else {
perror("server: socket");
if (dosyslog)
syslog(LOG_ERR, "socket failed: %m");
exit(1);
}
}
server.sin_family = AF_INET;
server.sin_port = htons(port);
if (addr != NULL) {
struct hostent *hp;
debug1("listening on %s\n", addr);
if ((hp = gethostbyname(addr)) == NULL) {
fprintf(stderr, "%s: cannot resolve hostname.\n", addr);
exit(1);
}
memcpy(&server.sin_addr, hp->h_addr, hp->h_length);
} else {
debug("local IP is default\n");
server.sin_addr.s_addr = htonl(inet_addr("0.0.0.0"));
}
setsockopt(servsock, SOL_SOCKET, SO_REUSEADDR, &reuse_addr, sizeof(reuse_addr));
setsockopt(servsock, SOL_SOCKET, SO_LINGER, &linger_opt, sizeof(SO_LINGER));
/*
* Try to bind the address to the socket.
*/
if (bind(servsock, (struct sockaddr *) &server,
sizeof(server)) < 0) {
if(fail) {
close(servsock);
return -1;
} else {
perror("server: bind");
if (dosyslog)
syslog(LOG_ERR, "bind failed: %m");
exit(1);
}
}
/*
* Listen on the socket.
*/
if (listen(servsock, 10) < 0) {
if(fail) {
close(servsock);
return -1;
} else {
perror("server: listen");
if (dosyslog)
syslog(LOG_ERR, "listen failed: %m");
exit(1);
}
}
return servsock;
}
int
main(int argc, char *argv[])
{
struct sockaddr_in target;
char *target_addr;
int target_port;
char *local_addr;
int local_port;
int inetd = 0;
char * target_ip;
char * ip_to_target;
debug("parse args\n");
parse_args(argc, argv, &target_addr, &target_port, &local_addr,
&local_port, &timeout, &dodebug, &inetd, &dosyslog, &bind_addr,
&ftp, &transproxy);
/* Set up target */
target.sin_family = AF_INET;
target.sin_port = htons(target_port);
if (target_addr != NULL) {
struct hostent *hp;
debug1("target is %s\n", target_addr);
if ((hp = gethostbyname(target_addr)) == NULL) {
fprintf(stderr, "%s: host unknown.\n", target_addr);
exit(1);
}
memcpy(&target.sin_addr, hp->h_addr, hp->h_length);
} else {
debug("target is default\n");
target.sin_addr.s_addr = htonl(inet_addr("0.0.0.0"));
}
target_ip = strdup(inet_ntoa(target.sin_addr));
debug1("target IP address is %s\n", target_ip);
debug1("target port is %d\n", target_port);
/* Set up outgoing IP addr (optional);
* we have to wait for bind until targetsock = socket() is done
*/
if (bind_addr && !transproxy) {
struct hostent *hp;
fprintf(stderr, "bind_addr is %s\n", bind_addr);
addr_out.sin_family = AF_INET;
addr_out.sin_port = 0;
if ((hp = gethostbyname(bind_addr)) == NULL) {
fprintf(stderr, "%s: cannot resolve forced outgoing IP address.\n", bind_addr);
exit(1);
}
memcpy(&addr_out.sin_addr, hp->h_addr, hp->h_length);
ip_to_target = strdup(inet_ntoa(addr_out.sin_addr));
debug1("IP address for target is %s\n", ip_to_target);
}
if (inetd) {
int targetsock;
struct sockaddr_in client;
int client_size = sizeof(client);
#ifdef USE_TCP_WRAPPERS
request_init(&request, RQ_DAEMON, ident, RQ_FILE, 0, 0);
sock_host(&request);
sock_hostname(&request);
sock_hostaddr(&request);
if (!hosts_access(&request))
refuse(&request);
#endif /* USE_TCP_WRAPPERS */
if (!getpeername(0, (struct sockaddr *) &client, &client_size)) {
debug1("peer IP is %s\n", inet_ntoa(client.sin_addr));
debug1("peer socket is %d\n", ntohs(client.sin_port));
}
if ((targetsock = socket(AF_INET, SOCK_STREAM, 0)) < 0) {
perror("target: socket");
if (dosyslog)
syslog(LOG_ERR, "targetsock failed: %m");
exit(1);
}
if(transproxy) {
memcpy(&addr_out, &client, sizeof(struct sockaddr_in));
addr_out.sin_port = 0;
}
if (bind_addr || transproxy) {
/* this only makes sense if an outgoing IP addr has been forced;
* at this point, we have a valid targetsock to bind() to.. */
if (bind(targetsock, (struct sockaddr *) &addr_out,
sizeof(addr_out)) < 0) {
perror("bind_addr: cannot bind to forcerd outgoing addr");
if (dosyslog)
syslog(LOG_ERR, "bind failed: %m");
exit(1);
}
debug1("outgoing IP is %s\n", inet_ntoa(addr_out.sin_addr));
}
if (connect(targetsock, (struct sockaddr *) &target,
sizeof(target)) < 0) {
perror("target: connect");
if (dosyslog)
syslog(LOG_ERR, "connect failed: %m");
exit(1);
}
if (dosyslog) {
syslog(LOG_NOTICE, "connecting %s/%d to %s/%d",
inet_ntoa(client.sin_addr), ntohs(client.sin_port),
target_ip, ntohs(target.sin_port));
}
/* Just start copying - one side of the loop is stdin - 0 */
copyloop(0, targetsock, timeout);
} else {
int servsock;
if(local_addr)
servsock = bindsock(local_addr, local_port, 0);
else
servsock = bindsock(NULL, local_port, 0);
/*
* Accept connections. When we accept one, ns
* will be connected to the client. client will
* contain the address of the client.
*/
while (1)
do_accept(servsock, &target);
}
/* this should really never be reached */
exit(0);
}
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