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/* $OpenBSD: netcat.c,v 1.39 2001/10/28 19:52:04 jakob Exp $ */
/*
* Copyright (c) 2001 Eric Jackson <ericj@monkey.org>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
/*
* Re-written nc(1) for OpenBSD. Original implementation by
* *Hobbit* <hobbit@avian.org>.
*/
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/time.h>
#include <netinet/in.h>
#include <arpa/telnet.h>
#include <err.h>
#include <errno.h>
#include <netdb.h>
#include <poll.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#define PORT_MAX 65535
/* Command Line Options */
int iflag; /* Interval Flag */
int kflag; /* More than one connect */
int lflag; /* Bind to local port */
int nflag; /* Dont do name lookup */
char *pflag; /* Localport flag */
int rflag; /* Random ports flag */
char *sflag; /* Source Address */
int tflag; /* Telnet Emulation */
int uflag; /* UDP - Default to TCP */
int vflag; /* Verbosity */
int xflag; /* Socks proxy */
int zflag; /* Port Scan Flag */
int timeout;
int family = AF_UNSPEC;
char *portlist[PORT_MAX];
ssize_t atomicio __P((ssize_t (*)(), int, void *, size_t));
void atelnet __P((int, unsigned char *, unsigned int));
void build_ports __P((char *));
void help __P((void));
int local_listen __P((char *, char *, struct addrinfo));
void readwrite __P((int));
int remote_connect __P((char *, char *, struct addrinfo));
int udptest __P((int));
void usage __P((int));
int
main(int argc, char *argv[])
{
int ch, s, ret;
char *host, *uport, *endp;
struct addrinfo hints;
struct servent *sv;
socklen_t len;
struct sockaddr *cliaddr;
char *proxy;
char *proxyhost, *proxyport;
struct addrinfo proxyhints;
ret = 1;
s = 0;
host = NULL;
uport = NULL;
endp = NULL;
sv = NULL;
while ((ch = getopt(argc, argv, "46hi:klnp:rs:tuvw:x:z")) != -1) {
switch (ch) {
case '4':
family = AF_INET;
break;
case '6':
family = AF_INET6;
break;
case 'h':
help();
break;
case 'i':
iflag = (int)strtoul(optarg, &endp, 10);
if (iflag < 0 || *endp != '\0')
errx(1, "interval cannot be negative");
break;
case 'k':
kflag = 1;
break;
case 'l':
lflag = 1;
break;
case 'n':
nflag = 1;
break;
case 'p':
pflag = optarg;
break;
case 'r':
rflag = 1;
break;
case 's':
sflag = optarg;
break;
case 't':
tflag = 1;
break;
case 'u':
uflag = 1;
break;
case 'v':
vflag = 1;
break;
case 'w':
timeout = (int)strtoul(optarg, &endp, 10);
if (timeout < 0 || *endp != '\0')
errx(1, "timeout cannot be negative");
break;
case 'x':
xflag = 1;
proxy = strdup(optarg);
break;
case 'z':
zflag = 1;
break;
default:
usage(1);
}
}
argc -= optind;
argv += optind;
/* Cruft to make sure options are clean, and used properly. */
if (argv[0] && !argv[1]) {
if (!lflag)
usage(1);
uport = argv[0];
host = NULL;
} else if (argv[0] && argv[1]) {
host = argv[0];
uport = argv[1];
} else
usage(1);
if (lflag && sflag)
errx(1, "cannot use -s and -l");
if (lflag && pflag)
errx(1, "cannot use -p and -l");
if (lflag && zflag)
errx(1, "cannot use -z and -l");
if (!lflag && kflag)
errx(1, "must use -l with -k");
/* Initialize addrinfo structure */
memset(&hints, 0, sizeof(struct addrinfo));
hints.ai_family = family;
hints.ai_socktype = uflag ? SOCK_DGRAM : SOCK_STREAM;
hints.ai_protocol = uflag ? IPPROTO_UDP : IPPROTO_TCP;
if (nflag)
hints.ai_flags |= AI_NUMERICHOST;
if (xflag) {
if (uflag)
errx(1, "no proxy support for UDP mode");
if (lflag)
errx(1, "no proxy support for listen");
/* XXX IPv6 transport to proxy would probably work */
if (family == AF_INET6)
errx(1, "no proxy support for IPv6");
if (sflag)
errx(1, "no proxy support for local source address");
proxyhost = strsep(&proxy, ":");
proxyport = proxy;
memset(&proxyhints, 0, sizeof(struct addrinfo));
proxyhints.ai_family = family;
proxyhints.ai_socktype = SOCK_STREAM;
proxyhints.ai_protocol = IPPROTO_TCP;
if (nflag)
proxyhints.ai_flags |= AI_NUMERICHOST;
}
if (lflag) {
int connfd;
ret = 0;
/* Allow only one connection at a time, but stay alive */
for (;;) {
if ((s = local_listen(host, uport, hints)) < 0)
err(1, NULL);
/*
* For UDP, we will use recvfrom() initially
* to wait for a caller, then use the regular
* functions to talk to the caller.
*/
if (uflag) {
int rv;
char buf[1024];
struct sockaddr_storage z;
len = sizeof(z);
rv = recvfrom(s, buf, sizeof(buf), MSG_PEEK,
(struct sockaddr *)&z, &len);
if (rv < 0)
errx(1, "%s", strerror(errno));
rv = connect(s, (struct sockaddr *)&z, len);
if (rv < 0)
errx(1, "%s", strerror(errno));
connfd = s;
} else {
connfd = accept(s, (struct sockaddr *)&cliaddr,
&len);
}
readwrite(connfd);
close(connfd);
close(s);
if (!kflag)
break;
}
} else {
int i = 0;
/* construct the portlist[] array */
build_ports(uport);
/* Cycle through portlist, connecting to each port */
for (i = 0; portlist[i] != NULL; i++) {
if (s)
close(s);
if (xflag)
s = socks_connect(host, portlist[i], hints,
proxyhost, proxyport, proxyhints);
else
s = remote_connect(host, portlist[i], hints);
if (s < 0)
continue;
ret = 0;
if (vflag || zflag) {
/* For UDP, make sure we are connected */
if (uflag) {
if ((udptest(s)) == -1) {
ret = 1;
continue;
}
}
/* Don't lookup port if -n */
if (nflag)
sv = NULL;
else {
sv = getservbyport(
ntohs(atoi(portlist[i])),
uflag ? "udp" : "tcp");
}
printf("Connection to %s %s port [%s/%s] succeeded!\n",
host, portlist[i], uflag ? "udp" : "tcp",
sv ? sv->s_name : "*");
}
if (!zflag)
readwrite(s);
}
}
if (s)
close(s);
exit(ret);
}
/*
* remote_connect()
* Return's a socket connected to a remote host. Properly bind's to a local
* port or source address if needed. Return's -1 on failure.
*/
int
remote_connect(char *host, char *port, struct addrinfo hints)
{
struct addrinfo *res, *res0;
int s, error;
if ((error = getaddrinfo(host, port, &hints, &res)))
errx(1, "%s", gai_strerror(error));
res0 = res;
do {
if ((s = socket(res0->ai_family, res0->ai_socktype,
res0->ai_protocol)) < 0)
continue;
/* Bind to a local port or source address if specified */
if (sflag || pflag) {
struct addrinfo ahints, *ares;
if (!(sflag && pflag)) {
if (!sflag)
sflag = NULL;
else
pflag = NULL;
}
memset(&ahints, 0, sizeof(struct addrinfo));
ahints.ai_family = res0->ai_family;
ahints.ai_socktype = uflag ? SOCK_DGRAM : SOCK_STREAM;
ahints.ai_protocol = uflag ? IPPROTO_UDP : IPPROTO_TCP;
ahints.ai_flags = AI_PASSIVE;
if ((error = getaddrinfo(sflag, pflag, &ahints, &ares)))
errx(1, "%s", gai_strerror(error));
if (bind(s, (struct sockaddr *)ares->ai_addr,
ares->ai_addrlen) < 0) {
errx(1, "bind failed: %s", strerror(errno));
freeaddrinfo(ares);
continue;
}
freeaddrinfo(ares);
}
if (connect(s, res0->ai_addr, res0->ai_addrlen) == 0)
break;
close(s);
s = -1;
} while ((res0 = res0->ai_next) != NULL);
freeaddrinfo(res);
return (s);
}
/*
* local_listen()
* Return's a socket listening on a local port, binds to specified source
* address. Return's -1 on failure.
*/
int
local_listen(char *host, char *port, struct addrinfo hints)
{
struct addrinfo *res, *res0;
int s, ret, x = 1;
int error;
/* Allow nodename to be null */
hints.ai_flags |= AI_PASSIVE;
/*
* In the case of binding to a wildcard address
* default to binding to an ipv4 address.
*/
if (host == NULL && hints.ai_family == AF_UNSPEC)
hints.ai_family = AF_INET;
if ((error = getaddrinfo(host, port, &hints, &res)))
errx(1, "%s", gai_strerror(error));
res0 = res;
do {
if ((s = socket(res0->ai_family, res0->ai_socktype,
res0->ai_protocol)) == 0)
continue;
ret = setsockopt(s, SOL_SOCKET, SO_REUSEPORT, &x, sizeof(x));
if (ret == -1)
err(1, NULL);
if (bind(s, (struct sockaddr *)res0->ai_addr,
res0->ai_addrlen) == 0)
break;
close(s);
s = -1;
} while ((res0 = res0->ai_next) != NULL);
if (!uflag) {
if (listen(s, 1) < 0)
errx(1, "%s", strerror(errno));
}
freeaddrinfo(res);
return (s);
}
/*
* readwrite()
* Loop that polls on the network file descriptor and stdin.
*/
void
readwrite(int nfd)
{
struct pollfd *pfd;
char buf[BUFSIZ];
int wfd = fileno(stdin), n, ret;
int lfd = fileno(stdout);
pfd = malloc(2 * sizeof(struct pollfd));
/* Setup Network FD */
pfd[0].fd = nfd;
pfd[0].events = POLLIN;
/* Setup STDIN FD */
pfd[1].fd = wfd;
pfd[1].events = POLLIN;
for (;;) {
if (iflag)
sleep(iflag);
if (poll(pfd, 2, timeout) < 0) {
close(nfd);
close(wfd);
free(pfd);
errx(1, "Polling Error");
}
if (pfd[0].revents & POLLIN) {
if ((n = read(nfd, buf, sizeof(buf))) <= 0) {
return;
} else {
if (tflag)
atelnet(nfd, buf, n);
if ((ret = atomicio(write, lfd, buf, n)) != n)
return;
}
}
if (pfd[1].revents & POLLIN) {
if ((n = read(wfd, buf, sizeof(buf))) <= 0) {
return;
} else
if((ret = atomicio(write, nfd, buf, n)) != n)
return;
}
}
}
/* Deal with RFC854 WILL/WONT DO/DONT negotiation */
void
atelnet(int nfd, unsigned char *buf, unsigned int size)
{
int ret;
unsigned char *p, *end;
unsigned char obuf[4];
end = buf + size;
obuf[0] = '\0';
for (p = buf; p < end; p++) {
if (*p != IAC)
break;
obuf[0] = IAC;
p++;
if ((*p == WILL) || (*p == WONT)) {
obuf[1] = DONT;
}
if ((*p == DO) || (*p == DONT)) {
obuf[1] = WONT;
}
if (obuf) {
p++;
obuf[2] = *p;
obuf[3] = '\0';
if ((ret = atomicio(write , nfd, obuf, 3)) != 3)
warnx("Write Error!");
obuf[0] = '\0';
}
}
}
/*
* build_ports()
* Build an array or ports in portlist[], listing each port
* that we should try to connect too.
*/
void
build_ports(char *p)
{
char *n, *endp;
int hi, lo, cp;
int x = 0;
if ((n = strchr(p, '-')) != NULL) {
if (lflag)
errx(1, "Cannot use -l with multiple ports!");
*n = '\0';
n++;
/* Make sure the ports are in order: lowest->highest */
hi = (int)strtoul(n, &endp, 10);
if (hi <= 0 || hi > PORT_MAX || *endp != '\0')
errx(1, "port range not valid");
lo = (int)strtoul(p, &endp, 10);
if (lo <= 0 || lo > PORT_MAX || *endp != '\0')
errx(1, "port range not valid");
if (lo > hi) {
cp = hi;
hi = lo;
lo = cp;
}
/* Load ports sequentially */
for (cp = lo; cp <= hi; cp++) {
portlist[x] = calloc(1, PORT_MAX);
sprintf(portlist[x], "%d", cp);
x++;
}
/* Randomly swap ports */
if (rflag) {
int y;
char *c;
for (x = 0; x <= (hi - lo); x++) {
y = (arc4random() & 0xFFFF) % (hi - lo);
c = portlist[x];
portlist[x] = portlist[y];
portlist[y] = c;
}
}
} else {
hi = (int)strtoul(p, &endp, 10);
if (hi <= 0 || hi > PORT_MAX || *endp != '\0')
errx(1, "port range not valid");
portlist[0] = calloc(1, PORT_MAX);
portlist[0] = p;
}
}
/*
* udptest()
* Do a few writes to see if the UDP port is there.
* XXX - Better way of doing this? Doesn't work for IPv6
* Also fails after around 100 ports checked.
*/
int
udptest(int s)
{
int i, rv, ret;
for (i=0; i <= 3; i++) {
if ((rv = write(s, "X", 1)) == 1)
ret = 1;
else
ret = -1;
}
return (ret);
}
void
help()
{
usage(0);
fprintf(stderr, "\tCommand Summary:\n\
\t-4 Use IPv4\n\
\t-6 Use IPv6\n\
\t-h This help text\n\
\t-i secs\t Delay interval for lines sent, ports scanned\n\
\t-k Keep inbound sockets open for multiple connects\n\
\t-l Listen mode, for inbound connects\n\
\t-n Suppress name/port resolutions\n\
\t-p port\t Specify local port for remote connects\n\
\t-r Randomize remote ports\n\
\t-s addr\t Local source address\n\
\t-t Answer TELNET negotiation\n\
\t-u UDP mode\n\
\t-v Verbose\n\
\t-w secs\t Timeout for connects and final net reads\n\
\t-x addr[:port]\tSpecify socks5 proxy address and port\n\
\t-z Zero-I/O mode [used for scanning]\n\
Port numbers can be individual or ranges: lo-hi [inclusive]\n");
exit(1);
}
void
usage(int ret)
{
fprintf(stderr, "usage: nc [-46hklnrtuvz] [-i interval] [-p source port]\n");
fprintf(stderr, "\t [-s ip address] [-w timeout] [-x proxy address [:port]]\n");
fprintf(stderr, "\t [hostname] [port[s...]]\n");
if (ret)
exit(1);
}
|