4.2BSD/usr/src/etc/telnetd.c
#ifndef lint
static char sccsid[] = "@(#)telnetd.c 4.26 (Berkeley) 83/08/06";
#endif
/*
* Stripped-down telnet server.
*/
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/wait.h>
#include <netinet/in.h>
#include <arpa/telnet.h>
#include <stdio.h>
#include <signal.h>
#include <errno.h>
#include <sgtty.h>
#include <netdb.h>
#define BELL '\07'
#define BANNER "\r\n\r\n4.2 BSD UNIX (%s)\r\n\r\r\n\r%s"
char hisopts[256];
char myopts[256];
char doopt[] = { IAC, DO, '%', 'c', 0 };
char dont[] = { IAC, DONT, '%', 'c', 0 };
char will[] = { IAC, WILL, '%', 'c', 0 };
char wont[] = { IAC, WONT, '%', 'c', 0 };
/*
* I/O data buffers, pointers, and counters.
*/
char ptyibuf[BUFSIZ], *ptyip = ptyibuf;
char ptyobuf[BUFSIZ], *pfrontp = ptyobuf, *pbackp = ptyobuf;
char netibuf[BUFSIZ], *netip = netibuf;
char netobuf[BUFSIZ], *nfrontp = netobuf, *nbackp = netobuf;
int pcc, ncc;
int pty, net;
int inter;
int reapchild();
extern char **environ;
extern int errno;
char line[] = "/dev/ptyp0";
struct sockaddr_in sin = { AF_INET };
main(argc, argv)
char *argv[];
{
int s, pid, options;
struct servent *sp;
sp = getservbyname("telnet", "tcp");
if (sp == 0) {
fprintf(stderr, "telnetd: tcp/telnet: unknown service\n");
exit(1);
}
sin.sin_port = sp->s_port;
argc--, argv++;
if (argc > 0 && !strcmp(*argv, "-d")) {
options |= SO_DEBUG;
argc--, argv++;
}
if (argc > 0) {
sin.sin_port = atoi(*argv);
if (sin.sin_port <= 0) {
fprintf(stderr, "telnetd: %s: bad port #\n", *argv);
exit(1);
}
sin.sin_port = htons((u_short)sin.sin_port);
}
#ifndef DEBUG
if (fork())
exit(0);
for (s = 0; s < 10; s++)
(void) close(s);
(void) open("/", 0);
(void) dup2(0, 1);
(void) dup2(0, 2);
{ int tt = open("/dev/tty", 2);
if (tt > 0) {
ioctl(tt, TIOCNOTTY, 0);
close(tt);
}
}
#endif
again:
s = socket(AF_INET, SOCK_STREAM, 0, 0);
if (s < 0) {
perror("telnetd: socket");;
sleep(5);
goto again;
}
if (options & SO_DEBUG)
if (setsockopt(s, SOL_SOCKET, SO_DEBUG, 0, 0) < 0)
perror("telnetd: setsockopt (SO_DEBUG)");
if (setsockopt(s, SOL_SOCKET, SO_KEEPALIVE, 0, 0) < 0)
perror("telnetd: setsockopt (SO_KEEPALIVE)");
while (bind(s, (caddr_t)&sin, sizeof (sin), 0) < 0) {
perror("telnetd: bind");
sleep(5);
}
signal(SIGCHLD, reapchild);
listen(s, 10);
for (;;) {
struct sockaddr_in from;
int s2, fromlen = sizeof (from);
s2 = accept(s, (caddr_t)&from, &fromlen);
if (s2 < 0) {
if (errno == EINTR)
continue;
perror("telnetd: accept");
sleep(1);
continue;
}
if ((pid = fork()) < 0)
printf("Out of processes\n");
else if (pid == 0) {
signal(SIGCHLD, SIG_DFL);
doit(s2, &from);
}
close(s2);
}
/*NOTREACHED*/
}
reapchild()
{
union wait status;
while (wait3(&status, WNOHANG, 0) > 0)
;
}
char *envinit[] = { "TERM=network", 0 };
int cleanup();
/*
* Get a pty, scan input lines.
*/
doit(f, who)
int f;
struct sockaddr_in *who;
{
char *cp = line, *host, *ntoa();
int i, p, cc, t;
struct sgttyb b;
struct hostent *hp;
for (i = 0; i < 16; i++) {
cp[strlen("/dev/ptyp")] = "0123456789abcdef"[i];
p = open(cp, 2);
if (p > 0)
goto gotpty;
}
fatal(f, "All network ports in use");
/*NOTREACHED*/
gotpty:
dup2(f, 0);
cp[strlen("/dev/")] = 't';
t = open("/dev/tty", 2);
if (t >= 0) {
ioctl(t, TIOCNOTTY, 0);
close(t);
}
t = open(cp, 2);
if (t < 0)
fatalperror(f, cp, errno);
ioctl(t, TIOCGETP, &b);
b.sg_flags = CRMOD|XTABS|ANYP;
ioctl(t, TIOCSETP, &b);
ioctl(p, TIOCGETP, &b);
b.sg_flags &= ~ECHO;
ioctl(p, TIOCSETP, &b);
hp = gethostbyaddr(&who->sin_addr, sizeof (struct in_addr),
who->sin_family);
if (hp)
host = hp->h_name;
else
host = ntoa(who->sin_addr);
if ((i = fork()) < 0)
fatalperror(f, "fork", errno);
if (i)
telnet(f, p);
close(f);
close(p);
dup2(t, 0);
dup2(t, 1);
dup2(t, 2);
close(t);
environ = envinit;
execl("/bin/login", "login", "-h", host, 0);
fatalperror(f, "/bin/login", errno);
/*NOTREACHED*/
}
fatal(f, msg)
int f;
char *msg;
{
char buf[BUFSIZ];
(void) sprintf(buf, "telnetd: %s.\n", msg);
(void) write(f, buf, strlen(buf));
exit(1);
}
fatalperror(f, msg, errno)
int f;
char *msg;
int errno;
{
char buf[BUFSIZ];
extern char *sys_errlist[];
(void) sprintf(buf, "%s: %s", msg, sys_errlist[errno]);
fatal(f, buf);
}
/*
* Main loop. Select from pty and network, and
* hand data to telnet receiver finite state machine.
*/
telnet(f, p)
{
int on = 1;
char hostname[32];
net = f, pty = p;
ioctl(f, FIONBIO, &on);
ioctl(p, FIONBIO, &on);
signal(SIGTSTP, SIG_IGN);
signal(SIGCHLD, cleanup);
/*
* Request to do remote echo.
*/
dooption(TELOPT_ECHO);
myopts[TELOPT_ECHO] = 1;
/*
* Show banner that getty never gave.
*/
gethostname(hostname, sizeof (hostname));
sprintf(nfrontp, BANNER, hostname, "");
nfrontp += strlen(nfrontp);
for (;;) {
int ibits = 0, obits = 0;
register int c;
/*
* Never look for input if there's still
* stuff in the corresponding output buffer
*/
if (nfrontp - nbackp)
obits |= (1 << f);
else
ibits |= (1 << p);
if (pfrontp - pbackp)
obits |= (1 << p);
else
ibits |= (1 << f);
if (ncc < 0 && pcc < 0)
break;
select(16, &ibits, &obits, 0, 0);
if (ibits == 0 && obits == 0) {
sleep(5);
continue;
}
/*
* Something to read from the network...
*/
if (ibits & (1 << f)) {
ncc = read(f, netibuf, BUFSIZ);
if (ncc < 0 && errno == EWOULDBLOCK)
ncc = 0;
else {
if (ncc <= 0)
break;
netip = netibuf;
}
}
/*
* Something to read from the pty...
*/
if (ibits & (1 << p)) {
pcc = read(p, ptyibuf, BUFSIZ);
if (pcc < 0 && errno == EWOULDBLOCK)
pcc = 0;
else {
if (pcc <= 0)
break;
ptyip = ptyibuf;
}
}
while (pcc > 0) {
if ((&netobuf[BUFSIZ] - nfrontp) < 2)
break;
c = *ptyip++ & 0377, pcc--;
if (c == IAC)
*nfrontp++ = c;
*nfrontp++ = c;
}
if ((obits & (1 << f)) && (nfrontp - nbackp) > 0)
netflush();
if (ncc > 0)
telrcv();
if ((obits & (1 << p)) && (pfrontp - pbackp) > 0)
ptyflush();
}
cleanup();
}
/*
* State for recv fsm
*/
#define TS_DATA 0 /* base state */
#define TS_IAC 1 /* look for double IAC's */
#define TS_CR 2 /* CR-LF ->'s CR */
#define TS_BEGINNEG 3 /* throw away begin's... */
#define TS_ENDNEG 4 /* ...end's (suboption negotiation) */
#define TS_WILL 5 /* will option negotiation */
#define TS_WONT 6 /* wont " */
#define TS_DO 7 /* do " */
#define TS_DONT 8 /* dont " */
telrcv()
{
register int c;
static int state = TS_DATA;
struct sgttyb b;
while (ncc > 0) {
if ((&ptyobuf[BUFSIZ] - pfrontp) < 2)
return;
c = *netip++ & 0377, ncc--;
switch (state) {
case TS_DATA:
if (c == IAC) {
state = TS_IAC;
break;
}
if (inter > 0)
break;
*pfrontp++ = c;
if (!myopts[TELOPT_BINARY] && c == '\r')
state = TS_CR;
break;
case TS_CR:
if (c && c != '\n')
*pfrontp++ = c;
state = TS_DATA;
break;
case TS_IAC:
switch (c) {
/*
* Send the process on the pty side an
* interrupt. Do this with a NULL or
* interrupt char; depending on the tty mode.
*/
case BREAK:
case IP:
interrupt();
break;
/*
* Are You There?
*/
case AYT:
*pfrontp++ = BELL;
break;
/*
* Erase Character and
* Erase Line
*/
case EC:
case EL:
ptyflush(); /* half-hearted */
ioctl(pty, TIOCGETP, &b);
*pfrontp++ = (c == EC) ?
b.sg_erase : b.sg_kill;
break;
/*
* Check for urgent data...
*/
case DM:
break;
/*
* Begin option subnegotiation...
*/
case SB:
state = TS_BEGINNEG;
continue;
case WILL:
case WONT:
case DO:
case DONT:
state = TS_WILL + (c - WILL);
continue;
case IAC:
*pfrontp++ = c;
break;
}
state = TS_DATA;
break;
case TS_BEGINNEG:
if (c == IAC)
state = TS_ENDNEG;
break;
case TS_ENDNEG:
state = c == SE ? TS_DATA : TS_BEGINNEG;
break;
case TS_WILL:
if (!hisopts[c])
willoption(c);
state = TS_DATA;
continue;
case TS_WONT:
if (hisopts[c])
wontoption(c);
state = TS_DATA;
continue;
case TS_DO:
if (!myopts[c])
dooption(c);
state = TS_DATA;
continue;
case TS_DONT:
if (myopts[c]) {
myopts[c] = 0;
sprintf(nfrontp, wont, c);
nfrontp += sizeof (wont) - 2;
}
state = TS_DATA;
continue;
default:
printf("telnetd: panic state=%d\n", state);
exit(1);
}
}
}
willoption(option)
int option;
{
char *fmt;
switch (option) {
case TELOPT_BINARY:
mode(RAW, 0);
goto common;
case TELOPT_ECHO:
mode(0, ECHO|CRMOD);
/*FALL THRU*/
case TELOPT_SGA:
common:
hisopts[option] = 1;
fmt = doopt;
break;
case TELOPT_TM:
fmt = dont;
break;
default:
fmt = dont;
break;
}
sprintf(nfrontp, fmt, option);
nfrontp += sizeof (dont) - 2;
}
wontoption(option)
int option;
{
char *fmt;
switch (option) {
case TELOPT_ECHO:
mode(ECHO|CRMOD, 0);
goto common;
case TELOPT_BINARY:
mode(0, RAW);
/*FALL THRU*/
case TELOPT_SGA:
common:
hisopts[option] = 0;
fmt = dont;
break;
default:
fmt = dont;
}
sprintf(nfrontp, fmt, option);
nfrontp += sizeof (doopt) - 2;
}
dooption(option)
int option;
{
char *fmt;
switch (option) {
case TELOPT_TM:
fmt = wont;
break;
case TELOPT_ECHO:
mode(ECHO|CRMOD, 0);
goto common;
case TELOPT_BINARY:
mode(RAW, 0);
/*FALL THRU*/
case TELOPT_SGA:
common:
fmt = will;
break;
default:
fmt = wont;
break;
}
sprintf(nfrontp, fmt, option);
nfrontp += sizeof (doopt) - 2;
}
mode(on, off)
int on, off;
{
struct sgttyb b;
ptyflush();
ioctl(pty, TIOCGETP, &b);
b.sg_flags |= on;
b.sg_flags &= ~off;
ioctl(pty, TIOCSETP, &b);
}
/*
* Send interrupt to process on other side of pty.
* If it is in raw mode, just write NULL;
* otherwise, write intr char.
*/
interrupt()
{
struct sgttyb b;
struct tchars tchars;
ptyflush(); /* half-hearted */
ioctl(pty, TIOCGETP, &b);
if (b.sg_flags & RAW) {
*pfrontp++ = '\0';
return;
}
*pfrontp++ = ioctl(pty, TIOCGETC, &tchars) < 0 ?
'\177' : tchars.t_intrc;
}
ptyflush()
{
int n;
if ((n = pfrontp - pbackp) > 0)
n = write(pty, pbackp, n);
if (n < 0)
return;
pbackp += n;
if (pbackp == pfrontp)
pbackp = pfrontp = ptyobuf;
}
netflush()
{
int n;
if ((n = nfrontp - nbackp) > 0)
n = write(net, nbackp, n);
if (n < 0) {
if (errno == EWOULDBLOCK)
return;
/* should blow this guy away... */
return;
}
nbackp += n;
if (nbackp == nfrontp)
nbackp = nfrontp = netobuf;
}
cleanup()
{
rmut();
vhangup(); /* XXX */
shutdown(net, 2);
kill(0, SIGKILL);
exit(1);
}
#include <utmp.h>
struct utmp wtmp;
char wtmpf[] = "/usr/adm/wtmp";
char utmp[] = "/etc/utmp";
#define SCPYN(a, b) strncpy(a, b, sizeof (a))
#define SCMPN(a, b) strncmp(a, b, sizeof (a))
rmut()
{
register f;
int found = 0;
f = open(utmp, 2);
if (f >= 0) {
while(read(f, (char *)&wtmp, sizeof (wtmp)) == sizeof (wtmp)) {
if (SCMPN(wtmp.ut_line, line+5) || wtmp.ut_name[0]==0)
continue;
lseek(f, -(long)sizeof (wtmp), 1);
SCPYN(wtmp.ut_name, "");
SCPYN(wtmp.ut_host, "");
time(&wtmp.ut_time);
write(f, (char *)&wtmp, sizeof (wtmp));
found++;
}
close(f);
}
if (found) {
f = open(wtmpf, 1);
if (f >= 0) {
SCPYN(wtmp.ut_line, line+5);
SCPYN(wtmp.ut_name, "");
SCPYN(wtmp.ut_host, "");
time(&wtmp.ut_time);
lseek(f, (long)0, 2);
write(f, (char *)&wtmp, sizeof (wtmp));
close(f);
}
}
chmod(line, 0666);
chown(line, 0, 0);
line[strlen("/dev/")] = 'p';
chmod(line, 0666);
chown(line, 0, 0);
}
/*
* Convert network-format internet address
* to base 256 d.d.d.d representation.
*/
char *
ntoa(in)
struct in_addr in;
{
static char b[18];
register char *p;
p = (char *)∈
#define UC(b) (((int)b)&0xff)
sprintf(b, "%d.%d.%d.%d", UC(p[0]), UC(p[1]), UC(p[2]), UC(p[3]));
return (b);
}