xref: /freebsd-11-stable/libexec/rlogind/rlogind.c

/*-
 * Copyright (c) 1983, 1988, 1989, 1993
 *	The Regents of the University of California.  All rights reserved.
 * Copyright (c) 2002 Networks Associates Technology, Inc.
 * All rights reserved.
 *
 * Portions of this software were developed for the FreeBSD Project by
 * ThinkSec AS and NAI Labs, the Security Research Division of Network
 * Associates, Inc.  under DARPA/SPAWAR contract N66001-01-C-8035
 * ("CBOSS"), as part of the DARPA CHATS research program.
 *
 * 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. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``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 REGENTS OR CONTRIBUTORS 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.
 */

#if 0
#ifndef lint
static const char copyright[] =
"@(#) Copyright (c) 1983, 1988, 1989, 1993\n\
	The Regents of the University of California.  All rights reserved.\n";
#endif /* not lint */

#ifndef lint
static const char sccsid[] = "@(#)rlogind.c	8.1 (Berkeley) 6/4/93";
#endif /* not lint */
#endif
#include <sys/cdefs.h>
__FBSDID("$FreeBSD: head/libexec/rlogind/rlogind.c 141918 2005-02-14 17:42:58Z stefanf $");

/*
 * remote login server:
 *	\0
 *	remuser\0
 *	locuser\0
 *	terminal_type/speed\0
 *	data
 */

#define	FD_SETSIZE	16		/* don't need many bits for select */
#include <sys/types.h>
#include <sys/param.h>
#include <sys/stat.h>
#include <sys/ioctl.h>
#include <signal.h>
#include <termios.h>

#include <sys/socket.h>
#include <netinet/in.h>
#include <netinet/in_systm.h>
#include <netinet/ip.h>
#include <netinet/tcp.h>
#include <arpa/inet.h>
#include <netdb.h>

#include <errno.h>
#include <libutil.h>
#include <paths.h>
#include <pwd.h>
#include <syslog.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>


#ifndef TIOCPKT_WINDOW
#define TIOCPKT_WINDOW 0x80
#endif

#define		ARGSTR			"Daln"

/* wrapper for KAME-special getnameinfo() */
#ifndef NI_WITHSCOPEID
#define	NI_WITHSCOPEID	0
#endif

char	*env[2];
#define	NMAX 30
char	lusername[NMAX+1], rusername[NMAX+1];
static	char term[64] = "TERM=";
#define	ENVSIZE	(sizeof("TERM=")-1)	/* skip null for concatenation */
int	keepalive = 1;
int	check_all = 0;
int	no_delay;

struct	passwd *pwd;

union sockunion {
	struct sockinet {
		u_char si_len;
		u_char si_family;
		u_short si_port;
	} su_si;
	struct sockaddr_in  su_sin;
	struct sockaddr_in6 su_sin6;
};
#define su_len		su_si.si_len
#define su_family	su_si.si_family
#define su_port		su_si.si_port

void	doit(int, union sockunion *);
int	control(int, char *, int);
void	protocol(int, int);
void	cleanup(int);
void	fatal(int, char *, int);
int	do_rlogin(union sockunion *);
void	getstr(char *, int, char *);
void	setup_term(int);
int	do_krb_login(struct sockaddr_in *);
void	usage(void);


int
main(int argc, char *argv[])
{
	extern int __check_rhosts_file;
	union sockunion from;
	socklen_t fromlen;
	int ch, on;

	openlog("rlogind", LOG_PID | LOG_CONS, LOG_AUTH);

	opterr = 0;
	while ((ch = getopt(argc, argv, ARGSTR)) != -1)
		switch (ch) {
		case 'D':
			no_delay = 1;
			break;
		case 'a':
			check_all = 1;
			break;
		case 'l':
			__check_rhosts_file = 0;
			break;
		case 'n':
			keepalive = 0;
			break;
		case '?':
		default:
			usage();
			break;
		}
	argc -= optind;
	argv += optind;

	fromlen = sizeof (from);
	if (getpeername(0, (struct sockaddr *)&from, &fromlen) < 0) {
		syslog(LOG_ERR,"Can't get peer name of remote host: %m");
		fatal(STDERR_FILENO, "Can't get peer name of remote host", 1);
	}
	on = 1;
	if (keepalive &&
	    setsockopt(0, SOL_SOCKET, SO_KEEPALIVE, &on, sizeof (on)) < 0)
		syslog(LOG_WARNING, "setsockopt (SO_KEEPALIVE): %m");
	if (no_delay &&
	    setsockopt(0, IPPROTO_TCP, TCP_NODELAY, &on, sizeof(on)) < 0)
		syslog(LOG_WARNING, "setsockopt (TCP_NODELAY): %m");
	if (from.su_family == AF_INET)
      {
	on = IPTOS_LOWDELAY;
	if (setsockopt(0, IPPROTO_IP, IP_TOS, (char *)&on, sizeof(int)) < 0)
		syslog(LOG_WARNING, "setsockopt (IP_TOS): %m");
      }

	doit(0, &from);
	return 0;
}

int	child;
int	netf;
char	line[MAXPATHLEN];
int	confirmed;

struct winsize win = { 0, 0, 0, 0 };


void
doit(int f, union sockunion *fromp)
{
	int master, pid, on = 1;
	int authenticated = 0;
	char hostname[2 * MAXHOSTNAMELEN + 1];
	char nameinfo[2 * INET6_ADDRSTRLEN + 1];
	char c;

	alarm(60);
	read(f, &c, 1);

	if (c != 0)
		exit(1);

	alarm(0);

	realhostname_sa(hostname, sizeof(hostname) - 1,
			    (struct sockaddr *)fromp, fromp->su_len);
	/* error check ? */
	fromp->su_port = ntohs((u_short)fromp->su_port);
	hostname[sizeof(hostname) - 1] = '\0';

	{
		if ((fromp->su_family != AF_INET
#ifdef INET6
		  && fromp->su_family != AF_INET6
#endif
		     ) ||
		    fromp->su_port >= IPPORT_RESERVED ||
		    fromp->su_port < IPPORT_RESERVED/2) {
			getnameinfo((struct sockaddr *)fromp,
				    fromp->su_len,
				    nameinfo, sizeof(nameinfo), NULL, 0,
				    NI_NUMERICHOST|NI_WITHSCOPEID);
			/* error check ? */
			syslog(LOG_NOTICE, "Connection from %s on illegal port",
			       nameinfo);
			fatal(f, "Permission denied", 0);
		}
#ifdef IP_OPTIONS
		if (fromp->su_family == AF_INET)
	      {
		u_char optbuf[BUFSIZ/3];
		socklen_t optsize = sizeof(optbuf);
		int ipproto, i;
		struct protoent *ip;

		if ((ip = getprotobyname("ip")) != NULL)
			ipproto = ip->p_proto;
		else
			ipproto = IPPROTO_IP;
		if (getsockopt(0, ipproto, IP_OPTIONS, (char *)optbuf,
		    &optsize) == 0 && optsize != 0) {
			for (i = 0; i < optsize; ) {
				u_char c = optbuf[i];
				if (c == IPOPT_LSRR || c == IPOPT_SSRR) {
					syslog(LOG_NOTICE,
						"Connection refused from %s with IP option %s",
						inet_ntoa(fromp->su_sin.sin_addr),
						c == IPOPT_LSRR ? "LSRR" : "SSRR");
					exit(1);
				}
				if (c == IPOPT_EOL)
					break;
				i += (c == IPOPT_NOP) ? 1 : optbuf[i+1];
			}
		}
	      }
#endif
		if (do_rlogin(fromp) == 0)
			authenticated++;
	}
	if (confirmed == 0) {
		write(f, "", 1);
		confirmed = 1;		/* we sent the null! */
	}
	netf = f;

	pid = forkpty(&master, line, NULL, &win);
	if (pid < 0) {
		if (errno == ENOENT)
			fatal(f, "Out of ptys", 0);
		else
			fatal(f, "Forkpty", 1);
	}
	if (pid == 0) {
		if (f > 2)	/* f should always be 0, but... */
			(void) close(f);
		setup_term(0);
		 if (*lusername=='-') {
			syslog(LOG_ERR, "tried to pass user \"%s\" to login",
			       lusername);
			fatal(STDERR_FILENO, "invalid user", 0);
		}
		if (authenticated) {
			execl(_PATH_LOGIN, "login", "-p",
			    "-h", hostname, "-f", lusername, (char *)NULL);
		} else
			execl(_PATH_LOGIN, "login", "-p",
			    "-h", hostname, lusername, (char *)NULL);
		fatal(STDERR_FILENO, _PATH_LOGIN, 1);
		/*NOTREACHED*/
	}
	ioctl(f, FIONBIO, &on);
	ioctl(master, FIONBIO, &on);
	ioctl(master, TIOCPKT, &on);
	signal(SIGCHLD, cleanup);
	protocol(f, master);
	signal(SIGCHLD, SIG_IGN);
	cleanup(0);
}

char	magic[2] = { 0377, 0377 };
char	oobdata[] = {TIOCPKT_WINDOW};

/*
 * Handle a "control" request (signaled by magic being present)
 * in the data stream.  For now, we are only willing to handle
 * window size changes.
 */
int
control(int pty, char *cp, int n)
{
	struct winsize w;

	if (n < 4 + (int)sizeof(w) || cp[2] != 's' || cp[3] != 's')
		return (0);
	oobdata[0] &= ~TIOCPKT_WINDOW;	/* we know he heard */
	bcopy(cp+4, (char *)&w, sizeof(w));
	w.ws_row = ntohs(w.ws_row);
	w.ws_col = ntohs(w.ws_col);
	w.ws_xpixel = ntohs(w.ws_xpixel);
	w.ws_ypixel = ntohs(w.ws_ypixel);
	(void)ioctl(pty, TIOCSWINSZ, &w);
	return (4+sizeof (w));
}

/*
 * rlogin "protocol" machine.
 */
void
protocol(int f, int p)
{
	char pibuf[1024+1], fibuf[1024], *pbp = NULL, *fbp = NULL;
	int pcc = 0, fcc = 0;
	int cc, nfd, n;
	char cntl;

	/*
	 * Must ignore SIGTTOU, otherwise we'll stop
	 * when we try and set slave pty's window shape
	 * (our controlling tty is the master pty).
	 */
	(void) signal(SIGTTOU, SIG_IGN);
	send(f, oobdata, 1, MSG_OOB);	/* indicate new rlogin */
	if (f > p)
		nfd = f + 1;
	else
		nfd = p + 1;
	if (nfd > FD_SETSIZE) {
		syslog(LOG_ERR, "select mask too small, increase FD_SETSIZE");
		fatal(f, "internal error (select mask too small)", 0);
	}
	for (;;) {
		fd_set ibits, obits, ebits, *omask;

		FD_ZERO(&ebits);
		FD_ZERO(&ibits);
		FD_ZERO(&obits);
		omask = (fd_set *)NULL;
		if (fcc) {
			FD_SET(p, &obits);
			omask = &obits;
		} else
			FD_SET(f, &ibits);
		if (pcc >= 0) {
			if (pcc) {
				FD_SET(f, &obits);
				omask = &obits;
			} else
				FD_SET(p, &ibits);
		}
		FD_SET(p, &ebits);
		if ((n = select(nfd, &ibits, omask, &ebits, 0)) < 0) {
			if (errno == EINTR)
				continue;
			fatal(f, "select", 1);
		}
		if (n == 0) {
			/* shouldn't happen... */
			sleep(5);
			continue;
		}
#define	pkcontrol(c)	((c)&(TIOCPKT_FLUSHWRITE|TIOCPKT_NOSTOP|TIOCPKT_DOSTOP))
		if (FD_ISSET(p, &ebits)) {
			cc = read(p, &cntl, 1);
			if (cc == 1 && pkcontrol(cntl)) {
				cntl |= oobdata[0];
				send(f, &cntl, 1, MSG_OOB);
				if (cntl & TIOCPKT_FLUSHWRITE) {
					pcc = 0;
					FD_CLR(p, &ibits);
				}
			}
		}
		if (FD_ISSET(f, &ibits)) {
			fcc = read(f, fibuf, sizeof(fibuf));
			if (fcc < 0 && errno == EWOULDBLOCK)
				fcc = 0;
			else {
				char *cp;
				int left, n;

				if (fcc <= 0)
					break;
				fbp = fibuf;

			top:
				for (cp = fibuf; cp < fibuf+fcc-1; cp++)
					if (cp[0] == magic[0] &&
					    cp[1] == magic[1]) {
						left = fcc - (cp-fibuf);
						n = control(p, cp, left);
						if (n) {
							left -= n;
							if (left > 0)
								bcopy(cp+n, cp, left);
							fcc -= n;
							goto top; /* n^2 */
						}
					}
				FD_SET(p, &obits);		/* try write */
			}
		}

		if (FD_ISSET(p, &obits) && fcc > 0) {
			cc = write(p, fbp, fcc);
			if (cc > 0) {
				fcc -= cc;
				fbp += cc;
			}
		}

		if (FD_ISSET(p, &ibits)) {
			pcc = read(p, pibuf, sizeof (pibuf));
			pbp = pibuf;
			if (pcc < 0 && errno == EWOULDBLOCK)
				pcc = 0;
			else if (pcc <= 0)
				break;
			else if (pibuf[0] == 0) {
				pbp++, pcc--;
				FD_SET(f, &obits);	/* try write */
			} else {
				if (pkcontrol(pibuf[0])) {
					pibuf[0] |= oobdata[0];
					send(f, &pibuf[0], 1, MSG_OOB);
				}
				pcc = 0;
			}
		}
		if ((FD_ISSET(f, &obits)) && pcc > 0) {
			cc = write(f, pbp, pcc);
			if (cc < 0 && errno == EWOULDBLOCK) {
				/*
				 * This happens when we try write after read
				 * from p, but some old kernels balk at large
				 * writes even when select returns true.
				 */
				if (!FD_ISSET(p, &ibits))
					sleep(5);
				continue;
			}
			if (cc > 0) {
				pcc -= cc;
				pbp += cc;
			}
		}
	}
}

void
cleanup(int signo)
{
	char *p;

	p = line + sizeof(_PATH_DEV) - 1;
	if (logout(p))
		logwtmp(p, "", "");
	(void)chflags(line, 0);
	(void)chmod(line, 0666);
	(void)chown(line, 0, 0);
	*p = 'p';
	(void)chflags(line, 0);
	(void)chmod(line, 0666);
	(void)chown(line, 0, 0);
	shutdown(netf, 2);
	exit(1);
}

void
fatal(int f, char *msg, int syserr)
{
	int len;
	char buf[BUFSIZ], *bp = buf;

	/*
	 * Prepend binary one to message if we haven't sent
	 * the magic null as confirmation.
	 */
	if (!confirmed)
		*bp++ = '\01';		/* error indicator */
	if (syserr)
		len = snprintf(bp, sizeof(buf), "rlogind: %s: %s.\r\n",
		    msg, strerror(errno));
	else
		len = snprintf(bp, sizeof(buf), "rlogind: %s.\r\n", msg);
	if (len < 0)
		len = 0;
	(void) write(f, buf, bp + len - buf);
	exit(1);
}

int
do_rlogin(union sockunion *dest)
{

	getstr(rusername, sizeof(rusername), "remuser too long");
	getstr(lusername, sizeof(lusername), "locuser too long");
	getstr(term+ENVSIZE, sizeof(term)-ENVSIZE, "Terminal type too long");

	pwd = getpwnam(lusername);
	if (pwd == NULL)
		return (-1);
	/* XXX why don't we syslog() failure? */

	return (iruserok_sa(dest, dest->su_len, pwd->pw_uid == 0, rusername,
			    lusername));
}

void
getstr(char *buf, int cnt, char *errmsg)
{
	char c;

	do {
		if (read(STDIN_FILENO, &c, 1) != 1)
			exit(1);
		if (--cnt < 0)
			fatal(STDOUT_FILENO, errmsg, 0);
		*buf++ = c;
	} while (c != 0);
}

extern	char **environ;

void
setup_term(int fd)
{
	char *cp = index(term+ENVSIZE, '/');
	char *speed;
	struct termios tt;

#ifndef notyet
	tcgetattr(fd, &tt);
	if (cp) {
		*cp++ = '\0';
		speed = cp;
		cp = index(speed, '/');
		if (cp)
			*cp++ = '\0';
		cfsetspeed(&tt, atoi(speed));
	}

	tt.c_iflag = TTYDEF_IFLAG;
	tt.c_oflag = TTYDEF_OFLAG;
	tt.c_lflag = TTYDEF_LFLAG;
	tcsetattr(fd, TCSAFLUSH, &tt);
#else
	if (cp) {
		*cp++ = '\0';
		speed = cp;
		cp = index(speed, '/');
		if (cp)
			*cp++ = '\0';
		tcgetattr(fd, &tt);
		cfsetspeed(&tt, atoi(speed));
		tcsetattr(fd, TCSAFLUSH, &tt);
	}
#endif

	env[0] = term;
	env[1] = 0;
	environ = env;
}

void
usage(void)
{
	syslog(LOG_ERR, "usage: rlogind [-" ARGSTR "]");
}