xref: /csrg-svn/libexec/rlogind/rlogind.c (revision 42264)

/*
 * Copyright (c) 1983, 1988, 1989 The Regents of the University of California.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms are permitted
 * provided that the above copyright notice and this paragraph are
 * duplicated in all such forms and that any documentation,
 * advertising materials, and other materials related to such
 * distribution and use acknowledge that the software was developed
 * by the University of California, Berkeley.  The name of the
 * University may not be used to endorse or promote products derived
 * from this software without specific prior written permission.
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
 * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 */

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

#ifndef lint
static char sccsid[] = "@(#)rlogind.c	5.43 (Berkeley) 05/21/90";
#endif /* not lint */

#ifdef KERBEROS
/* From:
 *	$Source: /mit/kerberos/ucb/mit/rlogind/RCS/rlogind.c,v $
 *	$Header: rlogind.c,v 5.0 89/06/26 18:31:01 kfall Locked $
 */
#endif

/*
 * 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/param.h>
#include <sys/stat.h>
#include <sys/socket.h>
#include <sys/wait.h>
#include <sys/file.h>
#include <sys/signal.h>
#include <sys/ioctl.h>
#include <sys/termios.h>

#include <netinet/in.h>

#include <errno.h>
#include <pwd.h>
#include <netdb.h>
#include <syslog.h>
#include <string.h>
#include <stdio.h>
#include <unistd.h>
#include "pathnames.h"

#ifndef TIOCPKT_WINDOW
#define TIOCPKT_WINDOW 0x80
#endif

#ifdef	KERBEROS
#include <kerberosIV/des.h>
#include <kerberosIV/krb.h>
#define	SECURE_MESSAGE "This rlogin session is using DES encryption for all transmissions.\r\n"

AUTH_DAT	*kdata;
KTEXT		ticket;
u_char		auth_buf[sizeof(AUTH_DAT)];
u_char		tick_buf[sizeof(KTEXT_ST)];
Key_schedule	schedule;
int		encrypt = 0, retval, use_kerberos = 0, vacuous = 0;

#define		ARGSTR			"alnkvx"
#else
#define		ARGSTR			"aln"
#endif	/* KERBEROS */

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;

extern	int errno;
int	reapchild();
struct	passwd *getpwnam(), *pwd;
char	*malloc();

main(argc, argv)
	int argc;
	char **argv;
{
	extern int opterr, optind;
	extern int _check_rhosts_file;
	int ch;
	int on = 1, fromlen;
	struct sockaddr_in from;

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

	opterr = 0;
	while ((ch = getopt(argc, argv, ARGSTR)) != EOF)
		switch (ch) {
		case 'a':
			check_all = 1;
			break;
		case 'l':
			_check_rhosts_file = 0;
			break;
		case 'n':
			keepalive = 0;
			break;
#ifdef KERBEROS
		case 'k':
			use_kerberos = 1;
			break;
		case 'v':
			vacuous = 1;
			break;
		case 'x':
			encrypt = 1;
			break;
#endif
		case '?':
		default:
			usage();
			break;
		}
	argc -= optind;
	argv += optind;

#ifdef	KERBEROS
	if (use_kerberos && vacuous) {
		usage();
		fatal(STDERR_FILENO, "only one of -k and -v allowed", 0);
	}
#endif
	fromlen = sizeof (from);
	if (getpeername(0, &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);
	}
	if (keepalive &&
	    setsockopt(0, SOL_SOCKET, SO_KEEPALIVE, &on, sizeof (on)) < 0)
		syslog(LOG_WARNING, "setsockopt (SO_KEEPALIVE): %m");
	doit(0, &from);
}

int	child;
int	cleanup();
int	netf;
char	*line;
int	confirmed;
extern	char	*inet_ntoa();

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


doit(f, fromp)
	int f;
	struct sockaddr_in *fromp;
{
	int i, p, t, pid, on = 1;
	int authenticated = 0, hostok = 0;
	register struct hostent *hp;
	char remotehost[2 * MAXHOSTNAMELEN + 1];
	struct hostent hostent;
	char c;

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

	if (c != 0)
		exit(1);
#ifdef	KERBEROS
	if (vacuous)
		fatal(f, "Remote host requires Kerberos authentication", 0);
#endif

	alarm(0);
	fromp->sin_port = ntohs((u_short)fromp->sin_port);
	hp = gethostbyaddr(&fromp->sin_addr, sizeof (struct in_addr),
		fromp->sin_family);
	if (hp == 0) {
		/*
		 * Only the name is used below.
		 */
		hp = &hostent;
		hp->h_name = inet_ntoa(fromp->sin_addr);
		hostok++;
	} else if (check_all || local_domain(hp->h_name)) {
		/*
		 * If name returned by gethostbyaddr is in our domain,
		 * attempt to verify that we haven't been fooled by someone
		 * in a remote net; look up the name and check that this
		 * address corresponds to the name.
		 */
		strncpy(remotehost, hp->h_name, sizeof(remotehost) - 1);
		remotehost[sizeof(remotehost) - 1] = 0;
		hp = gethostbyname(remotehost);
		if (hp)
		    for (; hp->h_addr_list[0]; hp->h_addr_list++)
			if (!bcmp(hp->h_addr_list[0], (caddr_t)&fromp->sin_addr,
			    sizeof(fromp->sin_addr))) {
				hostok++;
				break;
			}
	} else
		hostok++;

#ifdef	KERBEROS
	if (use_kerberos) {
		if (!hostok)
			fatal(f, "krlogind: Host address mismatch.", 0);
		retval = do_krb_login(hp->h_name, fromp, encrypt);
		if (retval == 0)
			authenticated++;
		else if (retval > 0)
			fatal(f, krb_err_txt[retval], 0);
		write(f, &c, 1);
		confirmed = 1;		/* we sent the null! */
	} else
#endif
	{
	    if (fromp->sin_family != AF_INET ||
	        fromp->sin_port >= IPPORT_RESERVED ||
	        fromp->sin_port < IPPORT_RESERVED/2) {
		    syslog(LOG_NOTICE, "Connection from %s on illegal port",
			    inet_ntoa(fromp->sin_addr));
		    fatal(f, "Permission denied", 0);
	    }
#ifdef IP_OPTIONS
	    {
	    u_char optbuf[BUFSIZ/3], *cp;
	    char lbuf[BUFSIZ], *lp;
	    int optsize = sizeof(optbuf), ipproto;
	    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) {
		    lp = lbuf;
		    for (cp = optbuf; optsize > 0; cp++, optsize--, lp += 3)
			    sprintf(lp, " %2.2x", *cp);
		    syslog(LOG_NOTICE,
			"Connection received using IP options (ignored):%s",
			lbuf);
		    if (setsockopt(0, ipproto, IP_OPTIONS,
			(char *)NULL, &optsize) != 0) {
			    syslog(LOG_ERR, "setsockopt IP_OPTIONS NULL: %m");
			    exit(1);
		    }
	        }
	    }
#endif
	    if (do_rlogin(hp->h_name) == 0 && hostok)
		    authenticated++;
	}

	for (c = 'p'; c <= 's'; c++) {
		struct stat stb;
		line = "/dev/ptyXX";
		line[strlen("/dev/pty")] = c;
		line[strlen("/dev/ptyp")] = '0';
		if (stat(line, &stb) < 0)
			break;
		for (i = 0; i < 16; i++) {
			line[sizeof("/dev/ptyp") - 1] = "0123456789abcdef"[i];
			p = open(line, O_RDWR);
			if (p > 0)
				goto gotpty;
		}
	}
	fatal(f, "Out of ptys", 0);
	/*NOTREACHED*/
gotpty:
	(void) ioctl(p, TIOCSWINSZ, &win);
	netf = f;
	line[sizeof(_PATH_DEV) - 1] = 't';
	t = open(line, O_RDWR);
	if (t < 0)
		fatal(f, line, 1);
	if (fchmod(t, 0))
		fatal(f, line, 1);
	(void)signal(SIGHUP, SIG_IGN);
	vhangup();
	(void)signal(SIGHUP, SIG_DFL);
	t = open(line, O_RDWR);
	if (t < 0)
		fatal(f, line, 1);
	setup_term(t);
	if (confirmed == 0) {
		write(f, "", 1);
		confirmed = 1;		/* we sent the null! */
	}
#ifdef	KERBEROS
	if (encrypt)
		(void) des_write(f, SECURE_MESSAGE, sizeof(SECURE_MESSAGE));

	if (use_kerberos == 0)
#endif
	   if (!authenticated && !hostok)
		write(f, "rlogind: Host address mismatch.\r\n",
		    sizeof("rlogind: Host address mismatch.\r\n") - 1);

	pid = fork();
	if (pid < 0)
		fatal(f, "", 1);
	if (pid == 0) {
		if (setsid() < 0)
			fatal(f, "setsid", 1);
		if (ioctl(t, TIOCSCTTY, 0) < 0)
			fatal(f, "ioctl(sctty)", 1);
		(void)close(f);
		(void)close(p);
		dup2(t, STDIN_FILENO);
		dup2(t, STDOUT_FILENO);
		dup2(t, STDERR_FILENO);
		(void)close(t);

		if (authenticated)
			execl(_PATH_LOGIN, "login", "-p",
			    "-h", hp->h_name, "-f", lusername, 0);
		else
			execl(_PATH_LOGIN, "login", "-p",
			    "-h", hp->h_name, lusername, 0);
		fatal(STDERR_FILENO, _PATH_LOGIN, 1);
		/*NOTREACHED*/
	}
	close(t);

#ifdef	KERBEROS
	/*
	 * If encrypted, don't turn on NBIO or the des read/write
	 * routines will croak.
	 */

	if (!encrypt)
#endif
		ioctl(f, FIONBIO, &on);
	ioctl(p, FIONBIO, &on);
	ioctl(p, TIOCPKT, &on);
	signal(SIGCHLD, cleanup);
	protocol(f, p);
	signal(SIGCHLD, SIG_IGN);
	cleanup();
}

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.
 */
control(pty, cp, n)
	int pty;
	char *cp;
	int n;
{
	struct winsize w;

	if (n < 4+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.
 */
protocol(f, p)
	register int f, p;
{
	char pibuf[1024+1], fibuf[1024], *pbp, *fbp;
	register 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(&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)) {
#ifdef KERBEROS
			if (encrypt)
				fcc = des_read(f, fibuf, sizeof(fibuf));
			else
#endif
				fcc = read(f, fibuf, sizeof(fibuf));
			if (fcc < 0 && errno == EWOULDBLOCK)
				fcc = 0;
			else {
				register 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--;
#ifdef KERBEROS
				if (!encrypt)
#endif
					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) {
#ifdef KERBEROS
			if (encrypt)
				cc = des_write(f, pbp, pcc);
			else
#endif
				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;
			}
		}
	}
}

cleanup()
{
	char *p;

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

fatal(f, msg, syserr)
	int f, syserr;
	char *msg;
{
	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 = sprintf(bp, "rlogind: %s: %s.\r\n",
		    msg, strerror(errno));
	else
		len = sprintf(bp, "rlogind: %s.\r\n", msg);
	(void) write(f, buf, bp + len - buf);
	exit(1);
}

do_rlogin(host)
	char *host;
{
	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);
	if (pwd->pw_uid == 0)
		return(-1);
	return(ruserok(host, 0, rusername, lusername));
}


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

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

extern	char **environ;

setup_term(fd)
	int fd;
{
	register 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, TCSADFLUSH, &tt);
#else
	if (cp) {
		*cp++ = '\0';
		speed = cp;
		cp = index(speed, '/');
		if (cp)
			*cp++ = '\0';
		tcgetattr(fd, &tt);
		cfsetspeed(&tt, atoi(speed));
		tcsetattr(fd, TCSADFLUSH, &tt);
	}
#endif

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

#ifdef	KERBEROS
#define	VERSION_SIZE	9

/*
 * Do the remote kerberos login to the named host with the
 * given inet address
 *
 * Return 0 on valid authorization
 * Return -1 on valid authentication, no authorization
 * Return >0 for error conditions
 */
do_krb_login(host, dest, encrypt)
	char *host;
	struct sockaddr_in *dest;
	int encrypt;
{
	int rc;
	char instance[INST_SZ], version[VERSION_SIZE];
	long authopts = 0L;	/* !mutual */
	struct sockaddr_in faddr;

	kdata = (AUTH_DAT *) auth_buf;
	ticket = (KTEXT) tick_buf;

	instance[0] = '*';
	instance[1] = '\0';

	if (encrypt) {
		rc = sizeof(faddr);
		if (getsockname(0, &faddr, &rc))
			return(-1);
		authopts = KOPT_DO_MUTUAL;
		rc = krb_recvauth(
			authopts, 0,
			ticket, "rcmd",
			instance, dest, &faddr,
			kdata, "", schedule, version);
		 des_set_key(kdata->session, schedule);

	} else {
		rc = krb_recvauth(
			authopts, 0,
			ticket, "rcmd",
			instance, dest, (struct sockaddr_in *) 0,
			kdata, "", (bit_64 *) 0, version);
	}

	if (rc != KSUCCESS)
		return(rc);

	getstr(lusername, sizeof(lusername), "locuser");
	/* get the "cmd" in the rcmd protocol */
	getstr(term+ENVSIZE, sizeof(term)-ENVSIZE, "Terminal type");

	pwd = getpwnam(lusername);
	if (pwd == NULL)
		return(-1);

	/* returns nonzero for no access */
	if (kuserok(kdata,lusername) != 0)
		return(-1);

	return(0);

}
#endif /* KERBEROS */

usage()
{
#ifdef KERBEROS
	syslog(LOG_ERR, "usage: rlogind [-aln] [-k | -v]");
#else
	syslog(LOG_ERR, "usage: rlogind [-aln]");
#endif
}

/*
 * Check whether host h is in our local domain,
 * defined as sharing the last two components of the domain part,
 * or the entire domain part if the local domain has only one component.
 * If either name is unqualified (contains no '.'),
 * assume that the host is local, as it will be
 * interpreted as such.
 */
local_domain(h)
	char *h;
{
	char localhost[MAXHOSTNAMELEN];
	char *p1, *p2, *topdomain();

	localhost[0] = 0;
	(void) gethostname(localhost, sizeof(localhost));
	p1 = topdomain(localhost);
	p2 = topdomain(h);
	if (p1 == NULL || p2 == NULL || !strcasecmp(p1, p2))
		return(1);
	return(0);
}

char *
topdomain(h)
	char *h;
{
	register char *p;
	char *maybe = NULL;
	int dots = 0;

	for (p = h + strlen(h); p >= h; p--) {
		if (*p == '.') {
			if (++dots == 2)
				return (p);
			maybe = p;
		}
	}
	return (maybe);
}