usr/src/usr.sbin/sliplogin/sliplogin.c

/*-
 * Copyright (c) 1990, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * 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.
 */

#ifndef lint
static char copyright[] =
"@(#) Copyright (c) 1990, 1993\n\
        The Regents of the University of California.  All rights reserved.\n";
#endif /* not lint */

#ifndef lint
static char sccsid[] = "@(#)sliplogin.c 8.1 (Berkeley) 6/6/93";
#endif /* not lint */

/*
 * sliplogin.c
 * [MUST BE RUN SUID, SLOPEN DOES A SUSER()!]
 *
 * This program initializes its own tty port to be an async TCP/IP interface.
 * It sets the line discipline to slip, invokes a shell script to initialize
 * the network interface, then pauses forever waiting for hangup.
 *
 * It is a remote descendant of several similar programs with incestuous ties:
 * - Kirk Smith's slipconf, modified by Richard Johnsson @ DEC WRL.
 * - slattach, probably by Rick Adams but touched by countless hordes.
 * - the original sliplogin for 4.2bsd, Doug Kingston the mover behind it.
 *
 * There are two forms of usage:
 *
 * "sliplogin"
 * Invoked simply as "sliplogin", the program looks up the username
 * in the file /etc/slip.hosts.
 * If an entry is found, the line on fd0 is configured for SLIP operation
 * as specified in the file.
 *
 * "sliplogin IPhostlogin </dev/ttyb"
 * Invoked by root with a username, the name is looked up in the
 * /etc/slip.hosts file and if found fd0 is configured as in case 1.
 */

#include <sys/param.h>
#include <sys/socket.h>
#include <sys/signal.h>
#include <sys/file.h>
#include <sys/syslog.h>
#include <netdb.h>

#if BSD >= 199006
#define POSIX
#endif
#ifdef POSIX
#include <sys/termios.h>
#include <sys/ioctl.h>
#include <ttyent.h>
#else
#include <sgtty.h>
#endif
#include <netinet/in.h>
#include <net/if.h>
#include <net/if_slvar.h>

#include <stdio.h>
#include <errno.h>
#include <ctype.h>
#include <string.h>
#include "pathnames.h"

int     unit;
int     speed;
int     uid;
char    loginargs[BUFSIZ];
char    loginfile[MAXPATHLEN];
char    loginname[BUFSIZ];

void
findid(name)
        char *name;
{
        FILE *fp;
        static char slopt[5][16];
        static char laddr[16];
        static char raddr[16];
        static char mask[16];
        char user[16];
        int i, j, n;

        (void)strcpy(loginname, name);
        if ((fp = fopen(_PATH_ACCESS, "r")) == NULL) {
                (void)fprintf(stderr, "sliplogin: %s: %s\n",
                    _PATH_ACCESS, strerror(errno));
                syslog(LOG_ERR, "%s: %m\n", _PATH_ACCESS);
                exit(1);
        }
        while (fgets(loginargs, sizeof(loginargs) - 1, fp)) {
                if (ferror(fp))
                        break;
                n = sscanf(loginargs, "%15s%*[ \t]%15s%*[ \t]%15s%*[ \t]%15s%*[ \t]%15s%*[ \t]%15s%*[ \t]%15s%*[ \t]%15s%*[ \t]%15s\n",
                        user, laddr, raddr, mask, slopt[0], slopt[1],
                        slopt[2], slopt[3], slopt[4]);
                if (user[0] == '#' || isspace(user[0]))
                        continue;
                if (strcmp(user, name) != 0)
                        continue;

                /*
                 * we've found the guy we're looking for -- see if
                 * there's a login file we can use.  First check for
                 * one specific to this host.  If none found, try for
                 * a generic one.
                 */
                (void)sprintf(loginfile, "%s.%s", _PATH_LOGIN, name);
                if (access(loginfile, R_OK|X_OK) != 0) {
                        (void)strcpy(loginfile, _PATH_LOGIN);
                        if (access(loginfile, R_OK|X_OK)) {
                                fputs("access denied - no login file\n",
                                      stderr);
                                syslog(LOG_ERR,
                                       "access denied for %s - no %s\n",
                                       name, _PATH_LOGIN);
                                exit(5);
                        }
                }

                (void) fclose(fp);
                return;
        }
        (void)fprintf(stderr, "SLIP access denied for %s\n", name);
        syslog(LOG_ERR, "SLIP access denied for %s\n", name);
        exit(4);
        /* NOTREACHED */
}

char *
sigstr(s)
        int s;
{
        static char buf[32];

        switch (s) {
        case SIGHUP:    return("HUP");
        case SIGINT:    return("INT");
        case SIGQUIT:   return("QUIT");
        case SIGILL:    return("ILL");
        case SIGTRAP:   return("TRAP");
        case SIGIOT:    return("IOT");
        case SIGEMT:    return("EMT");
        case SIGFPE:    return("FPE");
        case SIGKILL:   return("KILL");
        case SIGBUS:    return("BUS");
        case SIGSEGV:   return("SEGV");
        case SIGSYS:    return("SYS");
        case SIGPIPE:   return("PIPE");
        case SIGALRM:   return("ALRM");
        case SIGTERM:   return("TERM");
        case SIGURG:    return("URG");
        case SIGSTOP:   return("STOP");
        case SIGTSTP:   return("TSTP");
        case SIGCONT:   return("CONT");
        case SIGCHLD:   return("CHLD");
        case SIGTTIN:   return("TTIN");
        case SIGTTOU:   return("TTOU");
        case SIGIO:     return("IO");
        case SIGXCPU:   return("XCPU");
        case SIGXFSZ:   return("XFSZ");
        case SIGVTALRM: return("VTALRM");
        case SIGPROF:   return("PROF");
        case SIGWINCH:  return("WINCH");
#ifdef SIGLOST
        case SIGLOST:   return("LOST");
#endif
        case SIGUSR1:   return("USR1");
        case SIGUSR2:   return("USR2");
        }
        (void)sprintf(buf, "sig %d", s);
        return(buf);
}

void
hup_handler(s)
        int s;
{
        char logoutfile[MAXPATHLEN];

        (void)sprintf(logoutfile, "%s.%s", _PATH_LOGOUT, loginname);
        if (access(logoutfile, R_OK|X_OK) != 0)
                (void)strcpy(logoutfile, _PATH_LOGOUT);
        if (access(logoutfile, R_OK|X_OK) == 0) {
                char logincmd[2*MAXPATHLEN+32];

                (void) sprintf(logincmd, "%s %d %d %s", logoutfile, unit, speed,
                              loginargs);
                (void) system(logincmd);
        }
        (void) close(0);
        syslog(LOG_INFO, "closed %s slip unit %d (%s)\n", loginname, unit,
               sigstr(s));
        exit(1);
        /* NOTREACHED */
}

main(argc, argv)
        int argc;
        char *argv[];
{
        int fd, s, ldisc, odisc;
        char *name;
#ifdef POSIX
        struct termios tios, otios;
#else
        struct sgttyb tty, otty;
#endif
        char logincmd[2*BUFSIZ+32];
        extern uid_t getuid();

        if ((name = strrchr(argv[0], '/')) == NULL)
                name = argv[0];
        s = getdtablesize();
        for (fd = 3 ; fd < s ; fd++)
                (void) close(fd);
        openlog(name, LOG_PID, LOG_DAEMON);
        uid = getuid();
        if (argc > 1) {
                findid(argv[1]);

                /*
                 * Disassociate from current controlling terminal, if any,
                 * and ensure that the slip line is our controlling terminal.
                 */
#ifdef POSIX
                if (fork() > 0)
                        exit(0);
                if (setsid() != 0)
                        perror("setsid");
#else
                if ((fd = open("/dev/tty", O_RDONLY, 0)) >= 0) {
                        extern char *ttyname();

                        (void) ioctl(fd, TIOCNOTTY, (caddr_t)0);
                        (void) close(fd);
                        /* open slip tty again to acquire as controlling tty? */
                        fd = open(ttyname(0), O_RDWR, 0);
                        if (fd >= 0)
                                (void) close(fd);
                }
                (void) setpgrp(0, getpid());
#endif
                if (argc > 2) {
                        if ((fd = open(argv[2], O_RDWR)) == -1) {
                                perror(argv[2]);
                                exit(2);
                        }
                        (void) dup2(fd, 0);
                        if (fd > 2)
                                close(fd);
                }
#ifdef TIOCSCTTY
                if (ioctl(0, TIOCSCTTY, (caddr_t)0) != 0)
                        perror("ioctl (TIOCSCTTY)");
#endif
        } else {
                extern char *getlogin();

                if ((name = getlogin()) == NULL) {
                        (void) fprintf(stderr, "access denied - no username\n");
                        syslog(LOG_ERR, "access denied - getlogin returned 0\n");
                        exit(1);
                }
                findid(name);
        }
        (void) fchmod(0, 0600);
        (void) fprintf(stderr, "starting slip login for %s\n", loginname);
#ifdef POSIX
        /* set up the line parameters */
        if (tcgetattr(0, &tios) < 0) {
                syslog(LOG_ERR, "tcgetattr: %m");
                exit(1);
        }
        otios = tios;
        cfmakeraw(&tios);
        tios.c_iflag &= ~IMAXBEL;
        if (tcsetattr(0, TCSAFLUSH, &tios) < 0) {
                syslog(LOG_ERR, "tcsetattr: %m");
                exit(1);
        }
        speed = cfgetispeed(&tios);
#else
        /* set up the line parameters */
        if (ioctl(0, TIOCGETP, (caddr_t)&tty) < 0) {
                syslog(LOG_ERR, "ioctl (TIOCGETP): %m");
                exit(1);
        }
        otty = tty;
        speed = tty.sg_ispeed;
        tty.sg_flags = RAW | ANYP;
        if (ioctl(0, TIOCSETP, (caddr_t)&tty) < 0) {
                syslog(LOG_ERR, "ioctl (TIOCSETP): %m");
                exit(1);
        }
#endif
        /* find out what ldisc we started with */
        if (ioctl(0, TIOCGETD, (caddr_t)&odisc) < 0) {
                syslog(LOG_ERR, "ioctl(TIOCGETD) (1): %m");
                exit(1);
        }
        ldisc = SLIPDISC;
        if (ioctl(0, TIOCSETD, (caddr_t)&ldisc) < 0) {
                syslog(LOG_ERR, "ioctl(TIOCSETD): %m");
                exit(1);
        }
        /* find out what unit number we were assigned */
        if (ioctl(0, SLIOCGUNIT, (caddr_t)&unit) < 0) {
                syslog(LOG_ERR, "ioctl (SLIOCGUNIT): %m");
                exit(1);
        }
        (void) signal(SIGHUP, hup_handler);
        (void) signal(SIGTERM, hup_handler);

        syslog(LOG_INFO, "attaching slip unit %d for %s\n", unit, loginname);
        (void)sprintf(logincmd, "%s %d %d %s", loginfile, unit, speed,
                      loginargs);
        /*
         * aim stdout and errout at /dev/null so logincmd output won't
         * babble into the slip tty line.
         */
        (void) close(1);
        if ((fd = open(_PATH_DEVNULL, O_WRONLY)) != 1) {
                if (fd < 0) {
                        syslog(LOG_ERR, "open /dev/null: %m");
                        exit(1);
                }
                (void) dup2(fd, 1);
                (void) close(fd);
        }
        (void) dup2(1, 2);

        /*
         * Run login and logout scripts as root (real and effective);
         * current route(8) is setuid root, and checks the real uid
         * to see whether changes are allowed (or just "route get").
         */
        (void) setuid(0);
        if (s = system(logincmd)) {
                syslog(LOG_ERR, "%s login failed: exit status %d from %s",
                       loginname, s, loginfile);
                (void) ioctl(0, TIOCSETD, (caddr_t)&odisc);
                exit(6);
        }

        /* twiddle thumbs until we get a signal */
        while (1)
                sigpause(0);

        /* NOTREACHED */
}