usr.sbin/sliplogin/sliplogin.c

   1 /*-
   2  * Copyright (c) 1990, 1993
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  * 3. Neither the name of the University nor the names of its contributors
  14  *    may be used to endorse or promote products derived from this software
  15  *    without specific prior written permission.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  27  * SUCH DAMAGE.
  28  *
  29  * @(#) Copyright (c) 1990, 1993 The Regents of the University of California.  All rights reserved.
  30  * @(#)sliplogin.c        8.2 (Berkeley) 2/1/94
  31  * $FreeBSD: src/usr.sbin/sliplogin/sliplogin.c,v 1.9.6.2 2001/07/19 05:21:28 kris Exp $
  32  * $DragonFly: src/usr.sbin/sliplogin/sliplogin.c,v 1.5 2008/09/14 22:04:36 swildner Exp $
  33  */
  34
  35 /*
  36  * sliplogin.c
  37  * [MUST BE RUN SUID, SLOPEN DOES A SUSER()!]
  38  *
  39  * This program initializes its own tty port to be an async TCP/IP interface.
  40  * It sets the line discipline to slip, invokes a shell script to initialize
  41  * the network interface, then pauses forever waiting for hangup.
  42  *
  43  * It is a remote descendant of several similar programs with incestuous ties:
  44  * - Kirk Smith's slipconf, modified by Richard Johnsson @ DEC WRL.
  45  * - slattach, probably by Rick Adams but touched by countless hordes.
  46  * - the original sliplogin for 4.2bsd, Doug Kingston the mover behind it.
  47  *
  48  * There are two forms of usage:
  49  *
  50  * "sliplogin"
  51  * Invoked simply as "sliplogin", the program looks up the username
  52  * in the file /etc/slip.hosts.
  53  * If an entry is found, the line on fd0 is configured for SLIP operation
  54  * as specified in the file.
  55  *
  56  * "sliplogin IPhostlogin </dev/ttyb"
  57  * Invoked by root with a username, the name is looked up in the
  58  * /etc/slip.hosts file and if found fd0 is configured as in case 1.
  59  */
  60
  61 #include <sys/param.h>
  62 #include <sys/socket.h>
  63 #include <sys/file.h>
  64 #include <sys/stat.h>
  65 #include <syslog.h>
  66 #include <netdb.h>
  67
  68 #include <termios.h>
  69 #include <sys/ioctl.h>
  70 #include <net/slip.h>
  71 #include <net/if.h>
  72
  73 #include <stdio.h>
  74 #include <errno.h>
  75 #include <ctype.h>
  76 #include <paths.h>
  77 #include <string.h>
  78 #include <unistd.h>
  79 #include <stdlib.h>
  80 #include <signal.h>
  81 #include "pathnames.h"
  82
  83 extern char **environ;
  84
  85 static char *restricted_environ[] = {
  86         "PATH=" _PATH_STDPATH,
  87         NULL
  88 };
  89
  90 int     unit;
  91 int     slip_mode;
  92 speed_t speed;
  93 int     uid;
  94 int     keepal;
  95 int     outfill;
  96 int     slunit;
  97 char    loginargs[BUFSIZ];
  98 char    loginfile[MAXPATHLEN];
  99 char    loginname[BUFSIZ];
 100 static char raddr[32];                  /* remote address */
 101 char ifname[IFNAMSIZ];                  /* interface name */
 102 static  char pidfilename[MAXPATHLEN];   /* name of pid file */
 103 static  char iffilename[MAXPATHLEN];    /* name of if file */
 104 static  pid_t   pid;                    /* our pid */
 105
 106 char *
 107 make_ipaddr(void)
 108 {
 109 static char address[20] ="";
 110 struct hostent *he;
 111 unsigned long ipaddr;
 112
 113 address[0] = '\0';
 114 if ((he = gethostbyname(raddr)) != NULL) {
 115         ipaddr = ntohl(*(long *)he->h_addr_list[0]);
 116         sprintf(address, "%lu.%lu.%lu.%lu",
 117                 ipaddr >> 24,
 118                 (ipaddr & 0x00ff0000) >> 16,
 119                 (ipaddr & 0x0000ff00) >> 8,
 120                 (ipaddr & 0x000000ff));
 121         }
 122
 123 return address;
 124 }
 125
 126 struct slip_modes {
 127         char    *sm_name;
 128         int     sm_or_flag;
 129         int     sm_and_flag;
 130 }        modes[] = {
 131         "normal",       0        , 0        ,
 132         "compress",     IFF_LINK0, IFF_LINK2,
 133         "noicmp",       IFF_LINK1, 0        ,
 134         "autocomp",     IFF_LINK2, IFF_LINK0,
 135 };
 136
 137 void
 138 findid(char *name)
 139 {
 140         FILE *fp;
 141         static char slopt[5][16];
 142         static char laddr[16];
 143         static char mask[16];
 144         char   slparmsfile[MAXPATHLEN];
 145         char user[16];
 146         char buf[128];
 147         int i, j, n;
 148
 149         environ = restricted_environ; /* minimal protection for system() */
 150
 151         strncpy(loginname, name, sizeof(loginname)-1);
 152         loginname[sizeof(loginname)-1] = '\0';
 153
 154         if ((fp = fopen(_PATH_ACCESS, "r")) == NULL) {
 155         accfile_err:
 156                 syslog(LOG_ERR, "%s: %m\n", _PATH_ACCESS);
 157                 exit(1);
 158         }
 159         while (fgets(loginargs, sizeof(loginargs) - 1, fp)) {
 160                 if (ferror(fp))
 161                         goto accfile_err;
 162                 if (loginargs[0] == '#' || isspace(loginargs[0]))
 163                         continue;
 164                 n = sscanf(loginargs, "%15s%*[ \t]%15s%*[ \t]%15s%*[ \t]%15s%*[ \t]%15s%*[ \t]%15s%*[ \t]%15s%*[ \t]%15s%*[ \t]%15s\n",
 165                         user, laddr, raddr, mask, slopt[0], slopt[1],
 166                         slopt[2], slopt[3], slopt[4]);
 167                 if (n < 4) {
 168                         syslog(LOG_ERR, "%s: wrong format\n", _PATH_ACCESS);
 169                         exit(1);
 170                 }
 171                 if (strcmp(user, name) != 0)
 172                         continue;
 173
 174                 fclose(fp);
 175
 176                 slip_mode = 0;
 177                 for (i = 0; i < n - 4; i++) {
 178                         for (j = 0; j < sizeof(modes)/sizeof(struct slip_modes);
 179                                 j++) {
 180                                 if (strcmp(modes[j].sm_name, slopt[i]) == 0) {
 181                                         slip_mode |= (modes[j].sm_or_flag);
 182                                         slip_mode &= ~(modes[j].sm_and_flag);
 183                                         break;
 184                                 }
 185                         }
 186                 }
 187
 188                 /*
 189                  * we've found the guy we're looking for -- see if
 190                  * there's a login file we can use.  First check for
 191                  * one specific to this host.  If none found, try for
 192                  * a generic one.
 193                  */
 194                 snprintf(loginfile, sizeof(loginfile), "%s.%s", _PATH_SLOGIN, name);
 195                 if (access(loginfile, R_OK|X_OK) != 0) {
 196                         strncpy(loginfile, _PATH_SLOGIN, sizeof(loginfile)-1);
 197                         loginfile[sizeof(loginfile)-1] = '\0';
 198                         if (access(loginfile, R_OK|X_OK)) {
 199                                 syslog(LOG_ERR,
 200                                        "access denied for %s - no %s\n",
 201                                        name, _PATH_SLOGIN);
 202                                 exit(5);
 203                         }
 204                 }
 205                 snprintf(slparmsfile, sizeof(slparmsfile), "%s.%s", _PATH_SLPARMS, name);
 206                 if (access(slparmsfile, R_OK|X_OK) != 0) {
 207                         strncpy(slparmsfile, _PATH_SLPARMS, sizeof(slparmsfile)-1);
 208                         slparmsfile[sizeof(slparmsfile)-1] = '\0';
 209                         if (access(slparmsfile, R_OK|X_OK))
 210                                 *slparmsfile = '\0';
 211                 }
 212                 keepal = outfill = 0;
 213                 slunit = -1;
 214                 if (*slparmsfile) {
 215                         if ((fp = fopen(slparmsfile, "r")) == NULL) {
 216                         slfile_err:
 217                                 syslog(LOG_ERR, "%s: %m\n", slparmsfile);
 218                                 exit(1);
 219                         }
 220                         n = 0;
 221                         while (fgets(buf, sizeof(buf) - 1, fp) != NULL) {
 222                                 if (ferror(fp))
 223                                         goto slfile_err;
 224                                 if (buf[0] == '#' || isspace(buf[0]))
 225                                         continue;
 226                                 n = sscanf(buf, "%d %d %d", &keepal, &outfill, &slunit);
 227                                 if (n < 1) {
 228                                 slwrong_fmt:
 229                                         syslog(LOG_ERR, "%s: wrong format\n", slparmsfile);
 230                                         exit(1);
 231                                 }
 232                                 fclose(fp);
 233                                 break;
 234                         }
 235                         if (n == 0)
 236                                 goto slwrong_fmt;
 237                 }
 238
 239                 return;
 240         }
 241         syslog(LOG_ERR, "SLIP access denied for %s\n", name);
 242         exit(4);
 243         /* NOTREACHED */
 244 }
 245
 246 char *
 247 sigstr(int s)
 248 {
 249         static char buf[32];
 250
 251         switch (s) {
 252         case SIGHUP:    return("HUP");
 253         case SIGINT:    return("INT");
 254         case SIGQUIT:   return("QUIT");
 255         case SIGILL:    return("ILL");
 256         case SIGTRAP:   return("TRAP");
 257         case SIGIOT:    return("IOT");
 258         case SIGEMT:    return("EMT");
 259         case SIGFPE:    return("FPE");
 260         case SIGKILL:   return("KILL");
 261         case SIGBUS:    return("BUS");
 262         case SIGSEGV:   return("SEGV");
 263         case SIGSYS:    return("SYS");
 264         case SIGPIPE:   return("PIPE");
 265         case SIGALRM:   return("ALRM");
 266         case SIGTERM:   return("TERM");
 267         case SIGURG:    return("URG");
 268         case SIGSTOP:   return("STOP");
 269         case SIGTSTP:   return("TSTP");
 270         case SIGCONT:   return("CONT");
 271         case SIGCHLD:   return("CHLD");
 272         case SIGTTIN:   return("TTIN");
 273         case SIGTTOU:   return("TTOU");
 274         case SIGIO:     return("IO");
 275         case SIGXCPU:   return("XCPU");
 276         case SIGXFSZ:   return("XFSZ");
 277         case SIGVTALRM: return("VTALRM");
 278         case SIGPROF:   return("PROF");
 279         case SIGWINCH:  return("WINCH");
 280 #ifdef SIGLOST
 281         case SIGLOST:   return("LOST");
 282 #endif
 283         case SIGUSR1:   return("USR1");
 284         case SIGUSR2:   return("USR2");
 285         }
 286         snprintf(buf, sizeof(buf), "sig %d", s);
 287         return(buf);
 288 }
 289
 290 void
 291 hup_handler(int s)
 292 {
 293         char logoutfile[MAXPATHLEN];
 294
 295         close(0);
 296         seteuid(0);
 297         snprintf(logoutfile, sizeof(logoutfile), "%s.%s", _PATH_SLOGOUT, loginname);
 298         if (access(logoutfile, R_OK|X_OK) != 0) {
 299                 strncpy(logoutfile, _PATH_SLOGOUT, sizeof(logoutfile)-1);
 300                 logoutfile[sizeof(logoutfile)-1] = '\0';
 301         }
 302         if (access(logoutfile, R_OK|X_OK) == 0) {
 303                 char logincmd[2*MAXPATHLEN+32];
 304
 305                 snprintf(logincmd, sizeof(logincmd), "%s %d %ld %s", logoutfile, unit, speed, loginargs);
 306                 system(logincmd);
 307         }
 308         syslog(LOG_INFO, "closed %s slip unit %d (%s)\n", loginname, unit,
 309                sigstr(s));
 310         if (unlink(pidfilename) < 0 && errno != ENOENT)
 311                 syslog(LOG_WARNING, "unable to delete pid file: %m");
 312         if (unlink(iffilename) < 0 && errno != ENOENT)
 313                 syslog(LOG_WARNING, "unable to delete if file: %m");
 314         exit(1);
 315         /* NOTREACHED */
 316 }
 317
 318
 319 /* Modify the slip line mode and add any compression or no-icmp flags. */
 320 void
 321 line_flags(int unit)
 322 {
 323         struct ifreq ifr;
 324         int s;
 325
 326         /* open a socket as the handle to the interface */
 327         s = socket(AF_INET, SOCK_DGRAM, 0);
 328         if (s < 0) {
 329                 syslog(LOG_ERR, "socket: %m");
 330                 exit(1);
 331         }
 332         sprintf(ifr.ifr_name, "sl%d", unit);
 333
 334         /* get the flags for the interface */
 335         if (ioctl(s, SIOCGIFFLAGS, (caddr_t)&ifr) < 0) {
 336                 syslog(LOG_ERR, "ioctl (SIOCGIFFLAGS): %m");
 337                 exit(1);
 338         }
 339
 340         /* Assert any compression or no-icmp flags. */
 341 #define SLMASK (~(IFF_LINK0 | IFF_LINK1 | IFF_LINK2))
 342         ifr.ifr_flags &= SLMASK;
 343         ifr.ifr_flags |= slip_mode;
 344         if (ioctl(s, SIOCSIFFLAGS, (caddr_t)&ifr) < 0) {
 345                 syslog(LOG_ERR, "ioctl (SIOCSIFFLAGS): %m");
 346                 exit(1);
 347         }
 348         close(s);
 349 }
 350
 351 int
 352 main(int argc, char *argv[])
 353 {
 354         int fd, s, ldisc;
 355         char *name;
 356         struct termios tios, otios;
 357         char logincmd[2*BUFSIZ+32];
 358         extern uid_t getuid();
 359
 360         FILE *pidfile;                          /* pid file */
 361         FILE *iffile;                           /* interfaces file */
 362         char *p;
 363         int n;
 364         char devnam[MAXPATHLEN] = _PATH_TTY;   /* Device name */
 365
 366         if ((name = strrchr(argv[0], '/')) == NULL)
 367                 name = argv[0];
 368         s = getdtablesize();
 369         for (fd = 3 ; fd < s ; fd++)
 370                 close(fd);
 371         openlog(name, LOG_PID|LOG_PERROR, LOG_DAEMON);
 372         uid = getuid();
 373         if (argc > 1) {
 374                 findid(argv[1]);
 375
 376                 /*
 377                  * Disassociate from current controlling terminal, if any,
 378                  * and ensure that the slip line is our controlling terminal.
 379                  */
 380                 if (daemon(1, 1)) {
 381                         syslog(LOG_ERR, "daemon(1, 1): %m");
 382                         exit(1);
 383                 }
 384                 if (argc > 2) {
 385                         if ((fd = open(argv[2], O_RDWR)) == -1) {
 386                                 syslog(LOG_ERR, "open %s: %m", argv[2]);
 387                                 exit(2);
 388                         }
 389                         dup2(fd, 0);
 390                         if (fd > 2)
 391                                 close(fd);
 392                 }
 393                 if (ioctl(0, TIOCSCTTY, 0) == -1) {
 394                         syslog(LOG_ERR, "ioctl (TIOCSCTTY): %m");
 395                         exit(1);
 396                 }
 397                 if (tcsetpgrp(0, getpid()) < 0) {
 398                         syslog(LOG_ERR, "tcsetpgrp failed: %m");
 399                         exit(1);
 400                 }
 401         } else {
 402                 if ((name = getlogin()) == NULL) {
 403                         syslog(LOG_ERR, "access denied - login name not found\n");
 404                         exit(1);
 405                 }
 406                 findid(name);
 407         }
 408         fchmod(0, 0600);
 409         fprintf(stderr, "starting slip login for %s\n", loginname);
 410         fprintf(stderr, "your address is %s\n\n", make_ipaddr());
 411
 412         fflush(stderr);
 413         sleep(1);
 414
 415         /* set up the line parameters */
 416         if (tcgetattr(0, &tios) < 0) {
 417                 syslog(LOG_ERR, "tcgetattr: %m");
 418                 exit(1);
 419         }
 420         otios = tios;
 421         cfmakeraw(&tios);
 422         if (tcsetattr(0, TCSAFLUSH, &tios) < 0) {
 423                 syslog(LOG_ERR, "tcsetattr: %m");
 424                 exit(1);
 425         }
 426         speed = cfgetispeed(&tios);
 427
 428         ldisc = SLIPDISC;
 429         if (ioctl(0, TIOCSETD, &ldisc) < 0) {
 430                 syslog(LOG_ERR, "ioctl(TIOCSETD): %m");
 431                 exit(1);
 432         }
 433         if (slunit >= 0 && ioctl(0, SLIOCSUNIT, &slunit) < 0) {
 434                 syslog(LOG_ERR, "ioctl (SLIOCSUNIT): %m");
 435                 exit(1);
 436         }
 437         /* find out what unit number we were assigned */
 438         if (ioctl(0, SLIOCGUNIT, &unit) < 0) {
 439                 syslog(LOG_ERR, "ioctl (SLIOCGUNIT): %m");
 440                 exit(1);
 441         }
 442         signal(SIGHUP, hup_handler);
 443         signal(SIGTERM, hup_handler);
 444
 445         if (keepal > 0) {
 446                 signal(SIGURG, hup_handler);
 447                 if (ioctl(0, SLIOCSKEEPAL, &keepal) < 0) {
 448                         syslog(LOG_ERR, "ioctl(SLIOCSKEEPAL): %m");
 449                         exit(1);
 450                 }
 451         }
 452         if (outfill > 0 && ioctl(0, SLIOCSOUTFILL, &outfill) < 0) {
 453                 syslog(LOG_ERR, "ioctl(SLIOCSOUTFILL): %m");
 454                 exit(1);
 455         }
 456
 457         /* write pid to file */
 458         pid = getpid();
 459         sprintf(ifname, "sl%d", unit);
 460         sprintf(pidfilename, "%s%s.pid", _PATH_VARRUN, ifname);
 461         if ((pidfile = fopen(pidfilename, "w")) != NULL) {
 462                 fprintf(pidfile, "%d\n", pid);
 463                 fclose(pidfile);
 464         } else {
 465                 syslog(LOG_ERR, "Failed to create pid file %s: %m",
 466                                 pidfilename);
 467                 pidfilename[0] = 0;
 468         }
 469
 470         /* write interface unit number to file */
 471         p = ttyname(0);
 472         if (p)
 473                 strcpy(devnam, p);
 474         for (n = strlen(devnam); n > 0; n--)
 475                 if (devnam[n] == '/') {
 476                         n++;
 477                         break;
 478                 }
 479         sprintf(iffilename, "%s%s.if", _PATH_VARRUN, &devnam[n]);
 480         if ((iffile = fopen(iffilename, "w")) != NULL) {
 481                 fprintf(iffile, "sl%d\n", unit);
 482                 fclose(iffile);
 483         } else {
 484                 syslog(LOG_ERR, "Failed to create if file %s: %m", iffilename);
 485                 iffilename[0] = 0;
 486         }
 487
 488
 489         syslog(LOG_INFO, "attaching slip unit %d for %s\n", unit, loginname);
 490         snprintf(logincmd, sizeof(logincmd), "%s %d %ld %s", loginfile, unit, speed,
 491                  loginargs);
 492         /*
 493          * aim stdout and errout at /dev/null so logincmd output won't
 494          * babble into the slip tty line.
 495          */
 496         close(1);
 497         if ((fd = open(_PATH_DEVNULL, O_WRONLY)) != 1) {
 498                 if (fd < 0) {
 499                         syslog(LOG_ERR, "open %s: %m", _PATH_DEVNULL);
 500                         exit(1);
 501                 }
 502                 dup2(fd, 1);
 503                 close(fd);
 504         }
 505         dup2(1, 2);
 506
 507         /*
 508          * Run login and logout scripts as root (real and effective);
 509          * current route(8) is setuid root, and checks the real uid
 510          * to see whether changes are allowed (or just "route get").
 511          */
 512         setuid(0);
 513         if (s = system(logincmd)) {
 514                 syslog(LOG_ERR, "%s login failed: exit status %d from %s",
 515                        loginname, s, loginfile);
 516                 exit(6);
 517         }
 518
 519         /* Handle any compression or no-icmp flags. */
 520         line_flags(unit);
 521
 522         /* reset uid to users' to allow the user to give a signal. */
 523         seteuid(uid);
 524         /* twiddle thumbs until we get a signal */
 525         while (1)
 526                 sigpause(0);
 527
 528         /* NOTREACHED */
 529 }