libexec/rshd/rshd.c

   1 /*-
   2  * Copyright (c) 1988, 1989, 1992, 1993, 1994
   3  *      The Regents of the University of California.  All rights reserved.
   4  * Copyright (c) 2002 Networks Associates Technology, Inc.
   5  * All rights reserved.
   6  *
   7  * Portions of this software were developed for the FreeBSD Project by
   8  * ThinkSec AS and NAI Labs, the Security Research Division of Network
   9  * Associates, Inc.  under DARPA/SPAWAR contract N66001-01-C-8035
  10  * ("CBOSS"), as part of the DARPA CHATS research program.
  11  *
  12  * Redistribution and use in source and binary forms, with or without
  13  * modification, are permitted provided that the following conditions
  14  * are met:
  15  * 1. Redistributions of source code must retain the above copyright
  16  *    notice, this list of conditions and the following disclaimer.
  17  * 2. Redistributions in binary form must reproduce the above copyright
  18  *    notice, this list of conditions and the following disclaimer in the
  19  *    documentation and/or other materials provided with the distribution.
  20  * 3. Neither the name of the University nor the names of its contributors
  21  *    may be used to endorse or promote products derived from this software
  22  *    without specific prior written permission.
  23  *
  24  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  27  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  30  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  34  * SUCH DAMAGE.
  35  */
  36
  37 #ifndef lint
  38 static const char copyright[] =
  39 "@(#) Copyright (c) 1988, 1989, 1992, 1993, 1994\n\
  40         The Regents of the University of California.  All rights reserved.\n";
  41 #endif /* not lint */
  42
  43 #ifndef lint
  44 #if 0
  45 static const char sccsid[] = "@(#)rshd.c        8.2 (Berkeley) 4/6/94";
  46 #endif
  47 #endif /* not lint */
  48
  49 #include <sys/cdefs.h>
  50 __FBSDID("$FreeBSD$");
  51
  52 /*
  53  * remote shell server:
  54  *      [port]\0
  55  *      ruser\0
  56  *      luser\0
  57  *      command\0
  58  *      data
  59  */
  60 #include <sys/param.h>
  61 #include <sys/ioctl.h>
  62 #include <sys/time.h>
  63 #include <sys/socket.h>
  64
  65 #include <netinet/in_systm.h>
  66 #include <netinet/in.h>
  67 #include <netinet/ip.h>
  68 #include <netinet/tcp.h>
  69 #include <arpa/inet.h>
  70 #include <netdb.h>
  71
  72 #include <err.h>
  73 #include <errno.h>
  74 #include <fcntl.h>
  75 #include <libutil.h>
  76 #include <paths.h>
  77 #include <pwd.h>
  78 #include <signal.h>
  79 #include <stdarg.h>
  80 #include <stdio.h>
  81 #include <stdlib.h>
  82 #include <string.h>
  83 #include <syslog.h>
  84 #include <unistd.h>
  85 #include <login_cap.h>
  86
  87 #include <security/pam_appl.h>
  88 #include <security/openpam.h>
  89 #include <sys/wait.h>
  90
  91 static struct pam_conv pamc = { openpam_nullconv, NULL };
  92 static pam_handle_t *pamh;
  93 static int pam_err;
  94
  95 #define PAM_END { \
  96         if ((pam_err = pam_setcred(pamh, PAM_DELETE_CRED)) != PAM_SUCCESS) \
  97                 syslog(LOG_ERR|LOG_AUTH, "pam_setcred(): %s", pam_strerror(pamh, pam_err)); \
  98         if ((pam_err = pam_close_session(pamh,0)) != PAM_SUCCESS) \
  99                 syslog(LOG_ERR|LOG_AUTH, "pam_close_session(): %s", pam_strerror(pamh, pam_err)); \
 100         if ((pam_err = pam_end(pamh, pam_err)) != PAM_SUCCESS) \
 101                 syslog(LOG_ERR|LOG_AUTH, "pam_end(): %s", pam_strerror(pamh, pam_err)); \
 102 }
 103
 104 int     keepalive = 1;
 105 int     log_success;            /* If TRUE, log all successful accesses */
 106 int     sent_null;
 107 int     no_delay;
 108
 109 void     doit(struct sockaddr *);
 110 static void      rshd_errx(int, const char *, ...) __printf0like(2, 3);
 111 void     getstr(char *, int, const char *);
 112 int      local_domain(char *);
 113 char    *topdomain(char *);
 114 void     usage(void);
 115
 116 char     slash[] = "/";
 117 char     bshell[] = _PATH_BSHELL;
 118
 119 #define OPTIONS "aDLln"
 120
 121 int
 122 main(int argc, char *argv[])
 123 {
 124         extern int __check_rhosts_file;
 125         struct linger linger;
 126         socklen_t fromlen;
 127         int ch, on = 1;
 128         struct sockaddr_storage from;
 129
 130         openlog("rshd", LOG_PID | LOG_ODELAY, LOG_DAEMON);
 131
 132         opterr = 0;
 133         while ((ch = getopt(argc, argv, OPTIONS)) != -1)
 134                 switch (ch) {
 135                 case 'a':
 136                         /* ignored for compatibility */
 137                         break;
 138                 case 'l':
 139                         __check_rhosts_file = 0;
 140                         break;
 141                 case 'n':
 142                         keepalive = 0;
 143                         break;
 144                 case 'D':
 145                         no_delay = 1;
 146                         break;
 147                 case 'L':
 148                         log_success = 1;
 149                         break;
 150                 case '?':
 151                 default:
 152                         usage();
 153                         break;
 154                 }
 155
 156         argc -= optind;
 157         argv += optind;
 158
 159         fromlen = sizeof (from);
 160         if (getpeername(0, (struct sockaddr *)&from, &fromlen) < 0) {
 161                 syslog(LOG_ERR, "getpeername: %m");
 162                 exit(1);
 163         }
 164         if (keepalive &&
 165             setsockopt(0, SOL_SOCKET, SO_KEEPALIVE, (char *)&on,
 166             sizeof(on)) < 0)
 167                 syslog(LOG_WARNING, "setsockopt (SO_KEEPALIVE): %m");
 168         linger.l_onoff = 1;
 169         linger.l_linger = 60;                   /* XXX */
 170         if (setsockopt(0, SOL_SOCKET, SO_LINGER, (char *)&linger,
 171             sizeof (linger)) < 0)
 172                 syslog(LOG_WARNING, "setsockopt (SO_LINGER): %m");
 173         if (no_delay &&
 174             setsockopt(0, IPPROTO_TCP, TCP_NODELAY, &on, sizeof(on)) < 0)
 175                 syslog(LOG_WARNING, "setsockopt (TCP_NODELAY): %m");
 176         doit((struct sockaddr *)&from);
 177         /* NOTREACHED */
 178         return(0);
 179 }
 180
 181 extern char **environ;
 182
 183 void
 184 doit(struct sockaddr *fromp)
 185 {
 186         extern char *__rcmd_errstr;     /* syslog hook from libc/net/rcmd.c. */
 187         struct passwd *pwd;
 188         u_short port;
 189         fd_set ready, readfrom;
 190         int cc, fd, nfd, pv[2], pid, s;
 191         int one = 1;
 192         const char *cp, *errorstr;
 193         char sig, buf[BUFSIZ];
 194         char *cmdbuf, luser[16], ruser[16];
 195         char rhost[2 * MAXHOSTNAMELEN + 1];
 196         char numericname[INET6_ADDRSTRLEN];
 197         int af, srcport;
 198         int maxcmdlen;
 199         login_cap_t *lc;
 200
 201         maxcmdlen = (int)sysconf(_SC_ARG_MAX);
 202         if (maxcmdlen <= 0 || (cmdbuf = malloc(maxcmdlen)) == NULL)
 203                 exit(1);
 204
 205         (void) signal(SIGINT, SIG_DFL);
 206         (void) signal(SIGQUIT, SIG_DFL);
 207         (void) signal(SIGTERM, SIG_DFL);
 208         af = fromp->sa_family;
 209         srcport = ntohs(*((in_port_t *)&fromp->sa_data));
 210         if (af == AF_INET) {
 211                 inet_ntop(af, &((struct sockaddr_in *)fromp)->sin_addr,
 212                     numericname, sizeof numericname);
 213         } else if (af == AF_INET6) {
 214                 inet_ntop(af, &((struct sockaddr_in6 *)fromp)->sin6_addr,
 215                     numericname, sizeof numericname);
 216         } else {
 217                 syslog(LOG_ERR, "malformed \"from\" address (af %d)", af);
 218                 exit(1);
 219         }
 220 #ifdef IP_OPTIONS
 221         if (af == AF_INET) {
 222                 u_char optbuf[BUFSIZ/3];
 223                 socklen_t optsize = sizeof(optbuf), ipproto, i;
 224                 struct protoent *ip;
 225
 226                 if ((ip = getprotobyname("ip")) != NULL)
 227                         ipproto = ip->p_proto;
 228                 else
 229                         ipproto = IPPROTO_IP;
 230                 if (!getsockopt(0, ipproto, IP_OPTIONS, optbuf, &optsize) &&
 231                     optsize != 0) {
 232                         for (i = 0; i < optsize; ) {
 233                                 u_char c = optbuf[i];
 234                                 if (c == IPOPT_LSRR || c == IPOPT_SSRR) {
 235                                         syslog(LOG_NOTICE,
 236                                             "connection refused from %s with IP option %s",
 237                                             numericname,
 238                                             c == IPOPT_LSRR ? "LSRR" : "SSRR");
 239                                         exit(1);
 240                                 }
 241                                 if (c == IPOPT_EOL)
 242                                         break;
 243                                 i += (c == IPOPT_NOP) ? 1 : optbuf[i+1];
 244                         }
 245                 }
 246         }
 247 #endif
 248
 249         if (srcport >= IPPORT_RESERVED ||
 250             srcport < IPPORT_RESERVED/2) {
 251                 syslog(LOG_NOTICE|LOG_AUTH,
 252                     "connection from %s on illegal port %u",
 253                     numericname,
 254                     srcport);
 255                 exit(1);
 256         }
 257
 258         (void) alarm(60);
 259         port = 0;
 260         s = 0;          /* not set or used if port == 0 */
 261         for (;;) {
 262                 char c;
 263                 if ((cc = read(STDIN_FILENO, &c, 1)) != 1) {
 264                         if (cc < 0)
 265                                 syslog(LOG_NOTICE, "read: %m");
 266                         shutdown(0, SHUT_RDWR);
 267                         exit(1);
 268                 }
 269                 if (c == 0)
 270                         break;
 271                 port = port * 10 + c - '0';
 272         }
 273
 274         (void) alarm(0);
 275         if (port != 0) {
 276                 int lport = IPPORT_RESERVED - 1;
 277                 s = rresvport_af(&lport, af);
 278                 if (s < 0) {
 279                         syslog(LOG_ERR, "can't get stderr port: %m");
 280                         exit(1);
 281                 }
 282                 if (port >= IPPORT_RESERVED ||
 283                     port < IPPORT_RESERVED/2) {
 284                         syslog(LOG_NOTICE|LOG_AUTH,
 285                             "2nd socket from %s on unreserved port %u",
 286                             numericname,
 287                             port);
 288                         exit(1);
 289                 }
 290                 *((in_port_t *)&fromp->sa_data) = htons(port);
 291                 if (connect(s, fromp, fromp->sa_len) < 0) {
 292                         syslog(LOG_INFO, "connect second port %d: %m", port);
 293                         exit(1);
 294                 }
 295         }
 296
 297         errorstr = NULL;
 298         realhostname_sa(rhost, sizeof(rhost) - 1, fromp, fromp->sa_len);
 299         rhost[sizeof(rhost) - 1] = '\0';
 300         /* XXX truncation! */
 301
 302         (void) alarm(60);
 303         getstr(ruser, sizeof(ruser), "ruser");
 304         getstr(luser, sizeof(luser), "luser");
 305         getstr(cmdbuf, maxcmdlen, "command");
 306         (void) alarm(0);
 307
 308         pam_err = pam_start("rsh", luser, &pamc, &pamh);
 309         if (pam_err != PAM_SUCCESS) {
 310                 syslog(LOG_ERR|LOG_AUTH, "pam_start(): %s",
 311                     pam_strerror(pamh, pam_err));
 312                 rshd_errx(1, "Login incorrect.");
 313         }
 314
 315         if ((pam_err = pam_set_item(pamh, PAM_RUSER, ruser)) != PAM_SUCCESS ||
 316             (pam_err = pam_set_item(pamh, PAM_RHOST, rhost)) != PAM_SUCCESS) {
 317                 syslog(LOG_ERR|LOG_AUTH, "pam_set_item(): %s",
 318                     pam_strerror(pamh, pam_err));
 319                 rshd_errx(1, "Login incorrect.");
 320         }
 321
 322         pam_err = pam_authenticate(pamh, 0);
 323         if (pam_err == PAM_SUCCESS) {
 324                 if ((pam_err = pam_get_user(pamh, &cp, NULL)) == PAM_SUCCESS) {
 325                         strlcpy(luser, cp, sizeof(luser));
 326                         /* XXX truncation! */
 327                 }
 328                 pam_err = pam_acct_mgmt(pamh, 0);
 329         }
 330         if (pam_err != PAM_SUCCESS) {
 331                 syslog(LOG_INFO|LOG_AUTH,
 332                     "%s@%s as %s: permission denied (%s). cmd='%.80s'",
 333                     ruser, rhost, luser, pam_strerror(pamh, pam_err), cmdbuf);
 334                 rshd_errx(1, "Login incorrect.");
 335         }
 336
 337         setpwent();
 338         pwd = getpwnam(luser);
 339         if (pwd == NULL) {
 340                 syslog(LOG_INFO|LOG_AUTH,
 341                     "%s@%s as %s: unknown login. cmd='%.80s'",
 342                     ruser, rhost, luser, cmdbuf);
 343                 if (errorstr == NULL)
 344                         errorstr = "Login incorrect.";
 345                 rshd_errx(1, errorstr, rhost);
 346         }
 347
 348         lc = login_getpwclass(pwd);
 349         if (pwd->pw_uid)
 350                 auth_checknologin(lc);
 351
 352         if (chdir(pwd->pw_dir) < 0) {
 353                 if (chdir("/") < 0 ||
 354                     login_getcapbool(lc, "requirehome", !!pwd->pw_uid)) {
 355                         syslog(LOG_INFO|LOG_AUTH,
 356                         "%s@%s as %s: no home directory. cmd='%.80s'",
 357                         ruser, rhost, luser, cmdbuf);
 358                         rshd_errx(0, "No remote home directory.");
 359                 }
 360                 pwd->pw_dir = slash;
 361         }
 362
 363         if (lc != NULL && fromp->sa_family == AF_INET) {        /*XXX*/
 364                 char    remote_ip[MAXHOSTNAMELEN];
 365
 366                 strlcpy(remote_ip, numericname, sizeof(remote_ip));
 367                 /* XXX truncation! */
 368                 if (!auth_hostok(lc, rhost, remote_ip)) {
 369                         syslog(LOG_INFO|LOG_AUTH,
 370                             "%s@%s as %s: permission denied (%s). cmd='%.80s'",
 371                             ruser, rhost, luser, __rcmd_errstr,
 372                             cmdbuf);
 373                         rshd_errx(1, "Login incorrect.");
 374                 }
 375                 if (!auth_timeok(lc, time(NULL)))
 376                         rshd_errx(1, "Logins not available right now");
 377         }
 378
 379         /*
 380          * PAM modules might add supplementary groups in
 381          * pam_setcred(), so initialize them first.
 382          * But we need to open the session as root.
 383          */
 384         if (setusercontext(lc, pwd, pwd->pw_uid, LOGIN_SETGROUP) != 0) {
 385                 syslog(LOG_ERR, "setusercontext: %m");
 386                 exit(1);
 387         }
 388
 389         if ((pam_err = pam_open_session(pamh, 0)) != PAM_SUCCESS) {
 390                 syslog(LOG_ERR, "pam_open_session: %s", pam_strerror(pamh, pam_err));
 391         } else if ((pam_err = pam_setcred(pamh, PAM_ESTABLISH_CRED)) != PAM_SUCCESS) {
 392                 syslog(LOG_ERR, "pam_setcred: %s", pam_strerror(pamh, pam_err));
 393         }
 394
 395         (void) write(STDERR_FILENO, "\0", 1);
 396         sent_null = 1;
 397
 398         if (port) {
 399                 if (pipe(pv) < 0)
 400                         rshd_errx(1, "Can't make pipe.");
 401                 pid = fork();
 402                 if (pid == -1)
 403                         rshd_errx(1, "Can't fork; try again.");
 404                 if (pid) {
 405                         (void) close(0);
 406                         (void) close(1);
 407                         (void) close(2);
 408                         (void) close(pv[1]);
 409
 410                         FD_ZERO(&readfrom);
 411                         FD_SET(s, &readfrom);
 412                         FD_SET(pv[0], &readfrom);
 413                         if (pv[0] > s)
 414                                 nfd = pv[0];
 415                         else
 416                                 nfd = s;
 417                                 ioctl(pv[0], FIONBIO, (char *)&one);
 418
 419                         /* should set s nbio! */
 420                         nfd++;
 421                         do {
 422                                 ready = readfrom;
 423                                 if (select(nfd, &ready, (fd_set *)0,
 424                                   (fd_set *)0, (struct timeval *)0) < 0)
 425                                         break;
 426                                 if (FD_ISSET(s, &ready)) {
 427                                         int     ret;
 428                                                 ret = read(s, &sig, 1);
 429                                 if (ret <= 0)
 430                                         FD_CLR(s, &readfrom);
 431                                 else
 432                                         killpg(pid, sig);
 433                                 }
 434                                 if (FD_ISSET(pv[0], &ready)) {
 435                                         errno = 0;
 436                                         cc = read(pv[0], buf, sizeof(buf));
 437                                         if (cc <= 0) {
 438                                                 shutdown(s, SHUT_RDWR);
 439                                                 FD_CLR(pv[0], &readfrom);
 440                                         } else {
 441                                                 (void)write(s, buf, cc);
 442                                         }
 443                                 }
 444
 445                         } while (FD_ISSET(s, &readfrom) ||
 446                             FD_ISSET(pv[0], &readfrom));
 447                         PAM_END;
 448                         exit(0);
 449                 }
 450                 (void) close(s);
 451                 (void) close(pv[0]);
 452                 dup2(pv[1], 2);
 453                 close(pv[1]);
 454         }
 455         else {
 456                 pid = fork();
 457                 if (pid == -1)
 458                         rshd_errx(1, "Can't fork; try again.");
 459                 if (pid) {
 460                         /* Parent. */
 461                         while (wait(NULL) > 0 || errno == EINTR)
 462                                 /* nothing */ ;
 463                         PAM_END;
 464                         exit(0);
 465                 }
 466         }
 467
 468         for (fd = getdtablesize(); fd > 2; fd--)
 469                 (void) close(fd);
 470         if (setsid() == -1)
 471                 syslog(LOG_ERR, "setsid() failed: %m");
 472         if (setlogin(pwd->pw_name) < 0)
 473                 syslog(LOG_ERR, "setlogin() failed: %m");
 474
 475         if (*pwd->pw_shell == '\0')
 476                 pwd->pw_shell = bshell;
 477         (void) pam_setenv(pamh, "HOME", pwd->pw_dir, 1);
 478         (void) pam_setenv(pamh, "SHELL", pwd->pw_shell, 1);
 479         (void) pam_setenv(pamh, "USER", pwd->pw_name, 1);
 480         (void) pam_setenv(pamh, "PATH", _PATH_DEFPATH, 1);
 481         environ = pam_getenvlist(pamh);
 482         (void) pam_end(pamh, pam_err);
 483         cp = strrchr(pwd->pw_shell, '/');
 484         if (cp)
 485                 cp++;
 486         else
 487                 cp = pwd->pw_shell;
 488
 489         if (setusercontext(lc, pwd, pwd->pw_uid,
 490                 LOGIN_SETALL & ~LOGIN_SETGROUP) < 0) {
 491                 syslog(LOG_ERR, "setusercontext(): %m");
 492                 exit(1);
 493         }
 494         login_close(lc);
 495         endpwent();
 496         if (log_success || pwd->pw_uid == 0) {
 497                     syslog(LOG_INFO|LOG_AUTH, "%s@%s as %s: cmd='%.80s'",
 498                         ruser, rhost, luser, cmdbuf);
 499         }
 500         execl(pwd->pw_shell, cp, "-c", cmdbuf, (char *)NULL);
 501         err(1, "%s", pwd->pw_shell);
 502         exit(1);
 503 }
 504
 505 /*
 506  * Report error to client.  Note: can't be used until second socket has
 507  * connected to client, or older clients will hang waiting for that
 508  * connection first.
 509  */
 510
 511 static void
 512 rshd_errx(int errcode, const char *fmt, ...)
 513 {
 514         va_list ap;
 515
 516         va_start(ap, fmt);
 517
 518         if (sent_null == 0)
 519                 write(STDERR_FILENO, "\1", 1);
 520
 521         verrx(errcode, fmt, ap);
 522         /* NOTREACHED */
 523 }
 524
 525 void
 526 getstr(char *buf, int cnt, const char *error)
 527 {
 528         char c;
 529
 530         do {
 531                 if (read(STDIN_FILENO, &c, 1) != 1)
 532                         exit(1);
 533                 *buf++ = c;
 534                 if (--cnt == 0)
 535                         rshd_errx(1, "%s too long", error);
 536         } while (c != 0);
 537 }
 538
 539 /*
 540  * Check whether host h is in our local domain,
 541  * defined as sharing the last two components of the domain part,
 542  * or the entire domain part if the local domain has only one component.
 543  * If either name is unqualified (contains no '.'),
 544  * assume that the host is local, as it will be
 545  * interpreted as such.
 546  */
 547 int
 548 local_domain(char *h)
 549 {
 550         char localhost[MAXHOSTNAMELEN];
 551         char *p1, *p2;
 552
 553         localhost[0] = 0;
 554         (void) gethostname(localhost, sizeof(localhost) - 1);
 555         localhost[sizeof(localhost) - 1] = '\0';
 556         /* XXX truncation! */
 557         p1 = topdomain(localhost);
 558         p2 = topdomain(h);
 559         if (p1 == NULL || p2 == NULL || !strcasecmp(p1, p2))
 560                 return (1);
 561         return (0);
 562 }
 563
 564 char *
 565 topdomain(char *h)
 566 {
 567         char *p, *maybe = NULL;
 568         int dots = 0;
 569
 570         for (p = h + strlen(h); p >= h; p--) {
 571                 if (*p == '.') {
 572                         if (++dots == 2)
 573                                 return (p);
 574                         maybe = p;
 575                 }
 576         }
 577         return (maybe);
 578 }
 579
 580 void
 581 usage(void)
 582 {
 583
 584         syslog(LOG_ERR, "usage: rshd [-%s]", OPTIONS);
 585         exit(2);
 586 }