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. All advertising materials mentioning features or use of this software
  21  *    must display the following acknowledgement:
  22  *      This product includes software developed by the University of
  23  *      California, Berkeley and its contributors.
  24  * 4. Neither the name of the University nor the names of its contributors
  25  *    may be used to endorse or promote products derived from this software
  26  *    without specific prior written permission.
  27  *
  28  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  29  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  30  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  31  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  32  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  33  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  34  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  35  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  36  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  37  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  38  * SUCH DAMAGE.
  39  */
  40
  41 #ifndef lint
  42 static const char copyright[] =
  43 "@(#) Copyright (c) 1988, 1989, 1992, 1993, 1994\n\
  44         The Regents of the University of California.  All rights reserved.\n";
  45 #endif /* not lint */
  46
  47 #ifndef lint
  48 #if 0
  49 static const char sccsid[] = "@(#)rshd.c        8.2 (Berkeley) 4/6/94";
  50 #endif
  51 #endif /* not lint */
  52
  53 #include <sys/cdefs.h>
  54 __FBSDID("$FreeBSD$");
  55
  56 /*
  57  * remote shell server:
  58  *      [port]\0
  59  *      ruser\0
  60  *      luser\0
  61  *      command\0
  62  *      data
  63  */
  64 #include <sys/param.h>
  65 #include <sys/ioctl.h>
  66 #include <sys/time.h>
  67 #include <sys/socket.h>
  68
  69 #include <netinet/in_systm.h>
  70 #include <netinet/in.h>
  71 #include <netinet/ip.h>
  72 #include <netinet/tcp.h>
  73 #include <arpa/inet.h>
  74 #include <netdb.h>
  75
  76 #include <err.h>
  77 #include <errno.h>
  78 #include <fcntl.h>
  79 #include <libutil.h>
  80 #include <paths.h>
  81 #include <pwd.h>
  82 #include <signal.h>
  83 #include <stdarg.h>
  84 #include <stdio.h>
  85 #include <stdlib.h>
  86 #include <string.h>
  87 #include <syslog.h>
  88 #include <unistd.h>
  89 #include <login_cap.h>
  90
  91 #include <security/pam_appl.h>
  92 #include <security/openpam.h>
  93 #include <sys/wait.h>
  94
  95 static struct pam_conv pamc = { openpam_nullconv, NULL };
  96 static pam_handle_t *pamh;
  97 static int pam_err;
  98
  99 #define PAM_END { \
 100         if ((pam_err = pam_setcred(pamh, PAM_DELETE_CRED)) != PAM_SUCCESS) \
 101                 syslog(LOG_ERR|LOG_AUTH, "pam_setcred(): %s", pam_strerror(pamh, pam_err)); \
 102         if ((pam_err = pam_close_session(pamh,0)) != PAM_SUCCESS) \
 103                 syslog(LOG_ERR|LOG_AUTH, "pam_close_session(): %s", pam_strerror(pamh, pam_err)); \
 104         if ((pam_err = pam_end(pamh, pam_err)) != PAM_SUCCESS) \
 105                 syslog(LOG_ERR|LOG_AUTH, "pam_end(): %s", pam_strerror(pamh, pam_err)); \
 106 }
 107
 108 int     keepalive = 1;
 109 int     log_success;            /* If TRUE, log all successful accesses */
 110 int     sent_null;
 111 int     no_delay;
 112
 113 void     doit(struct sockaddr *);
 114 static void      rshd_errx(int, const char *, ...) __printf0like(2, 3);
 115 void     getstr(char *, int, const char *);
 116 int      local_domain(char *);
 117 char    *topdomain(char *);
 118 void     usage(void);
 119
 120 char     slash[] = "/";
 121 char     bshell[] = _PATH_BSHELL;
 122
 123 #define OPTIONS "aDLln"
 124
 125 int
 126 main(int argc, char *argv[])
 127 {
 128         extern int __check_rhosts_file;
 129         struct linger linger;
 130         socklen_t fromlen;
 131         int ch, on = 1;
 132         struct sockaddr_storage from;
 133
 134         openlog("rshd", LOG_PID | LOG_ODELAY, LOG_DAEMON);
 135
 136         opterr = 0;
 137         while ((ch = getopt(argc, argv, OPTIONS)) != -1)
 138                 switch (ch) {
 139                 case 'a':
 140                         /* ignored for compatibility */
 141                         break;
 142                 case 'l':
 143                         __check_rhosts_file = 0;
 144                         break;
 145                 case 'n':
 146                         keepalive = 0;
 147                         break;
 148                 case 'D':
 149                         no_delay = 1;
 150                         break;
 151                 case 'L':
 152                         log_success = 1;
 153                         break;
 154                 case '?':
 155                 default:
 156                         usage();
 157                         break;
 158                 }
 159
 160         argc -= optind;
 161         argv += optind;
 162
 163         fromlen = sizeof (from);
 164         if (getpeername(0, (struct sockaddr *)&from, &fromlen) < 0) {
 165                 syslog(LOG_ERR, "getpeername: %m");
 166                 exit(1);
 167         }
 168         if (keepalive &&
 169             setsockopt(0, SOL_SOCKET, SO_KEEPALIVE, (char *)&on,
 170             sizeof(on)) < 0)
 171                 syslog(LOG_WARNING, "setsockopt (SO_KEEPALIVE): %m");
 172         linger.l_onoff = 1;
 173         linger.l_linger = 60;                   /* XXX */
 174         if (setsockopt(0, SOL_SOCKET, SO_LINGER, (char *)&linger,
 175             sizeof (linger)) < 0)
 176                 syslog(LOG_WARNING, "setsockopt (SO_LINGER): %m");
 177         if (no_delay &&
 178             setsockopt(0, IPPROTO_TCP, TCP_NODELAY, &on, sizeof(on)) < 0)
 179                 syslog(LOG_WARNING, "setsockopt (TCP_NODELAY): %m");
 180         doit((struct sockaddr *)&from);
 181         /* NOTREACHED */
 182         return(0);
 183 }
 184
 185 extern char **environ;
 186
 187 void
 188 doit(struct sockaddr *fromp)
 189 {
 190         extern char *__rcmd_errstr;     /* syslog hook from libc/net/rcmd.c. */
 191         struct passwd *pwd;
 192         u_short port;
 193         fd_set ready, readfrom;
 194         int cc, fd, nfd, pv[2], pid, s;
 195         int one = 1;
 196         const char *cp, *errorstr;
 197         char sig, buf[BUFSIZ];
 198         char *cmdbuf, luser[16], ruser[16];
 199         char rhost[2 * MAXHOSTNAMELEN + 1];
 200         char numericname[INET6_ADDRSTRLEN];
 201         int af, srcport;
 202         int maxcmdlen;
 203         login_cap_t *lc;
 204
 205         maxcmdlen = (int)sysconf(_SC_ARG_MAX);
 206         if (maxcmdlen <= 0 || (cmdbuf = malloc(maxcmdlen)) == NULL)
 207                 exit(1);
 208
 209         (void) signal(SIGINT, SIG_DFL);
 210         (void) signal(SIGQUIT, SIG_DFL);
 211         (void) signal(SIGTERM, SIG_DFL);
 212         af = fromp->sa_family;
 213         srcport = ntohs(*((in_port_t *)&fromp->sa_data));
 214         if (af == AF_INET) {
 215                 inet_ntop(af, &((struct sockaddr_in *)fromp)->sin_addr,
 216                     numericname, sizeof numericname);
 217         } else if (af == AF_INET6) {
 218                 inet_ntop(af, &((struct sockaddr_in6 *)fromp)->sin6_addr,
 219                     numericname, sizeof numericname);
 220         } else {
 221                 syslog(LOG_ERR, "malformed \"from\" address (af %d)", af);
 222                 exit(1);
 223         }
 224 #ifdef IP_OPTIONS
 225         if (af == AF_INET) {
 226                 u_char optbuf[BUFSIZ/3];
 227                 socklen_t optsize = sizeof(optbuf), ipproto, i;
 228                 struct protoent *ip;
 229
 230                 if ((ip = getprotobyname("ip")) != NULL)
 231                         ipproto = ip->p_proto;
 232                 else
 233                         ipproto = IPPROTO_IP;
 234                 if (!getsockopt(0, ipproto, IP_OPTIONS, optbuf, &optsize) &&
 235                     optsize != 0) {
 236                         for (i = 0; i < optsize; ) {
 237                                 u_char c = optbuf[i];
 238                                 if (c == IPOPT_LSRR || c == IPOPT_SSRR) {
 239                                         syslog(LOG_NOTICE,
 240                                             "connection refused from %s with IP option %s",
 241                                             numericname,
 242                                             c == IPOPT_LSRR ? "LSRR" : "SSRR");
 243                                         exit(1);
 244                                 }
 245                                 if (c == IPOPT_EOL)
 246                                         break;
 247                                 i += (c == IPOPT_NOP) ? 1 : optbuf[i+1];
 248                         }
 249                 }
 250         }
 251 #endif
 252
 253         if (srcport >= IPPORT_RESERVED ||
 254             srcport < IPPORT_RESERVED/2) {
 255                 syslog(LOG_NOTICE|LOG_AUTH,
 256                     "connection from %s on illegal port %u",
 257                     numericname,
 258                     srcport);
 259                 exit(1);
 260         }
 261
 262         (void) alarm(60);
 263         port = 0;
 264         s = 0;          /* not set or used if port == 0 */
 265         for (;;) {
 266                 char c;
 267                 if ((cc = read(STDIN_FILENO, &c, 1)) != 1) {
 268                         if (cc < 0)
 269                                 syslog(LOG_NOTICE, "read: %m");
 270                         shutdown(0, SHUT_RDWR);
 271                         exit(1);
 272                 }
 273                 if (c == 0)
 274                         break;
 275                 port = port * 10 + c - '0';
 276         }
 277
 278         (void) alarm(0);
 279         if (port != 0) {
 280                 int lport = IPPORT_RESERVED - 1;
 281                 s = rresvport_af(&lport, af);
 282                 if (s < 0) {
 283                         syslog(LOG_ERR, "can't get stderr port: %m");
 284                         exit(1);
 285                 }
 286                 if (port >= IPPORT_RESERVED ||
 287                     port < IPPORT_RESERVED/2) {
 288                         syslog(LOG_NOTICE|LOG_AUTH,
 289                             "2nd socket from %s on unreserved port %u",
 290                             numericname,
 291                             port);
 292                         exit(1);
 293                 }
 294                 *((in_port_t *)&fromp->sa_data) = htons(port);
 295                 if (connect(s, fromp, fromp->sa_len) < 0) {
 296                         syslog(LOG_INFO, "connect second port %d: %m", port);
 297                         exit(1);
 298                 }
 299         }
 300
 301         errorstr = NULL;
 302         realhostname_sa(rhost, sizeof(rhost) - 1, fromp, fromp->sa_len);
 303         rhost[sizeof(rhost) - 1] = '\0';
 304         /* XXX truncation! */
 305
 306         (void) alarm(60);
 307         getstr(ruser, sizeof(ruser), "ruser");
 308         getstr(luser, sizeof(luser), "luser");
 309         getstr(cmdbuf, maxcmdlen, "command");
 310         (void) alarm(0);
 311
 312         pam_err = pam_start("rsh", luser, &pamc, &pamh);
 313         if (pam_err != PAM_SUCCESS) {
 314                 syslog(LOG_ERR|LOG_AUTH, "pam_start(): %s",
 315                     pam_strerror(pamh, pam_err));
 316                 rshd_errx(1, "Login incorrect.");
 317         }
 318
 319         if ((pam_err = pam_set_item(pamh, PAM_RUSER, ruser)) != PAM_SUCCESS ||
 320             (pam_err = pam_set_item(pamh, PAM_RHOST, rhost)) != PAM_SUCCESS) {
 321                 syslog(LOG_ERR|LOG_AUTH, "pam_set_item(): %s",
 322                     pam_strerror(pamh, pam_err));
 323                 rshd_errx(1, "Login incorrect.");
 324         }
 325
 326         pam_err = pam_authenticate(pamh, 0);
 327         if (pam_err == PAM_SUCCESS) {
 328                 if ((pam_err = pam_get_user(pamh, &cp, NULL)) == PAM_SUCCESS) {
 329                         strncpy(luser, cp, sizeof(luser));
 330                         luser[sizeof(luser) - 1] = '\0';
 331                         /* XXX truncation! */
 332                 }
 333                 pam_err = pam_acct_mgmt(pamh, 0);
 334         }
 335         if (pam_err != PAM_SUCCESS) {
 336                 syslog(LOG_INFO|LOG_AUTH,
 337                     "%s@%s as %s: permission denied (%s). cmd='%.80s'",
 338                     ruser, rhost, luser, pam_strerror(pamh, pam_err), cmdbuf);
 339                 rshd_errx(1, "Login incorrect.");
 340         }
 341
 342         setpwent();
 343         pwd = getpwnam(luser);
 344         if (pwd == NULL) {
 345                 syslog(LOG_INFO|LOG_AUTH,
 346                     "%s@%s as %s: unknown login. cmd='%.80s'",
 347                     ruser, rhost, luser, cmdbuf);
 348                 if (errorstr == NULL)
 349                         errorstr = "Login incorrect.";
 350                 rshd_errx(1, errorstr, rhost);
 351         }
 352
 353         lc = login_getpwclass(pwd);
 354         if (pwd->pw_uid)
 355                 auth_checknologin(lc);
 356
 357         if (chdir(pwd->pw_dir) < 0) {
 358                 if (chdir("/") < 0 ||
 359                     login_getcapbool(lc, "requirehome", !!pwd->pw_uid)) {
 360                         syslog(LOG_INFO|LOG_AUTH,
 361                         "%s@%s as %s: no home directory. cmd='%.80s'",
 362                         ruser, rhost, luser, cmdbuf);
 363                         rshd_errx(0, "No remote home directory.");
 364                 }
 365                 pwd->pw_dir = slash;
 366         }
 367
 368         if (lc != NULL && fromp->sa_family == AF_INET) {        /*XXX*/
 369                 char    remote_ip[MAXHOSTNAMELEN];
 370
 371                 strncpy(remote_ip, numericname,
 372                         sizeof(remote_ip) - 1);
 373                 remote_ip[sizeof(remote_ip) - 1] = 0;
 374                 /* XXX truncation! */
 375                 if (!auth_hostok(lc, rhost, remote_ip)) {
 376                         syslog(LOG_INFO|LOG_AUTH,
 377                             "%s@%s as %s: permission denied (%s). cmd='%.80s'",
 378                             ruser, rhost, luser, __rcmd_errstr,
 379                             cmdbuf);
 380                         rshd_errx(1, "Login incorrect.");
 381                 }
 382                 if (!auth_timeok(lc, time(NULL)))
 383                         rshd_errx(1, "Logins not available right now");
 384         }
 385
 386         /*
 387          * PAM modules might add supplementary groups in
 388          * pam_setcred(), so initialize them first.
 389          * But we need to open the session as root.
 390          */
 391         if (setusercontext(lc, pwd, pwd->pw_uid, LOGIN_SETGROUP) != 0) {
 392                 syslog(LOG_ERR, "setusercontext: %m");
 393                 exit(1);
 394         }
 395
 396         if ((pam_err = pam_open_session(pamh, 0)) != PAM_SUCCESS) {
 397                 syslog(LOG_ERR, "pam_open_session: %s", pam_strerror(pamh, pam_err));
 398         } else if ((pam_err = pam_setcred(pamh, PAM_ESTABLISH_CRED)) != PAM_SUCCESS) {
 399                 syslog(LOG_ERR, "pam_setcred: %s", pam_strerror(pamh, pam_err));
 400         }
 401
 402         (void) write(STDERR_FILENO, "\0", 1);
 403         sent_null = 1;
 404
 405         if (port) {
 406                 if (pipe(pv) < 0)
 407                         rshd_errx(1, "Can't make pipe.");
 408                 pid = fork();
 409                 if (pid == -1)
 410                         rshd_errx(1, "Can't fork; try again.");
 411                 if (pid) {
 412                         (void) close(0);
 413                         (void) close(1);
 414                         (void) close(2);
 415                         (void) close(pv[1]);
 416
 417                         FD_ZERO(&readfrom);
 418                         FD_SET(s, &readfrom);
 419                         FD_SET(pv[0], &readfrom);
 420                         if (pv[0] > s)
 421                                 nfd = pv[0];
 422                         else
 423                                 nfd = s;
 424                                 ioctl(pv[0], FIONBIO, (char *)&one);
 425
 426                         /* should set s nbio! */
 427                         nfd++;
 428                         do {
 429                                 ready = readfrom;
 430                                 if (select(nfd, &ready, (fd_set *)0,
 431                                   (fd_set *)0, (struct timeval *)0) < 0)
 432                                         break;
 433                                 if (FD_ISSET(s, &ready)) {
 434                                         int     ret;
 435                                                 ret = read(s, &sig, 1);
 436                                 if (ret <= 0)
 437                                         FD_CLR(s, &readfrom);
 438                                 else
 439                                         killpg(pid, sig);
 440                                 }
 441                                 if (FD_ISSET(pv[0], &ready)) {
 442                                         errno = 0;
 443                                         cc = read(pv[0], buf, sizeof(buf));
 444                                         if (cc <= 0) {
 445                                                 shutdown(s, SHUT_RDWR);
 446                                                 FD_CLR(pv[0], &readfrom);
 447                                         } else {
 448                                                 (void)write(s, buf, cc);
 449                                         }
 450                                 }
 451
 452                         } while (FD_ISSET(s, &readfrom) ||
 453                             FD_ISSET(pv[0], &readfrom));
 454                         PAM_END;
 455                         exit(0);
 456                 }
 457                 (void) close(s);
 458                 (void) close(pv[0]);
 459                 dup2(pv[1], 2);
 460                 close(pv[1]);
 461         }
 462         else {
 463                 pid = fork();
 464                 if (pid == -1)
 465                         rshd_errx(1, "Can't fork; try again.");
 466                 if (pid) {
 467                         /* Parent. */
 468                         while (wait(NULL) > 0 || errno == EINTR)
 469                                 /* nothing */ ;
 470                         PAM_END;
 471                         exit(0);
 472                 }
 473         }
 474
 475         for (fd = getdtablesize(); fd > 2; fd--)
 476                 (void) close(fd);
 477         if (setsid() == -1)
 478                 syslog(LOG_ERR, "setsid() failed: %m");
 479         if (setlogin(pwd->pw_name) < 0)
 480                 syslog(LOG_ERR, "setlogin() failed: %m");
 481
 482         if (*pwd->pw_shell == '\0')
 483                 pwd->pw_shell = bshell;
 484         (void) pam_setenv(pamh, "HOME", pwd->pw_dir, 1);
 485         (void) pam_setenv(pamh, "SHELL", pwd->pw_shell, 1);
 486         (void) pam_setenv(pamh, "USER", pwd->pw_name, 1);
 487         (void) pam_setenv(pamh, "PATH", _PATH_DEFPATH, 1);
 488         environ = pam_getenvlist(pamh);
 489         (void) pam_end(pamh, pam_err);
 490         cp = strrchr(pwd->pw_shell, '/');
 491         if (cp)
 492                 cp++;
 493         else
 494                 cp = pwd->pw_shell;
 495
 496         if (setusercontext(lc, pwd, pwd->pw_uid,
 497                 LOGIN_SETALL & ~LOGIN_SETGROUP) < 0) {
 498                 syslog(LOG_ERR, "setusercontext(): %m");
 499                 exit(1);
 500         }
 501         login_close(lc);
 502         endpwent();
 503         if (log_success || pwd->pw_uid == 0) {
 504                     syslog(LOG_INFO|LOG_AUTH, "%s@%s as %s: cmd='%.80s'",
 505                         ruser, rhost, luser, cmdbuf);
 506         }
 507         execl(pwd->pw_shell, cp, "-c", cmdbuf, (char *)NULL);
 508         err(1, "%s", pwd->pw_shell);
 509         exit(1);
 510 }
 511
 512 /*
 513  * Report error to client.  Note: can't be used until second socket has
 514  * connected to client, or older clients will hang waiting for that
 515  * connection first.
 516  */
 517
 518 static void
 519 rshd_errx(int errcode, const char *fmt, ...)
 520 {
 521         va_list ap;
 522
 523         va_start(ap, fmt);
 524
 525         if (sent_null == 0)
 526                 write(STDERR_FILENO, "\1", 1);
 527
 528         verrx(errcode, fmt, ap);
 529         /* NOTREACHED */
 530 }
 531
 532 void
 533 getstr(char *buf, int cnt, const char *error)
 534 {
 535         char c;
 536
 537         do {
 538                 if (read(STDIN_FILENO, &c, 1) != 1)
 539                         exit(1);
 540                 *buf++ = c;
 541                 if (--cnt == 0)
 542                         rshd_errx(1, "%s too long", error);
 543         } while (c != 0);
 544 }
 545
 546 /*
 547  * Check whether host h is in our local domain,
 548  * defined as sharing the last two components of the domain part,
 549  * or the entire domain part if the local domain has only one component.
 550  * If either name is unqualified (contains no '.'),
 551  * assume that the host is local, as it will be
 552  * interpreted as such.
 553  */
 554 int
 555 local_domain(char *h)
 556 {
 557         char localhost[MAXHOSTNAMELEN];
 558         char *p1, *p2;
 559
 560         localhost[0] = 0;
 561         (void) gethostname(localhost, sizeof(localhost) - 1);
 562         localhost[sizeof(localhost) - 1] = '\0';
 563         /* XXX truncation! */
 564         p1 = topdomain(localhost);
 565         p2 = topdomain(h);
 566         if (p1 == NULL || p2 == NULL || !strcasecmp(p1, p2))
 567                 return (1);
 568         return (0);
 569 }
 570
 571 char *
 572 topdomain(char *h)
 573 {
 574         char *p, *maybe = NULL;
 575         int dots = 0;
 576
 577         for (p = h + strlen(h); p >= h; p--) {
 578                 if (*p == '.') {
 579                         if (++dots == 2)
 580                                 return (p);
 581                         maybe = p;
 582                 }
 583         }
 584         return (maybe);
 585 }
 586
 587 void
 588 usage(void)
 589 {
 590
 591         syslog(LOG_ERR, "usage: rshd [-%s]", OPTIONS);
 592         exit(2);
 593 }