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 "alnDL"
 124
 125 int
 126 main(int argc, char *argv[])
 127 {
 128         extern int __check_rhosts_file;
 129         struct linger linger;
 130         int ch, on = 1, fromlen;
 131         struct sockaddr_storage from;
 132
 133         openlog("rshd", LOG_PID | LOG_ODELAY, LOG_DAEMON);
 134
 135         opterr = 0;
 136         while ((ch = getopt(argc, argv, OPTIONS)) != -1)
 137                 switch (ch) {
 138                 case 'a':
 139                         /* ignored for compatibility */
 140                         break;
 141                 case 'l':
 142                         __check_rhosts_file = 0;
 143                         break;
 144                 case 'n':
 145                         keepalive = 0;
 146                         break;
 147                 case 'D':
 148                         no_delay = 1;
 149                         break;
 150                 case 'L':
 151                         log_success = 1;
 152                         break;
 153                 case '?':
 154                 default:
 155                         usage();
 156                         break;
 157                 }
 158
 159         argc -= optind;
 160         argv += optind;
 161
 162         fromlen = sizeof (from);
 163         if (getpeername(0, (struct sockaddr *)&from, &fromlen) < 0) {
 164                 syslog(LOG_ERR, "getpeername: %m");
 165                 exit(1);
 166         }
 167         if (keepalive &&
 168             setsockopt(0, SOL_SOCKET, SO_KEEPALIVE, (char *)&on,
 169             sizeof(on)) < 0)
 170                 syslog(LOG_WARNING, "setsockopt (SO_KEEPALIVE): %m");
 171         linger.l_onoff = 1;
 172         linger.l_linger = 60;                   /* XXX */
 173         if (setsockopt(0, SOL_SOCKET, SO_LINGER, (char *)&linger,
 174             sizeof (linger)) < 0)
 175                 syslog(LOG_WARNING, "setsockopt (SO_LINGER): %m");
 176         if (no_delay &&
 177             setsockopt(0, IPPROTO_TCP, TCP_NODELAY, &on, sizeof(on)) < 0)
 178                 syslog(LOG_WARNING, "setsockopt (TCP_NODELAY): %m");
 179         doit((struct sockaddr *)&from);
 180         /* NOTREACHED */
 181         return(0);
 182 }
 183
 184 extern char **environ;
 185
 186 void
 187 doit(struct sockaddr *fromp)
 188 {
 189         extern char *__rcmd_errstr;     /* syslog hook from libc/net/rcmd.c. */
 190         struct passwd *pwd;
 191         u_short port;
 192         fd_set ready, readfrom;
 193         int cc, fd, nfd, pv[2], pid, s;
 194         int one = 1;
 195         const char *cp, *errorstr;
 196         char sig, buf[BUFSIZ];
 197         char cmdbuf[NCARGS+1], luser[16], ruser[16];
 198         char rhost[2 * MAXHOSTNAMELEN + 1];
 199         char numericname[INET6_ADDRSTRLEN];
 200         int af, srcport;
 201         login_cap_t *lc;
 202
 203         (void) signal(SIGINT, SIG_DFL);
 204         (void) signal(SIGQUIT, SIG_DFL);
 205         (void) signal(SIGTERM, SIG_DFL);
 206         af = fromp->sa_family;
 207         srcport = ntohs(*((in_port_t *)&fromp->sa_data));
 208         if (af == AF_INET) {
 209                 inet_ntop(af, &((struct sockaddr_in *)fromp)->sin_addr,
 210                     numericname, sizeof numericname);
 211         } else if (af == AF_INET6) {
 212                 inet_ntop(af, &((struct sockaddr_in6 *)fromp)->sin6_addr,
 213                     numericname, sizeof numericname);
 214         } else {
 215                 syslog(LOG_ERR, "malformed \"from\" address (af %d)", af);
 216                 exit(1);
 217         }
 218 #ifdef IP_OPTIONS
 219         if (af == AF_INET) {
 220                 u_char optbuf[BUFSIZ/3];
 221                 int optsize = sizeof(optbuf), ipproto, i;
 222                 struct protoent *ip;
 223
 224                 if ((ip = getprotobyname("ip")) != NULL)
 225                         ipproto = ip->p_proto;
 226                 else
 227                         ipproto = IPPROTO_IP;
 228                 if (!getsockopt(0, ipproto, IP_OPTIONS, optbuf, &optsize) &&
 229                     optsize != 0) {
 230                         for (i = 0; i < optsize; ) {
 231                                 u_char c = optbuf[i];
 232                                 if (c == IPOPT_LSRR || c == IPOPT_SSRR) {
 233                                         syslog(LOG_NOTICE,
 234                                             "connection refused from %s with IP option %s",
 235                                             numericname,
 236                                             c == IPOPT_LSRR ? "LSRR" : "SSRR");
 237                                         exit(1);
 238                                 }
 239                                 if (c == IPOPT_EOL)
 240                                         break;
 241                                 i += (c == IPOPT_NOP) ? 1 : optbuf[i+1];
 242                         }
 243                 }
 244         }
 245 #endif
 246
 247         if (srcport >= IPPORT_RESERVED ||
 248             srcport < IPPORT_RESERVED/2) {
 249                 syslog(LOG_NOTICE|LOG_AUTH,
 250                     "connection from %s on illegal port %u",
 251                     numericname,
 252                     srcport);
 253                 exit(1);
 254         }
 255
 256         (void) alarm(60);
 257         port = 0;
 258         s = 0;          /* not set or used if port == 0 */
 259         for (;;) {
 260                 char c;
 261                 if ((cc = read(STDIN_FILENO, &c, 1)) != 1) {
 262                         if (cc < 0)
 263                                 syslog(LOG_NOTICE, "read: %m");
 264                         shutdown(0, 1+1);
 265                         exit(1);
 266                 }
 267                 if (c == 0)
 268                         break;
 269                 port = port * 10 + c - '0';
 270         }
 271
 272         (void) alarm(0);
 273         if (port != 0) {
 274                 int lport = IPPORT_RESERVED - 1;
 275                 s = rresvport_af(&lport, af);
 276                 if (s < 0) {
 277                         syslog(LOG_ERR, "can't get stderr port: %m");
 278                         exit(1);
 279                 }
 280                 if (port >= IPPORT_RESERVED ||
 281                     port < IPPORT_RESERVED/2) {
 282                         syslog(LOG_NOTICE|LOG_AUTH,
 283                             "2nd socket from %s on unreserved port %u",
 284                             numericname,
 285                             port);
 286                         exit(1);
 287                 }
 288                 *((in_port_t *)&fromp->sa_data) = htons(port);
 289                 if (connect(s, fromp, fromp->sa_len) < 0) {
 290                         syslog(LOG_INFO, "connect second port %d: %m", port);
 291                         exit(1);
 292                 }
 293         }
 294
 295         errorstr = NULL;
 296         realhostname_sa(rhost, sizeof(rhost) - 1, fromp, fromp->sa_len);
 297         rhost[sizeof(rhost) - 1] = '\0';
 298         /* XXX truncation! */
 299
 300         (void) alarm(60);
 301         getstr(ruser, sizeof(ruser), "ruser");
 302         getstr(luser, sizeof(luser), "luser");
 303         getstr(cmdbuf, sizeof(cmdbuf), "command");
 304         (void) alarm(0);
 305
 306         pam_err = pam_start("rsh", luser, &pamc, &pamh);
 307         if (pam_err != PAM_SUCCESS) {
 308                 syslog(LOG_ERR|LOG_AUTH, "pam_start(): %s",
 309                     pam_strerror(pamh, pam_err));
 310                 rshd_errx(1, "Login incorrect.");
 311         }
 312
 313         if ((pam_err = pam_set_item(pamh, PAM_RUSER, ruser)) != PAM_SUCCESS ||
 314             (pam_err = pam_set_item(pamh, PAM_RHOST, rhost) != PAM_SUCCESS)) {
 315                 syslog(LOG_ERR|LOG_AUTH, "pam_set_item(): %s",
 316                     pam_strerror(pamh, pam_err));
 317                 rshd_errx(1, "Login incorrect.");
 318         }
 319
 320         pam_err = pam_authenticate(pamh, 0);
 321         if (pam_err == PAM_SUCCESS) {
 322                 if ((pam_err = pam_get_user(pamh, &cp, NULL)) == PAM_SUCCESS) {
 323                         strncpy(luser, cp, sizeof(luser));
 324                         luser[sizeof(luser) - 1] = '\0';
 325                         /* XXX truncation! */
 326                 }
 327                 pam_err = pam_acct_mgmt(pamh, 0);
 328         }
 329         if (pam_err != PAM_SUCCESS) {
 330                 syslog(LOG_INFO|LOG_AUTH,
 331                     "%s@%s as %s: permission denied (%s). cmd='%.80s'",
 332                     ruser, rhost, luser, pam_strerror(pamh, pam_err), cmdbuf);
 333                 rshd_errx(1, "Login incorrect.");
 334         }
 335
 336         setpwent();
 337         pwd = getpwnam(luser);
 338         if (pwd == NULL) {
 339                 syslog(LOG_INFO|LOG_AUTH,
 340                     "%s@%s as %s: unknown login. cmd='%.80s'",
 341                     ruser, rhost, luser, cmdbuf);
 342                 if (errorstr == NULL)
 343                         errorstr = "Login incorrect.";
 344                 rshd_errx(1, errorstr, rhost);
 345         }
 346
 347         lc = login_getpwclass(pwd);
 348         if (pwd->pw_uid)
 349                 auth_checknologin(lc);
 350
 351         if (chdir(pwd->pw_dir) < 0) {
 352                 if (chdir("/") < 0 ||
 353                     login_getcapbool(lc, "requirehome", !!pwd->pw_uid)) {
 354                         syslog(LOG_INFO|LOG_AUTH,
 355                         "%s@%s as %s: no home directory. cmd='%.80s'",
 356                         ruser, rhost, luser, cmdbuf);
 357                         rshd_errx(0, "No remote home directory.");
 358                 }
 359                 pwd->pw_dir = slash;
 360         }
 361
 362         if (lc != NULL && fromp->sa_family == AF_INET) {        /*XXX*/
 363                 char    remote_ip[MAXHOSTNAMELEN];
 364
 365                 strncpy(remote_ip, numericname,
 366                         sizeof(remote_ip) - 1);
 367                 remote_ip[sizeof(remote_ip) - 1] = 0;
 368                 /* XXX truncation! */
 369                 if (!auth_hostok(lc, rhost, remote_ip)) {
 370                         syslog(LOG_INFO|LOG_AUTH,
 371                             "%s@%s as %s: permission denied (%s). cmd='%.80s'",
 372                             ruser, rhost, luser, __rcmd_errstr,
 373                             cmdbuf);
 374                         rshd_errx(1, "Login incorrect.");
 375                 }
 376                 if (!auth_timeok(lc, time(NULL)))
 377                         rshd_errx(1, "Logins not available right now");
 378         }
 379
 380         /*
 381          * PAM modules might add supplementary groups in
 382          * pam_setcred(), so initialize them first.
 383          * But we need to open the session as root.
 384          */
 385         if (setusercontext(lc, pwd, pwd->pw_uid, LOGIN_SETGROUP) != 0) {
 386                 syslog(LOG_ERR, "setusercontext: %m");
 387                 exit(1);
 388         }
 389
 390         if ((pam_err = pam_open_session(pamh, 0)) != PAM_SUCCESS) {
 391                 syslog(LOG_ERR, "pam_open_session: %s", pam_strerror(pamh, pam_err));
 392         } else if ((pam_err = pam_setcred(pamh, PAM_ESTABLISH_CRED)) != PAM_SUCCESS) {
 393                 syslog(LOG_ERR, "pam_setcred: %s", pam_strerror(pamh, pam_err));
 394         }
 395
 396         (void) write(STDERR_FILENO, "\0", 1);
 397         sent_null = 1;
 398
 399         if (port) {
 400                 if (pipe(pv) < 0)
 401                         rshd_errx(1, "Can't make pipe.");
 402                 pid = fork();
 403                 if (pid == -1)
 404                         rshd_errx(1, "Can't fork; try again.");
 405                 if (pid) {
 406                         (void) close(0);
 407                         (void) close(1);
 408                         (void) close(2);
 409                         (void) close(pv[1]);
 410
 411                         FD_ZERO(&readfrom);
 412                         FD_SET(s, &readfrom);
 413                         FD_SET(pv[0], &readfrom);
 414                         if (pv[0] > s)
 415                                 nfd = pv[0];
 416                         else
 417                                 nfd = s;
 418                                 ioctl(pv[0], FIONBIO, (char *)&one);
 419
 420                         /* should set s nbio! */
 421                         nfd++;
 422                         do {
 423                                 ready = readfrom;
 424                                 if (select(nfd, &ready, (fd_set *)0,
 425                                   (fd_set *)0, (struct timeval *)0) < 0)
 426                                         break;
 427                                 if (FD_ISSET(s, &ready)) {
 428                                         int     ret;
 429                                                 ret = read(s, &sig, 1);
 430                                 if (ret <= 0)
 431                                         FD_CLR(s, &readfrom);
 432                                 else
 433                                         killpg(pid, sig);
 434                                 }
 435                                 if (FD_ISSET(pv[0], &ready)) {
 436                                         errno = 0;
 437                                         cc = read(pv[0], buf, sizeof(buf));
 438                                         if (cc <= 0) {
 439                                                 shutdown(s, 1+1);
 440                                                 FD_CLR(pv[0], &readfrom);
 441                                         } else {
 442                                                 (void)write(s, buf, cc);
 443                                         }
 444                                 }
 445
 446                         } while (FD_ISSET(s, &readfrom) ||
 447                             FD_ISSET(pv[0], &readfrom));
 448                         PAM_END;
 449                         exit(0);
 450                 }
 451                 (void) close(s);
 452                 (void) close(pv[0]);
 453                 dup2(pv[1], 2);
 454                 close(pv[1]);
 455         }
 456         else {
 457                 pid = fork();
 458                 if (pid == -1)
 459                         rshd_errx(1, "Can't fork; try again.");
 460                 if (pid) {
 461                         /* Parent. */
 462                         while (wait(NULL) > 0 || errno == EINTR)
 463                                 /* nothing */ ;
 464                         PAM_END;
 465                         exit(0);
 466                 }
 467         }
 468
 469         for (fd = getdtablesize(); fd > 2; fd--)
 470                 (void) close(fd);
 471         if (setsid() == -1)
 472                 syslog(LOG_ERR, "setsid() failed: %m");
 473         if (setlogin(pwd->pw_name) < 0)
 474                 syslog(LOG_ERR, "setlogin() failed: %m");
 475
 476         if (*pwd->pw_shell == '\0')
 477                 pwd->pw_shell = bshell;
 478         (void) pam_setenv(pamh, "HOME", pwd->pw_dir, 1);
 479         (void) pam_setenv(pamh, "SHELL", pwd->pw_shell, 1);
 480         (void) pam_setenv(pamh, "USER", pwd->pw_name, 1);
 481         (void) pam_setenv(pamh, "PATH", _PATH_DEFPATH, 1);
 482         environ = pam_getenvlist(pamh);
 483         (void) pam_end(pamh, pam_err);
 484         cp = strrchr(pwd->pw_shell, '/');
 485         if (cp)
 486                 cp++;
 487         else
 488                 cp = pwd->pw_shell;
 489
 490         if (setusercontext(lc, pwd, pwd->pw_uid,
 491                 LOGIN_SETALL & ~LOGIN_SETGROUP) < 0) {
 492                 syslog(LOG_ERR, "setusercontext(): %m");
 493                 exit(1);
 494         }
 495         login_close(lc);
 496         endpwent();
 497         if (log_success || pwd->pw_uid == 0) {
 498                     syslog(LOG_INFO|LOG_AUTH, "%s@%s as %s: cmd='%.80s'",
 499                         ruser, rhost, luser, cmdbuf);
 500         }
 501         execl(pwd->pw_shell, cp, "-c", cmdbuf, (char *)NULL);
 502         err(1, "%s", pwd->pw_shell);
 503         exit(1);
 504 }
 505
 506 /*
 507  * Report error to client.  Note: can't be used until second socket has
 508  * connected to client, or older clients will hang waiting for that
 509  * connection first.
 510  */
 511
 512 static void
 513 rshd_errx(int errcode, const char *fmt, ...)
 514 {
 515         va_list ap;
 516
 517         va_start(ap, fmt);
 518
 519         if (sent_null == 0)
 520                 write(STDERR_FILENO, "\1", 1);
 521
 522         verrx(errcode, fmt, ap);
 523         /* NOTREACHED */
 524 }
 525
 526 void
 527 getstr(char *buf, int cnt, const char *error)
 528 {
 529         char c;
 530
 531         do {
 532                 if (read(STDIN_FILENO, &c, 1) != 1)
 533                         exit(1);
 534                 *buf++ = c;
 535                 if (--cnt == 0)
 536                         rshd_errx(1, "%s too long", error);
 537         } while (c != 0);
 538 }
 539
 540 /*
 541  * Check whether host h is in our local domain,
 542  * defined as sharing the last two components of the domain part,
 543  * or the entire domain part if the local domain has only one component.
 544  * If either name is unqualified (contains no '.'),
 545  * assume that the host is local, as it will be
 546  * interpreted as such.
 547  */
 548 int
 549 local_domain(char *h)
 550 {
 551         char localhost[MAXHOSTNAMELEN];
 552         char *p1, *p2;
 553
 554         localhost[0] = 0;
 555         (void) gethostname(localhost, sizeof(localhost) - 1);
 556         localhost[sizeof(localhost) - 1] = '\0';
 557         /* XXX truncation! */
 558         p1 = topdomain(localhost);
 559         p2 = topdomain(h);
 560         if (p1 == NULL || p2 == NULL || !strcasecmp(p1, p2))
 561                 return (1);
 562         return (0);
 563 }
 564
 565 char *
 566 topdomain(char *h)
 567 {
 568         char *p, *maybe = NULL;
 569         int dots = 0;
 570
 571         for (p = h + strlen(h); p >= h; p--) {
 572                 if (*p == '.') {
 573                         if (++dots == 2)
 574                                 return (p);
 575                         maybe = p;
 576                 }
 577         }
 578         return (maybe);
 579 }
 580
 581 void
 582 usage(void)
 583 {
 584
 585         syslog(LOG_ERR, "usage: rshd [-%s]", OPTIONS);
 586         exit(2);
 587 }