1 /* 2 * Copyright (c) 1995, 1996, 1998 Theo de Raadt. All rights reserved. 3 * Copyright (c) 1983, 1993, 1994 4 * The Regents of the University of California. All rights reserved. 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: 9 * 1. Redistributions of source code must retain the above copyright 10 * notice, this list of conditions and the following disclaimer. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 3. Neither the name of the University nor the names of its contributors 15 * may be used to endorse or promote products derived from this software 16 * without specific prior written permission. 17 * 18 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 19 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 20 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 21 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 22 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28 * SUCH DAMAGE. 29 */ 30 31 #if defined(LIBC_SCCS) && !defined(lint) 32 static char *rcsid = "$OpenBSD: rcmd.c,v 1.52 2005/03/25 13:24:12 otto Exp $"; 33 #endif /* LIBC_SCCS and not lint */ 34 35 #include <sys/param.h> 36 #include <sys/socket.h> 37 #include <sys/stat.h> 38 39 #include <netinet/in.h> 40 #include <arpa/inet.h> 41 42 #include <signal.h> 43 #include <fcntl.h> 44 #include <netdb.h> 45 #include <unistd.h> 46 #include <pwd.h> 47 #include <errno.h> 48 #include <stdio.h> 49 #include <ctype.h> 50 #include <string.h> 51 #include <syslog.h> 52 #include <stdlib.h> 53 #include <netgroup.h> 54 55 int __ivaliduser(FILE *, in_addr_t, const char *, const char *); 56 int __ivaliduser_sa(FILE *, struct sockaddr *, socklen_t, 57 const char *, const char *); 58 static int __icheckhost(struct sockaddr *, socklen_t, const char *); 59 static char *__gethostloop(struct sockaddr *, socklen_t); 60 61 int 62 rcmd(char **ahost, int rport, const char *locuser, const char *remuser, 63 const char *cmd, int *fd2p) 64 { 65 return rcmd_af(ahost, rport, locuser, remuser, cmd, fd2p, AF_INET); 66 } 67 68 int 69 rcmd_af(char **ahost, int porta, const char *locuser, const char *remuser, 70 const char *cmd, int *fd2p, int af) 71 { 72 static char hbuf[MAXHOSTNAMELEN]; 73 char pbuf[NI_MAXSERV]; 74 struct addrinfo hints, *res, *r; 75 int error; 76 struct sockaddr_storage from; 77 fd_set *readsp = NULL; 78 sigset_t oldmask, mask; 79 pid_t pid; 80 int s, lport, timo; 81 char c, *p; 82 int refused; 83 in_port_t rport = porta; 84 85 /* call rcmdsh() with specified remote shell if appropriate. */ 86 if (!issetugid() && (p = getenv("RSH")) && *p) { 87 struct servent *sp = getservbyname("shell", "tcp"); 88 89 if (sp && sp->s_port == rport) 90 return (rcmdsh(ahost, rport, locuser, remuser, 91 cmd, p)); 92 } 93 94 /* use rsh(1) if non-root and remote port is shell. */ 95 if (geteuid()) { 96 struct servent *sp = getservbyname("shell", "tcp"); 97 98 if (sp && sp->s_port == rport) 99 return (rcmdsh(ahost, rport, locuser, remuser, 100 cmd, NULL)); 101 } 102 103 pid = getpid(); 104 snprintf(pbuf, sizeof(pbuf), "%u", ntohs(rport)); 105 memset(&hints, 0, sizeof(hints)); 106 hints.ai_family = af; 107 hints.ai_socktype = SOCK_STREAM; 108 hints.ai_flags = AI_CANONNAME; 109 error = getaddrinfo(*ahost, pbuf, &hints, &res); 110 if (error) { 111 #if 0 112 warnx("%s: %s", *ahost, gai_strerror(error)); 113 #endif 114 return (-1); 115 } 116 if (res->ai_canonname) { 117 strlcpy(hbuf, res->ai_canonname, sizeof(hbuf)); 118 *ahost = hbuf; 119 } else 120 ; /*XXX*/ 121 122 r = res; 123 refused = 0; 124 sigemptyset(&mask); 125 sigaddset(&mask, SIGURG); 126 oldmask = sigprocmask(SIG_BLOCK, &mask, &oldmask); 127 for (timo = 1, lport = IPPORT_RESERVED - 1;;) { 128 s = rresvport_af(&lport, r->ai_family); 129 if (s < 0) { 130 if (errno == EAGAIN) 131 (void)fprintf(stderr, 132 "rcmd: socket: All ports in use\n"); 133 else 134 (void)fprintf(stderr, "rcmd: socket: %s\n", 135 strerror(errno)); 136 if (r->ai_next) { 137 r = r->ai_next; 138 continue; 139 } else { 140 sigprocmask(SIG_SETMASK, &oldmask, NULL); 141 freeaddrinfo(res); 142 return (-1); 143 } 144 } 145 fcntl(s, F_SETOWN, pid); 146 if (connect(s, r->ai_addr, r->ai_addrlen) >= 0) 147 break; 148 (void)close(s); 149 if (errno == EADDRINUSE) { 150 lport--; 151 continue; 152 } 153 if (errno == ECONNREFUSED) 154 refused++; 155 if (r->ai_next) { 156 int oerrno = errno; 157 char hbuf[NI_MAXHOST]; 158 const int niflags = NI_NUMERICHOST; 159 160 hbuf[0] = '\0'; 161 if (getnameinfo(r->ai_addr, r->ai_addrlen, 162 hbuf, sizeof(hbuf), NULL, 0, niflags) != 0) 163 strlcpy(hbuf, "(invalid)", sizeof hbuf); 164 (void)fprintf(stderr, "connect to address %s: ", hbuf); 165 errno = oerrno; 166 perror(0); 167 r = r->ai_next; 168 hbuf[0] = '\0'; 169 if (getnameinfo(r->ai_addr, r->ai_addrlen, 170 hbuf, sizeof(hbuf), NULL, 0, niflags) != 0) 171 strlcpy(hbuf, "(invalid)", sizeof hbuf); 172 (void)fprintf(stderr, "Trying %s...\n", hbuf); 173 continue; 174 } 175 if (refused && timo <= 16) { 176 (void)sleep(timo); 177 timo *= 2; 178 r = res; 179 refused = 0; 180 continue; 181 } 182 (void)fprintf(stderr, "%s: %s\n", res->ai_canonname, 183 strerror(errno)); 184 sigprocmask(SIG_SETMASK, &oldmask, NULL); 185 freeaddrinfo(res); 186 return (-1); 187 } 188 /* given "af" can be PF_UNSPEC, we need the real af for "s" */ 189 af = r->ai_family; 190 freeaddrinfo(res); 191 #if 0 192 /* 193 * try to rresvport() to the same port. This will make rresvport() 194 * fail it's first bind, resulting in it choosing a random port. 195 */ 196 lport--; 197 #endif 198 if (fd2p == 0) { 199 write(s, "", 1); 200 lport = 0; 201 } else { 202 char num[8]; 203 int s2 = rresvport_af(&lport, af), s3; 204 socklen_t len = sizeof(from); 205 int fdssize = howmany(MAX(s, s2)+1, NFDBITS) * sizeof(fd_mask); 206 207 if (s2 < 0) 208 goto bad; 209 readsp = (fd_set *)malloc(fdssize); 210 if (readsp == NULL) { 211 close(s2); 212 goto bad; 213 } 214 listen(s2, 1); 215 (void)snprintf(num, sizeof(num), "%d", lport); 216 if (write(s, num, strlen(num)+1) != strlen(num)+1) { 217 (void)fprintf(stderr, 218 "rcmd: write (setting up stderr): %s\n", 219 strerror(errno)); 220 (void)close(s2); 221 goto bad; 222 } 223 again: 224 bzero(readsp, fdssize); 225 FD_SET(s, readsp); 226 FD_SET(s2, readsp); 227 errno = 0; 228 if (select(MAX(s, s2) + 1, readsp, 0, 0, 0) < 1 || 229 !FD_ISSET(s2, readsp)) { 230 if (errno != 0) 231 (void)fprintf(stderr, 232 "rcmd: select (setting up stderr): %s\n", 233 strerror(errno)); 234 else 235 (void)fprintf(stderr, 236 "select: protocol failure in circuit setup\n"); 237 (void)close(s2); 238 goto bad; 239 } 240 s3 = accept(s2, (struct sockaddr *)&from, &len); 241 if (s3 < 0) { 242 (void)fprintf(stderr, 243 "rcmd: accept: %s\n", strerror(errno)); 244 lport = 0; 245 close(s2); 246 goto bad; 247 } 248 249 /* 250 * XXX careful for ftp bounce attacks. If discovered, shut them 251 * down and check for the real auxiliary channel to connect. 252 */ 253 switch (from.ss_family) { 254 case AF_INET: 255 case AF_INET6: 256 if (getnameinfo((struct sockaddr *)&from, len, 257 NULL, 0, num, sizeof(num), NI_NUMERICSERV) == 0 && 258 atoi(num) != 20) { 259 break; 260 } 261 close(s3); 262 goto again; 263 default: 264 break; 265 } 266 (void)close(s2); 267 268 *fd2p = s3; 269 switch (from.ss_family) { 270 case AF_INET: 271 case AF_INET6: 272 if (getnameinfo((struct sockaddr *)&from, len, 273 NULL, 0, num, sizeof(num), NI_NUMERICSERV) != 0 || 274 (atoi(num) >= IPPORT_RESERVED || 275 atoi(num) < IPPORT_RESERVED / 2)) { 276 (void)fprintf(stderr, 277 "socket: protocol failure in circuit setup.\n"); 278 goto bad2; 279 } 280 break; 281 default: 282 break; 283 } 284 } 285 (void)write(s, locuser, strlen(locuser)+1); 286 (void)write(s, remuser, strlen(remuser)+1); 287 (void)write(s, cmd, strlen(cmd)+1); 288 if (read(s, &c, 1) != 1) { 289 (void)fprintf(stderr, 290 "rcmd: %s: %s\n", *ahost, strerror(errno)); 291 goto bad2; 292 } 293 if (c != 0) { 294 while (read(s, &c, 1) == 1) { 295 (void)write(STDERR_FILENO, &c, 1); 296 if (c == '\n') 297 break; 298 } 299 goto bad2; 300 } 301 sigprocmask(SIG_SETMASK, &oldmask, NULL); 302 free(readsp); 303 return (s); 304 bad2: 305 if (lport) 306 (void)close(*fd2p); 307 bad: 308 if (readsp) 309 free(readsp); 310 (void)close(s); 311 sigprocmask(SIG_SETMASK, &oldmask, NULL); 312 return (-1); 313 } 314 315 int __check_rhosts_file = 1; 316 char *__rcmd_errstr; 317 318 int 319 ruserok(const char *rhost, int superuser, const char *ruser, const char *luser) 320 { 321 struct addrinfo hints, *res, *r; 322 int error; 323 324 memset(&hints, 0, sizeof(hints)); 325 hints.ai_family = PF_UNSPEC; 326 hints.ai_socktype = SOCK_DGRAM; /*dummy*/ 327 error = getaddrinfo(rhost, "0", &hints, &res); 328 if (error) 329 return (-1); 330 331 for (r = res; r; r = r->ai_next) { 332 if (iruserok_sa(r->ai_addr, r->ai_addrlen, superuser, ruser, 333 luser) == 0) { 334 freeaddrinfo(res); 335 return (0); 336 } 337 } 338 freeaddrinfo(res); 339 return (-1); 340 } 341 342 /* 343 * New .rhosts strategy: We are passed an ip address. We spin through 344 * hosts.equiv and .rhosts looking for a match. When the .rhosts only 345 * has ip addresses, we don't have to trust a nameserver. When it 346 * contains hostnames, we spin through the list of addresses the nameserver 347 * gives us and look for a match. 348 * 349 * Returns 0 if ok, -1 if not ok. 350 */ 351 int 352 iruserok(u_int32_t raddr, int superuser, const char *ruser, const char *luser) 353 { 354 struct sockaddr_in sin; 355 356 memset(&sin, 0, sizeof(sin)); 357 sin.sin_family = AF_INET; 358 sin.sin_len = sizeof(struct sockaddr_in); 359 memcpy(&sin.sin_addr, &raddr, sizeof(sin.sin_addr)); 360 return iruserok_sa(&sin, sizeof(struct sockaddr_in), superuser, ruser, 361 luser); 362 } 363 364 int 365 iruserok_sa(const void *raddr, int rlen, int superuser, const char *ruser, 366 const char *luser) 367 { 368 struct sockaddr *sa; 369 char *cp; 370 struct stat sbuf; 371 struct passwd *pwd; 372 FILE *hostf; 373 uid_t uid; 374 int first; 375 char pbuf[MAXPATHLEN]; 376 377 sa = (struct sockaddr *)raddr; 378 first = 1; 379 hostf = superuser ? NULL : fopen(_PATH_HEQUIV, "r"); 380 again: 381 if (hostf) { 382 if (__ivaliduser_sa(hostf, sa, rlen, luser, ruser) == 0) { 383 (void)fclose(hostf); 384 return (0); 385 } 386 (void)fclose(hostf); 387 } 388 if (first == 1 && (__check_rhosts_file || superuser)) { 389 first = 0; 390 if ((pwd = getpwnam(luser)) == NULL) 391 return (-1); 392 snprintf(pbuf, sizeof pbuf, "%s/.rhosts", pwd->pw_dir); 393 394 /* 395 * Change effective uid while opening .rhosts. If root and 396 * reading an NFS mounted file system, can't read files that 397 * are protected read/write owner only. 398 */ 399 uid = geteuid(); 400 (void)seteuid(pwd->pw_uid); 401 hostf = fopen(pbuf, "r"); 402 (void)seteuid(uid); 403 404 if (hostf == NULL) 405 return (-1); 406 /* 407 * If not a regular file, or is owned by someone other than 408 * user or root or if writeable by anyone but the owner, quit. 409 */ 410 cp = NULL; 411 if (lstat(pbuf, &sbuf) < 0) 412 cp = ".rhosts lstat failed"; 413 else if (!S_ISREG(sbuf.st_mode)) 414 cp = ".rhosts not regular file"; 415 else if (fstat(fileno(hostf), &sbuf) < 0) 416 cp = ".rhosts fstat failed"; 417 else if (sbuf.st_uid && sbuf.st_uid != pwd->pw_uid) 418 cp = "bad .rhosts owner"; 419 else if (sbuf.st_mode & (S_IWGRP|S_IWOTH)) 420 cp = ".rhosts writable by other than owner"; 421 /* If there were any problems, quit. */ 422 if (cp) { 423 __rcmd_errstr = cp; 424 (void)fclose(hostf); 425 return (-1); 426 } 427 goto again; 428 } 429 return (-1); 430 } 431 432 /* 433 * XXX 434 * Don't make static, used by lpd(8). 435 * 436 * Returns 0 if ok, -1 if not ok. 437 */ 438 int 439 __ivaliduser(FILE *hostf, in_addr_t raddrl, const char *luser, 440 const char *ruser) 441 { 442 struct sockaddr_in sin; 443 444 memset(&sin, 0, sizeof(sin)); 445 sin.sin_family = AF_INET; 446 sin.sin_len = sizeof(struct sockaddr_in); 447 memcpy(&sin.sin_addr, &raddrl, sizeof(sin.sin_addr)); 448 return __ivaliduser_sa(hostf, (struct sockaddr *)&sin, sin.sin_len, 449 luser, ruser); 450 } 451 452 int 453 __ivaliduser_sa(FILE *hostf, struct sockaddr *raddr, socklen_t salen, 454 const char *luser, const char *ruser) 455 { 456 char *user, *p; 457 char *buf; 458 const char *auser, *ahost; 459 int hostok, userok; 460 char *rhost = (char *)-1; 461 char domain[MAXHOSTNAMELEN]; 462 size_t buflen; 463 464 getdomainname(domain, sizeof(domain)); 465 466 while ((buf = fgetln(hostf, &buflen))) { 467 p = buf; 468 if (*p == '#') 469 continue; 470 while (p < buf + buflen && *p != '\n' && *p != ' ' && *p != '\t') { 471 if (!isprint(*p)) 472 goto bail; 473 *p = isupper(*p) ? tolower(*p) : *p; 474 p++; 475 } 476 if (p >= buf + buflen) 477 continue; 478 if (*p == ' ' || *p == '\t') { 479 *p++ = '\0'; 480 while (p < buf + buflen && (*p == ' ' || *p == '\t')) 481 p++; 482 if (p >= buf + buflen) 483 continue; 484 user = p; 485 while (p < buf + buflen && *p != '\n' && *p != ' ' && 486 *p != '\t') { 487 if (!isprint(*p)) 488 goto bail; 489 p++; 490 } 491 } else 492 user = p; 493 *p = '\0'; 494 495 if (p == buf) 496 continue; 497 498 auser = *user ? user : luser; 499 ahost = buf; 500 501 if (strlen(ahost) >= MAXHOSTNAMELEN) 502 continue; 503 504 /* 505 * innetgr() must lookup a hostname (we do not attempt 506 * to change the semantics so that netgroups may have 507 * #.#.#.# addresses in the list.) 508 */ 509 if (ahost[0] == '+') 510 switch (ahost[1]) { 511 case '\0': 512 hostok = 1; 513 break; 514 case '@': 515 if (rhost == (char *)-1) 516 rhost = __gethostloop(raddr, salen); 517 hostok = 0; 518 if (rhost) 519 hostok = innetgr(&ahost[2], rhost, 520 NULL, domain); 521 break; 522 default: 523 hostok = __icheckhost(raddr, salen, &ahost[1]); 524 break; 525 } 526 else if (ahost[0] == '-') 527 switch (ahost[1]) { 528 case '\0': 529 hostok = -1; 530 break; 531 case '@': 532 if (rhost == (char *)-1) 533 rhost = __gethostloop(raddr, salen); 534 hostok = 0; 535 if (rhost) 536 hostok = -innetgr(&ahost[2], rhost, 537 NULL, domain); 538 break; 539 default: 540 hostok = -__icheckhost(raddr, salen, &ahost[1]); 541 break; 542 } 543 else 544 hostok = __icheckhost(raddr, salen, ahost); 545 546 547 if (auser[0] == '+') 548 switch (auser[1]) { 549 case '\0': 550 userok = 1; 551 break; 552 case '@': 553 userok = innetgr(&auser[2], NULL, ruser, 554 domain); 555 break; 556 default: 557 userok = strcmp(ruser, &auser[1]) ? 0 : 1; 558 break; 559 } 560 else if (auser[0] == '-') 561 switch (auser[1]) { 562 case '\0': 563 userok = -1; 564 break; 565 case '@': 566 userok = -innetgr(&auser[2], NULL, ruser, 567 domain); 568 break; 569 default: 570 userok = strcmp(ruser, &auser[1]) ? 0 : -1; 571 break; 572 } 573 else 574 userok = strcmp(ruser, auser) ? 0 : 1; 575 576 /* Check if one component did not match */ 577 if (hostok == 0 || userok == 0) 578 continue; 579 580 /* Check if we got a forbidden pair */ 581 if (userok <= -1 || hostok <= -1) 582 return (-1); 583 584 /* Check if we got a valid pair */ 585 if (hostok >= 1 && userok >= 1) 586 return (0); 587 } 588 bail: 589 return (-1); 590 } 591 592 /* 593 * Returns "true" if match, 0 if no match. If we do not find any 594 * semblance of an A->PTR->A loop, allow a simple #.#.#.# match to work. 595 */ 596 static int 597 __icheckhost(struct sockaddr *raddr, socklen_t salen, const char *lhost) 598 { 599 struct addrinfo hints, *res, *r; 600 char h1[NI_MAXHOST], h2[NI_MAXHOST]; 601 int error; 602 const int niflags = NI_NUMERICHOST; 603 604 h1[0] = '\0'; 605 if (getnameinfo(raddr, salen, h1, sizeof(h1), NULL, 0, 606 niflags) != 0) 607 return (0); 608 609 /* Resolve laddr into sockaddr */ 610 memset(&hints, 0, sizeof(hints)); 611 hints.ai_family = raddr->sa_family; 612 hints.ai_socktype = SOCK_DGRAM; /*dummy*/ 613 res = NULL; 614 error = getaddrinfo(lhost, "0", &hints, &res); 615 if (error) 616 return (0); 617 618 /* 619 * Try string comparisons between raddr and laddr. 620 */ 621 for (r = res; r; r = r->ai_next) { 622 h2[0] = '\0'; 623 if (getnameinfo(r->ai_addr, r->ai_addrlen, h2, sizeof(h2), 624 NULL, 0, niflags) != 0) 625 continue; 626 if (strcmp(h1, h2) == 0) { 627 freeaddrinfo(res); 628 return (1); 629 } 630 } 631 632 /* No match. */ 633 freeaddrinfo(res); 634 return (0); 635 } 636 637 /* 638 * Return the hostname associated with the supplied address. 639 * Do a reverse lookup as well for security. If a loop cannot 640 * be found, pack the result of inet_ntoa() into the string. 641 */ 642 static char * 643 __gethostloop(struct sockaddr *raddr, socklen_t salen) 644 { 645 static char remotehost[NI_MAXHOST]; 646 char h1[NI_MAXHOST], h2[NI_MAXHOST]; 647 struct addrinfo hints, *res, *r; 648 int error; 649 const int niflags = NI_NUMERICHOST; 650 651 h1[0] = remotehost[0] = '\0'; 652 if (getnameinfo(raddr, salen, remotehost, sizeof(remotehost), 653 NULL, 0, NI_NAMEREQD) != 0) 654 return (NULL); 655 if (getnameinfo(raddr, salen, h1, sizeof(h1), NULL, 0, 656 niflags) != 0) 657 return (NULL); 658 659 /* 660 * Look up the name and check that the supplied 661 * address is in the list 662 */ 663 memset(&hints, 0, sizeof(hints)); 664 hints.ai_family = raddr->sa_family; 665 hints.ai_socktype = SOCK_DGRAM; /*dummy*/ 666 hints.ai_flags = AI_CANONNAME; 667 res = NULL; 668 error = getaddrinfo(remotehost, "0", &hints, &res); 669 if (error) 670 return (NULL); 671 672 for (r = res; r; r = r->ai_next) { 673 h2[0] = '\0'; 674 if (getnameinfo(r->ai_addr, r->ai_addrlen, h2, sizeof(h2), 675 NULL, 0, niflags) != 0) 676 continue; 677 if (strcmp(h1, h2) == 0) { 678 freeaddrinfo(res); 679 return (remotehost); 680 } 681 } 682 683 /* 684 * either the DNS adminstrator has made a configuration 685 * mistake, or someone has attempted to spoof us 686 */ 687 syslog(LOG_NOTICE, "rcmd: address %s not listed for host %s", 688 h1, res->ai_canonname ? res->ai_canonname : remotehost); 689 freeaddrinfo(res); 690 return (NULL); 691 } 692