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 38static 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 45static 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: stable/11/libexec/rshd/rshd.c 360673 2020-05-05 20:53:45Z dim $"); 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#ifdef USE_BLACKLIST 92#include <blacklist.h> 93#endif 94 95static struct pam_conv pamc = { openpam_nullconv, NULL }; 96static pam_handle_t *pamh; 97static 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 108int keepalive = 1; 109int log_success; /* If TRUE, log all successful accesses */ 110int sent_null; 111int no_delay; 112 113void doit(struct sockaddr *); 114static void rshd_errx(int, const char *, ...) __printf0like(2, 3); 115void getstr(char *, int, const char *); 116int local_domain(char *); 117char *topdomain(char *); 118void usage(void); 119 120char slash[] = "/"; 121char bshell[] = _PATH_BSHELL; 122 123#define OPTIONS "aDLln" 124 125int 126main(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_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 185extern char **environ; 186 187void 188doit(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, 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#ifdef USE_BLACKLIST 260 blacklist(1, STDIN_FILENO, "illegal port"); 261#endif 262 exit(1); 263 } 264 265 (void) alarm(60); 266 port = 0; 267 s = 0; /* not set or used if port == 0 */ 268 for (;;) { 269 char c; 270 if ((cc = read(STDIN_FILENO, &c, 1)) != 1) { 271 if (cc < 0) 272 syslog(LOG_NOTICE, "read: %m"); 273 shutdown(0, SHUT_RDWR); 274 exit(1); 275 } 276 if (c == 0) 277 break; 278 port = port * 10 + c - '0'; 279 } 280 281 (void) alarm(0); 282 if (port != 0) { 283 int lport = IPPORT_RESERVED - 1; 284 s = rresvport_af(&lport, af); 285 if (s < 0) { 286 syslog(LOG_ERR, "can't get stderr port: %m"); 287 exit(1); 288 } 289 if (port >= IPPORT_RESERVED || 290 port < IPPORT_RESERVED/2) { 291 syslog(LOG_NOTICE|LOG_AUTH, 292 "2nd socket from %s on unreserved port %u", 293 numericname, 294 port); 295#ifdef USE_BLACKLIST 296 blacklist(1, STDIN_FILENO, "unreserved port"); 297#endif 298 exit(1); 299 } 300 *((in_port_t *)&fromp->sa_data) = htons(port); 301 if (connect(s, fromp, fromp->sa_len) < 0) { 302 syslog(LOG_INFO, "connect second port %d: %m", port); 303 exit(1); 304 } 305 } 306 307 errorstr = NULL; 308 realhostname_sa(rhost, sizeof(rhost) - 1, fromp, fromp->sa_len); 309 rhost[sizeof(rhost) - 1] = '\0'; 310 /* XXX truncation! */ 311 312 (void) alarm(60); 313 getstr(ruser, sizeof(ruser), "ruser"); 314 getstr(luser, sizeof(luser), "luser"); 315 getstr(cmdbuf, maxcmdlen, "command"); 316 (void) alarm(0); 317 318 pam_err = pam_start("rsh", luser, &pamc, &pamh); 319 if (pam_err != PAM_SUCCESS) { 320 syslog(LOG_ERR|LOG_AUTH, "pam_start(): %s", 321 pam_strerror(pamh, pam_err)); 322#ifdef USE_BLACKLIST 323 blacklist(1, STDIN_FILENO, "login incorrect"); 324#endif 325 rshd_errx(1, "Login incorrect."); 326 } 327 328 if ((pam_err = pam_set_item(pamh, PAM_RUSER, ruser)) != PAM_SUCCESS || 329 (pam_err = pam_set_item(pamh, PAM_RHOST, rhost)) != PAM_SUCCESS) { 330 syslog(LOG_ERR|LOG_AUTH, "pam_set_item(): %s", 331 pam_strerror(pamh, pam_err)); 332#ifdef USE_BLACKLIST 333 blacklist(1, STDIN_FILENO, "login incorrect"); 334#endif 335 rshd_errx(1, "Login incorrect."); 336 } 337 338 pam_err = pam_authenticate(pamh, 0); 339 if (pam_err == PAM_SUCCESS) { 340 if ((pam_err = pam_get_user(pamh, &cp, NULL)) == PAM_SUCCESS) { 341 strlcpy(luser, cp, sizeof(luser)); 342 /* XXX truncation! */ 343 } 344 pam_err = pam_acct_mgmt(pamh, 0); 345 } 346 if (pam_err != PAM_SUCCESS) { 347 syslog(LOG_INFO|LOG_AUTH, 348 "%s@%s as %s: permission denied (%s). cmd='%.80s'", 349 ruser, rhost, luser, pam_strerror(pamh, pam_err), cmdbuf); 350#ifdef USE_BLACKLIST 351 blacklist(1, STDIN_FILENO, "permission denied"); 352#endif 353 rshd_errx(1, "Login incorrect."); 354 } 355 356 setpwent(); 357 pwd = getpwnam(luser); 358 if (pwd == NULL) { 359 syslog(LOG_INFO|LOG_AUTH, 360 "%s@%s as %s: unknown login. cmd='%.80s'", 361 ruser, rhost, luser, cmdbuf); 362#ifdef USE_BLACKLIST 363 blacklist(1, STDIN_FILENO, "unknown login"); 364#endif 365 if (errorstr == NULL) 366 errorstr = "Login incorrect."; 367 rshd_errx(1, errorstr, rhost); 368 } 369 370 lc = login_getpwclass(pwd); 371 if (pwd->pw_uid) 372 auth_checknologin(lc); 373 374 if (chdir(pwd->pw_dir) < 0) { 375 if (chdir("/") < 0 || 376 login_getcapbool(lc, "requirehome", !!pwd->pw_uid)) { 377 syslog(LOG_INFO|LOG_AUTH, 378 "%s@%s as %s: no home directory. cmd='%.80s'", 379 ruser, rhost, luser, cmdbuf); 380 rshd_errx(0, "No remote home directory."); 381 } 382 pwd->pw_dir = slash; 383 } 384 385 if (lc != NULL && fromp->sa_family == AF_INET) { /*XXX*/ 386 char remote_ip[MAXHOSTNAMELEN]; 387 388 strlcpy(remote_ip, numericname, sizeof(remote_ip)); 389 /* XXX truncation! */ 390 if (!auth_hostok(lc, rhost, remote_ip)) { 391 syslog(LOG_INFO|LOG_AUTH, 392 "%s@%s as %s: permission denied (%s). cmd='%.80s'", 393 ruser, rhost, luser, __rcmd_errstr, 394 cmdbuf); 395#ifdef USE_BLACKLIST 396 blacklist(1, STDIN_FILENO, "permission denied"); 397#endif 398 rshd_errx(1, "Login incorrect."); 399 } 400 if (!auth_timeok(lc, time(NULL))) 401 rshd_errx(1, "Logins not available right now"); 402 } 403 404 /* 405 * PAM modules might add supplementary groups in 406 * pam_setcred(), so initialize them first. 407 * But we need to open the session as root. 408 */ 409 if (setusercontext(lc, pwd, pwd->pw_uid, LOGIN_SETGROUP) != 0) { 410 syslog(LOG_ERR, "setusercontext: %m"); 411 exit(1); 412 } 413 414 if ((pam_err = pam_open_session(pamh, 0)) != PAM_SUCCESS) { 415 syslog(LOG_ERR, "pam_open_session: %s", pam_strerror(pamh, pam_err)); 416 } else if ((pam_err = pam_setcred(pamh, PAM_ESTABLISH_CRED)) != PAM_SUCCESS) { 417 syslog(LOG_ERR, "pam_setcred: %s", pam_strerror(pamh, pam_err)); 418 } 419 420 (void) write(STDERR_FILENO, "\0", 1); 421 sent_null = 1; 422 423 if (port) { 424 if (pipe(pv) < 0) 425 rshd_errx(1, "Can't make pipe."); 426 pid = fork(); 427 if (pid == -1) 428 rshd_errx(1, "Can't fork; try again."); 429 if (pid) { 430 (void) close(0); 431 (void) close(1); 432 (void) close(2); 433 (void) close(pv[1]); 434 435 FD_ZERO(&readfrom); 436 FD_SET(s, &readfrom); 437 FD_SET(pv[0], &readfrom); 438 if (pv[0] > s) 439 nfd = pv[0]; 440 else 441 nfd = s; 442 ioctl(pv[0], FIONBIO, (char *)&one); 443 444 /* should set s nbio! */ 445 nfd++; 446 do { 447 ready = readfrom; 448 if (select(nfd, &ready, (fd_set *)0, 449 (fd_set *)0, (struct timeval *)0) < 0) 450 break; 451 if (FD_ISSET(s, &ready)) { 452 int ret; 453 ret = read(s, &sig, 1); 454 if (ret <= 0) 455 FD_CLR(s, &readfrom); 456 else 457 killpg(pid, sig); 458 } 459 if (FD_ISSET(pv[0], &ready)) { 460 errno = 0; 461 cc = read(pv[0], buf, sizeof(buf)); 462 if (cc <= 0) { 463 shutdown(s, SHUT_RDWR); 464 FD_CLR(pv[0], &readfrom); 465 } else { 466 (void)write(s, buf, cc); 467 } 468 } 469 470 } while (FD_ISSET(s, &readfrom) || 471 FD_ISSET(pv[0], &readfrom)); 472 PAM_END; 473 exit(0); 474 } 475 (void) close(s); 476 (void) close(pv[0]); 477 dup2(pv[1], 2); 478 close(pv[1]); 479 } 480 else { 481 pid = fork(); 482 if (pid == -1) 483 rshd_errx(1, "Can't fork; try again."); 484 if (pid) { 485 /* Parent. */ 486 while (wait(NULL) > 0 || errno == EINTR) 487 /* nothing */ ; 488 PAM_END; 489 exit(0); 490 } 491 } 492 493#ifdef USE_BLACKLIST 494 blacklist(0, STDIN_FILENO, "success"); 495#endif 496 closefrom(3); 497 if (setsid() == -1) 498 syslog(LOG_ERR, "setsid() failed: %m"); 499 if (setlogin(pwd->pw_name) < 0) 500 syslog(LOG_ERR, "setlogin() failed: %m"); 501 502 if (*pwd->pw_shell == '\0') 503 pwd->pw_shell = bshell; 504 (void) pam_setenv(pamh, "HOME", pwd->pw_dir, 1); 505 (void) pam_setenv(pamh, "SHELL", pwd->pw_shell, 1); 506 (void) pam_setenv(pamh, "USER", pwd->pw_name, 1); 507 (void) pam_setenv(pamh, "PATH", _PATH_DEFPATH, 1); 508 environ = pam_getenvlist(pamh); 509 (void) pam_end(pamh, pam_err); 510 cp = strrchr(pwd->pw_shell, '/'); 511 if (cp) 512 cp++; 513 else 514 cp = pwd->pw_shell; 515 516 if (setusercontext(lc, pwd, pwd->pw_uid, 517 LOGIN_SETALL & ~LOGIN_SETGROUP) < 0) { 518 syslog(LOG_ERR, "setusercontext(): %m"); 519 exit(1); 520 } 521 login_close(lc); 522 endpwent(); 523 if (log_success || pwd->pw_uid == 0) { 524 syslog(LOG_INFO|LOG_AUTH, "%s@%s as %s: cmd='%.80s'", 525 ruser, rhost, luser, cmdbuf); 526 } 527 execl(pwd->pw_shell, cp, "-c", cmdbuf, (char *)NULL); 528 err(1, "%s", pwd->pw_shell); 529 exit(1); 530} 531 532/* 533 * Report error to client. Note: can't be used until second socket has 534 * connected to client, or older clients will hang waiting for that 535 * connection first. 536 */ 537 538static void 539rshd_errx(int errcode, const char *fmt, ...) 540{ 541 va_list ap; 542 543 va_start(ap, fmt); 544 545 if (sent_null == 0) 546 write(STDERR_FILENO, "\1", 1); 547 548 verrx(errcode, fmt, ap); 549 /* NOTREACHED */ 550} 551 552void 553getstr(char *buf, int cnt, const char *error) 554{ 555 char c; 556 557 do { 558 if (read(STDIN_FILENO, &c, 1) != 1) 559 exit(1); 560 *buf++ = c; 561 if (--cnt == 0) { 562#ifdef USE_BLACKLIST 563 blacklist(1, STDIN_FILENO, "buffer overflow"); 564#endif 565 rshd_errx(1, "%s too long", error); 566 } 567 } while (c != 0); 568} 569 570/* 571 * Check whether host h is in our local domain, 572 * defined as sharing the last two components of the domain part, 573 * or the entire domain part if the local domain has only one component. 574 * If either name is unqualified (contains no '.'), 575 * assume that the host is local, as it will be 576 * interpreted as such. 577 */ 578int 579local_domain(char *h) 580{ 581 char localhost[MAXHOSTNAMELEN]; 582 char *p1, *p2; 583 584 localhost[0] = 0; 585 (void) gethostname(localhost, sizeof(localhost) - 1); 586 localhost[sizeof(localhost) - 1] = '\0'; 587 /* XXX truncation! */ 588 p1 = topdomain(localhost); 589 p2 = topdomain(h); 590 if (p1 == NULL || p2 == NULL || !strcasecmp(p1, p2)) 591 return (1); 592 return (0); 593} 594 595char * 596topdomain(char *h) 597{ 598 char *p, *maybe = NULL; 599 int dots = 0; 600 601 for (p = h + strlen(h); p >= h; p--) { 602 if (*p == '.') { 603 if (++dots == 2) 604 return (p); 605 maybe = p; 606 } 607 } 608 return (maybe); 609} 610 611void 612usage(void) 613{ 614 615 syslog(LOG_ERR, "usage: rshd [-%s]", OPTIONS); 616 exit(2); 617} 618