rshd.c revision 143907
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 42static 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 49static 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: head/libexec/rshd/rshd.c 143907 2005-03-21 08:01:14Z das $"); 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 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_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 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, 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, 1+1); 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, 1+1); 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 518static void 519rshd_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 532void 533getstr(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 */ 554int 555local_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 571char * 572topdomain(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 587void 588usage(void) 589{ 590 591 syslog(LOG_ERR, "usage: rshd [-%s]", OPTIONS); 592 exit(2); 593} 594