1 /*- 2 * Copyright (c) 2002 Networks Associates Technology, Inc. 3 * All rights reserved. 4 * 5 * This software was developed for the FreeBSD Project by ThinkSec AS and 6 * NAI Labs, the Security Research Division of Network Associates, Inc. 7 * under DARPA/SPAWAR contract N66001-01-C-8035 ("CBOSS"), as part of the 8 * DARPA CHATS research program. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29 * SUCH DAMAGE. 30 */ 31 /* 32 * Copyright (c) 2003,2004 Damien Miller <djm@mindrot.org> 33 * Copyright (c) 2003,2004 Darren Tucker <dtucker@zip.com.au> 34 * 35 * Permission to use, copy, modify, and distribute this software for any 36 * purpose with or without fee is hereby granted, provided that the above 37 * copyright notice and this permission notice appear in all copies. 38 * 39 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES 40 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF 41 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR 42 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES 43 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN 44 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF 45 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. 46 */ 47 48 /* Based on FreeBSD: src/crypto/openssh/auth2-pam-freebsd.c,v 1.11 2003/03/31 13:48:18 des */ 49 50 #include "includes.h" 51 52 #include <sys/types.h> 53 #include <sys/stat.h> 54 #include <sys/wait.h> 55 56 #include <errno.h> 57 #include <signal.h> 58 #include <stdarg.h> 59 #include <string.h> 60 #include <unistd.h> 61 62 #ifdef USE_PAM 63 #if defined(HAVE_SECURITY_PAM_APPL_H) 64 #include <security/pam_appl.h> 65 #elif defined (HAVE_PAM_PAM_APPL_H) 66 #include <pam/pam_appl.h> 67 #endif 68 69 #if !defined(SSHD_PAM_SERVICE) 70 extern char *__progname; 71 # define SSHD_PAM_SERVICE __progname 72 #endif 73 74 /* OpenGroup RFC86.0 and XSSO specify no "const" on arguments */ 75 #ifdef PAM_SUN_CODEBASE 76 # define sshpam_const /* Solaris, HP-UX, SunOS */ 77 #else 78 # define sshpam_const const /* LinuxPAM, OpenPAM, AIX */ 79 #endif 80 81 /* Ambiguity in spec: is it an array of pointers or a pointer to an array? */ 82 #ifdef PAM_SUN_CODEBASE 83 # define PAM_MSG_MEMBER(msg, n, member) ((*(msg))[(n)].member) 84 #else 85 # define PAM_MSG_MEMBER(msg, n, member) ((msg)[(n)]->member) 86 #endif 87 88 #include "xmalloc.h" 89 #include "buffer.h" 90 #include "key.h" 91 #include "hostfile.h" 92 #include "auth.h" 93 #include "auth-pam.h" 94 #include "canohost.h" 95 #include "log.h" 96 #include "msg.h" 97 #include "packet.h" 98 #include "misc.h" 99 #include "servconf.h" 100 #include "ssh2.h" 101 #include "auth-options.h" 102 #ifdef GSSAPI 103 #include "ssh-gss.h" 104 #endif 105 #include "monitor_wrap.h" 106 107 extern ServerOptions options; 108 extern Buffer loginmsg; 109 extern u_int utmp_len; 110 111 /* so we don't silently change behaviour */ 112 #ifdef USE_POSIX_THREADS 113 # error "USE_POSIX_THREADS replaced by UNSUPPORTED_POSIX_THREADS_HACK" 114 #endif 115 116 /* 117 * Formerly known as USE_POSIX_THREADS, using this is completely unsupported 118 * and generally a bad idea. Use at own risk and do not expect support if 119 * this breaks. 120 */ 121 #ifdef UNSUPPORTED_POSIX_THREADS_HACK 122 #include <pthread.h> 123 /* 124 * Avoid namespace clash when *not* using pthreads for systems *with* 125 * pthreads, which unconditionally define pthread_t via sys/types.h 126 * (e.g. Linux) 127 */ 128 typedef pthread_t sp_pthread_t; 129 #else 130 typedef pid_t sp_pthread_t; 131 #endif 132 133 struct pam_ctxt { 134 sp_pthread_t pam_thread; 135 int pam_psock; 136 int pam_csock; 137 int pam_done; 138 }; 139 140 static void sshpam_free_ctx(void *); 141 static struct pam_ctxt *cleanup_ctxt; 142 143 #ifndef UNSUPPORTED_POSIX_THREADS_HACK 144 /* 145 * Simulate threads with processes. 146 */ 147 148 static int sshpam_thread_status = -1; 149 static mysig_t sshpam_oldsig; 150 151 static void 152 sshpam_sigchld_handler(int sig) 153 { 154 signal(SIGCHLD, SIG_DFL); 155 if (cleanup_ctxt == NULL) 156 return; /* handler called after PAM cleanup, shouldn't happen */ 157 if (waitpid(cleanup_ctxt->pam_thread, &sshpam_thread_status, WNOHANG) 158 <= 0) { 159 /* PAM thread has not exitted, privsep slave must have */ 160 kill(cleanup_ctxt->pam_thread, SIGTERM); 161 while (waitpid(cleanup_ctxt->pam_thread, 162 &sshpam_thread_status, 0) == -1) { 163 if (errno == EINTR) 164 continue; 165 return; 166 } 167 } 168 if (WIFSIGNALED(sshpam_thread_status) && 169 WTERMSIG(sshpam_thread_status) == SIGTERM) 170 return; /* terminated by pthread_cancel */ 171 if (!WIFEXITED(sshpam_thread_status)) 172 sigdie("PAM: authentication thread exited unexpectedly"); 173 if (WEXITSTATUS(sshpam_thread_status) != 0) 174 sigdie("PAM: authentication thread exited uncleanly"); 175 } 176 177 /* ARGSUSED */ 178 static void 179 pthread_exit(void *value) 180 { 181 _exit(0); 182 } 183 184 /* ARGSUSED */ 185 static int 186 pthread_create(sp_pthread_t *thread, const void *attr, 187 void *(*thread_start)(void *), void *arg) 188 { 189 pid_t pid; 190 struct pam_ctxt *ctx = arg; 191 192 sshpam_thread_status = -1; 193 switch ((pid = fork())) { 194 case -1: 195 error("fork(): %s", strerror(errno)); 196 return (-1); 197 case 0: 198 close(ctx->pam_psock); 199 ctx->pam_psock = -1; 200 thread_start(arg); 201 _exit(1); 202 default: 203 *thread = pid; 204 close(ctx->pam_csock); 205 ctx->pam_csock = -1; 206 sshpam_oldsig = signal(SIGCHLD, sshpam_sigchld_handler); 207 return (0); 208 } 209 } 210 211 static int 212 pthread_cancel(sp_pthread_t thread) 213 { 214 signal(SIGCHLD, sshpam_oldsig); 215 return (kill(thread, SIGTERM)); 216 } 217 218 /* ARGSUSED */ 219 static int 220 pthread_join(sp_pthread_t thread, void **value) 221 { 222 int status; 223 224 if (sshpam_thread_status != -1) 225 return (sshpam_thread_status); 226 signal(SIGCHLD, sshpam_oldsig); 227 while (waitpid(thread, &status, 0) == -1) { 228 if (errno == EINTR) 229 continue; 230 fatal("%s: waitpid: %s", __func__, strerror(errno)); 231 } 232 return (status); 233 } 234 #endif 235 236 237 static pam_handle_t *sshpam_handle = NULL; 238 static int sshpam_err = 0; 239 static int sshpam_authenticated = 0; 240 static int sshpam_session_open = 0; 241 static int sshpam_cred_established = 0; 242 static int sshpam_account_status = -1; 243 static int sshpam_maxtries_reached = 0; 244 static char **sshpam_env = NULL; 245 static Authctxt *sshpam_authctxt = NULL; 246 static const char *sshpam_password = NULL; 247 248 /* Some PAM implementations don't implement this */ 249 #ifndef HAVE_PAM_GETENVLIST 250 static char ** 251 pam_getenvlist(pam_handle_t *pamh) 252 { 253 /* 254 * XXX - If necessary, we can still support envrionment passing 255 * for platforms without pam_getenvlist by searching for known 256 * env vars (e.g. KRB5CCNAME) from the PAM environment. 257 */ 258 return NULL; 259 } 260 #endif 261 262 /* 263 * Some platforms, notably Solaris, do not enforce password complexity 264 * rules during pam_chauthtok() if the real uid of the calling process 265 * is 0, on the assumption that it's being called by "passwd" run by root. 266 * This wraps pam_chauthtok and sets/restore the real uid so PAM will do 267 * the right thing. 268 */ 269 #ifdef SSHPAM_CHAUTHTOK_NEEDS_RUID 270 static int 271 sshpam_chauthtok_ruid(pam_handle_t *pamh, int flags) 272 { 273 int result; 274 275 if (sshpam_authctxt == NULL) 276 fatal("PAM: sshpam_authctxt not initialized"); 277 if (setreuid(sshpam_authctxt->pw->pw_uid, -1) == -1) 278 fatal("%s: setreuid failed: %s", __func__, strerror(errno)); 279 result = pam_chauthtok(pamh, flags); 280 if (setreuid(0, -1) == -1) 281 fatal("%s: setreuid failed: %s", __func__, strerror(errno)); 282 return result; 283 } 284 # define pam_chauthtok(a,b) (sshpam_chauthtok_ruid((a), (b))) 285 #endif 286 287 static void 288 sshpam_password_change_required(int reqd) 289 { 290 debug3("%s %d", __func__, reqd); 291 if (sshpam_authctxt == NULL) 292 fatal("%s: PAM authctxt not initialized", __func__); 293 sshpam_authctxt->force_pwchange = reqd; 294 if (reqd) { 295 no_port_forwarding_flag |= 2; 296 no_agent_forwarding_flag |= 2; 297 no_x11_forwarding_flag |= 2; 298 } else { 299 no_port_forwarding_flag &= ~2; 300 no_agent_forwarding_flag &= ~2; 301 no_x11_forwarding_flag &= ~2; 302 } 303 } 304 305 /* Import regular and PAM environment from subprocess */ 306 static void 307 import_environments(Buffer *b) 308 { 309 char *env; 310 u_int i, num_env; 311 int err; 312 313 debug3("PAM: %s entering", __func__); 314 315 #ifndef UNSUPPORTED_POSIX_THREADS_HACK 316 /* Import variables set by do_pam_account */ 317 sshpam_account_status = buffer_get_int(b); 318 sshpam_password_change_required(buffer_get_int(b)); 319 320 /* Import environment from subprocess */ 321 num_env = buffer_get_int(b); 322 if (num_env > 1024) 323 fatal("%s: received %u environment variables, expected <= 1024", 324 __func__, num_env); 325 sshpam_env = xcalloc(num_env + 1, sizeof(*sshpam_env)); 326 debug3("PAM: num env strings %d", num_env); 327 for(i = 0; i < num_env; i++) 328 sshpam_env[i] = buffer_get_string(b, NULL); 329 330 sshpam_env[num_env] = NULL; 331 332 /* Import PAM environment from subprocess */ 333 num_env = buffer_get_int(b); 334 debug("PAM: num PAM env strings %d", num_env); 335 for(i = 0; i < num_env; i++) { 336 env = buffer_get_string(b, NULL); 337 338 #ifdef HAVE_PAM_PUTENV 339 /* Errors are not fatal here */ 340 if ((err = pam_putenv(sshpam_handle, env)) != PAM_SUCCESS) { 341 error("PAM: pam_putenv: %s", 342 pam_strerror(sshpam_handle, sshpam_err)); 343 } 344 #endif 345 } 346 #endif 347 } 348 349 /* 350 * Conversation function for authentication thread. 351 */ 352 static int 353 sshpam_thread_conv(int n, sshpam_const struct pam_message **msg, 354 struct pam_response **resp, void *data) 355 { 356 Buffer buffer; 357 struct pam_ctxt *ctxt; 358 struct pam_response *reply; 359 int i; 360 361 debug3("PAM: %s entering, %d messages", __func__, n); 362 *resp = NULL; 363 364 if (data == NULL) { 365 error("PAM: conversation function passed a null context"); 366 return (PAM_CONV_ERR); 367 } 368 ctxt = data; 369 if (n <= 0 || n > PAM_MAX_NUM_MSG) 370 return (PAM_CONV_ERR); 371 372 if ((reply = calloc(n, sizeof(*reply))) == NULL) 373 return (PAM_CONV_ERR); 374 375 buffer_init(&buffer); 376 for (i = 0; i < n; ++i) { 377 switch (PAM_MSG_MEMBER(msg, i, msg_style)) { 378 case PAM_PROMPT_ECHO_OFF: 379 case PAM_PROMPT_ECHO_ON: 380 buffer_put_cstring(&buffer, 381 PAM_MSG_MEMBER(msg, i, msg)); 382 if (ssh_msg_send(ctxt->pam_csock, 383 PAM_MSG_MEMBER(msg, i, msg_style), &buffer) == -1) 384 goto fail; 385 if (ssh_msg_recv(ctxt->pam_csock, &buffer) == -1) 386 goto fail; 387 if (buffer_get_char(&buffer) != PAM_AUTHTOK) 388 goto fail; 389 reply[i].resp = buffer_get_string(&buffer, NULL); 390 break; 391 case PAM_ERROR_MSG: 392 case PAM_TEXT_INFO: 393 buffer_put_cstring(&buffer, 394 PAM_MSG_MEMBER(msg, i, msg)); 395 if (ssh_msg_send(ctxt->pam_csock, 396 PAM_MSG_MEMBER(msg, i, msg_style), &buffer) == -1) 397 goto fail; 398 break; 399 default: 400 goto fail; 401 } 402 buffer_clear(&buffer); 403 } 404 buffer_free(&buffer); 405 *resp = reply; 406 return (PAM_SUCCESS); 407 408 fail: 409 for(i = 0; i < n; i++) { 410 free(reply[i].resp); 411 } 412 free(reply); 413 buffer_free(&buffer); 414 return (PAM_CONV_ERR); 415 } 416 417 /* 418 * Authentication thread. 419 */ 420 static void * 421 sshpam_thread(void *ctxtp) 422 { 423 struct pam_ctxt *ctxt = ctxtp; 424 Buffer buffer; 425 struct pam_conv sshpam_conv; 426 int flags = (options.permit_empty_passwd == 0 ? 427 PAM_DISALLOW_NULL_AUTHTOK : 0); 428 #ifndef UNSUPPORTED_POSIX_THREADS_HACK 429 extern char **environ; 430 char **env_from_pam; 431 u_int i; 432 const char *pam_user; 433 const char **ptr_pam_user = &pam_user; 434 char *tz = getenv("TZ"); 435 436 sshpam_err = pam_get_item(sshpam_handle, PAM_USER, 437 (sshpam_const void **)ptr_pam_user); 438 if (sshpam_err != PAM_SUCCESS) 439 goto auth_fail; 440 441 environ[0] = NULL; 442 if (tz != NULL) 443 if (setenv("TZ", tz, 1) == -1) 444 error("PAM: could not set TZ environment: %s", 445 strerror(errno)); 446 447 if (sshpam_authctxt != NULL) { 448 setproctitle("%s [pam]", 449 sshpam_authctxt->valid ? pam_user : "unknown"); 450 } 451 #endif 452 453 sshpam_conv.conv = sshpam_thread_conv; 454 sshpam_conv.appdata_ptr = ctxt; 455 456 if (sshpam_authctxt == NULL) 457 fatal("%s: PAM authctxt not initialized", __func__); 458 459 buffer_init(&buffer); 460 sshpam_err = pam_set_item(sshpam_handle, PAM_CONV, 461 (const void *)&sshpam_conv); 462 if (sshpam_err != PAM_SUCCESS) 463 goto auth_fail; 464 sshpam_err = pam_authenticate(sshpam_handle, flags); 465 if (sshpam_err == PAM_MAXTRIES) 466 sshpam_set_maxtries_reached(1); 467 if (sshpam_err != PAM_SUCCESS) 468 goto auth_fail; 469 470 if (!do_pam_account()) { 471 sshpam_err = PAM_ACCT_EXPIRED; 472 goto auth_fail; 473 } 474 if (sshpam_authctxt->force_pwchange) { 475 sshpam_err = pam_chauthtok(sshpam_handle, 476 PAM_CHANGE_EXPIRED_AUTHTOK); 477 if (sshpam_err != PAM_SUCCESS) 478 goto auth_fail; 479 sshpam_password_change_required(0); 480 } 481 482 buffer_put_cstring(&buffer, "OK"); 483 484 #ifndef UNSUPPORTED_POSIX_THREADS_HACK 485 /* Export variables set by do_pam_account */ 486 buffer_put_int(&buffer, sshpam_account_status); 487 buffer_put_int(&buffer, sshpam_authctxt->force_pwchange); 488 489 /* Export any environment strings set in child */ 490 for(i = 0; environ[i] != NULL; i++) 491 ; /* Count */ 492 buffer_put_int(&buffer, i); 493 for(i = 0; environ[i] != NULL; i++) 494 buffer_put_cstring(&buffer, environ[i]); 495 496 /* Export any environment strings set by PAM in child */ 497 env_from_pam = pam_getenvlist(sshpam_handle); 498 for(i = 0; env_from_pam != NULL && env_from_pam[i] != NULL; i++) 499 ; /* Count */ 500 buffer_put_int(&buffer, i); 501 for(i = 0; env_from_pam != NULL && env_from_pam[i] != NULL; i++) 502 buffer_put_cstring(&buffer, env_from_pam[i]); 503 #endif /* UNSUPPORTED_POSIX_THREADS_HACK */ 504 505 /* XXX - can't do much about an error here */ 506 ssh_msg_send(ctxt->pam_csock, sshpam_err, &buffer); 507 buffer_free(&buffer); 508 pthread_exit(NULL); 509 510 auth_fail: 511 buffer_put_cstring(&buffer, 512 pam_strerror(sshpam_handle, sshpam_err)); 513 /* XXX - can't do much about an error here */ 514 if (sshpam_err == PAM_ACCT_EXPIRED) 515 ssh_msg_send(ctxt->pam_csock, PAM_ACCT_EXPIRED, &buffer); 516 else if (sshpam_maxtries_reached) 517 ssh_msg_send(ctxt->pam_csock, PAM_MAXTRIES, &buffer); 518 else 519 ssh_msg_send(ctxt->pam_csock, PAM_AUTH_ERR, &buffer); 520 buffer_free(&buffer); 521 pthread_exit(NULL); 522 523 return (NULL); /* Avoid warning for non-pthread case */ 524 } 525 526 void 527 sshpam_thread_cleanup(void) 528 { 529 struct pam_ctxt *ctxt = cleanup_ctxt; 530 531 debug3("PAM: %s entering", __func__); 532 if (ctxt != NULL && ctxt->pam_thread != 0) { 533 pthread_cancel(ctxt->pam_thread); 534 pthread_join(ctxt->pam_thread, NULL); 535 close(ctxt->pam_psock); 536 close(ctxt->pam_csock); 537 memset(ctxt, 0, sizeof(*ctxt)); 538 cleanup_ctxt = NULL; 539 } 540 } 541 542 static int 543 sshpam_null_conv(int n, sshpam_const struct pam_message **msg, 544 struct pam_response **resp, void *data) 545 { 546 debug3("PAM: %s entering, %d messages", __func__, n); 547 return (PAM_CONV_ERR); 548 } 549 550 static struct pam_conv null_conv = { sshpam_null_conv, NULL }; 551 552 static int 553 sshpam_store_conv(int n, sshpam_const struct pam_message **msg, 554 struct pam_response **resp, void *data) 555 { 556 struct pam_response *reply; 557 int i; 558 size_t len; 559 560 debug3("PAM: %s called with %d messages", __func__, n); 561 *resp = NULL; 562 563 if (n <= 0 || n > PAM_MAX_NUM_MSG) 564 return (PAM_CONV_ERR); 565 566 if ((reply = calloc(n, sizeof(*reply))) == NULL) 567 return (PAM_CONV_ERR); 568 569 for (i = 0; i < n; ++i) { 570 switch (PAM_MSG_MEMBER(msg, i, msg_style)) { 571 case PAM_ERROR_MSG: 572 case PAM_TEXT_INFO: 573 len = strlen(PAM_MSG_MEMBER(msg, i, msg)); 574 buffer_append(&loginmsg, PAM_MSG_MEMBER(msg, i, msg), len); 575 buffer_append(&loginmsg, "\n", 1 ); 576 reply[i].resp_retcode = PAM_SUCCESS; 577 break; 578 default: 579 goto fail; 580 } 581 } 582 *resp = reply; 583 return (PAM_SUCCESS); 584 585 fail: 586 for(i = 0; i < n; i++) { 587 free(reply[i].resp); 588 } 589 free(reply); 590 return (PAM_CONV_ERR); 591 } 592 593 static struct pam_conv store_conv = { sshpam_store_conv, NULL }; 594 595 void 596 sshpam_cleanup(void) 597 { 598 if (sshpam_handle == NULL || (use_privsep && !mm_is_monitor())) 599 return; 600 debug("PAM: cleanup"); 601 pam_set_item(sshpam_handle, PAM_CONV, (const void *)&null_conv); 602 if (sshpam_session_open) { 603 debug("PAM: closing session"); 604 pam_close_session(sshpam_handle, PAM_SILENT); 605 sshpam_session_open = 0; 606 } 607 if (sshpam_cred_established) { 608 debug("PAM: deleting credentials"); 609 pam_setcred(sshpam_handle, PAM_DELETE_CRED); 610 sshpam_cred_established = 0; 611 } 612 sshpam_authenticated = 0; 613 pam_end(sshpam_handle, sshpam_err); 614 sshpam_handle = NULL; 615 } 616 617 static int 618 sshpam_init(Authctxt *authctxt) 619 { 620 const char *pam_rhost, *pam_user, *user = authctxt->user; 621 const char **ptr_pam_user = &pam_user; 622 struct ssh *ssh = active_state; /* XXX */ 623 624 if (sshpam_handle != NULL) { 625 /* We already have a PAM context; check if the user matches */ 626 sshpam_err = pam_get_item(sshpam_handle, 627 PAM_USER, (sshpam_const void **)ptr_pam_user); 628 if (sshpam_err == PAM_SUCCESS && strcmp(user, pam_user) == 0) 629 return (0); 630 pam_end(sshpam_handle, sshpam_err); 631 sshpam_handle = NULL; 632 } 633 debug("PAM: initializing for \"%s\"", user); 634 sshpam_err = 635 pam_start(SSHD_PAM_SERVICE, user, &store_conv, &sshpam_handle); 636 sshpam_authctxt = authctxt; 637 638 if (sshpam_err != PAM_SUCCESS) { 639 pam_end(sshpam_handle, sshpam_err); 640 sshpam_handle = NULL; 641 return (-1); 642 } 643 pam_rhost = auth_get_canonical_hostname(ssh, options.use_dns); 644 debug("PAM: setting PAM_RHOST to \"%s\"", pam_rhost); 645 sshpam_err = pam_set_item(sshpam_handle, PAM_RHOST, pam_rhost); 646 if (sshpam_err != PAM_SUCCESS) { 647 pam_end(sshpam_handle, sshpam_err); 648 sshpam_handle = NULL; 649 return (-1); 650 } 651 #ifdef PAM_TTY_KLUDGE 652 /* 653 * Some silly PAM modules (e.g. pam_time) require a TTY to operate. 654 * sshd doesn't set the tty until too late in the auth process and 655 * may not even set one (for tty-less connections) 656 */ 657 debug("PAM: setting PAM_TTY to \"ssh\""); 658 sshpam_err = pam_set_item(sshpam_handle, PAM_TTY, "ssh"); 659 if (sshpam_err != PAM_SUCCESS) { 660 pam_end(sshpam_handle, sshpam_err); 661 sshpam_handle = NULL; 662 return (-1); 663 } 664 #endif 665 return (0); 666 } 667 668 static void * 669 sshpam_init_ctx(Authctxt *authctxt) 670 { 671 struct pam_ctxt *ctxt; 672 int socks[2]; 673 674 debug3("PAM: %s entering", __func__); 675 /* 676 * Refuse to start if we don't have PAM enabled or do_pam_account 677 * has previously failed. 678 */ 679 if (!options.use_pam || sshpam_account_status == 0) 680 return NULL; 681 682 /* Initialize PAM */ 683 if (sshpam_init(authctxt) == -1) { 684 error("PAM: initialization failed"); 685 return (NULL); 686 } 687 688 ctxt = xcalloc(1, sizeof *ctxt); 689 690 /* Start the authentication thread */ 691 if (socketpair(AF_UNIX, SOCK_STREAM, PF_UNSPEC, socks) == -1) { 692 error("PAM: failed create sockets: %s", strerror(errno)); 693 free(ctxt); 694 return (NULL); 695 } 696 ctxt->pam_psock = socks[0]; 697 ctxt->pam_csock = socks[1]; 698 if (pthread_create(&ctxt->pam_thread, NULL, sshpam_thread, ctxt) == -1) { 699 error("PAM: failed to start authentication thread: %s", 700 strerror(errno)); 701 close(socks[0]); 702 close(socks[1]); 703 free(ctxt); 704 return (NULL); 705 } 706 cleanup_ctxt = ctxt; 707 return (ctxt); 708 } 709 710 static int 711 sshpam_query(void *ctx, char **name, char **info, 712 u_int *num, char ***prompts, u_int **echo_on) 713 { 714 struct ssh *ssh = active_state; /* XXX */ 715 Buffer buffer; 716 struct pam_ctxt *ctxt = ctx; 717 size_t plen; 718 u_char type; 719 char *msg; 720 size_t len, mlen; 721 722 debug3("PAM: %s entering", __func__); 723 buffer_init(&buffer); 724 *name = xstrdup(""); 725 *info = xstrdup(""); 726 *prompts = xmalloc(sizeof(char *)); 727 **prompts = NULL; 728 plen = 0; 729 *echo_on = xmalloc(sizeof(u_int)); 730 while (ssh_msg_recv(ctxt->pam_psock, &buffer) == 0) { 731 type = buffer_get_char(&buffer); 732 msg = buffer_get_string(&buffer, NULL); 733 mlen = strlen(msg); 734 switch (type) { 735 case PAM_PROMPT_ECHO_ON: 736 case PAM_PROMPT_ECHO_OFF: 737 *num = 1; 738 len = plen + mlen + 1; 739 **prompts = xreallocarray(**prompts, 1, len); 740 strlcpy(**prompts + plen, msg, len - plen); 741 plen += mlen; 742 **echo_on = (type == PAM_PROMPT_ECHO_ON); 743 free(msg); 744 return (0); 745 case PAM_ERROR_MSG: 746 case PAM_TEXT_INFO: 747 /* accumulate messages */ 748 len = plen + mlen + 2; 749 **prompts = xreallocarray(**prompts, 1, len); 750 strlcpy(**prompts + plen, msg, len - plen); 751 plen += mlen; 752 strlcat(**prompts + plen, "\n", len - plen); 753 plen++; 754 free(msg); 755 break; 756 case PAM_ACCT_EXPIRED: 757 case PAM_MAXTRIES: 758 if (type == PAM_ACCT_EXPIRED) 759 sshpam_account_status = 0; 760 if (type == PAM_MAXTRIES) 761 sshpam_set_maxtries_reached(1); 762 /* FALLTHROUGH */ 763 case PAM_AUTH_ERR: 764 debug3("PAM: %s", pam_strerror(sshpam_handle, type)); 765 if (**prompts != NULL && strlen(**prompts) != 0) { 766 *info = **prompts; 767 **prompts = NULL; 768 *num = 0; 769 **echo_on = 0; 770 ctxt->pam_done = -1; 771 free(msg); 772 return 0; 773 } 774 /* FALLTHROUGH */ 775 case PAM_SUCCESS: 776 if (**prompts != NULL) { 777 /* drain any accumulated messages */ 778 debug("PAM: %s", **prompts); 779 buffer_append(&loginmsg, **prompts, 780 strlen(**prompts)); 781 free(**prompts); 782 **prompts = NULL; 783 } 784 if (type == PAM_SUCCESS) { 785 if (!sshpam_authctxt->valid || 786 (sshpam_authctxt->pw->pw_uid == 0 && 787 options.permit_root_login != PERMIT_YES)) 788 fatal("Internal error: PAM auth " 789 "succeeded when it should have " 790 "failed"); 791 import_environments(&buffer); 792 *num = 0; 793 **echo_on = 0; 794 ctxt->pam_done = 1; 795 free(msg); 796 return (0); 797 } 798 error("PAM: %s for %s%.100s from %.100s", msg, 799 sshpam_authctxt->valid ? "" : "illegal user ", 800 sshpam_authctxt->user, 801 auth_get_canonical_hostname(ssh, options.use_dns)); 802 /* FALLTHROUGH */ 803 default: 804 *num = 0; 805 **echo_on = 0; 806 free(msg); 807 ctxt->pam_done = -1; 808 return (-1); 809 } 810 } 811 return (-1); 812 } 813 814 /* 815 * Returns a junk password of identical length to that the user supplied. 816 * Used to mitigate timing attacks against crypt(3)/PAM stacks that 817 * vary processing time in proportion to password length. 818 */ 819 static char * 820 fake_password(const char *wire_password) 821 { 822 const char junk[] = "\b\n\r\177INCORRECT"; 823 char *ret = NULL; 824 size_t i, l = wire_password != NULL ? strlen(wire_password) : 0; 825 826 if (l >= INT_MAX) 827 fatal("%s: password length too long: %zu", __func__, l); 828 829 ret = malloc(l + 1); 830 if (ret == NULL) 831 return NULL; 832 for (i = 0; i < l; i++) 833 ret[i] = junk[i % (sizeof(junk) - 1)]; 834 ret[i] = '\0'; 835 return ret; 836 } 837 838 /* XXX - see also comment in auth-chall.c:verify_response */ 839 static int 840 sshpam_respond(void *ctx, u_int num, char **resp) 841 { 842 Buffer buffer; 843 struct pam_ctxt *ctxt = ctx; 844 char *fake; 845 846 debug2("PAM: %s entering, %u responses", __func__, num); 847 switch (ctxt->pam_done) { 848 case 1: 849 sshpam_authenticated = 1; 850 return (0); 851 case 0: 852 break; 853 default: 854 return (-1); 855 } 856 if (num != 1) { 857 error("PAM: expected one response, got %u", num); 858 return (-1); 859 } 860 buffer_init(&buffer); 861 if (sshpam_authctxt->valid && 862 (sshpam_authctxt->pw->pw_uid != 0 || 863 options.permit_root_login == PERMIT_YES)) 864 buffer_put_cstring(&buffer, *resp); 865 else { 866 fake = fake_password(*resp); 867 buffer_put_cstring(&buffer, fake); 868 free(fake); 869 } 870 if (ssh_msg_send(ctxt->pam_psock, PAM_AUTHTOK, &buffer) == -1) { 871 buffer_free(&buffer); 872 return (-1); 873 } 874 buffer_free(&buffer); 875 return (1); 876 } 877 878 static void 879 sshpam_free_ctx(void *ctxtp) 880 { 881 struct pam_ctxt *ctxt = ctxtp; 882 883 debug3("PAM: %s entering", __func__); 884 sshpam_thread_cleanup(); 885 free(ctxt); 886 /* 887 * We don't call sshpam_cleanup() here because we may need the PAM 888 * handle at a later stage, e.g. when setting up a session. It's 889 * still on the cleanup list, so pam_end() *will* be called before 890 * the server process terminates. 891 */ 892 } 893 894 KbdintDevice sshpam_device = { 895 "pam", 896 sshpam_init_ctx, 897 sshpam_query, 898 sshpam_respond, 899 sshpam_free_ctx 900 }; 901 902 KbdintDevice mm_sshpam_device = { 903 "pam", 904 mm_sshpam_init_ctx, 905 mm_sshpam_query, 906 mm_sshpam_respond, 907 mm_sshpam_free_ctx 908 }; 909 910 /* 911 * This replaces auth-pam.c 912 */ 913 void 914 start_pam(Authctxt *authctxt) 915 { 916 if (!options.use_pam) 917 fatal("PAM: initialisation requested when UsePAM=no"); 918 919 if (sshpam_init(authctxt) == -1) 920 fatal("PAM: initialisation failed"); 921 } 922 923 void 924 finish_pam(void) 925 { 926 sshpam_cleanup(); 927 } 928 929 static void 930 expose_authinfo(const char *caller) 931 { 932 char *auth_info; 933 934 /* 935 * Expose authentication information to PAM. 936 * The enviornment variable is versioned. Please increment the 937 * version suffix if the format of session_info changes. 938 */ 939 if (sshpam_authctxt->session_info == NULL) 940 auth_info = xstrdup(""); 941 else if ((auth_info = sshbuf_dup_string( 942 sshpam_authctxt->session_info)) == NULL) 943 fatal("%s: sshbuf_dup_string failed", __func__); 944 945 debug2("%s: auth information in SSH_AUTH_INFO_0", caller); 946 do_pam_putenv("SSH_AUTH_INFO_0", auth_info); 947 free(auth_info); 948 } 949 950 u_int 951 do_pam_account(void) 952 { 953 debug("%s: called", __func__); 954 if (sshpam_account_status != -1) 955 return (sshpam_account_status); 956 957 expose_authinfo(__func__); 958 959 sshpam_err = pam_acct_mgmt(sshpam_handle, 0); 960 debug3("PAM: %s pam_acct_mgmt = %d (%s)", __func__, sshpam_err, 961 pam_strerror(sshpam_handle, sshpam_err)); 962 963 if (sshpam_err != PAM_SUCCESS && sshpam_err != PAM_NEW_AUTHTOK_REQD) { 964 sshpam_account_status = 0; 965 return (sshpam_account_status); 966 } 967 968 if (sshpam_err == PAM_NEW_AUTHTOK_REQD) 969 sshpam_password_change_required(1); 970 971 sshpam_account_status = 1; 972 return (sshpam_account_status); 973 } 974 975 void 976 do_pam_setcred(int init) 977 { 978 sshpam_err = pam_set_item(sshpam_handle, PAM_CONV, 979 (const void *)&store_conv); 980 if (sshpam_err != PAM_SUCCESS) 981 fatal("PAM: failed to set PAM_CONV: %s", 982 pam_strerror(sshpam_handle, sshpam_err)); 983 if (init) { 984 debug("PAM: establishing credentials"); 985 sshpam_err = pam_setcred(sshpam_handle, PAM_ESTABLISH_CRED); 986 } else { 987 debug("PAM: reinitializing credentials"); 988 sshpam_err = pam_setcred(sshpam_handle, PAM_REINITIALIZE_CRED); 989 } 990 if (sshpam_err == PAM_SUCCESS) { 991 sshpam_cred_established = 1; 992 return; 993 } 994 if (sshpam_authenticated) 995 fatal("PAM: pam_setcred(): %s", 996 pam_strerror(sshpam_handle, sshpam_err)); 997 else 998 debug("PAM: pam_setcred(): %s", 999 pam_strerror(sshpam_handle, sshpam_err)); 1000 } 1001 1002 static int 1003 sshpam_tty_conv(int n, sshpam_const struct pam_message **msg, 1004 struct pam_response **resp, void *data) 1005 { 1006 char input[PAM_MAX_MSG_SIZE]; 1007 struct pam_response *reply; 1008 int i; 1009 1010 debug3("PAM: %s called with %d messages", __func__, n); 1011 1012 *resp = NULL; 1013 1014 if (n <= 0 || n > PAM_MAX_NUM_MSG || !isatty(STDIN_FILENO)) 1015 return (PAM_CONV_ERR); 1016 1017 if ((reply = calloc(n, sizeof(*reply))) == NULL) 1018 return (PAM_CONV_ERR); 1019 1020 for (i = 0; i < n; ++i) { 1021 switch (PAM_MSG_MEMBER(msg, i, msg_style)) { 1022 case PAM_PROMPT_ECHO_OFF: 1023 reply[i].resp = 1024 read_passphrase(PAM_MSG_MEMBER(msg, i, msg), 1025 RP_ALLOW_STDIN); 1026 reply[i].resp_retcode = PAM_SUCCESS; 1027 break; 1028 case PAM_PROMPT_ECHO_ON: 1029 fprintf(stderr, "%s\n", PAM_MSG_MEMBER(msg, i, msg)); 1030 if (fgets(input, sizeof input, stdin) == NULL) 1031 input[0] = '\0'; 1032 if ((reply[i].resp = strdup(input)) == NULL) 1033 goto fail; 1034 reply[i].resp_retcode = PAM_SUCCESS; 1035 break; 1036 case PAM_ERROR_MSG: 1037 case PAM_TEXT_INFO: 1038 fprintf(stderr, "%s\n", PAM_MSG_MEMBER(msg, i, msg)); 1039 reply[i].resp_retcode = PAM_SUCCESS; 1040 break; 1041 default: 1042 goto fail; 1043 } 1044 } 1045 *resp = reply; 1046 return (PAM_SUCCESS); 1047 1048 fail: 1049 for(i = 0; i < n; i++) { 1050 free(reply[i].resp); 1051 } 1052 free(reply); 1053 return (PAM_CONV_ERR); 1054 } 1055 1056 static struct pam_conv tty_conv = { sshpam_tty_conv, NULL }; 1057 1058 /* 1059 * XXX this should be done in the authentication phase, but ssh1 doesn't 1060 * support that 1061 */ 1062 void 1063 do_pam_chauthtok(void) 1064 { 1065 if (use_privsep) 1066 fatal("Password expired (unable to change with privsep)"); 1067 sshpam_err = pam_set_item(sshpam_handle, PAM_CONV, 1068 (const void *)&tty_conv); 1069 if (sshpam_err != PAM_SUCCESS) 1070 fatal("PAM: failed to set PAM_CONV: %s", 1071 pam_strerror(sshpam_handle, sshpam_err)); 1072 debug("PAM: changing password"); 1073 sshpam_err = pam_chauthtok(sshpam_handle, PAM_CHANGE_EXPIRED_AUTHTOK); 1074 if (sshpam_err != PAM_SUCCESS) 1075 fatal("PAM: pam_chauthtok(): %s", 1076 pam_strerror(sshpam_handle, sshpam_err)); 1077 } 1078 1079 void 1080 do_pam_session(void) 1081 { 1082 debug3("PAM: opening session"); 1083 1084 expose_authinfo(__func__); 1085 1086 sshpam_err = pam_set_item(sshpam_handle, PAM_CONV, 1087 (const void *)&store_conv); 1088 if (sshpam_err != PAM_SUCCESS) 1089 fatal("PAM: failed to set PAM_CONV: %s", 1090 pam_strerror(sshpam_handle, sshpam_err)); 1091 sshpam_err = pam_open_session(sshpam_handle, 0); 1092 if (sshpam_err == PAM_SUCCESS) 1093 sshpam_session_open = 1; 1094 else { 1095 sshpam_session_open = 0; 1096 disable_forwarding(); 1097 error("PAM: pam_open_session(): %s", 1098 pam_strerror(sshpam_handle, sshpam_err)); 1099 } 1100 1101 } 1102 1103 int 1104 is_pam_session_open(void) 1105 { 1106 return sshpam_session_open; 1107 } 1108 1109 /* 1110 * Set a PAM environment string. We need to do this so that the session 1111 * modules can handle things like Kerberos/GSI credentials that appear 1112 * during the ssh authentication process. 1113 */ 1114 int 1115 do_pam_putenv(char *name, char *value) 1116 { 1117 int ret = 1; 1118 #ifdef HAVE_PAM_PUTENV 1119 char *compound; 1120 size_t len; 1121 1122 len = strlen(name) + strlen(value) + 2; 1123 compound = xmalloc(len); 1124 1125 snprintf(compound, len, "%s=%s", name, value); 1126 ret = pam_putenv(sshpam_handle, compound); 1127 free(compound); 1128 #endif 1129 1130 return (ret); 1131 } 1132 1133 char ** 1134 fetch_pam_child_environment(void) 1135 { 1136 return sshpam_env; 1137 } 1138 1139 char ** 1140 fetch_pam_environment(void) 1141 { 1142 return (pam_getenvlist(sshpam_handle)); 1143 } 1144 1145 void 1146 free_pam_environment(char **env) 1147 { 1148 char **envp; 1149 1150 if (env == NULL) 1151 return; 1152 1153 for (envp = env; *envp; envp++) 1154 free(*envp); 1155 free(env); 1156 } 1157 1158 /* 1159 * "Blind" conversation function for password authentication. Assumes that 1160 * echo-off prompts are for the password and stores messages for later 1161 * display. 1162 */ 1163 static int 1164 sshpam_passwd_conv(int n, sshpam_const struct pam_message **msg, 1165 struct pam_response **resp, void *data) 1166 { 1167 struct pam_response *reply; 1168 int i; 1169 size_t len; 1170 1171 debug3("PAM: %s called with %d messages", __func__, n); 1172 1173 *resp = NULL; 1174 1175 if (n <= 0 || n > PAM_MAX_NUM_MSG) 1176 return (PAM_CONV_ERR); 1177 1178 if ((reply = calloc(n, sizeof(*reply))) == NULL) 1179 return (PAM_CONV_ERR); 1180 1181 for (i = 0; i < n; ++i) { 1182 switch (PAM_MSG_MEMBER(msg, i, msg_style)) { 1183 case PAM_PROMPT_ECHO_OFF: 1184 if (sshpam_password == NULL) 1185 goto fail; 1186 if ((reply[i].resp = strdup(sshpam_password)) == NULL) 1187 goto fail; 1188 reply[i].resp_retcode = PAM_SUCCESS; 1189 break; 1190 case PAM_ERROR_MSG: 1191 case PAM_TEXT_INFO: 1192 len = strlen(PAM_MSG_MEMBER(msg, i, msg)); 1193 if (len > 0) { 1194 buffer_append(&loginmsg, 1195 PAM_MSG_MEMBER(msg, i, msg), len); 1196 buffer_append(&loginmsg, "\n", 1); 1197 } 1198 if ((reply[i].resp = strdup("")) == NULL) 1199 goto fail; 1200 reply[i].resp_retcode = PAM_SUCCESS; 1201 break; 1202 default: 1203 goto fail; 1204 } 1205 } 1206 *resp = reply; 1207 return (PAM_SUCCESS); 1208 1209 fail: 1210 for(i = 0; i < n; i++) { 1211 free(reply[i].resp); 1212 } 1213 free(reply); 1214 return (PAM_CONV_ERR); 1215 } 1216 1217 static struct pam_conv passwd_conv = { sshpam_passwd_conv, NULL }; 1218 1219 /* 1220 * Attempt password authentication via PAM 1221 */ 1222 int 1223 sshpam_auth_passwd(Authctxt *authctxt, const char *password) 1224 { 1225 int flags = (options.permit_empty_passwd == 0 ? 1226 PAM_DISALLOW_NULL_AUTHTOK : 0); 1227 char *fake = NULL; 1228 1229 if (!options.use_pam || sshpam_handle == NULL) 1230 fatal("PAM: %s called when PAM disabled or failed to " 1231 "initialise.", __func__); 1232 1233 sshpam_password = password; 1234 sshpam_authctxt = authctxt; 1235 1236 /* 1237 * If the user logging in is invalid, or is root but is not permitted 1238 * by PermitRootLogin, use an invalid password to prevent leaking 1239 * information via timing (eg if the PAM config has a delay on fail). 1240 */ 1241 if (!authctxt->valid || (authctxt->pw->pw_uid == 0 && 1242 options.permit_root_login != PERMIT_YES)) 1243 sshpam_password = fake = fake_password(password); 1244 1245 sshpam_err = pam_set_item(sshpam_handle, PAM_CONV, 1246 (const void *)&passwd_conv); 1247 if (sshpam_err != PAM_SUCCESS) 1248 fatal("PAM: %s: failed to set PAM_CONV: %s", __func__, 1249 pam_strerror(sshpam_handle, sshpam_err)); 1250 1251 sshpam_err = pam_authenticate(sshpam_handle, flags); 1252 sshpam_password = NULL; 1253 free(fake); 1254 if (sshpam_err == PAM_MAXTRIES) 1255 sshpam_set_maxtries_reached(1); 1256 if (sshpam_err == PAM_SUCCESS && authctxt->valid) { 1257 debug("PAM: password authentication accepted for %.100s", 1258 authctxt->user); 1259 return 1; 1260 } else { 1261 debug("PAM: password authentication failed for %.100s: %s", 1262 authctxt->valid ? authctxt->user : "an illegal user", 1263 pam_strerror(sshpam_handle, sshpam_err)); 1264 return 0; 1265 } 1266 } 1267 1268 int 1269 sshpam_get_maxtries_reached(void) 1270 { 1271 return sshpam_maxtries_reached; 1272 } 1273 1274 void 1275 sshpam_set_maxtries_reached(int reached) 1276 { 1277 if (reached == 0 || sshpam_maxtries_reached) 1278 return; 1279 sshpam_maxtries_reached = 1; 1280 options.password_authentication = 0; 1281 options.kbd_interactive_authentication = 0; 1282 options.challenge_response_authentication = 0; 1283 } 1284 #endif /* USE_PAM */ 1285