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 (at) mindrot.org> 33 * Copyright (c) 2003,2004 Darren Tucker <dtucker (at) 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 int compat20; 110 extern u_int utmp_len; 111 112 /* so we don't silently change behaviour */ 113 #ifdef USE_POSIX_THREADS 114 # error "USE_POSIX_THREADS replaced by UNSUPPORTED_POSIX_THREADS_HACK" 115 #endif 116 117 /* 118 * Formerly known as USE_POSIX_THREADS, using this is completely unsupported 119 * and generally a bad idea. Use at own risk and do not expect support if 120 * this breaks. 121 */ 122 #ifdef UNSUPPORTED_POSIX_THREADS_HACK 123 #include <pthread.h> 124 /* 125 * Avoid namespace clash when *not* using pthreads for systems *with* 126 * pthreads, which unconditionally define pthread_t via sys/types.h 127 * (e.g. Linux) 128 */ 129 typedef pthread_t sp_pthread_t; 130 #else 131 typedef pid_t sp_pthread_t; 132 #endif 133 134 struct pam_ctxt { 135 sp_pthread_t pam_thread; 136 int pam_psock; 137 int pam_csock; 138 int pam_done; 139 }; 140 141 static void sshpam_free_ctx(void *); 142 static struct pam_ctxt *cleanup_ctxt; 143 144 #ifndef UNSUPPORTED_POSIX_THREADS_HACK 145 /* 146 * Simulate threads with processes. 147 */ 148 149 static int sshpam_thread_status = -1; 150 static mysig_t sshpam_oldsig; 151 152 static void 153 sshpam_sigchld_handler(int sig) 154 { 155 signal(SIGCHLD, SIG_DFL); 156 if (cleanup_ctxt == NULL) 157 return; /* handler called after PAM cleanup, shouldn't happen */ 158 if (waitpid(cleanup_ctxt->pam_thread, &sshpam_thread_status, WNOHANG) 159 <= 0) { 160 /* PAM thread has not exitted, privsep slave must have */ 161 kill(cleanup_ctxt->pam_thread, SIGTERM); 162 while (waitpid(cleanup_ctxt->pam_thread, 163 &sshpam_thread_status, 0) == -1) { 164 if (errno == EINTR) 165 continue; 166 return; 167 } 168 } 169 if (WIFSIGNALED(sshpam_thread_status) && 170 WTERMSIG(sshpam_thread_status) == SIGTERM) 171 return; /* terminated by pthread_cancel */ 172 if (!WIFEXITED(sshpam_thread_status)) 173 sigdie("PAM: authentication thread exited unexpectedly"); 174 if (WEXITSTATUS(sshpam_thread_status) != 0) 175 sigdie("PAM: authentication thread exited uncleanly"); 176 } 177 178 /* ARGSUSED */ 179 static void 180 pthread_exit(void *value) 181 { 182 _exit(0); 183 } 184 185 /* ARGSUSED */ 186 static int 187 pthread_create(sp_pthread_t *thread, const void *attr, 188 void *(*thread_start)(void *), void *arg) 189 { 190 pid_t pid; 191 struct pam_ctxt *ctx = arg; 192 193 sshpam_thread_status = -1; 194 switch ((pid = fork())) { 195 case -1: 196 error("fork(): %s", strerror(errno)); 197 return (-1); 198 case 0: 199 close(ctx->pam_psock); 200 ctx->pam_psock = -1; 201 thread_start(arg); 202 _exit(1); 203 default: 204 *thread = pid; 205 close(ctx->pam_csock); 206 ctx->pam_csock = -1; 207 sshpam_oldsig = signal(SIGCHLD, sshpam_sigchld_handler); 208 return (0); 209 } 210 } 211 212 static int 213 pthread_cancel(sp_pthread_t thread) 214 { 215 signal(SIGCHLD, sshpam_oldsig); 216 return (kill(thread, SIGTERM)); 217 } 218 219 /* ARGSUSED */ 220 static int 221 pthread_join(sp_pthread_t thread, void **value) 222 { 223 int status; 224 225 if (sshpam_thread_status != -1) 226 return (sshpam_thread_status); 227 signal(SIGCHLD, sshpam_oldsig); 228 while (waitpid(thread, &status, 0) == -1) { 229 if (errno == EINTR) 230 continue; 231 fatal("%s: waitpid: %s", __func__, strerror(errno)); 232 } 233 return (status); 234 } 235 #endif 236 237 238 static pam_handle_t *sshpam_handle = NULL; 239 static int sshpam_err = 0; 240 static int sshpam_authenticated = 0; 241 static int sshpam_session_open = 0; 242 static int sshpam_cred_established = 0; 243 static int sshpam_account_status = -1; 244 static int sshpam_maxtries_reached = 0; 245 static char **sshpam_env = NULL; 246 static Authctxt *sshpam_authctxt = NULL; 247 static const char *sshpam_password = NULL; 248 249 /* Some PAM implementations don't implement this */ 250 #ifndef HAVE_PAM_GETENVLIST 251 static char ** 252 pam_getenvlist(pam_handle_t *pamh) 253 { 254 /* 255 * XXX - If necessary, we can still support envrionment passing 256 * for platforms without pam_getenvlist by searching for known 257 * env vars (e.g. KRB5CCNAME) from the PAM environment. 258 */ 259 return NULL; 260 } 261 #endif 262 263 /* 264 * Some platforms, notably Solaris, do not enforce password complexity 265 * rules during pam_chauthtok() if the real uid of the calling process 266 * is 0, on the assumption that it's being called by "passwd" run by root. 267 * This wraps pam_chauthtok and sets/restore the real uid so PAM will do 268 * the right thing. 269 */ 270 #ifdef SSHPAM_CHAUTHTOK_NEEDS_RUID 271 static int 272 sshpam_chauthtok_ruid(pam_handle_t *pamh, int flags) 273 { 274 int result; 275 276 if (sshpam_authctxt == NULL) 277 fatal("PAM: sshpam_authctxt not initialized"); 278 if (setreuid(sshpam_authctxt->pw->pw_uid, -1) == -1) 279 fatal("%s: setreuid failed: %s", __func__, strerror(errno)); 280 result = pam_chauthtok(pamh, flags); 281 if (setreuid(0, -1) == -1) 282 fatal("%s: setreuid failed: %s", __func__, strerror(errno)); 283 return result; 284 } 285 # define pam_chauthtok(a,b) (sshpam_chauthtok_ruid((a), (b))) 286 #endif 287 288 void 289 sshpam_password_change_required(int reqd) 290 { 291 debug3("%s %d", __func__, reqd); 292 if (sshpam_authctxt == NULL) 293 fatal("%s: PAM authctxt not initialized", __func__); 294 sshpam_authctxt->force_pwchange = reqd; 295 if (reqd) { 296 no_port_forwarding_flag |= 2; 297 no_agent_forwarding_flag |= 2; 298 no_x11_forwarding_flag |= 2; 299 } else { 300 no_port_forwarding_flag &= ~2; 301 no_agent_forwarding_flag &= ~2; 302 no_x11_forwarding_flag &= ~2; 303 } 304 } 305 306 /* Import regular and PAM environment from subprocess */ 307 static void 308 import_environments(Buffer *b) 309 { 310 char *env; 311 u_int i, num_env; 312 int err; 313 314 debug3("PAM: %s entering", __func__); 315 316 #ifndef UNSUPPORTED_POSIX_THREADS_HACK 317 /* Import variables set by do_pam_account */ 318 sshpam_account_status = buffer_get_int(b); 319 sshpam_password_change_required(buffer_get_int(b)); 320 321 /* Import environment from subprocess */ 322 num_env = buffer_get_int(b); 323 if (num_env > 1024) 324 fatal("%s: received %u environment variables, expected <= 1024", 325 __func__, num_env); 326 sshpam_env = xcalloc(num_env + 1, sizeof(*sshpam_env)); 327 debug3("PAM: num env strings %d", num_env); 328 for(i = 0; i < num_env; i++) 329 sshpam_env[i] = buffer_get_string(b, NULL); 330 331 sshpam_env[num_env] = NULL; 332 333 /* Import PAM environment from subprocess */ 334 num_env = buffer_get_int(b); 335 debug("PAM: num PAM env strings %d", num_env); 336 for(i = 0; i < num_env; i++) { 337 env = buffer_get_string(b, NULL); 338 339 #ifdef HAVE_PAM_PUTENV 340 /* Errors are not fatal here */ 341 if ((err = pam_putenv(sshpam_handle, env)) != PAM_SUCCESS) { 342 error("PAM: pam_putenv: %s", 343 pam_strerror(sshpam_handle, sshpam_err)); 344 } 345 #endif 346 } 347 #endif 348 } 349 350 /* 351 * Conversation function for authentication thread. 352 */ 353 static int 354 sshpam_thread_conv(int n, sshpam_const struct pam_message **msg, 355 struct pam_response **resp, void *data) 356 { 357 Buffer buffer; 358 struct pam_ctxt *ctxt; 359 struct pam_response *reply; 360 int i; 361 362 debug3("PAM: %s entering, %d messages", __func__, n); 363 *resp = NULL; 364 365 if (data == NULL) { 366 error("PAM: conversation function passed a null context"); 367 return (PAM_CONV_ERR); 368 } 369 ctxt = data; 370 if (n <= 0 || n > PAM_MAX_NUM_MSG) 371 return (PAM_CONV_ERR); 372 373 if ((reply = calloc(n, sizeof(*reply))) == NULL) 374 return (PAM_CONV_ERR); 375 376 buffer_init(&buffer); 377 for (i = 0; i < n; ++i) { 378 switch (PAM_MSG_MEMBER(msg, i, msg_style)) { 379 case PAM_PROMPT_ECHO_OFF: 380 case PAM_PROMPT_ECHO_ON: 381 buffer_put_cstring(&buffer, 382 PAM_MSG_MEMBER(msg, i, msg)); 383 if (ssh_msg_send(ctxt->pam_csock, 384 PAM_MSG_MEMBER(msg, i, msg_style), &buffer) == -1) 385 goto fail; 386 if (ssh_msg_recv(ctxt->pam_csock, &buffer) == -1) 387 goto fail; 388 if (buffer_get_char(&buffer) != PAM_AUTHTOK) 389 goto fail; 390 reply[i].resp = buffer_get_string(&buffer, NULL); 391 break; 392 case PAM_ERROR_MSG: 393 case PAM_TEXT_INFO: 394 buffer_put_cstring(&buffer, 395 PAM_MSG_MEMBER(msg, i, msg)); 396 if (ssh_msg_send(ctxt->pam_csock, 397 PAM_MSG_MEMBER(msg, i, msg_style), &buffer) == -1) 398 goto fail; 399 break; 400 default: 401 goto fail; 402 } 403 buffer_clear(&buffer); 404 } 405 buffer_free(&buffer); 406 *resp = reply; 407 return (PAM_SUCCESS); 408 409 fail: 410 for(i = 0; i < n; i++) { 411 free(reply[i].resp); 412 } 413 free(reply); 414 buffer_free(&buffer); 415 return (PAM_CONV_ERR); 416 } 417 418 /* 419 * Authentication thread. 420 */ 421 static void * 422 sshpam_thread(void *ctxtp) 423 { 424 struct pam_ctxt *ctxt = ctxtp; 425 Buffer buffer; 426 struct pam_conv sshpam_conv; 427 int flags = (options.permit_empty_passwd == 0 ? 428 PAM_DISALLOW_NULL_AUTHTOK : 0); 429 #ifndef UNSUPPORTED_POSIX_THREADS_HACK 430 extern char **environ; 431 char **env_from_pam; 432 u_int i; 433 const char *pam_user; 434 const char **ptr_pam_user = &pam_user; 435 char *tz = getenv("TZ"); 436 437 sshpam_err = pam_get_item(sshpam_handle, PAM_USER, 438 (sshpam_const void **)ptr_pam_user); 439 if (sshpam_err != PAM_SUCCESS) 440 goto auth_fail; 441 442 environ[0] = NULL; 443 if (tz != NULL) 444 if (setenv("TZ", tz, 1) == -1) 445 error("PAM: could not set TZ environment: %s", 446 strerror(errno)); 447 448 if (sshpam_authctxt != NULL) { 449 setproctitle("%s [pam]", 450 sshpam_authctxt->valid ? pam_user : "unknown"); 451 } 452 #endif 453 454 sshpam_conv.conv = sshpam_thread_conv; 455 sshpam_conv.appdata_ptr = ctxt; 456 457 if (sshpam_authctxt == NULL) 458 fatal("%s: PAM authctxt not initialized", __func__); 459 460 buffer_init(&buffer); 461 sshpam_err = pam_set_item(sshpam_handle, PAM_CONV, 462 (const void *)&sshpam_conv); 463 if (sshpam_err != PAM_SUCCESS) 464 goto auth_fail; 465 sshpam_err = pam_authenticate(sshpam_handle, flags); 466 if (sshpam_err == PAM_MAXTRIES) 467 sshpam_set_maxtries_reached(1); 468 if (sshpam_err != PAM_SUCCESS) 469 goto auth_fail; 470 471 if (compat20) { 472 if (!do_pam_account()) { 473 sshpam_err = PAM_ACCT_EXPIRED; 474 goto auth_fail; 475 } 476 if (sshpam_authctxt->force_pwchange) { 477 sshpam_err = pam_chauthtok(sshpam_handle, 478 PAM_CHANGE_EXPIRED_AUTHTOK); 479 if (sshpam_err != PAM_SUCCESS) 480 goto auth_fail; 481 sshpam_password_change_required(0); 482 } 483 } 484 485 buffer_put_cstring(&buffer, "OK"); 486 487 #ifndef UNSUPPORTED_POSIX_THREADS_HACK 488 /* Export variables set by do_pam_account */ 489 buffer_put_int(&buffer, sshpam_account_status); 490 buffer_put_int(&buffer, sshpam_authctxt->force_pwchange); 491 492 /* Export any environment strings set in child */ 493 for(i = 0; environ[i] != NULL; i++) 494 ; /* Count */ 495 buffer_put_int(&buffer, i); 496 for(i = 0; environ[i] != NULL; i++) 497 buffer_put_cstring(&buffer, environ[i]); 498 499 /* Export any environment strings set by PAM in child */ 500 env_from_pam = pam_getenvlist(sshpam_handle); 501 for(i = 0; env_from_pam != NULL && env_from_pam[i] != NULL; i++) 502 ; /* Count */ 503 buffer_put_int(&buffer, i); 504 for(i = 0; env_from_pam != NULL && env_from_pam[i] != NULL; i++) 505 buffer_put_cstring(&buffer, env_from_pam[i]); 506 #endif /* UNSUPPORTED_POSIX_THREADS_HACK */ 507 508 /* XXX - can't do much about an error here */ 509 ssh_msg_send(ctxt->pam_csock, sshpam_err, &buffer); 510 buffer_free(&buffer); 511 pthread_exit(NULL); 512 513 auth_fail: 514 buffer_put_cstring(&buffer, 515 pam_strerror(sshpam_handle, sshpam_err)); 516 /* XXX - can't do much about an error here */ 517 if (sshpam_err == PAM_ACCT_EXPIRED) 518 ssh_msg_send(ctxt->pam_csock, PAM_ACCT_EXPIRED, &buffer); 519 else if (sshpam_maxtries_reached) 520 ssh_msg_send(ctxt->pam_csock, PAM_MAXTRIES, &buffer); 521 else 522 ssh_msg_send(ctxt->pam_csock, PAM_AUTH_ERR, &buffer); 523 buffer_free(&buffer); 524 pthread_exit(NULL); 525 526 return (NULL); /* Avoid warning for non-pthread case */ 527 } 528 529 void 530 sshpam_thread_cleanup(void) 531 { 532 struct pam_ctxt *ctxt = cleanup_ctxt; 533 534 debug3("PAM: %s entering", __func__); 535 if (ctxt != NULL && ctxt->pam_thread != 0) { 536 pthread_cancel(ctxt->pam_thread); 537 pthread_join(ctxt->pam_thread, NULL); 538 close(ctxt->pam_psock); 539 close(ctxt->pam_csock); 540 memset(ctxt, 0, sizeof(*ctxt)); 541 cleanup_ctxt = NULL; 542 } 543 } 544 545 static int 546 sshpam_null_conv(int n, sshpam_const struct pam_message **msg, 547 struct pam_response **resp, void *data) 548 { 549 debug3("PAM: %s entering, %d messages", __func__, n); 550 return (PAM_CONV_ERR); 551 } 552 553 static struct pam_conv null_conv = { sshpam_null_conv, NULL }; 554 555 static int 556 sshpam_store_conv(int n, sshpam_const struct pam_message **msg, 557 struct pam_response **resp, void *data) 558 { 559 struct pam_response *reply; 560 int i; 561 size_t len; 562 563 debug3("PAM: %s called with %d messages", __func__, n); 564 *resp = NULL; 565 566 if (n <= 0 || n > PAM_MAX_NUM_MSG) 567 return (PAM_CONV_ERR); 568 569 if ((reply = calloc(n, sizeof(*reply))) == NULL) 570 return (PAM_CONV_ERR); 571 572 for (i = 0; i < n; ++i) { 573 switch (PAM_MSG_MEMBER(msg, i, msg_style)) { 574 case PAM_ERROR_MSG: 575 case PAM_TEXT_INFO: 576 len = strlen(PAM_MSG_MEMBER(msg, i, msg)); 577 buffer_append(&loginmsg, PAM_MSG_MEMBER(msg, i, msg), len); 578 buffer_append(&loginmsg, "\n", 1 ); 579 reply[i].resp_retcode = PAM_SUCCESS; 580 break; 581 default: 582 goto fail; 583 } 584 } 585 *resp = reply; 586 return (PAM_SUCCESS); 587 588 fail: 589 for(i = 0; i < n; i++) { 590 free(reply[i].resp); 591 } 592 free(reply); 593 return (PAM_CONV_ERR); 594 } 595 596 static struct pam_conv store_conv = { sshpam_store_conv, NULL }; 597 598 void 599 sshpam_cleanup(void) 600 { 601 if (sshpam_handle == NULL || (use_privsep && !mm_is_monitor())) 602 return; 603 debug("PAM: cleanup"); 604 pam_set_item(sshpam_handle, PAM_CONV, (const void *)&null_conv); 605 if (sshpam_session_open) { 606 debug("PAM: closing session"); 607 pam_close_session(sshpam_handle, PAM_SILENT); 608 sshpam_session_open = 0; 609 } 610 if (sshpam_cred_established) { 611 debug("PAM: deleting credentials"); 612 pam_setcred(sshpam_handle, PAM_DELETE_CRED); 613 sshpam_cred_established = 0; 614 } 615 sshpam_authenticated = 0; 616 pam_end(sshpam_handle, sshpam_err); 617 sshpam_handle = NULL; 618 } 619 620 static int 621 sshpam_init(Authctxt *authctxt) 622 { 623 const char *pam_rhost, *pam_user, *user = authctxt->user; 624 const char **ptr_pam_user = &pam_user; 625 struct ssh *ssh = active_state; /* XXX */ 626 627 if (sshpam_handle != NULL) { 628 /* We already have a PAM context; check if the user matches */ 629 sshpam_err = pam_get_item(sshpam_handle, 630 PAM_USER, (sshpam_const void **)ptr_pam_user); 631 if (sshpam_err == PAM_SUCCESS && strcmp(user, pam_user) == 0) 632 return (0); 633 pam_end(sshpam_handle, sshpam_err); 634 sshpam_handle = NULL; 635 } 636 debug("PAM: initializing for \"%s\"", user); 637 sshpam_err = 638 pam_start(SSHD_PAM_SERVICE, user, &store_conv, &sshpam_handle); 639 sshpam_authctxt = authctxt; 640 641 if (sshpam_err != PAM_SUCCESS) { 642 pam_end(sshpam_handle, sshpam_err); 643 sshpam_handle = NULL; 644 return (-1); 645 } 646 pam_rhost = auth_get_canonical_hostname(ssh, options.use_dns); 647 debug("PAM: setting PAM_RHOST to \"%s\"", pam_rhost); 648 sshpam_err = pam_set_item(sshpam_handle, PAM_RHOST, pam_rhost); 649 if (sshpam_err != PAM_SUCCESS) { 650 pam_end(sshpam_handle, sshpam_err); 651 sshpam_handle = NULL; 652 return (-1); 653 } 654 #ifdef PAM_TTY_KLUDGE 655 /* 656 * Some silly PAM modules (e.g. pam_time) require a TTY to operate. 657 * sshd doesn't set the tty until too late in the auth process and 658 * may not even set one (for tty-less connections) 659 */ 660 debug("PAM: setting PAM_TTY to \"ssh\""); 661 sshpam_err = pam_set_item(sshpam_handle, PAM_TTY, "ssh"); 662 if (sshpam_err != PAM_SUCCESS) { 663 pam_end(sshpam_handle, sshpam_err); 664 sshpam_handle = NULL; 665 return (-1); 666 } 667 #endif 668 return (0); 669 } 670 671 static void * 672 sshpam_init_ctx(Authctxt *authctxt) 673 { 674 struct pam_ctxt *ctxt; 675 int socks[2]; 676 677 debug3("PAM: %s entering", __func__); 678 /* 679 * Refuse to start if we don't have PAM enabled or do_pam_account 680 * has previously failed. 681 */ 682 if (!options.use_pam || sshpam_account_status == 0) 683 return NULL; 684 685 /* Initialize PAM */ 686 if (sshpam_init(authctxt) == -1) { 687 error("PAM: initialization failed"); 688 return (NULL); 689 } 690 691 ctxt = xcalloc(1, sizeof *ctxt); 692 693 /* Start the authentication thread */ 694 if (socketpair(AF_UNIX, SOCK_STREAM, PF_UNSPEC, socks) == -1) { 695 error("PAM: failed create sockets: %s", strerror(errno)); 696 free(ctxt); 697 return (NULL); 698 } 699 ctxt->pam_psock = socks[0]; 700 ctxt->pam_csock = socks[1]; 701 if (pthread_create(&ctxt->pam_thread, NULL, sshpam_thread, ctxt) == -1) { 702 error("PAM: failed to start authentication thread: %s", 703 strerror(errno)); 704 close(socks[0]); 705 close(socks[1]); 706 free(ctxt); 707 return (NULL); 708 } 709 cleanup_ctxt = ctxt; 710 return (ctxt); 711 } 712 713 static int 714 sshpam_query(void *ctx, char **name, char **info, 715 u_int *num, char ***prompts, u_int **echo_on) 716 { 717 struct ssh *ssh = active_state; /* XXX */ 718 Buffer buffer; 719 struct pam_ctxt *ctxt = ctx; 720 size_t plen; 721 u_char type; 722 char *msg; 723 size_t len, mlen; 724 725 debug3("PAM: %s entering", __func__); 726 buffer_init(&buffer); 727 *name = xstrdup(""); 728 *info = xstrdup(""); 729 *prompts = xmalloc(sizeof(char *)); 730 **prompts = NULL; 731 plen = 0; 732 *echo_on = xmalloc(sizeof(u_int)); 733 while (ssh_msg_recv(ctxt->pam_psock, &buffer) == 0) { 734 type = buffer_get_char(&buffer); 735 msg = buffer_get_string(&buffer, NULL); 736 mlen = strlen(msg); 737 switch (type) { 738 case PAM_PROMPT_ECHO_ON: 739 case PAM_PROMPT_ECHO_OFF: 740 *num = 1; 741 len = plen + mlen + 1; 742 **prompts = xreallocarray(**prompts, 1, len); 743 strlcpy(**prompts + plen, msg, len - plen); 744 plen += mlen; 745 **echo_on = (type == PAM_PROMPT_ECHO_ON); 746 free(msg); 747 return (0); 748 case PAM_ERROR_MSG: 749 case PAM_TEXT_INFO: 750 /* accumulate messages */ 751 len = plen + mlen + 2; 752 **prompts = xreallocarray(**prompts, 1, len); 753 strlcpy(**prompts + plen, msg, len - plen); 754 plen += mlen; 755 strlcat(**prompts + plen, "\n", len - plen); 756 plen++; 757 free(msg); 758 break; 759 case PAM_ACCT_EXPIRED: 760 case PAM_MAXTRIES: 761 if (type == PAM_ACCT_EXPIRED) 762 sshpam_account_status = 0; 763 if (type == PAM_MAXTRIES) 764 sshpam_set_maxtries_reached(1); 765 /* FALLTHROUGH */ 766 case PAM_AUTH_ERR: 767 debug3("PAM: %s", pam_strerror(sshpam_handle, type)); 768 if (**prompts != NULL && strlen(**prompts) != 0) { 769 *info = **prompts; 770 **prompts = NULL; 771 *num = 0; 772 **echo_on = 0; 773 ctxt->pam_done = -1; 774 free(msg); 775 return 0; 776 } 777 /* FALLTHROUGH */ 778 case PAM_SUCCESS: 779 if (**prompts != NULL) { 780 /* drain any accumulated messages */ 781 debug("PAM: %s", **prompts); 782 buffer_append(&loginmsg, **prompts, 783 strlen(**prompts)); 784 free(**prompts); 785 **prompts = NULL; 786 } 787 if (type == PAM_SUCCESS) { 788 if (!sshpam_authctxt->valid || 789 (sshpam_authctxt->pw->pw_uid == 0 && 790 options.permit_root_login != PERMIT_YES)) 791 fatal("Internal error: PAM auth " 792 "succeeded when it should have " 793 "failed"); 794 import_environments(&buffer); 795 *num = 0; 796 **echo_on = 0; 797 ctxt->pam_done = 1; 798 free(msg); 799 return (0); 800 } 801 error("PAM: %s for %s%.100s from %.100s", msg, 802 sshpam_authctxt->valid ? "" : "illegal user ", 803 sshpam_authctxt->user, 804 auth_get_canonical_hostname(ssh, options.use_dns)); 805 /* FALLTHROUGH */ 806 default: 807 *num = 0; 808 **echo_on = 0; 809 free(msg); 810 ctxt->pam_done = -1; 811 return (-1); 812 } 813 } 814 return (-1); 815 } 816 817 /* 818 * Returns a junk password of identical length to that the user supplied. 819 * Used to mitigate timing attacks against crypt(3)/PAM stacks that 820 * vary processing time in proportion to password length. 821 */ 822 static char * 823 fake_password(const char *wire_password) 824 { 825 const char junk[] = "\b\n\r\177INCORRECT"; 826 char *ret = NULL; 827 size_t i, l = wire_password != NULL ? strlen(wire_password) : 0; 828 829 if (l >= INT_MAX) 830 fatal("%s: password length too long: %zu", __func__, l); 831 832 ret = malloc(l + 1); 833 if (ret == NULL) 834 return NULL; 835 for (i = 0; i < l; i++) 836 ret[i] = junk[i % (sizeof(junk) - 1)]; 837 ret[i] = '\0'; 838 return ret; 839 } 840 841 /* XXX - see also comment in auth-chall.c:verify_response */ 842 static int 843 sshpam_respond(void *ctx, u_int num, char **resp) 844 { 845 Buffer buffer; 846 struct pam_ctxt *ctxt = ctx; 847 char *fake; 848 849 debug2("PAM: %s entering, %u responses", __func__, num); 850 switch (ctxt->pam_done) { 851 case 1: 852 sshpam_authenticated = 1; 853 return (0); 854 case 0: 855 break; 856 default: 857 return (-1); 858 } 859 if (num != 1) { 860 error("PAM: expected one response, got %u", num); 861 return (-1); 862 } 863 buffer_init(&buffer); 864 if (sshpam_authctxt->valid && 865 (sshpam_authctxt->pw->pw_uid != 0 || 866 options.permit_root_login == PERMIT_YES)) 867 buffer_put_cstring(&buffer, *resp); 868 else { 869 fake = fake_password(*resp); 870 buffer_put_cstring(&buffer, fake); 871 free(fake); 872 } 873 if (ssh_msg_send(ctxt->pam_psock, PAM_AUTHTOK, &buffer) == -1) { 874 buffer_free(&buffer); 875 return (-1); 876 } 877 buffer_free(&buffer); 878 return (1); 879 } 880 881 static void 882 sshpam_free_ctx(void *ctxtp) 883 { 884 struct pam_ctxt *ctxt = ctxtp; 885 886 debug3("PAM: %s entering", __func__); 887 sshpam_thread_cleanup(); 888 free(ctxt); 889 /* 890 * We don't call sshpam_cleanup() here because we may need the PAM 891 * handle at a later stage, e.g. when setting up a session. It's 892 * still on the cleanup list, so pam_end() *will* be called before 893 * the server process terminates. 894 */ 895 } 896 897 KbdintDevice sshpam_device = { 898 "pam", 899 sshpam_init_ctx, 900 sshpam_query, 901 sshpam_respond, 902 sshpam_free_ctx 903 }; 904 905 KbdintDevice mm_sshpam_device = { 906 "pam", 907 mm_sshpam_init_ctx, 908 mm_sshpam_query, 909 mm_sshpam_respond, 910 mm_sshpam_free_ctx 911 }; 912 913 /* 914 * This replaces auth-pam.c 915 */ 916 void 917 start_pam(Authctxt *authctxt) 918 { 919 if (!options.use_pam) 920 fatal("PAM: initialisation requested when UsePAM=no"); 921 922 if (sshpam_init(authctxt) == -1) 923 fatal("PAM: initialisation failed"); 924 } 925 926 void 927 finish_pam(void) 928 { 929 sshpam_cleanup(); 930 } 931 932 u_int 933 do_pam_account(void) 934 { 935 debug("%s: called", __func__); 936 if (sshpam_account_status != -1) 937 return (sshpam_account_status); 938 939 sshpam_err = pam_acct_mgmt(sshpam_handle, 0); 940 debug3("PAM: %s pam_acct_mgmt = %d (%s)", __func__, sshpam_err, 941 pam_strerror(sshpam_handle, sshpam_err)); 942 943 if (sshpam_err != PAM_SUCCESS && sshpam_err != PAM_NEW_AUTHTOK_REQD) { 944 sshpam_account_status = 0; 945 return (sshpam_account_status); 946 } 947 948 if (sshpam_err == PAM_NEW_AUTHTOK_REQD) 949 sshpam_password_change_required(1); 950 951 sshpam_account_status = 1; 952 return (sshpam_account_status); 953 } 954 955 void 956 do_pam_setcred(int init) 957 { 958 sshpam_err = pam_set_item(sshpam_handle, PAM_CONV, 959 (const void *)&store_conv); 960 if (sshpam_err != PAM_SUCCESS) 961 fatal("PAM: failed to set PAM_CONV: %s", 962 pam_strerror(sshpam_handle, sshpam_err)); 963 if (init) { 964 debug("PAM: establishing credentials"); 965 sshpam_err = pam_setcred(sshpam_handle, PAM_ESTABLISH_CRED); 966 } else { 967 debug("PAM: reinitializing credentials"); 968 sshpam_err = pam_setcred(sshpam_handle, PAM_REINITIALIZE_CRED); 969 } 970 if (sshpam_err == PAM_SUCCESS) { 971 sshpam_cred_established = 1; 972 return; 973 } 974 if (sshpam_authenticated) 975 fatal("PAM: pam_setcred(): %s", 976 pam_strerror(sshpam_handle, sshpam_err)); 977 else 978 debug("PAM: pam_setcred(): %s", 979 pam_strerror(sshpam_handle, sshpam_err)); 980 } 981 982 static int 983 sshpam_tty_conv(int n, sshpam_const struct pam_message **msg, 984 struct pam_response **resp, void *data) 985 { 986 char input[PAM_MAX_MSG_SIZE]; 987 struct pam_response *reply; 988 int i; 989 990 debug3("PAM: %s called with %d messages", __func__, n); 991 992 *resp = NULL; 993 994 if (n <= 0 || n > PAM_MAX_NUM_MSG || !isatty(STDIN_FILENO)) 995 return (PAM_CONV_ERR); 996 997 if ((reply = calloc(n, sizeof(*reply))) == NULL) 998 return (PAM_CONV_ERR); 999 1000 for (i = 0; i < n; ++i) { 1001 switch (PAM_MSG_MEMBER(msg, i, msg_style)) { 1002 case PAM_PROMPT_ECHO_OFF: 1003 reply[i].resp = 1004 read_passphrase(PAM_MSG_MEMBER(msg, i, msg), 1005 RP_ALLOW_STDIN); 1006 reply[i].resp_retcode = PAM_SUCCESS; 1007 break; 1008 case PAM_PROMPT_ECHO_ON: 1009 fprintf(stderr, "%s\n", PAM_MSG_MEMBER(msg, i, msg)); 1010 if (fgets(input, sizeof input, stdin) == NULL) 1011 input[0] = '\0'; 1012 if ((reply[i].resp = strdup(input)) == NULL) 1013 goto fail; 1014 reply[i].resp_retcode = PAM_SUCCESS; 1015 break; 1016 case PAM_ERROR_MSG: 1017 case PAM_TEXT_INFO: 1018 fprintf(stderr, "%s\n", PAM_MSG_MEMBER(msg, i, msg)); 1019 reply[i].resp_retcode = PAM_SUCCESS; 1020 break; 1021 default: 1022 goto fail; 1023 } 1024 } 1025 *resp = reply; 1026 return (PAM_SUCCESS); 1027 1028 fail: 1029 for(i = 0; i < n; i++) { 1030 free(reply[i].resp); 1031 } 1032 free(reply); 1033 return (PAM_CONV_ERR); 1034 } 1035 1036 static struct pam_conv tty_conv = { sshpam_tty_conv, NULL }; 1037 1038 /* 1039 * XXX this should be done in the authentication phase, but ssh1 doesn't 1040 * support that 1041 */ 1042 void 1043 do_pam_chauthtok(void) 1044 { 1045 if (use_privsep) 1046 fatal("Password expired (unable to change with privsep)"); 1047 sshpam_err = pam_set_item(sshpam_handle, PAM_CONV, 1048 (const void *)&tty_conv); 1049 if (sshpam_err != PAM_SUCCESS) 1050 fatal("PAM: failed to set PAM_CONV: %s", 1051 pam_strerror(sshpam_handle, sshpam_err)); 1052 debug("PAM: changing password"); 1053 sshpam_err = pam_chauthtok(sshpam_handle, PAM_CHANGE_EXPIRED_AUTHTOK); 1054 if (sshpam_err != PAM_SUCCESS) 1055 fatal("PAM: pam_chauthtok(): %s", 1056 pam_strerror(sshpam_handle, sshpam_err)); 1057 } 1058 1059 void 1060 do_pam_session(void) 1061 { 1062 debug3("PAM: opening session"); 1063 sshpam_err = pam_set_item(sshpam_handle, PAM_CONV, 1064 (const void *)&store_conv); 1065 if (sshpam_err != PAM_SUCCESS) 1066 fatal("PAM: failed to set PAM_CONV: %s", 1067 pam_strerror(sshpam_handle, sshpam_err)); 1068 sshpam_err = pam_open_session(sshpam_handle, 0); 1069 if (sshpam_err == PAM_SUCCESS) 1070 sshpam_session_open = 1; 1071 else { 1072 sshpam_session_open = 0; 1073 disable_forwarding(); 1074 error("PAM: pam_open_session(): %s", 1075 pam_strerror(sshpam_handle, sshpam_err)); 1076 } 1077 1078 } 1079 1080 int 1081 is_pam_session_open(void) 1082 { 1083 return sshpam_session_open; 1084 } 1085 1086 /* 1087 * Set a PAM environment string. We need to do this so that the session 1088 * modules can handle things like Kerberos/GSI credentials that appear 1089 * during the ssh authentication process. 1090 */ 1091 int 1092 do_pam_putenv(char *name, char *value) 1093 { 1094 int ret = 1; 1095 #ifdef HAVE_PAM_PUTENV 1096 char *compound; 1097 size_t len; 1098 1099 len = strlen(name) + strlen(value) + 2; 1100 compound = xmalloc(len); 1101 1102 snprintf(compound, len, "%s=%s", name, value); 1103 ret = pam_putenv(sshpam_handle, compound); 1104 free(compound); 1105 #endif 1106 1107 return (ret); 1108 } 1109 1110 char ** 1111 fetch_pam_child_environment(void) 1112 { 1113 return sshpam_env; 1114 } 1115 1116 char ** 1117 fetch_pam_environment(void) 1118 { 1119 return (pam_getenvlist(sshpam_handle)); 1120 } 1121 1122 void 1123 free_pam_environment(char **env) 1124 { 1125 char **envp; 1126 1127 if (env == NULL) 1128 return; 1129 1130 for (envp = env; *envp; envp++) 1131 free(*envp); 1132 free(env); 1133 } 1134 1135 /* 1136 * "Blind" conversation function for password authentication. Assumes that 1137 * echo-off prompts are for the password and stores messages for later 1138 * display. 1139 */ 1140 static int 1141 sshpam_passwd_conv(int n, sshpam_const struct pam_message **msg, 1142 struct pam_response **resp, void *data) 1143 { 1144 struct pam_response *reply; 1145 int i; 1146 size_t len; 1147 1148 debug3("PAM: %s called with %d messages", __func__, n); 1149 1150 *resp = NULL; 1151 1152 if (n <= 0 || n > PAM_MAX_NUM_MSG) 1153 return (PAM_CONV_ERR); 1154 1155 if ((reply = calloc(n, sizeof(*reply))) == NULL) 1156 return (PAM_CONV_ERR); 1157 1158 for (i = 0; i < n; ++i) { 1159 switch (PAM_MSG_MEMBER(msg, i, msg_style)) { 1160 case PAM_PROMPT_ECHO_OFF: 1161 if (sshpam_password == NULL) 1162 goto fail; 1163 if ((reply[i].resp = strdup(sshpam_password)) == NULL) 1164 goto fail; 1165 reply[i].resp_retcode = PAM_SUCCESS; 1166 break; 1167 case PAM_ERROR_MSG: 1168 case PAM_TEXT_INFO: 1169 len = strlen(PAM_MSG_MEMBER(msg, i, msg)); 1170 if (len > 0) { 1171 buffer_append(&loginmsg, 1172 PAM_MSG_MEMBER(msg, i, msg), len); 1173 buffer_append(&loginmsg, "\n", 1); 1174 } 1175 if ((reply[i].resp = strdup("")) == NULL) 1176 goto fail; 1177 reply[i].resp_retcode = PAM_SUCCESS; 1178 break; 1179 default: 1180 goto fail; 1181 } 1182 } 1183 *resp = reply; 1184 return (PAM_SUCCESS); 1185 1186 fail: 1187 for(i = 0; i < n; i++) { 1188 free(reply[i].resp); 1189 } 1190 free(reply); 1191 return (PAM_CONV_ERR); 1192 } 1193 1194 static struct pam_conv passwd_conv = { sshpam_passwd_conv, NULL }; 1195 1196 /* 1197 * Attempt password authentication via PAM 1198 */ 1199 int 1200 sshpam_auth_passwd(Authctxt *authctxt, const char *password) 1201 { 1202 int flags = (options.permit_empty_passwd == 0 ? 1203 PAM_DISALLOW_NULL_AUTHTOK : 0); 1204 char *fake = NULL; 1205 1206 if (!options.use_pam || sshpam_handle == NULL) 1207 fatal("PAM: %s called when PAM disabled or failed to " 1208 "initialise.", __func__); 1209 1210 sshpam_password = password; 1211 sshpam_authctxt = authctxt; 1212 1213 /* 1214 * If the user logging in is invalid, or is root but is not permitted 1215 * by PermitRootLogin, use an invalid password to prevent leaking 1216 * information via timing (eg if the PAM config has a delay on fail). 1217 */ 1218 if (!authctxt->valid || (authctxt->pw->pw_uid == 0 && 1219 options.permit_root_login != PERMIT_YES)) 1220 sshpam_password = fake = fake_password(password); 1221 1222 sshpam_err = pam_set_item(sshpam_handle, PAM_CONV, 1223 (const void *)&passwd_conv); 1224 if (sshpam_err != PAM_SUCCESS) 1225 fatal("PAM: %s: failed to set PAM_CONV: %s", __func__, 1226 pam_strerror(sshpam_handle, sshpam_err)); 1227 1228 sshpam_err = pam_authenticate(sshpam_handle, flags); 1229 sshpam_password = NULL; 1230 free(fake); 1231 if (sshpam_err == PAM_MAXTRIES) 1232 sshpam_set_maxtries_reached(1); 1233 if (sshpam_err == PAM_SUCCESS && authctxt->valid) { 1234 debug("PAM: password authentication accepted for %.100s", 1235 authctxt->user); 1236 return 1; 1237 } else { 1238 debug("PAM: password authentication failed for %.100s: %s", 1239 authctxt->valid ? authctxt->user : "an illegal user", 1240 pam_strerror(sshpam_handle, sshpam_err)); 1241 return 0; 1242 } 1243 } 1244 1245 int 1246 sshpam_get_maxtries_reached(void) 1247 { 1248 return sshpam_maxtries_reached; 1249 } 1250 1251 void 1252 sshpam_set_maxtries_reached(int reached) 1253 { 1254 if (reached == 0 || sshpam_maxtries_reached) 1255 return; 1256 sshpam_maxtries_reached = 1; 1257 options.password_authentication = 0; 1258 options.kbd_interactive_authentication = 0; 1259 options.challenge_response_authentication = 0; 1260 } 1261 #endif /* USE_PAM */ 1262
