auth-pam.c revision 323124
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/* OpenGroup RFC86.0 and XSSO specify no "const" on arguments */ 70#ifdef PAM_SUN_CODEBASE 71# define sshpam_const /* Solaris, HP-UX, SunOS */ 72#else 73# define sshpam_const const /* LinuxPAM, OpenPAM, AIX */ 74#endif 75 76/* Ambiguity in spec: is it an array of pointers or a pointer to an array? */ 77#ifdef PAM_SUN_CODEBASE 78# define PAM_MSG_MEMBER(msg, n, member) ((*(msg))[(n)].member) 79#else 80# define PAM_MSG_MEMBER(msg, n, member) ((msg)[(n)]->member) 81#endif 82 83#include "xmalloc.h" 84#include "buffer.h" 85#include "key.h" 86#include "hostfile.h" 87#include "auth.h" 88#include "auth-pam.h" 89#include "canohost.h" 90#include "log.h" 91#include "msg.h" 92#include "packet.h" 93#include "misc.h" 94#include "servconf.h" 95#include "ssh2.h" 96#include "auth-options.h" 97#ifdef GSSAPI 98#include "ssh-gss.h" 99#endif 100#include "monitor_wrap.h" 101 102extern ServerOptions options; 103extern Buffer loginmsg; 104extern int compat20; 105extern u_int utmp_len; 106 107/* so we don't silently change behaviour */ 108#ifdef USE_POSIX_THREADS 109# error "USE_POSIX_THREADS replaced by UNSUPPORTED_POSIX_THREADS_HACK" 110#endif 111 112/* 113 * Formerly known as USE_POSIX_THREADS, using this is completely unsupported 114 * and generally a bad idea. Use at own risk and do not expect support if 115 * this breaks. 116 */ 117#ifdef UNSUPPORTED_POSIX_THREADS_HACK 118#include <pthread.h> 119/* 120 * Avoid namespace clash when *not* using pthreads for systems *with* 121 * pthreads, which unconditionally define pthread_t via sys/types.h 122 * (e.g. Linux) 123 */ 124typedef pthread_t sp_pthread_t; 125#else 126typedef pid_t sp_pthread_t; 127#endif 128 129struct pam_ctxt { 130 sp_pthread_t pam_thread; 131 int pam_psock; 132 int pam_csock; 133 int pam_done; 134}; 135 136static void sshpam_free_ctx(void *); 137static struct pam_ctxt *cleanup_ctxt; 138 139#ifndef UNSUPPORTED_POSIX_THREADS_HACK 140/* 141 * Simulate threads with processes. 142 */ 143 144static int sshpam_thread_status = -1; 145static mysig_t sshpam_oldsig; 146 147static void 148sshpam_sigchld_handler(int sig) 149{ 150 signal(SIGCHLD, SIG_DFL); 151 if (cleanup_ctxt == NULL) 152 return; /* handler called after PAM cleanup, shouldn't happen */ 153 if (waitpid(cleanup_ctxt->pam_thread, &sshpam_thread_status, WNOHANG) 154 <= 0) { 155 /* PAM thread has not exitted, privsep slave must have */ 156 kill(cleanup_ctxt->pam_thread, SIGTERM); 157 while (waitpid(cleanup_ctxt->pam_thread, 158 &sshpam_thread_status, 0) == -1) { 159 if (errno == EINTR) 160 continue; 161 return; 162 } 163 } 164 if (WIFSIGNALED(sshpam_thread_status) && 165 WTERMSIG(sshpam_thread_status) == SIGTERM) 166 return; /* terminated by pthread_cancel */ 167 if (!WIFEXITED(sshpam_thread_status)) 168 sigdie("PAM: authentication thread exited unexpectedly"); 169 if (WEXITSTATUS(sshpam_thread_status) != 0) 170 sigdie("PAM: authentication thread exited uncleanly"); 171} 172 173/* ARGSUSED */ 174static void 175pthread_exit(void *value) 176{ 177 _exit(0); 178} 179 180/* ARGSUSED */ 181static int 182pthread_create(sp_pthread_t *thread, const void *attr, 183 void *(*thread_start)(void *), void *arg) 184{ 185 pid_t pid; 186 struct pam_ctxt *ctx = arg; 187 188 sshpam_thread_status = -1; 189 switch ((pid = fork())) { 190 case -1: 191 error("fork(): %s", strerror(errno)); 192 return (-1); 193 case 0: 194 close(ctx->pam_psock); 195 ctx->pam_psock = -1; 196 thread_start(arg); 197 _exit(1); 198 default: 199 *thread = pid; 200 close(ctx->pam_csock); 201 ctx->pam_csock = -1; 202 sshpam_oldsig = signal(SIGCHLD, sshpam_sigchld_handler); 203 return (0); 204 } 205} 206 207static int 208pthread_cancel(sp_pthread_t thread) 209{ 210 signal(SIGCHLD, sshpam_oldsig); 211 return (kill(thread, SIGTERM)); 212} 213 214/* ARGSUSED */ 215static int 216pthread_join(sp_pthread_t thread, void **value) 217{ 218 int status; 219 220 if (sshpam_thread_status != -1) 221 return (sshpam_thread_status); 222 signal(SIGCHLD, sshpam_oldsig); 223 while (waitpid(thread, &status, 0) == -1) { 224 if (errno == EINTR) 225 continue; 226 fatal("%s: waitpid: %s", __func__, strerror(errno)); 227 } 228 return (status); 229} 230#endif 231 232 233static pam_handle_t *sshpam_handle = NULL; 234static int sshpam_err = 0; 235static int sshpam_authenticated = 0; 236static int sshpam_session_open = 0; 237static int sshpam_cred_established = 0; 238static int sshpam_account_status = -1; 239static int sshpam_maxtries_reached = 0; 240static char **sshpam_env = NULL; 241static Authctxt *sshpam_authctxt = NULL; 242static const char *sshpam_password = NULL; 243 244/* Some PAM implementations don't implement this */ 245#ifndef HAVE_PAM_GETENVLIST 246static char ** 247pam_getenvlist(pam_handle_t *pamh) 248{ 249 /* 250 * XXX - If necessary, we can still support envrionment passing 251 * for platforms without pam_getenvlist by searching for known 252 * env vars (e.g. KRB5CCNAME) from the PAM environment. 253 */ 254 return NULL; 255} 256#endif 257 258/* 259 * Some platforms, notably Solaris, do not enforce password complexity 260 * rules during pam_chauthtok() if the real uid of the calling process 261 * is 0, on the assumption that it's being called by "passwd" run by root. 262 * This wraps pam_chauthtok and sets/restore the real uid so PAM will do 263 * the right thing. 264 */ 265#ifdef SSHPAM_CHAUTHTOK_NEEDS_RUID 266static int 267sshpam_chauthtok_ruid(pam_handle_t *pamh, int flags) 268{ 269 int result; 270 271 if (sshpam_authctxt == NULL) 272 fatal("PAM: sshpam_authctxt not initialized"); 273 if (setreuid(sshpam_authctxt->pw->pw_uid, -1) == -1) 274 fatal("%s: setreuid failed: %s", __func__, strerror(errno)); 275 result = pam_chauthtok(pamh, flags); 276 if (setreuid(0, -1) == -1) 277 fatal("%s: setreuid failed: %s", __func__, strerror(errno)); 278 return result; 279} 280# define pam_chauthtok(a,b) (sshpam_chauthtok_ruid((a), (b))) 281#endif 282 283void 284sshpam_password_change_required(int reqd) 285{ 286 debug3("%s %d", __func__, reqd); 287 if (sshpam_authctxt == NULL) 288 fatal("%s: PAM authctxt not initialized", __func__); 289 sshpam_authctxt->force_pwchange = reqd; 290 if (reqd) { 291 no_port_forwarding_flag |= 2; 292 no_agent_forwarding_flag |= 2; 293 no_x11_forwarding_flag |= 2; 294 } else { 295 no_port_forwarding_flag &= ~2; 296 no_agent_forwarding_flag &= ~2; 297 no_x11_forwarding_flag &= ~2; 298 } 299} 300 301/* Import regular and PAM environment from subprocess */ 302static void 303import_environments(Buffer *b) 304{ 305 char *env; 306 u_int i, num_env; 307 int err; 308 309 debug3("PAM: %s entering", __func__); 310 311#ifndef UNSUPPORTED_POSIX_THREADS_HACK 312 /* Import variables set by do_pam_account */ 313 sshpam_account_status = buffer_get_int(b); 314 sshpam_password_change_required(buffer_get_int(b)); 315 316 /* Import environment from subprocess */ 317 num_env = buffer_get_int(b); 318 if (num_env > 1024) 319 fatal("%s: received %u environment variables, expected <= 1024", 320 __func__, num_env); 321 sshpam_env = xcalloc(num_env + 1, sizeof(*sshpam_env)); 322 debug3("PAM: num env strings %d", num_env); 323 for(i = 0; i < num_env; i++) 324 sshpam_env[i] = buffer_get_string(b, NULL); 325 326 sshpam_env[num_env] = NULL; 327 328 /* Import PAM environment from subprocess */ 329 num_env = buffer_get_int(b); 330 debug("PAM: num PAM env strings %d", num_env); 331 for(i = 0; i < num_env; i++) { 332 env = buffer_get_string(b, NULL); 333 334#ifdef HAVE_PAM_PUTENV 335 /* Errors are not fatal here */ 336 if ((err = pam_putenv(sshpam_handle, env)) != PAM_SUCCESS) { 337 error("PAM: pam_putenv: %s", 338 pam_strerror(sshpam_handle, sshpam_err)); 339 } 340#endif 341 } 342#endif 343} 344 345/* 346 * Conversation function for authentication thread. 347 */ 348static int 349sshpam_thread_conv(int n, sshpam_const struct pam_message **msg, 350 struct pam_response **resp, void *data) 351{ 352 Buffer buffer; 353 struct pam_ctxt *ctxt; 354 struct pam_response *reply; 355 int i; 356 357 debug3("PAM: %s entering, %d messages", __func__, n); 358 *resp = NULL; 359 360 if (data == NULL) { 361 error("PAM: conversation function passed a null context"); 362 return (PAM_CONV_ERR); 363 } 364 ctxt = data; 365 if (n <= 0 || n > PAM_MAX_NUM_MSG) 366 return (PAM_CONV_ERR); 367 368 if ((reply = calloc(n, sizeof(*reply))) == NULL) 369 return (PAM_CONV_ERR); 370 371 buffer_init(&buffer); 372 for (i = 0; i < n; ++i) { 373 switch (PAM_MSG_MEMBER(msg, i, msg_style)) { 374 case PAM_PROMPT_ECHO_OFF: 375 case PAM_PROMPT_ECHO_ON: 376 buffer_put_cstring(&buffer, 377 PAM_MSG_MEMBER(msg, i, msg)); 378 if (ssh_msg_send(ctxt->pam_csock, 379 PAM_MSG_MEMBER(msg, i, msg_style), &buffer) == -1) 380 goto fail; 381 if (ssh_msg_recv(ctxt->pam_csock, &buffer) == -1) 382 goto fail; 383 if (buffer_get_char(&buffer) != PAM_AUTHTOK) 384 goto fail; 385 reply[i].resp = buffer_get_string(&buffer, NULL); 386 break; 387 case PAM_ERROR_MSG: 388 case PAM_TEXT_INFO: 389 buffer_put_cstring(&buffer, 390 PAM_MSG_MEMBER(msg, i, msg)); 391 if (ssh_msg_send(ctxt->pam_csock, 392 PAM_MSG_MEMBER(msg, i, msg_style), &buffer) == -1) 393 goto fail; 394 break; 395 default: 396 goto fail; 397 } 398 buffer_clear(&buffer); 399 } 400 buffer_free(&buffer); 401 *resp = reply; 402 return (PAM_SUCCESS); 403 404 fail: 405 for(i = 0; i < n; i++) { 406 free(reply[i].resp); 407 } 408 free(reply); 409 buffer_free(&buffer); 410 return (PAM_CONV_ERR); 411} 412 413/* 414 * Authentication thread. 415 */ 416static void * 417sshpam_thread(void *ctxtp) 418{ 419 struct pam_ctxt *ctxt = ctxtp; 420 Buffer buffer; 421 struct pam_conv sshpam_conv; 422 int flags = (options.permit_empty_passwd == 0 ? 423 PAM_DISALLOW_NULL_AUTHTOK : 0); 424#ifndef UNSUPPORTED_POSIX_THREADS_HACK 425 extern char **environ; 426 char **env_from_pam; 427 u_int i; 428 const char *pam_user; 429 const char **ptr_pam_user = &pam_user; 430 char *tz = getenv("TZ"); 431 432 sshpam_err = pam_get_item(sshpam_handle, PAM_USER, 433 (sshpam_const void **)ptr_pam_user); 434 if (sshpam_err != PAM_SUCCESS) 435 goto auth_fail; 436 437 environ[0] = NULL; 438 if (tz != NULL) 439 if (setenv("TZ", tz, 1) == -1) 440 error("PAM: could not set TZ environment: %s", 441 strerror(errno)); 442 443 if (sshpam_authctxt != NULL) { 444 setproctitle("%s [pam]", 445 sshpam_authctxt->valid ? pam_user : "unknown"); 446 } 447#endif 448 449 sshpam_conv.conv = sshpam_thread_conv; 450 sshpam_conv.appdata_ptr = ctxt; 451 452 if (sshpam_authctxt == NULL) 453 fatal("%s: PAM authctxt not initialized", __func__); 454 455 buffer_init(&buffer); 456 sshpam_err = pam_set_item(sshpam_handle, PAM_CONV, 457 (const void *)&sshpam_conv); 458 if (sshpam_err != PAM_SUCCESS) 459 goto auth_fail; 460 sshpam_err = pam_authenticate(sshpam_handle, flags); 461 if (sshpam_err == PAM_MAXTRIES) 462 sshpam_set_maxtries_reached(1); 463 if (sshpam_err != PAM_SUCCESS) 464 goto auth_fail; 465 466 if (compat20) { 467 if (!do_pam_account()) { 468 sshpam_err = PAM_ACCT_EXPIRED; 469 goto auth_fail; 470 } 471 if (sshpam_authctxt->force_pwchange) { 472 sshpam_err = pam_chauthtok(sshpam_handle, 473 PAM_CHANGE_EXPIRED_AUTHTOK); 474 if (sshpam_err != PAM_SUCCESS) 475 goto auth_fail; 476 sshpam_password_change_required(0); 477 } 478 } 479 480 buffer_put_cstring(&buffer, "OK"); 481 482#ifndef UNSUPPORTED_POSIX_THREADS_HACK 483 /* Export variables set by do_pam_account */ 484 buffer_put_int(&buffer, sshpam_account_status); 485 buffer_put_int(&buffer, sshpam_authctxt->force_pwchange); 486 487 /* Export any environment strings set in child */ 488 for(i = 0; environ[i] != NULL; i++) 489 ; /* Count */ 490 buffer_put_int(&buffer, i); 491 for(i = 0; environ[i] != NULL; i++) 492 buffer_put_cstring(&buffer, environ[i]); 493 494 /* Export any environment strings set by PAM in child */ 495 env_from_pam = pam_getenvlist(sshpam_handle); 496 for(i = 0; env_from_pam != NULL && env_from_pam[i] != NULL; i++) 497 ; /* Count */ 498 buffer_put_int(&buffer, i); 499 for(i = 0; env_from_pam != NULL && env_from_pam[i] != NULL; i++) 500 buffer_put_cstring(&buffer, env_from_pam[i]); 501#endif /* UNSUPPORTED_POSIX_THREADS_HACK */ 502 503 /* XXX - can't do much about an error here */ 504 ssh_msg_send(ctxt->pam_csock, sshpam_err, &buffer); 505 buffer_free(&buffer); 506 pthread_exit(NULL); 507 508 auth_fail: 509 buffer_put_cstring(&buffer, 510 pam_strerror(sshpam_handle, sshpam_err)); 511 /* XXX - can't do much about an error here */ 512 if (sshpam_err == PAM_ACCT_EXPIRED) 513 ssh_msg_send(ctxt->pam_csock, PAM_ACCT_EXPIRED, &buffer); 514 else if (sshpam_maxtries_reached) 515 ssh_msg_send(ctxt->pam_csock, PAM_MAXTRIES, &buffer); 516 else 517 ssh_msg_send(ctxt->pam_csock, PAM_AUTH_ERR, &buffer); 518 buffer_free(&buffer); 519 pthread_exit(NULL); 520 521 return (NULL); /* Avoid warning for non-pthread case */ 522} 523 524void 525sshpam_thread_cleanup(void) 526{ 527 struct pam_ctxt *ctxt = cleanup_ctxt; 528 529 debug3("PAM: %s entering", __func__); 530 if (ctxt != NULL && ctxt->pam_thread != 0) { 531 pthread_cancel(ctxt->pam_thread); 532 pthread_join(ctxt->pam_thread, NULL); 533 close(ctxt->pam_psock); 534 close(ctxt->pam_csock); 535 memset(ctxt, 0, sizeof(*ctxt)); 536 cleanup_ctxt = NULL; 537 } 538} 539 540static int 541sshpam_null_conv(int n, sshpam_const struct pam_message **msg, 542 struct pam_response **resp, void *data) 543{ 544 debug3("PAM: %s entering, %d messages", __func__, n); 545 return (PAM_CONV_ERR); 546} 547 548static struct pam_conv null_conv = { sshpam_null_conv, NULL }; 549 550static int 551sshpam_store_conv(int n, sshpam_const struct pam_message **msg, 552 struct pam_response **resp, void *data) 553{ 554 struct pam_response *reply; 555 int i; 556 size_t len; 557 558 debug3("PAM: %s called with %d messages", __func__, n); 559 *resp = NULL; 560 561 if (n <= 0 || n > PAM_MAX_NUM_MSG) 562 return (PAM_CONV_ERR); 563 564 if ((reply = calloc(n, sizeof(*reply))) == NULL) 565 return (PAM_CONV_ERR); 566 567 for (i = 0; i < n; ++i) { 568 switch (PAM_MSG_MEMBER(msg, i, msg_style)) { 569 case PAM_ERROR_MSG: 570 case PAM_TEXT_INFO: 571 len = strlen(PAM_MSG_MEMBER(msg, i, msg)); 572 buffer_append(&loginmsg, PAM_MSG_MEMBER(msg, i, msg), len); 573 buffer_append(&loginmsg, "\n", 1 ); 574 reply[i].resp_retcode = PAM_SUCCESS; 575 break; 576 default: 577 goto fail; 578 } 579 } 580 *resp = reply; 581 return (PAM_SUCCESS); 582 583 fail: 584 for(i = 0; i < n; i++) { 585 free(reply[i].resp); 586 } 587 free(reply); 588 return (PAM_CONV_ERR); 589} 590 591static struct pam_conv store_conv = { sshpam_store_conv, NULL }; 592 593void 594sshpam_cleanup(void) 595{ 596 if (sshpam_handle == NULL || (use_privsep && !mm_is_monitor())) 597 return; 598 debug("PAM: cleanup"); 599 pam_set_item(sshpam_handle, PAM_CONV, (const void *)&null_conv); 600 if (sshpam_session_open) { 601 debug("PAM: closing session"); 602 pam_close_session(sshpam_handle, PAM_SILENT); 603 sshpam_session_open = 0; 604 } 605 if (sshpam_cred_established) { 606 debug("PAM: deleting credentials"); 607 pam_setcred(sshpam_handle, PAM_DELETE_CRED); 608 sshpam_cred_established = 0; 609 } 610 sshpam_authenticated = 0; 611 pam_end(sshpam_handle, sshpam_err); 612 sshpam_handle = NULL; 613} 614 615static int 616sshpam_init(Authctxt *authctxt) 617{ 618 extern char *__progname; 619 const char *pam_rhost, *pam_user, *user = authctxt->user; 620 const char **ptr_pam_user = &pam_user; 621 struct ssh *ssh = active_state; /* XXX */ 622 623 if (sshpam_handle != NULL) { 624 /* We already have a PAM context; check if the user matches */ 625 sshpam_err = pam_get_item(sshpam_handle, 626 PAM_USER, (sshpam_const void **)ptr_pam_user); 627 if (sshpam_err == PAM_SUCCESS && strcmp(user, pam_user) == 0) 628 return (0); 629 pam_end(sshpam_handle, sshpam_err); 630 sshpam_handle = NULL; 631 } 632 debug("PAM: initializing for \"%s\"", user); 633 sshpam_err = 634 pam_start(SSHD_PAM_SERVICE, user, &store_conv, &sshpam_handle); 635 sshpam_authctxt = authctxt; 636 637 if (sshpam_err != PAM_SUCCESS) { 638 pam_end(sshpam_handle, sshpam_err); 639 sshpam_handle = NULL; 640 return (-1); 641 } 642 pam_rhost = auth_get_canonical_hostname(ssh, options.use_dns); 643 debug("PAM: setting PAM_RHOST to \"%s\"", pam_rhost); 644 sshpam_err = pam_set_item(sshpam_handle, PAM_RHOST, pam_rhost); 645 if (sshpam_err != PAM_SUCCESS) { 646 pam_end(sshpam_handle, sshpam_err); 647 sshpam_handle = NULL; 648 return (-1); 649 } 650#ifdef PAM_TTY_KLUDGE 651 /* 652 * Some silly PAM modules (e.g. pam_time) require a TTY to operate. 653 * sshd doesn't set the tty until too late in the auth process and 654 * may not even set one (for tty-less connections) 655 */ 656 debug("PAM: setting PAM_TTY to \"ssh\""); 657 sshpam_err = pam_set_item(sshpam_handle, PAM_TTY, "ssh"); 658 if (sshpam_err != PAM_SUCCESS) { 659 pam_end(sshpam_handle, sshpam_err); 660 sshpam_handle = NULL; 661 return (-1); 662 } 663#endif 664 return (0); 665} 666 667static void * 668sshpam_init_ctx(Authctxt *authctxt) 669{ 670 struct pam_ctxt *ctxt; 671 int socks[2]; 672 673 debug3("PAM: %s entering", __func__); 674 /* 675 * Refuse to start if we don't have PAM enabled or do_pam_account 676 * has previously failed. 677 */ 678 if (!options.use_pam || sshpam_account_status == 0) 679 return NULL; 680 681 /* Initialize PAM */ 682 if (sshpam_init(authctxt) == -1) { 683 error("PAM: initialization failed"); 684 return (NULL); 685 } 686 687 ctxt = xcalloc(1, sizeof *ctxt); 688 689 /* Start the authentication thread */ 690 if (socketpair(AF_UNIX, SOCK_STREAM, PF_UNSPEC, socks) == -1) { 691 error("PAM: failed create sockets: %s", strerror(errno)); 692 free(ctxt); 693 return (NULL); 694 } 695 ctxt->pam_psock = socks[0]; 696 ctxt->pam_csock = socks[1]; 697 if (pthread_create(&ctxt->pam_thread, NULL, sshpam_thread, ctxt) == -1) { 698 error("PAM: failed to start authentication thread: %s", 699 strerror(errno)); 700 close(socks[0]); 701 close(socks[1]); 702 free(ctxt); 703 return (NULL); 704 } 705 cleanup_ctxt = ctxt; 706 return (ctxt); 707} 708 709static int 710sshpam_query(void *ctx, char **name, char **info, 711 u_int *num, char ***prompts, u_int **echo_on) 712{ 713 struct ssh *ssh = active_state; /* XXX */ 714 Buffer buffer; 715 struct pam_ctxt *ctxt = ctx; 716 size_t plen; 717 u_char type; 718 char *msg; 719 size_t len, mlen; 720 721 debug3("PAM: %s entering", __func__); 722 buffer_init(&buffer); 723 *name = xstrdup(""); 724 *info = xstrdup(""); 725 *prompts = xmalloc(sizeof(char *)); 726 **prompts = NULL; 727 plen = 0; 728 *echo_on = xmalloc(sizeof(u_int)); 729 while (ssh_msg_recv(ctxt->pam_psock, &buffer) == 0) { 730 type = buffer_get_char(&buffer); 731 msg = buffer_get_string(&buffer, NULL); 732 mlen = strlen(msg); 733 switch (type) { 734 case PAM_PROMPT_ECHO_ON: 735 case PAM_PROMPT_ECHO_OFF: 736 *num = 1; 737 len = plen + mlen + 1; 738 **prompts = xreallocarray(**prompts, 1, len); 739 strlcpy(**prompts + plen, msg, len - plen); 740 plen += mlen; 741 **echo_on = (type == PAM_PROMPT_ECHO_ON); 742 free(msg); 743 return (0); 744 case PAM_ERROR_MSG: 745 case PAM_TEXT_INFO: 746 /* accumulate messages */ 747 len = plen + mlen + 2; 748 **prompts = xreallocarray(**prompts, 1, len); 749 strlcpy(**prompts + plen, msg, len - plen); 750 plen += mlen; 751 strlcat(**prompts + plen, "\n", len - plen); 752 plen++; 753 free(msg); 754 break; 755 case PAM_ACCT_EXPIRED: 756 case PAM_MAXTRIES: 757 if (type == PAM_ACCT_EXPIRED) 758 sshpam_account_status = 0; 759 if (type == PAM_MAXTRIES) 760 sshpam_set_maxtries_reached(1); 761 /* FALLTHROUGH */ 762 case PAM_AUTH_ERR: 763 debug3("PAM: %s", pam_strerror(sshpam_handle, type)); 764 if (**prompts != NULL && strlen(**prompts) != 0) { 765 *info = **prompts; 766 **prompts = NULL; 767 *num = 0; 768 **echo_on = 0; 769 ctxt->pam_done = -1; 770 free(msg); 771 return 0; 772 } 773 /* FALLTHROUGH */ 774 case PAM_SUCCESS: 775 if (**prompts != NULL) { 776 /* drain any accumulated messages */ 777 debug("PAM: %s", **prompts); 778 buffer_append(&loginmsg, **prompts, 779 strlen(**prompts)); 780 free(**prompts); 781 **prompts = NULL; 782 } 783 if (type == PAM_SUCCESS) { 784 if (!sshpam_authctxt->valid || 785 (sshpam_authctxt->pw->pw_uid == 0 && 786 options.permit_root_login != PERMIT_YES)) 787 fatal("Internal error: PAM auth " 788 "succeeded when it should have " 789 "failed"); 790 import_environments(&buffer); 791 *num = 0; 792 **echo_on = 0; 793 ctxt->pam_done = 1; 794 free(msg); 795 return (0); 796 } 797 error("PAM: %s for %s%.100s from %.100s", msg, 798 sshpam_authctxt->valid ? "" : "illegal user ", 799 sshpam_authctxt->user, 800 auth_get_canonical_hostname(ssh, options.use_dns)); 801 /* FALLTHROUGH */ 802 default: 803 *num = 0; 804 **echo_on = 0; 805 free(msg); 806 ctxt->pam_done = -1; 807 return (-1); 808 } 809 } 810 return (-1); 811} 812 813/* 814 * Returns a junk password of identical length to that the user supplied. 815 * Used to mitigate timing attacks against crypt(3)/PAM stacks that 816 * vary processing time in proportion to password length. 817 */ 818static char * 819fake_password(const char *wire_password) 820{ 821 const char junk[] = "\b\n\r\177INCORRECT"; 822 char *ret = NULL; 823 size_t i, l = wire_password != NULL ? strlen(wire_password) : 0; 824 825 if (l >= INT_MAX) 826 fatal("%s: password length too long: %zu", __func__, l); 827 828 ret = malloc(l + 1); 829 for (i = 0; i < l; i++) 830 ret[i] = junk[i % (sizeof(junk) - 1)]; 831 ret[i] = '\0'; 832 return ret; 833} 834 835/* XXX - see also comment in auth-chall.c:verify_response */ 836static int 837sshpam_respond(void *ctx, u_int num, char **resp) 838{ 839 Buffer buffer; 840 struct pam_ctxt *ctxt = ctx; 841 char *fake; 842 843 debug2("PAM: %s entering, %u responses", __func__, num); 844 switch (ctxt->pam_done) { 845 case 1: 846 sshpam_authenticated = 1; 847 return (0); 848 case 0: 849 break; 850 default: 851 return (-1); 852 } 853 if (num != 1) { 854 error("PAM: expected one response, got %u", num); 855 return (-1); 856 } 857 buffer_init(&buffer); 858 if (sshpam_authctxt->valid && 859 (sshpam_authctxt->pw->pw_uid != 0 || 860 options.permit_root_login == PERMIT_YES)) 861 buffer_put_cstring(&buffer, *resp); 862 else { 863 fake = fake_password(*resp); 864 buffer_put_cstring(&buffer, fake); 865 free(fake); 866 } 867 if (ssh_msg_send(ctxt->pam_psock, PAM_AUTHTOK, &buffer) == -1) { 868 buffer_free(&buffer); 869 return (-1); 870 } 871 buffer_free(&buffer); 872 return (1); 873} 874 875static void 876sshpam_free_ctx(void *ctxtp) 877{ 878 struct pam_ctxt *ctxt = ctxtp; 879 880 debug3("PAM: %s entering", __func__); 881 sshpam_thread_cleanup(); 882 free(ctxt); 883 /* 884 * We don't call sshpam_cleanup() here because we may need the PAM 885 * handle at a later stage, e.g. when setting up a session. It's 886 * still on the cleanup list, so pam_end() *will* be called before 887 * the server process terminates. 888 */ 889} 890 891KbdintDevice sshpam_device = { 892 "pam", 893 sshpam_init_ctx, 894 sshpam_query, 895 sshpam_respond, 896 sshpam_free_ctx 897}; 898 899KbdintDevice mm_sshpam_device = { 900 "pam", 901 mm_sshpam_init_ctx, 902 mm_sshpam_query, 903 mm_sshpam_respond, 904 mm_sshpam_free_ctx 905}; 906 907/* 908 * This replaces auth-pam.c 909 */ 910void 911start_pam(Authctxt *authctxt) 912{ 913 if (!options.use_pam) 914 fatal("PAM: initialisation requested when UsePAM=no"); 915 916 if (sshpam_init(authctxt) == -1) 917 fatal("PAM: initialisation failed"); 918} 919 920void 921finish_pam(void) 922{ 923 sshpam_cleanup(); 924} 925 926u_int 927do_pam_account(void) 928{ 929 debug("%s: called", __func__); 930 if (sshpam_account_status != -1) 931 return (sshpam_account_status); 932 933 sshpam_err = pam_acct_mgmt(sshpam_handle, 0); 934 debug3("PAM: %s pam_acct_mgmt = %d (%s)", __func__, sshpam_err, 935 pam_strerror(sshpam_handle, sshpam_err)); 936 937 if (sshpam_err != PAM_SUCCESS && sshpam_err != PAM_NEW_AUTHTOK_REQD) { 938 sshpam_account_status = 0; 939 return (sshpam_account_status); 940 } 941 942 if (sshpam_err == PAM_NEW_AUTHTOK_REQD) 943 sshpam_password_change_required(1); 944 945 sshpam_account_status = 1; 946 return (sshpam_account_status); 947} 948 949void 950do_pam_set_tty(const char *tty) 951{ 952 if (tty != NULL) { 953 debug("PAM: setting PAM_TTY to \"%s\"", tty); 954 sshpam_err = pam_set_item(sshpam_handle, PAM_TTY, tty); 955 if (sshpam_err != PAM_SUCCESS) 956 fatal("PAM: failed to set PAM_TTY: %s", 957 pam_strerror(sshpam_handle, sshpam_err)); 958 } 959} 960 961void 962do_pam_setcred(int init) 963{ 964 sshpam_err = pam_set_item(sshpam_handle, PAM_CONV, 965 (const void *)&store_conv); 966 if (sshpam_err != PAM_SUCCESS) 967 fatal("PAM: failed to set PAM_CONV: %s", 968 pam_strerror(sshpam_handle, sshpam_err)); 969 if (init) { 970 debug("PAM: establishing credentials"); 971 sshpam_err = pam_setcred(sshpam_handle, PAM_ESTABLISH_CRED); 972 } else { 973 debug("PAM: reinitializing credentials"); 974 sshpam_err = pam_setcred(sshpam_handle, PAM_REINITIALIZE_CRED); 975 } 976 if (sshpam_err == PAM_SUCCESS) { 977 sshpam_cred_established = 1; 978 return; 979 } 980 if (sshpam_authenticated) 981 fatal("PAM: pam_setcred(): %s", 982 pam_strerror(sshpam_handle, sshpam_err)); 983 else 984 debug("PAM: pam_setcred(): %s", 985 pam_strerror(sshpam_handle, sshpam_err)); 986} 987 988static int 989sshpam_tty_conv(int n, sshpam_const struct pam_message **msg, 990 struct pam_response **resp, void *data) 991{ 992 char input[PAM_MAX_MSG_SIZE]; 993 struct pam_response *reply; 994 int i; 995 996 debug3("PAM: %s called with %d messages", __func__, n); 997 998 *resp = NULL; 999 1000 if (n <= 0 || n > PAM_MAX_NUM_MSG || !isatty(STDIN_FILENO)) 1001 return (PAM_CONV_ERR); 1002 1003 if ((reply = calloc(n, sizeof(*reply))) == NULL) 1004 return (PAM_CONV_ERR); 1005 1006 for (i = 0; i < n; ++i) { 1007 switch (PAM_MSG_MEMBER(msg, i, msg_style)) { 1008 case PAM_PROMPT_ECHO_OFF: 1009 reply[i].resp = 1010 read_passphrase(PAM_MSG_MEMBER(msg, i, msg), 1011 RP_ALLOW_STDIN); 1012 reply[i].resp_retcode = PAM_SUCCESS; 1013 break; 1014 case PAM_PROMPT_ECHO_ON: 1015 fprintf(stderr, "%s\n", PAM_MSG_MEMBER(msg, i, msg)); 1016 if (fgets(input, sizeof input, stdin) == NULL) 1017 input[0] = '\0'; 1018 if ((reply[i].resp = strdup(input)) == NULL) 1019 goto fail; 1020 reply[i].resp_retcode = PAM_SUCCESS; 1021 break; 1022 case PAM_ERROR_MSG: 1023 case PAM_TEXT_INFO: 1024 fprintf(stderr, "%s\n", PAM_MSG_MEMBER(msg, i, msg)); 1025 reply[i].resp_retcode = PAM_SUCCESS; 1026 break; 1027 default: 1028 goto fail; 1029 } 1030 } 1031 *resp = reply; 1032 return (PAM_SUCCESS); 1033 1034 fail: 1035 for(i = 0; i < n; i++) { 1036 free(reply[i].resp); 1037 } 1038 free(reply); 1039 return (PAM_CONV_ERR); 1040} 1041 1042static struct pam_conv tty_conv = { sshpam_tty_conv, NULL }; 1043 1044/* 1045 * XXX this should be done in the authentication phase, but ssh1 doesn't 1046 * support that 1047 */ 1048void 1049do_pam_chauthtok(void) 1050{ 1051 if (use_privsep) 1052 fatal("Password expired (unable to change with privsep)"); 1053 sshpam_err = pam_set_item(sshpam_handle, PAM_CONV, 1054 (const void *)&tty_conv); 1055 if (sshpam_err != PAM_SUCCESS) 1056 fatal("PAM: failed to set PAM_CONV: %s", 1057 pam_strerror(sshpam_handle, sshpam_err)); 1058 debug("PAM: changing password"); 1059 sshpam_err = pam_chauthtok(sshpam_handle, PAM_CHANGE_EXPIRED_AUTHTOK); 1060 if (sshpam_err != PAM_SUCCESS) 1061 fatal("PAM: pam_chauthtok(): %s", 1062 pam_strerror(sshpam_handle, sshpam_err)); 1063} 1064 1065void 1066do_pam_session(void) 1067{ 1068 debug3("PAM: opening session"); 1069 sshpam_err = pam_set_item(sshpam_handle, PAM_CONV, 1070 (const void *)&store_conv); 1071 if (sshpam_err != PAM_SUCCESS) 1072 fatal("PAM: failed to set PAM_CONV: %s", 1073 pam_strerror(sshpam_handle, sshpam_err)); 1074 sshpam_err = pam_open_session(sshpam_handle, 0); 1075 if (sshpam_err == PAM_SUCCESS) 1076 sshpam_session_open = 1; 1077 else { 1078 sshpam_session_open = 0; 1079 disable_forwarding(); 1080 error("PAM: pam_open_session(): %s", 1081 pam_strerror(sshpam_handle, sshpam_err)); 1082 } 1083 1084} 1085 1086int 1087is_pam_session_open(void) 1088{ 1089 return sshpam_session_open; 1090} 1091 1092/* 1093 * Set a PAM environment string. We need to do this so that the session 1094 * modules can handle things like Kerberos/GSI credentials that appear 1095 * during the ssh authentication process. 1096 */ 1097int 1098do_pam_putenv(char *name, char *value) 1099{ 1100 int ret = 1; 1101#ifdef HAVE_PAM_PUTENV 1102 char *compound; 1103 size_t len; 1104 1105 len = strlen(name) + strlen(value) + 2; 1106 compound = xmalloc(len); 1107 1108 snprintf(compound, len, "%s=%s", name, value); 1109 ret = pam_putenv(sshpam_handle, compound); 1110 free(compound); 1111#endif 1112 1113 return (ret); 1114} 1115 1116char ** 1117fetch_pam_child_environment(void) 1118{ 1119 return sshpam_env; 1120} 1121 1122char ** 1123fetch_pam_environment(void) 1124{ 1125 return (pam_getenvlist(sshpam_handle)); 1126} 1127 1128void 1129free_pam_environment(char **env) 1130{ 1131 char **envp; 1132 1133 if (env == NULL) 1134 return; 1135 1136 for (envp = env; *envp; envp++) 1137 free(*envp); 1138 free(env); 1139} 1140 1141/* 1142 * "Blind" conversation function for password authentication. Assumes that 1143 * echo-off prompts are for the password and stores messages for later 1144 * display. 1145 */ 1146static int 1147sshpam_passwd_conv(int n, sshpam_const struct pam_message **msg, 1148 struct pam_response **resp, void *data) 1149{ 1150 struct pam_response *reply; 1151 int i; 1152 size_t len; 1153 1154 debug3("PAM: %s called with %d messages", __func__, n); 1155 1156 *resp = NULL; 1157 1158 if (n <= 0 || n > PAM_MAX_NUM_MSG) 1159 return (PAM_CONV_ERR); 1160 1161 if ((reply = calloc(n, sizeof(*reply))) == NULL) 1162 return (PAM_CONV_ERR); 1163 1164 for (i = 0; i < n; ++i) { 1165 switch (PAM_MSG_MEMBER(msg, i, msg_style)) { 1166 case PAM_PROMPT_ECHO_OFF: 1167 if (sshpam_password == NULL) 1168 goto fail; 1169 if ((reply[i].resp = strdup(sshpam_password)) == NULL) 1170 goto fail; 1171 reply[i].resp_retcode = PAM_SUCCESS; 1172 break; 1173 case PAM_ERROR_MSG: 1174 case PAM_TEXT_INFO: 1175 len = strlen(PAM_MSG_MEMBER(msg, i, msg)); 1176 if (len > 0) { 1177 buffer_append(&loginmsg, 1178 PAM_MSG_MEMBER(msg, i, msg), len); 1179 buffer_append(&loginmsg, "\n", 1); 1180 } 1181 if ((reply[i].resp = strdup("")) == NULL) 1182 goto fail; 1183 reply[i].resp_retcode = PAM_SUCCESS; 1184 break; 1185 default: 1186 goto fail; 1187 } 1188 } 1189 *resp = reply; 1190 return (PAM_SUCCESS); 1191 1192 fail: 1193 for(i = 0; i < n; i++) { 1194 free(reply[i].resp); 1195 } 1196 free(reply); 1197 return (PAM_CONV_ERR); 1198} 1199 1200static struct pam_conv passwd_conv = { sshpam_passwd_conv, NULL }; 1201 1202/* 1203 * Attempt password authentication via PAM 1204 */ 1205int 1206sshpam_auth_passwd(Authctxt *authctxt, const char *password) 1207{ 1208 int flags = (options.permit_empty_passwd == 0 ? 1209 PAM_DISALLOW_NULL_AUTHTOK : 0); 1210 char *fake = NULL; 1211 1212 if (!options.use_pam || sshpam_handle == NULL) 1213 fatal("PAM: %s called when PAM disabled or failed to " 1214 "initialise.", __func__); 1215 1216 sshpam_password = password; 1217 sshpam_authctxt = authctxt; 1218 1219 /* 1220 * If the user logging in is invalid, or is root but is not permitted 1221 * by PermitRootLogin, use an invalid password to prevent leaking 1222 * information via timing (eg if the PAM config has a delay on fail). 1223 */ 1224 if (!authctxt->valid || (authctxt->pw->pw_uid == 0 && 1225 options.permit_root_login != PERMIT_YES)) 1226 sshpam_password = fake = fake_password(password); 1227 1228 sshpam_err = pam_set_item(sshpam_handle, PAM_CONV, 1229 (const void *)&passwd_conv); 1230 if (sshpam_err != PAM_SUCCESS) 1231 fatal("PAM: %s: failed to set PAM_CONV: %s", __func__, 1232 pam_strerror(sshpam_handle, sshpam_err)); 1233 1234 sshpam_err = pam_authenticate(sshpam_handle, flags); 1235 sshpam_password = NULL; 1236 free(fake); 1237 if (sshpam_err == PAM_MAXTRIES) 1238 sshpam_set_maxtries_reached(1); 1239 if (sshpam_err == PAM_SUCCESS && authctxt->valid) { 1240 debug("PAM: password authentication accepted for %.100s", 1241 authctxt->user); 1242 return 1; 1243 } else { 1244 debug("PAM: password authentication failed for %.100s: %s", 1245 authctxt->valid ? authctxt->user : "an illegal user", 1246 pam_strerror(sshpam_handle, sshpam_err)); 1247 return 0; 1248 } 1249} 1250 1251int 1252sshpam_get_maxtries_reached(void) 1253{ 1254 return sshpam_maxtries_reached; 1255} 1256 1257void 1258sshpam_set_maxtries_reached(int reached) 1259{ 1260 if (reached == 0 || sshpam_maxtries_reached) 1261 return; 1262 sshpam_maxtries_reached = 1; 1263 options.password_authentication = 0; 1264 options.kbd_interactive_authentication = 0; 1265 options.challenge_response_authentication = 0; 1266} 1267#endif /* USE_PAM */ 1268