auth-pam.c revision 323134
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) 70extern 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#include "blacklist_client.h" 107 108extern ServerOptions options; 109extern Buffer loginmsg; 110extern int compat20; 111extern u_int utmp_len; 112 113/* so we don't silently change behaviour */ 114#ifdef USE_POSIX_THREADS 115# error "USE_POSIX_THREADS replaced by UNSUPPORTED_POSIX_THREADS_HACK" 116#endif 117 118/* 119 * Formerly known as USE_POSIX_THREADS, using this is completely unsupported 120 * and generally a bad idea. Use at own risk and do not expect support if 121 * this breaks. 122 */ 123#ifdef UNSUPPORTED_POSIX_THREADS_HACK 124#include <pthread.h> 125/* 126 * Avoid namespace clash when *not* using pthreads for systems *with* 127 * pthreads, which unconditionally define pthread_t via sys/types.h 128 * (e.g. Linux) 129 */ 130typedef pthread_t sp_pthread_t; 131#else 132typedef pid_t sp_pthread_t; 133#endif 134 135struct pam_ctxt { 136 sp_pthread_t pam_thread; 137 int pam_psock; 138 int pam_csock; 139 int pam_done; 140}; 141 142static void sshpam_free_ctx(void *); 143static struct pam_ctxt *cleanup_ctxt; 144 145#ifndef UNSUPPORTED_POSIX_THREADS_HACK 146/* 147 * Simulate threads with processes. 148 */ 149 150static int sshpam_thread_status = -1; 151static mysig_t sshpam_oldsig; 152 153static void 154sshpam_sigchld_handler(int sig) 155{ 156 signal(SIGCHLD, SIG_DFL); 157 if (cleanup_ctxt == NULL) 158 return; /* handler called after PAM cleanup, shouldn't happen */ 159 if (waitpid(cleanup_ctxt->pam_thread, &sshpam_thread_status, WNOHANG) 160 <= 0) { 161 /* PAM thread has not exitted, privsep slave must have */ 162 kill(cleanup_ctxt->pam_thread, SIGTERM); 163 while (waitpid(cleanup_ctxt->pam_thread, 164 &sshpam_thread_status, 0) == -1) { 165 if (errno == EINTR) 166 continue; 167 return; 168 } 169 } 170 if (WIFSIGNALED(sshpam_thread_status) && 171 WTERMSIG(sshpam_thread_status) == SIGTERM) 172 return; /* terminated by pthread_cancel */ 173 if (!WIFEXITED(sshpam_thread_status)) 174 sigdie("PAM: authentication thread exited unexpectedly"); 175 if (WEXITSTATUS(sshpam_thread_status) != 0) 176 sigdie("PAM: authentication thread exited uncleanly"); 177} 178 179/* ARGSUSED */ 180static void 181pthread_exit(void *value) 182{ 183 _exit(0); 184} 185 186/* ARGSUSED */ 187static int 188pthread_create(sp_pthread_t *thread, const void *attr, 189 void *(*thread_start)(void *), void *arg) 190{ 191 pid_t pid; 192 struct pam_ctxt *ctx = arg; 193 194 sshpam_thread_status = -1; 195 switch ((pid = fork())) { 196 case -1: 197 error("fork(): %s", strerror(errno)); 198 return (-1); 199 case 0: 200 close(ctx->pam_psock); 201 ctx->pam_psock = -1; 202 thread_start(arg); 203 _exit(1); 204 default: 205 *thread = pid; 206 close(ctx->pam_csock); 207 ctx->pam_csock = -1; 208 sshpam_oldsig = signal(SIGCHLD, sshpam_sigchld_handler); 209 return (0); 210 } 211} 212 213static int 214pthread_cancel(sp_pthread_t thread) 215{ 216 signal(SIGCHLD, sshpam_oldsig); 217 return (kill(thread, SIGTERM)); 218} 219 220/* ARGSUSED */ 221static int 222pthread_join(sp_pthread_t thread, void **value) 223{ 224 int status; 225 226 if (sshpam_thread_status != -1) 227 return (sshpam_thread_status); 228 signal(SIGCHLD, sshpam_oldsig); 229 while (waitpid(thread, &status, 0) == -1) { 230 if (errno == EINTR) 231 continue; 232 fatal("%s: waitpid: %s", __func__, strerror(errno)); 233 } 234 return (status); 235} 236#endif 237 238 239static pam_handle_t *sshpam_handle = NULL; 240static int sshpam_err = 0; 241static int sshpam_authenticated = 0; 242static int sshpam_session_open = 0; 243static int sshpam_cred_established = 0; 244static int sshpam_account_status = -1; 245static int sshpam_maxtries_reached = 0; 246static char **sshpam_env = NULL; 247static Authctxt *sshpam_authctxt = NULL; 248static const char *sshpam_password = NULL; 249 250/* Some PAM implementations don't implement this */ 251#ifndef HAVE_PAM_GETENVLIST 252static char ** 253pam_getenvlist(pam_handle_t *pamh) 254{ 255 /* 256 * XXX - If necessary, we can still support envrionment passing 257 * for platforms without pam_getenvlist by searching for known 258 * env vars (e.g. KRB5CCNAME) from the PAM environment. 259 */ 260 return NULL; 261} 262#endif 263 264/* 265 * Some platforms, notably Solaris, do not enforce password complexity 266 * rules during pam_chauthtok() if the real uid of the calling process 267 * is 0, on the assumption that it's being called by "passwd" run by root. 268 * This wraps pam_chauthtok and sets/restore the real uid so PAM will do 269 * the right thing. 270 */ 271#ifdef SSHPAM_CHAUTHTOK_NEEDS_RUID 272static int 273sshpam_chauthtok_ruid(pam_handle_t *pamh, int flags) 274{ 275 int result; 276 277 if (sshpam_authctxt == NULL) 278 fatal("PAM: sshpam_authctxt not initialized"); 279 if (setreuid(sshpam_authctxt->pw->pw_uid, -1) == -1) 280 fatal("%s: setreuid failed: %s", __func__, strerror(errno)); 281 result = pam_chauthtok(pamh, flags); 282 if (setreuid(0, -1) == -1) 283 fatal("%s: setreuid failed: %s", __func__, strerror(errno)); 284 return result; 285} 286# define pam_chauthtok(a,b) (sshpam_chauthtok_ruid((a), (b))) 287#endif 288 289void 290sshpam_password_change_required(int reqd) 291{ 292 debug3("%s %d", __func__, reqd); 293 if (sshpam_authctxt == NULL) 294 fatal("%s: PAM authctxt not initialized", __func__); 295 sshpam_authctxt->force_pwchange = reqd; 296 if (reqd) { 297 no_port_forwarding_flag |= 2; 298 no_agent_forwarding_flag |= 2; 299 no_x11_forwarding_flag |= 2; 300 } else { 301 no_port_forwarding_flag &= ~2; 302 no_agent_forwarding_flag &= ~2; 303 no_x11_forwarding_flag &= ~2; 304 } 305} 306 307/* Import regular and PAM environment from subprocess */ 308static void 309import_environments(Buffer *b) 310{ 311 char *env; 312 u_int i, num_env; 313 int err; 314 315 debug3("PAM: %s entering", __func__); 316 317#ifndef UNSUPPORTED_POSIX_THREADS_HACK 318 /* Import variables set by do_pam_account */ 319 sshpam_account_status = buffer_get_int(b); 320 sshpam_password_change_required(buffer_get_int(b)); 321 322 /* Import environment from subprocess */ 323 num_env = buffer_get_int(b); 324 if (num_env > 1024) 325 fatal("%s: received %u environment variables, expected <= 1024", 326 __func__, num_env); 327 sshpam_env = xcalloc(num_env + 1, sizeof(*sshpam_env)); 328 debug3("PAM: num env strings %d", num_env); 329 for(i = 0; i < num_env; i++) 330 sshpam_env[i] = buffer_get_string(b, NULL); 331 332 sshpam_env[num_env] = NULL; 333 334 /* Import PAM environment from subprocess */ 335 num_env = buffer_get_int(b); 336 debug("PAM: num PAM env strings %d", num_env); 337 for(i = 0; i < num_env; i++) { 338 env = buffer_get_string(b, NULL); 339 340#ifdef HAVE_PAM_PUTENV 341 /* Errors are not fatal here */ 342 if ((err = pam_putenv(sshpam_handle, env)) != PAM_SUCCESS) { 343 error("PAM: pam_putenv: %s", 344 pam_strerror(sshpam_handle, sshpam_err)); 345 } 346#endif 347 } 348#endif 349} 350 351/* 352 * Conversation function for authentication thread. 353 */ 354static int 355sshpam_thread_conv(int n, sshpam_const struct pam_message **msg, 356 struct pam_response **resp, void *data) 357{ 358 Buffer buffer; 359 struct pam_ctxt *ctxt; 360 struct pam_response *reply; 361 int i; 362 363 debug3("PAM: %s entering, %d messages", __func__, n); 364 *resp = NULL; 365 366 if (data == NULL) { 367 error("PAM: conversation function passed a null context"); 368 return (PAM_CONV_ERR); 369 } 370 ctxt = data; 371 if (n <= 0 || n > PAM_MAX_NUM_MSG) 372 return (PAM_CONV_ERR); 373 374 if ((reply = calloc(n, sizeof(*reply))) == NULL) 375 return (PAM_CONV_ERR); 376 377 buffer_init(&buffer); 378 for (i = 0; i < n; ++i) { 379 switch (PAM_MSG_MEMBER(msg, i, msg_style)) { 380 case PAM_PROMPT_ECHO_OFF: 381 case PAM_PROMPT_ECHO_ON: 382 buffer_put_cstring(&buffer, 383 PAM_MSG_MEMBER(msg, i, msg)); 384 if (ssh_msg_send(ctxt->pam_csock, 385 PAM_MSG_MEMBER(msg, i, msg_style), &buffer) == -1) 386 goto fail; 387 if (ssh_msg_recv(ctxt->pam_csock, &buffer) == -1) 388 goto fail; 389 if (buffer_get_char(&buffer) != PAM_AUTHTOK) 390 goto fail; 391 reply[i].resp = buffer_get_string(&buffer, NULL); 392 break; 393 case PAM_ERROR_MSG: 394 case PAM_TEXT_INFO: 395 buffer_put_cstring(&buffer, 396 PAM_MSG_MEMBER(msg, i, msg)); 397 if (ssh_msg_send(ctxt->pam_csock, 398 PAM_MSG_MEMBER(msg, i, msg_style), &buffer) == -1) 399 goto fail; 400 break; 401 default: 402 goto fail; 403 } 404 buffer_clear(&buffer); 405 } 406 buffer_free(&buffer); 407 *resp = reply; 408 return (PAM_SUCCESS); 409 410 fail: 411 for(i = 0; i < n; i++) { 412 free(reply[i].resp); 413 } 414 free(reply); 415 buffer_free(&buffer); 416 return (PAM_CONV_ERR); 417} 418 419/* 420 * Authentication thread. 421 */ 422static void * 423sshpam_thread(void *ctxtp) 424{ 425 struct pam_ctxt *ctxt = ctxtp; 426 Buffer buffer; 427 struct pam_conv sshpam_conv; 428 int flags = (options.permit_empty_passwd == 0 ? 429 PAM_DISALLOW_NULL_AUTHTOK : 0); 430#ifndef UNSUPPORTED_POSIX_THREADS_HACK 431 extern char **environ; 432 char **env_from_pam; 433 u_int i; 434 const char *pam_user; 435 const char **ptr_pam_user = &pam_user; 436 char *tz = getenv("TZ"); 437 438 sshpam_err = pam_get_item(sshpam_handle, PAM_USER, 439 (sshpam_const void **)ptr_pam_user); 440 if (sshpam_err != PAM_SUCCESS) 441 goto auth_fail; 442 443 environ[0] = NULL; 444 if (tz != NULL) 445 if (setenv("TZ", tz, 1) == -1) 446 error("PAM: could not set TZ environment: %s", 447 strerror(errno)); 448 449 if (sshpam_authctxt != NULL) { 450 setproctitle("%s [pam]", 451 sshpam_authctxt->valid ? pam_user : "unknown"); 452 } 453#endif 454 455 sshpam_conv.conv = sshpam_thread_conv; 456 sshpam_conv.appdata_ptr = ctxt; 457 458 if (sshpam_authctxt == NULL) 459 fatal("%s: PAM authctxt not initialized", __func__); 460 461 buffer_init(&buffer); 462 sshpam_err = pam_set_item(sshpam_handle, PAM_CONV, 463 (const void *)&sshpam_conv); 464 if (sshpam_err != PAM_SUCCESS) 465 goto auth_fail; 466 sshpam_err = pam_authenticate(sshpam_handle, flags); 467 if (sshpam_err == PAM_MAXTRIES) 468 sshpam_set_maxtries_reached(1); 469 if (sshpam_err != PAM_SUCCESS) 470 goto auth_fail; 471 472 if (compat20) { 473 if (!do_pam_account()) { 474 sshpam_err = PAM_ACCT_EXPIRED; 475 goto auth_fail; 476 } 477 if (sshpam_authctxt->force_pwchange) { 478 sshpam_err = pam_chauthtok(sshpam_handle, 479 PAM_CHANGE_EXPIRED_AUTHTOK); 480 if (sshpam_err != PAM_SUCCESS) 481 goto auth_fail; 482 sshpam_password_change_required(0); 483 } 484 } 485 486 buffer_put_cstring(&buffer, "OK"); 487 488#ifndef UNSUPPORTED_POSIX_THREADS_HACK 489 /* Export variables set by do_pam_account */ 490 buffer_put_int(&buffer, sshpam_account_status); 491 buffer_put_int(&buffer, sshpam_authctxt->force_pwchange); 492 493 /* Export any environment strings set in child */ 494 for(i = 0; environ[i] != NULL; i++) 495 ; /* Count */ 496 buffer_put_int(&buffer, i); 497 for(i = 0; environ[i] != NULL; i++) 498 buffer_put_cstring(&buffer, environ[i]); 499 500 /* Export any environment strings set by PAM in child */ 501 env_from_pam = pam_getenvlist(sshpam_handle); 502 for(i = 0; env_from_pam != NULL && env_from_pam[i] != NULL; i++) 503 ; /* Count */ 504 buffer_put_int(&buffer, i); 505 for(i = 0; env_from_pam != NULL && env_from_pam[i] != NULL; i++) 506 buffer_put_cstring(&buffer, env_from_pam[i]); 507#endif /* UNSUPPORTED_POSIX_THREADS_HACK */ 508 509 /* XXX - can't do much about an error here */ 510 ssh_msg_send(ctxt->pam_csock, sshpam_err, &buffer); 511 buffer_free(&buffer); 512 pthread_exit(NULL); 513 514 auth_fail: 515 buffer_put_cstring(&buffer, 516 pam_strerror(sshpam_handle, sshpam_err)); 517 /* XXX - can't do much about an error here */ 518 if (sshpam_err == PAM_ACCT_EXPIRED) 519 ssh_msg_send(ctxt->pam_csock, PAM_ACCT_EXPIRED, &buffer); 520 else if (sshpam_maxtries_reached) 521 ssh_msg_send(ctxt->pam_csock, PAM_MAXTRIES, &buffer); 522 else 523 ssh_msg_send(ctxt->pam_csock, PAM_AUTH_ERR, &buffer); 524 buffer_free(&buffer); 525 pthread_exit(NULL); 526 527 return (NULL); /* Avoid warning for non-pthread case */ 528} 529 530void 531sshpam_thread_cleanup(void) 532{ 533 struct pam_ctxt *ctxt = cleanup_ctxt; 534 535 debug3("PAM: %s entering", __func__); 536 if (ctxt != NULL && ctxt->pam_thread != 0) { 537 pthread_cancel(ctxt->pam_thread); 538 pthread_join(ctxt->pam_thread, NULL); 539 close(ctxt->pam_psock); 540 close(ctxt->pam_csock); 541 memset(ctxt, 0, sizeof(*ctxt)); 542 cleanup_ctxt = NULL; 543 } 544} 545 546static int 547sshpam_null_conv(int n, sshpam_const struct pam_message **msg, 548 struct pam_response **resp, void *data) 549{ 550 debug3("PAM: %s entering, %d messages", __func__, n); 551 return (PAM_CONV_ERR); 552} 553 554static struct pam_conv null_conv = { sshpam_null_conv, NULL }; 555 556static int 557sshpam_store_conv(int n, sshpam_const struct pam_message **msg, 558 struct pam_response **resp, void *data) 559{ 560 struct pam_response *reply; 561 int i; 562 size_t len; 563 564 debug3("PAM: %s called with %d messages", __func__, n); 565 *resp = NULL; 566 567 if (n <= 0 || n > PAM_MAX_NUM_MSG) 568 return (PAM_CONV_ERR); 569 570 if ((reply = calloc(n, sizeof(*reply))) == NULL) 571 return (PAM_CONV_ERR); 572 573 for (i = 0; i < n; ++i) { 574 switch (PAM_MSG_MEMBER(msg, i, msg_style)) { 575 case PAM_ERROR_MSG: 576 case PAM_TEXT_INFO: 577 len = strlen(PAM_MSG_MEMBER(msg, i, msg)); 578 buffer_append(&loginmsg, PAM_MSG_MEMBER(msg, i, msg), len); 579 buffer_append(&loginmsg, "\n", 1 ); 580 reply[i].resp_retcode = PAM_SUCCESS; 581 break; 582 default: 583 goto fail; 584 } 585 } 586 *resp = reply; 587 return (PAM_SUCCESS); 588 589 fail: 590 for(i = 0; i < n; i++) { 591 free(reply[i].resp); 592 } 593 free(reply); 594 return (PAM_CONV_ERR); 595} 596 597static struct pam_conv store_conv = { sshpam_store_conv, NULL }; 598 599void 600sshpam_cleanup(void) 601{ 602 if (sshpam_handle == NULL || (use_privsep && !mm_is_monitor())) 603 return; 604 debug("PAM: cleanup"); 605 pam_set_item(sshpam_handle, PAM_CONV, (const void *)&null_conv); 606 if (sshpam_session_open) { 607 debug("PAM: closing session"); 608 pam_close_session(sshpam_handle, PAM_SILENT); 609 sshpam_session_open = 0; 610 } 611 if (sshpam_cred_established) { 612 debug("PAM: deleting credentials"); 613 pam_setcred(sshpam_handle, PAM_DELETE_CRED); 614 sshpam_cred_established = 0; 615 } 616 sshpam_authenticated = 0; 617 pam_end(sshpam_handle, sshpam_err); 618 sshpam_handle = NULL; 619} 620 621static int 622sshpam_init(Authctxt *authctxt) 623{ 624 const char *pam_rhost, *pam_user, *user = authctxt->user; 625 const char **ptr_pam_user = &pam_user; 626 struct ssh *ssh = active_state; /* XXX */ 627 628 if (sshpam_handle != NULL) { 629 /* We already have a PAM context; check if the user matches */ 630 sshpam_err = pam_get_item(sshpam_handle, 631 PAM_USER, (sshpam_const void **)ptr_pam_user); 632 if (sshpam_err == PAM_SUCCESS && strcmp(user, pam_user) == 0) 633 return (0); 634 pam_end(sshpam_handle, sshpam_err); 635 sshpam_handle = NULL; 636 } 637 debug("PAM: initializing for \"%s\"", user); 638 sshpam_err = 639 pam_start(SSHD_PAM_SERVICE, user, &store_conv, &sshpam_handle); 640 sshpam_authctxt = authctxt; 641 642 if (sshpam_err != PAM_SUCCESS) { 643 pam_end(sshpam_handle, sshpam_err); 644 sshpam_handle = NULL; 645 return (-1); 646 } 647 pam_rhost = auth_get_canonical_hostname(ssh, options.use_dns); 648 debug("PAM: setting PAM_RHOST to \"%s\"", pam_rhost); 649 sshpam_err = pam_set_item(sshpam_handle, PAM_RHOST, pam_rhost); 650 if (sshpam_err != PAM_SUCCESS) { 651 pam_end(sshpam_handle, sshpam_err); 652 sshpam_handle = NULL; 653 return (-1); 654 } 655#ifdef PAM_TTY_KLUDGE 656 /* 657 * Some silly PAM modules (e.g. pam_time) require a TTY to operate. 658 * sshd doesn't set the tty until too late in the auth process and 659 * may not even set one (for tty-less connections) 660 */ 661 debug("PAM: setting PAM_TTY to \"ssh\""); 662 sshpam_err = pam_set_item(sshpam_handle, PAM_TTY, "ssh"); 663 if (sshpam_err != PAM_SUCCESS) { 664 pam_end(sshpam_handle, sshpam_err); 665 sshpam_handle = NULL; 666 return (-1); 667 } 668#endif 669 return (0); 670} 671 672static void * 673sshpam_init_ctx(Authctxt *authctxt) 674{ 675 struct pam_ctxt *ctxt; 676 int socks[2]; 677 678 debug3("PAM: %s entering", __func__); 679 /* 680 * Refuse to start if we don't have PAM enabled or do_pam_account 681 * has previously failed. 682 */ 683 if (!options.use_pam || sshpam_account_status == 0) 684 return NULL; 685 686 /* Initialize PAM */ 687 if (sshpam_init(authctxt) == -1) { 688 error("PAM: initialization failed"); 689 return (NULL); 690 } 691 692 ctxt = xcalloc(1, sizeof *ctxt); 693 694 /* Start the authentication thread */ 695 if (socketpair(AF_UNIX, SOCK_STREAM, PF_UNSPEC, socks) == -1) { 696 error("PAM: failed create sockets: %s", strerror(errno)); 697 free(ctxt); 698 return (NULL); 699 } 700 ctxt->pam_psock = socks[0]; 701 ctxt->pam_csock = socks[1]; 702 if (pthread_create(&ctxt->pam_thread, NULL, sshpam_thread, ctxt) == -1) { 703 error("PAM: failed to start authentication thread: %s", 704 strerror(errno)); 705 close(socks[0]); 706 close(socks[1]); 707 free(ctxt); 708 return (NULL); 709 } 710 cleanup_ctxt = ctxt; 711 return (ctxt); 712} 713 714static int 715sshpam_query(void *ctx, char **name, char **info, 716 u_int *num, char ***prompts, u_int **echo_on) 717{ 718 struct ssh *ssh = active_state; /* XXX */ 719 Buffer buffer; 720 struct pam_ctxt *ctxt = ctx; 721 size_t plen; 722 u_char type; 723 char *msg; 724 size_t len, mlen; 725 726 debug3("PAM: %s entering", __func__); 727 buffer_init(&buffer); 728 *name = xstrdup(""); 729 *info = xstrdup(""); 730 *prompts = xmalloc(sizeof(char *)); 731 **prompts = NULL; 732 plen = 0; 733 *echo_on = xmalloc(sizeof(u_int)); 734 while (ssh_msg_recv(ctxt->pam_psock, &buffer) == 0) { 735 type = buffer_get_char(&buffer); 736 msg = buffer_get_string(&buffer, NULL); 737 mlen = strlen(msg); 738 switch (type) { 739 case PAM_PROMPT_ECHO_ON: 740 case PAM_PROMPT_ECHO_OFF: 741 *num = 1; 742 len = plen + mlen + 1; 743 **prompts = xreallocarray(**prompts, 1, len); 744 strlcpy(**prompts + plen, msg, len - plen); 745 plen += mlen; 746 **echo_on = (type == PAM_PROMPT_ECHO_ON); 747 free(msg); 748 return (0); 749 case PAM_ERROR_MSG: 750 case PAM_TEXT_INFO: 751 /* accumulate messages */ 752 len = plen + mlen + 2; 753 **prompts = xreallocarray(**prompts, 1, len); 754 strlcpy(**prompts + plen, msg, len - plen); 755 plen += mlen; 756 strlcat(**prompts + plen, "\n", len - plen); 757 plen++; 758 free(msg); 759 break; 760 case PAM_ACCT_EXPIRED: 761 case PAM_MAXTRIES: 762 if (type == PAM_ACCT_EXPIRED) 763 sshpam_account_status = 0; 764 if (type == PAM_MAXTRIES) 765 sshpam_set_maxtries_reached(1); 766 /* FALLTHROUGH */ 767 case PAM_AUTH_ERR: 768 debug3("PAM: %s", pam_strerror(sshpam_handle, type)); 769 if (**prompts != NULL && strlen(**prompts) != 0) { 770 *info = **prompts; 771 **prompts = NULL; 772 *num = 0; 773 **echo_on = 0; 774 ctxt->pam_done = -1; 775 free(msg); 776 return 0; 777 } 778 /* FALLTHROUGH */ 779 case PAM_SUCCESS: 780 if (**prompts != NULL) { 781 /* drain any accumulated messages */ 782 debug("PAM: %s", **prompts); 783 buffer_append(&loginmsg, **prompts, 784 strlen(**prompts)); 785 free(**prompts); 786 **prompts = NULL; 787 } 788 if (type == PAM_SUCCESS) { 789 if (!sshpam_authctxt->valid || 790 (sshpam_authctxt->pw->pw_uid == 0 && 791 options.permit_root_login != PERMIT_YES)) 792 fatal("Internal error: PAM auth " 793 "succeeded when it should have " 794 "failed"); 795 import_environments(&buffer); 796 *num = 0; 797 **echo_on = 0; 798 ctxt->pam_done = 1; 799 free(msg); 800 return (0); 801 } 802 BLACKLIST_NOTIFY(BLACKLIST_BAD_USER, 803 sshpam_authctxt->user); 804 error("PAM: %s for %s%.100s from %.100s", msg, 805 sshpam_authctxt->valid ? "" : "illegal user ", 806 sshpam_authctxt->user, 807 auth_get_canonical_hostname(ssh, options.use_dns)); 808 /* FALLTHROUGH */ 809 default: 810 *num = 0; 811 **echo_on = 0; 812 free(msg); 813 ctxt->pam_done = -1; 814 return (-1); 815 } 816 } 817 return (-1); 818} 819 820/* 821 * Returns a junk password of identical length to that the user supplied. 822 * Used to mitigate timing attacks against crypt(3)/PAM stacks that 823 * vary processing time in proportion to password length. 824 */ 825static char * 826fake_password(const char *wire_password) 827{ 828 const char junk[] = "\b\n\r\177INCORRECT"; 829 char *ret = NULL; 830 size_t i, l = wire_password != NULL ? strlen(wire_password) : 0; 831 832 if (l >= INT_MAX) 833 fatal("%s: password length too long: %zu", __func__, l); 834 835 ret = malloc(l + 1); 836 for (i = 0; i < l; i++) 837 ret[i] = junk[i % (sizeof(junk) - 1)]; 838 ret[i] = '\0'; 839 return ret; 840} 841 842/* XXX - see also comment in auth-chall.c:verify_response */ 843static int 844sshpam_respond(void *ctx, u_int num, char **resp) 845{ 846 Buffer buffer; 847 struct pam_ctxt *ctxt = ctx; 848 char *fake; 849 850 debug2("PAM: %s entering, %u responses", __func__, num); 851 switch (ctxt->pam_done) { 852 case 1: 853 sshpam_authenticated = 1; 854 return (0); 855 case 0: 856 break; 857 default: 858 return (-1); 859 } 860 if (num != 1) { 861 error("PAM: expected one response, got %u", num); 862 return (-1); 863 } 864 buffer_init(&buffer); 865 if (sshpam_authctxt->valid && 866 (sshpam_authctxt->pw->pw_uid != 0 || 867 options.permit_root_login == PERMIT_YES)) 868 buffer_put_cstring(&buffer, *resp); 869 else { 870 fake = fake_password(*resp); 871 buffer_put_cstring(&buffer, fake); 872 free(fake); 873 } 874 if (ssh_msg_send(ctxt->pam_psock, PAM_AUTHTOK, &buffer) == -1) { 875 buffer_free(&buffer); 876 return (-1); 877 } 878 buffer_free(&buffer); 879 return (1); 880} 881 882static void 883sshpam_free_ctx(void *ctxtp) 884{ 885 struct pam_ctxt *ctxt = ctxtp; 886 887 debug3("PAM: %s entering", __func__); 888 sshpam_thread_cleanup(); 889 free(ctxt); 890 /* 891 * We don't call sshpam_cleanup() here because we may need the PAM 892 * handle at a later stage, e.g. when setting up a session. It's 893 * still on the cleanup list, so pam_end() *will* be called before 894 * the server process terminates. 895 */ 896} 897 898KbdintDevice sshpam_device = { 899 "pam", 900 sshpam_init_ctx, 901 sshpam_query, 902 sshpam_respond, 903 sshpam_free_ctx 904}; 905 906KbdintDevice mm_sshpam_device = { 907 "pam", 908 mm_sshpam_init_ctx, 909 mm_sshpam_query, 910 mm_sshpam_respond, 911 mm_sshpam_free_ctx 912}; 913 914/* 915 * This replaces auth-pam.c 916 */ 917void 918start_pam(Authctxt *authctxt) 919{ 920 if (!options.use_pam) 921 fatal("PAM: initialisation requested when UsePAM=no"); 922 923 if (sshpam_init(authctxt) == -1) 924 fatal("PAM: initialisation failed"); 925} 926 927void 928finish_pam(void) 929{ 930 sshpam_cleanup(); 931} 932 933u_int 934do_pam_account(void) 935{ 936 debug("%s: called", __func__); 937 if (sshpam_account_status != -1) 938 return (sshpam_account_status); 939 940 sshpam_err = pam_acct_mgmt(sshpam_handle, 0); 941 debug3("PAM: %s pam_acct_mgmt = %d (%s)", __func__, sshpam_err, 942 pam_strerror(sshpam_handle, sshpam_err)); 943 944 if (sshpam_err != PAM_SUCCESS && sshpam_err != PAM_NEW_AUTHTOK_REQD) { 945 sshpam_account_status = 0; 946 return (sshpam_account_status); 947 } 948 949 if (sshpam_err == PAM_NEW_AUTHTOK_REQD) 950 sshpam_password_change_required(1); 951 952 sshpam_account_status = 1; 953 return (sshpam_account_status); 954} 955 956void 957do_pam_setcred(int init) 958{ 959 sshpam_err = pam_set_item(sshpam_handle, PAM_CONV, 960 (const void *)&store_conv); 961 if (sshpam_err != PAM_SUCCESS) 962 fatal("PAM: failed to set PAM_CONV: %s", 963 pam_strerror(sshpam_handle, sshpam_err)); 964 if (init) { 965 debug("PAM: establishing credentials"); 966 sshpam_err = pam_setcred(sshpam_handle, PAM_ESTABLISH_CRED); 967 } else { 968 debug("PAM: reinitializing credentials"); 969 sshpam_err = pam_setcred(sshpam_handle, PAM_REINITIALIZE_CRED); 970 } 971 if (sshpam_err == PAM_SUCCESS) { 972 sshpam_cred_established = 1; 973 return; 974 } 975 if (sshpam_authenticated) 976 fatal("PAM: pam_setcred(): %s", 977 pam_strerror(sshpam_handle, sshpam_err)); 978 else 979 debug("PAM: pam_setcred(): %s", 980 pam_strerror(sshpam_handle, sshpam_err)); 981} 982 983static int 984sshpam_tty_conv(int n, sshpam_const struct pam_message **msg, 985 struct pam_response **resp, void *data) 986{ 987 char input[PAM_MAX_MSG_SIZE]; 988 struct pam_response *reply; 989 int i; 990 991 debug3("PAM: %s called with %d messages", __func__, n); 992 993 *resp = NULL; 994 995 if (n <= 0 || n > PAM_MAX_NUM_MSG || !isatty(STDIN_FILENO)) 996 return (PAM_CONV_ERR); 997 998 if ((reply = calloc(n, sizeof(*reply))) == NULL) 999 return (PAM_CONV_ERR); 1000 1001 for (i = 0; i < n; ++i) { 1002 switch (PAM_MSG_MEMBER(msg, i, msg_style)) { 1003 case PAM_PROMPT_ECHO_OFF: 1004 reply[i].resp = 1005 read_passphrase(PAM_MSG_MEMBER(msg, i, msg), 1006 RP_ALLOW_STDIN); 1007 reply[i].resp_retcode = PAM_SUCCESS; 1008 break; 1009 case PAM_PROMPT_ECHO_ON: 1010 fprintf(stderr, "%s\n", PAM_MSG_MEMBER(msg, i, msg)); 1011 if (fgets(input, sizeof input, stdin) == NULL) 1012 input[0] = '\0'; 1013 if ((reply[i].resp = strdup(input)) == NULL) 1014 goto fail; 1015 reply[i].resp_retcode = PAM_SUCCESS; 1016 break; 1017 case PAM_ERROR_MSG: 1018 case PAM_TEXT_INFO: 1019 fprintf(stderr, "%s\n", PAM_MSG_MEMBER(msg, i, msg)); 1020 reply[i].resp_retcode = PAM_SUCCESS; 1021 break; 1022 default: 1023 goto fail; 1024 } 1025 } 1026 *resp = reply; 1027 return (PAM_SUCCESS); 1028 1029 fail: 1030 for(i = 0; i < n; i++) { 1031 free(reply[i].resp); 1032 } 1033 free(reply); 1034 return (PAM_CONV_ERR); 1035} 1036 1037static struct pam_conv tty_conv = { sshpam_tty_conv, NULL }; 1038 1039/* 1040 * XXX this should be done in the authentication phase, but ssh1 doesn't 1041 * support that 1042 */ 1043void 1044do_pam_chauthtok(void) 1045{ 1046 if (use_privsep) 1047 fatal("Password expired (unable to change with privsep)"); 1048 sshpam_err = pam_set_item(sshpam_handle, PAM_CONV, 1049 (const void *)&tty_conv); 1050 if (sshpam_err != PAM_SUCCESS) 1051 fatal("PAM: failed to set PAM_CONV: %s", 1052 pam_strerror(sshpam_handle, sshpam_err)); 1053 debug("PAM: changing password"); 1054 sshpam_err = pam_chauthtok(sshpam_handle, PAM_CHANGE_EXPIRED_AUTHTOK); 1055 if (sshpam_err != PAM_SUCCESS) 1056 fatal("PAM: pam_chauthtok(): %s", 1057 pam_strerror(sshpam_handle, sshpam_err)); 1058} 1059 1060void 1061do_pam_session(void) 1062{ 1063 debug3("PAM: opening session"); 1064 sshpam_err = pam_set_item(sshpam_handle, PAM_CONV, 1065 (const void *)&store_conv); 1066 if (sshpam_err != PAM_SUCCESS) 1067 fatal("PAM: failed to set PAM_CONV: %s", 1068 pam_strerror(sshpam_handle, sshpam_err)); 1069 sshpam_err = pam_open_session(sshpam_handle, 0); 1070 if (sshpam_err == PAM_SUCCESS) 1071 sshpam_session_open = 1; 1072 else { 1073 sshpam_session_open = 0; 1074 disable_forwarding(); 1075 error("PAM: pam_open_session(): %s", 1076 pam_strerror(sshpam_handle, sshpam_err)); 1077 } 1078 1079} 1080 1081int 1082is_pam_session_open(void) 1083{ 1084 return sshpam_session_open; 1085} 1086 1087/* 1088 * Set a PAM environment string. We need to do this so that the session 1089 * modules can handle things like Kerberos/GSI credentials that appear 1090 * during the ssh authentication process. 1091 */ 1092int 1093do_pam_putenv(char *name, char *value) 1094{ 1095 int ret = 1; 1096#ifdef HAVE_PAM_PUTENV 1097 char *compound; 1098 size_t len; 1099 1100 len = strlen(name) + strlen(value) + 2; 1101 compound = xmalloc(len); 1102 1103 snprintf(compound, len, "%s=%s", name, value); 1104 ret = pam_putenv(sshpam_handle, compound); 1105 free(compound); 1106#endif 1107 1108 return (ret); 1109} 1110 1111char ** 1112fetch_pam_child_environment(void) 1113{ 1114 return sshpam_env; 1115} 1116 1117char ** 1118fetch_pam_environment(void) 1119{ 1120 return (pam_getenvlist(sshpam_handle)); 1121} 1122 1123void 1124free_pam_environment(char **env) 1125{ 1126 char **envp; 1127 1128 if (env == NULL) 1129 return; 1130 1131 for (envp = env; *envp; envp++) 1132 free(*envp); 1133 free(env); 1134} 1135 1136/* 1137 * "Blind" conversation function for password authentication. Assumes that 1138 * echo-off prompts are for the password and stores messages for later 1139 * display. 1140 */ 1141static int 1142sshpam_passwd_conv(int n, sshpam_const struct pam_message **msg, 1143 struct pam_response **resp, void *data) 1144{ 1145 struct pam_response *reply; 1146 int i; 1147 size_t len; 1148 1149 debug3("PAM: %s called with %d messages", __func__, n); 1150 1151 *resp = NULL; 1152 1153 if (n <= 0 || n > PAM_MAX_NUM_MSG) 1154 return (PAM_CONV_ERR); 1155 1156 if ((reply = calloc(n, sizeof(*reply))) == NULL) 1157 return (PAM_CONV_ERR); 1158 1159 for (i = 0; i < n; ++i) { 1160 switch (PAM_MSG_MEMBER(msg, i, msg_style)) { 1161 case PAM_PROMPT_ECHO_OFF: 1162 if (sshpam_password == NULL) 1163 goto fail; 1164 if ((reply[i].resp = strdup(sshpam_password)) == NULL) 1165 goto fail; 1166 reply[i].resp_retcode = PAM_SUCCESS; 1167 break; 1168 case PAM_ERROR_MSG: 1169 case PAM_TEXT_INFO: 1170 len = strlen(PAM_MSG_MEMBER(msg, i, msg)); 1171 if (len > 0) { 1172 buffer_append(&loginmsg, 1173 PAM_MSG_MEMBER(msg, i, msg), len); 1174 buffer_append(&loginmsg, "\n", 1); 1175 } 1176 if ((reply[i].resp = strdup("")) == NULL) 1177 goto fail; 1178 reply[i].resp_retcode = PAM_SUCCESS; 1179 break; 1180 default: 1181 goto fail; 1182 } 1183 } 1184 *resp = reply; 1185 return (PAM_SUCCESS); 1186 1187 fail: 1188 for(i = 0; i < n; i++) { 1189 free(reply[i].resp); 1190 } 1191 free(reply); 1192 return (PAM_CONV_ERR); 1193} 1194 1195static struct pam_conv passwd_conv = { sshpam_passwd_conv, NULL }; 1196 1197/* 1198 * Attempt password authentication via PAM 1199 */ 1200int 1201sshpam_auth_passwd(Authctxt *authctxt, const char *password) 1202{ 1203 int flags = (options.permit_empty_passwd == 0 ? 1204 PAM_DISALLOW_NULL_AUTHTOK : 0); 1205 char *fake = NULL; 1206 1207 if (!options.use_pam || sshpam_handle == NULL) 1208 fatal("PAM: %s called when PAM disabled or failed to " 1209 "initialise.", __func__); 1210 1211 sshpam_password = password; 1212 sshpam_authctxt = authctxt; 1213 1214 /* 1215 * If the user logging in is invalid, or is root but is not permitted 1216 * by PermitRootLogin, use an invalid password to prevent leaking 1217 * information via timing (eg if the PAM config has a delay on fail). 1218 */ 1219 if (!authctxt->valid || (authctxt->pw->pw_uid == 0 && 1220 options.permit_root_login != PERMIT_YES)) 1221 sshpam_password = fake = fake_password(password); 1222 1223 sshpam_err = pam_set_item(sshpam_handle, PAM_CONV, 1224 (const void *)&passwd_conv); 1225 if (sshpam_err != PAM_SUCCESS) 1226 fatal("PAM: %s: failed to set PAM_CONV: %s", __func__, 1227 pam_strerror(sshpam_handle, sshpam_err)); 1228 1229 sshpam_err = pam_authenticate(sshpam_handle, flags); 1230 sshpam_password = NULL; 1231 free(fake); 1232 if (sshpam_err == PAM_MAXTRIES) 1233 sshpam_set_maxtries_reached(1); 1234 if (sshpam_err == PAM_SUCCESS && authctxt->valid) { 1235 debug("PAM: password authentication accepted for %.100s", 1236 authctxt->user); 1237 return 1; 1238 } else { 1239 debug("PAM: password authentication failed for %.100s: %s", 1240 authctxt->valid ? authctxt->user : "an illegal user", 1241 pam_strerror(sshpam_handle, sshpam_err)); 1242 return 0; 1243 } 1244} 1245 1246int 1247sshpam_get_maxtries_reached(void) 1248{ 1249 return sshpam_maxtries_reached; 1250} 1251 1252void 1253sshpam_set_maxtries_reached(int reached) 1254{ 1255 if (reached == 0 || sshpam_maxtries_reached) 1256 return; 1257 sshpam_maxtries_reached = 1; 1258 options.password_authentication = 0; 1259 options.kbd_interactive_authentication = 0; 1260 options.challenge_response_authentication = 0; 1261} 1262#endif /* USE_PAM */ 1263