1 /*-
2 * Copyright (c) 2002 Networks Associates Technology, Inc.
3 * All rights reserved.
4 *
5 * This software was developed for the FreeBSD Project by ThinkSec AS and
6 * NAI Labs, the Security Research Division of Network Associates, Inc.
7 * under DARPA/SPAWAR contract N66001-01-C-8035 ("CBOSS"), as part of the
8 * DARPA CHATS research program.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
22 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29 * SUCH DAMAGE.
30 */
31 /*
32 * Copyright (c) 2003,2004 Damien Miller <djm@mindrot.org>
33 * Copyright (c) 2003,2004 Darren Tucker <dtucker@zip.com.au>
34 *
35 * Permission to use, copy, modify, and distribute this software for any
36 * purpose with or without fee is hereby granted, provided that the above
37 * copyright notice and this permission notice appear in all copies.
38 *
39 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
40 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
41 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
42 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
43 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
44 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
45 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
46 */
47
48 /* Based on FreeBSD: src/crypto/openssh/auth2-pam-freebsd.c,v 1.11 2003/03/31 13:48:18 des */
49
50 #include "includes.h"
51
52 #include <sys/types.h>
53 #include <sys/stat.h>
54 #include <sys/wait.h>
55
56 #include <errno.h>
57 #include <signal.h>
58 #include <stdarg.h>
59 #include <string.h>
60 #include <unistd.h>
61
62 #ifdef USE_PAM
63 #if defined(HAVE_SECURITY_PAM_APPL_H)
64 #include <security/pam_appl.h>
65 #elif defined (HAVE_PAM_PAM_APPL_H)
66 #include <pam/pam_appl.h>
67 #endif
68
69 #if !defined(SSHD_PAM_SERVICE)
70 extern char *__progname;
71 # define SSHD_PAM_SERVICE __progname
72 #endif
73
74 /* OpenGroup RFC86.0 and XSSO specify no "const" on arguments */
75 #ifdef PAM_SUN_CODEBASE
76 # define sshpam_const /* Solaris, HP-UX, SunOS */
77 #else
78 # define sshpam_const const /* LinuxPAM, OpenPAM, AIX */
79 #endif
80
81 /* Ambiguity in spec: is it an array of pointers or a pointer to an array? */
82 #ifdef PAM_SUN_CODEBASE
83 # define PAM_MSG_MEMBER(msg, n, member) ((*(msg))[(n)].member)
84 #else
85 # define PAM_MSG_MEMBER(msg, n, member) ((msg)[(n)]->member)
86 #endif
87
88 #include "xmalloc.h"
89 #include "buffer.h"
90 #include "key.h"
91 #include "hostfile.h"
92 #include "auth.h"
93 #include "auth-pam.h"
94 #include "canohost.h"
95 #include "log.h"
96 #include "msg.h"
97 #include "packet.h"
98 #include "misc.h"
99 #include "servconf.h"
100 #include "ssh2.h"
101 #include "auth-options.h"
102 #ifdef GSSAPI
103 #include "ssh-gss.h"
104 #endif
105 #include "monitor_wrap.h"
106
107 extern ServerOptions options;
108 extern Buffer loginmsg;
109 extern 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
sshpam_sigchld_handler(int sig)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
pthread_exit(void * value)180 pthread_exit(void *value)
181 {
182 _exit(0);
183 }
184
185 /* ARGSUSED */
186 static int
pthread_create(sp_pthread_t * thread,const void * attr,void * (* thread_start)(void *),void * arg)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
pthread_cancel(sp_pthread_t thread)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
pthread_join(sp_pthread_t thread,void ** value)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 **
pam_getenvlist(pam_handle_t * pamh)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
sshpam_chauthtok_ruid(pam_handle_t * pamh,int flags)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
sshpam_password_change_required(int reqd)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
import_environments(Buffer * b)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
sshpam_thread_conv(int n,sshpam_const struct pam_message ** msg,struct pam_response ** resp,void * data)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 *
sshpam_thread(void * ctxtp)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
sshpam_thread_cleanup(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
sshpam_null_conv(int n,sshpam_const struct pam_message ** msg,struct pam_response ** resp,void * data)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
sshpam_store_conv(int n,sshpam_const struct pam_message ** msg,struct pam_response ** resp,void * data)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
sshpam_cleanup(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
sshpam_init(Authctxt * authctxt)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 *
sshpam_init_ctx(Authctxt * authctxt)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
sshpam_query(void * ctx,char ** name,char ** info,u_int * num,char *** prompts,u_int ** echo_on)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 *
fake_password(const char * wire_password)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
sshpam_respond(void * ctx,u_int num,char ** resp)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
sshpam_free_ctx(void * ctxtp)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
start_pam(Authctxt * authctxt)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
finish_pam(void)927 finish_pam(void)
928 {
929 sshpam_cleanup();
930 }
931
932 u_int
do_pam_account(void)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
do_pam_setcred(int init)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
sshpam_tty_conv(int n,sshpam_const struct pam_message ** msg,struct pam_response ** resp,void * data)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
do_pam_chauthtok(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
do_pam_session(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
is_pam_session_open(void)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
do_pam_putenv(char * name,char * value)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 **
fetch_pam_child_environment(void)1111 fetch_pam_child_environment(void)
1112 {
1113 return sshpam_env;
1114 }
1115
1116 char **
fetch_pam_environment(void)1117 fetch_pam_environment(void)
1118 {
1119 return (pam_getenvlist(sshpam_handle));
1120 }
1121
1122 void
free_pam_environment(char ** env)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
sshpam_passwd_conv(int n,sshpam_const struct pam_message ** msg,struct pam_response ** resp,void * data)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
sshpam_auth_passwd(Authctxt * authctxt,const char * password)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
sshpam_get_maxtries_reached(void)1246 sshpam_get_maxtries_reached(void)
1247 {
1248 return sshpam_maxtries_reached;
1249 }
1250
1251 void
sshpam_set_maxtries_reached(int reached)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