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 Exp $ */
49 #include "includes.h"
50
51 #include <sys/types.h>
52 #include <sys/stat.h>
53 #include <sys/wait.h>
54
55 #include <errno.h>
56 #include <signal.h>
57 #include <stdarg.h>
58 #include <string.h>
59 #include <unistd.h>
60
61 #ifdef USE_PAM
62 #if defined(HAVE_SECURITY_PAM_APPL_H)
63 #include <security/pam_appl.h>
64 #elif defined (HAVE_PAM_PAM_APPL_H)
65 #include <pam/pam_appl.h>
66 #endif
67
68 /* OpenGroup RFC86.0 and XSSO specify no "const" on arguments */
69 #ifdef PAM_SUN_CODEBASE
70 # define sshpam_const /* Solaris, HP-UX, AIX */
71 #else
72 # define sshpam_const const /* LinuxPAM, OpenPAM */
73 #endif
74
75 /* Ambiguity in spec: is it an array of pointers or a pointer to an array? */
76 #ifdef PAM_SUN_CODEBASE
77 # define PAM_MSG_MEMBER(msg, n, member) ((*(msg))[(n)].member)
78 #else
79 # define PAM_MSG_MEMBER(msg, n, member) ((msg)[(n)]->member)
80 #endif
81
82 #include "xmalloc.h"
83 #include "buffer.h"
84 #include "key.h"
85 #include "hostfile.h"
86 #include "auth.h"
87 #include "auth-pam.h"
88 #include "canohost.h"
89 #include "log.h"
90 #include "msg.h"
91 #include "packet.h"
92 #include "misc.h"
93 #include "servconf.h"
94 #include "ssh2.h"
95 #include "auth-options.h"
96 #ifdef GSSAPI
97 #include "ssh-gss.h"
98 #endif
99 #include "monitor_wrap.h"
100
101 extern ServerOptions options;
102 extern Buffer loginmsg;
103 extern int compat20;
104 extern u_int utmp_len;
105
106 /* so we don't silently change behaviour */
107 #ifdef USE_POSIX_THREADS
108 # error "USE_POSIX_THREADS replaced by UNSUPPORTED_POSIX_THREADS_HACK"
109 #endif
110
111 /*
112 * Formerly known as USE_POSIX_THREADS, using this is completely unsupported
113 * and generally a bad idea. Use at own risk and do not expect support if
114 * this breaks.
115 */
116 #ifdef UNSUPPORTED_POSIX_THREADS_HACK
117 #include <pthread.h>
118 /*
119 * Avoid namespace clash when *not* using pthreads for systems *with*
120 * pthreads, which unconditionally define pthread_t via sys/types.h
121 * (e.g. Linux)
122 */
123 typedef pthread_t sp_pthread_t;
124 #else
125 typedef pid_t sp_pthread_t;
126 #endif
127
128 struct pam_ctxt {
129 sp_pthread_t pam_thread;
130 int pam_psock;
131 int pam_csock;
132 int pam_done;
133 };
134
135 static void sshpam_free_ctx(void *);
136 static struct pam_ctxt *cleanup_ctxt;
137
138 #ifndef UNSUPPORTED_POSIX_THREADS_HACK
139 /*
140 * Simulate threads with processes.
141 */
142
143 static int sshpam_thread_status = -1;
144 static mysig_t sshpam_oldsig;
145
146 static void
sshpam_sigchld_handler(int sig)147 sshpam_sigchld_handler(int sig)
148 {
149 signal(SIGCHLD, SIG_DFL);
150 if (cleanup_ctxt == NULL)
151 return; /* handler called after PAM cleanup, shouldn't happen */
152 if (waitpid(cleanup_ctxt->pam_thread, &sshpam_thread_status, WNOHANG)
153 <= 0) {
154 /* PAM thread has not exitted, privsep slave must have */
155 kill(cleanup_ctxt->pam_thread, SIGTERM);
156 if (waitpid(cleanup_ctxt->pam_thread, &sshpam_thread_status, 0)
157 <= 0)
158 return; /* could not wait */
159 }
160 if (WIFSIGNALED(sshpam_thread_status) &&
161 WTERMSIG(sshpam_thread_status) == SIGTERM)
162 return; /* terminated by pthread_cancel */
163 if (!WIFEXITED(sshpam_thread_status))
164 sigdie("PAM: authentication thread exited unexpectedly");
165 if (WEXITSTATUS(sshpam_thread_status) != 0)
166 sigdie("PAM: authentication thread exited uncleanly");
167 }
168
169 /* ARGSUSED */
170 static void
pthread_exit(void * value)171 pthread_exit(void *value)
172 {
173 _exit(0);
174 }
175
176 /* ARGSUSED */
177 static int
pthread_create(sp_pthread_t * thread,const void * attr,void * (* thread_start)(void *),void * arg)178 pthread_create(sp_pthread_t *thread, const void *attr,
179 void *(*thread_start)(void *), void *arg)
180 {
181 pid_t pid;
182 struct pam_ctxt *ctx = arg;
183
184 sshpam_thread_status = -1;
185 switch ((pid = fork())) {
186 case -1:
187 error("fork(): %s", strerror(errno));
188 return (-1);
189 case 0:
190 close(ctx->pam_psock);
191 ctx->pam_psock = -1;
192 thread_start(arg);
193 _exit(1);
194 default:
195 *thread = pid;
196 close(ctx->pam_csock);
197 ctx->pam_csock = -1;
198 sshpam_oldsig = signal(SIGCHLD, sshpam_sigchld_handler);
199 return (0);
200 }
201 }
202
203 static int
pthread_cancel(sp_pthread_t thread)204 pthread_cancel(sp_pthread_t thread)
205 {
206 signal(SIGCHLD, sshpam_oldsig);
207 return (kill(thread, SIGTERM));
208 }
209
210 /* ARGSUSED */
211 static int
pthread_join(sp_pthread_t thread,void ** value)212 pthread_join(sp_pthread_t thread, void **value)
213 {
214 int status;
215
216 if (sshpam_thread_status != -1)
217 return (sshpam_thread_status);
218 signal(SIGCHLD, sshpam_oldsig);
219 waitpid(thread, &status, 0);
220 return (status);
221 }
222 #endif
223
224
225 static pam_handle_t *sshpam_handle = NULL;
226 static int sshpam_err = 0;
227 static int sshpam_authenticated = 0;
228 static int sshpam_session_open = 0;
229 static int sshpam_cred_established = 0;
230 static int sshpam_account_status = -1;
231 static char **sshpam_env = NULL;
232 static Authctxt *sshpam_authctxt = NULL;
233 static const char *sshpam_password = NULL;
234 static char badpw[] = "\b\n\r\177INCORRECT";
235
236 /* Some PAM implementations don't implement this */
237 #ifndef HAVE_PAM_GETENVLIST
238 static char **
pam_getenvlist(pam_handle_t * pamh)239 pam_getenvlist(pam_handle_t *pamh)
240 {
241 /*
242 * XXX - If necessary, we can still support envrionment passing
243 * for platforms without pam_getenvlist by searching for known
244 * env vars (e.g. KRB5CCNAME) from the PAM environment.
245 */
246 return NULL;
247 }
248 #endif
249
250 /*
251 * Some platforms, notably Solaris, do not enforce password complexity
252 * rules during pam_chauthtok() if the real uid of the calling process
253 * is 0, on the assumption that it's being called by "passwd" run by root.
254 * This wraps pam_chauthtok and sets/restore the real uid so PAM will do
255 * the right thing.
256 */
257 #ifdef SSHPAM_CHAUTHTOK_NEEDS_RUID
258 static int
sshpam_chauthtok_ruid(pam_handle_t * pamh,int flags)259 sshpam_chauthtok_ruid(pam_handle_t *pamh, int flags)
260 {
261 int result;
262
263 if (sshpam_authctxt == NULL)
264 fatal("PAM: sshpam_authctxt not initialized");
265 if (setreuid(sshpam_authctxt->pw->pw_uid, -1) == -1)
266 fatal("%s: setreuid failed: %s", __func__, strerror(errno));
267 result = pam_chauthtok(pamh, flags);
268 if (setreuid(0, -1) == -1)
269 fatal("%s: setreuid failed: %s", __func__, strerror(errno));
270 return result;
271 }
272 # define pam_chauthtok(a,b) (sshpam_chauthtok_ruid((a), (b)))
273 #endif
274
275 void
sshpam_password_change_required(int reqd)276 sshpam_password_change_required(int reqd)
277 {
278 debug3("%s %d", __func__, reqd);
279 if (sshpam_authctxt == NULL)
280 fatal("%s: PAM authctxt not initialized", __func__);
281 sshpam_authctxt->force_pwchange = reqd;
282 if (reqd) {
283 no_port_forwarding_flag |= 2;
284 no_agent_forwarding_flag |= 2;
285 no_x11_forwarding_flag |= 2;
286 } else {
287 no_port_forwarding_flag &= ~2;
288 no_agent_forwarding_flag &= ~2;
289 no_x11_forwarding_flag &= ~2;
290 }
291 }
292
293 /* Import regular and PAM environment from subprocess */
294 static void
import_environments(Buffer * b)295 import_environments(Buffer *b)
296 {
297 char *env;
298 u_int i, num_env;
299 int err;
300
301 debug3("PAM: %s entering", __func__);
302
303 #ifndef UNSUPPORTED_POSIX_THREADS_HACK
304 /* Import variables set by do_pam_account */
305 sshpam_account_status = buffer_get_int(b);
306 sshpam_password_change_required(buffer_get_int(b));
307
308 /* Import environment from subprocess */
309 num_env = buffer_get_int(b);
310 if (num_env > 1024)
311 fatal("%s: received %u environment variables, expected <= 1024",
312 __func__, num_env);
313 sshpam_env = xcalloc(num_env + 1, sizeof(*sshpam_env));
314 debug3("PAM: num env strings %d", num_env);
315 for(i = 0; i < num_env; i++)
316 sshpam_env[i] = buffer_get_string(b, NULL);
317
318 sshpam_env[num_env] = NULL;
319
320 /* Import PAM environment from subprocess */
321 num_env = buffer_get_int(b);
322 debug("PAM: num PAM env strings %d", num_env);
323 for(i = 0; i < num_env; i++) {
324 env = buffer_get_string(b, NULL);
325
326 #ifdef HAVE_PAM_PUTENV
327 /* Errors are not fatal here */
328 if ((err = pam_putenv(sshpam_handle, env)) != PAM_SUCCESS) {
329 error("PAM: pam_putenv: %s",
330 pam_strerror(sshpam_handle, sshpam_err));
331 }
332 #endif
333 }
334 #endif
335 }
336
337 /*
338 * Conversation function for authentication thread.
339 */
340 static int
sshpam_thread_conv(int n,sshpam_const struct pam_message ** msg,struct pam_response ** resp,void * data)341 sshpam_thread_conv(int n, sshpam_const struct pam_message **msg,
342 struct pam_response **resp, void *data)
343 {
344 Buffer buffer;
345 struct pam_ctxt *ctxt;
346 struct pam_response *reply;
347 int i;
348
349 debug3("PAM: %s entering, %d messages", __func__, n);
350 *resp = NULL;
351
352 if (data == NULL) {
353 error("PAM: conversation function passed a null context");
354 return (PAM_CONV_ERR);
355 }
356 ctxt = data;
357 if (n <= 0 || n > PAM_MAX_NUM_MSG)
358 return (PAM_CONV_ERR);
359
360 if ((reply = calloc(n, sizeof(*reply))) == NULL)
361 return (PAM_CONV_ERR);
362
363 buffer_init(&buffer);
364 for (i = 0; i < n; ++i) {
365 switch (PAM_MSG_MEMBER(msg, i, msg_style)) {
366 case PAM_PROMPT_ECHO_OFF:
367 buffer_put_cstring(&buffer,
368 PAM_MSG_MEMBER(msg, i, msg));
369 if (ssh_msg_send(ctxt->pam_csock,
370 PAM_MSG_MEMBER(msg, i, msg_style), &buffer) == -1)
371 goto fail;
372 if (ssh_msg_recv(ctxt->pam_csock, &buffer) == -1)
373 goto fail;
374 if (buffer_get_char(&buffer) != PAM_AUTHTOK)
375 goto fail;
376 reply[i].resp = buffer_get_string(&buffer, NULL);
377 break;
378 case PAM_PROMPT_ECHO_ON:
379 buffer_put_cstring(&buffer,
380 PAM_MSG_MEMBER(msg, i, msg));
381 if (ssh_msg_send(ctxt->pam_csock,
382 PAM_MSG_MEMBER(msg, i, msg_style), &buffer) == -1)
383 goto fail;
384 if (ssh_msg_recv(ctxt->pam_csock, &buffer) == -1)
385 goto fail;
386 if (buffer_get_char(&buffer) != PAM_AUTHTOK)
387 goto fail;
388 reply[i].resp = buffer_get_string(&buffer, NULL);
389 break;
390 case PAM_ERROR_MSG:
391 buffer_put_cstring(&buffer,
392 PAM_MSG_MEMBER(msg, i, msg));
393 if (ssh_msg_send(ctxt->pam_csock,
394 PAM_MSG_MEMBER(msg, i, msg_style), &buffer) == -1)
395 goto fail;
396 break;
397 case PAM_TEXT_INFO:
398 buffer_put_cstring(&buffer,
399 PAM_MSG_MEMBER(msg, i, msg));
400 if (ssh_msg_send(ctxt->pam_csock,
401 PAM_MSG_MEMBER(msg, i, msg_style), &buffer) == -1)
402 goto fail;
403 break;
404 default:
405 goto fail;
406 }
407 buffer_clear(&buffer);
408 }
409 buffer_free(&buffer);
410 *resp = reply;
411 return (PAM_SUCCESS);
412
413 fail:
414 for(i = 0; i < n; i++) {
415 free(reply[i].resp);
416 }
417 free(reply);
418 buffer_free(&buffer);
419 return (PAM_CONV_ERR);
420 }
421
422 /*
423 * Authentication thread.
424 */
425 static void *
sshpam_thread(void * ctxtp)426 sshpam_thread(void *ctxtp)
427 {
428 struct pam_ctxt *ctxt = ctxtp;
429 Buffer buffer;
430 struct pam_conv sshpam_conv;
431 int flags = (options.permit_empty_passwd == 0 ?
432 PAM_DISALLOW_NULL_AUTHTOK : 0);
433 #ifndef UNSUPPORTED_POSIX_THREADS_HACK
434 extern char **environ;
435 char **env_from_pam;
436 u_int i;
437 const char *pam_user;
438 const char **ptr_pam_user = &pam_user;
439 char *tz = getenv("TZ");
440
441 sshpam_err = pam_get_item(sshpam_handle, PAM_USER,
442 (sshpam_const void **)ptr_pam_user);
443 if (sshpam_err != PAM_SUCCESS)
444 goto auth_fail;
445
446 environ[0] = NULL;
447 if (tz != NULL)
448 if (setenv("TZ", tz, 1) == -1)
449 error("PAM: could not set TZ environment: %s",
450 strerror(errno));
451
452 if (sshpam_authctxt != NULL) {
453 setproctitle("%s [pam]",
454 sshpam_authctxt->valid ? pam_user : "unknown");
455 }
456 #endif
457
458 sshpam_conv.conv = sshpam_thread_conv;
459 sshpam_conv.appdata_ptr = ctxt;
460
461 if (sshpam_authctxt == NULL)
462 fatal("%s: PAM authctxt not initialized", __func__);
463
464 buffer_init(&buffer);
465 sshpam_err = pam_set_item(sshpam_handle, PAM_CONV,
466 (const void *)&sshpam_conv);
467 if (sshpam_err != PAM_SUCCESS)
468 goto auth_fail;
469 sshpam_err = pam_authenticate(sshpam_handle, flags);
470 if (sshpam_err != PAM_SUCCESS)
471 goto auth_fail;
472
473 if (compat20) {
474 if (!do_pam_account()) {
475 sshpam_err = PAM_ACCT_EXPIRED;
476 goto auth_fail;
477 }
478 if (sshpam_authctxt->force_pwchange) {
479 sshpam_err = pam_chauthtok(sshpam_handle,
480 PAM_CHANGE_EXPIRED_AUTHTOK);
481 if (sshpam_err != PAM_SUCCESS)
482 goto auth_fail;
483 sshpam_password_change_required(0);
484 }
485 }
486
487 buffer_put_cstring(&buffer, "OK");
488
489 #ifndef UNSUPPORTED_POSIX_THREADS_HACK
490 /* Export variables set by do_pam_account */
491 buffer_put_int(&buffer, sshpam_account_status);
492 buffer_put_int(&buffer, sshpam_authctxt->force_pwchange);
493
494 /* Export any environment strings set in child */
495 for(i = 0; environ[i] != NULL; i++)
496 ; /* Count */
497 buffer_put_int(&buffer, i);
498 for(i = 0; environ[i] != NULL; i++)
499 buffer_put_cstring(&buffer, environ[i]);
500
501 /* Export any environment strings set by PAM in child */
502 env_from_pam = pam_getenvlist(sshpam_handle);
503 for(i = 0; env_from_pam != NULL && env_from_pam[i] != NULL; i++)
504 ; /* Count */
505 buffer_put_int(&buffer, i);
506 for(i = 0; env_from_pam != NULL && env_from_pam[i] != NULL; i++)
507 buffer_put_cstring(&buffer, env_from_pam[i]);
508 #endif /* UNSUPPORTED_POSIX_THREADS_HACK */
509
510 /* XXX - can't do much about an error here */
511 ssh_msg_send(ctxt->pam_csock, sshpam_err, &buffer);
512 buffer_free(&buffer);
513 pthread_exit(NULL);
514
515 auth_fail:
516 buffer_put_cstring(&buffer,
517 pam_strerror(sshpam_handle, sshpam_err));
518 /* XXX - can't do much about an error here */
519 if (sshpam_err == PAM_ACCT_EXPIRED)
520 ssh_msg_send(ctxt->pam_csock, PAM_ACCT_EXPIRED, &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 extern char *__progname;
624 const char *pam_rhost, *pam_user, *user = authctxt->user;
625 const char **ptr_pam_user = &pam_user;
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 = get_remote_name_or_ip(utmp_len, 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 Buffer buffer;
718 struct pam_ctxt *ctxt = ctx;
719 size_t plen;
720 u_char type;
721 char *msg;
722 size_t len, mlen;
723
724 debug3("PAM: %s entering", __func__);
725 buffer_init(&buffer);
726 *name = xstrdup("");
727 *info = xstrdup("");
728 *prompts = xmalloc(sizeof(char *));
729 **prompts = NULL;
730 plen = 0;
731 *echo_on = xmalloc(sizeof(u_int));
732 while (ssh_msg_recv(ctxt->pam_psock, &buffer) == 0) {
733 type = buffer_get_char(&buffer);
734 msg = buffer_get_string(&buffer, NULL);
735 mlen = strlen(msg);
736 switch (type) {
737 case PAM_PROMPT_ECHO_ON:
738 case PAM_PROMPT_ECHO_OFF:
739 *num = 1;
740 len = plen + mlen + 1;
741 **prompts = xrealloc(**prompts, 1, len);
742 strlcpy(**prompts + plen, msg, len - plen);
743 plen += mlen;
744 **echo_on = (type == PAM_PROMPT_ECHO_ON);
745 free(msg);
746 return (0);
747 case PAM_ERROR_MSG:
748 case PAM_TEXT_INFO:
749 /* accumulate messages */
750 len = plen + mlen + 2;
751 **prompts = xrealloc(**prompts, 1, len);
752 strlcpy(**prompts + plen, msg, len - plen);
753 plen += mlen;
754 strlcat(**prompts + plen, "\n", len - plen);
755 plen++;
756 free(msg);
757 break;
758 case PAM_ACCT_EXPIRED:
759 sshpam_account_status = 0;
760 /* FALLTHROUGH */
761 case PAM_AUTH_ERR:
762 debug3("PAM: %s", pam_strerror(sshpam_handle, type));
763 if (**prompts != NULL && strlen(**prompts) != 0) {
764 *info = **prompts;
765 **prompts = NULL;
766 *num = 0;
767 **echo_on = 0;
768 ctxt->pam_done = -1;
769 free(msg);
770 return 0;
771 }
772 /* FALLTHROUGH */
773 case PAM_SUCCESS:
774 if (**prompts != NULL) {
775 /* drain any accumulated messages */
776 debug("PAM: %s", **prompts);
777 buffer_append(&loginmsg, **prompts,
778 strlen(**prompts));
779 free(**prompts);
780 **prompts = NULL;
781 }
782 if (type == PAM_SUCCESS) {
783 if (!sshpam_authctxt->valid ||
784 (sshpam_authctxt->pw->pw_uid == 0 &&
785 options.permit_root_login != PERMIT_YES))
786 fatal("Internal error: PAM auth "
787 "succeeded when it should have "
788 "failed");
789 import_environments(&buffer);
790 *num = 0;
791 **echo_on = 0;
792 ctxt->pam_done = 1;
793 free(msg);
794 return (0);
795 }
796 error("PAM: %s for %s%.100s from %.100s", msg,
797 sshpam_authctxt->valid ? "" : "illegal user ",
798 sshpam_authctxt->user,
799 get_remote_name_or_ip(utmp_len, options.use_dns));
800 /* FALLTHROUGH */
801 default:
802 *num = 0;
803 **echo_on = 0;
804 free(msg);
805 ctxt->pam_done = -1;
806 return (-1);
807 }
808 }
809 return (-1);
810 }
811
812 /* XXX - see also comment in auth-chall.c:verify_response */
813 static int
sshpam_respond(void * ctx,u_int num,char ** resp)814 sshpam_respond(void *ctx, u_int num, char **resp)
815 {
816 Buffer buffer;
817 struct pam_ctxt *ctxt = ctx;
818
819 debug2("PAM: %s entering, %u responses", __func__, num);
820 switch (ctxt->pam_done) {
821 case 1:
822 sshpam_authenticated = 1;
823 return (0);
824 case 0:
825 break;
826 default:
827 return (-1);
828 }
829 if (num != 1) {
830 error("PAM: expected one response, got %u", num);
831 return (-1);
832 }
833 buffer_init(&buffer);
834 if (sshpam_authctxt->valid &&
835 (sshpam_authctxt->pw->pw_uid != 0 ||
836 options.permit_root_login == PERMIT_YES))
837 buffer_put_cstring(&buffer, *resp);
838 else
839 buffer_put_cstring(&buffer, badpw);
840 if (ssh_msg_send(ctxt->pam_psock, PAM_AUTHTOK, &buffer) == -1) {
841 buffer_free(&buffer);
842 return (-1);
843 }
844 buffer_free(&buffer);
845 return (1);
846 }
847
848 static void
sshpam_free_ctx(void * ctxtp)849 sshpam_free_ctx(void *ctxtp)
850 {
851 struct pam_ctxt *ctxt = ctxtp;
852
853 debug3("PAM: %s entering", __func__);
854 sshpam_thread_cleanup();
855 free(ctxt);
856 /*
857 * We don't call sshpam_cleanup() here because we may need the PAM
858 * handle at a later stage, e.g. when setting up a session. It's
859 * still on the cleanup list, so pam_end() *will* be called before
860 * the server process terminates.
861 */
862 }
863
864 KbdintDevice sshpam_device = {
865 "pam",
866 sshpam_init_ctx,
867 sshpam_query,
868 sshpam_respond,
869 sshpam_free_ctx
870 };
871
872 KbdintDevice mm_sshpam_device = {
873 "pam",
874 mm_sshpam_init_ctx,
875 mm_sshpam_query,
876 mm_sshpam_respond,
877 mm_sshpam_free_ctx
878 };
879
880 /*
881 * This replaces auth-pam.c
882 */
883 void
start_pam(Authctxt * authctxt)884 start_pam(Authctxt *authctxt)
885 {
886 if (!options.use_pam)
887 fatal("PAM: initialisation requested when UsePAM=no");
888
889 if (sshpam_init(authctxt) == -1)
890 fatal("PAM: initialisation failed");
891 }
892
893 void
finish_pam(void)894 finish_pam(void)
895 {
896 sshpam_cleanup();
897 }
898
899 u_int
do_pam_account(void)900 do_pam_account(void)
901 {
902 debug("%s: called", __func__);
903 if (sshpam_account_status != -1)
904 return (sshpam_account_status);
905
906 sshpam_err = pam_acct_mgmt(sshpam_handle, 0);
907 debug3("PAM: %s pam_acct_mgmt = %d (%s)", __func__, sshpam_err,
908 pam_strerror(sshpam_handle, sshpam_err));
909
910 if (sshpam_err != PAM_SUCCESS && sshpam_err != PAM_NEW_AUTHTOK_REQD) {
911 sshpam_account_status = 0;
912 return (sshpam_account_status);
913 }
914
915 if (sshpam_err == PAM_NEW_AUTHTOK_REQD)
916 sshpam_password_change_required(1);
917
918 sshpam_account_status = 1;
919 return (sshpam_account_status);
920 }
921
922 void
do_pam_set_tty(const char * tty)923 do_pam_set_tty(const char *tty)
924 {
925 if (tty != NULL) {
926 debug("PAM: setting PAM_TTY to \"%s\"", tty);
927 sshpam_err = pam_set_item(sshpam_handle, PAM_TTY, tty);
928 if (sshpam_err != PAM_SUCCESS)
929 fatal("PAM: failed to set PAM_TTY: %s",
930 pam_strerror(sshpam_handle, sshpam_err));
931 }
932 }
933
934 void
do_pam_setcred(int init)935 do_pam_setcred(int init)
936 {
937 sshpam_err = pam_set_item(sshpam_handle, PAM_CONV,
938 (const void *)&store_conv);
939 if (sshpam_err != PAM_SUCCESS)
940 fatal("PAM: failed to set PAM_CONV: %s",
941 pam_strerror(sshpam_handle, sshpam_err));
942 if (init) {
943 debug("PAM: establishing credentials");
944 sshpam_err = pam_setcred(sshpam_handle, PAM_ESTABLISH_CRED);
945 } else {
946 debug("PAM: reinitializing credentials");
947 sshpam_err = pam_setcred(sshpam_handle, PAM_REINITIALIZE_CRED);
948 }
949 if (sshpam_err == PAM_SUCCESS) {
950 sshpam_cred_established = 1;
951 return;
952 }
953 if (sshpam_authenticated)
954 fatal("PAM: pam_setcred(): %s",
955 pam_strerror(sshpam_handle, sshpam_err));
956 else
957 debug("PAM: pam_setcred(): %s",
958 pam_strerror(sshpam_handle, sshpam_err));
959 }
960
961 static int
sshpam_tty_conv(int n,sshpam_const struct pam_message ** msg,struct pam_response ** resp,void * data)962 sshpam_tty_conv(int n, sshpam_const struct pam_message **msg,
963 struct pam_response **resp, void *data)
964 {
965 char input[PAM_MAX_MSG_SIZE];
966 struct pam_response *reply;
967 int i;
968
969 debug3("PAM: %s called with %d messages", __func__, n);
970
971 *resp = NULL;
972
973 if (n <= 0 || n > PAM_MAX_NUM_MSG || !isatty(STDIN_FILENO))
974 return (PAM_CONV_ERR);
975
976 if ((reply = calloc(n, sizeof(*reply))) == NULL)
977 return (PAM_CONV_ERR);
978
979 for (i = 0; i < n; ++i) {
980 switch (PAM_MSG_MEMBER(msg, i, msg_style)) {
981 case PAM_PROMPT_ECHO_OFF:
982 reply[i].resp =
983 read_passphrase(PAM_MSG_MEMBER(msg, i, msg),
984 RP_ALLOW_STDIN);
985 reply[i].resp_retcode = PAM_SUCCESS;
986 break;
987 case PAM_PROMPT_ECHO_ON:
988 fprintf(stderr, "%s\n", PAM_MSG_MEMBER(msg, i, msg));
989 if (fgets(input, sizeof input, stdin) == NULL)
990 input[0] = '\0';
991 if ((reply[i].resp = strdup(input)) == NULL)
992 goto fail;
993 reply[i].resp_retcode = PAM_SUCCESS;
994 break;
995 case PAM_ERROR_MSG:
996 case PAM_TEXT_INFO:
997 fprintf(stderr, "%s\n", PAM_MSG_MEMBER(msg, i, msg));
998 reply[i].resp_retcode = PAM_SUCCESS;
999 break;
1000 default:
1001 goto fail;
1002 }
1003 }
1004 *resp = reply;
1005 return (PAM_SUCCESS);
1006
1007 fail:
1008 for(i = 0; i < n; i++) {
1009 free(reply[i].resp);
1010 }
1011 free(reply);
1012 return (PAM_CONV_ERR);
1013 }
1014
1015 static struct pam_conv tty_conv = { sshpam_tty_conv, NULL };
1016
1017 /*
1018 * XXX this should be done in the authentication phase, but ssh1 doesn't
1019 * support that
1020 */
1021 void
do_pam_chauthtok(void)1022 do_pam_chauthtok(void)
1023 {
1024 if (use_privsep)
1025 fatal("Password expired (unable to change with privsep)");
1026 sshpam_err = pam_set_item(sshpam_handle, PAM_CONV,
1027 (const void *)&tty_conv);
1028 if (sshpam_err != PAM_SUCCESS)
1029 fatal("PAM: failed to set PAM_CONV: %s",
1030 pam_strerror(sshpam_handle, sshpam_err));
1031 debug("PAM: changing password");
1032 sshpam_err = pam_chauthtok(sshpam_handle, PAM_CHANGE_EXPIRED_AUTHTOK);
1033 if (sshpam_err != PAM_SUCCESS)
1034 fatal("PAM: pam_chauthtok(): %s",
1035 pam_strerror(sshpam_handle, sshpam_err));
1036 }
1037
1038 void
do_pam_session(void)1039 do_pam_session(void)
1040 {
1041 debug3("PAM: opening session");
1042 sshpam_err = pam_set_item(sshpam_handle, PAM_CONV,
1043 (const void *)&store_conv);
1044 if (sshpam_err != PAM_SUCCESS)
1045 fatal("PAM: failed to set PAM_CONV: %s",
1046 pam_strerror(sshpam_handle, sshpam_err));
1047 sshpam_err = pam_open_session(sshpam_handle, 0);
1048 if (sshpam_err == PAM_SUCCESS)
1049 sshpam_session_open = 1;
1050 else {
1051 sshpam_session_open = 0;
1052 disable_forwarding();
1053 error("PAM: pam_open_session(): %s",
1054 pam_strerror(sshpam_handle, sshpam_err));
1055 }
1056
1057 }
1058
1059 int
is_pam_session_open(void)1060 is_pam_session_open(void)
1061 {
1062 return sshpam_session_open;
1063 }
1064
1065 /*
1066 * Set a PAM environment string. We need to do this so that the session
1067 * modules can handle things like Kerberos/GSI credentials that appear
1068 * during the ssh authentication process.
1069 */
1070 int
do_pam_putenv(char * name,char * value)1071 do_pam_putenv(char *name, char *value)
1072 {
1073 int ret = 1;
1074 #ifdef HAVE_PAM_PUTENV
1075 char *compound;
1076 size_t len;
1077
1078 len = strlen(name) + strlen(value) + 2;
1079 compound = xmalloc(len);
1080
1081 snprintf(compound, len, "%s=%s", name, value);
1082 ret = pam_putenv(sshpam_handle, compound);
1083 free(compound);
1084 #endif
1085
1086 return (ret);
1087 }
1088
1089 char **
fetch_pam_child_environment(void)1090 fetch_pam_child_environment(void)
1091 {
1092 return sshpam_env;
1093 }
1094
1095 char **
fetch_pam_environment(void)1096 fetch_pam_environment(void)
1097 {
1098 return (pam_getenvlist(sshpam_handle));
1099 }
1100
1101 void
free_pam_environment(char ** env)1102 free_pam_environment(char **env)
1103 {
1104 char **envp;
1105
1106 if (env == NULL)
1107 return;
1108
1109 for (envp = env; *envp; envp++)
1110 free(*envp);
1111 free(env);
1112 }
1113
1114 /*
1115 * "Blind" conversation function for password authentication. Assumes that
1116 * echo-off prompts are for the password and stores messages for later
1117 * display.
1118 */
1119 static int
sshpam_passwd_conv(int n,sshpam_const struct pam_message ** msg,struct pam_response ** resp,void * data)1120 sshpam_passwd_conv(int n, sshpam_const struct pam_message **msg,
1121 struct pam_response **resp, void *data)
1122 {
1123 struct pam_response *reply;
1124 int i;
1125 size_t len;
1126
1127 debug3("PAM: %s called with %d messages", __func__, n);
1128
1129 *resp = NULL;
1130
1131 if (n <= 0 || n > PAM_MAX_NUM_MSG)
1132 return (PAM_CONV_ERR);
1133
1134 if ((reply = calloc(n, sizeof(*reply))) == NULL)
1135 return (PAM_CONV_ERR);
1136
1137 for (i = 0; i < n; ++i) {
1138 switch (PAM_MSG_MEMBER(msg, i, msg_style)) {
1139 case PAM_PROMPT_ECHO_OFF:
1140 if (sshpam_password == NULL)
1141 goto fail;
1142 if ((reply[i].resp = strdup(sshpam_password)) == NULL)
1143 goto fail;
1144 reply[i].resp_retcode = PAM_SUCCESS;
1145 break;
1146 case PAM_ERROR_MSG:
1147 case PAM_TEXT_INFO:
1148 len = strlen(PAM_MSG_MEMBER(msg, i, msg));
1149 if (len > 0) {
1150 buffer_append(&loginmsg,
1151 PAM_MSG_MEMBER(msg, i, msg), len);
1152 buffer_append(&loginmsg, "\n", 1);
1153 }
1154 if ((reply[i].resp = strdup("")) == NULL)
1155 goto fail;
1156 reply[i].resp_retcode = PAM_SUCCESS;
1157 break;
1158 default:
1159 goto fail;
1160 }
1161 }
1162 *resp = reply;
1163 return (PAM_SUCCESS);
1164
1165 fail:
1166 for(i = 0; i < n; i++) {
1167 free(reply[i].resp);
1168 }
1169 free(reply);
1170 return (PAM_CONV_ERR);
1171 }
1172
1173 static struct pam_conv passwd_conv = { sshpam_passwd_conv, NULL };
1174
1175 /*
1176 * Attempt password authentication via PAM
1177 */
1178 int
sshpam_auth_passwd(Authctxt * authctxt,const char * password)1179 sshpam_auth_passwd(Authctxt *authctxt, const char *password)
1180 {
1181 int flags = (options.permit_empty_passwd == 0 ?
1182 PAM_DISALLOW_NULL_AUTHTOK : 0);
1183
1184 if (!options.use_pam || sshpam_handle == NULL)
1185 fatal("PAM: %s called when PAM disabled or failed to "
1186 "initialise.", __func__);
1187
1188 sshpam_password = password;
1189 sshpam_authctxt = authctxt;
1190
1191 /*
1192 * If the user logging in is invalid, or is root but is not permitted
1193 * by PermitRootLogin, use an invalid password to prevent leaking
1194 * information via timing (eg if the PAM config has a delay on fail).
1195 */
1196 if (!authctxt->valid || (authctxt->pw->pw_uid == 0 &&
1197 options.permit_root_login != PERMIT_YES))
1198 sshpam_password = badpw;
1199
1200 sshpam_err = pam_set_item(sshpam_handle, PAM_CONV,
1201 (const void *)&passwd_conv);
1202 if (sshpam_err != PAM_SUCCESS)
1203 fatal("PAM: %s: failed to set PAM_CONV: %s", __func__,
1204 pam_strerror(sshpam_handle, sshpam_err));
1205
1206 sshpam_err = pam_authenticate(sshpam_handle, flags);
1207 sshpam_password = NULL;
1208 if (sshpam_err == PAM_SUCCESS && authctxt->valid) {
1209 debug("PAM: password authentication accepted for %.100s",
1210 authctxt->user);
1211 return 1;
1212 } else {
1213 debug("PAM: password authentication failed for %.100s: %s",
1214 authctxt->valid ? authctxt->user : "an illegal user",
1215 pam_strerror(sshpam_handle, sshpam_err));
1216 return 0;
1217 }
1218 }
1219 #endif /* USE_PAM */
1220