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 <stdlib.h>
60 #include <string.h>
61 #include <unistd.h>
62
63 #ifdef USE_PAM
64 #if defined(HAVE_SECURITY_PAM_APPL_H)
65 #include <security/pam_appl.h>
66 #elif defined (HAVE_PAM_PAM_APPL_H)
67 #include <pam/pam_appl.h>
68 #endif
69
70 #if !defined(SSHD_PAM_SERVICE)
71 extern char *__progname;
72 # define SSHD_PAM_SERVICE __progname
73 #endif
74
75 /* OpenGroup RFC86.0 and XSSO specify no "const" on arguments */
76 #ifdef PAM_SUN_CODEBASE
77 # define sshpam_const /* Solaris, HP-UX, SunOS */
78 #else
79 # define sshpam_const const /* LinuxPAM, OpenPAM, AIX */
80 #endif
81
82 /* Ambiguity in spec: is it an array of pointers or a pointer to an array? */
83 #ifdef PAM_SUN_CODEBASE
84 # define PAM_MSG_MEMBER(msg, n, member) ((*(msg))[(n)].member)
85 #else
86 # define PAM_MSG_MEMBER(msg, n, member) ((msg)[(n)]->member)
87 #endif
88
89 #include "xmalloc.h"
90 #include "sshbuf.h"
91 #include "ssherr.h"
92 #include "hostfile.h"
93 #include "auth.h"
94 #include "auth-pam.h"
95 #include "canohost.h"
96 #include "log.h"
97 #include "msg.h"
98 #include "packet.h"
99 #include "misc.h"
100 #include "servconf.h"
101 #include "ssh2.h"
102 #include "auth-options.h"
103 #include "misc.h"
104 #ifdef GSSAPI
105 #include "ssh-gss.h"
106 #endif
107 #include "monitor_wrap.h"
108 #include "blacklist_client.h"
109
110 extern ServerOptions options;
111 extern struct sshbuf *loginmsg;
112 extern u_int utmp_len;
113
114 /* so we don't silently change behaviour */
115 #ifdef USE_POSIX_THREADS
116 # error "USE_POSIX_THREADS replaced by UNSUPPORTED_POSIX_THREADS_HACK"
117 #endif
118
119 /*
120 * Formerly known as USE_POSIX_THREADS, using this is completely unsupported
121 * and generally a bad idea. Use at own risk and do not expect support if
122 * this breaks.
123 */
124 #ifdef UNSUPPORTED_POSIX_THREADS_HACK
125 #include <pthread.h>
126 /*
127 * Avoid namespace clash when *not* using pthreads for systems *with*
128 * pthreads, which unconditionally define pthread_t via sys/types.h
129 * (e.g. Linux)
130 */
131 typedef pthread_t sp_pthread_t;
132 #else
133 typedef pid_t sp_pthread_t;
134 #define pthread_exit fake_pthread_exit
135 #define pthread_create fake_pthread_create
136 #define pthread_cancel fake_pthread_cancel
137 #define pthread_join fake_pthread_join
138 #endif
139
140 struct pam_ctxt {
141 sp_pthread_t pam_thread;
142 int pam_psock;
143 int pam_csock;
144 int pam_done;
145 };
146
147 static void sshpam_free_ctx(void *);
148 static struct pam_ctxt *cleanup_ctxt;
149
150 #ifndef UNSUPPORTED_POSIX_THREADS_HACK
151 /*
152 * Simulate threads with processes.
153 */
154
155 static int sshpam_thread_status = -1;
156 static sshsig_t sshpam_oldsig;
157
158 static void
sshpam_sigchld_handler(int sig)159 sshpam_sigchld_handler(int sig)
160 {
161 ssh_signal(SIGCHLD, SIG_DFL);
162 if (cleanup_ctxt == NULL)
163 return; /* handler called after PAM cleanup, shouldn't happen */
164 if (waitpid(cleanup_ctxt->pam_thread, &sshpam_thread_status, WNOHANG)
165 <= 0) {
166 /* PAM thread has not exitted, privsep slave must have */
167 kill(cleanup_ctxt->pam_thread, SIGTERM);
168 while (waitpid(cleanup_ctxt->pam_thread,
169 &sshpam_thread_status, 0) == -1) {
170 if (errno == EINTR)
171 continue;
172 return;
173 }
174 }
175 if (WIFSIGNALED(sshpam_thread_status) &&
176 WTERMSIG(sshpam_thread_status) == SIGTERM)
177 return; /* terminated by pthread_cancel */
178 if (!WIFEXITED(sshpam_thread_status))
179 sigdie("PAM: authentication thread exited unexpectedly");
180 if (WEXITSTATUS(sshpam_thread_status) != 0)
181 sigdie("PAM: authentication thread exited uncleanly");
182 }
183
184 /* ARGSUSED */
185 static void
pthread_exit(void * value)186 pthread_exit(void *value)
187 {
188 _exit(0);
189 }
190
191 /* ARGSUSED */
192 static int
pthread_create(sp_pthread_t * thread,const void * attr,void * (* thread_start)(void *),void * arg)193 pthread_create(sp_pthread_t *thread, const void *attr,
194 void *(*thread_start)(void *), void *arg)
195 {
196 pid_t pid;
197 struct pam_ctxt *ctx = arg;
198
199 sshpam_thread_status = -1;
200 switch ((pid = fork())) {
201 case -1:
202 error("fork(): %s", strerror(errno));
203 return errno;
204 case 0:
205 close(ctx->pam_psock);
206 ctx->pam_psock = -1;
207 thread_start(arg);
208 _exit(1);
209 default:
210 *thread = pid;
211 close(ctx->pam_csock);
212 ctx->pam_csock = -1;
213 sshpam_oldsig = ssh_signal(SIGCHLD, sshpam_sigchld_handler);
214 return (0);
215 }
216 }
217
218 static int
pthread_cancel(sp_pthread_t thread)219 pthread_cancel(sp_pthread_t thread)
220 {
221 ssh_signal(SIGCHLD, sshpam_oldsig);
222 return (kill(thread, SIGTERM));
223 }
224
225 /* ARGSUSED */
226 static int
pthread_join(sp_pthread_t thread,void ** value)227 pthread_join(sp_pthread_t thread, void **value)
228 {
229 int status;
230
231 if (sshpam_thread_status != -1)
232 return (sshpam_thread_status);
233 ssh_signal(SIGCHLD, sshpam_oldsig);
234 while (waitpid(thread, &status, 0) == -1) {
235 if (errno == EINTR)
236 continue;
237 fatal("%s: waitpid: %s", __func__, strerror(errno));
238 }
239 return (status);
240 }
241 #endif
242
243
244 static pam_handle_t *sshpam_handle = NULL;
245 static int sshpam_err = 0;
246 static int sshpam_authenticated = 0;
247 static int sshpam_session_open = 0;
248 static int sshpam_cred_established = 0;
249 static int sshpam_account_status = -1;
250 static int sshpam_maxtries_reached = 0;
251 static char **sshpam_env = NULL;
252 static Authctxt *sshpam_authctxt = NULL;
253 static const char *sshpam_password = NULL;
254 static char *sshpam_rhost = NULL;
255 static char *sshpam_laddr = NULL;
256
257 /* Some PAM implementations don't implement this */
258 #ifndef HAVE_PAM_GETENVLIST
259 static char **
pam_getenvlist(pam_handle_t * pamh)260 pam_getenvlist(pam_handle_t *pamh)
261 {
262 /*
263 * XXX - If necessary, we can still support environment passing
264 * for platforms without pam_getenvlist by searching for known
265 * env vars (e.g. KRB5CCNAME) from the PAM environment.
266 */
267 return NULL;
268 }
269 #endif
270
271 #ifndef HAVE_PAM_PUTENV
272 static int
pam_putenv(pam_handle_t * pamh,const char * name_value)273 pam_putenv(pam_handle_t *pamh, const char *name_value)
274 {
275 return PAM_SUCCESS;
276 }
277 #endif /* HAVE_PAM_PUTENV */
278
279 /*
280 * Some platforms, notably Solaris, do not enforce password complexity
281 * rules during pam_chauthtok() if the real uid of the calling process
282 * is 0, on the assumption that it's being called by "passwd" run by root.
283 * This wraps pam_chauthtok and sets/restore the real uid so PAM will do
284 * the right thing.
285 */
286 #ifdef SSHPAM_CHAUTHTOK_NEEDS_RUID
287 static int
sshpam_chauthtok_ruid(pam_handle_t * pamh,int flags)288 sshpam_chauthtok_ruid(pam_handle_t *pamh, int flags)
289 {
290 int result;
291
292 if (sshpam_authctxt == NULL)
293 fatal("PAM: sshpam_authctxt not initialized");
294 if (setreuid(sshpam_authctxt->pw->pw_uid, -1) == -1)
295 fatal("%s: setreuid failed: %s", __func__, strerror(errno));
296 result = pam_chauthtok(pamh, flags);
297 if (setreuid(0, -1) == -1)
298 fatal("%s: setreuid failed: %s", __func__, strerror(errno));
299 return result;
300 }
301 # define pam_chauthtok(a,b) (sshpam_chauthtok_ruid((a), (b)))
302 #endif
303
304 static void
sshpam_password_change_required(int reqd)305 sshpam_password_change_required(int reqd)
306 {
307 extern struct sshauthopt *auth_opts;
308 static int saved_port, saved_agent, saved_x11;
309
310 debug3("%s %d", __func__, reqd);
311 if (sshpam_authctxt == NULL)
312 fatal("%s: PAM authctxt not initialized", __func__);
313 sshpam_authctxt->force_pwchange = reqd;
314 if (reqd) {
315 saved_port = auth_opts->permit_port_forwarding_flag;
316 saved_agent = auth_opts->permit_agent_forwarding_flag;
317 saved_x11 = auth_opts->permit_x11_forwarding_flag;
318 auth_opts->permit_port_forwarding_flag = 0;
319 auth_opts->permit_agent_forwarding_flag = 0;
320 auth_opts->permit_x11_forwarding_flag = 0;
321 } else {
322 if (saved_port)
323 auth_opts->permit_port_forwarding_flag = saved_port;
324 if (saved_agent)
325 auth_opts->permit_agent_forwarding_flag = saved_agent;
326 if (saved_x11)
327 auth_opts->permit_x11_forwarding_flag = saved_x11;
328 }
329 }
330
331 /* Import regular and PAM environment from subprocess */
332 static void
import_environments(struct sshbuf * b)333 import_environments(struct sshbuf *b)
334 {
335 char *env;
336 u_int n, i, num_env;
337 int r;
338
339 debug3("PAM: %s entering", __func__);
340
341 #ifndef UNSUPPORTED_POSIX_THREADS_HACK
342 /* Import variables set by do_pam_account */
343 if ((r = sshbuf_get_u32(b, &n)) != 0)
344 fatal("%s: buffer error: %s", __func__, ssh_err(r));
345 if (n > INT_MAX)
346 fatal("%s: invalid PAM account status %u", __func__, n);
347 sshpam_account_status = (int)n;
348 if ((r = sshbuf_get_u32(b, &n)) != 0)
349 fatal("%s: buffer error: %s", __func__, ssh_err(r));
350 sshpam_password_change_required(n != 0);
351
352 /* Import environment from subprocess */
353 if ((r = sshbuf_get_u32(b, &num_env)) != 0)
354 fatal("%s: buffer error: %s", __func__, ssh_err(r));
355 if (num_env > 1024) {
356 fatal_f("received %u environment variables, expected <= 1024",
357 num_env);
358 }
359 sshpam_env = xcalloc(num_env + 1, sizeof(*sshpam_env));
360 debug3("PAM: num env strings %u", num_env);
361 for(i = 0; i < num_env; i++) {
362 if ((r = sshbuf_get_cstring(b, &(sshpam_env[i]), NULL)) != 0)
363 fatal("%s: buffer error: %s", __func__, ssh_err(r));
364 }
365 sshpam_env[num_env] = NULL;
366
367 /* Import PAM environment from subprocess */
368 if ((r = sshbuf_get_u32(b, &num_env)) != 0)
369 fatal("%s: buffer error: %s", __func__, ssh_err(r));
370 if (num_env > 1024) {
371 fatal_f("received %u PAM env variables, expected <= 1024",
372 num_env);
373 }
374 debug("PAM: num PAM env strings %u", num_env);
375 for (i = 0; i < num_env; i++) {
376 if ((r = sshbuf_get_cstring(b, &env, NULL)) != 0)
377 fatal("%s: buffer error: %s", __func__, ssh_err(r));
378 /* Errors are not fatal here */
379 if ((r = pam_putenv(sshpam_handle, env)) != PAM_SUCCESS) {
380 error("PAM: pam_putenv: %s",
381 pam_strerror(sshpam_handle, r));
382 }
383 /*
384 * XXX this possibly leaks env because it is not documented
385 * what pam_putenv() does with it. Does it copy it? Does it
386 * take ownweship? We don't know, so it's safest just to leak.
387 */
388 }
389 #endif
390 }
391
392 /*
393 * Conversation function for authentication thread.
394 */
395 static int
sshpam_thread_conv(int n,sshpam_const struct pam_message ** msg,struct pam_response ** resp,void * data)396 sshpam_thread_conv(int n, sshpam_const struct pam_message **msg,
397 struct pam_response **resp, void *data)
398 {
399 struct sshbuf *buffer;
400 struct pam_ctxt *ctxt;
401 struct pam_response *reply;
402 int r, i;
403 u_char status;
404
405 debug3("PAM: %s entering, %d messages", __func__, n);
406 *resp = NULL;
407
408 if (data == NULL) {
409 error("PAM: conversation function passed a null context");
410 return (PAM_CONV_ERR);
411 }
412 ctxt = data;
413 if (n <= 0 || n > PAM_MAX_NUM_MSG)
414 return (PAM_CONV_ERR);
415
416 if ((reply = calloc(n, sizeof(*reply))) == NULL)
417 return PAM_CONV_ERR;
418 if ((buffer = sshbuf_new()) == NULL) {
419 free(reply);
420 return PAM_CONV_ERR;
421 }
422
423 for (i = 0; i < n; ++i) {
424 switch (PAM_MSG_MEMBER(msg, i, msg_style)) {
425 case PAM_PROMPT_ECHO_OFF:
426 case PAM_PROMPT_ECHO_ON:
427 if ((r = sshbuf_put_cstring(buffer,
428 PAM_MSG_MEMBER(msg, i, msg))) != 0)
429 fatal("%s: buffer error: %s",
430 __func__, ssh_err(r));
431 if (ssh_msg_send(ctxt->pam_csock,
432 PAM_MSG_MEMBER(msg, i, msg_style), buffer) == -1)
433 goto fail;
434
435 if (ssh_msg_recv(ctxt->pam_csock, buffer) == -1)
436 goto fail;
437 if ((r = sshbuf_get_u8(buffer, &status)) != 0)
438 fatal("%s: buffer error: %s",
439 __func__, ssh_err(r));
440 if (status != PAM_AUTHTOK)
441 goto fail;
442 if ((r = sshbuf_get_cstring(buffer,
443 &reply[i].resp, NULL)) != 0)
444 fatal("%s: buffer error: %s",
445 __func__, ssh_err(r));
446 break;
447 case PAM_ERROR_MSG:
448 case PAM_TEXT_INFO:
449 if ((r = sshbuf_put_cstring(buffer,
450 PAM_MSG_MEMBER(msg, i, msg))) != 0)
451 fatal("%s: buffer error: %s",
452 __func__, ssh_err(r));
453 if (ssh_msg_send(ctxt->pam_csock,
454 PAM_MSG_MEMBER(msg, i, msg_style), buffer) == -1)
455 goto fail;
456 break;
457 default:
458 goto fail;
459 }
460 sshbuf_reset(buffer);
461 }
462 sshbuf_free(buffer);
463 *resp = reply;
464 return (PAM_SUCCESS);
465
466 fail:
467 for(i = 0; i < n; i++) {
468 free(reply[i].resp);
469 }
470 free(reply);
471 sshbuf_free(buffer);
472 return (PAM_CONV_ERR);
473 }
474
475 /*
476 * Authentication thread.
477 */
478 static void *
sshpam_thread(void * ctxtp)479 sshpam_thread(void *ctxtp)
480 {
481 struct pam_ctxt *ctxt = ctxtp;
482 struct sshbuf *buffer = NULL;
483 struct pam_conv sshpam_conv;
484 int r, flags = (options.permit_empty_passwd == 0 ?
485 PAM_DISALLOW_NULL_AUTHTOK : 0);
486 #ifndef UNSUPPORTED_POSIX_THREADS_HACK
487 extern char **environ;
488 char **env_from_pam;
489 u_int i;
490 const char *pam_user;
491 const char **ptr_pam_user = &pam_user;
492 char *tz = getenv("TZ");
493
494 sshpam_err = pam_get_item(sshpam_handle, PAM_USER,
495 (sshpam_const void **)ptr_pam_user);
496 if (sshpam_err != PAM_SUCCESS)
497 goto auth_fail;
498
499 environ[0] = NULL;
500 if (tz != NULL)
501 if (setenv("TZ", tz, 1) == -1)
502 error("PAM: could not set TZ environment: %s",
503 strerror(errno));
504
505 if (sshpam_authctxt != NULL) {
506 setproctitle("%s [pam]",
507 sshpam_authctxt->valid ? pam_user : "unknown");
508 }
509 #endif
510
511 sshpam_conv.conv = sshpam_thread_conv;
512 sshpam_conv.appdata_ptr = ctxt;
513
514 if (sshpam_authctxt == NULL)
515 fatal("%s: PAM authctxt not initialized", __func__);
516
517 if ((buffer = sshbuf_new()) == NULL)
518 fatal("%s: sshbuf_new failed", __func__);
519
520 sshpam_err = pam_set_item(sshpam_handle, PAM_CONV,
521 (const void *)&sshpam_conv);
522 if (sshpam_err != PAM_SUCCESS)
523 goto auth_fail;
524 sshpam_err = pam_authenticate(sshpam_handle, flags);
525 if (sshpam_err == PAM_MAXTRIES)
526 sshpam_set_maxtries_reached(1);
527 if (sshpam_err != PAM_SUCCESS)
528 goto auth_fail;
529
530 if (!do_pam_account()) {
531 sshpam_err = PAM_ACCT_EXPIRED;
532 goto auth_fail;
533 }
534 if (sshpam_authctxt->force_pwchange) {
535 sshpam_err = pam_chauthtok(sshpam_handle,
536 PAM_CHANGE_EXPIRED_AUTHTOK);
537 if (sshpam_err != PAM_SUCCESS)
538 goto auth_fail;
539 sshpam_password_change_required(0);
540 }
541
542 if ((r = sshbuf_put_cstring(buffer, "OK")) != 0)
543 fatal("%s: buffer error: %s", __func__, ssh_err(r));
544
545 #ifndef UNSUPPORTED_POSIX_THREADS_HACK
546 /* Export variables set by do_pam_account */
547 if ((r = sshbuf_put_u32(buffer, sshpam_account_status)) != 0 ||
548 (r = sshbuf_put_u32(buffer, sshpam_authctxt->force_pwchange)) != 0)
549 fatal("%s: buffer error: %s", __func__, ssh_err(r));
550
551 /* Export any environment strings set in child */
552 for (i = 0; environ[i] != NULL; i++) {
553 /* Count */
554 if (i > INT_MAX)
555 fatal("%s: too many environment strings", __func__);
556 }
557 if ((r = sshbuf_put_u32(buffer, i)) != 0)
558 fatal("%s: buffer error: %s", __func__, ssh_err(r));
559 for (i = 0; environ[i] != NULL; i++) {
560 if ((r = sshbuf_put_cstring(buffer, environ[i])) != 0)
561 fatal("%s: buffer error: %s", __func__, ssh_err(r));
562 }
563 /* Export any environment strings set by PAM in child */
564 env_from_pam = pam_getenvlist(sshpam_handle);
565 for (i = 0; env_from_pam != NULL && env_from_pam[i] != NULL; i++) {
566 /* Count */
567 if (i > INT_MAX)
568 fatal("%s: too many PAM environment strings", __func__);
569 }
570 if ((r = sshbuf_put_u32(buffer, i)) != 0)
571 fatal("%s: buffer error: %s", __func__, ssh_err(r));
572 for (i = 0; env_from_pam != NULL && env_from_pam[i] != NULL; i++) {
573 if ((r = sshbuf_put_cstring(buffer, env_from_pam[i])) != 0)
574 fatal("%s: buffer error: %s", __func__, ssh_err(r));
575 }
576 #endif /* UNSUPPORTED_POSIX_THREADS_HACK */
577
578 /* XXX - can't do much about an error here */
579 ssh_msg_send(ctxt->pam_csock, sshpam_err, buffer);
580 sshbuf_free(buffer);
581 pthread_exit(NULL);
582
583 auth_fail:
584 if ((r = sshbuf_put_cstring(buffer,
585 pam_strerror(sshpam_handle, sshpam_err))) != 0)
586 fatal("%s: buffer error: %s", __func__, ssh_err(r));
587 /* XXX - can't do much about an error here */
588 if (sshpam_err == PAM_ACCT_EXPIRED)
589 ssh_msg_send(ctxt->pam_csock, PAM_ACCT_EXPIRED, buffer);
590 else if (sshpam_maxtries_reached)
591 ssh_msg_send(ctxt->pam_csock, PAM_MAXTRIES, buffer);
592 else
593 ssh_msg_send(ctxt->pam_csock, PAM_AUTH_ERR, buffer);
594 sshbuf_free(buffer);
595 pthread_exit(NULL);
596
597 return (NULL); /* Avoid warning for non-pthread case */
598 }
599
600 void
sshpam_thread_cleanup(void)601 sshpam_thread_cleanup(void)
602 {
603 struct pam_ctxt *ctxt = cleanup_ctxt;
604
605 debug3("PAM: %s entering", __func__);
606 if (ctxt != NULL && ctxt->pam_thread != 0) {
607 pthread_cancel(ctxt->pam_thread);
608 pthread_join(ctxt->pam_thread, NULL);
609 close(ctxt->pam_psock);
610 close(ctxt->pam_csock);
611 memset(ctxt, 0, sizeof(*ctxt));
612 cleanup_ctxt = NULL;
613 }
614 }
615
616 static int
sshpam_null_conv(int n,sshpam_const struct pam_message ** msg,struct pam_response ** resp,void * data)617 sshpam_null_conv(int n, sshpam_const struct pam_message **msg,
618 struct pam_response **resp, void *data)
619 {
620 debug3("PAM: %s entering, %d messages", __func__, n);
621 return (PAM_CONV_ERR);
622 }
623
624 static struct pam_conv null_conv = { sshpam_null_conv, NULL };
625
626 static int
sshpam_store_conv(int n,sshpam_const struct pam_message ** msg,struct pam_response ** resp,void * data)627 sshpam_store_conv(int n, sshpam_const struct pam_message **msg,
628 struct pam_response **resp, void *data)
629 {
630 struct pam_response *reply;
631 int r, i;
632
633 debug3("PAM: %s called with %d messages", __func__, n);
634 *resp = NULL;
635
636 if (n <= 0 || n > PAM_MAX_NUM_MSG)
637 return (PAM_CONV_ERR);
638
639 if ((reply = calloc(n, sizeof(*reply))) == NULL)
640 return (PAM_CONV_ERR);
641
642 for (i = 0; i < n; ++i) {
643 switch (PAM_MSG_MEMBER(msg, i, msg_style)) {
644 case PAM_ERROR_MSG:
645 case PAM_TEXT_INFO:
646 if ((r = sshbuf_putf(loginmsg, "%s\n",
647 PAM_MSG_MEMBER(msg, i, msg))) != 0)
648 fatal("%s: buffer error: %s",
649 __func__, ssh_err(r));
650 reply[i].resp_retcode = PAM_SUCCESS;
651 break;
652 default:
653 goto fail;
654 }
655 }
656 *resp = reply;
657 return (PAM_SUCCESS);
658
659 fail:
660 for(i = 0; i < n; i++) {
661 free(reply[i].resp);
662 }
663 free(reply);
664 return (PAM_CONV_ERR);
665 }
666
667 static struct pam_conv store_conv = { sshpam_store_conv, NULL };
668
669 void
sshpam_cleanup(void)670 sshpam_cleanup(void)
671 {
672 if (sshpam_handle == NULL || (use_privsep && !mm_is_monitor()))
673 return;
674 debug("PAM: cleanup");
675 pam_set_item(sshpam_handle, PAM_CONV, (const void *)&null_conv);
676 if (sshpam_session_open) {
677 debug("PAM: closing session");
678 pam_close_session(sshpam_handle, PAM_SILENT);
679 sshpam_session_open = 0;
680 }
681 if (sshpam_cred_established) {
682 debug("PAM: deleting credentials");
683 pam_setcred(sshpam_handle, PAM_DELETE_CRED);
684 sshpam_cred_established = 0;
685 }
686 sshpam_authenticated = 0;
687 pam_end(sshpam_handle, sshpam_err);
688 sshpam_handle = NULL;
689 }
690
691 static int
sshpam_init(struct ssh * ssh,Authctxt * authctxt)692 sshpam_init(struct ssh *ssh, Authctxt *authctxt)
693 {
694 const char *pam_user, *user = authctxt->user;
695 const char **ptr_pam_user = &pam_user;
696 int r;
697
698 #if defined(PAM_SUN_CODEBASE) && defined(PAM_MAX_RESP_SIZE)
699 /* Protect buggy PAM implementations from excessively long usernames */
700 if (strlen(user) >= PAM_MAX_RESP_SIZE)
701 fatal("Username too long from %s port %d",
702 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh));
703 #endif
704 if (sshpam_handle == NULL) {
705 if (ssh == NULL) {
706 fatal("%s: called initially with no "
707 "packet context", __func__);
708 }
709 } if (sshpam_handle != NULL) {
710 /* We already have a PAM context; check if the user matches */
711 sshpam_err = pam_get_item(sshpam_handle,
712 PAM_USER, (sshpam_const void **)ptr_pam_user);
713 if (sshpam_err == PAM_SUCCESS && strcmp(user, pam_user) == 0)
714 return (0);
715 pam_end(sshpam_handle, sshpam_err);
716 sshpam_handle = NULL;
717 }
718 debug("PAM: initializing for \"%s\"", user);
719 sshpam_err =
720 pam_start(SSHD_PAM_SERVICE, user, &store_conv, &sshpam_handle);
721 sshpam_authctxt = authctxt;
722
723 if (sshpam_err != PAM_SUCCESS) {
724 pam_end(sshpam_handle, sshpam_err);
725 sshpam_handle = NULL;
726 return (-1);
727 }
728
729 if (ssh != NULL && sshpam_rhost == NULL) {
730 /*
731 * We need to cache these as we don't have packet context
732 * during the kbdint flow.
733 */
734 sshpam_rhost = xstrdup(auth_get_canonical_hostname(ssh,
735 options.use_dns));
736 sshpam_laddr = get_local_ipaddr(
737 ssh_packet_get_connection_in(ssh));
738 }
739 if (sshpam_rhost != NULL) {
740 debug("PAM: setting PAM_RHOST to \"%s\"", sshpam_rhost);
741 sshpam_err = pam_set_item(sshpam_handle, PAM_RHOST,
742 sshpam_rhost);
743 if (sshpam_err != PAM_SUCCESS) {
744 pam_end(sshpam_handle, sshpam_err);
745 sshpam_handle = NULL;
746 return (-1);
747 }
748 }
749 if (ssh != NULL && sshpam_laddr != NULL) {
750 char *conninfo;
751
752 /* Put SSH_CONNECTION in the PAM environment too */
753 xasprintf(&conninfo, "SSH_CONNECTION=%.50s %d %.50s %d",
754 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh),
755 sshpam_laddr, ssh_local_port(ssh));
756 if ((r = pam_putenv(sshpam_handle, conninfo)) != PAM_SUCCESS)
757 logit("pam_putenv: %s", pam_strerror(sshpam_handle, r));
758 free(conninfo);
759 }
760
761 #ifdef PAM_TTY_KLUDGE
762 /*
763 * Some silly PAM modules (e.g. pam_time) require a TTY to operate.
764 * sshd doesn't set the tty until too late in the auth process and
765 * may not even set one (for tty-less connections)
766 */
767 debug("PAM: setting PAM_TTY to \"ssh\"");
768 sshpam_err = pam_set_item(sshpam_handle, PAM_TTY, "ssh");
769 if (sshpam_err != PAM_SUCCESS) {
770 pam_end(sshpam_handle, sshpam_err);
771 sshpam_handle = NULL;
772 return (-1);
773 }
774 #endif
775 return (0);
776 }
777
778 static void
expose_authinfo(const char * caller)779 expose_authinfo(const char *caller)
780 {
781 char *auth_info;
782
783 /*
784 * Expose authentication information to PAM.
785 * The environment variable is versioned. Please increment the
786 * version suffix if the format of session_info changes.
787 */
788 if (sshpam_authctxt->session_info == NULL)
789 auth_info = xstrdup("");
790 else if ((auth_info = sshbuf_dup_string(
791 sshpam_authctxt->session_info)) == NULL)
792 fatal("%s: sshbuf_dup_string failed", __func__);
793
794 debug2("%s: auth information in SSH_AUTH_INFO_0", caller);
795 do_pam_putenv("SSH_AUTH_INFO_0", auth_info);
796 free(auth_info);
797 }
798
799 static void *
sshpam_init_ctx(Authctxt * authctxt)800 sshpam_init_ctx(Authctxt *authctxt)
801 {
802 struct pam_ctxt *ctxt;
803 int result, socks[2];
804
805 debug3("PAM: %s entering", __func__);
806 /*
807 * Refuse to start if we don't have PAM enabled or do_pam_account
808 * has previously failed.
809 */
810 if (!options.use_pam || sshpam_account_status == 0)
811 return NULL;
812
813 /* Initialize PAM */
814 if (sshpam_init(NULL, authctxt) == -1) {
815 error("PAM: initialization failed");
816 return (NULL);
817 }
818
819 expose_authinfo(__func__);
820 ctxt = xcalloc(1, sizeof *ctxt);
821
822 /* Start the authentication thread */
823 if (socketpair(AF_UNIX, SOCK_STREAM, PF_UNSPEC, socks) == -1) {
824 error("PAM: failed create sockets: %s", strerror(errno));
825 free(ctxt);
826 return (NULL);
827 }
828 ctxt->pam_psock = socks[0];
829 ctxt->pam_csock = socks[1];
830 result = pthread_create(&ctxt->pam_thread, NULL, sshpam_thread, ctxt);
831 if (result != 0) {
832 error("PAM: failed to start authentication thread: %s",
833 strerror(result));
834 close(socks[0]);
835 close(socks[1]);
836 free(ctxt);
837 return (NULL);
838 }
839 cleanup_ctxt = ctxt;
840 return (ctxt);
841 }
842
843 static int
sshpam_query(void * ctx,char ** name,char ** info,u_int * num,char *** prompts,u_int ** echo_on)844 sshpam_query(void *ctx, char **name, char **info,
845 u_int *num, char ***prompts, u_int **echo_on)
846 {
847 struct sshbuf *buffer;
848 struct pam_ctxt *ctxt = ctx;
849 size_t plen;
850 u_char type;
851 char *msg;
852 size_t len, mlen, nmesg = 0;
853 int r;
854
855 debug3("PAM: %s entering", __func__);
856 if ((buffer = sshbuf_new()) == NULL)
857 fatal("%s: sshbuf_new failed", __func__);
858 *name = xstrdup("");
859 *info = xstrdup("");
860 *prompts = xmalloc(sizeof(char *));
861 **prompts = NULL;
862 plen = 0;
863 *echo_on = xmalloc(sizeof(u_int));
864 while (ssh_msg_recv(ctxt->pam_psock, buffer) == 0) {
865 if (++nmesg > PAM_MAX_NUM_MSG)
866 fatal_f("too many query messages");
867 if ((r = sshbuf_get_u8(buffer, &type)) != 0 ||
868 (r = sshbuf_get_cstring(buffer, &msg, &mlen)) != 0)
869 fatal("%s: buffer error: %s", __func__, ssh_err(r));
870 switch (type) {
871 case PAM_PROMPT_ECHO_ON:
872 case PAM_PROMPT_ECHO_OFF:
873 *num = 1;
874 len = plen + mlen + 1;
875 **prompts = xreallocarray(**prompts, 1, len);
876 strlcpy(**prompts + plen, msg, len - plen);
877 plen += mlen;
878 **echo_on = (type == PAM_PROMPT_ECHO_ON);
879 free(msg);
880 sshbuf_free(buffer);
881 return (0);
882 case PAM_ERROR_MSG:
883 case PAM_TEXT_INFO:
884 /* accumulate messages */
885 len = plen + mlen + 2;
886 **prompts = xreallocarray(**prompts, 1, len);
887 strlcpy(**prompts + plen, msg, len - plen);
888 plen += mlen;
889 strlcat(**prompts + plen, "\n", len - plen);
890 plen++;
891 free(msg);
892 break;
893 case PAM_ACCT_EXPIRED:
894 case PAM_MAXTRIES:
895 if (type == PAM_ACCT_EXPIRED)
896 sshpam_account_status = 0;
897 if (type == PAM_MAXTRIES)
898 sshpam_set_maxtries_reached(1);
899 /* FALLTHROUGH */
900 case PAM_AUTH_ERR:
901 debug3("PAM: %s", pam_strerror(sshpam_handle, type));
902 if (**prompts != NULL && strlen(**prompts) != 0) {
903 free(*info);
904 *info = **prompts;
905 **prompts = NULL;
906 *num = 0;
907 **echo_on = 0;
908 ctxt->pam_done = -1;
909 free(msg);
910 sshbuf_free(buffer);
911 return 0;
912 }
913 /* FALLTHROUGH */
914 case PAM_SUCCESS:
915 if (**prompts != NULL) {
916 /* drain any accumulated messages */
917 debug("PAM: %s", **prompts);
918 if ((r = sshbuf_put(loginmsg, **prompts,
919 strlen(**prompts))) != 0)
920 fatal("%s: buffer error: %s",
921 __func__, ssh_err(r));
922 free(**prompts);
923 **prompts = NULL;
924 }
925 if (type == PAM_SUCCESS) {
926 if (!sshpam_authctxt->valid ||
927 (sshpam_authctxt->pw->pw_uid == 0 &&
928 options.permit_root_login != PERMIT_YES))
929 fatal("Internal error: PAM auth "
930 "succeeded when it should have "
931 "failed");
932 import_environments(buffer);
933 *num = 0;
934 **echo_on = 0;
935 ctxt->pam_done = 1;
936 free(msg);
937 sshbuf_free(buffer);
938 return (0);
939 }
940 BLACKLIST_NOTIFY(NULL, BLACKLIST_BAD_USER,
941 sshpam_authctxt->user);
942 error("PAM: %s for %s%.100s from %.100s", msg,
943 sshpam_authctxt->valid ? "" : "illegal user ",
944 sshpam_authctxt->user, sshpam_rhost);
945 /* FALLTHROUGH */
946 default:
947 *num = 0;
948 **echo_on = 0;
949 free(msg);
950 ctxt->pam_done = -1;
951 sshbuf_free(buffer);
952 return (-1);
953 }
954 }
955 sshbuf_free(buffer);
956 return (-1);
957 }
958
959 /*
960 * Returns a junk password of identical length to that the user supplied.
961 * Used to mitigate timing attacks against crypt(3)/PAM stacks that
962 * vary processing time in proportion to password length.
963 */
964 static char *
fake_password(const char * wire_password)965 fake_password(const char *wire_password)
966 {
967 const char junk[] = "\b\n\r\177INCORRECT";
968 char *ret = NULL;
969 size_t i, l = wire_password != NULL ? strlen(wire_password) : 0;
970
971 if (l >= INT_MAX)
972 fatal("%s: password length too long: %zu", __func__, l);
973
974 ret = malloc(l + 1);
975 if (ret == NULL)
976 return NULL;
977 for (i = 0; i < l; i++)
978 ret[i] = junk[i % (sizeof(junk) - 1)];
979 ret[i] = '\0';
980 return ret;
981 }
982
983 /* XXX - see also comment in auth-chall.c:verify_response */
984 static int
sshpam_respond(void * ctx,u_int num,char ** resp)985 sshpam_respond(void *ctx, u_int num, char **resp)
986 {
987 struct sshbuf *buffer;
988 struct pam_ctxt *ctxt = ctx;
989 char *fake;
990 int r;
991
992 debug2("PAM: %s entering, %u responses", __func__, num);
993 switch (ctxt->pam_done) {
994 case 1:
995 sshpam_authenticated = 1;
996 return (0);
997 case 0:
998 break;
999 default:
1000 return (-1);
1001 }
1002 if (num != 1) {
1003 error("PAM: expected one response, got %u", num);
1004 return (-1);
1005 }
1006 if ((buffer = sshbuf_new()) == NULL)
1007 fatal("%s: sshbuf_new failed", __func__);
1008 if (sshpam_authctxt->valid &&
1009 (sshpam_authctxt->pw->pw_uid != 0 ||
1010 options.permit_root_login == PERMIT_YES)) {
1011 if ((r = sshbuf_put_cstring(buffer, *resp)) != 0)
1012 fatal("%s: buffer error: %s", __func__, ssh_err(r));
1013 } else {
1014 fake = fake_password(*resp);
1015 if ((r = sshbuf_put_cstring(buffer, fake)) != 0)
1016 fatal("%s: buffer error: %s", __func__, ssh_err(r));
1017 free(fake);
1018 }
1019 if (ssh_msg_send(ctxt->pam_psock, PAM_AUTHTOK, buffer) == -1) {
1020 sshbuf_free(buffer);
1021 return (-1);
1022 }
1023 sshbuf_free(buffer);
1024 return (1);
1025 }
1026
1027 static void
sshpam_free_ctx(void * ctxtp)1028 sshpam_free_ctx(void *ctxtp)
1029 {
1030 struct pam_ctxt *ctxt = ctxtp;
1031
1032 debug3("PAM: %s entering", __func__);
1033 sshpam_thread_cleanup();
1034 free(ctxt);
1035 /*
1036 * We don't call sshpam_cleanup() here because we may need the PAM
1037 * handle at a later stage, e.g. when setting up a session. It's
1038 * still on the cleanup list, so pam_end() *will* be called before
1039 * the server process terminates.
1040 */
1041 }
1042
1043 KbdintDevice sshpam_device = {
1044 "pam",
1045 sshpam_init_ctx,
1046 sshpam_query,
1047 sshpam_respond,
1048 sshpam_free_ctx
1049 };
1050
1051 KbdintDevice mm_sshpam_device = {
1052 "pam",
1053 mm_sshpam_init_ctx,
1054 mm_sshpam_query,
1055 mm_sshpam_respond,
1056 mm_sshpam_free_ctx
1057 };
1058
1059 /*
1060 * This replaces auth-pam.c
1061 */
1062 void
start_pam(struct ssh * ssh)1063 start_pam(struct ssh *ssh)
1064 {
1065 Authctxt *authctxt = (Authctxt *)ssh->authctxt;
1066
1067 if (!options.use_pam)
1068 fatal("PAM: initialisation requested when UsePAM=no");
1069
1070 if (sshpam_init(ssh, authctxt) == -1)
1071 fatal("PAM: initialisation failed");
1072 }
1073
1074 void
finish_pam(void)1075 finish_pam(void)
1076 {
1077 sshpam_cleanup();
1078 }
1079
1080
1081 u_int
do_pam_account(void)1082 do_pam_account(void)
1083 {
1084 debug("%s: called", __func__);
1085 if (sshpam_account_status != -1)
1086 return (sshpam_account_status);
1087
1088 expose_authinfo(__func__);
1089
1090 sshpam_err = pam_acct_mgmt(sshpam_handle, 0);
1091 debug3("PAM: %s pam_acct_mgmt = %d (%s)", __func__, sshpam_err,
1092 pam_strerror(sshpam_handle, sshpam_err));
1093
1094 if (sshpam_err != PAM_SUCCESS && sshpam_err != PAM_NEW_AUTHTOK_REQD) {
1095 sshpam_account_status = 0;
1096 return (sshpam_account_status);
1097 }
1098
1099 if (sshpam_err == PAM_NEW_AUTHTOK_REQD)
1100 sshpam_password_change_required(1);
1101
1102 sshpam_account_status = 1;
1103 return (sshpam_account_status);
1104 }
1105
1106 void
do_pam_setcred(int init)1107 do_pam_setcred(int init)
1108 {
1109 sshpam_err = pam_set_item(sshpam_handle, PAM_CONV,
1110 (const void *)&store_conv);
1111 if (sshpam_err != PAM_SUCCESS)
1112 fatal("PAM: failed to set PAM_CONV: %s",
1113 pam_strerror(sshpam_handle, sshpam_err));
1114 if (init) {
1115 debug("PAM: establishing credentials");
1116 sshpam_err = pam_setcred(sshpam_handle, PAM_ESTABLISH_CRED);
1117 } else {
1118 debug("PAM: reinitializing credentials");
1119 sshpam_err = pam_setcred(sshpam_handle, PAM_REINITIALIZE_CRED);
1120 }
1121 if (sshpam_err == PAM_SUCCESS) {
1122 sshpam_cred_established = 1;
1123 return;
1124 }
1125 if (sshpam_authenticated)
1126 fatal("PAM: pam_setcred(): %s",
1127 pam_strerror(sshpam_handle, sshpam_err));
1128 else
1129 debug("PAM: pam_setcred(): %s",
1130 pam_strerror(sshpam_handle, sshpam_err));
1131 }
1132
1133 static int
sshpam_tty_conv(int n,sshpam_const struct pam_message ** msg,struct pam_response ** resp,void * data)1134 sshpam_tty_conv(int n, sshpam_const struct pam_message **msg,
1135 struct pam_response **resp, void *data)
1136 {
1137 char input[PAM_MAX_MSG_SIZE];
1138 struct pam_response *reply;
1139 int i;
1140
1141 debug3("PAM: %s called with %d messages", __func__, n);
1142
1143 *resp = NULL;
1144
1145 if (n <= 0 || n > PAM_MAX_NUM_MSG || !isatty(STDIN_FILENO))
1146 return (PAM_CONV_ERR);
1147
1148 if ((reply = calloc(n, sizeof(*reply))) == NULL)
1149 return (PAM_CONV_ERR);
1150
1151 for (i = 0; i < n; ++i) {
1152 switch (PAM_MSG_MEMBER(msg, i, msg_style)) {
1153 case PAM_PROMPT_ECHO_OFF:
1154 reply[i].resp =
1155 read_passphrase(PAM_MSG_MEMBER(msg, i, msg),
1156 RP_ALLOW_STDIN);
1157 reply[i].resp_retcode = PAM_SUCCESS;
1158 break;
1159 case PAM_PROMPT_ECHO_ON:
1160 fprintf(stderr, "%s\n", PAM_MSG_MEMBER(msg, i, msg));
1161 if (fgets(input, sizeof input, stdin) == NULL)
1162 input[0] = '\0';
1163 if ((reply[i].resp = strdup(input)) == NULL)
1164 goto fail;
1165 reply[i].resp_retcode = PAM_SUCCESS;
1166 break;
1167 case PAM_ERROR_MSG:
1168 case PAM_TEXT_INFO:
1169 fprintf(stderr, "%s\n", PAM_MSG_MEMBER(msg, i, msg));
1170 reply[i].resp_retcode = PAM_SUCCESS;
1171 break;
1172 default:
1173 goto fail;
1174 }
1175 }
1176 *resp = reply;
1177 return (PAM_SUCCESS);
1178
1179 fail:
1180 for(i = 0; i < n; i++) {
1181 free(reply[i].resp);
1182 }
1183 free(reply);
1184 return (PAM_CONV_ERR);
1185 }
1186
1187 static struct pam_conv tty_conv = { sshpam_tty_conv, NULL };
1188
1189 /*
1190 * XXX this should be done in the authentication phase, but ssh1 doesn't
1191 * support that
1192 */
1193 void
do_pam_chauthtok(void)1194 do_pam_chauthtok(void)
1195 {
1196 if (use_privsep)
1197 fatal("Password expired (unable to change with privsep)");
1198 sshpam_err = pam_set_item(sshpam_handle, PAM_CONV,
1199 (const void *)&tty_conv);
1200 if (sshpam_err != PAM_SUCCESS)
1201 fatal("PAM: failed to set PAM_CONV: %s",
1202 pam_strerror(sshpam_handle, sshpam_err));
1203 debug("PAM: changing password");
1204 sshpam_err = pam_chauthtok(sshpam_handle, PAM_CHANGE_EXPIRED_AUTHTOK);
1205 if (sshpam_err != PAM_SUCCESS)
1206 fatal("PAM: pam_chauthtok(): %s",
1207 pam_strerror(sshpam_handle, sshpam_err));
1208 }
1209
1210 void
do_pam_session(struct ssh * ssh)1211 do_pam_session(struct ssh *ssh)
1212 {
1213 debug3("PAM: opening session");
1214
1215 expose_authinfo(__func__);
1216
1217 sshpam_err = pam_set_item(sshpam_handle, PAM_CONV,
1218 (const void *)&store_conv);
1219 if (sshpam_err != PAM_SUCCESS)
1220 fatal("PAM: failed to set PAM_CONV: %s",
1221 pam_strerror(sshpam_handle, sshpam_err));
1222 sshpam_err = pam_open_session(sshpam_handle, 0);
1223 if (sshpam_err == PAM_SUCCESS)
1224 sshpam_session_open = 1;
1225 else {
1226 sshpam_session_open = 0;
1227 auth_restrict_session(ssh);
1228 error("PAM: pam_open_session(): %s",
1229 pam_strerror(sshpam_handle, sshpam_err));
1230 }
1231
1232 }
1233
1234 int
is_pam_session_open(void)1235 is_pam_session_open(void)
1236 {
1237 return sshpam_session_open;
1238 }
1239
1240 /*
1241 * Set a PAM environment string. We need to do this so that the session
1242 * modules can handle things like Kerberos/GSI credentials that appear
1243 * during the ssh authentication process.
1244 */
1245 int
do_pam_putenv(char * name,char * value)1246 do_pam_putenv(char *name, char *value)
1247 {
1248 int ret = 1;
1249 char *compound;
1250 size_t len;
1251
1252 len = strlen(name) + strlen(value) + 2;
1253 compound = xmalloc(len);
1254
1255 snprintf(compound, len, "%s=%s", name, value);
1256 ret = pam_putenv(sshpam_handle, compound);
1257 free(compound);
1258
1259 return (ret);
1260 }
1261
1262 char **
fetch_pam_child_environment(void)1263 fetch_pam_child_environment(void)
1264 {
1265 return sshpam_env;
1266 }
1267
1268 char **
fetch_pam_environment(void)1269 fetch_pam_environment(void)
1270 {
1271 return (pam_getenvlist(sshpam_handle));
1272 }
1273
1274 void
free_pam_environment(char ** env)1275 free_pam_environment(char **env)
1276 {
1277 char **envp;
1278
1279 if (env == NULL)
1280 return;
1281
1282 for (envp = env; *envp; envp++)
1283 free(*envp);
1284 free(env);
1285 }
1286
1287 /*
1288 * "Blind" conversation function for password authentication. Assumes that
1289 * echo-off prompts are for the password and stores messages for later
1290 * display.
1291 */
1292 static int
sshpam_passwd_conv(int n,sshpam_const struct pam_message ** msg,struct pam_response ** resp,void * data)1293 sshpam_passwd_conv(int n, sshpam_const struct pam_message **msg,
1294 struct pam_response **resp, void *data)
1295 {
1296 struct pam_response *reply;
1297 int r, i;
1298 size_t len;
1299
1300 debug3("PAM: %s called with %d messages", __func__, n);
1301
1302 *resp = NULL;
1303
1304 if (n <= 0 || n > PAM_MAX_NUM_MSG)
1305 return (PAM_CONV_ERR);
1306
1307 if ((reply = calloc(n, sizeof(*reply))) == NULL)
1308 return (PAM_CONV_ERR);
1309
1310 for (i = 0; i < n; ++i) {
1311 switch (PAM_MSG_MEMBER(msg, i, msg_style)) {
1312 case PAM_PROMPT_ECHO_OFF:
1313 if (sshpam_password == NULL)
1314 goto fail;
1315 if ((reply[i].resp = strdup(sshpam_password)) == NULL)
1316 goto fail;
1317 reply[i].resp_retcode = PAM_SUCCESS;
1318 break;
1319 case PAM_ERROR_MSG:
1320 case PAM_TEXT_INFO:
1321 len = strlen(PAM_MSG_MEMBER(msg, i, msg));
1322 if (len > 0) {
1323 if ((r = sshbuf_putf(loginmsg, "%s\n",
1324 PAM_MSG_MEMBER(msg, i, msg))) != 0)
1325 fatal("%s: buffer error: %s",
1326 __func__, ssh_err(r));
1327 }
1328 if ((reply[i].resp = strdup("")) == NULL)
1329 goto fail;
1330 reply[i].resp_retcode = PAM_SUCCESS;
1331 break;
1332 default:
1333 goto fail;
1334 }
1335 }
1336 *resp = reply;
1337 return (PAM_SUCCESS);
1338
1339 fail:
1340 for(i = 0; i < n; i++) {
1341 free(reply[i].resp);
1342 }
1343 free(reply);
1344 return (PAM_CONV_ERR);
1345 }
1346
1347 static struct pam_conv passwd_conv = { sshpam_passwd_conv, NULL };
1348
1349 /*
1350 * Attempt password authentication via PAM
1351 */
1352 int
sshpam_auth_passwd(Authctxt * authctxt,const char * password)1353 sshpam_auth_passwd(Authctxt *authctxt, const char *password)
1354 {
1355 int flags = (options.permit_empty_passwd == 0 ?
1356 PAM_DISALLOW_NULL_AUTHTOK : 0);
1357 char *fake = NULL;
1358
1359 if (!options.use_pam || sshpam_handle == NULL)
1360 fatal("PAM: %s called when PAM disabled or failed to "
1361 "initialise.", __func__);
1362
1363 sshpam_password = password;
1364 sshpam_authctxt = authctxt;
1365
1366 /*
1367 * If the user logging in is invalid, or is root but is not permitted
1368 * by PermitRootLogin, use an invalid password to prevent leaking
1369 * information via timing (eg if the PAM config has a delay on fail).
1370 */
1371 if (!authctxt->valid || (authctxt->pw->pw_uid == 0 &&
1372 options.permit_root_login != PERMIT_YES))
1373 sshpam_password = fake = fake_password(password);
1374
1375 sshpam_err = pam_set_item(sshpam_handle, PAM_CONV,
1376 (const void *)&passwd_conv);
1377 if (sshpam_err != PAM_SUCCESS)
1378 fatal("PAM: %s: failed to set PAM_CONV: %s", __func__,
1379 pam_strerror(sshpam_handle, sshpam_err));
1380
1381 sshpam_err = pam_authenticate(sshpam_handle, flags);
1382 sshpam_password = NULL;
1383 free(fake);
1384 if (sshpam_err == PAM_MAXTRIES)
1385 sshpam_set_maxtries_reached(1);
1386 if (sshpam_err == PAM_SUCCESS && authctxt->valid) {
1387 debug("PAM: password authentication accepted for %.100s",
1388 authctxt->user);
1389 return 1;
1390 } else {
1391 debug("PAM: password authentication failed for %.100s: %s",
1392 authctxt->valid ? authctxt->user : "an illegal user",
1393 pam_strerror(sshpam_handle, sshpam_err));
1394 return 0;
1395 }
1396 }
1397
1398 int
sshpam_get_maxtries_reached(void)1399 sshpam_get_maxtries_reached(void)
1400 {
1401 return sshpam_maxtries_reached;
1402 }
1403
1404 void
sshpam_set_maxtries_reached(int reached)1405 sshpam_set_maxtries_reached(int reached)
1406 {
1407 if (reached == 0 || sshpam_maxtries_reached)
1408 return;
1409 sshpam_maxtries_reached = 1;
1410 options.password_authentication = 0;
1411 options.kbd_interactive_authentication = 0;
1412 }
1413 #endif /* USE_PAM */
1414