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- (djm) Add new UsePAM configuration directive to allow runtime control
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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 #include "includes.h"
33 RCSID("$FreeBSD: src/crypto/openssh/auth2-pam-freebsd.c,v 1.11 2003/03/31 13:48:18 des Exp $");
34
35 #ifdef USE_PAM
36 #include <security/pam_appl.h>
37
38 #include "auth.h"
39 #include "auth-pam.h"
40 #include "buffer.h"
41 #include "bufaux.h"
42 #include "canohost.h"
43 #include "log.h"
44 #include "monitor_wrap.h"
45 #include "msg.h"
46 #include "packet.h"
47 #include "readpass.h"
48 #include "servconf.h"
49 #include "ssh2.h"
50 #include "xmalloc.h"
51
52 extern ServerOptions options;
53
54 #define __unused
55
56 #ifdef USE_POSIX_THREADS
57 #include <pthread.h>
58 /*
59  * Avoid namespace clash when *not* using pthreads for systems *with* 
60  * pthreads, which unconditionally define pthread_t via sys/types.h 
61  * (e.g. Linux)
62  */
63 typedef pthread_t sp_pthread_t; 
64 #else
65 /*
66  * Simulate threads with processes.
67  */
68 typedef pid_t sp_pthread_t;
69
70 static void
71 pthread_exit(void *value __unused)
72 {
73         _exit(0);
74 }
75
76 static int
77 pthread_create(sp_pthread_t *thread, const void *attr __unused,
78     void *(*thread_start)(void *), void *arg)
79 {
80         pid_t pid;
81
82         switch ((pid = fork())) {
83         case -1:
84                 error("fork(): %s", strerror(errno));
85                 return (-1);
86         case 0:
87                 thread_start(arg);
88                 _exit(1);
89         default:
90                 *thread = pid;
91                 return (0);
92         }
93 }
94
95 static int
96 pthread_cancel(sp_pthread_t thread)
97 {
98         return (kill(thread, SIGTERM));
99 }
100
101 static int
102 pthread_join(sp_pthread_t thread, void **value __unused)
103 {
104         int status;
105
106         waitpid(thread, &status, 0);
107         return (status);
108 }
109 #endif
110
111
112 static pam_handle_t *sshpam_handle;
113 static int sshpam_err;
114 static int sshpam_authenticated;
115 static int sshpam_new_authtok_reqd;
116 static int sshpam_session_open;
117 static int sshpam_cred_established;
118
119 struct pam_ctxt {
120         sp_pthread_t     pam_thread;
121         int              pam_psock;
122         int              pam_csock;
123         int              pam_done;
124 };
125
126 static void sshpam_free_ctx(void *);
127
128 /*
129  * Conversation function for authentication thread.
130  */
131 static int
132 sshpam_thread_conv(int n,
133          const struct pam_message **msg,
134          struct pam_response **resp,
135          void *data)
136 {
137         Buffer buffer;
138         struct pam_ctxt *ctxt;
139         int i;
140
141         ctxt = data;
142         if (n <= 0 || n > PAM_MAX_NUM_MSG)
143                 return (PAM_CONV_ERR);
144         *resp = xmalloc(n * sizeof **resp);
145         buffer_init(&buffer);
146         for (i = 0; i < n; ++i) {
147                 resp[i]->resp_retcode = 0;
148                 resp[i]->resp = NULL;
149                 switch (PAM_MSG_MEMBER(msg, i, msg_style)) {
150                 case PAM_PROMPT_ECHO_OFF:
151                         buffer_put_cstring(&buffer, PAM_MSG_MEMBER(msg, i, msg));
152                         ssh_msg_send(ctxt->pam_csock, 
153                             PAM_MSG_MEMBER(msg, i, msg_style), &buffer);
154                         ssh_msg_recv(ctxt->pam_csock, &buffer);
155                         if (buffer_get_char(&buffer) != PAM_AUTHTOK)
156                                 goto fail;
157                         resp[i]->resp = buffer_get_string(&buffer, NULL);
158                         break;
159                 case PAM_PROMPT_ECHO_ON:
160                         buffer_put_cstring(&buffer, PAM_MSG_MEMBER(msg, i, msg));
161                         ssh_msg_send(ctxt->pam_csock, 
162                             PAM_MSG_MEMBER(msg, i, msg_style), &buffer);
163                         ssh_msg_recv(ctxt->pam_csock, &buffer);
164                         if (buffer_get_char(&buffer) != PAM_AUTHTOK)
165                                 goto fail;
166                         resp[i]->resp = buffer_get_string(&buffer, NULL);
167                         break;
168                 case PAM_ERROR_MSG:
169                         buffer_put_cstring(&buffer, PAM_MSG_MEMBER(msg, i, msg));
170                         ssh_msg_send(ctxt->pam_csock, 
171                             PAM_MSG_MEMBER(msg, i, msg_style), &buffer);
172                         break;
173                 case PAM_TEXT_INFO:
174                         buffer_put_cstring(&buffer, PAM_MSG_MEMBER(msg, i, msg));
175                         ssh_msg_send(ctxt->pam_csock, 
176                             PAM_MSG_MEMBER(msg, i, msg_style), &buffer);
177                         break;
178                 default:
179                         goto fail;
180                 }
181                 buffer_clear(&buffer);
182         }
183         buffer_free(&buffer);
184         return (PAM_SUCCESS);
185  fail:
186         while (i)
187                 xfree(resp[--i]);
188         xfree(*resp);
189         *resp = NULL;
190         buffer_free(&buffer);
191         return (PAM_CONV_ERR);
192 }
193
194 /*
195  * Authentication thread.
196  */
197 static void *
198 sshpam_thread(void *ctxtp)
199 {
200         struct pam_ctxt *ctxt = ctxtp;
201         Buffer buffer;
202         struct pam_conv sshpam_conv = { sshpam_thread_conv, ctxt };
203 #ifndef USE_POSIX_THREADS
204         const char *pam_user;
205
206         pam_get_item(sshpam_handle, PAM_USER, (const void **)&pam_user);
207         setproctitle("%s [pam]", pam_user);
208 #endif
209
210         buffer_init(&buffer);
211         sshpam_err = pam_set_item(sshpam_handle, PAM_CONV,
212             (const void *)&sshpam_conv);
213         if (sshpam_err != PAM_SUCCESS)
214                 goto auth_fail;
215         sshpam_err = pam_authenticate(sshpam_handle, 0);
216         if (sshpam_err != PAM_SUCCESS)
217                 goto auth_fail;
218         sshpam_err = pam_acct_mgmt(sshpam_handle, 0);
219         if (sshpam_err != PAM_SUCCESS && sshpam_err != PAM_NEW_AUTHTOK_REQD)
220                 goto auth_fail;
221         buffer_put_cstring(&buffer, "OK");
222         ssh_msg_send(ctxt->pam_csock, sshpam_err, &buffer);
223         buffer_free(&buffer);
224         pthread_exit(NULL);
225
226  auth_fail:
227         buffer_put_cstring(&buffer,
228             pam_strerror(sshpam_handle, sshpam_err));
229         ssh_msg_send(ctxt->pam_csock, PAM_AUTH_ERR, &buffer);
230         buffer_free(&buffer);
231         pthread_exit(NULL);
232         
233         return (NULL); /* Avoid warning for non-pthread case */
234 }
235
236 static void
237 sshpam_thread_cleanup(void *ctxtp)
238 {
239         struct pam_ctxt *ctxt = ctxtp;
240
241         pthread_cancel(ctxt->pam_thread);
242         pthread_join(ctxt->pam_thread, NULL);
243         close(ctxt->pam_psock);
244         close(ctxt->pam_csock);
245 }
246
247 static int
248 sshpam_null_conv(int n,
249          const struct pam_message **msg,
250          struct pam_response **resp,
251          void *data)
252 {
253
254         return (PAM_CONV_ERR);
255 }
256
257 static struct pam_conv null_conv = { sshpam_null_conv, NULL };
258
259 static void
260 sshpam_cleanup(void *arg)
261 {
262         (void)arg;
263         debug("PAM: cleanup");
264         pam_set_item(sshpam_handle, PAM_CONV, (const void *)&null_conv);
265         if (sshpam_cred_established) {
266                 pam_setcred(sshpam_handle, PAM_DELETE_CRED);
267                 sshpam_cred_established = 0;
268         }
269         if (sshpam_session_open) {
270                 pam_close_session(sshpam_handle, PAM_SILENT);
271                 sshpam_session_open = 0;
272         }
273         sshpam_authenticated = sshpam_new_authtok_reqd = 0;
274         pam_end(sshpam_handle, sshpam_err);
275         sshpam_handle = NULL;
276 }
277
278 static int
279 sshpam_init(const char *user)
280 {
281         extern u_int utmp_len;
282         const char *pam_rhost, *pam_user;
283
284         if (sshpam_handle != NULL) {
285                 /* We already have a PAM context; check if the user matches */
286                 sshpam_err = pam_get_item(sshpam_handle,
287                     PAM_USER, (const void **)&pam_user);
288                 if (sshpam_err == PAM_SUCCESS && strcmp(user, pam_user) == 0)
289                         return (0);
290                 fatal_remove_cleanup(sshpam_cleanup, NULL);
291                 pam_end(sshpam_handle, sshpam_err);
292                 sshpam_handle = NULL;
293         }
294         debug("PAM: initializing for \"%s\"", user);
295         sshpam_err = pam_start("sshd", user, &null_conv, &sshpam_handle);
296         if (sshpam_err != PAM_SUCCESS)
297                 return (-1);
298         pam_rhost = get_remote_name_or_ip(utmp_len,
299             options.verify_reverse_mapping);
300         debug("PAM: setting PAM_RHOST to \"%s\"", pam_rhost);
301         sshpam_err = pam_set_item(sshpam_handle, PAM_RHOST, pam_rhost);
302         if (sshpam_err != PAM_SUCCESS) {
303                 pam_end(sshpam_handle, sshpam_err);
304                 sshpam_handle = NULL;
305                 return (-1);
306         }
307         fatal_add_cleanup(sshpam_cleanup, NULL);
308         return (0);
309 }
310
311 static void *
312 sshpam_init_ctx(Authctxt *authctxt)
313 {
314         struct pam_ctxt *ctxt;
315         int socks[2];
316
317         /* Refuse to start if we don't have PAM enabled */
318         if (!options.use_pam)
319                 return NULL;
320
321         /* Initialize PAM */
322         if (sshpam_init(authctxt->user) == -1) {
323                 error("PAM: initialization failed");
324                 return (NULL);
325         }
326
327         ctxt = xmalloc(sizeof *ctxt);
328         ctxt->pam_done = 0;
329
330         /* Start the authentication thread */
331         if (socketpair(AF_UNIX, SOCK_STREAM, PF_UNSPEC, socks) == -1) {
332                 error("PAM: failed create sockets: %s", strerror(errno));
333                 xfree(ctxt);
334                 return (NULL);
335         }
336         ctxt->pam_psock = socks[0];
337         ctxt->pam_csock = socks[1];
338         if (pthread_create(&ctxt->pam_thread, NULL, sshpam_thread, ctxt) == -1) {
339                 error("PAM: failed to start authentication thread: %s",
340                     strerror(errno));
341                 close(socks[0]);
342                 close(socks[1]);
343                 xfree(ctxt);
344                 return (NULL);
345         }
346         fatal_add_cleanup(sshpam_thread_cleanup, ctxt);
347         return (ctxt);
348 }
349
350 static int
351 sshpam_query(void *ctx, char **name, char **info,
352     u_int *num, char ***prompts, u_int **echo_on)
353 {
354         Buffer buffer;
355         struct pam_ctxt *ctxt = ctx;
356         size_t plen;
357         u_char type;
358         char *msg;
359
360         buffer_init(&buffer);
361         *name = xstrdup("");
362         *info = xstrdup("");
363         *prompts = xmalloc(sizeof(char *));
364         **prompts = NULL;
365         plen = 0;
366         *echo_on = xmalloc(sizeof(u_int));
367         while (ssh_msg_recv(ctxt->pam_psock, &buffer) == 0) {
368                 type = buffer_get_char(&buffer);
369                 msg = buffer_get_string(&buffer, NULL);
370                 switch (type) {
371                 case PAM_PROMPT_ECHO_ON:
372                 case PAM_PROMPT_ECHO_OFF:
373                         *num = 1;
374                         **prompts = xrealloc(**prompts, plen + strlen(msg) + 1);
375                         plen += sprintf(**prompts + plen, "%s", msg);
376                         **echo_on = (type == PAM_PROMPT_ECHO_ON);
377                         xfree(msg);
378                         return (0);
379                 case PAM_ERROR_MSG:
380                 case PAM_TEXT_INFO:
381                         /* accumulate messages */
382                         **prompts = xrealloc(**prompts, plen + strlen(msg) + 1);
383                         plen += sprintf(**prompts + plen, "%s", msg);
384                         xfree(msg);
385                         break;
386                 case PAM_NEW_AUTHTOK_REQD:
387                         sshpam_new_authtok_reqd = 1;
388                         /* FALLTHROUGH */
389                 case PAM_SUCCESS:
390                 case PAM_AUTH_ERR:
391                         if (**prompts != NULL) {
392                                 /* drain any accumulated messages */
393 #if 0 /* XXX - not compatible with privsep */
394                                 packet_start(SSH2_MSG_USERAUTH_BANNER);
395                                 packet_put_cstring(**prompts);
396                                 packet_put_cstring("");
397                                 packet_send();
398                                 packet_write_wait();
399 #endif
400                                 xfree(**prompts);
401                                 **prompts = NULL;
402                         }
403                         if (type == PAM_SUCCESS) {
404                                 *num = 0;
405                                 **echo_on = 0;
406                                 ctxt->pam_done = 1;
407                                 xfree(msg);
408                                 return (0);
409                         }
410                         error("PAM: %s", msg);
411                 default:
412                         *num = 0;
413                         **echo_on = 0;
414                         xfree(msg);
415                         ctxt->pam_done = -1;
416                         return (-1);
417                 }
418         }
419         return (-1);
420 }
421
422 /* XXX - see also comment in auth-chall.c:verify_response */
423 static int
424 sshpam_respond(void *ctx, u_int num, char **resp)
425 {
426         Buffer buffer;
427         struct pam_ctxt *ctxt = ctx;
428
429         debug2("PAM: %s", __func__);
430         switch (ctxt->pam_done) {
431         case 1:
432                 sshpam_authenticated = 1;
433                 return (0);
434         case 0:
435                 break;
436         default:
437                 return (-1);
438         }
439         if (num != 1) {
440                 error("PAM: expected one response, got %u", num);
441                 return (-1);
442         }
443         buffer_init(&buffer);
444         buffer_put_cstring(&buffer, *resp);
445         ssh_msg_send(ctxt->pam_psock, PAM_AUTHTOK, &buffer);
446         buffer_free(&buffer);
447         return (1);
448 }
449
450 static void
451 sshpam_free_ctx(void *ctxtp)
452 {
453         struct pam_ctxt *ctxt = ctxtp;
454
455         fatal_remove_cleanup(sshpam_thread_cleanup, ctxt);
456         sshpam_thread_cleanup(ctxtp);
457         xfree(ctxt);
458         /*
459          * We don't call sshpam_cleanup() here because we may need the PAM
460          * handle at a later stage, e.g. when setting up a session.  It's
461          * still on the cleanup list, so pam_end() *will* be called before
462          * the server process terminates.
463          */
464 }
465
466 KbdintDevice sshpam_device = {
467         "pam",
468         sshpam_init_ctx,
469         sshpam_query,
470         sshpam_respond,
471         sshpam_free_ctx
472 };
473
474 KbdintDevice mm_sshpam_device = {
475         "pam",
476         mm_sshpam_init_ctx,
477         mm_sshpam_query,
478         mm_sshpam_respond,
479         mm_sshpam_free_ctx
480 };
481
482 /*
483  * This replaces auth-pam.c
484  */
485 void
486 start_pam(const char *user)
487 {
488         if (sshpam_init(user) == -1)
489                 fatal("PAM: initialisation failed");
490 }
491
492 void
493 finish_pam(void)
494 {
495         fatal_remove_cleanup(sshpam_cleanup, NULL);
496         sshpam_cleanup(NULL);
497 }
498
499 int
500 do_pam_account(const char *user, const char *ruser)
501 {
502         /* XXX */
503         return (1);
504 }
505
506 void
507 do_pam_session(const char *user, const char *tty)
508 {
509         sshpam_err = pam_set_item(sshpam_handle, PAM_CONV, 
510             (const void *)&null_conv);
511         if (sshpam_err != PAM_SUCCESS)
512                 fatal("PAM: failed to set PAM_CONV: %s",
513                     pam_strerror(sshpam_handle, sshpam_err));
514         debug("PAM: setting PAM_TTY to \"%s\"", tty);
515         sshpam_err = pam_set_item(sshpam_handle, PAM_TTY, tty);
516         if (sshpam_err != PAM_SUCCESS)
517                 fatal("PAM: failed to set PAM_TTY: %s",
518                     pam_strerror(sshpam_handle, sshpam_err));
519         sshpam_err = pam_open_session(sshpam_handle, 0);
520         if (sshpam_err != PAM_SUCCESS)
521                 fatal("PAM: pam_open_session(): %s",
522                     pam_strerror(sshpam_handle, sshpam_err));
523         sshpam_session_open = 1;
524 }
525
526 void
527 do_pam_setcred(int init)
528 {
529         sshpam_err = pam_set_item(sshpam_handle, PAM_CONV,
530             (const void *)&null_conv);
531         if (sshpam_err != PAM_SUCCESS)
532                 fatal("PAM: failed to set PAM_CONV: %s",
533                     pam_strerror(sshpam_handle, sshpam_err));
534         if (init) {
535                 debug("PAM: establishing credentials");
536                 sshpam_err = pam_setcred(sshpam_handle, PAM_ESTABLISH_CRED);
537         } else {
538                 debug("PAM: reinitializing credentials");
539                 sshpam_err = pam_setcred(sshpam_handle, PAM_REINITIALIZE_CRED);
540         }
541         if (sshpam_err == PAM_SUCCESS) {
542                 sshpam_cred_established = 1;
543                 return;
544         }
545         if (sshpam_authenticated)
546                 fatal("PAM: pam_setcred(): %s",
547                     pam_strerror(sshpam_handle, sshpam_err));
548         else
549                 debug("PAM: pam_setcred(): %s",
550                     pam_strerror(sshpam_handle, sshpam_err));
551 }
552
553 int
554 is_pam_password_change_required(void)
555 {
556         return (sshpam_new_authtok_reqd);
557 }
558
559 static int
560 pam_chauthtok_conv(int n,
561          const struct pam_message **msg,
562          struct pam_response **resp,
563          void *data)
564 {
565         char input[PAM_MAX_MSG_SIZE];
566         int i;
567
568         if (n <= 0 || n > PAM_MAX_NUM_MSG)
569                 return (PAM_CONV_ERR);
570         *resp = xmalloc(n * sizeof **resp);
571         for (i = 0; i < n; ++i) {
572                 switch (PAM_MSG_MEMBER(msg, i, msg_style)) {
573                 case PAM_PROMPT_ECHO_OFF:
574                         resp[i]->resp =
575                             read_passphrase(PAM_MSG_MEMBER(msg, i, msg), 
576                             RP_ALLOW_STDIN);
577                         resp[i]->resp_retcode = PAM_SUCCESS;
578                         break;
579                 case PAM_PROMPT_ECHO_ON:
580                         fputs(PAM_MSG_MEMBER(msg, i, msg), stderr);
581                         fgets(input, sizeof input, stdin);
582                         resp[i]->resp = xstrdup(input);
583                         resp[i]->resp_retcode = PAM_SUCCESS;
584                         break;
585                 case PAM_ERROR_MSG:
586                 case PAM_TEXT_INFO:
587                         fputs(PAM_MSG_MEMBER(msg, i, msg), stderr);
588                         resp[i]->resp_retcode = PAM_SUCCESS;
589                         break;
590                 default:
591                         goto fail;
592                 }
593         }
594         return (PAM_SUCCESS);
595  fail:
596         while (i)
597                 xfree(resp[--i]);
598         xfree(*resp);
599         *resp = NULL;
600         return (PAM_CONV_ERR);
601 }
602
603 /*
604  * XXX this should be done in the authentication phase, but ssh1 doesn't
605  * support that
606  */
607 void
608 do_pam_chauthtok(void)
609 {
610         struct pam_conv pam_conv = { pam_chauthtok_conv, NULL };
611
612         if (use_privsep)
613                 fatal("PAM: chauthtok not supprted with privsep");
614         sshpam_err = pam_set_item(sshpam_handle, PAM_CONV,
615             (const void *)&pam_conv);
616         if (sshpam_err != PAM_SUCCESS)
617                 fatal("PAM: failed to set PAM_CONV: %s",
618                     pam_strerror(sshpam_handle, sshpam_err));
619         debug("PAM: changing password");
620         sshpam_err = pam_chauthtok(sshpam_handle, PAM_CHANGE_EXPIRED_AUTHTOK);
621         if (sshpam_err != PAM_SUCCESS)
622                 fatal("PAM: pam_chauthtok(): %s",
623                     pam_strerror(sshpam_handle, sshpam_err));
624 }
625
626 void
627 print_pam_messages(void)
628 {
629         /* XXX */
630 }
631
632 char **
633 fetch_pam_environment(void)
634 {
635 #ifdef HAVE_PAM_GETENVLIST
636         debug("PAM: retrieving environment");
637         return (pam_getenvlist(sshpam_handle));
638 #else
639         return (NULL);
640 #endif
641 }
642
643 void
644 free_pam_environment(char **env)
645 {
646         char **envp;
647
648         for (envp = env; *envp; envp++)
649                 xfree(*envp);
650         xfree(env);
651 }
652
653 #endif /* USE_PAM */
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