summaryrefslogtreecommitdiff
path: root/src/login/pam_systemd.c
blob: d5b29c8af466b5a873ad6917c9efec64c770356e (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/

/***
  This file is part of systemd.

  Copyright 2010 Lennart Poettering

  systemd is free software; you can redistribute it and/or modify it
  under the terms of the GNU Lesser General Public License as published by
  the Free Software Foundation; either version 2.1 of the License, or
  (at your option) any later version.

  systemd is distributed in the hope that it will be useful, but
  WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  Lesser General Public License for more details.

  You should have received a copy of the GNU Lesser General Public License
  along with systemd; If not, see <http://www.gnu.org/licenses/>.
***/

#include <errno.h>
#include <fcntl.h>
#include <sys/file.h>
#include <pwd.h>
#include <endian.h>

#include <security/pam_modules.h>
#include <security/_pam_macros.h>
#include <security/pam_modutil.h>
#include <security/pam_ext.h>
#include <security/pam_misc.h>

#include "util.h"
#include "audit.h"
#include "macro.h"
#include "strv.h"
#include "bus-util.h"
#include "def.h"
#include "socket-util.h"
#include "fileio.h"
#include "bus-error.h"

static int parse_argv(
                pam_handle_t *handle,
                int argc, const char **argv,
                const char **class,
                const char **type,
                bool *debug) {

        unsigned i;

        assert(argc >= 0);
        assert(argc == 0 || argv);

        for (i = 0; i < (unsigned) argc; i++) {
                if (startswith(argv[i], "class=")) {
                        if (class)
                                *class = argv[i] + 6;

                } else if (startswith(argv[i], "type=")) {
                        if (type)
                                *type = argv[i] + 5;

                } else if (streq(argv[i], "debug")) {
                        if (debug)
                                *debug = true;

                } else if (startswith(argv[i], "debug=")) {
                        int k;

                        k = parse_boolean(argv[i] + 6);
                        if (k < 0)
                                pam_syslog(handle, LOG_WARNING, "Failed to parse debug= argument, ignoring.");
                        else if (debug)
                                *debug = k;

                } else
                        pam_syslog(handle, LOG_WARNING, "Unknown parameter '%s', ignoring", argv[i]);
        }

        return 0;
}

static int get_user_data(
                pam_handle_t *handle,
                const char **ret_username,
                struct passwd **ret_pw) {

        const char *username = NULL;
        struct passwd *pw = NULL;
        int r;

        assert(handle);
        assert(ret_username);
        assert(ret_pw);

        r = pam_get_user(handle, &username, NULL);
        if (r != PAM_SUCCESS) {
                pam_syslog(handle, LOG_ERR, "Failed to get user name.");
                return r;
        }

        if (isempty(username)) {
                pam_syslog(handle, LOG_ERR, "User name not valid.");
                return PAM_AUTH_ERR;
        }

        pw = pam_modutil_getpwnam(handle, username);
        if (!pw) {
                pam_syslog(handle, LOG_ERR, "Failed to get user data.");
                return PAM_USER_UNKNOWN;
        }

        *ret_pw = pw;
        *ret_username = username;

        return PAM_SUCCESS;
}

static int get_seat_from_display(const char *display, const char **seat, uint32_t *vtnr) {
        union sockaddr_union sa = {
                .un.sun_family = AF_UNIX,
        };
        _cleanup_free_ char *p = NULL, *tty = NULL;
        _cleanup_close_ int fd = -1;
        struct ucred ucred;
        int v, r;

        assert(display);
        assert(vtnr);

        /* We deduce the X11 socket from the display name, then use
         * SO_PEERCRED to determine the X11 server process, ask for
         * the controlling tty of that and if it's a VC then we know
         * the seat and the virtual terminal. Sounds ugly, is only
         * semi-ugly. */

        r = socket_from_display(display, &p);
        if (r < 0)
                return r;
        strncpy(sa.un.sun_path, p, sizeof(sa.un.sun_path)-1);

        fd = socket(AF_UNIX, SOCK_STREAM|SOCK_CLOEXEC, 0);
        if (fd < 0)
                return -errno;

        if (connect(fd, &sa.sa, offsetof(struct sockaddr_un, sun_path) + strlen(sa.un.sun_path)) < 0)
                return -errno;

        r = getpeercred(fd, &ucred);
        if (r < 0)
                return r;

        r = get_ctty(ucred.pid, NULL, &tty);
        if (r < 0)
                return r;

        v = vtnr_from_tty(tty);
        if (v < 0)
                return v;
        else if (v == 0)
                return -ENOENT;

        if (seat)
                *seat = "seat0";
        *vtnr = (uint32_t) v;

        return 0;
}

static int export_legacy_dbus_address(
                pam_handle_t *handle,
                uid_t uid,
                const char *runtime) {

#ifdef ENABLE_KDBUS
        _cleanup_free_ char *s = NULL;
        int r;

        /* skip export if kdbus is not active */
        if (access("/sys/fs/kdbus", F_OK) < 0)
                return PAM_SUCCESS;

        if (asprintf(&s, KERNEL_USER_BUS_ADDRESS_FMT ";" UNIX_USER_BUS_ADDRESS_FMT, uid, runtime) < 0) {
                pam_syslog(handle, LOG_ERR, "Failed to set bus variable.");
                return PAM_BUF_ERR;
        }

        r = pam_misc_setenv(handle, "DBUS_SESSION_BUS_ADDRESS", s, 0);
        if (r != PAM_SUCCESS) {
                pam_syslog(handle, LOG_ERR, "Failed to set bus variable.");
                return r;
        }
#endif
        return PAM_SUCCESS;
}

_public_ PAM_EXTERN int pam_sm_open_session(
                pam_handle_t *handle,
                int flags,
                int argc, const char **argv) {

        _cleanup_bus_error_free_ sd_bus_error error = SD_BUS_ERROR_NULL;
        _cleanup_bus_message_unref_ sd_bus_message *reply = NULL;
        const char
                *username, *id, *object_path, *runtime_path,
                *service = NULL,
                *tty = NULL, *display = NULL,
                *remote_user = NULL, *remote_host = NULL,
                *seat = NULL,
                *type = NULL, *class = NULL,
                *class_pam = NULL, *type_pam = NULL, *cvtnr = NULL, *desktop = NULL;
        _cleanup_bus_close_unref_ sd_bus *bus = NULL;
        int session_fd = -1, existing, r;
        bool debug = false, remote;
        struct passwd *pw;
        uint32_t vtnr = 0;
        uid_t original_uid;

        assert(handle);

        /* Make this a NOP on non-logind systems */
        if (!logind_running())
                return PAM_SUCCESS;

        if (parse_argv(handle,
                       argc, argv,
                       &class_pam,
                       &type_pam,
                       &debug) < 0)
                return PAM_SESSION_ERR;

        if (debug)
                pam_syslog(handle, LOG_DEBUG, "pam-systemd initializing");

        r = get_user_data(handle, &username, &pw);
        if (r != PAM_SUCCESS) {
                pam_syslog(handle, LOG_ERR, "Failed to get user data.");
                return r;
        }

        /* Make sure we don't enter a loop by talking to
         * systemd-logind when it is actually waiting for the
         * background to finish start-up. If the service is
         * "systemd-user" we simply set XDG_RUNTIME_DIR and
         * leave. */

        pam_get_item(handle, PAM_SERVICE, (const void**) &service);
        if (streq_ptr(service, "systemd-user")) {
                _cleanup_free_ char *p = NULL, *rt = NULL;

                if (asprintf(&p, "/run/systemd/users/"UID_FMT, pw->pw_uid) < 0)
                        return PAM_BUF_ERR;

                r = parse_env_file(p, NEWLINE,
                                   "RUNTIME", &rt,
                                   NULL);
                if (r < 0 && r != -ENOENT)
                        return PAM_SESSION_ERR;

                if (rt)  {
                        r = pam_misc_setenv(handle, "XDG_RUNTIME_DIR", rt, 0);
                        if (r != PAM_SUCCESS) {
                                pam_syslog(handle, LOG_ERR, "Failed to set runtime dir.");
                                return r;
                        }

                        r = export_legacy_dbus_address(handle, pw->pw_uid, rt);
                        if (r != PAM_SUCCESS)
                                return r;
                }

                return PAM_SUCCESS;
        }

        /* Otherwise, we ask logind to create a session for us */

        pam_get_item(handle, PAM_XDISPLAY, (const void**) &display);
        pam_get_item(handle, PAM_TTY, (const void**) &tty);
        pam_get_item(handle, PAM_RUSER, (const void**) &remote_user);
        pam_get_item(handle, PAM_RHOST, (const void**) &remote_host);

        seat = pam_getenv(handle, "XDG_SEAT");
        if (isempty(seat))
                seat = getenv("XDG_SEAT");

        cvtnr = pam_getenv(handle, "XDG_VTNR");
        if (isempty(cvtnr))
                cvtnr = getenv("XDG_VTNR");

        type = pam_getenv(handle, "XDG_SESSION_TYPE");
        if (isempty(type))
                type = getenv("XDG_SESSION_TYPE");
        if (isempty(type))
                type = type_pam;

        class = pam_getenv(handle, "XDG_SESSION_CLASS");
        if (isempty(class))
                class = getenv("XDG_SESSION_CLASS");
        if (isempty(class))
                class = class_pam;

        desktop = pam_getenv(handle, "XDG_SESSION_DESKTOP");
        if (isempty(desktop))
                desktop = getenv("XDG_SESSION_DESKTOP");

        tty = strempty(tty);

        if (strchr(tty, ':')) {
                /* A tty with a colon is usually an X11 display,
                 * placed there to show up in utmp. We rearrange
                 * things and don't pretend that an X display was a
                 * tty. */

                if (isempty(display))
                        display = tty;
                tty = NULL;
        } else if (streq(tty, "cron")) {
                /* cron has been setting PAM_TTY to "cron" for a very
                 * long time and it probably shouldn't stop doing that
                 * for compatibility reasons. */
                type = "unspecified";
                class = "background";
                tty = NULL;
        } else if (streq(tty, "ssh")) {
                /* ssh has been setting PAM_TTY to "ssh" for a very
                 * long time and probably shouldn't stop doing that
                 * for compatibility reasons. */
                type ="tty";
                class = "user";
                tty = NULL;
        }

        /* If this fails vtnr will be 0, that's intended */
        if (!isempty(cvtnr))
                safe_atou32(cvtnr, &vtnr);

        if (!isempty(display) && !vtnr) {
                if (isempty(seat))
                        get_seat_from_display(display, &seat, &vtnr);
                else if (streq(seat, "seat0"))
                        get_seat_from_display(display, NULL, &vtnr);
        }

        if (seat && !streq(seat, "seat0") && vtnr != 0) {
                pam_syslog(handle, LOG_DEBUG, "Ignoring vtnr %d for %s which is not seat0", vtnr, seat);
                vtnr = 0;
        }

        if (isempty(type))
                type = !isempty(display) ? "x11" :
                           !isempty(tty) ? "tty" : "unspecified";

        if (isempty(class))
                class = streq(type, "unspecified") ? "background" : "user";

        remote = !isempty(remote_host) && !is_localhost(remote_host);

        /* Talk to logind over the message bus */

        r = sd_bus_open_system(&bus);
        if (r < 0) {
                pam_syslog(handle, LOG_ERR, "Failed to connect to system bus: %s", strerror(-r));
                return PAM_SESSION_ERR;
        }

        if (debug)
                pam_syslog(handle, LOG_DEBUG, "Asking logind to create session: "
                           "uid=%u pid=%u service=%s type=%s class=%s desktop=%s seat=%s vtnr=%u tty=%s display=%s remote=%s remote_user=%s remote_host=%s",
                           pw->pw_uid, getpid(),
                           strempty(service),
                           type, class, strempty(desktop),
                           strempty(seat), vtnr, strempty(tty), strempty(display),
                           yes_no(remote), strempty(remote_user), strempty(remote_host));

        r = sd_bus_call_method(bus,
                               "org.freedesktop.login1",
                               "/org/freedesktop/login1",
                               "org.freedesktop.login1.Manager",
                               "CreateSession",
                               &error,
                               &reply,
                               "uusssssussbssa(sv)",
                               (uint32_t) pw->pw_uid,
                               (uint32_t) getpid(),
                               service,
                               type,
                               class,
                               desktop,
                               seat,
                               vtnr,
                               tty,
                               display,
                               remote,
                               remote_user,
                               remote_host,
                               0);
        if (r < 0) {
                pam_syslog(handle, LOG_ERR, "Failed to create session: %s", bus_error_message(&error, r));
                return PAM_SYSTEM_ERR;
        }

        r = sd_bus_message_read(reply,
                                "soshusub",
                                &id,
                                &object_path,
                                &runtime_path,
                                &session_fd,
                                &original_uid,
                                &seat,
                                &vtnr,
                                &existing);
        if (r < 0) {
                pam_syslog(handle, LOG_ERR, "Failed to parse message: %s", strerror(-r));
                return PAM_SESSION_ERR;
        }

        if (debug)
                pam_syslog(handle, LOG_DEBUG, "Reply from logind: "
                           "id=%s object_path=%s runtime_path=%s session_fd=%d seat=%s vtnr=%u original_uid=%u",
                           id, object_path, runtime_path, session_fd, seat, vtnr, original_uid);

        r = pam_misc_setenv(handle, "XDG_SESSION_ID", id, 0);
        if (r != PAM_SUCCESS) {
                pam_syslog(handle, LOG_ERR, "Failed to set session id.");
                return r;
        }

        if (original_uid == pw->pw_uid) {
                /* Don't set $XDG_RUNTIME_DIR if the user we now
                 * authenticated for does not match the original user
                 * of the session. We do this in order not to result
                 * in privileged apps clobbering the runtime directory
                 * unnecessarily. */

                r = pam_misc_setenv(handle, "XDG_RUNTIME_DIR", runtime_path, 0);
                if (r != PAM_SUCCESS) {
                        pam_syslog(handle, LOG_ERR, "Failed to set runtime dir.");
                        return r;
                }

                r = export_legacy_dbus_address(handle, pw->pw_uid, runtime_path);
                if (r != PAM_SUCCESS)
                        return r;
        }

        if (!isempty(seat)) {
                r = pam_misc_setenv(handle, "XDG_SEAT", seat, 0);
                if (r != PAM_SUCCESS) {
                        pam_syslog(handle, LOG_ERR, "Failed to set seat.");
                        return r;
                }
        }

        if (vtnr > 0) {
                char buf[DECIMAL_STR_MAX(vtnr)];
                sprintf(buf, "%u", vtnr);

                r = pam_misc_setenv(handle, "XDG_VTNR", buf, 0);
                if (r != PAM_SUCCESS) {
                        pam_syslog(handle, LOG_ERR, "Failed to set virtual terminal number.");
                        return r;
                }
        }

        r = pam_set_data(handle, "systemd.existing", INT_TO_PTR(!!existing), NULL);
        if (r != PAM_SUCCESS) {
                pam_syslog(handle, LOG_ERR, "Failed to install existing flag.");
                return r;
        }

        if (session_fd >= 0) {
                session_fd = fcntl(session_fd, F_DUPFD_CLOEXEC, 3);
                if (session_fd < 0) {
                        pam_syslog(handle, LOG_ERR, "Failed to dup session fd: %m");
                        return PAM_SESSION_ERR;
                }

                r = pam_set_data(handle, "systemd.session-fd", INT_TO_PTR(session_fd+1), NULL);
                if (r != PAM_SUCCESS) {
                        pam_syslog(handle, LOG_ERR, "Failed to install session fd.");
                        safe_close(session_fd);
                        return r;
                }
        }

        return PAM_SUCCESS;
}

_public_ PAM_EXTERN int pam_sm_close_session(
                pam_handle_t *handle,
                int flags,
                int argc, const char **argv) {

        _cleanup_bus_error_free_ sd_bus_error error = SD_BUS_ERROR_NULL;
        _cleanup_bus_close_unref_ sd_bus *bus = NULL;
        const void *existing = NULL;
        const char *id;
        int r;

        assert(handle);

        /* Only release session if it wasn't pre-existing when we
         * tried to create it */
        pam_get_data(handle, "systemd.existing", &existing);

        id = pam_getenv(handle, "XDG_SESSION_ID");
        if (id && !existing) {

                /* Before we go and close the FIFO we need to tell
                 * logind that this is a clean session shutdown, so
                 * that it doesn't just go and slaughter us
                 * immediately after closing the fd */

                r = sd_bus_open_system(&bus);
                if (r < 0) {
                        pam_syslog(handle, LOG_ERR, "Failed to connect to system bus: %s", strerror(-r));
                        return PAM_SESSION_ERR;
                }

                r = sd_bus_call_method(bus,
                                       "org.freedesktop.login1",
                                       "/org/freedesktop/login1",
                                       "org.freedesktop.login1.Manager",
                                       "ReleaseSession",
                                       &error,
                                       NULL,
                                       "s",
                                       id);
                if (r < 0) {
                        pam_syslog(handle, LOG_ERR, "Failed to release session: %s", bus_error_message(&error, r));
                        return PAM_SESSION_ERR;
                }
        }

        /* Note that we are knowingly leaking the FIFO fd here. This
         * way, logind can watch us die. If we closed it here it would
         * not have any clue when that is completed. Given that one
         * cannot really have multiple PAM sessions open from the same
         * process this means we will leak one FD at max. */

        return PAM_SUCCESS;
}