src/login/pam_systemd.c

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2 /***
   3   This file is part of systemd.
   4
   5   Copyright 2010 Lennart Poettering
   6 ***/
   7
   8 #include <endian.h>
   9 #include <errno.h>
  10 #include <fcntl.h>
  11 #include <pwd.h>
  12 #include <security/_pam_macros.h>
  13 #include <security/pam_ext.h>
  14 #include <security/pam_misc.h>
  15 #include <security/pam_modules.h>
  16 #include <security/pam_modutil.h>
  17 #include <sys/file.h>
  18
  19 #include "alloc-util.h"
  20 #include "audit-util.h"
  21 #include "bus-common-errors.h"
  22 #include "bus-error.h"
  23 #include "bus-util.h"
  24 #include "def.h"
  25 #include "fd-util.h"
  26 #include "fileio.h"
  27 #include "format-util.h"
  28 #include "hostname-util.h"
  29 #include "login-util.h"
  30 #include "macro.h"
  31 #include "parse-util.h"
  32 #include "process-util.h"
  33 #include "socket-util.h"
  34 #include "strv.h"
  35 #include "terminal-util.h"
  36 #include "util.h"
  37 #include "path-util.h"
  38 #include "cgroup-util.h"
  39
  40 static int parse_argv(
  41                 pam_handle_t *handle,
  42                 int argc, const char **argv,
  43                 const char **class,
  44                 const char **type,
  45                 bool *debug) {
  46
  47         unsigned i;
  48
  49         assert(argc >= 0);
  50         assert(argc == 0 || argv);
  51
  52         for (i = 0; i < (unsigned) argc; i++) {
  53                 if (startswith(argv[i], "class=")) {
  54                         if (class)
  55                                 *class = argv[i] + 6;
  56
  57                 } else if (startswith(argv[i], "type=")) {
  58                         if (type)
  59                                 *type = argv[i] + 5;
  60
  61                 } else if (streq(argv[i], "debug")) {
  62                         if (debug)
  63                                 *debug = true;
  64
  65                 } else if (startswith(argv[i], "debug=")) {
  66                         int k;
  67
  68                         k = parse_boolean(argv[i] + 6);
  69                         if (k < 0)
  70                                 pam_syslog(handle, LOG_WARNING, "Failed to parse debug= argument, ignoring.");
  71                         else if (debug)
  72                                 *debug = k;
  73
  74                 } else
  75                         pam_syslog(handle, LOG_WARNING, "Unknown parameter '%s', ignoring", argv[i]);
  76         }
  77
  78         return 0;
  79 }
  80
  81 static int get_user_data(
  82                 pam_handle_t *handle,
  83                 const char **ret_username,
  84                 struct passwd **ret_pw) {
  85
  86         const char *username = NULL;
  87         struct passwd *pw = NULL;
  88         int r;
  89
  90         assert(handle);
  91         assert(ret_username);
  92         assert(ret_pw);
  93
  94         r = pam_get_user(handle, &username, NULL);
  95         if (r != PAM_SUCCESS) {
  96                 pam_syslog(handle, LOG_ERR, "Failed to get user name.");
  97                 return r;
  98         }
  99
 100         if (isempty(username)) {
 101                 pam_syslog(handle, LOG_ERR, "User name not valid.");
 102                 return PAM_AUTH_ERR;
 103         }
 104
 105         pw = pam_modutil_getpwnam(handle, username);
 106         if (!pw) {
 107                 pam_syslog(handle, LOG_ERR, "Failed to get user data.");
 108                 return PAM_USER_UNKNOWN;
 109         }
 110
 111         *ret_pw = pw;
 112         *ret_username = username;
 113
 114         return PAM_SUCCESS;
 115 }
 116
 117 static int get_seat_from_display(const char *display, const char **seat, uint32_t *vtnr) {
 118         union sockaddr_union sa = {
 119                 .un.sun_family = AF_UNIX,
 120         };
 121         _cleanup_free_ char *p = NULL, *tty = NULL;
 122         _cleanup_close_ int fd = -1;
 123         struct ucred ucred;
 124         int v, r;
 125
 126         assert(display);
 127         assert(vtnr);
 128
 129         /* We deduce the X11 socket from the display name, then use
 130          * SO_PEERCRED to determine the X11 server process, ask for
 131          * the controlling tty of that and if it's a VC then we know
 132          * the seat and the virtual terminal. Sounds ugly, is only
 133          * semi-ugly. */
 134
 135         r = socket_from_display(display, &p);
 136         if (r < 0)
 137                 return r;
 138         strncpy(sa.un.sun_path, p, sizeof(sa.un.sun_path)-1);
 139
 140         fd = socket(AF_UNIX, SOCK_STREAM|SOCK_CLOEXEC, 0);
 141         if (fd < 0)
 142                 return -errno;
 143
 144         if (connect(fd, &sa.sa, SOCKADDR_UN_LEN(sa.un)) < 0)
 145                 return -errno;
 146
 147         r = getpeercred(fd, &ucred);
 148         if (r < 0)
 149                 return r;
 150
 151         r = get_ctty(ucred.pid, NULL, &tty);
 152         if (r < 0)
 153                 return r;
 154
 155         v = vtnr_from_tty(tty);
 156         if (v < 0)
 157                 return v;
 158         else if (v == 0)
 159                 return -ENOENT;
 160
 161         if (seat)
 162                 *seat = "seat0";
 163         *vtnr = (uint32_t) v;
 164
 165         return 0;
 166 }
 167
 168 static int export_legacy_dbus_address(
 169                 pam_handle_t *handle,
 170                 uid_t uid,
 171                 const char *runtime) {
 172
 173         _cleanup_free_ char *s = NULL;
 174         int r = PAM_BUF_ERR;
 175
 176         /* FIXME: We *really* should move the access() check into the
 177          * daemons that spawn dbus-daemon, instead of forcing
 178          * DBUS_SESSION_BUS_ADDRESS= here. */
 179
 180         s = strjoin(runtime, "/bus");
 181         if (!s)
 182                 goto error;
 183
 184         if (access(s, F_OK) < 0)
 185                 return PAM_SUCCESS;
 186
 187         s = mfree(s);
 188         if (asprintf(&s, DEFAULT_USER_BUS_ADDRESS_FMT, runtime) < 0)
 189                 goto error;
 190
 191         r = pam_misc_setenv(handle, "DBUS_SESSION_BUS_ADDRESS", s, 0);
 192         if (r != PAM_SUCCESS)
 193                 goto error;
 194
 195         return PAM_SUCCESS;
 196
 197 error:
 198         pam_syslog(handle, LOG_ERR, "Failed to set bus variable.");
 199         return r;
 200 }
 201
 202 static int append_session_memory_max(pam_handle_t *handle, sd_bus_message *m, const char *limit) {
 203         uint64_t val;
 204         int r;
 205
 206         if (isempty(limit))
 207                 return 0;
 208
 209         if (streq(limit, "infinity")) {
 210                 r = sd_bus_message_append(m, "(sv)", "MemoryMax", "t", (uint64_t)-1);
 211                 if (r < 0) {
 212                         pam_syslog(handle, LOG_ERR, "Failed to append to bus message: %s", strerror(-r));
 213                         return r;
 214                 }
 215         } else {
 216                 r = parse_percent(limit);
 217                 if (r >= 0) {
 218                         r = sd_bus_message_append(m, "(sv)", "MemoryMaxScale", "u", (uint32_t) (((uint64_t) UINT32_MAX * r) / 100U));
 219                         if (r < 0) {
 220                                 pam_syslog(handle, LOG_ERR, "Failed to append to bus message: %s", strerror(-r));
 221                                 return r;
 222                         }
 223                 } else {
 224                         r = parse_size(limit, 1024, &val);
 225                         if (r >= 0) {
 226                                 r = sd_bus_message_append(m, "(sv)", "MemoryMax", "t", val);
 227                                 if (r < 0) {
 228                                         pam_syslog(handle, LOG_ERR, "Failed to append to bus message: %s", strerror(-r));
 229                                         return r;
 230                                 }
 231                         } else
 232                                 pam_syslog(handle, LOG_WARNING, "Failed to parse systemd.limit: %s, ignoring.", limit);
 233                 }
 234         }
 235
 236         return 0;
 237 }
 238
 239 static int append_session_tasks_max(pam_handle_t *handle, sd_bus_message *m, const char *limit)
 240 {
 241         uint64_t val;
 242         int r;
 243
 244         /* No need to parse "infinity" here, it will be set unconditionally later in manager_start_scope() */
 245         if (isempty(limit) || streq(limit, "infinity"))
 246                 return 0;
 247
 248         r = safe_atou64(limit, &val);
 249         if (r >= 0) {
 250                 r = sd_bus_message_append(m, "(sv)", "TasksMax", "t", val);
 251                 if (r < 0) {
 252                         pam_syslog(handle, LOG_ERR, "Failed to append to bus message: %s", strerror(-r));
 253                         return r;
 254                 }
 255         } else
 256                 pam_syslog(handle, LOG_WARNING, "Failed to parse systemd.limit: %s, ignoring.", limit);
 257
 258         return 0;
 259 }
 260
 261 static int append_session_cg_weight(pam_handle_t *handle, sd_bus_message *m, const char *limit, const char *field) {
 262         uint64_t val;
 263         int r;
 264
 265         if (!isempty(limit)) {
 266                 r = cg_weight_parse(limit, &val);
 267                 if (r >= 0) {
 268                         r = sd_bus_message_append(m, "(sv)", field, "t", val);
 269                         if (r < 0) {
 270                                 pam_syslog(handle, LOG_ERR, "Failed to append to bus message: %s", strerror(-r));
 271                                 return r;
 272                         }
 273                 } else if (streq(field, "CPUWeight"))
 274                         pam_syslog(handle, LOG_WARNING, "Failed to parse systemd.cpu_weight: %s, ignoring.", limit);
 275                 else
 276                         pam_syslog(handle, LOG_WARNING, "Failed to parse systemd.io_weight: %s, ignoring.", limit);
 277         }
 278
 279         return 0;
 280 }
 281
 282 _public_ PAM_EXTERN int pam_sm_open_session(
 283                 pam_handle_t *handle,
 284                 int flags,
 285                 int argc, const char **argv) {
 286
 287         _cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
 288         _cleanup_(sd_bus_message_unrefp) sd_bus_message *m = NULL, *reply = NULL;
 289         const char
 290                 *username, *id, *object_path, *runtime_path,
 291                 *service = NULL,
 292                 *tty = NULL, *display = NULL,
 293                 *remote_user = NULL, *remote_host = NULL,
 294                 *seat = NULL,
 295                 *type = NULL, *class = NULL,
 296                 *class_pam = NULL, *type_pam = NULL, *cvtnr = NULL, *desktop = NULL,
 297                 *memory_max = NULL, *tasks_max = NULL, *cpu_weight = NULL, *io_weight = NULL;
 298         _cleanup_(sd_bus_flush_close_unrefp) sd_bus *bus = NULL;
 299         int session_fd = -1, existing, r;
 300         bool debug = false, remote;
 301         struct passwd *pw;
 302         uint32_t vtnr = 0;
 303         uid_t original_uid;
 304
 305         assert(handle);
 306
 307         /* Make this a NOP on non-logind systems */
 308         if (!logind_running())
 309                 return PAM_SUCCESS;
 310
 311         if (parse_argv(handle,
 312                        argc, argv,
 313                        &class_pam,
 314                        &type_pam,
 315                        &debug) < 0)
 316                 return PAM_SESSION_ERR;
 317
 318         if (debug)
 319                 pam_syslog(handle, LOG_DEBUG, "pam-systemd initializing");
 320
 321         r = get_user_data(handle, &username, &pw);
 322         if (r != PAM_SUCCESS) {
 323                 pam_syslog(handle, LOG_ERR, "Failed to get user data.");
 324                 return r;
 325         }
 326
 327         /* Make sure we don't enter a loop by talking to
 328          * systemd-logind when it is actually waiting for the
 329          * background to finish start-up. If the service is
 330          * "systemd-user" we simply set XDG_RUNTIME_DIR and
 331          * leave. */
 332
 333         pam_get_item(handle, PAM_SERVICE, (const void**) &service);
 334         if (streq_ptr(service, "systemd-user")) {
 335                 _cleanup_free_ char *rt = NULL;
 336
 337                 if (asprintf(&rt, "/run/user/"UID_FMT, pw->pw_uid) < 0)
 338                         return PAM_BUF_ERR;
 339
 340                 r = pam_misc_setenv(handle, "XDG_RUNTIME_DIR", rt, 0);
 341                 if (r != PAM_SUCCESS) {
 342                         pam_syslog(handle, LOG_ERR, "Failed to set runtime dir.");
 343                         return r;
 344                 }
 345
 346                 r = export_legacy_dbus_address(handle, pw->pw_uid, rt);
 347                 if (r != PAM_SUCCESS)
 348                         return r;
 349
 350                 return PAM_SUCCESS;
 351         }
 352
 353         /* Otherwise, we ask logind to create a session for us */
 354
 355         pam_get_item(handle, PAM_XDISPLAY, (const void**) &display);
 356         pam_get_item(handle, PAM_TTY, (const void**) &tty);
 357         pam_get_item(handle, PAM_RUSER, (const void**) &remote_user);
 358         pam_get_item(handle, PAM_RHOST, (const void**) &remote_host);
 359
 360         seat = pam_getenv(handle, "XDG_SEAT");
 361         if (isempty(seat))
 362                 seat = getenv("XDG_SEAT");
 363
 364         cvtnr = pam_getenv(handle, "XDG_VTNR");
 365         if (isempty(cvtnr))
 366                 cvtnr = getenv("XDG_VTNR");
 367
 368         type = pam_getenv(handle, "XDG_SESSION_TYPE");
 369         if (isempty(type))
 370                 type = getenv("XDG_SESSION_TYPE");
 371         if (isempty(type))
 372                 type = type_pam;
 373
 374         class = pam_getenv(handle, "XDG_SESSION_CLASS");
 375         if (isempty(class))
 376                 class = getenv("XDG_SESSION_CLASS");
 377         if (isempty(class))
 378                 class = class_pam;
 379
 380         desktop = pam_getenv(handle, "XDG_SESSION_DESKTOP");
 381         if (isempty(desktop))
 382                 desktop = getenv("XDG_SESSION_DESKTOP");
 383
 384         tty = strempty(tty);
 385
 386         if (strchr(tty, ':')) {
 387                 /* A tty with a colon is usually an X11 display,
 388                  * placed there to show up in utmp. We rearrange
 389                  * things and don't pretend that an X display was a
 390                  * tty. */
 391
 392                 if (isempty(display))
 393                         display = tty;
 394                 tty = NULL;
 395         } else if (streq(tty, "cron")) {
 396                 /* cron has been setting PAM_TTY to "cron" for a very
 397                  * long time and it probably shouldn't stop doing that
 398                  * for compatibility reasons. */
 399                 type = "unspecified";
 400                 class = "background";
 401                 tty = NULL;
 402         } else if (streq(tty, "ssh")) {
 403                 /* ssh has been setting PAM_TTY to "ssh" for a very
 404                  * long time and probably shouldn't stop doing that
 405                  * for compatibility reasons. */
 406                 type ="tty";
 407                 class = "user";
 408                 tty = NULL;
 409         } else
 410                 /* Chop off leading /dev prefix that some clients specify, but others do not. */
 411                 tty = skip_dev_prefix(tty);
 412
 413         /* If this fails vtnr will be 0, that's intended */
 414         if (!isempty(cvtnr))
 415                 (void) safe_atou32(cvtnr, &vtnr);
 416
 417         if (!isempty(display) && !vtnr) {
 418                 if (isempty(seat))
 419                         get_seat_from_display(display, &seat, &vtnr);
 420                 else if (streq(seat, "seat0"))
 421                         get_seat_from_display(display, NULL, &vtnr);
 422         }
 423
 424         if (seat && !streq(seat, "seat0") && vtnr != 0) {
 425                 pam_syslog(handle, LOG_DEBUG, "Ignoring vtnr %"PRIu32" for %s which is not seat0", vtnr, seat);
 426                 vtnr = 0;
 427         }
 428
 429         if (isempty(type))
 430                 type = !isempty(display) ? "x11" :
 431                            !isempty(tty) ? "tty" : "unspecified";
 432
 433         if (isempty(class))
 434                 class = streq(type, "unspecified") ? "background" : "user";
 435
 436         remote = !isempty(remote_host) && !is_localhost(remote_host);
 437
 438         (void) pam_get_data(handle, "systemd.memory_max", (const void **)&memory_max);
 439         (void) pam_get_data(handle, "systemd.tasks_max",  (const void **)&tasks_max);
 440         (void) pam_get_data(handle, "systemd.cpu_weight", (const void **)&cpu_weight);
 441         (void) pam_get_data(handle, "systemd.io_weight",  (const void **)&io_weight);
 442
 443         /* Talk to logind over the message bus */
 444
 445         r = sd_bus_open_system(&bus);
 446         if (r < 0) {
 447                 pam_syslog(handle, LOG_ERR, "Failed to connect to system bus: %s", strerror(-r));
 448                 return PAM_SESSION_ERR;
 449         }
 450
 451         if (debug) {
 452                 pam_syslog(handle, LOG_DEBUG, "Asking logind to create session: "
 453                            "uid="UID_FMT" pid="PID_FMT" service=%s type=%s class=%s desktop=%s seat=%s vtnr=%"PRIu32" tty=%s display=%s remote=%s remote_user=%s remote_host=%s",
 454                            pw->pw_uid, getpid_cached(),
 455                            strempty(service),
 456                            type, class, strempty(desktop),
 457                            strempty(seat), vtnr, strempty(tty), strempty(display),
 458                            yes_no(remote), strempty(remote_user), strempty(remote_host));
 459                 pam_syslog(handle, LOG_DEBUG, "Session limits: "
 460                            "memory_max=%s tasks_max=%s cpu_weight=%s io_weight=%s",
 461                            strna(memory_max), strna(tasks_max), strna(cpu_weight), strna(io_weight));
 462         }
 463
 464         r = sd_bus_message_new_method_call(
 465                         bus,
 466                         &m,
 467                         "org.freedesktop.login1",
 468                         "/org/freedesktop/login1",
 469                         "org.freedesktop.login1.Manager",
 470                         "CreateSession");
 471         if (r < 0) {
 472                 pam_syslog(handle, LOG_ERR, "Failed to create CreateSession method call: %s", strerror(-r));
 473                 return PAM_SESSION_ERR;
 474         }
 475
 476         r = sd_bus_message_append(m, "uusssssussbss",
 477                         (uint32_t) pw->pw_uid,
 478                         (uint32_t) getpid_cached(),
 479                         service,
 480                         type,
 481                         class,
 482                         desktop,
 483                         seat,
 484                         vtnr,
 485                         tty,
 486                         display,
 487                         remote,
 488                         remote_user,
 489                         remote_host);
 490         if (r < 0) {
 491                 pam_syslog(handle, LOG_ERR, "Failed to append to bus message: %s", strerror(-r));
 492                 return PAM_SESSION_ERR;
 493         }
 494
 495         r = sd_bus_message_open_container(m, 'a', "(sv)");
 496         if (r < 0) {
 497                 pam_syslog(handle, LOG_ERR, "Failed to open message container: %s", strerror(-r));
 498                 return PAM_SYSTEM_ERR;
 499         }
 500
 501         r = append_session_memory_max(handle, m, memory_max);
 502         if (r < 0)
 503                 return PAM_SESSION_ERR;
 504
 505         r = append_session_tasks_max(handle, m, tasks_max);
 506         if (r < 0)
 507                 return PAM_SESSION_ERR;
 508
 509         r = append_session_cg_weight(handle, m, cpu_weight, "CPUWeight");
 510         if (r < 0)
 511                 return PAM_SESSION_ERR;
 512
 513         r = append_session_cg_weight(handle, m, io_weight, "IOWeight");
 514         if (r < 0)
 515                 return PAM_SESSION_ERR;
 516
 517         r = sd_bus_message_close_container(m);
 518         if (r < 0) {
 519                 pam_syslog(handle, LOG_ERR, "Failed to close message container: %s", strerror(-r));
 520                 return PAM_SYSTEM_ERR;
 521         }
 522
 523         r = sd_bus_call(bus, m, 0, &error, &reply);
 524         if (r < 0) {
 525                 if (sd_bus_error_has_name(&error, BUS_ERROR_SESSION_BUSY)) {
 526                         pam_syslog(handle, LOG_DEBUG, "Cannot create session: %s", bus_error_message(&error, r));
 527                         return PAM_SUCCESS;
 528                 } else {
 529                         pam_syslog(handle, LOG_ERR, "Failed to create session: %s", bus_error_message(&error, r));
 530                         return PAM_SYSTEM_ERR;
 531                 }
 532         }
 533
 534         r = sd_bus_message_read(reply,
 535                                 "soshusub",
 536                                 &id,
 537                                 &object_path,
 538                                 &runtime_path,
 539                                 &session_fd,
 540                                 &original_uid,
 541                                 &seat,
 542                                 &vtnr,
 543                                 &existing);
 544         if (r < 0) {
 545                 pam_syslog(handle, LOG_ERR, "Failed to parse message: %s", strerror(-r));
 546                 return PAM_SESSION_ERR;
 547         }
 548
 549         if (debug)
 550                 pam_syslog(handle, LOG_DEBUG, "Reply from logind: "
 551                            "id=%s object_path=%s runtime_path=%s session_fd=%d seat=%s vtnr=%u original_uid=%u",
 552                            id, object_path, runtime_path, session_fd, seat, vtnr, original_uid);
 553
 554         r = pam_misc_setenv(handle, "XDG_SESSION_ID", id, 0);
 555         if (r != PAM_SUCCESS) {
 556                 pam_syslog(handle, LOG_ERR, "Failed to set session id.");
 557                 return r;
 558         }
 559
 560         if (original_uid == pw->pw_uid) {
 561                 /* Don't set $XDG_RUNTIME_DIR if the user we now
 562                  * authenticated for does not match the original user
 563                  * of the session. We do this in order not to result
 564                  * in privileged apps clobbering the runtime directory
 565                  * unnecessarily. */
 566
 567                 r = pam_misc_setenv(handle, "XDG_RUNTIME_DIR", runtime_path, 0);
 568                 if (r != PAM_SUCCESS) {
 569                         pam_syslog(handle, LOG_ERR, "Failed to set runtime dir.");
 570                         return r;
 571                 }
 572
 573                 r = export_legacy_dbus_address(handle, pw->pw_uid, runtime_path);
 574                 if (r != PAM_SUCCESS)
 575                         return r;
 576         }
 577
 578         if (!isempty(seat)) {
 579                 r = pam_misc_setenv(handle, "XDG_SEAT", seat, 0);
 580                 if (r != PAM_SUCCESS) {
 581                         pam_syslog(handle, LOG_ERR, "Failed to set seat.");
 582                         return r;
 583                 }
 584         }
 585
 586         if (vtnr > 0) {
 587                 char buf[DECIMAL_STR_MAX(vtnr)];
 588                 sprintf(buf, "%u", vtnr);
 589
 590                 r = pam_misc_setenv(handle, "XDG_VTNR", buf, 0);
 591                 if (r != PAM_SUCCESS) {
 592                         pam_syslog(handle, LOG_ERR, "Failed to set virtual terminal number.");
 593                         return r;
 594                 }
 595         }
 596
 597         r = pam_set_data(handle, "systemd.existing", INT_TO_PTR(!!existing), NULL);
 598         if (r != PAM_SUCCESS) {
 599                 pam_syslog(handle, LOG_ERR, "Failed to install existing flag.");
 600                 return r;
 601         }
 602
 603         if (session_fd >= 0) {
 604                 session_fd = fcntl(session_fd, F_DUPFD_CLOEXEC, 3);
 605                 if (session_fd < 0) {
 606                         pam_syslog(handle, LOG_ERR, "Failed to dup session fd: %m");
 607                         return PAM_SESSION_ERR;
 608                 }
 609
 610                 r = pam_set_data(handle, "systemd.session-fd", FD_TO_PTR(session_fd), NULL);
 611                 if (r != PAM_SUCCESS) {
 612                         pam_syslog(handle, LOG_ERR, "Failed to install session fd.");
 613                         safe_close(session_fd);
 614                         return r;
 615                 }
 616         }
 617
 618         return PAM_SUCCESS;
 619 }
 620
 621 _public_ PAM_EXTERN int pam_sm_close_session(
 622                 pam_handle_t *handle,
 623                 int flags,
 624                 int argc, const char **argv) {
 625
 626         _cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
 627         _cleanup_(sd_bus_flush_close_unrefp) sd_bus *bus = NULL;
 628         const void *existing = NULL;
 629         const char *id;
 630         int r;
 631
 632         assert(handle);
 633
 634         /* Only release session if it wasn't pre-existing when we
 635          * tried to create it */
 636         pam_get_data(handle, "systemd.existing", &existing);
 637
 638         id = pam_getenv(handle, "XDG_SESSION_ID");
 639         if (id && !existing) {
 640
 641                 /* Before we go and close the FIFO we need to tell
 642                  * logind that this is a clean session shutdown, so
 643                  * that it doesn't just go and slaughter us
 644                  * immediately after closing the fd */
 645
 646                 r = sd_bus_open_system(&bus);
 647                 if (r < 0) {
 648                         pam_syslog(handle, LOG_ERR, "Failed to connect to system bus: %s", strerror(-r));
 649                         return PAM_SESSION_ERR;
 650                 }
 651
 652                 r = sd_bus_call_method(bus,
 653                                        "org.freedesktop.login1",
 654                                        "/org/freedesktop/login1",
 655                                        "org.freedesktop.login1.Manager",
 656                                        "ReleaseSession",
 657                                        &error,
 658                                        NULL,
 659                                        "s",
 660                                        id);
 661                 if (r < 0) {
 662                         pam_syslog(handle, LOG_ERR, "Failed to release session: %s", bus_error_message(&error, r));
 663                         return PAM_SESSION_ERR;
 664                 }
 665         }
 666
 667         /* Note that we are knowingly leaking the FIFO fd here. This
 668          * way, logind can watch us die. If we closed it here it would
 669          * not have any clue when that is completed. Given that one
 670          * cannot really have multiple PAM sessions open from the same
 671          * process this means we will leak one FD at max. */
 672
 673         return PAM_SUCCESS;
 674 }