src/login/pam_systemd.c

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