src/login/pam_elogind.c

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