src/login/pam_systemd.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 "formats-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", NULL);
 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                 pam_syslog(handle, LOG_DEBUG, "pam-systemd initializing");
 248
 249         r = get_user_data(handle, &username, &pw);
 250         if (r != PAM_SUCCESS) {
 251                 pam_syslog(handle, LOG_ERR, "Failed to get user data.");
 252                 return r;
 253         }
 254
 255         /* Make sure we don't enter a loop by talking to
 256          * systemd-logind when it is actually waiting for the
 257          * background to finish start-up. If the service is
 258          * "systemd-user" we simply set XDG_RUNTIME_DIR and
 259          * leave. */
 260
 261         pam_get_item(handle, PAM_SERVICE, (const void**) &service);
 262         if (streq_ptr(service, "systemd-user")) {
 263                 _cleanup_free_ char *rt = NULL;
 264
 265                 if (asprintf(&rt, "/run/user/"UID_FMT, pw->pw_uid) < 0)
 266                         return PAM_BUF_ERR;
 267
 268                 r = pam_misc_setenv(handle, "XDG_RUNTIME_DIR", rt, 0);
 269                 if (r != PAM_SUCCESS) {
 270                         pam_syslog(handle, LOG_ERR, "Failed to set runtime dir.");
 271                         return r;
 272                 }
 273
 274                 r = export_legacy_dbus_address(handle, pw->pw_uid, rt);
 275                 if (r != PAM_SUCCESS)
 276                         return r;
 277
 278                 return PAM_SUCCESS;
 279         }
 280
 281         /* Otherwise, we ask logind to create a session for us */
 282
 283         pam_get_item(handle, PAM_XDISPLAY, (const void**) &display);
 284         pam_get_item(handle, PAM_TTY, (const void**) &tty);
 285         pam_get_item(handle, PAM_RUSER, (const void**) &remote_user);
 286         pam_get_item(handle, PAM_RHOST, (const void**) &remote_host);
 287
 288         seat = pam_getenv(handle, "XDG_SEAT");
 289         if (isempty(seat))
 290                 seat = getenv("XDG_SEAT");
 291
 292         cvtnr = pam_getenv(handle, "XDG_VTNR");
 293         if (isempty(cvtnr))
 294                 cvtnr = getenv("XDG_VTNR");
 295
 296         type = pam_getenv(handle, "XDG_SESSION_TYPE");
 297         if (isempty(type))
 298                 type = getenv("XDG_SESSION_TYPE");
 299         if (isempty(type))
 300                 type = type_pam;
 301
 302         class = pam_getenv(handle, "XDG_SESSION_CLASS");
 303         if (isempty(class))
 304                 class = getenv("XDG_SESSION_CLASS");
 305         if (isempty(class))
 306                 class = class_pam;
 307
 308         desktop = pam_getenv(handle, "XDG_SESSION_DESKTOP");
 309         if (isempty(desktop))
 310                 desktop = getenv("XDG_SESSION_DESKTOP");
 311
 312         tty = strempty(tty);
 313
 314         if (strchr(tty, ':')) {
 315                 /* A tty with a colon is usually an X11 display,
 316                  * placed there to show up in utmp. We rearrange
 317                  * things and don't pretend that an X display was a
 318                  * tty. */
 319
 320                 if (isempty(display))
 321                         display = tty;
 322                 tty = NULL;
 323         } else if (streq(tty, "cron")) {
 324                 /* cron has been setting PAM_TTY to "cron" for a very
 325                  * long time and it probably shouldn't stop doing that
 326                  * for compatibility reasons. */
 327                 type = "unspecified";
 328                 class = "background";
 329                 tty = NULL;
 330         } else if (streq(tty, "ssh")) {
 331                 /* ssh has been setting PAM_TTY to "ssh" for a very
 332                  * long time and probably shouldn't stop doing that
 333                  * for compatibility reasons. */
 334                 type ="tty";
 335                 class = "user";
 336                 tty = NULL;
 337         }
 338
 339         /* If this fails vtnr will be 0, that's intended */
 340         if (!isempty(cvtnr))
 341                 (void) safe_atou32(cvtnr, &vtnr);
 342
 343         if (!isempty(display) && !vtnr) {
 344                 if (isempty(seat))
 345                         get_seat_from_display(display, &seat, &vtnr);
 346                 else if (streq(seat, "seat0"))
 347                         get_seat_from_display(display, NULL, &vtnr);
 348         }
 349
 350         if (seat && !streq(seat, "seat0") && vtnr != 0) {
 351                 pam_syslog(handle, LOG_DEBUG, "Ignoring vtnr %"PRIu32" for %s which is not seat0", vtnr, seat);
 352                 vtnr = 0;
 353         }
 354
 355         if (isempty(type))
 356                 type = !isempty(display) ? "x11" :
 357                            !isempty(tty) ? "tty" : "unspecified";
 358
 359         if (isempty(class))
 360                 class = streq(type, "unspecified") ? "background" : "user";
 361
 362         remote = !isempty(remote_host) && !is_localhost(remote_host);
 363
 364         /* Talk to logind over the message bus */
 365
 366         r = sd_bus_open_system(&bus);
 367         if (r < 0) {
 368                 pam_syslog(handle, LOG_ERR, "Failed to connect to system bus: %s", strerror(-r));
 369                 return PAM_SESSION_ERR;
 370         }
 371
 372         if (debug)
 373                 pam_syslog(handle, LOG_DEBUG, "Asking logind to create session: "
 374                            "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",
 375                            pw->pw_uid, getpid(),
 376                            strempty(service),
 377                            type, class, strempty(desktop),
 378                            strempty(seat), vtnr, strempty(tty), strempty(display),
 379                            yes_no(remote), strempty(remote_user), strempty(remote_host));
 380
 381         r = sd_bus_call_method(bus,
 382                                "org.freedesktop.login1",
 383                                "/org/freedesktop/login1",
 384                                "org.freedesktop.login1.Manager",
 385                                "CreateSession",
 386                                &error,
 387                                &reply,
 388                                "uusssssussbssa(sv)",
 389                                (uint32_t) pw->pw_uid,
 390                                (uint32_t) getpid(),
 391                                service,
 392                                type,
 393                                class,
 394                                desktop,
 395                                seat,
 396                                vtnr,
 397                                tty,
 398                                display,
 399                                remote,
 400                                remote_user,
 401                                remote_host,
 402                                0);
 403         if (r < 0) {
 404                 if (sd_bus_error_has_name(&error, BUS_ERROR_SESSION_BUSY)) {
 405                         pam_syslog(handle, LOG_DEBUG, "Cannot create session: %s", bus_error_message(&error, r));
 406                         return PAM_SUCCESS;
 407                 } else {
 408                         pam_syslog(handle, LOG_ERR, "Failed to create session: %s", bus_error_message(&error, r));
 409                         return PAM_SYSTEM_ERR;
 410                 }
 411         }
 412
 413         r = sd_bus_message_read(reply,
 414                                 "soshusub",
 415                                 &id,
 416                                 &object_path,
 417                                 &runtime_path,
 418                                 &session_fd,
 419                                 &original_uid,
 420                                 &seat,
 421                                 &vtnr,
 422                                 &existing);
 423         if (r < 0) {
 424                 pam_syslog(handle, LOG_ERR, "Failed to parse message: %s", strerror(-r));
 425                 return PAM_SESSION_ERR;
 426         }
 427
 428         if (debug)
 429                 pam_syslog(handle, LOG_DEBUG, "Reply from logind: "
 430                            "id=%s object_path=%s runtime_path=%s session_fd=%d seat=%s vtnr=%u original_uid=%u",
 431                            id, object_path, runtime_path, session_fd, seat, vtnr, original_uid);
 432
 433         r = pam_misc_setenv(handle, "XDG_SESSION_ID", id, 0);
 434         if (r != PAM_SUCCESS) {
 435                 pam_syslog(handle, LOG_ERR, "Failed to set session id.");
 436                 return r;
 437         }
 438
 439         if (original_uid == pw->pw_uid) {
 440                 /* Don't set $XDG_RUNTIME_DIR if the user we now
 441                  * authenticated for does not match the original user
 442                  * of the session. We do this in order not to result
 443                  * in privileged apps clobbering the runtime directory
 444                  * unnecessarily. */
 445
 446                 r = pam_misc_setenv(handle, "XDG_RUNTIME_DIR", runtime_path, 0);
 447                 if (r != PAM_SUCCESS) {
 448                         pam_syslog(handle, LOG_ERR, "Failed to set runtime dir.");
 449                         return r;
 450                 }
 451
 452                 r = export_legacy_dbus_address(handle, pw->pw_uid, runtime_path);
 453                 if (r != PAM_SUCCESS)
 454                         return r;
 455         }
 456
 457         if (!isempty(seat)) {
 458                 r = pam_misc_setenv(handle, "XDG_SEAT", seat, 0);
 459                 if (r != PAM_SUCCESS) {
 460                         pam_syslog(handle, LOG_ERR, "Failed to set seat.");
 461                         return r;
 462                 }
 463         }
 464
 465         if (vtnr > 0) {
 466                 char buf[DECIMAL_STR_MAX(vtnr)];
 467                 sprintf(buf, "%u", vtnr);
 468
 469                 r = pam_misc_setenv(handle, "XDG_VTNR", buf, 0);
 470                 if (r != PAM_SUCCESS) {
 471                         pam_syslog(handle, LOG_ERR, "Failed to set virtual terminal number.");
 472                         return r;
 473                 }
 474         }
 475
 476         r = pam_set_data(handle, "systemd.existing", INT_TO_PTR(!!existing), NULL);
 477         if (r != PAM_SUCCESS) {
 478                 pam_syslog(handle, LOG_ERR, "Failed to install existing flag.");
 479                 return r;
 480         }
 481
 482         if (session_fd >= 0) {
 483                 session_fd = fcntl(session_fd, F_DUPFD_CLOEXEC, 3);
 484                 if (session_fd < 0) {
 485                         pam_syslog(handle, LOG_ERR, "Failed to dup session fd: %m");
 486                         return PAM_SESSION_ERR;
 487                 }
 488
 489                 r = pam_set_data(handle, "systemd.session-fd", FD_TO_PTR(session_fd), NULL);
 490                 if (r != PAM_SUCCESS) {
 491                         pam_syslog(handle, LOG_ERR, "Failed to install session fd.");
 492                         safe_close(session_fd);
 493                         return r;
 494                 }
 495         }
 496
 497         return PAM_SUCCESS;
 498 }
 499
 500 _public_ PAM_EXTERN int pam_sm_close_session(
 501                 pam_handle_t *handle,
 502                 int flags,
 503                 int argc, const char **argv) {
 504
 505         _cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
 506         _cleanup_(sd_bus_flush_close_unrefp) sd_bus *bus = NULL;
 507         const void *existing = NULL;
 508         const char *id;
 509         int r;
 510
 511         assert(handle);
 512
 513         /* Only release session if it wasn't pre-existing when we
 514          * tried to create it */
 515         pam_get_data(handle, "systemd.existing", &existing);
 516
 517         id = pam_getenv(handle, "XDG_SESSION_ID");
 518         if (id && !existing) {
 519
 520                 /* Before we go and close the FIFO we need to tell
 521                  * logind that this is a clean session shutdown, so
 522                  * that it doesn't just go and slaughter us
 523                  * immediately after closing the fd */
 524
 525                 r = sd_bus_open_system(&bus);
 526                 if (r < 0) {
 527                         pam_syslog(handle, LOG_ERR, "Failed to connect to system bus: %s", strerror(-r));
 528                         return PAM_SESSION_ERR;
 529                 }
 530
 531                 r = sd_bus_call_method(bus,
 532                                        "org.freedesktop.login1",
 533                                        "/org/freedesktop/login1",
 534                                        "org.freedesktop.login1.Manager",
 535                                        "ReleaseSession",
 536                                        &error,
 537                                        NULL,
 538                                        "s",
 539                                        id);
 540                 if (r < 0) {
 541                         pam_syslog(handle, LOG_ERR, "Failed to release session: %s", bus_error_message(&error, r));
 542                         return PAM_SESSION_ERR;
 543                 }
 544         }
 545
 546         /* Note that we are knowingly leaking the FIFO fd here. This
 547          * way, logind can watch us die. If we closed it here it would
 548          * not have any clue when that is completed. Given that one
 549          * cannot really have multiple PAM sessions open from the same
 550          * process this means we will leak one FD at max. */
 551
 552         return PAM_SUCCESS;
 553 }