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