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         if (is_kdbus_available()) {
 186                 if (asprintf(&s, KERNEL_USER_BUS_ADDRESS_FMT ";" UNIX_USER_BUS_ADDRESS_FMT, uid, runtime) < 0)
 187                         goto error;
 188         } else {
 189                 /* FIXME: We *really* should move the access() check into the
 190                  * daemons that spawn dbus-daemon, instead of forcing
 191                  * DBUS_SESSION_BUS_ADDRESS= here. */
 192
 193                 s = strjoin(runtime, "/bus", NULL);
 194                 if (!s)
 195                         goto error;
 196
 197                 if (access(s, F_OK) < 0)
 198                         return PAM_SUCCESS;
 199
 200                 s = mfree(s);
 201                 if (asprintf(&s, UNIX_USER_BUS_ADDRESS_FMT, runtime) < 0)
 202                         goto error;
 203         }
 204
 205         r = pam_misc_setenv(handle, "DBUS_SESSION_BUS_ADDRESS", s, 0);
 206         if (r != PAM_SUCCESS)
 207                 goto error;
 208
 209         return PAM_SUCCESS;
 210
 211 error:
 212         pam_syslog(handle, LOG_ERR, "Failed to set bus variable.");
 213         return r;
 214 }
 215
 216 _public_ PAM_EXTERN int pam_sm_open_session(
 217                 pam_handle_t *handle,
 218                 int flags,
 219                 int argc, const char **argv) {
 220
 221         _cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
 222         _cleanup_(sd_bus_message_unrefp) sd_bus_message *reply = NULL;
 223         const char
 224                 *username, *id, *object_path, *runtime_path,
 225                 *service = NULL,
 226                 *tty = NULL, *display = NULL,
 227                 *remote_user = NULL, *remote_host = NULL,
 228                 *seat = NULL,
 229                 *type = NULL, *class = NULL,
 230                 *class_pam = NULL, *type_pam = NULL, *cvtnr = NULL, *desktop = NULL;
 231         _cleanup_(sd_bus_flush_close_unrefp) sd_bus *bus = NULL;
 232         int session_fd = -1, existing, r;
 233         bool debug = false, remote;
 234         struct passwd *pw;
 235         uint32_t vtnr = 0;
 236         uid_t original_uid;
 237
 238         assert(handle);
 239
 240         /* Make this a NOP on non-logind systems */
 241         if (!logind_running())
 242                 return PAM_SUCCESS;
 243
 244         if (parse_argv(handle,
 245                        argc, argv,
 246                        &class_pam,
 247                        &type_pam,
 248                        &debug) < 0)
 249                 return PAM_SESSION_ERR;
 250
 251         if (debug)
 252                 pam_syslog(handle, LOG_DEBUG, "pam-systemd initializing");
 253
 254         r = get_user_data(handle, &username, &pw);
 255         if (r != PAM_SUCCESS) {
 256                 pam_syslog(handle, LOG_ERR, "Failed to get user data.");
 257                 return r;
 258         }
 259
 260         /* Make sure we don't enter a loop by talking to
 261          * systemd-logind when it is actually waiting for the
 262          * background to finish start-up. If the service is
 263          * "systemd-user" we simply set XDG_RUNTIME_DIR and
 264          * leave. */
 265
 266         pam_get_item(handle, PAM_SERVICE, (const void**) &service);
 267         if (streq_ptr(service, "systemd-user")) {
 268                 _cleanup_free_ char *rt = NULL;
 269
 270                 if (asprintf(&rt, "/run/user/"UID_FMT, pw->pw_uid) < 0)
 271                         return PAM_BUF_ERR;
 272
 273                 r = pam_misc_setenv(handle, "XDG_RUNTIME_DIR", rt, 0);
 274                 if (r != PAM_SUCCESS) {
 275                         pam_syslog(handle, LOG_ERR, "Failed to set runtime dir.");
 276                         return r;
 277                 }
 278
 279                 r = export_legacy_dbus_address(handle, pw->pw_uid, rt);
 280                 if (r != PAM_SUCCESS)
 281                         return r;
 282
 283                 return PAM_SUCCESS;
 284         }
 285
 286         /* Otherwise, we ask logind to create a session for us */
 287
 288         pam_get_item(handle, PAM_XDISPLAY, (const void**) &display);
 289         pam_get_item(handle, PAM_TTY, (const void**) &tty);
 290         pam_get_item(handle, PAM_RUSER, (const void**) &remote_user);
 291         pam_get_item(handle, PAM_RHOST, (const void**) &remote_host);
 292
 293         seat = pam_getenv(handle, "XDG_SEAT");
 294         if (isempty(seat))
 295                 seat = getenv("XDG_SEAT");
 296
 297         cvtnr = pam_getenv(handle, "XDG_VTNR");
 298         if (isempty(cvtnr))
 299                 cvtnr = getenv("XDG_VTNR");
 300
 301         type = pam_getenv(handle, "XDG_SESSION_TYPE");
 302         if (isempty(type))
 303                 type = getenv("XDG_SESSION_TYPE");
 304         if (isempty(type))
 305                 type = type_pam;
 306
 307         class = pam_getenv(handle, "XDG_SESSION_CLASS");
 308         if (isempty(class))
 309                 class = getenv("XDG_SESSION_CLASS");
 310         if (isempty(class))
 311                 class = class_pam;
 312
 313         desktop = pam_getenv(handle, "XDG_SESSION_DESKTOP");
 314         if (isempty(desktop))
 315                 desktop = getenv("XDG_SESSION_DESKTOP");
 316
 317         tty = strempty(tty);
 318
 319         if (strchr(tty, ':')) {
 320                 /* A tty with a colon is usually an X11 display,
 321                  * placed there to show up in utmp. We rearrange
 322                  * things and don't pretend that an X display was a
 323                  * tty. */
 324
 325                 if (isempty(display))
 326                         display = tty;
 327                 tty = NULL;
 328         } else if (streq(tty, "cron")) {
 329                 /* cron has been setting PAM_TTY to "cron" for a very
 330                  * long time and it probably shouldn't stop doing that
 331                  * for compatibility reasons. */
 332                 type = "unspecified";
 333                 class = "background";
 334                 tty = NULL;
 335         } else if (streq(tty, "ssh")) {
 336                 /* ssh has been setting PAM_TTY to "ssh" for a very
 337                  * long time and probably shouldn't stop doing that
 338                  * for compatibility reasons. */
 339                 type ="tty";
 340                 class = "user";
 341                 tty = NULL;
 342         }
 343
 344         /* If this fails vtnr will be 0, that's intended */
 345         if (!isempty(cvtnr))
 346                 (void) safe_atou32(cvtnr, &vtnr);
 347
 348         if (!isempty(display) && !vtnr) {
 349                 if (isempty(seat))
 350                         get_seat_from_display(display, &seat, &vtnr);
 351                 else if (streq(seat, "seat0"))
 352                         get_seat_from_display(display, NULL, &vtnr);
 353         }
 354
 355         if (seat && !streq(seat, "seat0") && vtnr != 0) {
 356                 pam_syslog(handle, LOG_DEBUG, "Ignoring vtnr %"PRIu32" for %s which is not seat0", vtnr, seat);
 357                 vtnr = 0;
 358         }
 359
 360         if (isempty(type))
 361                 type = !isempty(display) ? "x11" :
 362                            !isempty(tty) ? "tty" : "unspecified";
 363
 364         if (isempty(class))
 365                 class = streq(type, "unspecified") ? "background" : "user";
 366
 367         remote = !isempty(remote_host) && !is_localhost(remote_host);
 368
 369         /* Talk to logind over the message bus */
 370
 371         r = sd_bus_open_system(&bus);
 372         if (r < 0) {
 373                 pam_syslog(handle, LOG_ERR, "Failed to connect to system bus: %s", strerror(-r));
 374                 return PAM_SESSION_ERR;
 375         }
 376
 377         if (debug)
 378                 pam_syslog(handle, LOG_DEBUG, "Asking logind to create session: "
 379                            "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",
 380                            pw->pw_uid, getpid(),
 381                            strempty(service),
 382                            type, class, strempty(desktop),
 383                            strempty(seat), vtnr, strempty(tty), strempty(display),
 384                            yes_no(remote), strempty(remote_user), strempty(remote_host));
 385
 386         r = sd_bus_call_method(bus,
 387                                "org.freedesktop.login1",
 388                                "/org/freedesktop/login1",
 389                                "org.freedesktop.login1.Manager",
 390                                "CreateSession",
 391                                &error,
 392                                &reply,
 393                                "uusssssussbssa(sv)",
 394                                (uint32_t) pw->pw_uid,
 395                                (uint32_t) getpid(),
 396                                service,
 397                                type,
 398                                class,
 399                                desktop,
 400                                seat,
 401                                vtnr,
 402                                tty,
 403                                display,
 404                                remote,
 405                                remote_user,
 406                                remote_host,
 407                                0);
 408         if (r < 0) {
 409                 if (sd_bus_error_has_name(&error, BUS_ERROR_SESSION_BUSY)) {
 410                         pam_syslog(handle, LOG_DEBUG, "Cannot create session: %s", bus_error_message(&error, r));
 411                         return PAM_SUCCESS;
 412                 } else {
 413                         pam_syslog(handle, LOG_ERR, "Failed to create session: %s", bus_error_message(&error, r));
 414                         return PAM_SYSTEM_ERR;
 415                 }
 416         }
 417
 418         r = sd_bus_message_read(reply,
 419                                 "soshusub",
 420                                 &id,
 421                                 &object_path,
 422                                 &runtime_path,
 423                                 &session_fd,
 424                                 &original_uid,
 425                                 &seat,
 426                                 &vtnr,
 427                                 &existing);
 428         if (r < 0) {
 429                 pam_syslog(handle, LOG_ERR, "Failed to parse message: %s", strerror(-r));
 430                 return PAM_SESSION_ERR;
 431         }
 432
 433         if (debug)
 434                 pam_syslog(handle, LOG_DEBUG, "Reply from logind: "
 435                            "id=%s object_path=%s runtime_path=%s session_fd=%d seat=%s vtnr=%u original_uid=%u",
 436                            id, object_path, runtime_path, session_fd, seat, vtnr, original_uid);
 437
 438         r = pam_misc_setenv(handle, "XDG_SESSION_ID", id, 0);
 439         if (r != PAM_SUCCESS) {
 440                 pam_syslog(handle, LOG_ERR, "Failed to set session id.");
 441                 return r;
 442         }
 443
 444         if (original_uid == pw->pw_uid) {
 445                 /* Don't set $XDG_RUNTIME_DIR if the user we now
 446                  * authenticated for does not match the original user
 447                  * of the session. We do this in order not to result
 448                  * in privileged apps clobbering the runtime directory
 449                  * unnecessarily. */
 450
 451                 r = pam_misc_setenv(handle, "XDG_RUNTIME_DIR", runtime_path, 0);
 452                 if (r != PAM_SUCCESS) {
 453                         pam_syslog(handle, LOG_ERR, "Failed to set runtime dir.");
 454                         return r;
 455                 }
 456
 457                 r = export_legacy_dbus_address(handle, pw->pw_uid, runtime_path);
 458                 if (r != PAM_SUCCESS)
 459                         return r;
 460         }
 461
 462         if (!isempty(seat)) {
 463                 r = pam_misc_setenv(handle, "XDG_SEAT", seat, 0);
 464                 if (r != PAM_SUCCESS) {
 465                         pam_syslog(handle, LOG_ERR, "Failed to set seat.");
 466                         return r;
 467                 }
 468         }
 469
 470         if (vtnr > 0) {
 471                 char buf[DECIMAL_STR_MAX(vtnr)];
 472                 sprintf(buf, "%u", vtnr);
 473
 474                 r = pam_misc_setenv(handle, "XDG_VTNR", buf, 0);
 475                 if (r != PAM_SUCCESS) {
 476                         pam_syslog(handle, LOG_ERR, "Failed to set virtual terminal number.");
 477                         return r;
 478                 }
 479         }
 480
 481         r = pam_set_data(handle, "systemd.existing", INT_TO_PTR(!!existing), NULL);
 482         if (r != PAM_SUCCESS) {
 483                 pam_syslog(handle, LOG_ERR, "Failed to install existing flag.");
 484                 return r;
 485         }
 486
 487         if (session_fd >= 0) {
 488                 session_fd = fcntl(session_fd, F_DUPFD_CLOEXEC, 3);
 489                 if (session_fd < 0) {
 490                         pam_syslog(handle, LOG_ERR, "Failed to dup session fd: %m");
 491                         return PAM_SESSION_ERR;
 492                 }
 493
 494                 r = pam_set_data(handle, "systemd.session-fd", FD_TO_PTR(session_fd), NULL);
 495                 if (r != PAM_SUCCESS) {
 496                         pam_syslog(handle, LOG_ERR, "Failed to install session fd.");
 497                         safe_close(session_fd);
 498                         return r;
 499                 }
 500         }
 501
 502         return PAM_SUCCESS;
 503 }
 504
 505 _public_ PAM_EXTERN int pam_sm_close_session(
 506                 pam_handle_t *handle,
 507                 int flags,
 508                 int argc, const char **argv) {
 509
 510         _cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
 511         _cleanup_(sd_bus_flush_close_unrefp) sd_bus *bus = NULL;
 512         const void *existing = NULL;
 513         const char *id;
 514         int r;
 515
 516         assert(handle);
 517
 518         /* Only release session if it wasn't pre-existing when we
 519          * tried to create it */
 520         pam_get_data(handle, "systemd.existing", &existing);
 521
 522         id = pam_getenv(handle, "XDG_SESSION_ID");
 523         if (id && !existing) {
 524
 525                 /* Before we go and close the FIFO we need to tell
 526                  * logind that this is a clean session shutdown, so
 527                  * that it doesn't just go and slaughter us
 528                  * immediately after closing the fd */
 529
 530                 r = sd_bus_open_system(&bus);
 531                 if (r < 0) {
 532                         pam_syslog(handle, LOG_ERR, "Failed to connect to system bus: %s", strerror(-r));
 533                         return PAM_SESSION_ERR;
 534                 }
 535
 536                 r = sd_bus_call_method(bus,
 537                                        "org.freedesktop.login1",
 538                                        "/org/freedesktop/login1",
 539                                        "org.freedesktop.login1.Manager",
 540                                        "ReleaseSession",
 541                                        &error,
 542                                        NULL,
 543                                        "s",
 544                                        id);
 545                 if (r < 0) {
 546                         pam_syslog(handle, LOG_ERR, "Failed to release session: %s", bus_error_message(&error, r));
 547                         return PAM_SESSION_ERR;
 548                 }
 549         }
 550
 551         /* Note that we are knowingly leaking the FIFO fd here. This
 552          * way, logind can watch us die. If we closed it here it would
 553          * not have any clue when that is completed. Given that one
 554          * cannot really have multiple PAM sessions open from the same
 555          * process this means we will leak one FD at max. */
 556
 557         return PAM_SUCCESS;
 558 }