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 #include "path-util.h"
  50
  51 static int parse_argv(
  52                 pam_handle_t *handle,
  53                 int argc, const char **argv,
  54                 const char **class,
  55                 const char **type,
  56                 bool *debug) {
  57
  58         unsigned i;
  59
  60         assert(argc >= 0);
  61         assert(argc == 0 || argv);
  62
  63         for (i = 0; i < (unsigned) argc; i++) {
  64                 if (startswith(argv[i], "class=")) {
  65                         if (class)
  66                                 *class = argv[i] + 6;
  67
  68                 } else if (startswith(argv[i], "type=")) {
  69                         if (type)
  70                                 *type = argv[i] + 5;
  71
  72                 } else if (streq(argv[i], "debug")) {
  73                         if (debug)
  74                                 *debug = true;
  75
  76                 } else if (startswith(argv[i], "debug=")) {
  77                         int k;
  78
  79                         k = parse_boolean(argv[i] + 6);
  80                         if (k < 0)
  81                                 pam_syslog(handle, LOG_WARNING, "Failed to parse debug= argument, ignoring.");
  82                         else if (debug)
  83                                 *debug = k;
  84
  85                 } else
  86                         pam_syslog(handle, LOG_WARNING, "Unknown parameter '%s', ignoring", argv[i]);
  87         }
  88
  89         return 0;
  90 }
  91
  92 static int get_user_data(
  93                 pam_handle_t *handle,
  94                 const char **ret_username,
  95                 struct passwd **ret_pw) {
  96
  97         const char *username = NULL;
  98         struct passwd *pw = NULL;
  99         int r;
 100
 101         assert(handle);
 102         assert(ret_username);
 103         assert(ret_pw);
 104
 105         r = pam_get_user(handle, &username, NULL);
 106         if (r != PAM_SUCCESS) {
 107                 pam_syslog(handle, LOG_ERR, "Failed to get user name.");
 108                 return r;
 109         }
 110
 111         if (isempty(username)) {
 112                 pam_syslog(handle, LOG_ERR, "User name not valid.");
 113                 return PAM_AUTH_ERR;
 114         }
 115
 116         pw = pam_modutil_getpwnam(handle, username);
 117         if (!pw) {
 118                 pam_syslog(handle, LOG_ERR, "Failed to get user data.");
 119                 return PAM_USER_UNKNOWN;
 120         }
 121
 122         *ret_pw = pw;
 123         *ret_username = username;
 124
 125         return PAM_SUCCESS;
 126 }
 127
 128 static int get_seat_from_display(const char *display, const char **seat, uint32_t *vtnr) {
 129         union sockaddr_union sa = {
 130                 .un.sun_family = AF_UNIX,
 131         };
 132         _cleanup_free_ char *p = NULL, *tty = NULL;
 133         _cleanup_close_ int fd = -1;
 134         struct ucred ucred;
 135         int v, r;
 136
 137         assert(display);
 138         assert(vtnr);
 139
 140         /* We deduce the X11 socket from the display name, then use
 141          * SO_PEERCRED to determine the X11 server process, ask for
 142          * the controlling tty of that and if it's a VC then we know
 143          * the seat and the virtual terminal. Sounds ugly, is only
 144          * semi-ugly. */
 145
 146         r = socket_from_display(display, &p);
 147         if (r < 0)
 148                 return r;
 149         strncpy(sa.un.sun_path, p, sizeof(sa.un.sun_path)-1);
 150
 151         fd = socket(AF_UNIX, SOCK_STREAM|SOCK_CLOEXEC, 0);
 152         if (fd < 0)
 153                 return -errno;
 154
 155         if (connect(fd, &sa.sa, SOCKADDR_UN_LEN(sa.un)) < 0)
 156                 return -errno;
 157
 158         r = getpeercred(fd, &ucred);
 159         if (r < 0)
 160                 return r;
 161
 162         r = get_ctty(ucred.pid, NULL, &tty);
 163         if (r < 0)
 164                 return r;
 165
 166         v = vtnr_from_tty(tty);
 167         if (v < 0)
 168                 return v;
 169         else if (v == 0)
 170                 return -ENOENT;
 171
 172         if (seat)
 173                 *seat = "seat0";
 174         *vtnr = (uint32_t) v;
 175
 176         return 0;
 177 }
 178
 179 static int export_legacy_dbus_address(
 180                 pam_handle_t *handle,
 181                 uid_t uid,
 182                 const char *runtime) {
 183
 184         _cleanup_free_ char *s = NULL;
 185         int r = PAM_BUF_ERR;
 186
 187         /* FIXME: We *really* should move the access() check into the
 188          * daemons that spawn dbus-daemon, instead of forcing
 189          * DBUS_SESSION_BUS_ADDRESS= here. */
 190
 191         s = strjoin(runtime, "/bus");
 192         if (!s)
 193                 goto error;
 194
 195         if (access(s, F_OK) < 0)
 196                 return PAM_SUCCESS;
 197
 198         s = mfree(s);
 199         if (asprintf(&s, UNIX_USER_BUS_ADDRESS_FMT, runtime) < 0)
 200                 goto error;
 201
 202         r = pam_misc_setenv(handle, "DBUS_SESSION_BUS_ADDRESS", s, 0);
 203         if (r != PAM_SUCCESS)
 204                 goto error;
 205
 206         return PAM_SUCCESS;
 207
 208 error:
 209         pam_syslog(handle, LOG_ERR, "Failed to set bus variable.");
 210         return r;
 211 }
 212
 213 _public_ PAM_EXTERN int pam_sm_open_session(
 214                 pam_handle_t *handle,
 215                 int flags,
 216                 int argc, const char **argv) {
 217
 218         _cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
 219         _cleanup_(sd_bus_message_unrefp) sd_bus_message *reply = NULL;
 220         const char
 221                 *username, *id, *object_path, *runtime_path,
 222                 *service = NULL,
 223                 *tty = NULL, *display = NULL,
 224                 *remote_user = NULL, *remote_host = NULL,
 225                 *seat = NULL,
 226                 *type = NULL, *class = NULL,
 227                 *class_pam = NULL, *type_pam = NULL, *cvtnr = NULL, *desktop = NULL;
 228         _cleanup_(sd_bus_flush_close_unrefp) sd_bus *bus = NULL;
 229         int session_fd = -1, existing, r;
 230         bool debug = false, remote;
 231         struct passwd *pw;
 232         uint32_t vtnr = 0;
 233         uid_t original_uid;
 234
 235         assert(handle);
 236
 237         /* Make this a NOP on non-logind systems */
 238         if (!logind_running())
 239                 return PAM_SUCCESS;
 240
 241         if (parse_argv(handle,
 242                        argc, argv,
 243                        &class_pam,
 244                        &type_pam,
 245                        &debug) < 0)
 246                 return PAM_SESSION_ERR;
 247
 248         if (debug)
 249                 pam_syslog(handle, LOG_DEBUG, "pam-systemd initializing");
 250
 251         r = get_user_data(handle, &username, &pw);
 252         if (r != PAM_SUCCESS) {
 253                 pam_syslog(handle, LOG_ERR, "Failed to get user data.");
 254                 return r;
 255         }
 256
 257         /* Make sure we don't enter a loop by talking to
 258          * systemd-logind when it is actually waiting for the
 259          * background to finish start-up. If the service is
 260          * "systemd-user" we simply set XDG_RUNTIME_DIR and
 261          * leave. */
 262
 263         pam_get_item(handle, PAM_SERVICE, (const void**) &service);
 264         if (streq_ptr(service, "systemd-user")) {
 265                 _cleanup_free_ char *rt = NULL;
 266
 267                 if (asprintf(&rt, "/run/user/"UID_FMT, pw->pw_uid) < 0)
 268                         return PAM_BUF_ERR;
 269
 270                 r = pam_misc_setenv(handle, "XDG_RUNTIME_DIR", rt, 0);
 271                 if (r != PAM_SUCCESS) {
 272                         pam_syslog(handle, LOG_ERR, "Failed to set runtime dir.");
 273                         return r;
 274                 }
 275
 276                 r = export_legacy_dbus_address(handle, pw->pw_uid, rt);
 277                 if (r != PAM_SUCCESS)
 278                         return r;
 279
 280                 return PAM_SUCCESS;
 281         }
 282
 283         /* Otherwise, we ask logind to create a session for us */
 284
 285         pam_get_item(handle, PAM_XDISPLAY, (const void**) &display);
 286         pam_get_item(handle, PAM_TTY, (const void**) &tty);
 287         pam_get_item(handle, PAM_RUSER, (const void**) &remote_user);
 288         pam_get_item(handle, PAM_RHOST, (const void**) &remote_host);
 289
 290         seat = pam_getenv(handle, "XDG_SEAT");
 291         if (isempty(seat))
 292                 seat = getenv("XDG_SEAT");
 293
 294         cvtnr = pam_getenv(handle, "XDG_VTNR");
 295         if (isempty(cvtnr))
 296                 cvtnr = getenv("XDG_VTNR");
 297
 298         type = pam_getenv(handle, "XDG_SESSION_TYPE");
 299         if (isempty(type))
 300                 type = getenv("XDG_SESSION_TYPE");
 301         if (isempty(type))
 302                 type = type_pam;
 303
 304         class = pam_getenv(handle, "XDG_SESSION_CLASS");
 305         if (isempty(class))
 306                 class = getenv("XDG_SESSION_CLASS");
 307         if (isempty(class))
 308                 class = class_pam;
 309
 310         desktop = pam_getenv(handle, "XDG_SESSION_DESKTOP");
 311         if (isempty(desktop))
 312                 desktop = getenv("XDG_SESSION_DESKTOP");
 313
 314         tty = strempty(tty);
 315
 316         if (strchr(tty, ':')) {
 317                 /* A tty with a colon is usually an X11 display,
 318                  * placed there to show up in utmp. We rearrange
 319                  * things and don't pretend that an X display was a
 320                  * tty. */
 321
 322                 if (isempty(display))
 323                         display = tty;
 324                 tty = NULL;
 325         } else if (streq(tty, "cron")) {
 326                 /* cron has been setting PAM_TTY to "cron" for a very
 327                  * long time and it probably shouldn't stop doing that
 328                  * for compatibility reasons. */
 329                 type = "unspecified";
 330                 class = "background";
 331                 tty = NULL;
 332         } else if (streq(tty, "ssh")) {
 333                 /* ssh has been setting PAM_TTY to "ssh" for a very
 334                  * long time and probably shouldn't stop doing that
 335                  * for compatibility reasons. */
 336                 type ="tty";
 337                 class = "user";
 338                 tty = NULL;
 339         } else
 340                 /* Chop off leading /dev prefix that some clients specify, but others do not. */
 341                 tty = skip_dev_prefix(tty);
 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_cached(),
 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_cached(),
 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 }