src/login/pam_elogind.c

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