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