src/login/logind-seat.c

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2
   3 #include <errno.h>
   4 #include <fcntl.h>
   5 #include <string.h>
   6 #include <sys/stat.h>
   7 #include <unistd.h>
   8
   9 #include "sd-messages.h"
  10
  11 #include "alloc-util.h"
  12 #include "fd-util.h"
  13 #include "fileio.h"
  14 #include "format-util.h"
  15 #include "logind-acl.h"
  16 #include "logind-seat.h"
  17 #include "mkdir.h"
  18 #include "parse-util.h"
  19 #include "stdio-util.h"
  20 #include "string-util.h"
  21 #include "terminal-util.h"
  22 #include "tmpfile-util.h"
  23 #include "util.h"
  24
  25 int seat_new(Seat** ret, Manager *m, const char *id) {
  26         _cleanup_(seat_freep) Seat *s = NULL;
  27         int r;
  28
  29         assert(ret);
  30         assert(m);
  31         assert(id);
  32
  33         if (!seat_name_is_valid(id))
  34                 return -EINVAL;
  35
  36         s = new(Seat, 1);
  37         if (!s)
  38                 return -ENOMEM;
  39
  40         *s = (Seat) {
  41                 .manager = m,
  42         };
  43
  44         s->state_file = strappend("/run/systemd/seats/", id);
  45         if (!s->state_file)
  46                 return -ENOMEM;
  47
  48         s->id = basename(s->state_file);
  49
  50         r = hashmap_put(m->seats, s->id, s);
  51         if (r < 0)
  52                 return r;
  53
  54         *ret = TAKE_PTR(s);
  55         return 0;
  56 }
  57
  58 Seat* seat_free(Seat *s) {
  59         if (!s)
  60                 return NULL;
  61
  62         if (s->in_gc_queue)
  63                 LIST_REMOVE(gc_queue, s->manager->seat_gc_queue, s);
  64
  65         while (s->sessions)
  66                 session_free(s->sessions);
  67
  68         assert(!s->active);
  69
  70         while (s->devices)
  71                 device_free(s->devices);
  72
  73         hashmap_remove(s->manager->seats, s->id);
  74
  75         free(s->positions);
  76         free(s->state_file);
  77
  78         return mfree(s);
  79 }
  80
  81 int seat_save(Seat *s) {
  82         _cleanup_free_ char *temp_path = NULL;
  83         _cleanup_fclose_ FILE *f = NULL;
  84         int r;
  85
  86         assert(s);
  87
  88         if (!s->started)
  89                 return 0;
  90
  91         r = mkdir_safe_label("/run/systemd/seats", 0755, 0, 0, MKDIR_WARN_MODE);
  92         if (r < 0)
  93                 goto fail;
  94
  95         r = fopen_temporary(s->state_file, &f, &temp_path);
  96         if (r < 0)
  97                 goto fail;
  98
  99         (void) fchmod(fileno(f), 0644);
 100
 101         fprintf(f,
 102                 "# This is private data. Do not parse.\n"
 103                 "IS_SEAT0=%i\n"
 104                 "CAN_MULTI_SESSION=%i\n"
 105                 "CAN_TTY=%i\n"
 106                 "CAN_GRAPHICAL=%i\n",
 107                 seat_is_seat0(s),
 108                 seat_can_multi_session(s),
 109                 seat_can_tty(s),
 110                 seat_can_graphical(s));
 111
 112         if (s->active) {
 113                 assert(s->active->user);
 114
 115                 fprintf(f,
 116                         "ACTIVE=%s\n"
 117                         "ACTIVE_UID="UID_FMT"\n",
 118                         s->active->id,
 119                         s->active->user->uid);
 120         }
 121
 122         if (s->sessions) {
 123                 Session *i;
 124
 125                 fputs("SESSIONS=", f);
 126                 LIST_FOREACH(sessions_by_seat, i, s->sessions) {
 127                         fprintf(f,
 128                                 "%s%c",
 129                                 i->id,
 130                                 i->sessions_by_seat_next ? ' ' : '\n');
 131                 }
 132
 133                 fputs("UIDS=", f);
 134                 LIST_FOREACH(sessions_by_seat, i, s->sessions)
 135                         fprintf(f,
 136                                 UID_FMT"%c",
 137                                 i->user->uid,
 138                                 i->sessions_by_seat_next ? ' ' : '\n');
 139         }
 140
 141         r = fflush_and_check(f);
 142         if (r < 0)
 143                 goto fail;
 144
 145         if (rename(temp_path, s->state_file) < 0) {
 146                 r = -errno;
 147                 goto fail;
 148         }
 149
 150         return 0;
 151
 152 fail:
 153         (void) unlink(s->state_file);
 154
 155         if (temp_path)
 156                 (void) unlink(temp_path);
 157
 158         return log_error_errno(r, "Failed to save seat data %s: %m", s->state_file);
 159 }
 160
 161 int seat_load(Seat *s) {
 162         assert(s);
 163
 164         /* There isn't actually anything to read here ... */
 165
 166         return 0;
 167 }
 168
 169 static int vt_allocate(unsigned vtnr) {
 170         char p[sizeof("/dev/tty") + DECIMAL_STR_MAX(unsigned)];
 171         _cleanup_close_ int fd = -1;
 172
 173         assert(vtnr >= 1);
 174
 175         xsprintf(p, "/dev/tty%u", vtnr);
 176         fd = open_terminal(p, O_RDWR|O_NOCTTY|O_CLOEXEC);
 177         if (fd < 0)
 178                 return fd;
 179
 180         return 0;
 181 }
 182
 183 int seat_preallocate_vts(Seat *s) {
 184         int r = 0;
 185         unsigned i;
 186
 187         assert(s);
 188         assert(s->manager);
 189
 190         log_debug("Preallocating VTs...");
 191
 192         if (s->manager->n_autovts <= 0)
 193                 return 0;
 194
 195         if (!seat_has_vts(s))
 196                 return 0;
 197
 198         for (i = 1; i <= s->manager->n_autovts; i++) {
 199                 int q;
 200
 201                 q = vt_allocate(i);
 202                 if (q < 0)
 203                         r = log_error_errno(q, "Failed to preallocate VT %u: %m", i);
 204         }
 205
 206         return r;
 207 }
 208
 209 int seat_apply_acls(Seat *s, Session *old_active) {
 210         int r;
 211
 212         assert(s);
 213
 214         r = devnode_acl_all(s->id,
 215                             false,
 216                             !!old_active, old_active ? old_active->user->uid : 0,
 217                             !!s->active, s->active ? s->active->user->uid : 0);
 218
 219         if (r < 0)
 220                 return log_error_errno(r, "Failed to apply ACLs: %m");
 221
 222         return 0;
 223 }
 224
 225 int seat_set_active(Seat *s, Session *session) {
 226         Session *old_active;
 227
 228         assert(s);
 229         assert(!session || session->seat == s);
 230
 231         if (session == s->active)
 232                 return 0;
 233
 234         old_active = s->active;
 235         s->active = session;
 236
 237         if (old_active) {
 238                 session_device_pause_all(old_active);
 239                 session_send_changed(old_active, "Active", NULL);
 240         }
 241
 242         (void) seat_apply_acls(s, old_active);
 243
 244         if (session && session->started) {
 245                 session_send_changed(session, "Active", NULL);
 246                 session_device_resume_all(session);
 247         }
 248
 249         if (!session || session->started)
 250                 seat_send_changed(s, "ActiveSession", NULL);
 251
 252         seat_save(s);
 253
 254         if (session) {
 255                 session_save(session);
 256                 user_save(session->user);
 257         }
 258
 259         if (old_active) {
 260                 session_save(old_active);
 261                 if (!session || session->user != old_active->user)
 262                         user_save(old_active->user);
 263         }
 264
 265         return 0;
 266 }
 267
 268 int seat_switch_to(Seat *s, unsigned num) {
 269         /* Public session positions skip 0 (there is only F1-F12). Maybe it
 270          * will get reassigned in the future, so return error for now. */
 271         if (num == 0)
 272                 return -EINVAL;
 273
 274         if (num >= s->position_count || !s->positions[num]) {
 275                 /* allow switching to unused VTs to trigger auto-activate */
 276                 if (seat_has_vts(s) && num < 64)
 277                         return chvt(num);
 278
 279                 return -EINVAL;
 280         }
 281
 282         return session_activate(s->positions[num]);
 283 }
 284
 285 int seat_switch_to_next(Seat *s) {
 286         unsigned start, i;
 287
 288         if (s->position_count == 0)
 289                 return -EINVAL;
 290
 291         start = 1;
 292         if (s->active && s->active->position > 0)
 293                 start = s->active->position;
 294
 295         for (i = start + 1; i < s->position_count; ++i)
 296                 if (s->positions[i])
 297                         return session_activate(s->positions[i]);
 298
 299         for (i = 1; i < start; ++i)
 300                 if (s->positions[i])
 301                         return session_activate(s->positions[i]);
 302
 303         return -EINVAL;
 304 }
 305
 306 int seat_switch_to_previous(Seat *s) {
 307         unsigned start, i;
 308
 309         if (s->position_count == 0)
 310                 return -EINVAL;
 311
 312         start = 1;
 313         if (s->active && s->active->position > 0)
 314                 start = s->active->position;
 315
 316         for (i = start - 1; i > 0; --i)
 317                 if (s->positions[i])
 318                         return session_activate(s->positions[i]);
 319
 320         for (i = s->position_count - 1; i > start; --i)
 321                 if (s->positions[i])
 322                         return session_activate(s->positions[i]);
 323
 324         return -EINVAL;
 325 }
 326
 327 int seat_active_vt_changed(Seat *s, unsigned vtnr) {
 328         Session *i, *new_active = NULL;
 329         int r;
 330
 331         assert(s);
 332         assert(vtnr >= 1);
 333
 334         if (!seat_has_vts(s))
 335                 return -EINVAL;
 336
 337         log_debug("VT changed to %u", vtnr);
 338
 339         /* we might have earlier closing sessions on the same VT, so try to
 340          * find a running one first */
 341         LIST_FOREACH(sessions_by_seat, i, s->sessions)
 342                 if (i->vtnr == vtnr && !i->stopping) {
 343                         new_active = i;
 344                         break;
 345                 }
 346
 347         if (!new_active) {
 348                 /* no running one? then we can't decide which one is the
 349                  * active one, let the first one win */
 350                 LIST_FOREACH(sessions_by_seat, i, s->sessions)
 351                         if (i->vtnr == vtnr) {
 352                                 new_active = i;
 353                                 break;
 354                         }
 355         }
 356
 357         r = seat_set_active(s, new_active);
 358         manager_spawn_autovt(s->manager, vtnr);
 359
 360         return r;
 361 }
 362
 363 int seat_read_active_vt(Seat *s) {
 364         char t[64];
 365         ssize_t k;
 366         int vtnr;
 367
 368         assert(s);
 369
 370         if (!seat_has_vts(s))
 371                 return 0;
 372
 373         if (lseek(s->manager->console_active_fd, SEEK_SET, 0) < 0)
 374                 return log_error_errno(errno, "lseek on console_active_fd failed: %m");
 375
 376         k = read(s->manager->console_active_fd, t, sizeof(t)-1);
 377         if (k <= 0) {
 378                 log_error("Failed to read current console: %s", k < 0 ? strerror(errno) : "EOF");
 379                 return k < 0 ? -errno : -EIO;
 380         }
 381
 382         t[k] = 0;
 383         truncate_nl(t);
 384
 385         vtnr = vtnr_from_tty(t);
 386         if (vtnr < 0) {
 387                 log_error_errno(vtnr, "Hm, /sys/class/tty/tty0/active is badly formatted: %m");
 388                 return -EIO;
 389         }
 390
 391         return seat_active_vt_changed(s, vtnr);
 392 }
 393
 394 int seat_start(Seat *s) {
 395         assert(s);
 396
 397         if (s->started)
 398                 return 0;
 399
 400         log_struct(LOG_INFO,
 401                    "MESSAGE_ID=" SD_MESSAGE_SEAT_START_STR,
 402                    "SEAT_ID=%s", s->id,
 403                    LOG_MESSAGE("New seat %s.", s->id));
 404
 405         /* Initialize VT magic stuff */
 406         seat_preallocate_vts(s);
 407
 408         /* Read current VT */
 409         seat_read_active_vt(s);
 410
 411         s->started = true;
 412
 413         /* Save seat data */
 414         seat_save(s);
 415
 416         seat_send_signal(s, true);
 417
 418         return 0;
 419 }
 420
 421 int seat_stop(Seat *s, bool force) {
 422         int r;
 423
 424         assert(s);
 425
 426         if (s->started)
 427                 log_struct(LOG_INFO,
 428                            "MESSAGE_ID=" SD_MESSAGE_SEAT_STOP_STR,
 429                            "SEAT_ID=%s", s->id,
 430                            LOG_MESSAGE("Removed seat %s.", s->id));
 431
 432         r = seat_stop_sessions(s, force);
 433
 434         (void) unlink(s->state_file);
 435         seat_add_to_gc_queue(s);
 436
 437         if (s->started)
 438                 seat_send_signal(s, false);
 439
 440         s->started = false;
 441
 442         return r;
 443 }
 444
 445 int seat_stop_sessions(Seat *s, bool force) {
 446         Session *session;
 447         int r = 0, k;
 448
 449         assert(s);
 450
 451         LIST_FOREACH(sessions_by_seat, session, s->sessions) {
 452                 k = session_stop(session, force);
 453                 if (k < 0)
 454                         r = k;
 455         }
 456
 457         return r;
 458 }
 459
 460 void seat_evict_position(Seat *s, Session *session) {
 461         Session *iter;
 462         unsigned pos = session->position;
 463
 464         session->position = 0;
 465
 466         if (pos == 0)
 467                 return;
 468
 469         if (pos < s->position_count && s->positions[pos] == session) {
 470                 s->positions[pos] = NULL;
 471
 472                 /* There might be another session claiming the same
 473                  * position (eg., during gdm->session transition), so let's look
 474                  * for it and set it on the free slot. */
 475                 LIST_FOREACH(sessions_by_seat, iter, s->sessions) {
 476                         if (iter->position == pos && session_get_state(iter) != SESSION_CLOSING) {
 477                                 s->positions[pos] = iter;
 478                                 break;
 479                         }
 480                 }
 481         }
 482 }
 483
 484 void seat_claim_position(Seat *s, Session *session, unsigned pos) {
 485         /* with VTs, the position is always the same as the VTnr */
 486         if (seat_has_vts(s))
 487                 pos = session->vtnr;
 488
 489         if (!GREEDY_REALLOC0(s->positions, s->position_count, pos + 1))
 490                 return;
 491
 492         seat_evict_position(s, session);
 493
 494         session->position = pos;
 495         if (pos > 0)
 496                 s->positions[pos] = session;
 497 }
 498
 499 static void seat_assign_position(Seat *s, Session *session) {
 500         unsigned pos;
 501
 502         if (session->position > 0)
 503                 return;
 504
 505         for (pos = 1; pos < s->position_count; ++pos)
 506                 if (!s->positions[pos])
 507                         break;
 508
 509         seat_claim_position(s, session, pos);
 510 }
 511
 512 int seat_attach_session(Seat *s, Session *session) {
 513         assert(s);
 514         assert(session);
 515         assert(!session->seat);
 516
 517         if (!seat_has_vts(s) != !session->vtnr)
 518                 return -EINVAL;
 519
 520         session->seat = s;
 521         LIST_PREPEND(sessions_by_seat, s->sessions, session);
 522         seat_assign_position(s, session);
 523
 524         /* On seats with VTs, the VT logic defines which session is active. On
 525          * seats without VTs, we automatically activate new sessions. */
 526         if (!seat_has_vts(s))
 527                 seat_set_active(s, session);
 528
 529         return 0;
 530 }
 531
 532 void seat_complete_switch(Seat *s) {
 533         Session *session;
 534
 535         assert(s);
 536
 537         /* if no session-switch is pending or if it got canceled, do nothing */
 538         if (!s->pending_switch)
 539                 return;
 540
 541         session = TAKE_PTR(s->pending_switch);
 542
 543         seat_set_active(s, session);
 544 }
 545
 546 bool seat_has_vts(Seat *s) {
 547         assert(s);
 548
 549         return seat_is_seat0(s) && s->manager->console_active_fd >= 0;
 550 }
 551
 552 bool seat_is_seat0(Seat *s) {
 553         assert(s);
 554
 555         return s->manager->seat0 == s;
 556 }
 557
 558 bool seat_can_multi_session(Seat *s) {
 559         assert(s);
 560
 561         return seat_has_vts(s);
 562 }
 563
 564 bool seat_can_tty(Seat *s) {
 565         assert(s);
 566
 567         return seat_has_vts(s);
 568 }
 569
 570 bool seat_has_master_device(Seat *s) {
 571         assert(s);
 572
 573         /* device list is ordered by "master" flag */
 574         return !!s->devices && s->devices->master;
 575 }
 576
 577 bool seat_can_graphical(Seat *s) {
 578         assert(s);
 579
 580         return seat_has_master_device(s);
 581 }
 582
 583 int seat_get_idle_hint(Seat *s, dual_timestamp *t) {
 584         Session *session;
 585         bool idle_hint = true;
 586         dual_timestamp ts = DUAL_TIMESTAMP_NULL;
 587
 588         assert(s);
 589
 590         LIST_FOREACH(sessions_by_seat, session, s->sessions) {
 591                 dual_timestamp k;
 592                 int ih;
 593
 594                 ih = session_get_idle_hint(session, &k);
 595                 if (ih < 0)
 596                         return ih;
 597
 598                 if (!ih) {
 599                         if (!idle_hint) {
 600                                 if (k.monotonic > ts.monotonic)
 601                                         ts = k;
 602                         } else {
 603                                 idle_hint = false;
 604                                 ts = k;
 605                         }
 606                 } else if (idle_hint) {
 607
 608                         if (k.monotonic > ts.monotonic)
 609                                 ts = k;
 610                 }
 611         }
 612
 613         if (t)
 614                 *t = ts;
 615
 616         return idle_hint;
 617 }
 618
 619 bool seat_may_gc(Seat *s, bool drop_not_started) {
 620         assert(s);
 621
 622         if (drop_not_started && !s->started)
 623                 return true;
 624
 625         if (seat_is_seat0(s))
 626                 return false;
 627
 628         return !seat_has_master_device(s);
 629 }
 630
 631 void seat_add_to_gc_queue(Seat *s) {
 632         assert(s);
 633
 634         if (s->in_gc_queue)
 635                 return;
 636
 637         LIST_PREPEND(gc_queue, s->manager->seat_gc_queue, s);
 638         s->in_gc_queue = true;
 639 }
 640
 641 static bool seat_name_valid_char(char c) {
 642         return
 643                 (c >= 'a' && c <= 'z') ||
 644                 (c >= 'A' && c <= 'Z') ||
 645                 (c >= '0' && c <= '9') ||
 646                 IN_SET(c, '-', '_');
 647 }
 648
 649 bool seat_name_is_valid(const char *name) {
 650         const char *p;
 651
 652         assert(name);
 653
 654         if (!startswith(name, "seat"))
 655                 return false;
 656
 657         if (!name[4])
 658                 return false;
 659
 660         for (p = name; *p; p++)
 661                 if (!seat_name_valid_char(*p))
 662                         return false;
 663
 664         if (strlen(name) > 255)
 665                 return false;
 666
 667         return true;
 668 }