src/login/logind-seat.c

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2
   3 #include <errno.h>
   4 #include <fcntl.h>
   5 #include <stdio_ext.h>
   6 #include <string.h>
   7 #include <sys/stat.h>
   8 #include <unistd.h>
   9
  10 #include "sd-messages.h"
  11
  12 #include "alloc-util.h"
  13 #include "fd-util.h"
  14 #include "fileio.h"
  15 #include "format-util.h"
  16 #include "logind-acl.h"
  17 #include "logind-seat.h"
  18 #include "mkdir.h"
  19 #include "parse-util.h"
  20 #include "stdio-util.h"
  21 #include "string-util.h"
  22 #include "terminal-util.h"
  23 #include "tmpfile-util.h"
  24 #include "util.h"
  25
  26 int seat_new(Seat** ret, Manager *m, const char *id) {
  27         _cleanup_(seat_freep) Seat *s = NULL;
  28         int r;
  29
  30         assert(ret);
  31         assert(m);
  32         assert(id);
  33
  34         if (!seat_name_is_valid(id))
  35                 return -EINVAL;
  36
  37         s = new(Seat, 1);
  38         if (!s)
  39                 return -ENOMEM;
  40
  41         *s = (Seat) {
  42                 .manager = m,
  43         };
  44
  45         s->state_file = strappend("/run/systemd/seats/", id);
  46         if (!s->state_file)
  47                 return -ENOMEM;
  48
  49         s->id = basename(s->state_file);
  50
  51         r = hashmap_put(m->seats, s->id, s);
  52         if (r < 0)
  53                 return r;
  54
  55         *ret = TAKE_PTR(s);
  56         return 0;
  57 }
  58
  59 Seat* seat_free(Seat *s) {
  60         if (!s)
  61                 return NULL;
  62
  63         if (s->in_gc_queue)
  64                 LIST_REMOVE(gc_queue, s->manager->seat_gc_queue, s);
  65
  66         while (s->sessions)
  67                 session_free(s->sessions);
  68
  69         assert(!s->active);
  70
  71         while (s->devices)
  72                 device_free(s->devices);
  73
  74         hashmap_remove(s->manager->seats, s->id);
  75
  76         free(s->positions);
  77         free(s->state_file);
  78
  79         return mfree(s);
  80 }
  81
  82 int seat_save(Seat *s) {
  83         _cleanup_free_ char *temp_path = NULL;
  84         _cleanup_fclose_ FILE *f = NULL;
  85         int r;
  86
  87         assert(s);
  88
  89         if (!s->started)
  90                 return 0;
  91
  92         r = mkdir_safe_label("/run/systemd/seats", 0755, 0, 0, MKDIR_WARN_MODE);
  93         if (r < 0)
  94                 goto fail;
  95
  96         r = fopen_temporary(s->state_file, &f, &temp_path);
  97         if (r < 0)
  98                 goto fail;
  99
 100         (void) __fsetlocking(f, FSETLOCKING_BYCALLER);
 101         (void) fchmod(fileno(f), 0644);
 102
 103         fprintf(f,
 104                 "# This is private data. Do not parse.\n"
 105                 "IS_SEAT0=%i\n"
 106                 "CAN_MULTI_SESSION=%i\n"
 107                 "CAN_TTY=%i\n"
 108                 "CAN_GRAPHICAL=%i\n",
 109                 seat_is_seat0(s),
 110                 seat_can_multi_session(s),
 111                 seat_can_tty(s),
 112                 seat_can_graphical(s));
 113
 114         if (s->active) {
 115                 assert(s->active->user);
 116
 117                 fprintf(f,
 118                         "ACTIVE=%s\n"
 119                         "ACTIVE_UID="UID_FMT"\n",
 120                         s->active->id,
 121                         s->active->user->uid);
 122         }
 123
 124         if (s->sessions) {
 125                 Session *i;
 126
 127                 fputs("SESSIONS=", f);
 128                 LIST_FOREACH(sessions_by_seat, i, s->sessions) {
 129                         fprintf(f,
 130                                 "%s%c",
 131                                 i->id,
 132                                 i->sessions_by_seat_next ? ' ' : '\n');
 133                 }
 134
 135                 fputs("UIDS=", f);
 136                 LIST_FOREACH(sessions_by_seat, i, s->sessions)
 137                         fprintf(f,
 138                                 UID_FMT"%c",
 139                                 i->user->uid,
 140                                 i->sessions_by_seat_next ? ' ' : '\n');
 141         }
 142
 143         r = fflush_and_check(f);
 144         if (r < 0)
 145                 goto fail;
 146
 147         if (rename(temp_path, s->state_file) < 0) {
 148                 r = -errno;
 149                 goto fail;
 150         }
 151
 152         return 0;
 153
 154 fail:
 155         (void) unlink(s->state_file);
 156
 157         if (temp_path)
 158                 (void) unlink(temp_path);
 159
 160         return log_error_errno(r, "Failed to save seat data %s: %m", s->state_file);
 161 }
 162
 163 int seat_load(Seat *s) {
 164         assert(s);
 165
 166         /* There isn't actually anything to read here ... */
 167
 168         return 0;
 169 }
 170
 171 static int vt_allocate(unsigned vtnr) {
 172         char p[sizeof("/dev/tty") + DECIMAL_STR_MAX(unsigned)];
 173         _cleanup_close_ int fd = -1;
 174
 175         assert(vtnr >= 1);
 176
 177         xsprintf(p, "/dev/tty%u", vtnr);
 178         fd = open_terminal(p, O_RDWR|O_NOCTTY|O_CLOEXEC);
 179         if (fd < 0)
 180                 return fd;
 181
 182         return 0;
 183 }
 184
 185 int seat_preallocate_vts(Seat *s) {
 186         int r = 0;
 187         unsigned i;
 188
 189         assert(s);
 190         assert(s->manager);
 191
 192         log_debug("Preallocating VTs...");
 193
 194         if (s->manager->n_autovts <= 0)
 195                 return 0;
 196
 197         if (!seat_has_vts(s))
 198                 return 0;
 199
 200         for (i = 1; i <= s->manager->n_autovts; i++) {
 201                 int q;
 202
 203                 q = vt_allocate(i);
 204                 if (q < 0)
 205                         r = log_error_errno(q, "Failed to preallocate VT %u: %m", i);
 206         }
 207
 208         return r;
 209 }
 210
 211 int seat_apply_acls(Seat *s, Session *old_active) {
 212         int r;
 213
 214         assert(s);
 215
 216         r = devnode_acl_all(s->id,
 217                             false,
 218                             !!old_active, old_active ? old_active->user->uid : 0,
 219                             !!s->active, s->active ? s->active->user->uid : 0);
 220
 221         if (r < 0)
 222                 return log_error_errno(r, "Failed to apply ACLs: %m");
 223
 224         return 0;
 225 }
 226
 227 int seat_set_active(Seat *s, Session *session) {
 228         Session *old_active;
 229
 230         assert(s);
 231         assert(!session || session->seat == s);
 232
 233         if (session == s->active)
 234                 return 0;
 235
 236         old_active = s->active;
 237         s->active = session;
 238
 239         if (old_active) {
 240                 session_device_pause_all(old_active);
 241                 session_send_changed(old_active, "Active", NULL);
 242         }
 243
 244         (void) seat_apply_acls(s, old_active);
 245
 246         if (session && session->started) {
 247                 session_send_changed(session, "Active", NULL);
 248                 session_device_resume_all(session);
 249         }
 250
 251         if (!session || session->started)
 252                 seat_send_changed(s, "ActiveSession", NULL);
 253
 254         seat_save(s);
 255
 256         if (session) {
 257                 session_save(session);
 258                 user_save(session->user);
 259         }
 260
 261         if (old_active) {
 262                 session_save(old_active);
 263                 if (!session || session->user != old_active->user)
 264                         user_save(old_active->user);
 265         }
 266
 267         return 0;
 268 }
 269
 270 int seat_switch_to(Seat *s, unsigned num) {
 271         /* Public session positions skip 0 (there is only F1-F12). Maybe it
 272          * will get reassigned in the future, so return error for now. */
 273         if (num == 0)
 274                 return -EINVAL;
 275
 276         if (num >= s->position_count || !s->positions[num]) {
 277                 /* allow switching to unused VTs to trigger auto-activate */
 278                 if (seat_has_vts(s) && num < 64)
 279                         return chvt(num);
 280
 281                 return -EINVAL;
 282         }
 283
 284         return session_activate(s->positions[num]);
 285 }
 286
 287 int seat_switch_to_next(Seat *s) {
 288         unsigned start, i;
 289
 290         if (s->position_count == 0)
 291                 return -EINVAL;
 292
 293         start = 1;
 294         if (s->active && s->active->position > 0)
 295                 start = s->active->position;
 296
 297         for (i = start + 1; i < s->position_count; ++i)
 298                 if (s->positions[i])
 299                         return session_activate(s->positions[i]);
 300
 301         for (i = 1; i < start; ++i)
 302                 if (s->positions[i])
 303                         return session_activate(s->positions[i]);
 304
 305         return -EINVAL;
 306 }
 307
 308 int seat_switch_to_previous(Seat *s) {
 309         unsigned start, i;
 310
 311         if (s->position_count == 0)
 312                 return -EINVAL;
 313
 314         start = 1;
 315         if (s->active && s->active->position > 0)
 316                 start = s->active->position;
 317
 318         for (i = start - 1; i > 0; --i)
 319                 if (s->positions[i])
 320                         return session_activate(s->positions[i]);
 321
 322         for (i = s->position_count - 1; i > start; --i)
 323                 if (s->positions[i])
 324                         return session_activate(s->positions[i]);
 325
 326         return -EINVAL;
 327 }
 328
 329 int seat_active_vt_changed(Seat *s, unsigned vtnr) {
 330         Session *i, *new_active = NULL;
 331         int r;
 332
 333         assert(s);
 334         assert(vtnr >= 1);
 335
 336         if (!seat_has_vts(s))
 337                 return -EINVAL;
 338
 339         log_debug("VT changed to %u", vtnr);
 340
 341         /* we might have earlier closing sessions on the same VT, so try to
 342          * find a running one first */
 343         LIST_FOREACH(sessions_by_seat, i, s->sessions)
 344                 if (i->vtnr == vtnr && !i->stopping) {
 345                         new_active = i;
 346                         break;
 347                 }
 348
 349         if (!new_active) {
 350                 /* no running one? then we can't decide which one is the
 351                  * active one, let the first one win */
 352                 LIST_FOREACH(sessions_by_seat, i, s->sessions)
 353                         if (i->vtnr == vtnr) {
 354                                 new_active = i;
 355                                 break;
 356                         }
 357         }
 358
 359         r = seat_set_active(s, new_active);
 360         manager_spawn_autovt(s->manager, vtnr);
 361
 362         return r;
 363 }
 364
 365 int seat_read_active_vt(Seat *s) {
 366         char t[64];
 367         ssize_t k;
 368         int vtnr;
 369
 370         assert(s);
 371
 372         if (!seat_has_vts(s))
 373                 return 0;
 374
 375         if (lseek(s->manager->console_active_fd, SEEK_SET, 0) < 0)
 376                 return log_error_errno(errno, "lseek on console_active_fd failed: %m");
 377
 378         k = read(s->manager->console_active_fd, t, sizeof(t)-1);
 379         if (k <= 0) {
 380                 log_error("Failed to read current console: %s", k < 0 ? strerror(errno) : "EOF");
 381                 return k < 0 ? -errno : -EIO;
 382         }
 383
 384         t[k] = 0;
 385         truncate_nl(t);
 386
 387         vtnr = vtnr_from_tty(t);
 388         if (vtnr < 0) {
 389                 log_error_errno(vtnr, "Hm, /sys/class/tty/tty0/active is badly formatted: %m");
 390                 return -EIO;
 391         }
 392
 393         return seat_active_vt_changed(s, vtnr);
 394 }
 395
 396 int seat_start(Seat *s) {
 397         assert(s);
 398
 399         if (s->started)
 400                 return 0;
 401
 402         log_struct(LOG_INFO,
 403                    "MESSAGE_ID=" SD_MESSAGE_SEAT_START_STR,
 404                    "SEAT_ID=%s", s->id,
 405                    LOG_MESSAGE("New seat %s.", s->id));
 406
 407         /* Initialize VT magic stuff */
 408         seat_preallocate_vts(s);
 409
 410         /* Read current VT */
 411         seat_read_active_vt(s);
 412
 413         s->started = true;
 414
 415         /* Save seat data */
 416         seat_save(s);
 417
 418         seat_send_signal(s, true);
 419
 420         return 0;
 421 }
 422
 423 int seat_stop(Seat *s, bool force) {
 424         int r;
 425
 426         assert(s);
 427
 428         if (s->started)
 429                 log_struct(LOG_INFO,
 430                            "MESSAGE_ID=" SD_MESSAGE_SEAT_STOP_STR,
 431                            "SEAT_ID=%s", s->id,
 432                            LOG_MESSAGE("Removed seat %s.", s->id));
 433
 434         r = seat_stop_sessions(s, force);
 435
 436         (void) unlink(s->state_file);
 437         seat_add_to_gc_queue(s);
 438
 439         if (s->started)
 440                 seat_send_signal(s, false);
 441
 442         s->started = false;
 443
 444         return r;
 445 }
 446
 447 int seat_stop_sessions(Seat *s, bool force) {
 448         Session *session;
 449         int r = 0, k;
 450
 451         assert(s);
 452
 453         LIST_FOREACH(sessions_by_seat, session, s->sessions) {
 454                 k = session_stop(session, force);
 455                 if (k < 0)
 456                         r = k;
 457         }
 458
 459         return r;
 460 }
 461
 462 void seat_evict_position(Seat *s, Session *session) {
 463         Session *iter;
 464         unsigned pos = session->position;
 465
 466         session->position = 0;
 467
 468         if (pos == 0)
 469                 return;
 470
 471         if (pos < s->position_count && s->positions[pos] == session) {
 472                 s->positions[pos] = NULL;
 473
 474                 /* There might be another session claiming the same
 475                  * position (eg., during gdm->session transition), so let's look
 476                  * for it and set it on the free slot. */
 477                 LIST_FOREACH(sessions_by_seat, iter, s->sessions) {
 478                         if (iter->position == pos && session_get_state(iter) != SESSION_CLOSING) {
 479                                 s->positions[pos] = iter;
 480                                 break;
 481                         }
 482                 }
 483         }
 484 }
 485
 486 void seat_claim_position(Seat *s, Session *session, unsigned pos) {
 487         /* with VTs, the position is always the same as the VTnr */
 488         if (seat_has_vts(s))
 489                 pos = session->vtnr;
 490
 491         if (!GREEDY_REALLOC0(s->positions, s->position_count, pos + 1))
 492                 return;
 493
 494         seat_evict_position(s, session);
 495
 496         session->position = pos;
 497         if (pos > 0)
 498                 s->positions[pos] = session;
 499 }
 500
 501 static void seat_assign_position(Seat *s, Session *session) {
 502         unsigned pos;
 503
 504         if (session->position > 0)
 505                 return;
 506
 507         for (pos = 1; pos < s->position_count; ++pos)
 508                 if (!s->positions[pos])
 509                         break;
 510
 511         seat_claim_position(s, session, pos);
 512 }
 513
 514 int seat_attach_session(Seat *s, Session *session) {
 515         assert(s);
 516         assert(session);
 517         assert(!session->seat);
 518
 519         if (!seat_has_vts(s) != !session->vtnr)
 520                 return -EINVAL;
 521
 522         session->seat = s;
 523         LIST_PREPEND(sessions_by_seat, s->sessions, session);
 524         seat_assign_position(s, session);
 525
 526         /* On seats with VTs, the VT logic defines which session is active. On
 527          * seats without VTs, we automatically activate new sessions. */
 528         if (!seat_has_vts(s))
 529                 seat_set_active(s, session);
 530
 531         return 0;
 532 }
 533
 534 void seat_complete_switch(Seat *s) {
 535         Session *session;
 536
 537         assert(s);
 538
 539         /* if no session-switch is pending or if it got canceled, do nothing */
 540         if (!s->pending_switch)
 541                 return;
 542
 543         session = TAKE_PTR(s->pending_switch);
 544
 545         seat_set_active(s, session);
 546 }
 547
 548 bool seat_has_vts(Seat *s) {
 549         assert(s);
 550
 551         return seat_is_seat0(s) && s->manager->console_active_fd >= 0;
 552 }
 553
 554 bool seat_is_seat0(Seat *s) {
 555         assert(s);
 556
 557         return s->manager->seat0 == s;
 558 }
 559
 560 bool seat_can_multi_session(Seat *s) {
 561         assert(s);
 562
 563         return seat_has_vts(s);
 564 }
 565
 566 bool seat_can_tty(Seat *s) {
 567         assert(s);
 568
 569         return seat_has_vts(s);
 570 }
 571
 572 bool seat_has_master_device(Seat *s) {
 573         assert(s);
 574
 575         /* device list is ordered by "master" flag */
 576         return !!s->devices && s->devices->master;
 577 }
 578
 579 bool seat_can_graphical(Seat *s) {
 580         assert(s);
 581
 582         return seat_has_master_device(s);
 583 }
 584
 585 int seat_get_idle_hint(Seat *s, dual_timestamp *t) {
 586         Session *session;
 587         bool idle_hint = true;
 588         dual_timestamp ts = DUAL_TIMESTAMP_NULL;
 589
 590         assert(s);
 591
 592         LIST_FOREACH(sessions_by_seat, session, s->sessions) {
 593                 dual_timestamp k;
 594                 int ih;
 595
 596                 ih = session_get_idle_hint(session, &k);
 597                 if (ih < 0)
 598                         return ih;
 599
 600                 if (!ih) {
 601                         if (!idle_hint) {
 602                                 if (k.monotonic > ts.monotonic)
 603                                         ts = k;
 604                         } else {
 605                                 idle_hint = false;
 606                                 ts = k;
 607                         }
 608                 } else if (idle_hint) {
 609
 610                         if (k.monotonic > ts.monotonic)
 611                                 ts = k;
 612                 }
 613         }
 614
 615         if (t)
 616                 *t = ts;
 617
 618         return idle_hint;
 619 }
 620
 621 bool seat_may_gc(Seat *s, bool drop_not_started) {
 622         assert(s);
 623
 624         if (drop_not_started && !s->started)
 625                 return true;
 626
 627         if (seat_is_seat0(s))
 628                 return false;
 629
 630         return !seat_has_master_device(s);
 631 }
 632
 633 void seat_add_to_gc_queue(Seat *s) {
 634         assert(s);
 635
 636         if (s->in_gc_queue)
 637                 return;
 638
 639         LIST_PREPEND(gc_queue, s->manager->seat_gc_queue, s);
 640         s->in_gc_queue = true;
 641 }
 642
 643 static bool seat_name_valid_char(char c) {
 644         return
 645                 (c >= 'a' && c <= 'z') ||
 646                 (c >= 'A' && c <= 'Z') ||
 647                 (c >= '0' && c <= '9') ||
 648                 IN_SET(c, '-', '_');
 649 }
 650
 651 bool seat_name_is_valid(const char *name) {
 652         const char *p;
 653
 654         assert(name);
 655
 656         if (!startswith(name, "seat"))
 657                 return false;
 658
 659         if (!name[4])
 660                 return false;
 661
 662         for (p = name; *p; p++)
 663                 if (!seat_name_valid_char(*p))
 664                         return false;
 665
 666         if (strlen(name) > 255)
 667                 return false;
 668
 669         return true;
 670 }