src/basic/terminal-util.c

   1 /* SPDX-License-Identifier: LGPL-2.1-or-later */
   2
   3 #include <errno.h>
   4 #include <fcntl.h>
   5 #include <limits.h>
   6 #include <linux/kd.h>
   7 #include <linux/tiocl.h>
   8 #include <linux/vt.h>
   9 #include <poll.h>
  10 #include <signal.h>
  11 #include <stdarg.h>
  12 #include <stddef.h>
  13 #include <stdlib.h>
  14 #include <sys/inotify.h>
  15 #include <sys/ioctl.h>
  16 #include <sys/sysmacros.h>
  17 #include <sys/time.h>
  18 #include <sys/types.h>
  19 #include <sys/utsname.h>
  20 #include <termios.h>
  21 #include <unistd.h>
  22
  23 #include "alloc-util.h"
  24 #include "constants.h"
  25 #include "devnum-util.h"
  26 #include "env-util.h"
  27 #include "fd-util.h"
  28 #include "fileio.h"
  29 #include "fs-util.h"
  30 #include "hexdecoct.h"
  31 #include "inotify-util.h"
  32 #include "io-util.h"
  33 #include "log.h"
  34 #include "macro.h"
  35 #include "namespace-util.h"
  36 #include "parse-util.h"
  37 #include "path-util.h"
  38 #include "proc-cmdline.h"
  39 #include "process-util.h"
  40 #include "socket-util.h"
  41 #include "stat-util.h"
  42 #include "stdio-util.h"
  43 #include "string-util.h"
  44 #include "strv.h"
  45 #include "terminal-util.h"
  46 #include "time-util.h"
  47 #include "user-util.h"
  48
  49 static volatile unsigned cached_columns = 0;
  50 static volatile unsigned cached_lines = 0;
  51
  52 static volatile int cached_on_tty = -1;
  53 static volatile int cached_on_dev_null = -1;
  54 static volatile int cached_color_mode = _COLOR_INVALID;
  55 static volatile int cached_underline_enabled = -1;
  56
  57 bool isatty_safe(int fd) {
  58         assert(fd >= 0);
  59
  60         if (isatty(fd))
  61                 return true;
  62
  63         /* Be resilient if we're working on stdio, since they're set up by parent process. */
  64         assert(errno != EBADF || IN_SET(fd, STDIN_FILENO, STDOUT_FILENO, STDERR_FILENO));
  65
  66         return false;
  67 }
  68
  69 int chvt(int vt) {
  70         _cleanup_close_ int fd = -EBADF;
  71
  72         /* Switch to the specified vt number. If the VT is specified <= 0 switch to the VT the kernel log messages go,
  73          * if that's configured. */
  74
  75         fd = open_terminal("/dev/tty0", O_RDWR|O_NOCTTY|O_CLOEXEC|O_NONBLOCK);
  76         if (fd < 0)
  77                 return -errno;
  78
  79         if (vt <= 0) {
  80                 int tiocl[2] = {
  81                         TIOCL_GETKMSGREDIRECT,
  82                         0
  83                 };
  84
  85                 if (ioctl(fd, TIOCLINUX, tiocl) < 0)
  86                         return -errno;
  87
  88                 vt = tiocl[0] <= 0 ? 1 : tiocl[0];
  89         }
  90
  91         return RET_NERRNO(ioctl(fd, VT_ACTIVATE, vt));
  92 }
  93
  94 int read_one_char(FILE *f, char *ret, usec_t t, bool *need_nl) {
  95         _cleanup_free_ char *line = NULL;
  96         struct termios old_termios;
  97         int r, fd;
  98
  99         assert(f);
 100         assert(ret);
 101
 102         /* If this is a terminal, then switch canonical mode off, so that we can read a single
 103          * character. (Note that fmemopen() streams do not have an fd associated with them, let's handle that
 104          * nicely.) */
 105         fd = fileno(f);
 106         if (fd >= 0 && tcgetattr(fd, &old_termios) >= 0) {
 107                 struct termios new_termios = old_termios;
 108
 109                 new_termios.c_lflag &= ~ICANON;
 110                 new_termios.c_cc[VMIN] = 1;
 111                 new_termios.c_cc[VTIME] = 0;
 112
 113                 if (tcsetattr(fd, TCSADRAIN, &new_termios) >= 0) {
 114                         char c;
 115
 116                         if (t != USEC_INFINITY) {
 117                                 if (fd_wait_for_event(fd, POLLIN, t) <= 0) {
 118                                         (void) tcsetattr(fd, TCSADRAIN, &old_termios);
 119                                         return -ETIMEDOUT;
 120                                 }
 121                         }
 122
 123                         r = safe_fgetc(f, &c);
 124                         (void) tcsetattr(fd, TCSADRAIN, &old_termios);
 125                         if (r < 0)
 126                                 return r;
 127                         if (r == 0)
 128                                 return -EIO;
 129
 130                         if (need_nl)
 131                                 *need_nl = c != '\n';
 132
 133                         *ret = c;
 134                         return 0;
 135                 }
 136         }
 137
 138         if (t != USEC_INFINITY && fd > 0) {
 139                 /* Let's wait the specified amount of time for input. When we have no fd we skip this, under
 140                  * the assumption that this is an fmemopen() stream or so where waiting doesn't make sense
 141                  * anyway, as the data is either already in the stream or cannot possible be placed there
 142                  * while we access the stream */
 143
 144                 if (fd_wait_for_event(fd, POLLIN, t) <= 0)
 145                         return -ETIMEDOUT;
 146         }
 147
 148         /* If this is not a terminal, then read a full line instead */
 149
 150         r = read_line(f, 16, &line); /* longer than necessary, to eat up UTF-8 chars/vt100 key sequences */
 151         if (r < 0)
 152                 return r;
 153         if (r == 0)
 154                 return -EIO;
 155
 156         if (strlen(line) != 1)
 157                 return -EBADMSG;
 158
 159         if (need_nl)
 160                 *need_nl = false;
 161
 162         *ret = line[0];
 163         return 0;
 164 }
 165
 166 #define DEFAULT_ASK_REFRESH_USEC (2*USEC_PER_SEC)
 167
 168 int ask_char(char *ret, const char *replies, const char *fmt, ...) {
 169         int r;
 170
 171         assert(ret);
 172         assert(replies);
 173         assert(fmt);
 174
 175         for (;;) {
 176                 va_list ap;
 177                 char c;
 178                 bool need_nl = true;
 179
 180                 fputs(ansi_highlight(), stdout);
 181
 182                 putchar('\r');
 183
 184                 va_start(ap, fmt);
 185                 vprintf(fmt, ap);
 186                 va_end(ap);
 187
 188                 fputs(ansi_normal(), stdout);
 189
 190                 fflush(stdout);
 191
 192                 r = read_one_char(stdin, &c, DEFAULT_ASK_REFRESH_USEC, &need_nl);
 193                 if (r < 0) {
 194
 195                         if (r == -ETIMEDOUT)
 196                                 continue;
 197
 198                         if (r == -EBADMSG) {
 199                                 puts("Bad input, please try again.");
 200                                 continue;
 201                         }
 202
 203                         putchar('\n');
 204                         return r;
 205                 }
 206
 207                 if (need_nl)
 208                         putchar('\n');
 209
 210                 if (strchr(replies, c)) {
 211                         *ret = c;
 212                         return 0;
 213                 }
 214
 215                 puts("Read unexpected character, please try again.");
 216         }
 217 }
 218
 219 int ask_string(char **ret, const char *text, ...) {
 220         _cleanup_free_ char *line = NULL;
 221         va_list ap;
 222         int r;
 223
 224         assert(ret);
 225         assert(text);
 226
 227         fputs(ansi_highlight(), stdout);
 228
 229         va_start(ap, text);
 230         vprintf(text, ap);
 231         va_end(ap);
 232
 233         fputs(ansi_normal(), stdout);
 234
 235         fflush(stdout);
 236
 237         r = read_line(stdin, LONG_LINE_MAX, &line);
 238         if (r < 0)
 239                 return r;
 240         if (r == 0)
 241                 return -EIO;
 242
 243         *ret = TAKE_PTR(line);
 244         return 0;
 245 }
 246
 247 int reset_terminal_fd(int fd, bool switch_to_text) {
 248         struct termios termios;
 249         int r;
 250
 251         /* Set terminal to some sane defaults */
 252
 253         assert(fd >= 0);
 254
 255         if (!isatty_safe(fd))
 256                 return log_debug_errno(errno, "Asked to reset a terminal that actually isn't a terminal: %m");
 257
 258         /* We leave locked terminal attributes untouched, so that Plymouth may set whatever it wants to set,
 259          * and we don't interfere with that. */
 260
 261         /* Disable exclusive mode, just in case */
 262         if (ioctl(fd, TIOCNXCL) < 0)
 263                 log_debug_errno(errno, "TIOCNXCL ioctl failed on TTY, ignoring: %m");
 264
 265         /* Switch to text mode */
 266         if (switch_to_text)
 267                 if (ioctl(fd, KDSETMODE, KD_TEXT) < 0)
 268                         log_debug_errno(errno, "KDSETMODE ioctl for switching to text mode failed on TTY, ignoring: %m");
 269
 270
 271         /* Set default keyboard mode */
 272         r = vt_reset_keyboard(fd);
 273         if (r < 0)
 274                 log_debug_errno(r, "Failed to reset VT keyboard, ignoring: %m");
 275
 276         if (tcgetattr(fd, &termios) < 0) {
 277                 r = log_debug_errno(errno, "Failed to get terminal parameters: %m");
 278                 goto finish;
 279         }
 280
 281         /* We only reset the stuff that matters to the software. How
 282          * hardware is set up we don't touch assuming that somebody
 283          * else will do that for us */
 284
 285         termios.c_iflag &= ~(IGNBRK | BRKINT | ISTRIP | INLCR | IGNCR | IUCLC);
 286         termios.c_iflag |= ICRNL | IMAXBEL | IUTF8;
 287         termios.c_oflag |= ONLCR | OPOST;
 288         termios.c_cflag |= CREAD;
 289         termios.c_lflag = ISIG | ICANON | IEXTEN | ECHO | ECHOE | ECHOK | ECHOCTL | ECHOKE;
 290
 291         termios.c_cc[VINTR]    =   03;  /* ^C */
 292         termios.c_cc[VQUIT]    =  034;  /* ^\ */
 293         termios.c_cc[VERASE]   = 0177;
 294         termios.c_cc[VKILL]    =  025;  /* ^X */
 295         termios.c_cc[VEOF]     =   04;  /* ^D */
 296         termios.c_cc[VSTART]   =  021;  /* ^Q */
 297         termios.c_cc[VSTOP]    =  023;  /* ^S */
 298         termios.c_cc[VSUSP]    =  032;  /* ^Z */
 299         termios.c_cc[VLNEXT]   =  026;  /* ^V */
 300         termios.c_cc[VWERASE]  =  027;  /* ^W */
 301         termios.c_cc[VREPRINT] =  022;  /* ^R */
 302         termios.c_cc[VEOL]     =    0;
 303         termios.c_cc[VEOL2]    =    0;
 304
 305         termios.c_cc[VTIME]  = 0;
 306         termios.c_cc[VMIN]   = 1;
 307
 308         r = RET_NERRNO(tcsetattr(fd, TCSANOW, &termios));
 309
 310 finish:
 311         /* Just in case, flush all crap out */
 312         (void) tcflush(fd, TCIOFLUSH);
 313
 314         return r;
 315 }
 316
 317 int reset_terminal(const char *name) {
 318         _cleanup_close_ int fd = -EBADF;
 319
 320         /* We open the terminal with O_NONBLOCK here, to ensure we
 321          * don't block on carrier if this is a terminal with carrier
 322          * configured. */
 323
 324         fd = open_terminal(name, O_RDWR|O_NOCTTY|O_CLOEXEC|O_NONBLOCK);
 325         if (fd < 0)
 326                 return fd;
 327
 328         return reset_terminal_fd(fd, true);
 329 }
 330
 331 int open_terminal(const char *name, int mode) {
 332         _cleanup_close_ int fd = -EBADF;
 333         unsigned c = 0;
 334
 335         /*
 336          * If a TTY is in the process of being closed opening it might cause EIO. This is horribly awful, but
 337          * unlikely to be changed in the kernel. Hence we work around this problem by retrying a couple of
 338          * times.
 339          *
 340          * https://bugs.launchpad.net/ubuntu/+source/linux/+bug/554172/comments/245
 341          */
 342
 343         if (mode & O_CREAT)
 344                 return -EINVAL;
 345
 346         for (;;) {
 347                 fd = open(name, mode, 0);
 348                 if (fd >= 0)
 349                         break;
 350
 351                 if (errno != EIO)
 352                         return -errno;
 353
 354                 /* Max 1s in total */
 355                 if (c >= 20)
 356                         return -errno;
 357
 358                 (void) usleep_safe(50 * USEC_PER_MSEC);
 359                 c++;
 360         }
 361
 362         if (!isatty_safe(fd))
 363                 return negative_errno();
 364
 365         return TAKE_FD(fd);
 366 }
 367
 368 int acquire_terminal(
 369                 const char *name,
 370                 AcquireTerminalFlags flags,
 371                 usec_t timeout) {
 372
 373         _cleanup_close_ int notify = -EBADF, fd = -EBADF;
 374         usec_t ts = USEC_INFINITY;
 375         int r, wd = -1;
 376
 377         assert(name);
 378         assert(IN_SET(flags & ~ACQUIRE_TERMINAL_PERMISSIVE, ACQUIRE_TERMINAL_TRY, ACQUIRE_TERMINAL_FORCE, ACQUIRE_TERMINAL_WAIT));
 379
 380         /* We use inotify to be notified when the tty is closed. We create the watch before checking if we can actually
 381          * acquire it, so that we don't lose any event.
 382          *
 383          * Note: strictly speaking this actually watches for the device being closed, it does *not* really watch
 384          * whether a tty loses its controlling process. However, unless some rogue process uses TIOCNOTTY on /dev/tty
 385          * *after* closing its tty otherwise this will not become a problem. As long as the administrator makes sure to
 386          * not configure any service on the same tty as an untrusted user this should not be a problem. (Which they
 387          * probably should not do anyway.) */
 388
 389         if ((flags & ~ACQUIRE_TERMINAL_PERMISSIVE) == ACQUIRE_TERMINAL_WAIT) {
 390                 notify = inotify_init1(IN_CLOEXEC | (timeout != USEC_INFINITY ? IN_NONBLOCK : 0));
 391                 if (notify < 0)
 392                         return -errno;
 393
 394                 wd = inotify_add_watch(notify, name, IN_CLOSE);
 395                 if (wd < 0)
 396                         return -errno;
 397
 398                 if (timeout != USEC_INFINITY)
 399                         ts = now(CLOCK_MONOTONIC);
 400         }
 401
 402         for (;;) {
 403                 struct sigaction sa_old, sa_new = {
 404                         .sa_handler = SIG_IGN,
 405                         .sa_flags = SA_RESTART,
 406                 };
 407
 408                 if (notify >= 0) {
 409                         r = flush_fd(notify);
 410                         if (r < 0)
 411                                 return r;
 412                 }
 413
 414                 /* We pass here O_NOCTTY only so that we can check the return value TIOCSCTTY and have a reliable way
 415                  * to figure out if we successfully became the controlling process of the tty */
 416                 fd = open_terminal(name, O_RDWR|O_NOCTTY|O_CLOEXEC);
 417                 if (fd < 0)
 418                         return fd;
 419
 420                 /* Temporarily ignore SIGHUP, so that we don't get SIGHUP'ed if we already own the tty. */
 421                 assert_se(sigaction(SIGHUP, &sa_new, &sa_old) == 0);
 422
 423                 /* First, try to get the tty */
 424                 r = RET_NERRNO(ioctl(fd, TIOCSCTTY, (flags & ~ACQUIRE_TERMINAL_PERMISSIVE) == ACQUIRE_TERMINAL_FORCE));
 425
 426                 /* Reset signal handler to old value */
 427                 assert_se(sigaction(SIGHUP, &sa_old, NULL) == 0);
 428
 429                 /* Success? Exit the loop now! */
 430                 if (r >= 0)
 431                         break;
 432
 433                 /* Any failure besides -EPERM? Fail, regardless of the mode. */
 434                 if (r != -EPERM)
 435                         return r;
 436
 437                 if (flags & ACQUIRE_TERMINAL_PERMISSIVE) /* If we are in permissive mode, then EPERM is fine, turn this
 438                                                           * into a success. Note that EPERM is also returned if we
 439                                                           * already are the owner of the TTY. */
 440                         break;
 441
 442                 if (flags != ACQUIRE_TERMINAL_WAIT) /* If we are in TRY or FORCE mode, then propagate EPERM as EPERM */
 443                         return r;
 444
 445                 assert(notify >= 0);
 446                 assert(wd >= 0);
 447
 448                 for (;;) {
 449                         union inotify_event_buffer buffer;
 450                         ssize_t l;
 451
 452                         if (timeout != USEC_INFINITY) {
 453                                 usec_t n;
 454
 455                                 assert(ts != USEC_INFINITY);
 456
 457                                 n = usec_sub_unsigned(now(CLOCK_MONOTONIC), ts);
 458                                 if (n >= timeout)
 459                                         return -ETIMEDOUT;
 460
 461                                 r = fd_wait_for_event(notify, POLLIN, usec_sub_unsigned(timeout, n));
 462                                 if (r < 0)
 463                                         return r;
 464                                 if (r == 0)
 465                                         return -ETIMEDOUT;
 466                         }
 467
 468                         l = read(notify, &buffer, sizeof(buffer));
 469                         if (l < 0) {
 470                                 if (ERRNO_IS_TRANSIENT(errno))
 471                                         continue;
 472
 473                                 return -errno;
 474                         }
 475
 476                         FOREACH_INOTIFY_EVENT(e, buffer, l) {
 477                                 if (e->mask & IN_Q_OVERFLOW) /* If we hit an inotify queue overflow, simply check if the terminal is up for grabs now. */
 478                                         break;
 479
 480                                 if (e->wd != wd || !(e->mask & IN_CLOSE)) /* Safety checks */
 481                                         return -EIO;
 482                         }
 483
 484                         break;
 485                 }
 486
 487                 /* We close the tty fd here since if the old session ended our handle will be dead. It's important that
 488                  * we do this after sleeping, so that we don't enter an endless loop. */
 489                 fd = safe_close(fd);
 490         }
 491
 492         return TAKE_FD(fd);
 493 }
 494
 495 int release_terminal(void) {
 496         static const struct sigaction sa_new = {
 497                 .sa_handler = SIG_IGN,
 498                 .sa_flags = SA_RESTART,
 499         };
 500
 501         _cleanup_close_ int fd = -EBADF;
 502         struct sigaction sa_old;
 503         int r;
 504
 505         fd = open("/dev/tty", O_RDWR|O_NOCTTY|O_CLOEXEC|O_NONBLOCK);
 506         if (fd < 0)
 507                 return -errno;
 508
 509         /* Temporarily ignore SIGHUP, so that we don't get SIGHUP'ed
 510          * by our own TIOCNOTTY */
 511         assert_se(sigaction(SIGHUP, &sa_new, &sa_old) == 0);
 512
 513         r = RET_NERRNO(ioctl(fd, TIOCNOTTY));
 514
 515         assert_se(sigaction(SIGHUP, &sa_old, NULL) == 0);
 516
 517         return r;
 518 }
 519
 520 int terminal_vhangup_fd(int fd) {
 521         assert(fd >= 0);
 522         return RET_NERRNO(ioctl(fd, TIOCVHANGUP));
 523 }
 524
 525 int terminal_vhangup(const char *name) {
 526         _cleanup_close_ int fd = -EBADF;
 527
 528         fd = open_terminal(name, O_RDWR|O_NOCTTY|O_CLOEXEC|O_NONBLOCK);
 529         if (fd < 0)
 530                 return fd;
 531
 532         return terminal_vhangup_fd(fd);
 533 }
 534
 535 int vt_disallocate(const char *name) {
 536         const char *e;
 537         int r;
 538
 539         /* Deallocate the VT if possible. If not possible
 540          * (i.e. because it is the active one), at least clear it
 541          * entirely (including the scrollback buffer). */
 542
 543         e = path_startswith(name, "/dev/");
 544         if (!e)
 545                 return -EINVAL;
 546
 547         if (tty_is_vc(name)) {
 548                 _cleanup_close_ int fd = -EBADF;
 549                 unsigned u;
 550                 const char *n;
 551
 552                 n = startswith(e, "tty");
 553                 if (!n)
 554                         return -EINVAL;
 555
 556                 r = safe_atou(n, &u);
 557                 if (r < 0)
 558                         return r;
 559
 560                 if (u <= 0)
 561                         return -EINVAL;
 562
 563                 /* Try to deallocate */
 564                 fd = open_terminal("/dev/tty0", O_RDWR|O_NOCTTY|O_CLOEXEC|O_NONBLOCK);
 565                 if (fd < 0)
 566                         return fd;
 567
 568                 r = ioctl(fd, VT_DISALLOCATE, u);
 569                 if (r >= 0)
 570                         return 0;
 571                 if (errno != EBUSY)
 572                         return -errno;
 573         }
 574
 575         /* So this is not a VT (in which case we cannot deallocate it),
 576          * or we failed to deallocate. Let's at least clear the screen. */
 577
 578         _cleanup_close_ int fd2 = open_terminal(name, O_RDWR|O_NOCTTY|O_CLOEXEC);
 579         if (fd2 < 0)
 580                 return fd2;
 581
 582         (void) loop_write(fd2,
 583                           "\033[r"   /* clear scrolling region */
 584                           "\033[H"   /* move home */
 585                           "\033[3J", /* clear screen including scrollback, requires Linux 2.6.40 */
 586                           10);
 587         return 0;
 588 }
 589
 590 int make_console_stdio(void) {
 591         int fd, r;
 592
 593         /* Make /dev/console the controlling terminal and stdin/stdout/stderr, if we can. If we can't use
 594          * /dev/null instead. This is particularly useful if /dev/console is turned off, e.g. if console=null
 595          * is specified on the kernel command line. */
 596
 597         fd = acquire_terminal("/dev/console", ACQUIRE_TERMINAL_FORCE|ACQUIRE_TERMINAL_PERMISSIVE, USEC_INFINITY);
 598         if (fd < 0) {
 599                 log_warning_errno(fd, "Failed to acquire terminal, using /dev/null stdin/stdout/stderr instead: %m");
 600
 601                 r = make_null_stdio();
 602                 if (r < 0)
 603                         return log_error_errno(r, "Failed to make /dev/null stdin/stdout/stderr: %m");
 604
 605         } else {
 606                 unsigned rows, cols;
 607
 608                 r = reset_terminal_fd(fd, /* switch_to_text= */ true);
 609                 if (r < 0)
 610                         log_warning_errno(r, "Failed to reset terminal, ignoring: %m");
 611
 612                 r = proc_cmdline_tty_size("/dev/console", &rows, &cols);
 613                 if (r < 0)
 614                         log_warning_errno(r, "Failed to get terminal size, ignoring: %m");
 615                 else {
 616                         r = terminal_set_size_fd(fd, NULL, rows, cols);
 617                         if (r < 0)
 618                                 log_warning_errno(r, "Failed to set terminal size, ignoring: %m");
 619                 }
 620
 621                 r = rearrange_stdio(fd, fd, fd); /* This invalidates 'fd' both on success and on failure. */
 622                 if (r < 0)
 623                         return log_error_errno(r, "Failed to make terminal stdin/stdout/stderr: %m");
 624         }
 625
 626         reset_terminal_feature_caches();
 627         return 0;
 628 }
 629
 630 bool tty_is_vc(const char *tty) {
 631         assert(tty);
 632
 633         return vtnr_from_tty(tty) >= 0;
 634 }
 635
 636 bool tty_is_console(const char *tty) {
 637         assert(tty);
 638
 639         return streq(skip_dev_prefix(tty), "console");
 640 }
 641
 642 int vtnr_from_tty(const char *tty) {
 643         int i, r;
 644
 645         assert(tty);
 646
 647         tty = skip_dev_prefix(tty);
 648
 649         if (!startswith(tty, "tty") )
 650                 return -EINVAL;
 651
 652         if (!ascii_isdigit(tty[3]))
 653                 return -EINVAL;
 654
 655         r = safe_atoi(tty+3, &i);
 656         if (r < 0)
 657                 return r;
 658
 659         if (i < 0 || i > 63)
 660                 return -EINVAL;
 661
 662         return i;
 663 }
 664
 665  int resolve_dev_console(char **ret) {
 666         _cleanup_free_ char *active = NULL;
 667         char *tty;
 668         int r;
 669
 670         assert(ret);
 671
 672         /* Resolve where /dev/console is pointing to, if /sys is actually ours (i.e. not read-only-mounted which is a
 673          * sign for container setups) */
 674
 675         if (path_is_read_only_fs("/sys") > 0)
 676                 return -ENOMEDIUM;
 677
 678         r = read_one_line_file("/sys/class/tty/console/active", &active);
 679         if (r < 0)
 680                 return r;
 681
 682         /* If multiple log outputs are configured the last one is what /dev/console points to */
 683         tty = strrchr(active, ' ');
 684         if (tty)
 685                 tty++;
 686         else
 687                 tty = active;
 688
 689         if (streq(tty, "tty0")) {
 690                 active = mfree(active);
 691
 692                 /* Get the active VC (e.g. tty1) */
 693                 r = read_one_line_file("/sys/class/tty/tty0/active", &active);
 694                 if (r < 0)
 695                         return r;
 696
 697                 tty = active;
 698         }
 699
 700         if (tty == active)
 701                 *ret = TAKE_PTR(active);
 702         else {
 703                 char *tmp;
 704
 705                 tmp = strdup(tty);
 706                 if (!tmp)
 707                         return -ENOMEM;
 708
 709                 *ret = tmp;
 710         }
 711
 712         return 0;
 713 }
 714
 715 int get_kernel_consoles(char ***ret) {
 716         _cleanup_strv_free_ char **l = NULL;
 717         _cleanup_free_ char *line = NULL;
 718         const char *p;
 719         int r;
 720
 721         assert(ret);
 722
 723         /* If /sys is mounted read-only this means we are running in some kind of container environment. In that
 724          * case /sys would reflect the host system, not us, hence ignore the data we can read from it. */
 725         if (path_is_read_only_fs("/sys") > 0)
 726                 goto fallback;
 727
 728         r = read_one_line_file("/sys/class/tty/console/active", &line);
 729         if (r < 0)
 730                 return r;
 731
 732         p = line;
 733         for (;;) {
 734                 _cleanup_free_ char *tty = NULL, *path = NULL;
 735
 736                 r = extract_first_word(&p, &tty, NULL, 0);
 737                 if (r < 0)
 738                         return r;
 739                 if (r == 0)
 740                         break;
 741
 742                 if (streq(tty, "tty0")) {
 743                         tty = mfree(tty);
 744                         r = read_one_line_file("/sys/class/tty/tty0/active", &tty);
 745                         if (r < 0)
 746                                 return r;
 747                 }
 748
 749                 path = path_join("/dev", tty);
 750                 if (!path)
 751                         return -ENOMEM;
 752
 753                 if (access(path, F_OK) < 0) {
 754                         log_debug_errno(errno, "Console device %s is not accessible, skipping: %m", path);
 755                         continue;
 756                 }
 757
 758                 r = strv_consume(&l, TAKE_PTR(path));
 759                 if (r < 0)
 760                         return r;
 761         }
 762
 763         if (strv_isempty(l)) {
 764                 log_debug("No devices found for system console");
 765                 goto fallback;
 766         }
 767
 768         *ret = TAKE_PTR(l);
 769
 770         return 0;
 771
 772 fallback:
 773         r = strv_extend(&l, "/dev/console");
 774         if (r < 0)
 775                 return r;
 776
 777         *ret = TAKE_PTR(l);
 778
 779         return 0;
 780 }
 781
 782 bool tty_is_vc_resolve(const char *tty) {
 783         _cleanup_free_ char *resolved = NULL;
 784
 785         assert(tty);
 786
 787         tty = skip_dev_prefix(tty);
 788
 789         if (streq(tty, "console")) {
 790                 if (resolve_dev_console(&resolved) < 0)
 791                         return false;
 792
 793                 tty = resolved;
 794         }
 795
 796         return tty_is_vc(tty);
 797 }
 798
 799 const char *default_term_for_tty(const char *tty) {
 800         return tty && tty_is_vc_resolve(tty) ? "linux" : "vt220";
 801 }
 802
 803 int fd_columns(int fd) {
 804         struct winsize ws = {};
 805
 806         if (fd < 0)
 807                 return -EBADF;
 808
 809         if (ioctl(fd, TIOCGWINSZ, &ws) < 0)
 810                 return -errno;
 811
 812         if (ws.ws_col <= 0)
 813                 return -EIO;
 814
 815         return ws.ws_col;
 816 }
 817
 818 unsigned columns(void) {
 819         const char *e;
 820         int c;
 821
 822         if (cached_columns > 0)
 823                 return cached_columns;
 824
 825         c = 0;
 826         e = getenv("COLUMNS");
 827         if (e)
 828                 (void) safe_atoi(e, &c);
 829
 830         if (c <= 0 || c > USHRT_MAX) {
 831                 c = fd_columns(STDOUT_FILENO);
 832                 if (c <= 0)
 833                         c = 80;
 834         }
 835
 836         cached_columns = c;
 837         return cached_columns;
 838 }
 839
 840 int fd_lines(int fd) {
 841         struct winsize ws = {};
 842
 843         if (fd < 0)
 844                 return -EBADF;
 845
 846         if (ioctl(fd, TIOCGWINSZ, &ws) < 0)
 847                 return -errno;
 848
 849         if (ws.ws_row <= 0)
 850                 return -EIO;
 851
 852         return ws.ws_row;
 853 }
 854
 855 unsigned lines(void) {
 856         const char *e;
 857         int l;
 858
 859         if (cached_lines > 0)
 860                 return cached_lines;
 861
 862         l = 0;
 863         e = getenv("LINES");
 864         if (e)
 865                 (void) safe_atoi(e, &l);
 866
 867         if (l <= 0 || l > USHRT_MAX) {
 868                 l = fd_lines(STDOUT_FILENO);
 869                 if (l <= 0)
 870                         l = 24;
 871         }
 872
 873         cached_lines = l;
 874         return cached_lines;
 875 }
 876
 877 int terminal_set_size_fd(int fd, const char *ident, unsigned rows, unsigned cols) {
 878         struct winsize ws;
 879
 880         if (rows == UINT_MAX && cols == UINT_MAX)
 881                 return 0;
 882
 883         if (ioctl(fd, TIOCGWINSZ, &ws) < 0)
 884                 return log_debug_errno(errno,
 885                                        "TIOCGWINSZ ioctl for getting %s size failed, not setting terminal size: %m",
 886                                        ident ?: "TTY");
 887
 888         if (rows == UINT_MAX)
 889                 rows = ws.ws_row;
 890         else if (rows > USHRT_MAX)
 891                 rows = USHRT_MAX;
 892
 893         if (cols == UINT_MAX)
 894                 cols = ws.ws_col;
 895         else if (cols > USHRT_MAX)
 896                 cols = USHRT_MAX;
 897
 898         if (rows == ws.ws_row && cols == ws.ws_col)
 899                 return 0;
 900
 901         ws.ws_row = rows;
 902         ws.ws_col = cols;
 903
 904         if (ioctl(fd, TIOCSWINSZ, &ws) < 0)
 905                 return log_debug_errno(errno, "TIOCSWINSZ ioctl for setting %s size failed: %m", ident ?: "TTY");
 906
 907         return 0;
 908 }
 909
 910 int proc_cmdline_tty_size(const char *tty, unsigned *ret_rows, unsigned *ret_cols) {
 911         _cleanup_free_ char *rowskey = NULL, *rowsvalue = NULL, *colskey = NULL, *colsvalue = NULL;
 912         unsigned rows = UINT_MAX, cols = UINT_MAX;
 913         int r;
 914
 915         assert(tty);
 916
 917         if (!ret_rows && !ret_cols)
 918                 return 0;
 919
 920         tty = skip_dev_prefix(tty);
 921         if (!in_charset(tty, ALPHANUMERICAL))
 922                 return log_debug_errno(SYNTHETIC_ERRNO(EINVAL), "%s contains non-alphanumeric characters", tty);
 923
 924         rowskey = strjoin("systemd.tty.rows.", tty);
 925         if (!rowskey)
 926                 return -ENOMEM;
 927
 928         colskey = strjoin("systemd.tty.columns.", tty);
 929         if (!colskey)
 930                 return -ENOMEM;
 931
 932         r = proc_cmdline_get_key_many(/* flags = */ 0,
 933                                       rowskey, &rowsvalue,
 934                                       colskey, &colsvalue);
 935         if (r < 0)
 936                 return log_debug_errno(r, "Failed to read TTY size of %s from kernel cmdline: %m", tty);
 937
 938         if (rowsvalue) {
 939                 r = safe_atou(rowsvalue, &rows);
 940                 if (r < 0)
 941                         return log_debug_errno(r, "Failed to parse %s=%s: %m", rowskey, rowsvalue);
 942         }
 943
 944         if (colsvalue) {
 945                 r = safe_atou(colsvalue, &cols);
 946                 if (r < 0)
 947                         return log_debug_errno(r, "Failed to parse %s=%s: %m", colskey, colsvalue);
 948         }
 949
 950         if (ret_rows)
 951                 *ret_rows = rows;
 952         if (ret_cols)
 953                 *ret_cols = cols;
 954
 955         return 0;
 956 }
 957
 958 /* intended to be used as a SIGWINCH sighandler */
 959 void columns_lines_cache_reset(int signum) {
 960         cached_columns = 0;
 961         cached_lines = 0;
 962 }
 963
 964 void reset_terminal_feature_caches(void) {
 965         cached_columns = 0;
 966         cached_lines = 0;
 967
 968         cached_color_mode = _COLOR_INVALID;
 969         cached_underline_enabled = -1;
 970         cached_on_tty = -1;
 971         cached_on_dev_null = -1;
 972 }
 973
 974 bool on_tty(void) {
 975
 976         /* We check both stdout and stderr, so that situations where pipes on the shell are used are reliably
 977          * recognized, regardless if only the output or the errors are piped to some place. Since on_tty() is generally
 978          * used to default to a safer, non-interactive, non-color mode of operation it's probably good to be defensive
 979          * here, and check for both. Note that we don't check for STDIN_FILENO, because it should fine to use fancy
 980          * terminal functionality when outputting stuff, even if the input is piped to us. */
 981
 982         if (cached_on_tty < 0)
 983                 cached_on_tty =
 984                         isatty(STDOUT_FILENO) > 0 &&
 985                         isatty(STDERR_FILENO) > 0;
 986
 987         return cached_on_tty;
 988 }
 989
 990 int getttyname_malloc(int fd, char **ret) {
 991         char path[PATH_MAX], *c; /* PATH_MAX is counted *with* the trailing NUL byte */
 992         int r;
 993
 994         assert(fd >= 0);
 995         assert(ret);
 996
 997         r = ttyname_r(fd, path, sizeof path); /* positive error */
 998         assert(r >= 0);
 999         if (r == ERANGE)
1000                 return -ENAMETOOLONG;
1001         if (r > 0)
1002                 return -r;
1003
1004         c = strdup(skip_dev_prefix(path));
1005         if (!c)
1006                 return -ENOMEM;
1007
1008         *ret = c;
1009         return 0;
1010 }
1011
1012 int getttyname_harder(int fd, char **ret) {
1013         _cleanup_free_ char *s = NULL;
1014         int r;
1015
1016         r = getttyname_malloc(fd, &s);
1017         if (r < 0)
1018                 return r;
1019
1020         if (streq(s, "tty"))
1021                 return get_ctty(0, NULL, ret);
1022
1023         *ret = TAKE_PTR(s);
1024         return 0;
1025 }
1026
1027 int get_ctty_devnr(pid_t pid, dev_t *d) {
1028         int r;
1029         _cleanup_free_ char *line = NULL;
1030         const char *p;
1031         unsigned long ttynr;
1032
1033         assert(pid >= 0);
1034
1035         p = procfs_file_alloca(pid, "stat");
1036         r = read_one_line_file(p, &line);
1037         if (r < 0)
1038                 return r;
1039
1040         p = strrchr(line, ')');
1041         if (!p)
1042                 return -EIO;
1043
1044         p++;
1045
1046         if (sscanf(p, " "
1047                    "%*c "  /* state */
1048                    "%*d "  /* ppid */
1049                    "%*d "  /* pgrp */
1050                    "%*d "  /* session */
1051                    "%lu ", /* ttynr */
1052                    &ttynr) != 1)
1053                 return -EIO;
1054
1055         if (devnum_is_zero(ttynr))
1056                 return -ENXIO;
1057
1058         if (d)
1059                 *d = (dev_t) ttynr;
1060
1061         return 0;
1062 }
1063
1064 int get_ctty(pid_t pid, dev_t *ret_devnr, char **ret) {
1065         char pty[STRLEN("/dev/pts/") + DECIMAL_STR_MAX(dev_t) + 1];
1066         _cleanup_free_ char *buf = NULL;
1067         const char *fn = NULL, *w;
1068         dev_t devnr;
1069         int r;
1070
1071         r = get_ctty_devnr(pid, &devnr);
1072         if (r < 0)
1073                 return r;
1074
1075         r = device_path_make_canonical(S_IFCHR, devnr, &buf);
1076         if (r < 0) {
1077                 struct stat st;
1078
1079                 if (r != -ENOENT) /* No symlink for this in /dev/char/? */
1080                         return r;
1081
1082                 /* Maybe this is PTY? PTY devices are not listed in /dev/char/, as they don't follow the
1083                  * Linux device model and hence device_path_make_canonical() doesn't work for them. Let's
1084                  * assume this is a PTY for a moment, and check if the device node this would then map to in
1085                  * /dev/pts/ matches the one we are looking for. This way we don't have to hardcode the major
1086                  * number (which is 136 btw), but we still rely on the fact that PTY numbers map directly to
1087                  * the minor number of the pty. */
1088                 xsprintf(pty, "/dev/pts/%u", minor(devnr));
1089
1090                 if (stat(pty, &st) < 0) {
1091                         if (errno != ENOENT)
1092                                 return -errno;
1093
1094                 } else if (S_ISCHR(st.st_mode) && devnr == st.st_rdev) /* Bingo! */
1095                         fn = pty;
1096
1097                 if (!fn) {
1098                         /* Doesn't exist, or not a PTY? Probably something similar to the PTYs which have no
1099                          * symlink in /dev/char/. Let's return something vaguely useful. */
1100                         r = device_path_make_major_minor(S_IFCHR, devnr, &buf);
1101                         if (r < 0)
1102                                 return r;
1103
1104                         fn = buf;
1105                 }
1106         } else
1107                 fn = buf;
1108
1109         w = path_startswith(fn, "/dev/");
1110         if (!w)
1111                 return -EINVAL;
1112
1113         if (ret) {
1114                 _cleanup_free_ char *b = NULL;
1115
1116                 b = strdup(w);
1117                 if (!b)
1118                         return -ENOMEM;
1119
1120                 *ret = TAKE_PTR(b);
1121         }
1122
1123         if (ret_devnr)
1124                 *ret_devnr = devnr;
1125
1126         return 0;
1127 }
1128
1129 int ptsname_malloc(int fd, char **ret) {
1130         size_t l = 100;
1131
1132         assert(fd >= 0);
1133         assert(ret);
1134
1135         for (;;) {
1136                 char *c;
1137
1138                 c = new(char, l);
1139                 if (!c)
1140                         return -ENOMEM;
1141
1142                 if (ptsname_r(fd, c, l) == 0) {
1143                         *ret = c;
1144                         return 0;
1145                 }
1146                 if (errno != ERANGE) {
1147                         free(c);
1148                         return -errno;
1149                 }
1150
1151                 free(c);
1152
1153                 if (l > SIZE_MAX / 2)
1154                         return -ENOMEM;
1155
1156                 l *= 2;
1157         }
1158 }
1159
1160 int openpt_allocate(int flags, char **ret_slave) {
1161         _cleanup_close_ int fd = -EBADF;
1162         _cleanup_free_ char *p = NULL;
1163         int r;
1164
1165         fd = posix_openpt(flags|O_NOCTTY|O_CLOEXEC);
1166         if (fd < 0)
1167                 return -errno;
1168
1169         if (ret_slave) {
1170                 r = ptsname_malloc(fd, &p);
1171                 if (r < 0)
1172                         return r;
1173
1174                 if (!path_startswith(p, "/dev/pts/"))
1175                         return -EINVAL;
1176         }
1177
1178         if (unlockpt(fd) < 0)
1179                 return -errno;
1180
1181         if (ret_slave)
1182                 *ret_slave = TAKE_PTR(p);
1183
1184         return TAKE_FD(fd);
1185 }
1186
1187 static int ptsname_namespace(int pty, char **ret) {
1188         int no = -1, r;
1189
1190         /* Like ptsname(), but doesn't assume that the path is
1191          * accessible in the local namespace. */
1192
1193         r = ioctl(pty, TIOCGPTN, &no);
1194         if (r < 0)
1195                 return -errno;
1196
1197         if (no < 0)
1198                 return -EIO;
1199
1200         if (asprintf(ret, "/dev/pts/%i", no) < 0)
1201                 return -ENOMEM;
1202
1203         return 0;
1204 }
1205
1206 int openpt_allocate_in_namespace(pid_t pid, int flags, char **ret_slave) {
1207         _cleanup_close_ int pidnsfd = -EBADF, mntnsfd = -EBADF, usernsfd = -EBADF, rootfd = -EBADF, fd = -EBADF;
1208         _cleanup_close_pair_ int pair[2] = EBADF_PAIR;
1209         pid_t child;
1210         int r;
1211
1212         assert(pid > 0);
1213
1214         r = namespace_open(pid, &pidnsfd, &mntnsfd, /* ret_netns_fd = */ NULL, &usernsfd, &rootfd);
1215         if (r < 0)
1216                 return r;
1217
1218         if (socketpair(AF_UNIX, SOCK_DGRAM, 0, pair) < 0)
1219                 return -errno;
1220
1221         r = namespace_fork("(sd-openptns)", "(sd-openpt)", NULL, 0, FORK_RESET_SIGNALS|FORK_DEATHSIG_SIGKILL,
1222                            pidnsfd, mntnsfd, -1, usernsfd, rootfd, &child);
1223         if (r < 0)
1224                 return r;
1225         if (r == 0) {
1226                 pair[0] = safe_close(pair[0]);
1227
1228                 fd = openpt_allocate(flags, NULL);
1229                 if (fd < 0)
1230                         _exit(EXIT_FAILURE);
1231
1232                 if (send_one_fd(pair[1], fd, 0) < 0)
1233                         _exit(EXIT_FAILURE);
1234
1235                 _exit(EXIT_SUCCESS);
1236         }
1237
1238         pair[1] = safe_close(pair[1]);
1239
1240         r = wait_for_terminate_and_check("(sd-openptns)", child, 0);
1241         if (r < 0)
1242                 return r;
1243         if (r != EXIT_SUCCESS)
1244                 return -EIO;
1245
1246         fd = receive_one_fd(pair[0], 0);
1247         if (fd < 0)
1248                 return fd;
1249
1250         if (ret_slave) {
1251                 r = ptsname_namespace(fd, ret_slave);
1252                 if (r < 0)
1253                         return r;
1254         }
1255
1256         return TAKE_FD(fd);
1257 }
1258
1259 int open_terminal_in_namespace(pid_t pid, const char *name, int mode) {
1260         _cleanup_close_ int pidnsfd = -EBADF, mntnsfd = -EBADF, usernsfd = -EBADF, rootfd = -EBADF;
1261         _cleanup_close_pair_ int pair[2] = EBADF_PAIR;
1262         pid_t child;
1263         int r;
1264
1265         r = namespace_open(pid, &pidnsfd, &mntnsfd, /* ret_netns_fd = */ NULL, &usernsfd, &rootfd);
1266         if (r < 0)
1267                 return r;
1268
1269         if (socketpair(AF_UNIX, SOCK_DGRAM, 0, pair) < 0)
1270                 return -errno;
1271
1272         r = namespace_fork("(sd-terminalns)", "(sd-terminal)", NULL, 0, FORK_RESET_SIGNALS|FORK_DEATHSIG_SIGKILL,
1273                            pidnsfd, mntnsfd, -1, usernsfd, rootfd, &child);
1274         if (r < 0)
1275                 return r;
1276         if (r == 0) {
1277                 int master;
1278
1279                 pair[0] = safe_close(pair[0]);
1280
1281                 master = open_terminal(name, mode|O_NOCTTY|O_CLOEXEC);
1282                 if (master < 0)
1283                         _exit(EXIT_FAILURE);
1284
1285                 if (send_one_fd(pair[1], master, 0) < 0)
1286                         _exit(EXIT_FAILURE);
1287
1288                 _exit(EXIT_SUCCESS);
1289         }
1290
1291         pair[1] = safe_close(pair[1]);
1292
1293         r = wait_for_terminate_and_check("(sd-terminalns)", child, 0);
1294         if (r < 0)
1295                 return r;
1296         if (r != EXIT_SUCCESS)
1297                 return -EIO;
1298
1299         return receive_one_fd(pair[0], 0);
1300 }
1301
1302 static bool on_dev_null(void) {
1303         struct stat dst, ost, est;
1304
1305         if (cached_on_dev_null >= 0)
1306                 return cached_on_dev_null;
1307
1308         if (stat("/dev/null", &dst) < 0 || fstat(STDOUT_FILENO, &ost) < 0 || fstat(STDERR_FILENO, &est) < 0)
1309                 cached_on_dev_null = false;
1310         else
1311                 cached_on_dev_null = stat_inode_same(&dst, &ost) && stat_inode_same(&dst, &est);
1312
1313         return cached_on_dev_null;
1314 }
1315
1316 static bool getenv_terminal_is_dumb(void) {
1317         const char *e;
1318
1319         e = getenv("TERM");
1320         if (!e)
1321                 return true;
1322
1323         return streq(e, "dumb");
1324 }
1325
1326 bool terminal_is_dumb(void) {
1327         if (!on_tty() && !on_dev_null())
1328                 return true;
1329
1330         return getenv_terminal_is_dumb();
1331 }
1332
1333 static ColorMode parse_systemd_colors(void) {
1334         const char *e;
1335         int r;
1336
1337         e = getenv("SYSTEMD_COLORS");
1338         if (!e)
1339                 return _COLOR_INVALID;
1340         if (streq(e, "16"))
1341                 return COLOR_16;
1342         if (streq(e, "256"))
1343                 return COLOR_256;
1344         r = parse_boolean(e);
1345         if (r >= 0)
1346                 return r > 0 ? COLOR_ON : COLOR_OFF;
1347         return _COLOR_INVALID;
1348 }
1349
1350 ColorMode get_color_mode(void) {
1351
1352         /* Returns the mode used to choose output colors. The possible modes are COLOR_OFF for no colors,
1353          * COLOR_16 for only the base 16 ANSI colors, COLOR_256 for more colors and COLOR_ON for unrestricted
1354          * color output. For that we check $SYSTEMD_COLORS first (which is the explicit way to
1355          * change the mode). If that didn't work we turn colors off unless we are on a TTY. And if we are on a TTY
1356          * we turn it off if $TERM is set to "dumb". There's one special tweak though: if we are PID 1 then we do not
1357          * check whether we are connected to a TTY, because we don't keep /dev/console open continuously due to fear
1358          * of SAK, and hence things are a bit weird. */
1359         ColorMode m;
1360
1361         if (cached_color_mode < 0) {
1362                 m = parse_systemd_colors();
1363                 if (m >= 0)
1364                         cached_color_mode = m;
1365                 else if (getenv("NO_COLOR"))
1366                         /* We only check for the presence of the variable; value is ignored. */
1367                         cached_color_mode = COLOR_OFF;
1368
1369                 else if (getpid_cached() == 1) {
1370                         /* PID1 outputs to the console without holding it open all the time.
1371                          *
1372                          * Note that the Linux console can only display 16 colors. We still enable 256 color
1373                          * mode even for PID1 output though (which typically goes to the Linux console),
1374                          * since the Linux console is able to parse the 256 color sequences and automatically
1375                          * map them to the closest color in the 16 color palette (since kernel 3.16). Doing
1376                          * 256 colors is nice for people who invoke systemd in a container or via a serial
1377                          * link or such, and use a true 256 color terminal to do so. */
1378                         if (getenv_terminal_is_dumb())
1379                                 cached_color_mode = COLOR_OFF;
1380                 } else {
1381                         if (terminal_is_dumb())
1382                                 cached_color_mode = COLOR_OFF;
1383                 }
1384
1385                 if (cached_color_mode < 0) {
1386                         /* We failed to figure out any reason to *disable* colors.
1387                          * Let's see how many colors we shall use. */
1388                         if (STRPTR_IN_SET(getenv("COLORTERM"),
1389                                           "truecolor",
1390                                           "24bit"))
1391                                 cached_color_mode = COLOR_24BIT;
1392                         else
1393                                 cached_color_mode = COLOR_256;
1394                 }
1395         }
1396
1397         return cached_color_mode;
1398 }
1399
1400 bool dev_console_colors_enabled(void) {
1401         _cleanup_free_ char *s = NULL;
1402         ColorMode m;
1403
1404         /* Returns true if we assume that color is supported on /dev/console.
1405          *
1406          * For that we first check if we explicitly got told to use colors or not, by checking $SYSTEMD_COLORS. If that
1407          * isn't set we check whether PID 1 has $TERM set, and if not, whether TERM is set on the kernel command
1408          * line. If we find $TERM set we assume color if it's not set to "dumb", similarly to how regular
1409          * colors_enabled() operates. */
1410
1411         m = parse_systemd_colors();
1412         if (m >= 0)
1413                 return m;
1414
1415         if (getenv("NO_COLOR"))
1416                 return false;
1417
1418         if (getenv_for_pid(1, "TERM", &s) <= 0)
1419                 (void) proc_cmdline_get_key("TERM", 0, &s);
1420
1421         return !streq_ptr(s, "dumb");
1422 }
1423
1424 bool underline_enabled(void) {
1425
1426         if (cached_underline_enabled < 0) {
1427
1428                 /* The Linux console doesn't support underlining, turn it off, but only there. */
1429
1430                 if (colors_enabled())
1431                         cached_underline_enabled = !streq_ptr(getenv("TERM"), "linux");
1432                 else
1433                         cached_underline_enabled = false;
1434         }
1435
1436         return cached_underline_enabled;
1437 }
1438
1439 int vt_default_utf8(void) {
1440         _cleanup_free_ char *b = NULL;
1441         int r;
1442
1443         /* Read the default VT UTF8 setting from the kernel */
1444
1445         r = read_one_line_file("/sys/module/vt/parameters/default_utf8", &b);
1446         if (r < 0)
1447                 return r;
1448
1449         return parse_boolean(b);
1450 }
1451
1452 int vt_reset_keyboard(int fd) {
1453         int kb;
1454
1455         /* If we can't read the default, then default to unicode. It's 2017 after all. */
1456         kb = vt_default_utf8() != 0 ? K_UNICODE : K_XLATE;
1457
1458         return RET_NERRNO(ioctl(fd, KDSKBMODE, kb));
1459 }
1460
1461 int vt_restore(int fd) {
1462
1463         static const struct vt_mode mode = {
1464                 .mode = VT_AUTO,
1465         };
1466
1467         int r, ret = 0;
1468
1469         assert(fd >= 0);
1470
1471         if (!isatty_safe(fd))
1472                 return log_debug_errno(errno, "Asked to restore the VT for an fd that does not refer to a terminal: %m");
1473
1474         if (ioctl(fd, KDSETMODE, KD_TEXT) < 0)
1475                 RET_GATHER(ret, log_debug_errno(errno, "Failed to set VT to text mode, ignoring: %m"));
1476
1477         r = vt_reset_keyboard(fd);
1478         if (r < 0)
1479                 RET_GATHER(ret, log_debug_errno(r, "Failed to reset keyboard mode, ignoring: %m"));
1480
1481         if (ioctl(fd, VT_SETMODE, &mode) < 0)
1482                 RET_GATHER(ret, log_debug_errno(errno, "Failed to set VT_AUTO mode, ignoring: %m"));
1483
1484         r = fchmod_and_chown(fd, TTY_MODE, 0, GID_INVALID);
1485         if (r < 0)
1486                 RET_GATHER(ret, log_debug_errno(r, "Failed to chmod()/chown() VT, ignoring: %m"));
1487
1488         return ret;
1489 }
1490
1491 int vt_release(int fd, bool restore) {
1492         assert(fd >= 0);
1493
1494         /* This function releases the VT by acknowledging the VT-switch signal
1495          * sent by the kernel and optionally reset the VT in text and auto
1496          * VT-switching modes. */
1497
1498         if (!isatty_safe(fd))
1499                 return log_debug_errno(errno, "Asked to release the VT for an fd that does not refer to a terminal: %m");
1500
1501         if (ioctl(fd, VT_RELDISP, 1) < 0)
1502                 return -errno;
1503
1504         if (restore)
1505                 return vt_restore(fd);
1506
1507         return 0;
1508 }
1509
1510 void get_log_colors(int priority, const char **on, const char **off, const char **highlight) {
1511         /* Note that this will initialize output variables only when there's something to output.
1512          * The caller must pre-initialize to "" or NULL as appropriate. */
1513
1514         if (priority <= LOG_ERR) {
1515                 if (on)
1516                         *on = ansi_highlight_red();
1517                 if (off)
1518                         *off = ansi_normal();
1519                 if (highlight)
1520                         *highlight = ansi_highlight();
1521
1522         } else if (priority <= LOG_WARNING) {
1523                 if (on)
1524                         *on = ansi_highlight_yellow();
1525                 if (off)
1526                         *off = ansi_normal();
1527                 if (highlight)
1528                         *highlight = ansi_highlight();
1529
1530         } else if (priority <= LOG_NOTICE) {
1531                 if (on)
1532                         *on = ansi_highlight();
1533                 if (off)
1534                         *off = ansi_normal();
1535                 if (highlight)
1536                         *highlight = ansi_highlight_red();
1537
1538         } else if (priority >= LOG_DEBUG) {
1539                 if (on)
1540                         *on = ansi_grey();
1541                 if (off)
1542                         *off = ansi_normal();
1543                 if (highlight)
1544                         *highlight = ansi_highlight_red();
1545         }
1546 }
1547
1548 int set_terminal_cursor_position(int fd, unsigned int row, unsigned int column) {
1549         int r;
1550         char cursor_position[STRLEN("\x1B[") + DECIMAL_STR_MAX(int) * 2 + STRLEN(";H") + 1];
1551
1552         assert(fd >= 0);
1553
1554         xsprintf(cursor_position, "\x1B[%u;%uH", row, column);
1555
1556         r = loop_write(fd, cursor_position, SIZE_MAX);
1557         if (r < 0)
1558                 return log_warning_errno(r, "Failed to set cursor position, ignoring: %m");
1559
1560         return 0;
1561 }
1562
1563 void termios_disable_echo(struct termios *termios) {
1564         assert(termios);
1565
1566         termios->c_lflag &= ~(ICANON|ECHO);
1567         termios->c_cc[VMIN] = 1;
1568         termios->c_cc[VTIME] = 0;
1569 }
1570
1571 typedef enum BackgroundColorState {
1572         BACKGROUND_TEXT,
1573         BACKGROUND_ESCAPE,
1574         BACKGROUND_BRACKET,
1575         BACKGROUND_FIRST_ONE,
1576         BACKGROUND_SECOND_ONE,
1577         BACKGROUND_SEMICOLON,
1578         BACKGROUND_R,
1579         BACKGROUND_G,
1580         BACKGROUND_B,
1581         BACKGROUND_RED,
1582         BACKGROUND_GREEN,
1583         BACKGROUND_BLUE,
1584         BACKGROUND_STRING_TERMINATOR,
1585 } BackgroundColorState;
1586
1587 typedef struct BackgroundColorContext {
1588         BackgroundColorState state;
1589         uint32_t red, green, blue;
1590         unsigned red_bits, green_bits, blue_bits;
1591 } BackgroundColorContext;
1592
1593 static int scan_background_color_response(
1594                 BackgroundColorContext *context,
1595                 const char *buf,
1596                 size_t size) {
1597
1598         assert(context);
1599         assert(buf || size == 0);
1600
1601         for (size_t i = 0; i < size; i++) {
1602                 char c = buf[i];
1603
1604                 switch (context->state) {
1605
1606                 case BACKGROUND_TEXT:
1607                         context->state = c == '\x1B' ? BACKGROUND_ESCAPE : BACKGROUND_TEXT;
1608                         break;
1609
1610                 case BACKGROUND_ESCAPE:
1611                         context->state = c == ']' ? BACKGROUND_BRACKET : BACKGROUND_TEXT;
1612                         break;
1613
1614                 case BACKGROUND_BRACKET:
1615                         context->state = c == '1' ? BACKGROUND_FIRST_ONE : BACKGROUND_TEXT;
1616                         break;
1617
1618                 case BACKGROUND_FIRST_ONE:
1619                         context->state = c == '1' ? BACKGROUND_SECOND_ONE : BACKGROUND_TEXT;
1620                         break;
1621
1622                 case BACKGROUND_SECOND_ONE:
1623                         context->state = c == ';' ? BACKGROUND_SEMICOLON : BACKGROUND_TEXT;
1624                         break;
1625
1626                 case BACKGROUND_SEMICOLON:
1627                         context->state = c == 'r' ? BACKGROUND_R : BACKGROUND_TEXT;
1628                         break;
1629
1630                 case BACKGROUND_R:
1631                         context->state = c == 'g' ? BACKGROUND_G : BACKGROUND_TEXT;
1632                         break;
1633
1634                 case BACKGROUND_G:
1635                         context->state = c == 'b' ? BACKGROUND_B : BACKGROUND_TEXT;
1636                         break;
1637
1638                 case BACKGROUND_B:
1639                         context->state = c == ':' ? BACKGROUND_RED : BACKGROUND_TEXT;
1640                         break;
1641
1642                 case BACKGROUND_RED:
1643                         if (c == '/')
1644                                 context->state = context->red_bits > 0 ? BACKGROUND_GREEN : BACKGROUND_TEXT;
1645                         else {
1646                                 int d = unhexchar(c);
1647                                 if (d < 0 || context->red_bits >= sizeof(context->red)*8)
1648                                         context->state = BACKGROUND_TEXT;
1649                                 else {
1650                                         context->red = (context->red << 4) | d;
1651                                         context->red_bits += 4;
1652                                 }
1653                         }
1654                         break;
1655
1656                 case BACKGROUND_GREEN:
1657                         if (c == '/')
1658                                 context->state = context->green_bits > 0 ? BACKGROUND_BLUE : BACKGROUND_TEXT;
1659                         else {
1660                                 int d = unhexchar(c);
1661                                 if (d < 0 || context->green_bits >= sizeof(context->green)*8)
1662                                         context->state = BACKGROUND_TEXT;
1663                                 else {
1664                                         context->green = (context->green << 4) | d;
1665                                         context->green_bits += 4;
1666                                 }
1667                         }
1668                         break;
1669
1670                 case BACKGROUND_BLUE:
1671                         if (c == '\x07') {
1672                                 if (context->blue_bits > 0)
1673                                         return 1; /* success! */
1674
1675                                 context->state = BACKGROUND_TEXT;
1676                         } else if (c == '\x1b')
1677                                 context->state = context->blue_bits > 0 ? BACKGROUND_STRING_TERMINATOR : BACKGROUND_TEXT;
1678                         else {
1679                                 int d = unhexchar(c);
1680                                 if (d < 0 || context->blue_bits >= sizeof(context->blue)*8)
1681                                         context->state = BACKGROUND_TEXT;
1682                                 else {
1683                                         context->blue = (context->blue << 4) | d;
1684                                         context->blue_bits += 4;
1685                                 }
1686                         }
1687                         break;
1688
1689                 case BACKGROUND_STRING_TERMINATOR:
1690                         if (c == '\\')
1691                                 return 1; /* success! */
1692
1693                         context->state = c == ']' ? BACKGROUND_ESCAPE : BACKGROUND_TEXT;
1694                         break;
1695
1696                 }
1697
1698                 /* Reset any colors we might have picked up */
1699                 if (IN_SET(context->state, BACKGROUND_TEXT, BACKGROUND_ESCAPE)) {
1700                         /* reset color */
1701                         context->red = context->green = context->blue = 0;
1702                         context->red_bits = context->green_bits = context->blue_bits = 0;
1703                 }
1704         }
1705
1706         return 0; /* all good, but not enough data yet */
1707 }
1708
1709 int get_default_background_color(double *ret_red, double *ret_green, double *ret_blue) {
1710         int r;
1711
1712         assert(ret_red);
1713         assert(ret_green);
1714         assert(ret_blue);
1715
1716         if (!colors_enabled())
1717                 return -EOPNOTSUPP;
1718
1719         if (!isatty(STDIN_FILENO) || !isatty(STDOUT_FILENO))
1720                 return -EOPNOTSUPP;
1721
1722         if (streq_ptr(getenv("TERM"), "linux")) {
1723                 /* Linux console is black */
1724                 *ret_red = *ret_green = *ret_blue = 0.0;
1725                 return 0;
1726         }
1727
1728         struct termios old_termios;
1729         if (tcgetattr(STDIN_FILENO, &old_termios) < 0)
1730                 return -errno;
1731
1732         struct termios new_termios = old_termios;
1733         termios_disable_echo(&new_termios);
1734
1735         if (tcsetattr(STDOUT_FILENO, TCSADRAIN, &new_termios) < 0)
1736                 return -errno;
1737
1738         r = loop_write(STDOUT_FILENO, "\x1B]11;?\x07", SIZE_MAX);
1739         if (r < 0)
1740                 goto finish;
1741
1742         usec_t end = usec_add(now(CLOCK_MONOTONIC), 100 * USEC_PER_MSEC);
1743         char buf[256];
1744         size_t buf_full = 0;
1745         BackgroundColorContext context = {};
1746
1747         for (;;) {
1748                 usec_t n = now(CLOCK_MONOTONIC);
1749
1750                 if (n >= end) {
1751                         r = -EOPNOTSUPP;
1752                         goto finish;
1753                 }
1754
1755                 r = fd_wait_for_event(STDIN_FILENO, POLLIN, usec_sub_unsigned(end, n));
1756                 if (r < 0)
1757                         goto finish;
1758                 if (r == 0) {
1759                         r = -EOPNOTSUPP;
1760                         goto finish;
1761                 }
1762
1763                 ssize_t l;
1764                 l = read(STDIN_FILENO, buf, sizeof(buf) - buf_full);
1765                 if (l < 0) {
1766                         r = -errno;
1767                         goto finish;
1768                 }
1769
1770                 buf_full += l;
1771                 assert(buf_full <= sizeof(buf));
1772
1773                 r = scan_background_color_response(&context, buf, buf_full);
1774                 if (r < 0)
1775                         goto finish;
1776                 if (r > 0) {
1777                         assert(context.red_bits > 0);
1778                         *ret_red = (double) context.red / ((UINT64_C(1) << context.red_bits) - 1);
1779                         assert(context.green_bits > 0);
1780                         *ret_green = (double) context.green / ((UINT64_C(1) << context.green_bits) - 1);
1781                         assert(context.blue_bits > 0);
1782                         *ret_blue = (double) context.blue / ((UINT64_C(1) << context.blue_bits) - 1);
1783                         r = 0;
1784                         goto finish;
1785                 }
1786         }
1787
1788 finish:
1789         (void) tcsetattr(STDOUT_FILENO, TCSADRAIN, &old_termios);
1790         return r;
1791 }