src/shared/ptyfwd.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 <signal.h>
   7 #include <stddef.h>
   8 #include <stdint.h>
   9 #include <stdlib.h>
  10 #include <string.h>
  11 #include <sys/epoll.h>
  12 #include <sys/ioctl.h>
  13 #include <sys/time.h>
  14 #include <termios.h>
  15 #include <unistd.h>
  16
  17 #include "sd-event.h"
  18
  19 #include "alloc-util.h"
  20 #include "errno-util.h"
  21 #include "fd-util.h"
  22 #include "log.h"
  23 #include "macro.h"
  24 #include "ptyfwd.h"
  25 #include "stat-util.h"
  26 #include "terminal-util.h"
  27 #include "time-util.h"
  28
  29 struct PTYForward {
  30         sd_event *event;
  31
  32         int input_fd;
  33         int output_fd;
  34         int master;
  35
  36         PTYForwardFlags flags;
  37
  38         sd_event_source *stdin_event_source;
  39         sd_event_source *stdout_event_source;
  40         sd_event_source *master_event_source;
  41
  42         sd_event_source *sigwinch_event_source;
  43
  44         struct termios saved_stdin_attr;
  45         struct termios saved_stdout_attr;
  46
  47         bool close_input_fd:1;
  48         bool close_output_fd:1;
  49
  50         bool saved_stdin:1;
  51         bool saved_stdout:1;
  52
  53         bool stdin_readable:1;
  54         bool stdin_hangup:1;
  55         bool stdout_writable:1;
  56         bool stdout_hangup:1;
  57         bool master_readable:1;
  58         bool master_writable:1;
  59         bool master_hangup:1;
  60
  61         bool read_from_master:1;
  62
  63         bool done:1;
  64         bool drain:1;
  65
  66         bool last_char_set:1;
  67         char last_char;
  68
  69         char in_buffer[LINE_MAX], out_buffer[LINE_MAX];
  70         size_t in_buffer_full, out_buffer_full;
  71
  72         usec_t escape_timestamp;
  73         unsigned escape_counter;
  74
  75         PTYForwardHandler handler;
  76         void *userdata;
  77 };
  78
  79 #define ESCAPE_USEC (1*USEC_PER_SEC)
  80
  81 static void pty_forward_disconnect(PTYForward *f) {
  82
  83         if (!f)
  84                 return;
  85
  86         f->stdin_event_source = sd_event_source_unref(f->stdin_event_source);
  87         f->stdout_event_source = sd_event_source_unref(f->stdout_event_source);
  88
  89         f->master_event_source = sd_event_source_unref(f->master_event_source);
  90         f->sigwinch_event_source = sd_event_source_unref(f->sigwinch_event_source);
  91         f->event = sd_event_unref(f->event);
  92
  93         if (f->output_fd >= 0) {
  94                 if (f->saved_stdout)
  95                         (void) tcsetattr(f->output_fd, TCSANOW, &f->saved_stdout_attr);
  96
  97                 /* STDIN/STDOUT should not be non-blocking normally, so let's reset it */
  98                 (void) fd_nonblock(f->output_fd, false);
  99                 if (f->close_output_fd)
 100                         f->output_fd = safe_close(f->output_fd);
 101         }
 102
 103         if (f->input_fd >= 0) {
 104                 if (f->saved_stdin)
 105                         (void) tcsetattr(f->input_fd, TCSANOW, &f->saved_stdin_attr);
 106
 107                 (void) fd_nonblock(f->input_fd, false);
 108                 if (f->close_input_fd)
 109                         f->input_fd = safe_close(f->input_fd);
 110         }
 111
 112         f->saved_stdout = f->saved_stdin = false;
 113 }
 114
 115 static int pty_forward_done(PTYForward *f, int rcode) {
 116         _cleanup_(sd_event_unrefp) sd_event *e = NULL;
 117         assert(f);
 118
 119         if (f->done)
 120                 return 0;
 121
 122         e = sd_event_ref(f->event);
 123
 124         f->done = true;
 125         pty_forward_disconnect(f);
 126
 127         if (f->handler)
 128                 return f->handler(f, rcode, f->userdata);
 129         else
 130                 return sd_event_exit(e, rcode < 0 ? EXIT_FAILURE : rcode);
 131 }
 132
 133 static bool look_for_escape(PTYForward *f, const char *buffer, size_t n) {
 134         const char *p;
 135
 136         assert(f);
 137         assert(buffer);
 138         assert(n > 0);
 139
 140         for (p = buffer; p < buffer + n; p++) {
 141
 142                 /* Check for ^] */
 143                 if (*p == 0x1D) {
 144                         usec_t nw = now(CLOCK_MONOTONIC);
 145
 146                         if (f->escape_counter == 0 || nw > f->escape_timestamp + ESCAPE_USEC) {
 147                                 f->escape_timestamp = nw;
 148                                 f->escape_counter = 1;
 149                         } else {
 150                                 (f->escape_counter)++;
 151
 152                                 if (f->escape_counter >= 3)
 153                                         return true;
 154                         }
 155                 } else {
 156                         f->escape_timestamp = 0;
 157                         f->escape_counter = 0;
 158                 }
 159         }
 160
 161         return false;
 162 }
 163
 164 static bool ignore_vhangup(PTYForward *f) {
 165         assert(f);
 166
 167         if (f->flags & PTY_FORWARD_IGNORE_VHANGUP)
 168                 return true;
 169
 170         if ((f->flags & PTY_FORWARD_IGNORE_INITIAL_VHANGUP) && !f->read_from_master)
 171                 return true;
 172
 173         return false;
 174 }
 175
 176 static bool drained(PTYForward *f) {
 177         int q = 0;
 178
 179         assert(f);
 180
 181         if (f->out_buffer_full > 0)
 182                 return false;
 183
 184         if (f->master_readable)
 185                 return false;
 186
 187         if (ioctl(f->master, TIOCINQ, &q) < 0)
 188                 log_debug_errno(errno, "TIOCINQ failed on master: %m");
 189         else if (q > 0)
 190                 return false;
 191
 192         if (ioctl(f->master, TIOCOUTQ, &q) < 0)
 193                 log_debug_errno(errno, "TIOCOUTQ failed on master: %m");
 194         else if (q > 0)
 195                 return false;
 196
 197         return true;
 198 }
 199
 200 static int shovel(PTYForward *f) {
 201         ssize_t k;
 202
 203         assert(f);
 204
 205         while ((f->stdin_readable && f->in_buffer_full <= 0) ||
 206                (f->master_writable && f->in_buffer_full > 0) ||
 207                (f->master_readable && f->out_buffer_full <= 0) ||
 208                (f->stdout_writable && f->out_buffer_full > 0)) {
 209
 210                 if (f->stdin_readable && f->in_buffer_full < LINE_MAX) {
 211
 212                         k = read(f->input_fd, f->in_buffer + f->in_buffer_full, LINE_MAX - f->in_buffer_full);
 213                         if (k < 0) {
 214
 215                                 if (errno == EAGAIN)
 216                                         f->stdin_readable = false;
 217                                 else if (errno == EIO || ERRNO_IS_DISCONNECT(errno)) {
 218                                         f->stdin_readable = false;
 219                                         f->stdin_hangup = true;
 220
 221                                         f->stdin_event_source = sd_event_source_unref(f->stdin_event_source);
 222                                 } else {
 223                                         log_error_errno(errno, "read(): %m");
 224                                         return pty_forward_done(f, -errno);
 225                                 }
 226                         } else if (k == 0) {
 227                                 /* EOF on stdin */
 228                                 f->stdin_readable = false;
 229                                 f->stdin_hangup = true;
 230
 231                                 f->stdin_event_source = sd_event_source_unref(f->stdin_event_source);
 232                         } else {
 233                                 /* Check if ^] has been pressed three times within one second. If we get this we quite
 234                                  * immediately. */
 235                                 if (look_for_escape(f, f->in_buffer + f->in_buffer_full, k))
 236                                         return pty_forward_done(f, -ECANCELED);
 237
 238                                 f->in_buffer_full += (size_t) k;
 239                         }
 240                 }
 241
 242                 if (f->master_writable && f->in_buffer_full > 0) {
 243
 244                         k = write(f->master, f->in_buffer, f->in_buffer_full);
 245                         if (k < 0) {
 246
 247                                 if (IN_SET(errno, EAGAIN, EIO))
 248                                         f->master_writable = false;
 249                                 else if (IN_SET(errno, EPIPE, ECONNRESET)) {
 250                                         f->master_writable = f->master_readable = false;
 251                                         f->master_hangup = true;
 252
 253                                         f->master_event_source = sd_event_source_unref(f->master_event_source);
 254                                 } else {
 255                                         log_error_errno(errno, "write(): %m");
 256                                         return pty_forward_done(f, -errno);
 257                                 }
 258                         } else {
 259                                 assert(f->in_buffer_full >= (size_t) k);
 260                                 memmove(f->in_buffer, f->in_buffer + k, f->in_buffer_full - k);
 261                                 f->in_buffer_full -= k;
 262                         }
 263                 }
 264
 265                 if (f->master_readable && f->out_buffer_full < LINE_MAX) {
 266
 267                         k = read(f->master, f->out_buffer + f->out_buffer_full, LINE_MAX - f->out_buffer_full);
 268                         if (k < 0) {
 269
 270                                 /* Note that EIO on the master device might be caused by vhangup() or
 271                                  * temporary closing of everything on the other side, we treat it like EAGAIN
 272                                  * here and try again, unless ignore_vhangup is off. */
 273
 274                                 if (errno == EAGAIN || (errno == EIO && ignore_vhangup(f)))
 275                                         f->master_readable = false;
 276                                 else if (IN_SET(errno, EPIPE, ECONNRESET, EIO)) {
 277                                         f->master_readable = f->master_writable = false;
 278                                         f->master_hangup = true;
 279
 280                                         f->master_event_source = sd_event_source_unref(f->master_event_source);
 281                                 } else {
 282                                         log_error_errno(errno, "read(): %m");
 283                                         return pty_forward_done(f, -errno);
 284                                 }
 285                         } else {
 286                                 f->read_from_master = true;
 287                                 f->out_buffer_full += (size_t) k;
 288                         }
 289                 }
 290
 291                 if (f->stdout_writable && f->out_buffer_full > 0) {
 292
 293                         k = write(f->output_fd, f->out_buffer, f->out_buffer_full);
 294                         if (k < 0) {
 295
 296                                 if (errno == EAGAIN)
 297                                         f->stdout_writable = false;
 298                                 else if (errno == EIO || ERRNO_IS_DISCONNECT(errno)) {
 299                                         f->stdout_writable = false;
 300                                         f->stdout_hangup = true;
 301                                         f->stdout_event_source = sd_event_source_unref(f->stdout_event_source);
 302                                 } else {
 303                                         log_error_errno(errno, "write(): %m");
 304                                         return pty_forward_done(f, -errno);
 305                                 }
 306
 307                         } else {
 308
 309                                 if (k > 0) {
 310                                         f->last_char = f->out_buffer[k-1];
 311                                         f->last_char_set = true;
 312                                 }
 313
 314                                 assert(f->out_buffer_full >= (size_t) k);
 315                                 memmove(f->out_buffer, f->out_buffer + k, f->out_buffer_full - k);
 316                                 f->out_buffer_full -= k;
 317                         }
 318                 }
 319         }
 320
 321         if (f->stdin_hangup || f->stdout_hangup || f->master_hangup) {
 322                 /* Exit the loop if any side hung up and if there's
 323                  * nothing more to write or nothing we could write. */
 324
 325                 if ((f->out_buffer_full <= 0 || f->stdout_hangup) &&
 326                     (f->in_buffer_full <= 0 || f->master_hangup))
 327                         return pty_forward_done(f, 0);
 328         }
 329
 330         /* If we were asked to drain, and there's nothing more to handle from the master, then call the callback
 331          * too. */
 332         if (f->drain && drained(f))
 333                 return pty_forward_done(f, 0);
 334
 335         return 0;
 336 }
 337
 338 static int on_master_event(sd_event_source *e, int fd, uint32_t revents, void *userdata) {
 339         PTYForward *f = ASSERT_PTR(userdata);
 340
 341         assert(e);
 342         assert(e == f->master_event_source);
 343         assert(fd >= 0);
 344         assert(fd == f->master);
 345
 346         if (revents & (EPOLLIN|EPOLLHUP))
 347                 f->master_readable = true;
 348
 349         if (revents & (EPOLLOUT|EPOLLHUP))
 350                 f->master_writable = true;
 351
 352         return shovel(f);
 353 }
 354
 355 static int on_stdin_event(sd_event_source *e, int fd, uint32_t revents, void *userdata) {
 356         PTYForward *f = ASSERT_PTR(userdata);
 357
 358         assert(e);
 359         assert(e == f->stdin_event_source);
 360         assert(fd >= 0);
 361         assert(fd == f->input_fd);
 362
 363         if (revents & (EPOLLIN|EPOLLHUP))
 364                 f->stdin_readable = true;
 365
 366         return shovel(f);
 367 }
 368
 369 static int on_stdout_event(sd_event_source *e, int fd, uint32_t revents, void *userdata) {
 370         PTYForward *f = ASSERT_PTR(userdata);
 371
 372         assert(e);
 373         assert(e == f->stdout_event_source);
 374         assert(fd >= 0);
 375         assert(fd == f->output_fd);
 376
 377         if (revents & (EPOLLOUT|EPOLLHUP))
 378                 f->stdout_writable = true;
 379
 380         return shovel(f);
 381 }
 382
 383 static int on_sigwinch_event(sd_event_source *e, const struct signalfd_siginfo *si, void *userdata) {
 384         PTYForward *f = ASSERT_PTR(userdata);
 385         struct winsize ws;
 386
 387         assert(e);
 388         assert(e == f->sigwinch_event_source);
 389
 390         /* The window size changed, let's forward that. */
 391         if (ioctl(f->output_fd, TIOCGWINSZ, &ws) >= 0)
 392                 (void) ioctl(f->master, TIOCSWINSZ, &ws);
 393
 394         return 0;
 395 }
 396
 397 int pty_forward_new(
 398                 sd_event *event,
 399                 int master,
 400                 PTYForwardFlags flags,
 401                 PTYForward **ret) {
 402
 403         _cleanup_(pty_forward_freep) PTYForward *f = NULL;
 404         struct winsize ws;
 405         int r;
 406
 407         f = new(PTYForward, 1);
 408         if (!f)
 409                 return -ENOMEM;
 410
 411         *f = (struct PTYForward) {
 412                 .flags = flags,
 413                 .master = -EBADF,
 414                 .input_fd = -EBADF,
 415                 .output_fd = -EBADF,
 416         };
 417
 418         if (event)
 419                 f->event = sd_event_ref(event);
 420         else {
 421                 r = sd_event_default(&f->event);
 422                 if (r < 0)
 423                         return r;
 424         }
 425
 426         if (FLAGS_SET(flags, PTY_FORWARD_READ_ONLY))
 427                 f->output_fd = STDOUT_FILENO;
 428         else {
 429                 /* If we shall be invoked in interactive mode, let's switch on non-blocking mode, so that we
 430                  * never end up staving one direction while we block on the other. However, let's be careful
 431                  * here and not turn on O_NONBLOCK for stdin/stdout directly, but of re-opened copies of
 432                  * them. This has two advantages: when we are killed abruptly the stdin/stdout fds won't be
 433                  * left in O_NONBLOCK state for the next process using them. In addition, if some process
 434                  * running in the background wants to continue writing to our stdout it can do so without
 435                  * being confused by O_NONBLOCK. */
 436
 437                 f->input_fd = fd_reopen(STDIN_FILENO, O_RDONLY|O_CLOEXEC|O_NOCTTY|O_NONBLOCK);
 438                 if (f->input_fd < 0) {
 439                         /* Handle failures gracefully, after all certain fd types cannot be reopened
 440                          * (sockets, …) */
 441                         log_debug_errno(f->input_fd, "Failed to reopen stdin, using original fd: %m");
 442
 443                         r = fd_nonblock(STDIN_FILENO, true);
 444                         if (r < 0)
 445                                 return r;
 446
 447                         f->input_fd = STDIN_FILENO;
 448                 } else
 449                         f->close_input_fd = true;
 450
 451                 f->output_fd = fd_reopen(STDOUT_FILENO, O_WRONLY|O_CLOEXEC|O_NOCTTY|O_NONBLOCK);
 452                 if (f->output_fd < 0) {
 453                         log_debug_errno(f->output_fd, "Failed to reopen stdout, using original fd: %m");
 454
 455                         r = fd_nonblock(STDOUT_FILENO, true);
 456                         if (r < 0)
 457                                 return r;
 458
 459                         f->output_fd = STDOUT_FILENO;
 460                 } else
 461                         f->close_output_fd = true;
 462         }
 463
 464         r = fd_nonblock(master, true);
 465         if (r < 0)
 466                 return r;
 467
 468         f->master = master;
 469
 470         if (ioctl(f->output_fd, TIOCGWINSZ, &ws) < 0)
 471                 /* If we can't get the resolution from the output fd, then use our internal, regular width/height,
 472                  * i.e. something derived from $COLUMNS and $LINES if set. */
 473                 ws = (struct winsize) {
 474                         .ws_row = lines(),
 475                         .ws_col = columns(),
 476                 };
 477
 478         (void) ioctl(master, TIOCSWINSZ, &ws);
 479
 480         if (!(flags & PTY_FORWARD_READ_ONLY)) {
 481                 int same;
 482
 483                 assert(f->input_fd >= 0);
 484
 485                 same = inode_same_at(f->input_fd, NULL, f->output_fd, NULL, AT_EMPTY_PATH);
 486                 if (same < 0)
 487                         return same;
 488
 489                 if (tcgetattr(f->input_fd, &f->saved_stdin_attr) >= 0) {
 490                         struct termios raw_stdin_attr;
 491
 492                         f->saved_stdin = true;
 493
 494                         raw_stdin_attr = f->saved_stdin_attr;
 495                         cfmakeraw(&raw_stdin_attr);
 496
 497                         if (!same)
 498                                 raw_stdin_attr.c_oflag = f->saved_stdin_attr.c_oflag;
 499
 500                         (void) tcsetattr(f->input_fd, TCSANOW, &raw_stdin_attr);
 501                 }
 502
 503                 if (!same && tcgetattr(f->output_fd, &f->saved_stdout_attr) >= 0) {
 504                         struct termios raw_stdout_attr;
 505
 506                         f->saved_stdout = true;
 507
 508                         raw_stdout_attr = f->saved_stdout_attr;
 509                         cfmakeraw(&raw_stdout_attr);
 510                         raw_stdout_attr.c_iflag = f->saved_stdout_attr.c_iflag;
 511                         raw_stdout_attr.c_lflag = f->saved_stdout_attr.c_lflag;
 512                         (void) tcsetattr(f->output_fd, TCSANOW, &raw_stdout_attr);
 513                 }
 514
 515                 r = sd_event_add_io(f->event, &f->stdin_event_source, f->input_fd, EPOLLIN|EPOLLET, on_stdin_event, f);
 516                 if (r < 0 && r != -EPERM)
 517                         return r;
 518
 519                 if (r >= 0)
 520                         (void) sd_event_source_set_description(f->stdin_event_source, "ptyfwd-stdin");
 521         }
 522
 523         r = sd_event_add_io(f->event, &f->stdout_event_source, f->output_fd, EPOLLOUT|EPOLLET, on_stdout_event, f);
 524         if (r == -EPERM)
 525                 /* stdout without epoll support. Likely redirected to regular file. */
 526                 f->stdout_writable = true;
 527         else if (r < 0)
 528                 return r;
 529         else
 530                 (void) sd_event_source_set_description(f->stdout_event_source, "ptyfwd-stdout");
 531
 532         r = sd_event_add_io(f->event, &f->master_event_source, master, EPOLLIN|EPOLLOUT|EPOLLET, on_master_event, f);
 533         if (r < 0)
 534                 return r;
 535
 536         (void) sd_event_source_set_description(f->master_event_source, "ptyfwd-master");
 537
 538         r = sd_event_add_signal(f->event, &f->sigwinch_event_source, SIGWINCH, on_sigwinch_event, f);
 539         if (r < 0)
 540                 return r;
 541
 542         (void) sd_event_source_set_description(f->sigwinch_event_source, "ptyfwd-sigwinch");
 543
 544         *ret = TAKE_PTR(f);
 545
 546         return 0;
 547 }
 548
 549 PTYForward *pty_forward_free(PTYForward *f) {
 550         pty_forward_disconnect(f);
 551         return mfree(f);
 552 }
 553
 554 int pty_forward_get_last_char(PTYForward *f, char *ch) {
 555         assert(f);
 556         assert(ch);
 557
 558         if (!f->last_char_set)
 559                 return -ENXIO;
 560
 561         *ch = f->last_char;
 562         return 0;
 563 }
 564
 565 int pty_forward_set_ignore_vhangup(PTYForward *f, bool b) {
 566         int r;
 567
 568         assert(f);
 569
 570         if (!!(f->flags & PTY_FORWARD_IGNORE_VHANGUP) == b)
 571                 return 0;
 572
 573         SET_FLAG(f->flags, PTY_FORWARD_IGNORE_VHANGUP, b);
 574
 575         if (!ignore_vhangup(f)) {
 576
 577                 /* We shall now react to vhangup()s? Let's check
 578                  * immediately if we might be in one */
 579
 580                 f->master_readable = true;
 581                 r = shovel(f);
 582                 if (r < 0)
 583                         return r;
 584         }
 585
 586         return 0;
 587 }
 588
 589 bool pty_forward_get_ignore_vhangup(PTYForward *f) {
 590         assert(f);
 591
 592         return !!(f->flags & PTY_FORWARD_IGNORE_VHANGUP);
 593 }
 594
 595 bool pty_forward_is_done(PTYForward *f) {
 596         assert(f);
 597
 598         return f->done;
 599 }
 600
 601 void pty_forward_set_handler(PTYForward *f, PTYForwardHandler cb, void *userdata) {
 602         assert(f);
 603
 604         f->handler = cb;
 605         f->userdata = userdata;
 606 }
 607
 608 bool pty_forward_drain(PTYForward *f) {
 609         assert(f);
 610
 611         /* Starts draining the forwarder. Specifically:
 612          *
 613          * - Returns true if there are no unprocessed bytes from the pty, false otherwise
 614          *
 615          * - Makes sure the handler function is called the next time the number of unprocessed bytes hits zero
 616          */
 617
 618         f->drain = true;
 619         return drained(f);
 620 }
 621
 622 int pty_forward_set_priority(PTYForward *f, int64_t priority) {
 623         int r;
 624         assert(f);
 625
 626         if (f->stdin_event_source) {
 627                 r = sd_event_source_set_priority(f->stdin_event_source, priority);
 628                 if (r < 0)
 629                         return r;
 630         }
 631
 632         r = sd_event_source_set_priority(f->stdout_event_source, priority);
 633         if (r < 0)
 634                 return r;
 635
 636         r = sd_event_source_set_priority(f->master_event_source, priority);
 637         if (r < 0)
 638                 return r;
 639
 640         r = sd_event_source_set_priority(f->sigwinch_event_source, priority);
 641         if (r < 0)
 642                 return r;
 643
 644         return 0;
 645 }
 646
 647 int pty_forward_set_width_height(PTYForward *f, unsigned width, unsigned height) {
 648         struct winsize ws;
 649
 650         assert(f);
 651
 652         if (width == UINT_MAX && height == UINT_MAX)
 653                 return 0; /* noop */
 654
 655         if (width != UINT_MAX &&
 656             (width == 0 || width > USHRT_MAX))
 657                 return -ERANGE;
 658
 659         if (height != UINT_MAX &&
 660             (height == 0 || height > USHRT_MAX))
 661                 return -ERANGE;
 662
 663         if (width == UINT_MAX || height == UINT_MAX) {
 664                 if (ioctl(f->master, TIOCGWINSZ, &ws) < 0)
 665                         return -errno;
 666
 667                 if (width != UINT_MAX)
 668                         ws.ws_col = width;
 669                 if (height != UINT_MAX)
 670                         ws.ws_row = height;
 671         } else
 672                 ws = (struct winsize) {
 673                         .ws_row = height,
 674                         .ws_col = width,
 675                 };
 676
 677         if (ioctl(f->master, TIOCSWINSZ, &ws) < 0)
 678                 return -errno;
 679
 680         /* Make sure we ignore SIGWINCH window size events from now on */
 681         f->sigwinch_event_source = sd_event_source_unref(f->sigwinch_event_source);
 682
 683         return 0;
 684 }