src/shared/ptyfwd.c

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2
   3 #include <errno.h>
   4 #include <limits.h>
   5 #include <signal.h>
   6 #include <stddef.h>
   7 #include <stdint.h>
   8 #include <stdlib.h>
   9 #include <string.h>
  10 #include <sys/epoll.h>
  11 #include <sys/ioctl.h>
  12 #include <sys/time.h>
  13 #include <termios.h>
  14 #include <unistd.h>
  15
  16 #include "sd-event.h"
  17
  18 #include "alloc-util.h"
  19 #include "fd-util.h"
  20 #include "log.h"
  21 #include "macro.h"
  22 #include "ptyfwd.h"
  23 #include "time-util.h"
  24
  25 struct PTYForward {
  26         sd_event *event;
  27
  28         int master;
  29
  30         PTYForwardFlags flags;
  31
  32         sd_event_source *stdin_event_source;
  33         sd_event_source *stdout_event_source;
  34         sd_event_source *master_event_source;
  35
  36         sd_event_source *sigwinch_event_source;
  37
  38         struct termios saved_stdin_attr;
  39         struct termios saved_stdout_attr;
  40
  41         bool saved_stdin:1;
  42         bool saved_stdout:1;
  43
  44         bool stdin_readable:1;
  45         bool stdin_hangup:1;
  46         bool stdout_writable:1;
  47         bool stdout_hangup:1;
  48         bool master_readable:1;
  49         bool master_writable:1;
  50         bool master_hangup:1;
  51
  52         bool read_from_master:1;
  53
  54         bool done:1;
  55         bool drain:1;
  56
  57         bool last_char_set:1;
  58         char last_char;
  59
  60         char in_buffer[LINE_MAX], out_buffer[LINE_MAX];
  61         size_t in_buffer_full, out_buffer_full;
  62
  63         usec_t escape_timestamp;
  64         unsigned escape_counter;
  65
  66         PTYForwardHandler handler;
  67         void *userdata;
  68 };
  69
  70 #define ESCAPE_USEC (1*USEC_PER_SEC)
  71
  72 static void pty_forward_disconnect(PTYForward *f) {
  73
  74         if (f) {
  75                 f->stdin_event_source = sd_event_source_unref(f->stdin_event_source);
  76                 f->stdout_event_source = sd_event_source_unref(f->stdout_event_source);
  77
  78                 f->master_event_source = sd_event_source_unref(f->master_event_source);
  79                 f->sigwinch_event_source = sd_event_source_unref(f->sigwinch_event_source);
  80                 f->event = sd_event_unref(f->event);
  81
  82                 if (f->saved_stdout)
  83                         tcsetattr(STDOUT_FILENO, TCSANOW, &f->saved_stdout_attr);
  84                 if (f->saved_stdin)
  85                         tcsetattr(STDIN_FILENO, TCSANOW, &f->saved_stdin_attr);
  86
  87                 f->saved_stdout = f->saved_stdin = false;
  88         }
  89
  90         /* STDIN/STDOUT should not be nonblocking normally, so let's unconditionally reset it */
  91         fd_nonblock(STDIN_FILENO, false);
  92         fd_nonblock(STDOUT_FILENO, false);
  93 }
  94
  95 static int pty_forward_done(PTYForward *f, int rcode) {
  96         _cleanup_(sd_event_unrefp) sd_event *e = NULL;
  97         assert(f);
  98
  99         if (f->done)
 100                 return 0;
 101
 102         e = sd_event_ref(f->event);
 103
 104         f->done = true;
 105         pty_forward_disconnect(f);
 106
 107         if (f->handler)
 108                 return f->handler(f, rcode, f->userdata);
 109         else
 110                 return sd_event_exit(e, rcode < 0 ? EXIT_FAILURE : rcode);
 111 }
 112
 113 static bool look_for_escape(PTYForward *f, const char *buffer, size_t n) {
 114         const char *p;
 115
 116         assert(f);
 117         assert(buffer);
 118         assert(n > 0);
 119
 120         for (p = buffer; p < buffer + n; p++) {
 121
 122                 /* Check for ^] */
 123                 if (*p == 0x1D) {
 124                         usec_t nw = now(CLOCK_MONOTONIC);
 125
 126                         if (f->escape_counter == 0 || nw > f->escape_timestamp + ESCAPE_USEC)  {
 127                                 f->escape_timestamp = nw;
 128                                 f->escape_counter = 1;
 129                         } else {
 130                                 (f->escape_counter)++;
 131
 132                                 if (f->escape_counter >= 3)
 133                                         return true;
 134                         }
 135                 } else {
 136                         f->escape_timestamp = 0;
 137                         f->escape_counter = 0;
 138                 }
 139         }
 140
 141         return false;
 142 }
 143
 144 static bool ignore_vhangup(PTYForward *f) {
 145         assert(f);
 146
 147         if (f->flags & PTY_FORWARD_IGNORE_VHANGUP)
 148                 return true;
 149
 150         if ((f->flags & PTY_FORWARD_IGNORE_INITIAL_VHANGUP) && !f->read_from_master)
 151                 return true;
 152
 153         return false;
 154 }
 155
 156 static bool drained(PTYForward *f) {
 157         int q = 0;
 158
 159         assert(f);
 160
 161         if (f->out_buffer_full > 0)
 162                 return false;
 163
 164         if (f->master_readable)
 165                 return false;
 166
 167         if (ioctl(f->master, TIOCINQ, &q) < 0)
 168                 log_debug_errno(errno, "TIOCINQ failed on master: %m");
 169         else if (q > 0)
 170                 return false;
 171
 172         if (ioctl(f->master, TIOCOUTQ, &q) < 0)
 173                 log_debug_errno(errno, "TIOCOUTQ failed on master: %m");
 174         else if (q > 0)
 175                 return false;
 176
 177         return true;
 178 }
 179
 180 static int shovel(PTYForward *f) {
 181         ssize_t k;
 182
 183         assert(f);
 184
 185         while ((f->stdin_readable && f->in_buffer_full <= 0) ||
 186                (f->master_writable && f->in_buffer_full > 0) ||
 187                (f->master_readable && f->out_buffer_full <= 0) ||
 188                (f->stdout_writable && f->out_buffer_full > 0)) {
 189
 190                 if (f->stdin_readable && f->in_buffer_full < LINE_MAX) {
 191
 192                         k = read(STDIN_FILENO, f->in_buffer + f->in_buffer_full, LINE_MAX - f->in_buffer_full);
 193                         if (k < 0) {
 194
 195                                 if (errno == EAGAIN)
 196                                         f->stdin_readable = false;
 197                                 else if (IN_SET(errno, EIO, EPIPE, ECONNRESET)) {
 198                                         f->stdin_readable = false;
 199                                         f->stdin_hangup = true;
 200
 201                                         f->stdin_event_source = sd_event_source_unref(f->stdin_event_source);
 202                                 } else {
 203                                         log_error_errno(errno, "read(): %m");
 204                                         return pty_forward_done(f, -errno);
 205                                 }
 206                         } else if (k == 0) {
 207                                 /* EOF on stdin */
 208                                 f->stdin_readable = false;
 209                                 f->stdin_hangup = true;
 210
 211                                 f->stdin_event_source = sd_event_source_unref(f->stdin_event_source);
 212                         } else  {
 213                                 /* Check if ^] has been pressed three times within one second. If we get this we quite
 214                                  * immediately. */
 215                                 if (look_for_escape(f, f->in_buffer + f->in_buffer_full, k))
 216                                         return pty_forward_done(f, -ECANCELED);
 217
 218                                 f->in_buffer_full += (size_t) k;
 219                         }
 220                 }
 221
 222                 if (f->master_writable && f->in_buffer_full > 0) {
 223
 224                         k = write(f->master, f->in_buffer, f->in_buffer_full);
 225                         if (k < 0) {
 226
 227                                 if (IN_SET(errno, EAGAIN, EIO))
 228                                         f->master_writable = false;
 229                                 else if (IN_SET(errno, EPIPE, ECONNRESET)) {
 230                                         f->master_writable = f->master_readable = false;
 231                                         f->master_hangup = true;
 232
 233                                         f->master_event_source = sd_event_source_unref(f->master_event_source);
 234                                 } else {
 235                                         log_error_errno(errno, "write(): %m");
 236                                         return pty_forward_done(f, -errno);
 237                                 }
 238                         } else {
 239                                 assert(f->in_buffer_full >= (size_t) k);
 240                                 memmove(f->in_buffer, f->in_buffer + k, f->in_buffer_full - k);
 241                                 f->in_buffer_full -= k;
 242                         }
 243                 }
 244
 245                 if (f->master_readable && f->out_buffer_full < LINE_MAX) {
 246
 247                         k = read(f->master, f->out_buffer + f->out_buffer_full, LINE_MAX - f->out_buffer_full);
 248                         if (k < 0) {
 249
 250                                 /* Note that EIO on the master device
 251                                  * might be caused by vhangup() or
 252                                  * temporary closing of everything on
 253                                  * the other side, we treat it like
 254                                  * EAGAIN here and try again, unless
 255                                  * ignore_vhangup is off. */
 256
 257                                 if (errno == EAGAIN || (errno == EIO && ignore_vhangup(f)))
 258                                         f->master_readable = false;
 259                                 else if (IN_SET(errno, EPIPE, ECONNRESET, EIO)) {
 260                                         f->master_readable = f->master_writable = false;
 261                                         f->master_hangup = true;
 262
 263                                         f->master_event_source = sd_event_source_unref(f->master_event_source);
 264                                 } else {
 265                                         log_error_errno(errno, "read(): %m");
 266                                         return pty_forward_done(f, -errno);
 267                                 }
 268                         }  else {
 269                                 f->read_from_master = true;
 270                                 f->out_buffer_full += (size_t) k;
 271                         }
 272                 }
 273
 274                 if (f->stdout_writable && f->out_buffer_full > 0) {
 275
 276                         k = write(STDOUT_FILENO, f->out_buffer, f->out_buffer_full);
 277                         if (k < 0) {
 278
 279                                 if (errno == EAGAIN)
 280                                         f->stdout_writable = false;
 281                                 else if (IN_SET(errno, EIO, EPIPE, ECONNRESET)) {
 282                                         f->stdout_writable = false;
 283                                         f->stdout_hangup = true;
 284                                         f->stdout_event_source = sd_event_source_unref(f->stdout_event_source);
 285                                 } else {
 286                                         log_error_errno(errno, "write(): %m");
 287                                         return pty_forward_done(f, -errno);
 288                                 }
 289
 290                         } else {
 291
 292                                 if (k > 0) {
 293                                         f->last_char = f->out_buffer[k-1];
 294                                         f->last_char_set = true;
 295                                 }
 296
 297                                 assert(f->out_buffer_full >= (size_t) k);
 298                                 memmove(f->out_buffer, f->out_buffer + k, f->out_buffer_full - k);
 299                                 f->out_buffer_full -= k;
 300                         }
 301                 }
 302         }
 303
 304         if (f->stdin_hangup || f->stdout_hangup || f->master_hangup) {
 305                 /* Exit the loop if any side hung up and if there's
 306                  * nothing more to write or nothing we could write. */
 307
 308                 if ((f->out_buffer_full <= 0 || f->stdout_hangup) &&
 309                     (f->in_buffer_full <= 0 || f->master_hangup))
 310                         return pty_forward_done(f, 0);
 311         }
 312
 313         /* If we were asked to drain, and there's nothing more to handle from the master, then call the callback
 314          * too. */
 315         if (f->drain && drained(f))
 316                 return pty_forward_done(f, 0);
 317
 318         return 0;
 319 }
 320
 321 static int on_master_event(sd_event_source *e, int fd, uint32_t revents, void *userdata) {
 322         PTYForward *f = userdata;
 323
 324         assert(f);
 325         assert(e);
 326         assert(e == f->master_event_source);
 327         assert(fd >= 0);
 328         assert(fd == f->master);
 329
 330         if (revents & (EPOLLIN|EPOLLHUP))
 331                 f->master_readable = true;
 332
 333         if (revents & (EPOLLOUT|EPOLLHUP))
 334                 f->master_writable = true;
 335
 336         return shovel(f);
 337 }
 338
 339 static int on_stdin_event(sd_event_source *e, int fd, uint32_t revents, void *userdata) {
 340         PTYForward *f = userdata;
 341
 342         assert(f);
 343         assert(e);
 344         assert(e == f->stdin_event_source);
 345         assert(fd >= 0);
 346         assert(fd == STDIN_FILENO);
 347
 348         if (revents & (EPOLLIN|EPOLLHUP))
 349                 f->stdin_readable = true;
 350
 351         return shovel(f);
 352 }
 353
 354 static int on_stdout_event(sd_event_source *e, int fd, uint32_t revents, void *userdata) {
 355         PTYForward *f = userdata;
 356
 357         assert(f);
 358         assert(e);
 359         assert(e == f->stdout_event_source);
 360         assert(fd >= 0);
 361         assert(fd == STDOUT_FILENO);
 362
 363         if (revents & (EPOLLOUT|EPOLLHUP))
 364                 f->stdout_writable = true;
 365
 366         return shovel(f);
 367 }
 368
 369 static int on_sigwinch_event(sd_event_source *e, const struct signalfd_siginfo *si, void *userdata) {
 370         PTYForward *f = userdata;
 371         struct winsize ws;
 372
 373         assert(f);
 374         assert(e);
 375         assert(e == f->sigwinch_event_source);
 376
 377         /* The window size changed, let's forward that. */
 378         if (ioctl(STDOUT_FILENO, TIOCGWINSZ, &ws) >= 0)
 379                 (void) ioctl(f->master, TIOCSWINSZ, &ws);
 380
 381         return 0;
 382 }
 383
 384 int pty_forward_new(
 385                 sd_event *event,
 386                 int master,
 387                 PTYForwardFlags flags,
 388                 PTYForward **ret) {
 389
 390         _cleanup_(pty_forward_freep) PTYForward *f = NULL;
 391         struct winsize ws;
 392         int r;
 393
 394         f = new0(PTYForward, 1);
 395         if (!f)
 396                 return -ENOMEM;
 397
 398         f->flags = flags;
 399
 400         if (event)
 401                 f->event = sd_event_ref(event);
 402         else {
 403                 r = sd_event_default(&f->event);
 404                 if (r < 0)
 405                         return r;
 406         }
 407
 408         if (!(flags & PTY_FORWARD_READ_ONLY)) {
 409                 r = fd_nonblock(STDIN_FILENO, true);
 410                 if (r < 0)
 411                         return r;
 412
 413                 r = fd_nonblock(STDOUT_FILENO, true);
 414                 if (r < 0)
 415                         return r;
 416         }
 417
 418         r = fd_nonblock(master, true);
 419         if (r < 0)
 420                 return r;
 421
 422         f->master = master;
 423
 424         if (ioctl(STDOUT_FILENO, TIOCGWINSZ, &ws) >= 0)
 425                 (void) ioctl(master, TIOCSWINSZ, &ws);
 426
 427         if (!(flags & PTY_FORWARD_READ_ONLY)) {
 428                 if (tcgetattr(STDIN_FILENO, &f->saved_stdin_attr) >= 0) {
 429                         struct termios raw_stdin_attr;
 430
 431                         f->saved_stdin = true;
 432
 433                         raw_stdin_attr = f->saved_stdin_attr;
 434                         cfmakeraw(&raw_stdin_attr);
 435                         raw_stdin_attr.c_oflag = f->saved_stdin_attr.c_oflag;
 436                         tcsetattr(STDIN_FILENO, TCSANOW, &raw_stdin_attr);
 437                 }
 438
 439                 if (tcgetattr(STDOUT_FILENO, &f->saved_stdout_attr) >= 0) {
 440                         struct termios raw_stdout_attr;
 441
 442                         f->saved_stdout = true;
 443
 444                         raw_stdout_attr = f->saved_stdout_attr;
 445                         cfmakeraw(&raw_stdout_attr);
 446                         raw_stdout_attr.c_iflag = f->saved_stdout_attr.c_iflag;
 447                         raw_stdout_attr.c_lflag = f->saved_stdout_attr.c_lflag;
 448                         tcsetattr(STDOUT_FILENO, TCSANOW, &raw_stdout_attr);
 449                 }
 450
 451                 r = sd_event_add_io(f->event, &f->stdin_event_source, STDIN_FILENO, EPOLLIN|EPOLLET, on_stdin_event, f);
 452                 if (r < 0 && r != -EPERM)
 453                         return r;
 454
 455                 if (r >= 0)
 456                         (void) sd_event_source_set_description(f->stdin_event_source, "ptyfwd-stdin");
 457         }
 458
 459         r = sd_event_add_io(f->event, &f->stdout_event_source, STDOUT_FILENO, EPOLLOUT|EPOLLET, on_stdout_event, f);
 460         if (r == -EPERM)
 461                 /* stdout without epoll support. Likely redirected to regular file. */
 462                 f->stdout_writable = true;
 463         else if (r < 0)
 464                 return r;
 465         else
 466                 (void) sd_event_source_set_description(f->stdout_event_source, "ptyfwd-stdout");
 467
 468         r = sd_event_add_io(f->event, &f->master_event_source, master, EPOLLIN|EPOLLOUT|EPOLLET, on_master_event, f);
 469         if (r < 0)
 470                 return r;
 471
 472         (void) sd_event_source_set_description(f->master_event_source, "ptyfwd-master");
 473
 474         r = sd_event_add_signal(f->event, &f->sigwinch_event_source, SIGWINCH, on_sigwinch_event, f);
 475         if (r < 0)
 476                 return r;
 477
 478         (void) sd_event_source_set_description(f->sigwinch_event_source, "ptyfwd-sigwinch");
 479
 480         *ret = TAKE_PTR(f);
 481
 482         return 0;
 483 }
 484
 485 PTYForward *pty_forward_free(PTYForward *f) {
 486         pty_forward_disconnect(f);
 487         return mfree(f);
 488 }
 489
 490 int pty_forward_get_last_char(PTYForward *f, char *ch) {
 491         assert(f);
 492         assert(ch);
 493
 494         if (!f->last_char_set)
 495                 return -ENXIO;
 496
 497         *ch = f->last_char;
 498         return 0;
 499 }
 500
 501 int pty_forward_set_ignore_vhangup(PTYForward *f, bool b) {
 502         int r;
 503
 504         assert(f);
 505
 506         if (!!(f->flags & PTY_FORWARD_IGNORE_VHANGUP) == b)
 507                 return 0;
 508
 509         SET_FLAG(f->flags, PTY_FORWARD_IGNORE_VHANGUP, b);
 510
 511         if (!ignore_vhangup(f)) {
 512
 513                 /* We shall now react to vhangup()s? Let's check
 514                  * immediately if we might be in one */
 515
 516                 f->master_readable = true;
 517                 r = shovel(f);
 518                 if (r < 0)
 519                         return r;
 520         }
 521
 522         return 0;
 523 }
 524
 525 bool pty_forward_get_ignore_vhangup(PTYForward *f) {
 526         assert(f);
 527
 528         return !!(f->flags & PTY_FORWARD_IGNORE_VHANGUP);
 529 }
 530
 531 bool pty_forward_is_done(PTYForward *f) {
 532         assert(f);
 533
 534         return f->done;
 535 }
 536
 537 void pty_forward_set_handler(PTYForward *f, PTYForwardHandler cb, void *userdata) {
 538         assert(f);
 539
 540         f->handler = cb;
 541         f->userdata = userdata;
 542 }
 543
 544 bool pty_forward_drain(PTYForward *f) {
 545         assert(f);
 546
 547         /* Starts draining the forwarder. Specifically:
 548          *
 549          * - Returns true if there are no unprocessed bytes from the pty, false otherwise
 550          *
 551          * - Makes sure the handler function is called the next time the number of unprocessed bytes hits zero
 552          */
 553
 554         f->drain = true;
 555         return drained(f);
 556 }
 557
 558 int pty_forward_set_priority(PTYForward *f, int64_t priority) {
 559         int r;
 560         assert(f);
 561
 562         r = sd_event_source_set_priority(f->stdin_event_source, priority);
 563         if (r < 0)
 564                 return r;
 565
 566         r = sd_event_source_set_priority(f->stdout_event_source, priority);
 567         if (r < 0)
 568                 return r;
 569
 570         r = sd_event_source_set_priority(f->master_event_source, priority);
 571         if (r < 0)
 572                 return r;
 573
 574         r = sd_event_source_set_priority(f->sigwinch_event_source, priority);
 575         if (r < 0)
 576                 return r;
 577
 578         return 0;
 579 }