src/shared/ptyfwd.c

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2 /***
   3   Copyright 2010-2013 Lennart Poettering
   4 ***/
   5
   6 #include <errno.h>
   7 #include <limits.h>
   8 #include <signal.h>
   9 #include <stddef.h>
  10 #include <stdint.h>
  11 #include <stdlib.h>
  12 #include <string.h>
  13 #include <sys/epoll.h>
  14 #include <sys/ioctl.h>
  15 #include <sys/time.h>
  16 #include <termios.h>
  17 #include <unistd.h>
  18
  19 #include "sd-event.h"
  20
  21 #include "alloc-util.h"
  22 #include "fd-util.h"
  23 #include "log.h"
  24 #include "macro.h"
  25 #include "ptyfwd.h"
  26 #include "time-util.h"
  27
  28 struct PTYForward {
  29         sd_event *event;
  30
  31         int master;
  32
  33         PTYForwardFlags flags;
  34
  35         sd_event_source *stdin_event_source;
  36         sd_event_source *stdout_event_source;
  37         sd_event_source *master_event_source;
  38
  39         sd_event_source *sigwinch_event_source;
  40
  41         struct termios saved_stdin_attr;
  42         struct termios saved_stdout_attr;
  43
  44         bool saved_stdin:1;
  45         bool saved_stdout:1;
  46
  47         bool stdin_readable:1;
  48         bool stdin_hangup:1;
  49         bool stdout_writable:1;
  50         bool stdout_hangup:1;
  51         bool master_readable:1;
  52         bool master_writable:1;
  53         bool master_hangup:1;
  54
  55         bool read_from_master:1;
  56
  57         bool done:1;
  58         bool drain:1;
  59
  60         bool last_char_set:1;
  61         char last_char;
  62
  63         char in_buffer[LINE_MAX], out_buffer[LINE_MAX];
  64         size_t in_buffer_full, out_buffer_full;
  65
  66         usec_t escape_timestamp;
  67         unsigned escape_counter;
  68
  69         PTYForwardHandler handler;
  70         void *userdata;
  71 };
  72
  73 #define ESCAPE_USEC (1*USEC_PER_SEC)
  74
  75 static void pty_forward_disconnect(PTYForward *f) {
  76
  77         if (f) {
  78                 f->stdin_event_source = sd_event_source_unref(f->stdin_event_source);
  79                 f->stdout_event_source = sd_event_source_unref(f->stdout_event_source);
  80
  81                 f->master_event_source = sd_event_source_unref(f->master_event_source);
  82                 f->sigwinch_event_source = sd_event_source_unref(f->sigwinch_event_source);
  83                 f->event = sd_event_unref(f->event);
  84
  85                 if (f->saved_stdout)
  86                         tcsetattr(STDOUT_FILENO, TCSANOW, &f->saved_stdout_attr);
  87                 if (f->saved_stdin)
  88                         tcsetattr(STDIN_FILENO, TCSANOW, &f->saved_stdin_attr);
  89
  90                 f->saved_stdout = f->saved_stdin = false;
  91         }
  92
  93         /* STDIN/STDOUT should not be nonblocking normally, so let's unconditionally reset it */
  94         fd_nonblock(STDIN_FILENO, false);
  95         fd_nonblock(STDOUT_FILENO, false);
  96 }
  97
  98 static int pty_forward_done(PTYForward *f, int rcode) {
  99         _cleanup_(sd_event_unrefp) sd_event *e = NULL;
 100         assert(f);
 101
 102         if (f->done)
 103                 return 0;
 104
 105         e = sd_event_ref(f->event);
 106
 107         f->done = true;
 108         pty_forward_disconnect(f);
 109
 110         if (f->handler)
 111                 return f->handler(f, rcode, f->userdata);
 112         else
 113                 return sd_event_exit(e, rcode < 0 ? EXIT_FAILURE : rcode);
 114 }
 115
 116 static bool look_for_escape(PTYForward *f, const char *buffer, size_t n) {
 117         const char *p;
 118
 119         assert(f);
 120         assert(buffer);
 121         assert(n > 0);
 122
 123         for (p = buffer; p < buffer + n; p++) {
 124
 125                 /* Check for ^] */
 126                 if (*p == 0x1D) {
 127                         usec_t nw = now(CLOCK_MONOTONIC);
 128
 129                         if (f->escape_counter == 0 || nw > f->escape_timestamp + ESCAPE_USEC)  {
 130                                 f->escape_timestamp = nw;
 131                                 f->escape_counter = 1;
 132                         } else {
 133                                 (f->escape_counter)++;
 134
 135                                 if (f->escape_counter >= 3)
 136                                         return true;
 137                         }
 138                 } else {
 139                         f->escape_timestamp = 0;
 140                         f->escape_counter = 0;
 141                 }
 142         }
 143
 144         return false;
 145 }
 146
 147 static bool ignore_vhangup(PTYForward *f) {
 148         assert(f);
 149
 150         if (f->flags & PTY_FORWARD_IGNORE_VHANGUP)
 151                 return true;
 152
 153         if ((f->flags & PTY_FORWARD_IGNORE_INITIAL_VHANGUP) && !f->read_from_master)
 154                 return true;
 155
 156         return false;
 157 }
 158
 159 static bool drained(PTYForward *f) {
 160         int q = 0;
 161
 162         assert(f);
 163
 164         if (f->out_buffer_full > 0)
 165                 return false;
 166
 167         if (f->master_readable)
 168                 return false;
 169
 170         if (ioctl(f->master, TIOCINQ, &q) < 0)
 171                 log_debug_errno(errno, "TIOCINQ failed on master: %m");
 172         else if (q > 0)
 173                 return false;
 174
 175         if (ioctl(f->master, TIOCOUTQ, &q) < 0)
 176                 log_debug_errno(errno, "TIOCOUTQ failed on master: %m");
 177         else if (q > 0)
 178                 return false;
 179
 180         return true;
 181 }
 182
 183 static int shovel(PTYForward *f) {
 184         ssize_t k;
 185
 186         assert(f);
 187
 188         while ((f->stdin_readable && f->in_buffer_full <= 0) ||
 189                (f->master_writable && f->in_buffer_full > 0) ||
 190                (f->master_readable && f->out_buffer_full <= 0) ||
 191                (f->stdout_writable && f->out_buffer_full > 0)) {
 192
 193                 if (f->stdin_readable && f->in_buffer_full < LINE_MAX) {
 194
 195                         k = read(STDIN_FILENO, f->in_buffer + f->in_buffer_full, LINE_MAX - f->in_buffer_full);
 196                         if (k < 0) {
 197
 198                                 if (errno == EAGAIN)
 199                                         f->stdin_readable = false;
 200                                 else if (IN_SET(errno, EIO, EPIPE, ECONNRESET)) {
 201                                         f->stdin_readable = false;
 202                                         f->stdin_hangup = true;
 203
 204                                         f->stdin_event_source = sd_event_source_unref(f->stdin_event_source);
 205                                 } else {
 206                                         log_error_errno(errno, "read(): %m");
 207                                         return pty_forward_done(f, -errno);
 208                                 }
 209                         } else if (k == 0) {
 210                                 /* EOF on stdin */
 211                                 f->stdin_readable = false;
 212                                 f->stdin_hangup = true;
 213
 214                                 f->stdin_event_source = sd_event_source_unref(f->stdin_event_source);
 215                         } else  {
 216                                 /* Check if ^] has been pressed three times within one second. If we get this we quite
 217                                  * immediately. */
 218                                 if (look_for_escape(f, f->in_buffer + f->in_buffer_full, k))
 219                                         return pty_forward_done(f, -ECANCELED);
 220
 221                                 f->in_buffer_full += (size_t) k;
 222                         }
 223                 }
 224
 225                 if (f->master_writable && f->in_buffer_full > 0) {
 226
 227                         k = write(f->master, f->in_buffer, f->in_buffer_full);
 228                         if (k < 0) {
 229
 230                                 if (IN_SET(errno, EAGAIN, EIO))
 231                                         f->master_writable = false;
 232                                 else if (IN_SET(errno, EPIPE, ECONNRESET)) {
 233                                         f->master_writable = f->master_readable = false;
 234                                         f->master_hangup = true;
 235
 236                                         f->master_event_source = sd_event_source_unref(f->master_event_source);
 237                                 } else {
 238                                         log_error_errno(errno, "write(): %m");
 239                                         return pty_forward_done(f, -errno);
 240                                 }
 241                         } else {
 242                                 assert(f->in_buffer_full >= (size_t) k);
 243                                 memmove(f->in_buffer, f->in_buffer + k, f->in_buffer_full - k);
 244                                 f->in_buffer_full -= k;
 245                         }
 246                 }
 247
 248                 if (f->master_readable && f->out_buffer_full < LINE_MAX) {
 249
 250                         k = read(f->master, f->out_buffer + f->out_buffer_full, LINE_MAX - f->out_buffer_full);
 251                         if (k < 0) {
 252
 253                                 /* Note that EIO on the master device
 254                                  * might be caused by vhangup() or
 255                                  * temporary closing of everything on
 256                                  * the other side, we treat it like
 257                                  * EAGAIN here and try again, unless
 258                                  * ignore_vhangup is off. */
 259
 260                                 if (errno == EAGAIN || (errno == EIO && ignore_vhangup(f)))
 261                                         f->master_readable = false;
 262                                 else if (IN_SET(errno, EPIPE, ECONNRESET, EIO)) {
 263                                         f->master_readable = f->master_writable = false;
 264                                         f->master_hangup = true;
 265
 266                                         f->master_event_source = sd_event_source_unref(f->master_event_source);
 267                                 } else {
 268                                         log_error_errno(errno, "read(): %m");
 269                                         return pty_forward_done(f, -errno);
 270                                 }
 271                         }  else {
 272                                 f->read_from_master = true;
 273                                 f->out_buffer_full += (size_t) k;
 274                         }
 275                 }
 276
 277                 if (f->stdout_writable && f->out_buffer_full > 0) {
 278
 279                         k = write(STDOUT_FILENO, f->out_buffer, f->out_buffer_full);
 280                         if (k < 0) {
 281
 282                                 if (errno == EAGAIN)
 283                                         f->stdout_writable = false;
 284                                 else if (IN_SET(errno, EIO, EPIPE, ECONNRESET)) {
 285                                         f->stdout_writable = false;
 286                                         f->stdout_hangup = true;
 287                                         f->stdout_event_source = sd_event_source_unref(f->stdout_event_source);
 288                                 } else {
 289                                         log_error_errno(errno, "write(): %m");
 290                                         return pty_forward_done(f, -errno);
 291                                 }
 292
 293                         } else {
 294
 295                                 if (k > 0) {
 296                                         f->last_char = f->out_buffer[k-1];
 297                                         f->last_char_set = true;
 298                                 }
 299
 300                                 assert(f->out_buffer_full >= (size_t) k);
 301                                 memmove(f->out_buffer, f->out_buffer + k, f->out_buffer_full - k);
 302                                 f->out_buffer_full -= k;
 303                         }
 304                 }
 305         }
 306
 307         if (f->stdin_hangup || f->stdout_hangup || f->master_hangup) {
 308                 /* Exit the loop if any side hung up and if there's
 309                  * nothing more to write or nothing we could write. */
 310
 311                 if ((f->out_buffer_full <= 0 || f->stdout_hangup) &&
 312                     (f->in_buffer_full <= 0 || f->master_hangup))
 313                         return pty_forward_done(f, 0);
 314         }
 315
 316         /* If we were asked to drain, and there's nothing more to handle from the master, then call the callback
 317          * too. */
 318         if (f->drain && drained(f))
 319                 return pty_forward_done(f, 0);
 320
 321         return 0;
 322 }
 323
 324 static int on_master_event(sd_event_source *e, int fd, uint32_t revents, void *userdata) {
 325         PTYForward *f = userdata;
 326
 327         assert(f);
 328         assert(e);
 329         assert(e == f->master_event_source);
 330         assert(fd >= 0);
 331         assert(fd == f->master);
 332
 333         if (revents & (EPOLLIN|EPOLLHUP))
 334                 f->master_readable = true;
 335
 336         if (revents & (EPOLLOUT|EPOLLHUP))
 337                 f->master_writable = true;
 338
 339         return shovel(f);
 340 }
 341
 342 static int on_stdin_event(sd_event_source *e, int fd, uint32_t revents, void *userdata) {
 343         PTYForward *f = userdata;
 344
 345         assert(f);
 346         assert(e);
 347         assert(e == f->stdin_event_source);
 348         assert(fd >= 0);
 349         assert(fd == STDIN_FILENO);
 350
 351         if (revents & (EPOLLIN|EPOLLHUP))
 352                 f->stdin_readable = true;
 353
 354         return shovel(f);
 355 }
 356
 357 static int on_stdout_event(sd_event_source *e, int fd, uint32_t revents, void *userdata) {
 358         PTYForward *f = userdata;
 359
 360         assert(f);
 361         assert(e);
 362         assert(e == f->stdout_event_source);
 363         assert(fd >= 0);
 364         assert(fd == STDOUT_FILENO);
 365
 366         if (revents & (EPOLLOUT|EPOLLHUP))
 367                 f->stdout_writable = true;
 368
 369         return shovel(f);
 370 }
 371
 372 static int on_sigwinch_event(sd_event_source *e, const struct signalfd_siginfo *si, void *userdata) {
 373         PTYForward *f = userdata;
 374         struct winsize ws;
 375
 376         assert(f);
 377         assert(e);
 378         assert(e == f->sigwinch_event_source);
 379
 380         /* The window size changed, let's forward that. */
 381         if (ioctl(STDOUT_FILENO, TIOCGWINSZ, &ws) >= 0)
 382                 (void) ioctl(f->master, TIOCSWINSZ, &ws);
 383
 384         return 0;
 385 }
 386
 387 int pty_forward_new(
 388                 sd_event *event,
 389                 int master,
 390                 PTYForwardFlags flags,
 391                 PTYForward **ret) {
 392
 393         _cleanup_(pty_forward_freep) PTYForward *f = NULL;
 394         struct winsize ws;
 395         int r;
 396
 397         f = new0(PTYForward, 1);
 398         if (!f)
 399                 return -ENOMEM;
 400
 401         f->flags = flags;
 402
 403         if (event)
 404                 f->event = sd_event_ref(event);
 405         else {
 406                 r = sd_event_default(&f->event);
 407                 if (r < 0)
 408                         return r;
 409         }
 410
 411         if (!(flags & PTY_FORWARD_READ_ONLY)) {
 412                 r = fd_nonblock(STDIN_FILENO, true);
 413                 if (r < 0)
 414                         return r;
 415
 416                 r = fd_nonblock(STDOUT_FILENO, true);
 417                 if (r < 0)
 418                         return r;
 419         }
 420
 421         r = fd_nonblock(master, true);
 422         if (r < 0)
 423                 return r;
 424
 425         f->master = master;
 426
 427         if (ioctl(STDOUT_FILENO, TIOCGWINSZ, &ws) >= 0)
 428                 (void) ioctl(master, TIOCSWINSZ, &ws);
 429
 430         if (!(flags & PTY_FORWARD_READ_ONLY)) {
 431                 if (tcgetattr(STDIN_FILENO, &f->saved_stdin_attr) >= 0) {
 432                         struct termios raw_stdin_attr;
 433
 434                         f->saved_stdin = true;
 435
 436                         raw_stdin_attr = f->saved_stdin_attr;
 437                         cfmakeraw(&raw_stdin_attr);
 438                         raw_stdin_attr.c_oflag = f->saved_stdin_attr.c_oflag;
 439                         tcsetattr(STDIN_FILENO, TCSANOW, &raw_stdin_attr);
 440                 }
 441
 442                 if (tcgetattr(STDOUT_FILENO, &f->saved_stdout_attr) >= 0) {
 443                         struct termios raw_stdout_attr;
 444
 445                         f->saved_stdout = true;
 446
 447                         raw_stdout_attr = f->saved_stdout_attr;
 448                         cfmakeraw(&raw_stdout_attr);
 449                         raw_stdout_attr.c_iflag = f->saved_stdout_attr.c_iflag;
 450                         raw_stdout_attr.c_lflag = f->saved_stdout_attr.c_lflag;
 451                         tcsetattr(STDOUT_FILENO, TCSANOW, &raw_stdout_attr);
 452                 }
 453
 454                 r = sd_event_add_io(f->event, &f->stdin_event_source, STDIN_FILENO, EPOLLIN|EPOLLET, on_stdin_event, f);
 455                 if (r < 0 && r != -EPERM)
 456                         return r;
 457
 458                 if (r >= 0)
 459                         (void) sd_event_source_set_description(f->stdin_event_source, "ptyfwd-stdin");
 460         }
 461
 462         r = sd_event_add_io(f->event, &f->stdout_event_source, STDOUT_FILENO, EPOLLOUT|EPOLLET, on_stdout_event, f);
 463         if (r == -EPERM)
 464                 /* stdout without epoll support. Likely redirected to regular file. */
 465                 f->stdout_writable = true;
 466         else if (r < 0)
 467                 return r;
 468         else
 469                 (void) sd_event_source_set_description(f->stdout_event_source, "ptyfwd-stdout");
 470
 471         r = sd_event_add_io(f->event, &f->master_event_source, master, EPOLLIN|EPOLLOUT|EPOLLET, on_master_event, f);
 472         if (r < 0)
 473                 return r;
 474
 475         (void) sd_event_source_set_description(f->master_event_source, "ptyfwd-master");
 476
 477         r = sd_event_add_signal(f->event, &f->sigwinch_event_source, SIGWINCH, on_sigwinch_event, f);
 478         if (r < 0)
 479                 return r;
 480
 481         (void) sd_event_source_set_description(f->sigwinch_event_source, "ptyfwd-sigwinch");
 482
 483         *ret = TAKE_PTR(f);
 484
 485         return 0;
 486 }
 487
 488 PTYForward *pty_forward_free(PTYForward *f) {
 489         pty_forward_disconnect(f);
 490         return mfree(f);
 491 }
 492
 493 int pty_forward_get_last_char(PTYForward *f, char *ch) {
 494         assert(f);
 495         assert(ch);
 496
 497         if (!f->last_char_set)
 498                 return -ENXIO;
 499
 500         *ch = f->last_char;
 501         return 0;
 502 }
 503
 504 int pty_forward_set_ignore_vhangup(PTYForward *f, bool b) {
 505         int r;
 506
 507         assert(f);
 508
 509         if (!!(f->flags & PTY_FORWARD_IGNORE_VHANGUP) == b)
 510                 return 0;
 511
 512         SET_FLAG(f->flags, PTY_FORWARD_IGNORE_VHANGUP, b);
 513
 514         if (!ignore_vhangup(f)) {
 515
 516                 /* We shall now react to vhangup()s? Let's check
 517                  * immediately if we might be in one */
 518
 519                 f->master_readable = true;
 520                 r = shovel(f);
 521                 if (r < 0)
 522                         return r;
 523         }
 524
 525         return 0;
 526 }
 527
 528 bool pty_forward_get_ignore_vhangup(PTYForward *f) {
 529         assert(f);
 530
 531         return !!(f->flags & PTY_FORWARD_IGNORE_VHANGUP);
 532 }
 533
 534 bool pty_forward_is_done(PTYForward *f) {
 535         assert(f);
 536
 537         return f->done;
 538 }
 539
 540 void pty_forward_set_handler(PTYForward *f, PTYForwardHandler cb, void *userdata) {
 541         assert(f);
 542
 543         f->handler = cb;
 544         f->userdata = userdata;
 545 }
 546
 547 bool pty_forward_drain(PTYForward *f) {
 548         assert(f);
 549
 550         /* Starts draining the forwarder. Specifically:
 551          *
 552          * - Returns true if there are no unprocessed bytes from the pty, false otherwise
 553          *
 554          * - Makes sure the handler function is called the next time the number of unprocessed bytes hits zero
 555          */
 556
 557         f->drain = true;
 558         return drained(f);
 559 }
 560
 561 int pty_forward_set_priority(PTYForward *f, int64_t priority) {
 562         int r;
 563         assert(f);
 564
 565         r = sd_event_source_set_priority(f->stdin_event_source, priority);
 566         if (r < 0)
 567                 return r;
 568
 569         r = sd_event_source_set_priority(f->stdout_event_source, priority);
 570         if (r < 0)
 571                 return r;
 572
 573         r = sd_event_source_set_priority(f->master_event_source, priority);
 574         if (r < 0)
 575                 return r;
 576
 577         r = sd_event_source_set_priority(f->sigwinch_event_source, priority);
 578         if (r < 0)
 579                 return r;
 580
 581         return 0;
 582 }