src/shared/ptyfwd.c

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