miscutils/conspy.c

   1 /* vi: set sw=4 ts=4: */
   2 /*
   3  * A text-mode VNC like program for Linux virtual terminals.
   4  *
   5  * pascal.bellard@ads-lu.com
   6  *
   7  * Based on Russell Stuart's conspy.c
   8  *   http://ace-host.stuart.id.au/russell/files/conspy.c
   9  *
  10  * Licensed under GPLv2 or later, see file License in this tarball for details.
  11  */
  12
  13 //applet:IF_CONSPY(APPLET(conspy, _BB_DIR_BIN, _BB_SUID_DROP))
  14
  15 //kbuild:lib-$(CONFIG_CONSPY) += conspy.o
  16
  17 //config:config CONSPY
  18 //config:       bool "conspy"
  19 //config:       default n
  20 //config:       help
  21 //config:         A text-mode VNC like program for Linux virtual terminals.
  22 //config:         example:  conspy NUM      shared access to console num
  23 //config:         or        conspy -nd NUM  screenshot of console num
  24 //config:         or        conspy -cs NUM  poor man's GNU screen like
  25
  26 //usage:#define conspy_trivial_usage
  27 //usage:        "[-vcsndf] [-x COL] [-y LINE] [CONSOLE_NO]"
  28 //usage:#define conspy_full_usage "\n\n"
  29 //usage:     "A text-mode VNC like program for Linux virtual consoles."
  30 //usage:     "\nTo exit, quickly press ESC 3 times."
  31 //usage:     "\n"
  32 //usage:     "\nOptions:"
  33 //usage:     "\n        -v      Don't send keystrokes to the console"
  34 //usage:     "\n        -c      Create missing devices in /dev"
  35 //usage:     "\n        -s      Open a SHELL session"
  36 //usage:     "\n        -n      Black & white"
  37 //usage:     "\n        -d      Dump console to stdout"
  38 //usage:     "\n        -f      Follow cursor"
  39 //usage:     "\n        -x COL  Starting column"
  40 //usage:     "\n        -y LINE Starting line"
  41
  42 #include "libbb.h"
  43 #include <sys/kd.h>
  44
  45 struct screen_info {
  46         unsigned char lines, cols, cursor_x, cursor_y;
  47 };
  48
  49 #define CHAR(x) (*(uint8_t*)(x))
  50 #define ATTR(x) (((uint8_t*)(x))[1])
  51 #define NEXT(x) ((x) += 2)
  52 #define DATA(x) (*(uint16_t*)(x))
  53
  54 struct globals {
  55         char* data;
  56         int size;
  57         int x, y;
  58         int kbd_fd;
  59         int ioerror_count;
  60         int key_count;
  61         int escape_count;
  62         int nokeys;
  63         int current;
  64         int first_line_offset;
  65         int last_attr;
  66         // cached local tty parameters
  67         unsigned width;
  68         unsigned height;
  69         unsigned col;
  70         unsigned line;
  71         smallint curoff; // unknown:0 cursor on:-1 cursor off:1
  72         char attrbuf[sizeof("\033[0;1;5;30;40m")];
  73         // remote console
  74         struct screen_info remote;
  75         // saved local tty terminfo
  76         struct termios term_orig;
  77         char vcsa_name[sizeof("/dev/vcsaNN")];
  78 };
  79
  80 #define G (*ptr_to_globals)
  81 #define INIT_G() do { \
  82         SET_PTR_TO_GLOBALS(xzalloc(sizeof(G))); \
  83         G.attrbuf[0] = '\033'; \
  84         G.attrbuf[1] = '['; \
  85         G.width = G.height = UINT_MAX; \
  86         G.last_attr--; \
  87 } while (0)
  88
  89 enum {
  90         FLAG_v,  // view only
  91         FLAG_c,  // create device if need
  92         FLAG_s,  // session
  93         FLAG_n,  // no colors
  94         FLAG_d,  // dump screen
  95         FLAG_f,  // follow cursor
  96 };
  97 #define FLAG(x) (1 << FLAG_##x)
  98 #define BW (option_mask32 & FLAG(n))
  99
 100 static void clrscr(void)
 101 {
 102         // Home, clear till end of screen
 103         fputs("\033[1;1H" "\033[J", stdout);
 104         G.col = G.line = 0;
 105 }
 106
 107 static void set_cursor(int state)
 108 {
 109         if (G.curoff != state) {
 110                 G.curoff = state;
 111                 fputs("\033[?25", stdout);
 112                 bb_putchar("h?l"[1 + state]);
 113         }
 114 }
 115
 116 static void gotoxy(int col, int line)
 117 {
 118         if (G.col != col || G.line != line) {
 119                 G.col = col;
 120                 G.line = line;
 121                 printf("\033[%u;%uH", line + 1, col + 1);
 122         }
 123 }
 124
 125 static void cleanup(int code)
 126 {
 127         set_cursor(-1); // cursor on
 128         tcsetattr(G.kbd_fd, TCSANOW, &G.term_orig);
 129         if (ENABLE_FEATURE_CLEAN_UP) {
 130                 close(G.kbd_fd);
 131         }
 132         // Reset attributes
 133         if (!BW)
 134                 fputs("\033[0m", stdout);
 135         bb_putchar('\n');
 136         if (code > 1)
 137                 kill_myself_with_sig(code);
 138         exit(code);
 139 }
 140
 141 static void screen_read_close(void)
 142 {
 143         unsigned i, j;
 144         int vcsa_fd;
 145         char *data;
 146
 147         // Close & re-open vcsa in case they have swapped virtual consoles
 148         vcsa_fd = xopen(G.vcsa_name, O_RDONLY);
 149         xread(vcsa_fd, &G.remote, 4);
 150         i = G.remote.cols * 2;
 151         G.first_line_offset = G.y * i;
 152         i *= G.remote.lines;
 153         if (G.data == NULL) {
 154                 G.size = i;
 155                 G.data = xzalloc(2 * i);
 156         }
 157         else if (G.size != i) {
 158                 cleanup(1);
 159         }
 160         data = G.data + G.current;
 161         xread(vcsa_fd, data, G.size);
 162         close(vcsa_fd);
 163         for (i = 0; i < G.remote.lines; i++) {
 164                 for (j = 0; j < G.remote.cols; j++, NEXT(data)) {
 165                         unsigned x = j - G.x; // if will catch j < G.x too
 166                         unsigned y = i - G.y; // if will catch i < G.y too
 167
 168                         if (CHAR(data) < ' ')
 169                                 CHAR(data) = ' ';
 170                         if (y >= G.height || x >= G.width)
 171                                 DATA(data) = 0;
 172                 }
 173         }
 174 }
 175
 176 static void screen_char(char *data)
 177 {
 178         if (!BW) {
 179                 uint8_t attr = ATTR(data);
 180                 //uint8_t attr = ATTR(data) >> 1; // for framebuffer console
 181                 uint8_t attr_diff = G.last_attr ^ attr;
 182
 183                 if (attr_diff) {
 184 // Attribute layout for VGA compatible text videobuffer:
 185 // blinking text
 186 // |red bkgd
 187 // ||green bkgd
 188 // |||blue bkgd
 189 // vvvv
 190 // 00000000 <- lsb bit on the right
 191 //     bold text / text 8th bit
 192 //      red text
 193 //       green text
 194 //        blue text
 195 // TODO: apparently framebuffer-based console uses different layout
 196 // (bug? attempt to get 8th text bit in better position?)
 197 // red bkgd
 198 // |green bkgd
 199 // ||blue bkgd
 200 // vvv
 201 // 00000000 <- lsb bit on the right
 202 //    bold text
 203 //     red text
 204 //      green text
 205 //       blue text
 206 //        text 8th bit
 207                         // converting RGB color bit triad to BGR:
 208                         static const char color[8] = "04261537";
 209                         const uint8_t fg_mask = 0x07, bold_mask  = 0x08;
 210                         const uint8_t bg_mask = 0x70, blink_mask = 0x80;
 211                         char *ptr;
 212
 213                         ptr = G.attrbuf + 2; // skip "ESC ["
 214
 215                         // (G.last_attr & ~attr) has 1 only where
 216                         // G.last_attr has 1 but attr has 0.
 217                         // Here we check whether we have transition
 218                         // bold->non-bold or blink->non-blink:
 219                         if (G.last_attr < 0  // initial value
 220                          || ((G.last_attr & ~attr) & (bold_mask | blink_mask)) != 0
 221                         ) {
 222                                 *ptr++ = '0'; // "reset all attrs"
 223                                 *ptr++ = ';';
 224                                 // must set fg & bg, maybe need to set bold or blink:
 225                                 attr_diff = attr | ~(bold_mask | blink_mask);
 226                         }
 227                         G.last_attr = attr;
 228                         if (attr_diff & bold_mask) {
 229                                 *ptr++ = '1';
 230                                 *ptr++ = ';';
 231                         }
 232                         if (attr_diff & blink_mask) {
 233                                 *ptr++ = '5';
 234                                 *ptr++ = ';';
 235                         }
 236                         if (attr_diff & fg_mask) {
 237                                 *ptr++ = '3';
 238                                 *ptr++ = color[attr & fg_mask];
 239                                 *ptr++ = ';';
 240                         }
 241                         if (attr_diff & bg_mask) {
 242                                 *ptr++ = '4';
 243                                 *ptr++ = color[(attr & bg_mask) >> 4];
 244                                 *ptr++ = ';';
 245                         }
 246                         if (ptr != G.attrbuf + 2) {
 247                                 ptr[-1] = 'm';
 248                                 *ptr = '\0';
 249                                 fputs(G.attrbuf, stdout);
 250                         }
 251                 }
 252         }
 253         putchar(CHAR(data));
 254         G.col++;
 255 }
 256
 257 static void screen_dump(void)
 258 {
 259         int linefeed_cnt;
 260         int line, col;
 261         int linecnt = G.remote.lines - G.y;
 262         char *data = G.data + G.current + G.first_line_offset;
 263
 264         linefeed_cnt = 0;
 265         for (line = 0; line < linecnt && line < G.height; line++) {
 266                 int space_cnt = 0;
 267                 for (col = 0; col < G.remote.cols; col++, NEXT(data)) {
 268                         unsigned tty_col = col - G.x; // if will catch col < G.x too
 269
 270                         if (tty_col >= G.width)
 271                                 continue;
 272                         space_cnt++;
 273                         if (BW && CHAR(data) == ' ')
 274                                 continue;
 275                         while (linefeed_cnt != 0) {
 276                                 //bb_putchar('\r'); - tty driver does it for us
 277                                 bb_putchar('\n');
 278                                 linefeed_cnt--;
 279                         }
 280                         while (--space_cnt)
 281                                 bb_putchar(' ');
 282                         screen_char(data);
 283                 }
 284                 linefeed_cnt++;
 285         }
 286 }
 287
 288 static void curmove(void)
 289 {
 290         unsigned cx = G.remote.cursor_x - G.x;
 291         unsigned cy = G.remote.cursor_y - G.y;
 292         int cursor = 1;
 293
 294         if (cx < G.width && cy < G.height) {
 295                 gotoxy(cx, cy);
 296                 cursor = -1;
 297         }
 298         set_cursor(cursor);
 299 }
 300
 301 static void create_cdev_if_doesnt_exist(const char* name, dev_t dev)
 302 {
 303         int fd = open(name, O_RDONLY);
 304         if (fd != -1)
 305                 close(fd);
 306         else if (errno == ENOENT)
 307                 mknod(name, S_IFCHR | 0660, dev);
 308 }
 309
 310 static NOINLINE void start_shell_in_child(const char* tty_name)
 311 {
 312         int pid = xvfork();
 313         if (pid == 0) {
 314                 struct termios termchild;
 315                 char *shell = getenv("SHELL");
 316
 317                 if (!shell)
 318                         shell = (char *) DEFAULT_SHELL;
 319                 signal(SIGHUP, SIG_IGN);
 320                 // set tty as a controlling tty
 321                 setsid();
 322                 // make tty to be input, output, error
 323                 close(0);
 324                 xopen(tty_name, O_RDWR); // uses fd 0
 325                 xdup2(0, 1);
 326                 xdup2(0, 2);
 327                 ioctl(0, TIOCSCTTY, 1);
 328                 tcsetpgrp(0, getpid());
 329                 tcgetattr(0, &termchild);
 330                 termchild.c_lflag |= ECHO;
 331                 termchild.c_oflag |= ONLCR | XTABS;
 332                 termchild.c_iflag |= ICRNL;
 333                 termchild.c_iflag &= ~IXOFF;
 334                 tcsetattr_stdin_TCSANOW(&termchild);
 335                 execl(shell, shell, "-i", (char *) NULL);
 336                 bb_simple_perror_msg_and_die(shell);
 337         }
 338 }
 339
 340 int conspy_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 341 int conspy_main(int argc UNUSED_PARAM, char **argv)
 342 {
 343         char tty_name[sizeof("/dev/ttyNN")];
 344 #define keybuf bb_common_bufsiz1
 345         struct termios termbuf;
 346         unsigned opts;
 347         unsigned ttynum;
 348         int poll_timeout_ms;
 349 #if ENABLE_LONG_OPTS
 350         static const char getopt_longopts[] ALIGN1 =
 351                 "viewonly\0"     No_argument "v"
 352                 "createdevice\0" No_argument "c"
 353                 "session\0"      No_argument "s"
 354                 "nocolors\0"     No_argument "n"
 355                 "dump\0"         No_argument "d"
 356                 "follow\0"       No_argument "f"
 357                 ;
 358
 359         applet_long_options = getopt_longopts;
 360 #endif
 361         INIT_G();
 362         strcpy(G.vcsa_name, "/dev/vcsa");
 363
 364         opt_complementary = "x+:y+"; // numeric params
 365         opts = getopt32(argv, "vcsndfx:y:", &G.x, &G.y);
 366         argv += optind;
 367         ttynum = 0;
 368         if (argv[0]) {
 369                 ttynum = xatou_range(argv[0], 0, 63);
 370                 sprintf(G.vcsa_name + sizeof("/dev/vcsa")-1, "%u", ttynum);
 371         }
 372         sprintf(tty_name, "%s%u", "/dev/tty", ttynum);
 373         if (opts & FLAG(c)) {
 374                 if ((opts & (FLAG(s)|FLAG(v))) != FLAG(v))
 375                         create_cdev_if_doesnt_exist(tty_name, makedev(4, ttynum));
 376                 create_cdev_if_doesnt_exist(G.vcsa_name, makedev(7, 128 + ttynum));
 377         }
 378         if ((opts & FLAG(s)) && ttynum) {
 379                 start_shell_in_child(tty_name);
 380         }
 381
 382         screen_read_close();
 383         if (opts & FLAG(d)) {
 384                 screen_dump();
 385                 bb_putchar('\n');
 386                 return 0;
 387         }
 388
 389         bb_signals(BB_FATAL_SIGS, cleanup);
 390
 391         // All characters must be passed through to us unaltered
 392         G.kbd_fd = xopen(CURRENT_TTY, O_RDONLY);
 393         tcgetattr(G.kbd_fd, &G.term_orig);
 394         termbuf = G.term_orig;
 395         termbuf.c_iflag &= ~(BRKINT|INLCR|ICRNL|IXON|IXOFF|IUCLC|IXANY|IMAXBEL);
 396         //termbuf.c_oflag &= ~(OPOST); - no, we still want \n -> \r\n
 397         termbuf.c_lflag &= ~(ISIG|ICANON|ECHO);
 398         termbuf.c_cc[VMIN] = 1;
 399         termbuf.c_cc[VTIME] = 0;
 400         tcsetattr(G.kbd_fd, TCSANOW, &termbuf);
 401
 402         poll_timeout_ms = 250;
 403         while (1) {
 404                 struct pollfd pfd;
 405                 int bytes_read;
 406                 int i, j;
 407                 char *data, *old;
 408
 409                 // in the first loop G.width = G.height = 0: refresh
 410                 i = G.width;
 411                 j = G.height;
 412                 get_terminal_width_height(G.kbd_fd, &G.width, &G.height);
 413                 if (option_mask32 & FLAG(f)) {
 414                         int nx = G.remote.cursor_x - G.width + 1;
 415                         int ny = G.remote.cursor_y - G.height + 1;
 416
 417                         if (G.remote.cursor_x < G.x) {
 418                                 G.x = G.remote.cursor_x;
 419                                 i = 0;  // force refresh
 420                         }
 421                         if (nx > G.x) {
 422                                 G.x = nx;
 423                                 i = 0;  // force refresh
 424                         }
 425                         if (G.remote.cursor_y < G.y) {
 426                                 G.y = G.remote.cursor_y;
 427                                 i = 0;  // force refresh
 428                         }
 429                         if (ny > G.y) {
 430                                 G.y = ny;
 431                                 i = 0;  // force refresh
 432                         }
 433                 }
 434
 435                 // Scan console data and redraw our tty where needed
 436                 old = G.data + G.current;
 437                 G.current = G.size - G.current;
 438                 data = G.data + G.current;
 439                 screen_read_close();
 440                 if (i != G.width || j != G.height) {
 441                         clrscr();
 442                         screen_dump();
 443                 } else {
 444                         // For each remote line
 445                         old += G.first_line_offset;
 446                         data += G.first_line_offset;
 447                         for (i = G.y; i < G.remote.lines; i++) {
 448                                 char *first = NULL; // first char which needs updating
 449                                 char *last = last;  // last char which needs updating
 450                                 unsigned iy = i - G.y;
 451
 452                                 if (iy >= G.height)
 453                                         break;
 454                                 for (j = 0; j < G.remote.cols; j++, NEXT(old), NEXT(data)) {
 455                                         unsigned jx = j - G.x; // if will catch j >= G.x too
 456
 457                                         if (jx < G.width && DATA(data) != DATA(old)) {
 458                                                 last = data;
 459                                                 if (!first) {
 460                                                         first = data;
 461                                                         gotoxy(jx, iy);
 462                                                 }
 463                                         }
 464                                 }
 465                                 if (first) {
 466                                         // Rewrite updated data on the local screen
 467                                         for (; first <= last; NEXT(first))
 468                                                 screen_char(first);
 469                                 }
 470                         }
 471                 }
 472                 curmove();
 473
 474                 // Wait for local user keypresses
 475                 fflush_all();
 476                 pfd.fd = G.kbd_fd;
 477                 pfd.events = POLLIN;
 478                 bytes_read = 0;
 479                 switch (poll(&pfd, 1, poll_timeout_ms)) {
 480                         char *k;
 481                 case -1:
 482                         if (errno != EINTR)
 483                                 cleanup(1);
 484                         break;
 485                 case 0:
 486                         if (++G.nokeys >= 4)
 487                                 G.nokeys = G.escape_count = 0;
 488                         break;
 489                 default:
 490                         // Read the keys pressed
 491                         k = keybuf + G.key_count;
 492                         bytes_read = read(G.kbd_fd, k, sizeof(keybuf) - G.key_count);
 493                         if (bytes_read < 0)
 494                                 cleanup(1);
 495
 496                         // Do exit processing
 497                         for (i = 0; i < bytes_read; i++) {
 498                                 if (k[i] != '\033')
 499                                         G.escape_count = 0;
 500                                 else if (++G.escape_count >= 3)
 501                                         cleanup(0);
 502                         }
 503                 }
 504                 poll_timeout_ms = 250;
 505
 506                 // Insert all keys pressed into the virtual console's input
 507                 // buffer.  Don't do this if the virtual console is in scan
 508                 // code mode - giving ASCII characters to a program expecting
 509                 // scan codes will confuse it.
 510                 if (!(option_mask32 & FLAG(v)) && G.escape_count == 0) {
 511                         int handle, result;
 512                         long kbd_mode;
 513
 514                         G.key_count += bytes_read;
 515                         handle = xopen(tty_name, O_WRONLY);
 516                         result = ioctl(handle, KDGKBMODE, &kbd_mode);
 517                         if (result >= 0) {
 518                                 char *p = keybuf;
 519
 520                                 if (kbd_mode != K_XLATE && kbd_mode != K_UNICODE) {
 521                                         G.key_count = 0; // scan code mode
 522                                 }
 523                                 for (; G.key_count != 0; p++, G.key_count--) {
 524                                         result = ioctl(handle, TIOCSTI, p);
 525                                         if (result < 0) {
 526                                                 memmove(keybuf, p, G.key_count);
 527                                                 break;
 528                                         }
 529                                         // If there is an application on console which reacts
 530                                         // to keypresses, we need to make our first sleep
 531                                         // shorter to quickly redraw whatever it printed there.
 532                                         poll_timeout_ms = 20;
 533                                 }
 534                         }
 535                         // Close & re-open tty in case they have
 536                         // swapped virtual consoles
 537                         close(handle);
 538
 539                         // We sometimes get spurious IO errors on the TTY
 540                         // as programs close and re-open it
 541                         if (result >= 0)
 542                                 G.ioerror_count = 0;
 543                         else if (errno != EIO || ++G.ioerror_count > 4)
 544                                 cleanup(1);
 545                 }
 546         } /* while (1) */
 547 }