Contents of /tags/mkinitrd-6_3_3/busybox/networking/telnetd.c
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Wed Dec 15 21:43:57 2010 UTC (13 years, 9 months ago) by niro
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Wed Dec 15 21:43:57 2010 UTC (13 years, 9 months ago) by niro
File MIME type: text/plain
File size: 20641 byte(s)
tagged 'mkinitrd-6_3_3'
1 | /* vi: set sw=4 ts=4: */ |
2 | /* |
3 | * Simple telnet server |
4 | * Bjorn Wesen, Axis Communications AB (bjornw@axis.com) |
5 | * |
6 | * Licensed under GPLv2 or later, see file LICENSE in this tarball for details. |
7 | * |
8 | * --------------------------------------------------------------------------- |
9 | * (C) Copyright 2000, Axis Communications AB, LUND, SWEDEN |
10 | **************************************************************************** |
11 | * |
12 | * The telnetd manpage says it all: |
13 | * |
14 | * Telnetd operates by allocating a pseudo-terminal device (see pty(4)) for |
15 | * a client, then creating a login process which has the slave side of the |
16 | * pseudo-terminal as stdin, stdout, and stderr. Telnetd manipulates the |
17 | * master side of the pseudo-terminal, implementing the telnet protocol and |
18 | * passing characters between the remote client and the login process. |
19 | * |
20 | * Vladimir Oleynik <dzo@simtreas.ru> 2001 |
21 | * Set process group corrections, initial busybox port |
22 | */ |
23 | #define DEBUG 0 |
24 | |
25 | #include "libbb.h" |
26 | #include <syslog.h> |
27 | |
28 | #if DEBUG |
29 | # define TELCMDS |
30 | # define TELOPTS |
31 | #endif |
32 | #include <arpa/telnet.h> |
33 | |
34 | #if ENABLE_FEATURE_UTMP |
35 | # include <utmp.h> /* LOGIN_PROCESS */ |
36 | #endif |
37 | |
38 | |
39 | struct tsession { |
40 | struct tsession *next; |
41 | pid_t shell_pid; |
42 | int sockfd_read; |
43 | int sockfd_write; |
44 | int ptyfd; |
45 | |
46 | /* two circular buffers */ |
47 | /*char *buf1, *buf2;*/ |
48 | /*#define TS_BUF1(ts) ts->buf1*/ |
49 | /*#define TS_BUF2(ts) TS_BUF2(ts)*/ |
50 | #define TS_BUF1(ts) ((unsigned char*)(ts + 1)) |
51 | #define TS_BUF2(ts) (((unsigned char*)(ts + 1)) + BUFSIZE) |
52 | int rdidx1, wridx1, size1; |
53 | int rdidx2, wridx2, size2; |
54 | }; |
55 | |
56 | /* Two buffers are directly after tsession in malloced memory. |
57 | * Make whole thing fit in 4k */ |
58 | enum { BUFSIZE = (4 * 1024 - sizeof(struct tsession)) / 2 }; |
59 | |
60 | |
61 | /* Globals */ |
62 | struct globals { |
63 | struct tsession *sessions; |
64 | const char *loginpath; |
65 | const char *issuefile; |
66 | int maxfd; |
67 | } FIX_ALIASING; |
68 | #define G (*(struct globals*)&bb_common_bufsiz1) |
69 | #define INIT_G() do { \ |
70 | G.loginpath = "/bin/login"; \ |
71 | G.issuefile = "/etc/issue.net"; \ |
72 | } while (0) |
73 | |
74 | |
75 | /* |
76 | Remove all IAC's from buf1 (received IACs are ignored and must be removed |
77 | so as to not be interpreted by the terminal). Make an uninterrupted |
78 | string of characters fit for the terminal. Do this by packing |
79 | all characters meant for the terminal sequentially towards the end of buf. |
80 | |
81 | Return a pointer to the beginning of the characters meant for the terminal |
82 | and make *num_totty the number of characters that should be sent to |
83 | the terminal. |
84 | |
85 | Note - if an IAC (3 byte quantity) starts before (bf + len) but extends |
86 | past (bf + len) then that IAC will be left unprocessed and *processed |
87 | will be less than len. |
88 | |
89 | CR-LF ->'s CR mapping is also done here, for convenience. |
90 | |
91 | NB: may fail to remove iacs which wrap around buffer! |
92 | */ |
93 | static unsigned char * |
94 | remove_iacs(struct tsession *ts, int *pnum_totty) |
95 | { |
96 | unsigned char *ptr0 = TS_BUF1(ts) + ts->wridx1; |
97 | unsigned char *ptr = ptr0; |
98 | unsigned char *totty = ptr; |
99 | unsigned char *end = ptr + MIN(BUFSIZE - ts->wridx1, ts->size1); |
100 | int num_totty; |
101 | |
102 | while (ptr < end) { |
103 | if (*ptr != IAC) { |
104 | char c = *ptr; |
105 | |
106 | *totty++ = c; |
107 | ptr++; |
108 | /* We map \r\n ==> \r for pragmatic reasons. |
109 | * Many client implementations send \r\n when |
110 | * the user hits the CarriageReturn key. |
111 | */ |
112 | if (c == '\r' && ptr < end && (*ptr == '\n' || *ptr == '\0')) |
113 | ptr++; |
114 | continue; |
115 | } |
116 | |
117 | if ((ptr+1) >= end) |
118 | break; |
119 | if (ptr[1] == NOP) { /* Ignore? (putty keepalive, etc.) */ |
120 | ptr += 2; |
121 | continue; |
122 | } |
123 | if (ptr[1] == IAC) { /* Literal IAC? (emacs M-DEL) */ |
124 | *totty++ = ptr[1]; |
125 | ptr += 2; |
126 | continue; |
127 | } |
128 | |
129 | /* |
130 | * TELOPT_NAWS support! |
131 | */ |
132 | if ((ptr+2) >= end) { |
133 | /* Only the beginning of the IAC is in the |
134 | buffer we were asked to process, we can't |
135 | process this char */ |
136 | break; |
137 | } |
138 | /* |
139 | * IAC -> SB -> TELOPT_NAWS -> 4-byte -> IAC -> SE |
140 | */ |
141 | if (ptr[1] == SB && ptr[2] == TELOPT_NAWS) { |
142 | struct winsize ws; |
143 | if ((ptr+8) >= end) |
144 | break; /* incomplete, can't process */ |
145 | ws.ws_col = (ptr[3] << 8) | ptr[4]; |
146 | ws.ws_row = (ptr[5] << 8) | ptr[6]; |
147 | ioctl(ts->ptyfd, TIOCSWINSZ, (char *)&ws); |
148 | ptr += 9; |
149 | continue; |
150 | } |
151 | /* skip 3-byte IAC non-SB cmd */ |
152 | #if DEBUG |
153 | fprintf(stderr, "Ignoring IAC %s,%s\n", |
154 | TELCMD(ptr[1]), TELOPT(ptr[2])); |
155 | #endif |
156 | ptr += 3; |
157 | } |
158 | |
159 | num_totty = totty - ptr0; |
160 | *pnum_totty = num_totty; |
161 | /* The difference between ptr and totty is number of iacs |
162 | we removed from the stream. Adjust buf1 accordingly */ |
163 | if ((ptr - totty) == 0) /* 99.999% of cases */ |
164 | return ptr0; |
165 | ts->wridx1 += ptr - totty; |
166 | ts->size1 -= ptr - totty; |
167 | /* Move chars meant for the terminal towards the end of the buffer */ |
168 | return memmove(ptr - num_totty, ptr0, num_totty); |
169 | } |
170 | |
171 | /* |
172 | * Converting single IAC into double on output |
173 | */ |
174 | static size_t iac_safe_write(int fd, const char *buf, size_t count) |
175 | { |
176 | const char *IACptr; |
177 | size_t wr, rc, total; |
178 | |
179 | total = 0; |
180 | while (1) { |
181 | if (count == 0) |
182 | return total; |
183 | if (*buf == (char)IAC) { |
184 | static const char IACIAC[] ALIGN1 = { IAC, IAC }; |
185 | rc = safe_write(fd, IACIAC, 2); |
186 | if (rc != 2) |
187 | break; |
188 | buf++; |
189 | total++; |
190 | count--; |
191 | continue; |
192 | } |
193 | /* count != 0, *buf != IAC */ |
194 | IACptr = memchr(buf, IAC, count); |
195 | wr = count; |
196 | if (IACptr) |
197 | wr = IACptr - buf; |
198 | rc = safe_write(fd, buf, wr); |
199 | if (rc != wr) |
200 | break; |
201 | buf += rc; |
202 | total += rc; |
203 | count -= rc; |
204 | } |
205 | /* here: rc - result of last short write */ |
206 | if ((ssize_t)rc < 0) { /* error? */ |
207 | if (total == 0) |
208 | return rc; |
209 | rc = 0; |
210 | } |
211 | return total + rc; |
212 | } |
213 | |
214 | /* Must match getopt32 string */ |
215 | enum { |
216 | OPT_WATCHCHILD = (1 << 2), /* -K */ |
217 | OPT_INETD = (1 << 3) * ENABLE_FEATURE_TELNETD_STANDALONE, /* -i */ |
218 | OPT_PORT = (1 << 4) * ENABLE_FEATURE_TELNETD_STANDALONE, /* -p PORT */ |
219 | OPT_FOREGROUND = (1 << 6) * ENABLE_FEATURE_TELNETD_STANDALONE, /* -F */ |
220 | OPT_SYSLOG = (1 << 7) * ENABLE_FEATURE_TELNETD_INETD_WAIT, /* -S */ |
221 | OPT_WAIT = (1 << 8) * ENABLE_FEATURE_TELNETD_INETD_WAIT, /* -w SEC */ |
222 | }; |
223 | |
224 | static struct tsession * |
225 | make_new_session( |
226 | IF_FEATURE_TELNETD_STANDALONE(int sock) |
227 | IF_NOT_FEATURE_TELNETD_STANDALONE(void) |
228 | ) { |
229 | #if !ENABLE_FEATURE_TELNETD_STANDALONE |
230 | enum { sock = 0 }; |
231 | #endif |
232 | const char *login_argv[2]; |
233 | struct termios termbuf; |
234 | int fd, pid; |
235 | char tty_name[GETPTY_BUFSIZE]; |
236 | struct tsession *ts = xzalloc(sizeof(struct tsession) + BUFSIZE * 2); |
237 | |
238 | /*ts->buf1 = (char *)(ts + 1);*/ |
239 | /*ts->buf2 = ts->buf1 + BUFSIZE;*/ |
240 | |
241 | /* Got a new connection, set up a tty */ |
242 | fd = xgetpty(tty_name); |
243 | if (fd > G.maxfd) |
244 | G.maxfd = fd; |
245 | ts->ptyfd = fd; |
246 | ndelay_on(fd); |
247 | close_on_exec_on(fd); |
248 | |
249 | /* SO_KEEPALIVE by popular demand */ |
250 | setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, &const_int_1, sizeof(const_int_1)); |
251 | #if ENABLE_FEATURE_TELNETD_STANDALONE |
252 | ts->sockfd_read = sock; |
253 | ndelay_on(sock); |
254 | if (sock == 0) { /* We are called with fd 0 - we are in inetd mode */ |
255 | sock++; /* so use fd 1 for output */ |
256 | ndelay_on(sock); |
257 | } |
258 | ts->sockfd_write = sock; |
259 | if (sock > G.maxfd) |
260 | G.maxfd = sock; |
261 | #else |
262 | /* ts->sockfd_read = 0; - done by xzalloc */ |
263 | ts->sockfd_write = 1; |
264 | ndelay_on(0); |
265 | ndelay_on(1); |
266 | #endif |
267 | |
268 | /* Make the telnet client understand we will echo characters so it |
269 | * should not do it locally. We don't tell the client to run linemode, |
270 | * because we want to handle line editing and tab completion and other |
271 | * stuff that requires char-by-char support. */ |
272 | { |
273 | static const char iacs_to_send[] ALIGN1 = { |
274 | IAC, DO, TELOPT_ECHO, |
275 | IAC, DO, TELOPT_NAWS, |
276 | /* This requires telnetd.ctrlSQ.patch (incomplete) */ |
277 | /* IAC, DO, TELOPT_LFLOW, */ |
278 | IAC, WILL, TELOPT_ECHO, |
279 | IAC, WILL, TELOPT_SGA |
280 | }; |
281 | /* This confuses iac_safe_write(), it will try to duplicate |
282 | * each IAC... */ |
283 | //memcpy(TS_BUF2(ts), iacs_to_send, sizeof(iacs_to_send)); |
284 | //ts->rdidx2 = sizeof(iacs_to_send); |
285 | //ts->size2 = sizeof(iacs_to_send); |
286 | /* So just stuff it into TCP stream! (no error check...) */ |
287 | #if ENABLE_FEATURE_TELNETD_STANDALONE |
288 | safe_write(sock, iacs_to_send, sizeof(iacs_to_send)); |
289 | #else |
290 | safe_write(1, iacs_to_send, sizeof(iacs_to_send)); |
291 | #endif |
292 | /*ts->rdidx2 = 0; - xzalloc did it */ |
293 | /*ts->size2 = 0;*/ |
294 | } |
295 | |
296 | fflush_all(); |
297 | pid = vfork(); /* NOMMU-friendly */ |
298 | if (pid < 0) { |
299 | free(ts); |
300 | close(fd); |
301 | /* sock will be closed by caller */ |
302 | bb_perror_msg("vfork"); |
303 | return NULL; |
304 | } |
305 | if (pid > 0) { |
306 | /* Parent */ |
307 | ts->shell_pid = pid; |
308 | return ts; |
309 | } |
310 | |
311 | /* Child */ |
312 | /* Careful - we are after vfork! */ |
313 | |
314 | /* Restore default signal handling ASAP */ |
315 | bb_signals((1 << SIGCHLD) + (1 << SIGPIPE), SIG_DFL); |
316 | |
317 | if (ENABLE_FEATURE_UTMP) { |
318 | len_and_sockaddr *lsa = get_peer_lsa(sock); |
319 | char *hostname = NULL; |
320 | if (lsa) { |
321 | hostname = xmalloc_sockaddr2dotted(&lsa->u.sa); |
322 | free(lsa); |
323 | } |
324 | write_new_utmp(pid, LOGIN_PROCESS, tty_name, /*username:*/ "LOGIN", hostname); |
325 | free(hostname); |
326 | } |
327 | |
328 | /* Make new session and process group */ |
329 | setsid(); |
330 | |
331 | /* Open the child's side of the tty */ |
332 | /* NB: setsid() disconnects from any previous ctty's. Therefore |
333 | * we must open child's side of the tty AFTER setsid! */ |
334 | close(0); |
335 | xopen(tty_name, O_RDWR); /* becomes our ctty */ |
336 | xdup2(0, 1); |
337 | xdup2(0, 2); |
338 | pid = getpid(); |
339 | tcsetpgrp(0, pid); /* switch this tty's process group to us */ |
340 | |
341 | /* The pseudo-terminal allocated to the client is configured to operate |
342 | * in cooked mode, and with XTABS CRMOD enabled (see tty(4)) */ |
343 | tcgetattr(0, &termbuf); |
344 | termbuf.c_lflag |= ECHO; /* if we use readline we dont want this */ |
345 | termbuf.c_oflag |= ONLCR | XTABS; |
346 | termbuf.c_iflag |= ICRNL; |
347 | termbuf.c_iflag &= ~IXOFF; |
348 | /*termbuf.c_lflag &= ~ICANON;*/ |
349 | tcsetattr_stdin_TCSANOW(&termbuf); |
350 | |
351 | /* Uses FILE-based I/O to stdout, but does fflush_all(), |
352 | * so should be safe with vfork. |
353 | * I fear, though, that some users will have ridiculously big |
354 | * issue files, and they may block writing to fd 1, |
355 | * (parent is supposed to read it, but parent waits |
356 | * for vforked child to exec!) */ |
357 | print_login_issue(G.issuefile, tty_name); |
358 | |
359 | /* Exec shell / login / whatever */ |
360 | login_argv[0] = G.loginpath; |
361 | login_argv[1] = NULL; |
362 | /* exec busybox applet (if PREFER_APPLETS=y), if that fails, |
363 | * exec external program. |
364 | * NB: sock is either 0 or has CLOEXEC set on it. |
365 | * fd has CLOEXEC set on it too. These two fds will be closed here. |
366 | */ |
367 | BB_EXECVP(G.loginpath, (char **)login_argv); |
368 | /* _exit is safer with vfork, and we shouldn't send message |
369 | * to remote clients anyway */ |
370 | _exit(EXIT_FAILURE); /*bb_perror_msg_and_die("execv %s", G.loginpath);*/ |
371 | } |
372 | |
373 | #if ENABLE_FEATURE_TELNETD_STANDALONE |
374 | |
375 | static void |
376 | free_session(struct tsession *ts) |
377 | { |
378 | struct tsession *t; |
379 | |
380 | if (option_mask32 & OPT_INETD) |
381 | exit(EXIT_SUCCESS); |
382 | |
383 | /* Unlink this telnet session from the session list */ |
384 | t = G.sessions; |
385 | if (t == ts) |
386 | G.sessions = ts->next; |
387 | else { |
388 | while (t->next != ts) |
389 | t = t->next; |
390 | t->next = ts->next; |
391 | } |
392 | |
393 | #if 0 |
394 | /* It was said that "normal" telnetd just closes ptyfd, |
395 | * doesn't send SIGKILL. When we close ptyfd, |
396 | * kernel sends SIGHUP to processes having slave side opened. */ |
397 | kill(ts->shell_pid, SIGKILL); |
398 | waitpid(ts->shell_pid, NULL, 0); |
399 | #endif |
400 | close(ts->ptyfd); |
401 | close(ts->sockfd_read); |
402 | /* We do not need to close(ts->sockfd_write), it's the same |
403 | * as sockfd_read unless we are in inetd mode. But in inetd mode |
404 | * we do not reach this */ |
405 | free(ts); |
406 | |
407 | /* Scan all sessions and find new maxfd */ |
408 | G.maxfd = 0; |
409 | ts = G.sessions; |
410 | while (ts) { |
411 | if (G.maxfd < ts->ptyfd) |
412 | G.maxfd = ts->ptyfd; |
413 | if (G.maxfd < ts->sockfd_read) |
414 | G.maxfd = ts->sockfd_read; |
415 | #if 0 |
416 | /* Again, sockfd_write == sockfd_read here */ |
417 | if (G.maxfd < ts->sockfd_write) |
418 | G.maxfd = ts->sockfd_write; |
419 | #endif |
420 | ts = ts->next; |
421 | } |
422 | } |
423 | |
424 | #else /* !FEATURE_TELNETD_STANDALONE */ |
425 | |
426 | /* Used in main() only, thus "return 0" actually is exit(EXIT_SUCCESS). */ |
427 | #define free_session(ts) return 0 |
428 | |
429 | #endif |
430 | |
431 | static void handle_sigchld(int sig UNUSED_PARAM) |
432 | { |
433 | pid_t pid; |
434 | struct tsession *ts; |
435 | int save_errno = errno; |
436 | |
437 | /* Looping: more than one child may have exited */ |
438 | while (1) { |
439 | pid = wait_any_nohang(NULL); |
440 | if (pid <= 0) |
441 | break; |
442 | ts = G.sessions; |
443 | while (ts) { |
444 | if (ts->shell_pid == pid) { |
445 | ts->shell_pid = -1; |
446 | // man utmp: |
447 | // When init(8) finds that a process has exited, it locates its utmp entry |
448 | // by ut_pid, sets ut_type to DEAD_PROCESS, and clears ut_user, ut_host |
449 | // and ut_time with null bytes. |
450 | // [same applies to other processes which maintain utmp entries, like telnetd] |
451 | // |
452 | // We do not bother actually clearing fields: |
453 | // it might be interesting to know who was logged in and from where |
454 | update_utmp(pid, DEAD_PROCESS, /*tty_name:*/ NULL, /*username:*/ NULL, /*hostname:*/ NULL); |
455 | break; |
456 | } |
457 | ts = ts->next; |
458 | } |
459 | } |
460 | |
461 | errno = save_errno; |
462 | } |
463 | |
464 | int telnetd_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE; |
465 | int telnetd_main(int argc UNUSED_PARAM, char **argv) |
466 | { |
467 | fd_set rdfdset, wrfdset; |
468 | unsigned opt; |
469 | int count; |
470 | struct tsession *ts; |
471 | #if ENABLE_FEATURE_TELNETD_STANDALONE |
472 | #define IS_INETD (opt & OPT_INETD) |
473 | int master_fd = master_fd; /* for compiler */ |
474 | int sec_linger = sec_linger; |
475 | char *opt_bindaddr = NULL; |
476 | char *opt_portnbr; |
477 | #else |
478 | enum { |
479 | IS_INETD = 1, |
480 | master_fd = -1, |
481 | }; |
482 | #endif |
483 | INIT_G(); |
484 | |
485 | /* -w NUM, and implies -F. -w and -i don't mix */ |
486 | IF_FEATURE_TELNETD_INETD_WAIT(opt_complementary = "wF:w+:i--w:w--i";) |
487 | /* Even if !STANDALONE, we accept (and ignore) -i, thus people |
488 | * don't need to guess whether it's ok to pass -i to us */ |
489 | opt = getopt32(argv, "f:l:Ki" |
490 | IF_FEATURE_TELNETD_STANDALONE("p:b:F") |
491 | IF_FEATURE_TELNETD_INETD_WAIT("Sw:"), |
492 | &G.issuefile, &G.loginpath |
493 | IF_FEATURE_TELNETD_STANDALONE(, &opt_portnbr, &opt_bindaddr) |
494 | IF_FEATURE_TELNETD_INETD_WAIT(, &sec_linger) |
495 | ); |
496 | if (!IS_INETD /*&& !re_execed*/) { |
497 | /* inform that we start in standalone mode? |
498 | * May be useful when people forget to give -i */ |
499 | /*bb_error_msg("listening for connections");*/ |
500 | if (!(opt & OPT_FOREGROUND)) { |
501 | /* DAEMON_CHDIR_ROOT was giving inconsistent |
502 | * behavior with/without -F, -i */ |
503 | bb_daemonize_or_rexec(0 /*was DAEMON_CHDIR_ROOT*/, argv); |
504 | } |
505 | } |
506 | /* Redirect log to syslog early, if needed */ |
507 | if (IS_INETD || (opt & OPT_SYSLOG) || !(opt & OPT_FOREGROUND)) { |
508 | openlog(applet_name, LOG_PID, LOG_DAEMON); |
509 | logmode = LOGMODE_SYSLOG; |
510 | } |
511 | #if ENABLE_FEATURE_TELNETD_STANDALONE |
512 | if (IS_INETD) { |
513 | G.sessions = make_new_session(0); |
514 | if (!G.sessions) /* pty opening or vfork problem, exit */ |
515 | return 1; /* make_new_session printed error message */ |
516 | } else { |
517 | master_fd = 0; |
518 | if (!(opt & OPT_WAIT)) { |
519 | unsigned portnbr = 23; |
520 | if (opt & OPT_PORT) |
521 | portnbr = xatou16(opt_portnbr); |
522 | master_fd = create_and_bind_stream_or_die(opt_bindaddr, portnbr); |
523 | xlisten(master_fd, 1); |
524 | } |
525 | close_on_exec_on(master_fd); |
526 | } |
527 | #else |
528 | G.sessions = make_new_session(); |
529 | if (!G.sessions) /* pty opening or vfork problem, exit */ |
530 | return 1; /* make_new_session printed error message */ |
531 | #endif |
532 | |
533 | /* We don't want to die if just one session is broken */ |
534 | signal(SIGPIPE, SIG_IGN); |
535 | |
536 | if (opt & OPT_WATCHCHILD) |
537 | signal(SIGCHLD, handle_sigchld); |
538 | else /* prevent dead children from becoming zombies */ |
539 | signal(SIGCHLD, SIG_IGN); |
540 | |
541 | /* |
542 | This is how the buffers are used. The arrows indicate data flow. |
543 | |
544 | +-------+ wridx1++ +------+ rdidx1++ +----------+ |
545 | | | <-------------- | buf1 | <-------------- | | |
546 | | | size1-- +------+ size1++ | | |
547 | | pty | | socket | |
548 | | | rdidx2++ +------+ wridx2++ | | |
549 | | | --------------> | buf2 | --------------> | | |
550 | +-------+ size2++ +------+ size2-- +----------+ |
551 | |
552 | size1: "how many bytes are buffered for pty between rdidx1 and wridx1?" |
553 | size2: "how many bytes are buffered for socket between rdidx2 and wridx2?" |
554 | |
555 | Each session has got two buffers. Buffers are circular. If sizeN == 0, |
556 | buffer is empty. If sizeN == BUFSIZE, buffer is full. In both these cases |
557 | rdidxN == wridxN. |
558 | */ |
559 | again: |
560 | FD_ZERO(&rdfdset); |
561 | FD_ZERO(&wrfdset); |
562 | |
563 | /* Select on the master socket, all telnet sockets and their |
564 | * ptys if there is room in their session buffers. |
565 | * NB: scalability problem: we recalculate entire bitmap |
566 | * before each select. Can be a problem with 500+ connections. */ |
567 | ts = G.sessions; |
568 | while (ts) { |
569 | struct tsession *next = ts->next; /* in case we free ts */ |
570 | if (ts->shell_pid == -1) { |
571 | /* Child died and we detected that */ |
572 | free_session(ts); |
573 | } else { |
574 | if (ts->size1 > 0) /* can write to pty */ |
575 | FD_SET(ts->ptyfd, &wrfdset); |
576 | if (ts->size1 < BUFSIZE) /* can read from socket */ |
577 | FD_SET(ts->sockfd_read, &rdfdset); |
578 | if (ts->size2 > 0) /* can write to socket */ |
579 | FD_SET(ts->sockfd_write, &wrfdset); |
580 | if (ts->size2 < BUFSIZE) /* can read from pty */ |
581 | FD_SET(ts->ptyfd, &rdfdset); |
582 | } |
583 | ts = next; |
584 | } |
585 | if (!IS_INETD) { |
586 | FD_SET(master_fd, &rdfdset); |
587 | /* This is needed because free_session() does not |
588 | * take master_fd into account when it finds new |
589 | * maxfd among remaining fd's */ |
590 | if (master_fd > G.maxfd) |
591 | G.maxfd = master_fd; |
592 | } |
593 | |
594 | { |
595 | struct timeval *tv_ptr = NULL; |
596 | #if ENABLE_FEATURE_TELNETD_INETD_WAIT |
597 | struct timeval tv; |
598 | if ((opt & OPT_WAIT) && !G.sessions) { |
599 | tv.tv_sec = sec_linger; |
600 | tv.tv_usec = 0; |
601 | tv_ptr = &tv; |
602 | } |
603 | #endif |
604 | count = select(G.maxfd + 1, &rdfdset, &wrfdset, NULL, tv_ptr); |
605 | } |
606 | if (count == 0) /* "telnetd -w SEC" timed out */ |
607 | return 0; |
608 | if (count < 0) |
609 | goto again; /* EINTR or ENOMEM */ |
610 | |
611 | #if ENABLE_FEATURE_TELNETD_STANDALONE |
612 | /* Check for and accept new sessions */ |
613 | if (!IS_INETD && FD_ISSET(master_fd, &rdfdset)) { |
614 | int fd; |
615 | struct tsession *new_ts; |
616 | |
617 | fd = accept(master_fd, NULL, NULL); |
618 | if (fd < 0) |
619 | goto again; |
620 | close_on_exec_on(fd); |
621 | |
622 | /* Create a new session and link it into active list */ |
623 | new_ts = make_new_session(fd); |
624 | if (new_ts) { |
625 | new_ts->next = G.sessions; |
626 | G.sessions = new_ts; |
627 | } else { |
628 | close(fd); |
629 | } |
630 | } |
631 | #endif |
632 | |
633 | /* Then check for data tunneling */ |
634 | ts = G.sessions; |
635 | while (ts) { /* For all sessions... */ |
636 | struct tsession *next = ts->next; /* in case we free ts */ |
637 | |
638 | if (/*ts->size1 &&*/ FD_ISSET(ts->ptyfd, &wrfdset)) { |
639 | int num_totty; |
640 | unsigned char *ptr; |
641 | /* Write to pty from buffer 1 */ |
642 | ptr = remove_iacs(ts, &num_totty); |
643 | count = safe_write(ts->ptyfd, ptr, num_totty); |
644 | if (count < 0) { |
645 | if (errno == EAGAIN) |
646 | goto skip1; |
647 | goto kill_session; |
648 | } |
649 | ts->size1 -= count; |
650 | ts->wridx1 += count; |
651 | if (ts->wridx1 >= BUFSIZE) /* actually == BUFSIZE */ |
652 | ts->wridx1 = 0; |
653 | } |
654 | skip1: |
655 | if (/*ts->size2 &&*/ FD_ISSET(ts->sockfd_write, &wrfdset)) { |
656 | /* Write to socket from buffer 2 */ |
657 | count = MIN(BUFSIZE - ts->wridx2, ts->size2); |
658 | count = iac_safe_write(ts->sockfd_write, (void*)(TS_BUF2(ts) + ts->wridx2), count); |
659 | if (count < 0) { |
660 | if (errno == EAGAIN) |
661 | goto skip2; |
662 | goto kill_session; |
663 | } |
664 | ts->size2 -= count; |
665 | ts->wridx2 += count; |
666 | if (ts->wridx2 >= BUFSIZE) /* actually == BUFSIZE */ |
667 | ts->wridx2 = 0; |
668 | } |
669 | skip2: |
670 | /* Should not be needed, but... remove_iacs is actually buggy |
671 | * (it cannot process iacs which wrap around buffer's end)! |
672 | * Since properly fixing it requires writing bigger code, |
673 | * we rely instead on this code making it virtually impossible |
674 | * to have wrapped iac (people don't type at 2k/second). |
675 | * It also allows for bigger reads in common case. */ |
676 | if (ts->size1 == 0) { |
677 | ts->rdidx1 = 0; |
678 | ts->wridx1 = 0; |
679 | } |
680 | if (ts->size2 == 0) { |
681 | ts->rdidx2 = 0; |
682 | ts->wridx2 = 0; |
683 | } |
684 | |
685 | if (/*ts->size1 < BUFSIZE &&*/ FD_ISSET(ts->sockfd_read, &rdfdset)) { |
686 | /* Read from socket to buffer 1 */ |
687 | count = MIN(BUFSIZE - ts->rdidx1, BUFSIZE - ts->size1); |
688 | count = safe_read(ts->sockfd_read, TS_BUF1(ts) + ts->rdidx1, count); |
689 | if (count <= 0) { |
690 | if (count < 0 && errno == EAGAIN) |
691 | goto skip3; |
692 | goto kill_session; |
693 | } |
694 | /* Ignore trailing NUL if it is there */ |
695 | if (!TS_BUF1(ts)[ts->rdidx1 + count - 1]) { |
696 | --count; |
697 | } |
698 | ts->size1 += count; |
699 | ts->rdidx1 += count; |
700 | if (ts->rdidx1 >= BUFSIZE) /* actually == BUFSIZE */ |
701 | ts->rdidx1 = 0; |
702 | } |
703 | skip3: |
704 | if (/*ts->size2 < BUFSIZE &&*/ FD_ISSET(ts->ptyfd, &rdfdset)) { |
705 | /* Read from pty to buffer 2 */ |
706 | count = MIN(BUFSIZE - ts->rdidx2, BUFSIZE - ts->size2); |
707 | count = safe_read(ts->ptyfd, TS_BUF2(ts) + ts->rdidx2, count); |
708 | if (count <= 0) { |
709 | if (count < 0 && errno == EAGAIN) |
710 | goto skip4; |
711 | goto kill_session; |
712 | } |
713 | ts->size2 += count; |
714 | ts->rdidx2 += count; |
715 | if (ts->rdidx2 >= BUFSIZE) /* actually == BUFSIZE */ |
716 | ts->rdidx2 = 0; |
717 | } |
718 | skip4: |
719 | ts = next; |
720 | continue; |
721 | kill_session: |
722 | if (ts->shell_pid > 0) |
723 | update_utmp(ts->shell_pid, DEAD_PROCESS, /*tty_name:*/ NULL, /*username:*/ NULL, /*hostname:*/ NULL); |
724 | free_session(ts); |
725 | ts = next; |
726 | } |
727 | |
728 | goto again; |
729 | } |