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Improve socket error handling so that a socket error isn't an
[u/mdw/putty] / telnet.c
1 #include <windows.h>
2 #include <stdio.h>
3 #include <stdlib.h>
4
5 #include "putty.h"
6
7 #ifndef FALSE
8 #define FALSE 0
9 #endif
10 #ifndef TRUE
11 #define TRUE 1
12 #endif
13
14 static Socket s = NULL;
15
16 #define IAC 255 /* interpret as command: */
17 #define DONT 254 /* you are not to use option */
18 #define DO 253 /* please, you use option */
19 #define WONT 252 /* I won't use option */
20 #define WILL 251 /* I will use option */
21 #define SB 250 /* interpret as subnegotiation */
22 #define SE 240 /* end sub negotiation */
23
24 #define GA 249 /* you may reverse the line */
25 #define EL 248 /* erase the current line */
26 #define EC 247 /* erase the current character */
27 #define AYT 246 /* are you there */
28 #define AO 245 /* abort output--but let prog finish */
29 #define IP 244 /* interrupt process--permanently */
30 #define BREAK 243 /* break */
31 #define DM 242 /* data mark--for connect. cleaning */
32 #define NOP 241 /* nop */
33 #define EOR 239 /* end of record (transparent mode) */
34 #define ABORT 238 /* Abort process */
35 #define SUSP 237 /* Suspend process */
36 #define xEOF 236 /* End of file: EOF is already used... */
37
38 #define TELOPT_BINARY 0 /* 8-bit data path */
39 #define TELOPT_ECHO 1 /* echo */
40 #define TELOPT_RCP 2 /* prepare to reconnect */
41 #define TELOPT_SGA 3 /* suppress go ahead */
42 #define TELOPT_NAMS 4 /* approximate message size */
43 #define TELOPT_STATUS 5 /* give status */
44 #define TELOPT_TM 6 /* timing mark */
45 #define TELOPT_RCTE 7 /* remote controlled transmission and echo */
46 #define TELOPT_NAOL 8 /* negotiate about output line width */
47 #define TELOPT_NAOP 9 /* negotiate about output page size */
48 #define TELOPT_NAOCRD 10 /* negotiate about CR disposition */
49 #define TELOPT_NAOHTS 11 /* negotiate about horizontal tabstops */
50 #define TELOPT_NAOHTD 12 /* negotiate about horizontal tab disposition */
51 #define TELOPT_NAOFFD 13 /* negotiate about formfeed disposition */
52 #define TELOPT_NAOVTS 14 /* negotiate about vertical tab stops */
53 #define TELOPT_NAOVTD 15 /* negotiate about vertical tab disposition */
54 #define TELOPT_NAOLFD 16 /* negotiate about output LF disposition */
55 #define TELOPT_XASCII 17 /* extended ascic character set */
56 #define TELOPT_LOGOUT 18 /* force logout */
57 #define TELOPT_BM 19 /* byte macro */
58 #define TELOPT_DET 20 /* data entry terminal */
59 #define TELOPT_SUPDUP 21 /* supdup protocol */
60 #define TELOPT_SUPDUPOUTPUT 22 /* supdup output */
61 #define TELOPT_SNDLOC 23 /* send location */
62 #define TELOPT_TTYPE 24 /* terminal type */
63 #define TELOPT_EOR 25 /* end or record */
64 #define TELOPT_TUID 26 /* TACACS user identification */
65 #define TELOPT_OUTMRK 27 /* output marking */
66 #define TELOPT_TTYLOC 28 /* terminal location number */
67 #define TELOPT_3270REGIME 29 /* 3270 regime */
68 #define TELOPT_X3PAD 30 /* X.3 PAD */
69 #define TELOPT_NAWS 31 /* window size */
70 #define TELOPT_TSPEED 32 /* terminal speed */
71 #define TELOPT_LFLOW 33 /* remote flow control */
72 #define TELOPT_LINEMODE 34 /* Linemode option */
73 #define TELOPT_XDISPLOC 35 /* X Display Location */
74 #define TELOPT_OLD_ENVIRON 36 /* Old - Environment variables */
75 #define TELOPT_AUTHENTICATION 37/* Authenticate */
76 #define TELOPT_ENCRYPT 38 /* Encryption option */
77 #define TELOPT_NEW_ENVIRON 39 /* New - Environment variables */
78 #define TELOPT_EXOPL 255 /* extended-options-list */
79
80 #define TELQUAL_IS 0 /* option is... */
81 #define TELQUAL_SEND 1 /* send option */
82 #define TELQUAL_INFO 2 /* ENVIRON: informational version of IS */
83 #define BSD_VAR 1
84 #define BSD_VALUE 0
85 #define RFC_VAR 0
86 #define RFC_VALUE 1
87
88 #define CR 13
89 #define LF 10
90 #define NUL 0
91
92 #define iswritable(x) ( (x) != IAC && (x) != CR )
93
94 static char *telopt(int opt) {
95 #define i(x) if (opt == TELOPT_ ## x) return #x;
96 i(BINARY); i(ECHO); i(RCP); i(SGA); i(NAMS); i(STATUS); i(TM); i(RCTE);
97 i(NAOL); i(NAOP); i(NAOCRD); i(NAOHTS); i(NAOHTD); i(NAOFFD); i(NAOVTS);
98 i(NAOVTD); i(NAOLFD); i(XASCII); i(LOGOUT); i(BM); i(DET); i(SUPDUP);
99 i(SUPDUPOUTPUT); i(SNDLOC); i(TTYPE); i(EOR); i(TUID); i(OUTMRK);
100 i(TTYLOC); i(X3PAD); i(NAWS); i(TSPEED); i(LFLOW); i(LINEMODE);
101 i(XDISPLOC); i(OLD_ENVIRON); i(AUTHENTICATION); i(ENCRYPT);
102 i(NEW_ENVIRON); i(EXOPL);
103 #undef i
104 return "<unknown>";
105 }
106
107 static void telnet_size(void);
108
109 struct Opt {
110 int send; /* what we initially send */
111 int nsend; /* -ve send if requested to stop it */
112 int ack, nak; /* +ve and -ve acknowledgements */
113 int option; /* the option code */
114 enum {
115 REQUESTED, ACTIVE, INACTIVE, REALLY_INACTIVE
116 } state;
117 };
118
119 static struct Opt o_naws = {WILL, WONT, DO, DONT, TELOPT_NAWS, REQUESTED};
120 static struct Opt o_tspeed = {WILL, WONT, DO, DONT, TELOPT_TSPEED, REQUESTED};
121 static struct Opt o_ttype = {WILL, WONT, DO, DONT, TELOPT_TTYPE, REQUESTED};
122 static struct Opt o_oenv = {WILL, WONT, DO, DONT, TELOPT_OLD_ENVIRON,
123 INACTIVE};
124 static struct Opt o_nenv = {WILL, WONT, DO, DONT, TELOPT_NEW_ENVIRON,
125 REQUESTED};
126 static struct Opt o_echo = {DO, DONT, WILL, WONT, TELOPT_ECHO, REQUESTED};
127 static struct Opt o_we_sga = {WILL, WONT, DO, DONT, TELOPT_SGA, REQUESTED};
128 static struct Opt o_they_sga = {DO, DONT, WILL, WONT, TELOPT_SGA, REQUESTED};
129
130 static struct Opt *opts[] = {
131 &o_naws, &o_tspeed, &o_ttype, &o_oenv, &o_nenv, &o_echo,
132 &o_we_sga, &o_they_sga, NULL
133 };
134
135 static int in_synch;
136 static int sb_opt, sb_len;
137 static char *sb_buf = NULL;
138 static int sb_size = 0;
139 #define SB_DELTA 1024
140
141 static void c_write1(int c) {
142 char cc = (char)c;
143 from_backend(0, &cc, 1);
144 }
145
146 static void log_option (char *sender, int cmd, int option) {
147 char buf[50];
148 sprintf(buf, "%s:\t%s %s", sender,
149 (cmd == WILL ? "WILL" : cmd == WONT ? "WONT" :
150 cmd == DO ? "DO" : cmd == DONT ? "DONT" : "<??>"),
151 telopt(option));
152 logevent(buf);
153 }
154
155 static void send_opt (int cmd, int option) {
156 unsigned char b[3];
157
158 b[0] = IAC; b[1] = cmd; b[2] = option;
159 sk_write(s, b, 3);
160 log_option("client", cmd, option);
161 }
162
163 static void deactivate_option (struct Opt *o) {
164 if (o->state == REQUESTED || o->state == ACTIVE)
165 send_opt (o->nsend, o->option);
166 o->state = REALLY_INACTIVE;
167 }
168
169 /*
170 * Generate side effects of enabling or disabling an option.
171 */
172 static void option_side_effects(struct Opt *o, int enabled) {
173 if (o->option == TELOPT_ECHO && cfg.ldisc_term)
174 ldisc = enabled ? &ldisc_simple : &ldisc_term;
175 }
176
177 static void activate_option (struct Opt *o) {
178 if (o->send == WILL && o->option == TELOPT_NAWS)
179 telnet_size();
180 if (o->send == WILL &&
181 (o->option == TELOPT_NEW_ENVIRON ||
182 o->option == TELOPT_OLD_ENVIRON)) {
183 /*
184 * We may only have one kind of ENVIRON going at a time.
185 * This is a hack, but who cares.
186 */
187 deactivate_option (o->option==TELOPT_NEW_ENVIRON ? &o_oenv : &o_nenv);
188 }
189 option_side_effects(o, 1);
190 }
191
192 static void refused_option (struct Opt *o) {
193 if (o->send == WILL && o->option == TELOPT_NEW_ENVIRON &&
194 o_oenv.state == INACTIVE) {
195 send_opt (WILL, TELOPT_OLD_ENVIRON);
196 o_oenv.state = REQUESTED;
197 }
198 option_side_effects(o, 0);
199 }
200
201 static void proc_rec_opt (int cmd, int option) {
202 struct Opt **o;
203
204 log_option ("server", cmd, option);
205 for (o = opts; *o; o++) {
206 if ((*o)->option == option && (*o)->ack == cmd) {
207 switch ((*o)->state) {
208 case REQUESTED:
209 (*o)->state = ACTIVE;
210 activate_option (*o);
211 break;
212 case ACTIVE:
213 break;
214 case INACTIVE:
215 (*o)->state = ACTIVE;
216 send_opt ((*o)->send, option);
217 activate_option (*o);
218 break;
219 case REALLY_INACTIVE:
220 send_opt ((*o)->nsend, option);
221 break;
222 }
223 return;
224 } else if ((*o)->option == option && (*o)->nak == cmd) {
225 switch ((*o)->state) {
226 case REQUESTED:
227 (*o)->state = INACTIVE;
228 refused_option (*o);
229 break;
230 case ACTIVE:
231 (*o)->state = INACTIVE;
232 send_opt ((*o)->nsend, option);
233 option_side_effects(*o, 0);
234 break;
235 case INACTIVE:
236 case REALLY_INACTIVE:
237 break;
238 }
239 return;
240 }
241 }
242 /*
243 * If we reach here, the option was one we weren't prepared to
244 * cope with. So send a negative ack.
245 */
246 send_opt ((cmd == WILL ? DONT : WONT), option);
247 }
248
249 static void process_subneg (void) {
250 unsigned char b[2048], *p, *q;
251 int var, value, n;
252 char *e;
253
254 switch (sb_opt) {
255 case TELOPT_TSPEED:
256 if (sb_len == 1 && sb_buf[0] == TELQUAL_SEND) {
257 char logbuf[sizeof(cfg.termspeed)+80];
258 b[0] = IAC; b[1] = SB; b[2] = TELOPT_TSPEED;
259 b[3] = TELQUAL_IS;
260 strcpy(b+4, cfg.termspeed);
261 n = 4 + strlen(cfg.termspeed);
262 b[n] = IAC; b[n+1] = SE;
263 sk_write(s, b, n+2);
264 logevent("server:\tSB TSPEED SEND");
265 sprintf(logbuf, "client:\tSB TSPEED IS %s", cfg.termspeed);
266 logevent (logbuf);
267 } else
268 logevent ("server:\tSB TSPEED <something weird>");
269 break;
270 case TELOPT_TTYPE:
271 if (sb_len == 1 && sb_buf[0] == TELQUAL_SEND) {
272 char logbuf[sizeof(cfg.termtype)+80];
273 b[0] = IAC; b[1] = SB; b[2] = TELOPT_TTYPE;
274 b[3] = TELQUAL_IS;
275 for (n = 0; cfg.termtype[n]; n++)
276 b[n+4] = (cfg.termtype[n] >= 'a' && cfg.termtype[n] <= 'z' ?
277 cfg.termtype[n] + 'A'-'a' : cfg.termtype[n]);
278 b[n+4] = IAC; b[n+5] = SE;
279 sk_write(s, b, n+6);
280 b[n+4] = 0;
281 logevent("server:\tSB TTYPE SEND");
282 sprintf(logbuf, "client:\tSB TTYPE IS %s", b+4);
283 logevent(logbuf);
284 } else
285 logevent("server:\tSB TTYPE <something weird>\r\n");
286 break;
287 case TELOPT_OLD_ENVIRON:
288 case TELOPT_NEW_ENVIRON:
289 p = sb_buf;
290 q = p + sb_len;
291 if (p < q && *p == TELQUAL_SEND) {
292 char logbuf[50];
293 p++;
294 sprintf (logbuf, "server:\tSB %s SEND", telopt(sb_opt));
295 logevent (logbuf);
296 if (sb_opt == TELOPT_OLD_ENVIRON) {
297 if (cfg.rfc_environ) {
298 value = RFC_VALUE;
299 var = RFC_VAR;
300 } else {
301 value = BSD_VALUE;
302 var = BSD_VAR;
303 }
304 /*
305 * Try to guess the sense of VAR and VALUE.
306 */
307 while (p < q) {
308 if (*p == RFC_VAR) {
309 value = RFC_VALUE;
310 var = RFC_VAR;
311 } else if (*p == BSD_VAR) {
312 value = BSD_VALUE;
313 var = BSD_VAR;
314 }
315 p++;
316 }
317 } else {
318 /*
319 * With NEW_ENVIRON, the sense of VAR and VALUE
320 * isn't in doubt.
321 */
322 value = RFC_VALUE;
323 var = RFC_VAR;
324 }
325 b[0] = IAC; b[1] = SB; b[2] = sb_opt;
326 b[3] = TELQUAL_IS;
327 n = 4;
328 e = cfg.environmt;
329 while (*e) {
330 b[n++] = var;
331 while (*e && *e != '\t') b[n++] = *e++;
332 if (*e == '\t') e++;
333 b[n++] = value;
334 while (*e) b[n++] = *e++;
335 e++;
336 }
337 if (*cfg.username) {
338 b[n++] = var; b[n++] = 'U'; b[n++] = 'S';
339 b[n++] = 'E'; b[n++] = 'R'; b[n++] = value;
340 e = cfg.username;
341 while (*e) b[n++] = *e++;
342 }
343 b[n++] = IAC; b[n++] = SE;
344 sk_write(s, b, n);
345 sprintf(logbuf, "client:\tSB %s IS %s", telopt(sb_opt),
346 n==6 ? "<nothing>" : "<stuff>");
347 logevent (logbuf);
348 }
349 break;
350 }
351 }
352
353 static enum {
354 TOPLEVEL, SEENIAC, SEENWILL, SEENWONT, SEENDO, SEENDONT,
355 SEENSB, SUBNEGOT, SUBNEG_IAC, SEENCR
356 } telnet_state = TOPLEVEL;
357
358 static void do_telnet_read (char *buf, int len) {
359
360 while (len--) {
361 int c = (unsigned char) *buf++;
362
363 switch (telnet_state) {
364 case TOPLEVEL:
365 case SEENCR:
366 if (c == NUL && telnet_state == SEENCR)
367 telnet_state = TOPLEVEL;
368 else if (c == IAC)
369 telnet_state = SEENIAC;
370 else {
371 if (!in_synch)
372 c_write1(c);
373
374 #if 1
375 /* I can't get the F***ing winsock to insert the urgent IAC
376 * into the right position! Even with SO_OOBINLINE it gives
377 * it to recv too soon. And of course the DM byte (that
378 * arrives in the same packet!) appears several K later!!
379 *
380 * Oh well, we do get the DM in the right place so I'll
381 * just stop hiding on the next 0xf2 and hope for the best.
382 */
383 else if (c == DM) in_synch = 0;
384 #endif
385 if (c == CR)
386 telnet_state = SEENCR;
387 else
388 telnet_state = TOPLEVEL;
389 }
390 break;
391 case SEENIAC:
392 if (c == DO) telnet_state = SEENDO;
393 else if (c == DONT) telnet_state = SEENDONT;
394 else if (c == WILL) telnet_state = SEENWILL;
395 else if (c == WONT) telnet_state = SEENWONT;
396 else if (c == SB) telnet_state = SEENSB;
397 else if (c == DM) {
398 in_synch = 0;
399 telnet_state = TOPLEVEL;
400 }
401 else {
402 /* ignore everything else; print it if it's IAC */
403 if (c == IAC) {
404 c_write1(c);
405 }
406 telnet_state = TOPLEVEL;
407 }
408 break;
409 case SEENWILL:
410 proc_rec_opt (WILL, c);
411 telnet_state = TOPLEVEL;
412 break;
413 case SEENWONT:
414 proc_rec_opt (WONT, c);
415 telnet_state = TOPLEVEL;
416 break;
417 case SEENDO:
418 proc_rec_opt (DO, c);
419 telnet_state = TOPLEVEL;
420 break;
421 case SEENDONT:
422 proc_rec_opt (DONT, c);
423 telnet_state = TOPLEVEL;
424 break;
425 case SEENSB:
426 sb_opt = c;
427 sb_len = 0;
428 telnet_state = SUBNEGOT;
429 break;
430 case SUBNEGOT:
431 if (c == IAC)
432 telnet_state = SUBNEG_IAC;
433 else {
434 subneg_addchar:
435 if (sb_len >= sb_size) {
436 char *newbuf;
437 sb_size += SB_DELTA;
438 newbuf = (sb_buf ?
439 srealloc(sb_buf, sb_size) :
440 smalloc(sb_size));
441 if (newbuf)
442 sb_buf = newbuf;
443 else
444 sb_size -= SB_DELTA;
445 }
446 if (sb_len < sb_size)
447 sb_buf[sb_len++] = c;
448 telnet_state = SUBNEGOT;/* in case we came here by goto */
449 }
450 break;
451 case SUBNEG_IAC:
452 if (c != SE)
453 goto subneg_addchar; /* yes, it's a hack, I know, but... */
454 else {
455 process_subneg();
456 telnet_state = TOPLEVEL;
457 }
458 break;
459 }
460 }
461 }
462
463 static int telnet_receive(Socket s, int urgent, char *data, int len) {
464 if (urgent==3) {
465 /* A socket error has occurred. */
466 connection_fatal(data);
467 len = 0;
468 }
469 if (!len) {
470 /* Connection has closed. */
471 sk_close(s);
472 s = NULL;
473 return 0;
474 }
475 do_telnet_read (data, len);
476 return 1;
477 }
478
479 /*
480 * Called to set up the Telnet connection.
481 *
482 * Returns an error message, or NULL on success.
483 *
484 * Also places the canonical host name into `realhost'.
485 */
486 static char *telnet_init (char *host, int port, char **realhost) {
487 SockAddr addr;
488 char *err;
489
490 /*
491 * Try to find host.
492 */
493 addr = sk_namelookup(host, realhost);
494 if ( (err = sk_addr_error(addr)) )
495 return err;
496
497 if (port < 0)
498 port = 23; /* default telnet port */
499
500 /*
501 * Open socket.
502 */
503 s = sk_new(addr, port, 0, telnet_receive);
504 if ( (err = sk_socket_error(s)) )
505 return err;
506
507 sk_addr_free(addr);
508
509 /*
510 * Initialise option states.
511 */
512 if( cfg.ldisc_term )
513 {
514 struct Opt **o;
515
516 for (o = opts; *o; o++)
517 if ((*o)->state == REQUESTED)
518 (*o)->state = INACTIVE;
519 }
520 else
521 {
522 struct Opt **o;
523
524 for (o = opts; *o; o++)
525 if ((*o)->state == REQUESTED)
526 send_opt ((*o)->send, (*o)->option);
527 }
528
529 /*
530 * Set up SYNCH state.
531 */
532 in_synch = FALSE;
533
534 /*
535 * We have no pre-session phase.
536 */
537 begin_session();
538
539 return NULL;
540 }
541
542 /*
543 * Called to send data down the Telnet connection.
544 */
545 static void telnet_send (char *buf, int len) {
546 char *p;
547 static unsigned char iac[2] = { IAC, IAC };
548 static unsigned char cr[2] = { CR, NUL };
549 static unsigned char nl[2] = { CR, LF };
550
551 if (s == NULL)
552 return;
553
554 p = buf;
555 while (p < buf+len) {
556 char *q = p;
557
558 while (iswritable((unsigned char)*p) && p < buf+len) p++;
559 sk_write(s, q, p-q);
560
561 while (p < buf+len && !iswritable((unsigned char)*p)) {
562 sk_write(s, (unsigned char)*p == IAC ? iac : nl, 2);
563 p++;
564 }
565 }
566 }
567
568 /*
569 * Called to set the size of the window from Telnet's POV.
570 */
571 static void telnet_size(void) {
572 unsigned char b[16];
573 char logbuf[50];
574
575 if (s == NULL || o_naws.state != ACTIVE)
576 return;
577 b[0] = IAC; b[1] = SB; b[2] = TELOPT_NAWS;
578 b[3] = cols >> 8; b[4] = cols & 0xFF;
579 b[5] = rows >> 8; b[6] = rows & 0xFF;
580 b[7] = IAC; b[8] = SE;
581 sk_write(s, b, 9);
582 sprintf(logbuf, "client:\tSB NAWS %d,%d",
583 ((unsigned char)b[3] << 8) + (unsigned char)b[4],
584 ((unsigned char)b[5] << 8) + (unsigned char)b[6]);
585 logevent (logbuf);
586 }
587
588 /*
589 * Send Telnet special codes.
590 */
591 static void telnet_special (Telnet_Special code) {
592 unsigned char b[2];
593
594 if (s == NULL)
595 return;
596
597 b[0] = IAC;
598 switch (code) {
599 case TS_AYT: b[1] = AYT; sk_write(s, b, 2); break;
600 case TS_BRK: b[1] = BREAK; sk_write(s, b, 2); break;
601 case TS_EC: b[1] = EC; sk_write(s, b, 2); break;
602 case TS_EL: b[1] = EL; sk_write(s, b, 2); break;
603 case TS_GA: b[1] = GA; sk_write(s, b, 2); break;
604 case TS_NOP: b[1] = NOP; sk_write(s, b, 2); break;
605 case TS_ABORT: b[1] = ABORT; sk_write(s, b, 2); break;
606 case TS_AO: b[1] = AO; sk_write(s, b, 2); break;
607 case TS_IP: b[1] = IP; sk_write(s, b, 2); break;
608 case TS_SUSP: b[1] = SUSP; sk_write(s, b, 2); break;
609 case TS_EOR: b[1] = EOR; sk_write(s, b, 2); break;
610 case TS_EOF: b[1] = xEOF; sk_write(s, b, 2); break;
611 case TS_SYNCH:
612 b[1] = DM;
613 sk_write (s, b, 1);
614 sk_write_oob (s, b+1, 1);
615 break;
616 case TS_RECHO:
617 if (o_echo.state == INACTIVE || o_echo.state == REALLY_INACTIVE) {
618 o_echo.state = REQUESTED;
619 send_opt (o_echo.send, o_echo.option);
620 }
621 break;
622 case TS_LECHO:
623 if (o_echo.state == ACTIVE) {
624 o_echo.state = REQUESTED;
625 send_opt (o_echo.nsend, o_echo.option);
626 }
627 break;
628 case TS_PING:
629 if (o_they_sga.state == ACTIVE) {
630 b[1] = NOP;
631 sk_write(s, b, 2);
632 }
633 break;
634 }
635 }
636
637 static Socket telnet_socket(void) { return s; }
638
639 static int telnet_sendok(void) { return 1; }
640
641 Backend telnet_backend = {
642 telnet_init,
643 telnet_send,
644 telnet_size,
645 telnet_special,
646 telnet_socket,
647 telnet_sendok,
648 23
649 };
Local modifications for Simon Tatham's `PuTTY' SSH client and terminal emulator