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Date:: Fri Jan 29 17:29:14 2021 UTC
Message:: don't ignore punycode errors when decoding SNI-provided servname
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1 /*
2  * Copyright (c) 2021 Omar Polo <op@omarpolo.com>
3  *
4  * Permission to use, copy, modify, and distribute this software for any
5  * purpose with or without fee is hereby granted, provided that the above
6  * copyright notice and this permission notice appear in all copies.
7  *
8  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
9  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
10  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
11  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
12  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
13  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
14  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
15  */
16 
17 #include <sys/mman.h>
18 #include <sys/stat.h>
19 
20 #include <netdb.h>
21 
22 #include <assert.h>
23 #include <errno.h>
24 #include <fcntl.h>
25 #include <fnmatch.h>
26 #include <string.h>
27 
28 #include "gmid.h"
29 
30 int connected_clients;
31 
32 const char *
33 vhost_lang(struct vhost *v, const char *path)
34 {
35 	struct location *loc;
36 	const char *lang = NULL;
37 
38 	if (v == NULL || path == NULL)
39 		return lang;
40 
41 	for (loc = v->locations; loc->match != NULL; ++loc) {
42 		if (!fnmatch(loc->match, path, 0)) {
43 			if (loc->lang != NULL)
44 				lang = loc->lang;
45 		}
46 	}
47 
48 	return lang;
49 }
50 
51 const char *
52 vhost_default_mime(struct vhost *v, const char *path)
53 {
54 	struct location *loc;
55 	const char *default_mime = "application/octet-stream";
56 
57 	if (v == NULL || path == NULL)
58 		return default_mime;
59 
60 	for (loc = v->locations; loc->match != NULL; ++loc) {
61 		if (!fnmatch(loc->match, path, 0)) {
62 			if (loc->default_mime != NULL)
63 				default_mime = loc->default_mime;
64 		}
65 	}
66 
67 	return default_mime;
68 }
69 
70 const char *
71 vhost_index(struct vhost *v, const char *path)
72 {
73 	struct location *loc;
74 	const char *index = "index.gmi";
75 
76 	if (v == NULL || path == NULL)
77 		return index;
78 
79 	for (loc = v->locations; loc->match != NULL; ++loc) {
80 		if (!fnmatch(loc->match, path, 0)) {
81 			if (loc->index != NULL)
82 				index = loc->index;
83 		}
84 	}
85 
86 	return index;
87 }
88 
89 int
90 vhost_auto_index(struct vhost *v, const char *path)
91 {
92 	struct location *loc;
93 	int auto_index = 0;
94 
95 	for (loc = v->locations; loc->match != NULL; ++loc) {
96 		if (!fnmatch(loc->match, path, 0)) {
97 			if (loc->auto_index)
98 				auto_index = loc->auto_index;
99 		}
100 	}
101 
102 	return auto_index == 1;
103 }
104 
105 int
106 check_path(struct client *c, const char *path, int *fd)
107 {
108 	struct stat sb;
109 	const char *p;
110 	int flags;
111 
112 	assert(path != NULL);
113 
114 	if (*path == '\0')
115 		p = ".";
116 	else if (*path == '/')
117 		/* in send_dir we add an initial / (to be
118 		 * redirect-friendly), but here we want to skip it */
119 		p = path+1;
120 	else
121 		p = path;
122 
123 	flags = O_RDONLY | O_NOFOLLOW;
124 
125 	if (*fd == -1 && (*fd = openat(c->host->dirfd, p, flags)) == -1)
126 		return FILE_MISSING;
127 
128 	if (fstat(*fd, &sb) == -1) {
129 		LOGN(c, "failed stat for %s: %s", path, strerror(errno));
130 		return FILE_MISSING;
131 	}
132 
133 	if (S_ISDIR(sb.st_mode))
134 		return FILE_DIRECTORY;
135 
136 	if (sb.st_mode & S_IXUSR)
137 		return FILE_EXECUTABLE;
138 
139 	return FILE_EXISTS;
140 }
141 
142 void
143 open_file(struct pollfd *fds, struct client *c)
144 {
145 	switch (check_path(c, c->iri.path, &c->fd)) {
146 	case FILE_EXECUTABLE:
147 		if (starts_with(c->iri.path, c->host->cgi)) {
148 			start_cgi(c->iri.path, "", c->iri.query, fds, c);
149 			return;
150 		}
151 
152 		/* fallthrough */
153 
154 	case FILE_EXISTS:
155 		load_file(fds, c);
156 		return;
157 
158 	case FILE_DIRECTORY:
159 		open_dir(fds, c);
160 		return;
161 
162 	case FILE_MISSING:
163 		if (c->host->cgi != NULL && starts_with(c->iri.path, c->host->cgi)) {
164 			check_for_cgi(c->iri.path, c->iri.query, fds, c);
165 			return;
166 		}
167 		start_reply(fds, c, NOT_FOUND, "not found");
168 		return;
169 
170 	default:
171 		/* unreachable */
172 		abort();
173 	}
174 }
175 
176 void
177 load_file(struct pollfd *fds, struct client *c)
178 {
179 	if ((c->len = filesize(c->fd)) == -1) {
180 		LOGE(c, "failed to get file size for %s", c->iri.path);
181 		start_reply(fds, c, TEMP_FAILURE, "internal server error");
182 		return;
183 	}
184 
185 	if ((c->buf = mmap(NULL, c->len, PROT_READ, MAP_PRIVATE,
186 		    c->fd, 0)) == MAP_FAILED) {
187 		LOGW(c, "mmap: %s: %s", c->iri.path, strerror(errno));
188 		start_reply(fds, c, TEMP_FAILURE, "internal server error");
189 		return;
190 	}
191 	c->i = c->buf;
192 	c->next = S_SENDING_FILE;
193 	start_reply(fds, c, SUCCESS, mime(c->host, c->iri.path));
194 }
195 
196 /*
197  * the inverse of this algorithm, i.e. starting from the start of the
198  * path + strlen(cgi), and checking if each component, should be
199  * faster.  But it's tedious to write.  This does the opposite: starts
200  * from the end and strip one component at a time, until either an
201  * executable is found or we emptied the path.
202  */
203 void
204 check_for_cgi(char *path, char *query, struct pollfd *fds, struct client *c)
205 {
206 	char *end;
207 	end = strchr(path, '\0');
208 
209 	/* NB: assume CGI is enabled and path matches cgi */
210 
211 	while (end > path) {
212 		/* go up one level.  UNIX paths are simple and POSIX
213 		 * dirname, with its ambiguities on if the given path
214 		 * is changed or not, gives me headaches. */
215 		while (*end != '/')
216 			end--;
217 		*end = '\0';
218 
219 		switch (check_path(c, path, &c->fd)) {
220 		case FILE_EXECUTABLE:
221 			start_cgi(path, end+1, query, fds,c);
222 			return;
223 		case FILE_MISSING:
224 			break;
225 		default:
226 			goto err;
227 		}
228 
229 		*end = '/';
230 		end--;
231 	}
232 
233 err:
234 	start_reply(fds, c, NOT_FOUND, "not found");
235 	return;
236 }
237 
238 void
239 mark_nonblock(int fd)
240 {
241 	int flags;
242 
243 	if ((flags = fcntl(fd, F_GETFL)) == -1)
244 		fatal("fcntl(F_GETFL): %s", strerror(errno));
245 	if (fcntl(fd, F_SETFL, flags | O_NONBLOCK) == -1)
246 		fatal("fcntl(F_SETFL): %s", strerror(errno));
247 }
248 
249 void
250 handle_handshake(struct pollfd *fds, struct client *c)
251 {
252 	struct vhost *h;
253 	const char *servname;
254 	const char *parse_err = "unknown error";
255 
256 	switch (tls_handshake(c->ctx)) {
257 	case 0:  /* success */
258 	case -1: /* already handshaked */
259 		break;
260 	case TLS_WANT_POLLIN:
261 		fds->events = POLLIN;
262 		return;
263 	case TLS_WANT_POLLOUT:
264 		fds->events = POLLOUT;
265 		return;
266 	default:
267 		/* unreachable */
268 		abort();
269 	}
270 
271 	servname = tls_conn_servername(c->ctx);
272 	if (!puny_decode(servname, c->domain, sizeof(c->domain), &parse_err)) {
273 		LOGI(c, "%s", parse_err);
274 		goto err;
275 	}
276 
277 	for (h = hosts; h->domain != NULL; ++h) {
278 		if (!fnmatch(h->domain, c->domain, 0))
279 			break;
280 	}
281 
282 	/* LOGD(c, "handshake: SNI: \"%s\"; decoded: \"%s\"; matched: \"%s\"", */
283 	/*     servname != NULL ? servname : "(null)", */
284 	/*     c->domain, */
285 	/*     h->domain != NULL ? h->domain : "(null)"); */
286 
287 	if (h->domain != NULL) {
288 		c->state = S_OPEN;
289 		c->host = h;
290 		handle_open_conn(fds, c);
291 		return;
292 	}
293 
294 err:
295 	if (servname != NULL)
296 		strncpy(c->req, servname, sizeof(c->req));
297 	else
298 		strncpy(c->req, "null", sizeof(c->req));
299 
300 	start_reply(fds, c, BAD_REQUEST, "Wrong/malformed host or missing SNI");
301 }
302 
303 void
304 handle_open_conn(struct pollfd *fds, struct client *c)
305 {
306 	const char *parse_err = "invalid request";
307 	char decoded[DOMAIN_NAME_LEN];
308 
309 	bzero(c->req, sizeof(c->req));
310 	bzero(&c->iri, sizeof(c->iri));
311 
312 	switch (tls_read(c->ctx, c->req, sizeof(c->req)-1)) {
313 	case -1:
314 		LOGE(c, "tls_read: %s", tls_error(c->ctx));
315 		close_conn(fds, c);
316 		return;
317 
318 	case TLS_WANT_POLLIN:
319 		fds->events = POLLIN;
320 		return;
321 
322 	case TLS_WANT_POLLOUT:
323 		fds->events = POLLOUT;
324 		return;
325 	}
326 
327 	if (!trim_req_iri(c->req, &parse_err)
328 	    || !parse_iri(c->req, &c->iri, &parse_err)
329 	    || !puny_decode(c->iri.host, decoded, sizeof(decoded), &parse_err)) {
330 		LOGI(c, "iri parse error: %s", parse_err);
331 		start_reply(fds, c, BAD_REQUEST, "invalid request");
332 		return;
333 	}
334 
335 	if (c->iri.port_no != conf.port
336 	    || strcmp(c->iri.schema, "gemini")
337 	    || strcmp(decoded, c->domain)) {
338 		start_reply(fds, c, PROXY_REFUSED, "won't proxy request");
339 		return;
340 	}
341 
342 	open_file(fds, c);
343 }
344 
345 void
346 start_reply(struct pollfd *pfd, struct client *c, int code, const char *meta)
347 {
348 	char buf[1030];		/* status + ' ' + max reply len + \r\n\0 */
349 	const char *lang;
350 	size_t len;
351 
352 	c->code = code;
353 	c->meta = meta;
354 	c->state = S_INITIALIZING;
355 
356 	lang = vhost_lang(c->host, c->iri.path);
357 
358 	snprintf(buf, sizeof(buf), "%d ", code);
359 	strlcat(buf, meta, sizeof(buf));
360 	if (!strcmp(meta, "text/gemini") && lang != NULL) {
361 		strlcat(buf, "; lang=", sizeof(buf));
362 		strlcat(buf, lang, sizeof(buf));
363 	}
364 
365 	len = strlcat(buf, "\r\n", sizeof(buf));
366 	assert(len < sizeof(buf));
367 
368 	switch (tls_write(c->ctx, buf, len)) {
369 	case -1:
370 		close_conn(pfd, c);
371 		return;
372 	case TLS_WANT_POLLIN:
373 		pfd->events = POLLIN;
374 		return;
375 	case TLS_WANT_POLLOUT:
376 		pfd->events = POLLOUT;
377 		return;
378 	}
379 
380 	log_request(c, buf, sizeof(buf));
381 
382 	/* we don't need a body */
383 	if (c->code != SUCCESS) {
384 		close_conn(pfd, c);
385 		return;
386 	}
387 
388 	/* advance the state machine */
389 	c->state = c->next;
390 	handle(pfd, c);
391 }
392 
393 void
394 start_cgi(const char *spath, const char *relpath, const char *query,
395     struct pollfd *fds, struct client *c)
396 {
397 	char addr[NI_MAXHOST];
398 	const char *ruser, *cissuer, *chash;
399 	int e;
400 
401 	e = getnameinfo((struct sockaddr*)&c->addr, sizeof(c->addr),
402 	    addr, sizeof(addr),
403 	    NULL, 0,
404 	    NI_NUMERICHOST);
405 	if (e != 0)
406 		goto err;
407 
408 	if (tls_peer_cert_provided(c->ctx)) {
409 		ruser = tls_peer_cert_subject(c->ctx);
410 		cissuer = tls_peer_cert_issuer(c->ctx);
411 		chash = tls_peer_cert_hash(c->ctx);
412 	} else {
413 		ruser = NULL;
414 		cissuer = NULL;
415 		chash = NULL;
416 	}
417 
418 	if (!send_string(exfd, spath)
419 	    || !send_string(exfd, relpath)
420 	    || !send_string(exfd, query)
421 	    || !send_string(exfd, addr)
422 	    || !send_string(exfd, ruser)
423 	    || !send_string(exfd, cissuer)
424 	    || !send_string(exfd, chash)
425 	    || !send_vhost(exfd, c->host))
426 		goto err;
427 
428 	close(c->fd);
429 	if ((c->fd = recv_fd(exfd)) == -1) {
430 		start_reply(fds, c, TEMP_FAILURE, "internal server error");
431 		return;
432 	}
433 	c->state = S_SENDING_CGI;
434 	cgi_poll_on_child(fds, c);
435 	c->code = -1;
436 	/* handle_cgi(fds, c); */
437 	return;
438 
439 err:
440 	/* fatal("cannot talk to the executor process: %s", strerror(errno)); */
441 	fatal("cannot talk to the executor process");
442 }
443 
444 void
445 send_file(struct pollfd *fds, struct client *c)
446 {
447 	ssize_t ret, len;
448 
449 	/* ensure the correct state */
450 	c->state = S_SENDING_FILE;
451 
452 	len = (c->buf + c->len) - c->i;
453 
454 	while (len > 0) {
455 		switch (ret = tls_write(c->ctx, c->i, len)) {
456 		case -1:
457 			LOGE(c, "tls_write: %s", tls_error(c->ctx));
458 			close_conn(fds, c);
459 			return;
460 
461 		case TLS_WANT_POLLIN:
462 			fds->events = POLLIN;
463 			return;
464 
465 		case TLS_WANT_POLLOUT:
466 			fds->events = POLLOUT;
467 			return;
468 
469 		default:
470 			c->i += ret;
471 			len -= ret;
472 			break;
473 		}
474 	}
475 
476 	close_conn(fds, c);
477 }
478 
479 void
480 open_dir(struct pollfd *fds, struct client *c)
481 {
482 	size_t len;
483 	int dirfd;
484 	char *before_file;
485 
486 	len = strlen(c->iri.path);
487 	if (len > 0 && !ends_with(c->iri.path, "/")) {
488 		redirect_canonical_dir(fds, c);
489 		return;
490 	}
491 
492 	strlcpy(c->sbuf, "/", sizeof(c->sbuf));
493 	strlcat(c->sbuf, c->iri.path, sizeof(c->sbuf));
494 	if (!ends_with(c->sbuf, "/"))
495 		strlcat(c->sbuf, "/", sizeof(c->sbuf));
496 	before_file = strchr(c->sbuf, '\0');
497 	len = strlcat(c->sbuf, vhost_index(c->host, c->iri.path),
498 	    sizeof(c->sbuf));
499 	if (len >= sizeof(c->sbuf)) {
500 		start_reply(fds, c, TEMP_FAILURE, "internal server error");
501 		return;
502 	}
503 
504 	c->iri.path = c->sbuf;
505 
506 	/* close later unless we have to generate the dir listing */
507 	dirfd = c->fd;
508 	c->fd = -1;
509 
510 	switch (check_path(c, c->iri.path, &c->fd)) {
511 	case FILE_EXECUTABLE:
512 		if (starts_with(c->iri.path, c->host->cgi)) {
513 			start_cgi(c->iri.path, "", c->iri.query, fds, c);
514 			break;
515 		}
516 
517 		/* fallthrough */
518 
519 	case FILE_EXISTS:
520                 load_file(fds, c);
521 		break;
522 
523 	case FILE_DIRECTORY:
524 		start_reply(fds, c, TEMP_REDIRECT, c->sbuf);
525 		break;
526 
527 	case FILE_MISSING:
528 		*before_file = '\0';
529 
530 		if (!vhost_auto_index(c->host, c->iri.path)) {
531 			start_reply(fds, c, NOT_FOUND, "not found");
532 			break;
533 		}
534 
535 		c->fd = dirfd;
536 		c->next = S_SENDING_DIR;
537 
538 		if ((c->dir = fdopendir(c->fd)) == NULL) {
539 			LOGE(c, "can't fdopendir(%d) (vhost:%s) %s: %s",
540 			    c->fd, c->host->domain, c->iri.path, strerror(errno));
541 			start_reply(fds, c, TEMP_FAILURE, "internal server error");
542 			return;
543 		}
544 		c->off = 0;
545 
546                 start_reply(fds, c, SUCCESS, "text/gemini");
547 		return;
548 
549 	default:
550 		/* unreachable */
551 		abort();
552 	}
553 
554 	close(dirfd);
555 }
556 
557 void
558 redirect_canonical_dir(struct pollfd *fds, struct client *c)
559 {
560 	size_t len;
561 
562 	strlcpy(c->sbuf, "/", sizeof(c->sbuf));
563 	strlcat(c->sbuf, c->iri.path, sizeof(c->sbuf));
564 	len = strlcat(c->sbuf, "/", sizeof(c->sbuf));
565 
566 	if (len >= sizeof(c->sbuf)) {
567 		start_reply(fds, c, TEMP_FAILURE, "internal server error");
568 		return;
569 	}
570 
571 	start_reply(fds, c, TEMP_REDIRECT, c->sbuf);
572 }
573 
574 int
575 read_next_dir_entry(struct client *c)
576 {
577 	struct dirent *d;
578 
579 	do {
580 		errno = 0;
581 		if ((d = readdir(c->dir)) == NULL) {
582 			if (errno != 0)
583 				LOGE(c, "readdir: %s", strerror(errno));
584 			return 0;
585 		}
586 	} while (!strcmp(d->d_name, "."));
587 
588 	/* XXX: url escape */
589 	snprintf(c->sbuf, sizeof(c->sbuf), "=> %s %s\n",
590 	    d->d_name, d->d_name);
591 	c->len = strlen(c->sbuf);
592 	c->off = 0;
593 
594 	return 1;
595 }
596 
597 void
598 send_directory_listing(struct pollfd *fds, struct client *c)
599 {
600 	ssize_t r;
601 
602 	while (1) {
603 		if (c->len == 0) {
604 			if (!read_next_dir_entry(c))
605 				goto end;
606 		}
607 
608 		while (c->len > 0) {
609 			switch (r = tls_write(c->ctx, c->sbuf + c->off, c->len)) {
610 			case -1:
611 				goto end;
612 
613 			case TLS_WANT_POLLOUT:
614 				fds->events = POLLOUT;
615 				return;
616 
617 			case TLS_WANT_POLLIN:
618 				fds->events = POLLIN;
619 				return;
620 
621 			default:
622 				c->off += r;
623 				c->len -= r;
624 				break;
625 			}
626 		}
627 	}
628 
629 end:
630 	close_conn(fds, c);
631 }
632 
633 void
634 cgi_poll_on_child(struct pollfd *fds, struct client *c)
635 {
636 	int fd;
637 
638 	if (c->waiting_on_child)
639 		return;
640 	c->waiting_on_child = 1;
641 
642 	fds->events = POLLIN;
643 
644 	fd = fds->fd;
645 	fds->fd = c->fd;
646 	c->fd = fd;
647 }
648 
649 void
650 cgi_poll_on_client(struct pollfd *fds, struct client *c)
651 {
652 	int fd;
653 
654 	if (!c->waiting_on_child)
655 		return;
656 	c->waiting_on_child = 0;
657 
658 	fd = fds->fd;
659 	fds->fd = c->fd;
660 	c->fd = fd;
661 }
662 
663 /* handle the read from the child process.  Return like read(2) */
664 static ssize_t
665 read_from_cgi(struct client *c)
666 {
667 	void	*buf;
668 	size_t	 len;
669 	ssize_t	 r;
670 
671 	/* if we haven't read a whole response line, we want to
672 	 * continue reading. */
673 
674 	if (c->code == -1) {
675 		buf = c->sbuf + c->len;
676 		len = sizeof(c->sbuf) - c->len;
677 	} else {
678 		buf = c->sbuf;
679 		len = sizeof(c->sbuf);
680 	}
681 
682 	r = read(c->fd, buf, len);
683 	if (r == 0 || r == -1)
684 		return r;
685 
686 	c->len += r;
687 	c->off = 0;
688 
689 	if (c->code != -1)
690 		return r;
691 
692 	if (strchr(c->sbuf, '\n') || c->len == sizeof(c->sbuf)) {
693 		c->code = 0;
694 		log_request(c, c->sbuf, c->len);
695 	}
696 
697 	return r;
698 }
699 
700 void
701 handle_cgi(struct pollfd *fds, struct client *c)
702 {
703 	ssize_t r;
704 
705 	/* ensure c->fd is the child and fds->fd the client */
706 	cgi_poll_on_client(fds, c);
707 
708 	while (1) {
709 		if (c->code == -1 || c->len == 0) {
710 			switch (r = read_from_cgi(c)) {
711 			case 0:
712 				goto end;
713 
714 			case -1:
715 				if (errno == EAGAIN || errno == EWOULDBLOCK) {
716 					cgi_poll_on_child(fds, c);
717 					return;
718 				}
719 				goto end;
720 			}
721 		}
722 
723 		if (c->code == -1) {
724 			cgi_poll_on_child(fds, c);
725 			return;
726 		}
727 
728 		while (c->len > 0) {
729 			switch (r = tls_write(c->ctx, c->sbuf + c->off, c->len)) {
730 			case -1:
731 				goto end;
732 
733 			case TLS_WANT_POLLOUT:
734 				fds->events = POLLOUT;
735 				return;
736 
737 			case TLS_WANT_POLLIN:
738 				fds->events = POLLIN;
739 				return;
740 
741 			default:
742                                 c->off += r;
743 				c->len -= r;
744 				break;
745 			}
746 		}
747 	}
748 
749 end:
750 	close_conn(fds, c);
751 }
752 
753 void
754 close_conn(struct pollfd *pfd, struct client *c)
755 {
756 	c->state = S_CLOSING;
757 
758 	switch (tls_close(c->ctx)) {
759 	case TLS_WANT_POLLIN:
760 		pfd->events = POLLIN;
761 		return;
762 	case TLS_WANT_POLLOUT:
763 		pfd->events = POLLOUT;
764 		return;
765 	}
766 
767 	connected_clients--;
768 
769 	tls_free(c->ctx);
770 	c->ctx = NULL;
771 
772 	if (c->buf != MAP_FAILED)
773 		munmap(c->buf, c->len);
774 
775 	if (c->fd != -1)
776 		close(c->fd);
777 
778 	if (c->dir != NULL)
779 		closedir(c->dir);
780 
781 	close(pfd->fd);
782 	pfd->fd = -1;
783 }
784 
785 void
786 do_accept(int sock, struct tls *ctx, struct pollfd *fds, struct client *clients)
787 {
788 	int i, fd;
789 	struct sockaddr_storage addr;
790 	socklen_t len;
791 
792 	len = sizeof(addr);
793 	if ((fd = accept(sock, (struct sockaddr*)&addr, &len)) == -1) {
794 		if (errno == EWOULDBLOCK)
795 			return;
796 		fatal("accept: %s", strerror(errno));
797 	}
798 
799 	mark_nonblock(fd);
800 
801 	for (i = 0; i < MAX_USERS; ++i) {
802 		if (fds[i].fd == -1) {
803 			bzero(&clients[i], sizeof(struct client));
804 			if (tls_accept_socket(ctx, &clients[i].ctx, fd) == -1)
805 				break; /* goodbye fd! */
806 
807 			fds[i].fd = fd;
808 			fds[i].events = POLLIN;
809 
810 			clients[i].state = S_HANDSHAKE;
811 			clients[i].next = S_SENDING_FILE;
812 			clients[i].fd = -1;
813 			clients[i].waiting_on_child = 0;
814 			clients[i].buf = MAP_FAILED;
815 			clients[i].dir = NULL;
816 			clients[i].addr = addr;
817 
818 			connected_clients++;
819 			return;
820 		}
821 	}
822 
823 	close(fd);
824 }
825 
826 void
827 handle(struct pollfd *fds, struct client *client)
828 {
829 	switch (client->state) {
830 	case S_HANDSHAKE:
831 		handle_handshake(fds, client);
832 		break;
833 
834 	case S_OPEN:
835                 handle_open_conn(fds, client);
836 		break;
837 
838 	case S_INITIALIZING:
839 		start_reply(fds, client, client->code, client->meta);
840                 break;
841 
842 	case S_SENDING_FILE:
843 		send_file(fds, client);
844 		break;
845 
846 	case S_SENDING_DIR:
847 		send_directory_listing(fds, client);
848 		break;
849 
850 	case S_SENDING_CGI:
851 		handle_cgi(fds, client);
852 		break;
853 
854 	case S_CLOSING:
855 		close_conn(fds, client);
856 		break;
857 
858 	default:
859 		/* unreachable */
860 		abort();
861 	}
862 }
863 
864 void
865 loop(struct tls *ctx, int sock4, int sock6)
866 {
867 	int i;
868 	struct client clients[MAX_USERS];
869 	struct pollfd fds[MAX_USERS];
870 
871 	connected_clients = 0;
872 
873 	for (i = 0; i < MAX_USERS; ++i) {
874 		fds[i].fd = -1;
875 		fds[i].events = POLLIN;
876 		bzero(&clients[i], sizeof(struct client));
877 	}
878 
879 	fds[0].fd = sock4;
880 	fds[1].fd = sock6;
881 
882 	for (;;) {
883 		if (poll(fds, MAX_USERS, INFTIM) == -1) {
884 			if (errno == EINTR) {
885                                 fprintf(stderr, "connected clients: %d\n",
886 				    connected_clients);
887 				continue;
888 			}
889 			fatal("poll: %s", strerror(errno));
890 		}
891 
892 		for (i = 0; i < MAX_USERS; i++) {
893 			if (fds[i].revents == 0)
894 				continue;
895 
896 			if (fds[i].revents & (POLLERR|POLLNVAL))
897 				fatal("bad fd %d: %s", fds[i].fd,
898 				    strerror(errno));
899 
900 			if (fds[i].revents & POLLHUP) {
901 				/* fds[i] may be the fd of the stdin
902 				 * of a cgi script that has exited. */
903 				if (!clients[i].waiting_on_child) {
904 					close_conn(&fds[i], &clients[i]);
905 					continue;
906 				}
907 			}
908 
909 			if (fds[i].fd == sock4)
910 				do_accept(sock4, ctx, fds, clients);
911 			else if (fds[i].fd == sock6)
912 				do_accept(sock6, ctx, fds, clients);
913 			else
914 				handle(&fds[i], &clients[i]);
915 		}
916 	}
917 }