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 "gmid.h"
18 
19 #include <sys/stat.h>
20 
21 #include <assert.h>
22 #include <errno.h>
23 #include <event.h>
24 #include <fcntl.h>
25 #include <fnmatch.h>
26 #include <limits.h>
27 #include <string.h>
28 
29 static struct client	 clients[MAX_USERS];
30 static struct tls	*ctx;
31 
32 static struct event e4, e6, imsgev, siginfo, sigusr2;
33 static int has_ipv6, has_siginfo;
34 
35 int connected_clients;
36 
37 static inline int matches(const char*, const char*);
38 
39 static inline void reschedule_read(int, struct client*, statefn);
40 static inline void reschedule_write(int, struct client*, statefn);
41 
42 static int	 check_path(struct client*, const char*, int*);
43 static void	 open_file(struct client*);
44 static void	 check_for_cgi(struct client*);
45 static void	 handle_handshake(int, short, void*);
46 static char	*strip_path(char*, int);
47 static void	 fmt_sbuf(const char*, struct client*, const char*);
48 static int	 apply_block_return(struct client*);
49 static int	 apply_require_ca(struct client*);
50 static void	 handle_open_conn(int, short, void*);
51 static void	 start_reply(struct client*, int, const char*);
52 static void	 handle_start_reply(int, short, void*);
53 static size_t	 host_nth(struct vhost*);
54 static void	 start_cgi(const char*, const char*, struct client*);
55 static void	 open_dir(struct client*);
56 static void	 redirect_canonical_dir(struct client*);
57 static void	 enter_handle_dirlist(int, short, void*);
58 static void	 handle_dirlist(int, short, void*);
59 static int 	 read_next_dir_entry(struct client*);
60 static void	 send_directory_listing(int, short, void*);
61 static void	 handle_cgi_reply(int, short, void*);
62 static void	 handle_copy(int, short, void*);
63 static void	 close_conn(int, short, void*);
64 static void	 do_accept(int, short, void*);
65 struct client	*client_by_id(int);
66 static void	 handle_imsg_cgi_res(struct imsgbuf*, struct imsg*, size_t);
67 static void	 handle_imsg_quit(struct imsgbuf*, struct imsg*, size_t);
68 static void	 handle_siginfo(int, short, void*);
69 
70 static imsg_handlerfn *handlers[] = {
71 	[IMSG_QUIT] = handle_imsg_quit,
72 	[IMSG_CGI_RES] = handle_imsg_cgi_res,
73 };
74 
75 static inline int
76 matches(const char *pattern, const char *path)
77 {
78 	if (*path == '/')
79 		path++;
80 	return !fnmatch(pattern, path, 0);
81 }
82 
83 static inline void
84 reschedule_read(int fd, struct client *c, statefn fn)
85 {
86 	event_once(fd, EV_READ, fn, c, NULL);
87 }
88 
89 static inline void
90 reschedule_write(int fd, struct client *c, statefn fn)
91 {
92 	event_once(fd, EV_WRITE, fn, c, NULL);
93 }
94 
95 const char *
96 vhost_lang(struct vhost *v, const char *path)
97 {
98 	struct location *loc;
99 
100 	if (v == NULL || path == NULL)
101 		return NULL;
102 
103 	loc = TAILQ_FIRST(&v->locations);
104 	while ((loc = TAILQ_NEXT(loc, locations)) != NULL) {
105 		if (loc->lang != NULL) {
106 			if (matches(loc->match, path))
107 				return loc->lang;
108 		}
109 	}
110 
111 	return TAILQ_FIRST(&v->locations)->lang;
112 }
113 
114 const char *
115 vhost_default_mime(struct vhost *v, const char *path)
116 {
117 	struct location *loc;
118 	const char *default_mime = "application/octet-stream";
119 
120 	if (v == NULL || path == NULL)
121 		return default_mime;
122 
123 	loc = TAILQ_FIRST(&v->locations);
124 	while ((loc = TAILQ_NEXT(loc, locations)) != NULL) {
125 		if (loc->default_mime != NULL) {
126 			if (matches(loc->match, path))
127 				return loc->default_mime;
128 		}
129 	}
130 
131 	loc = TAILQ_FIRST(&v->locations);
132 	if (loc->default_mime != NULL)
133 		return loc->default_mime;
134 	return default_mime;
135 }
136 
137 const char *
138 vhost_index(struct vhost *v, const char *path)
139 {
140 	struct location *loc;
141 	const char *index = "index.gmi";
142 
143 	if (v == NULL || path == NULL)
144 		return index;
145 
146 	loc = TAILQ_FIRST(&v->locations);
147 	while ((loc = TAILQ_NEXT(loc, locations)) != NULL) {
148 		if (loc->index != NULL) {
149 			if (matches(loc->match, path))
150 				return loc->index;
151 		}
152 	}
153 
154 	loc = TAILQ_FIRST(&v->locations);
155 	if (loc->index != NULL)
156 		return loc->index;
157 	return index;
158 }
159 
160 int
161 vhost_auto_index(struct vhost *v, const char *path)
162 {
163 	struct location *loc;
164 
165 	if (v == NULL || path == NULL)
166 		return 0;
167 
168 	loc = TAILQ_FIRST(&v->locations);
169 	while ((loc = TAILQ_NEXT(loc, locations)) != NULL) {
170 		if (loc->auto_index != 0) {
171 			if (matches(loc->match, path))
172 				return loc->auto_index == 1;
173 		}
174 	}
175 
176 	loc = TAILQ_FIRST(&v->locations);
177 	return loc->auto_index == 1;
178 }
179 
180 int
181 vhost_block_return(struct vhost *v, const char *path, int *code, const char **fmt)
182 {
183 	struct location *loc;
184 
185 	if (v == NULL || path == NULL)
186 		return 0;
187 
188 	loc = TAILQ_FIRST(&v->locations);
189 	while ((loc = TAILQ_NEXT(loc, locations)) != NULL) {
190 		if (loc->block_code != 0) {
191 			if (matches(loc->match, path)) {
192 				*code = loc->block_code;
193 				*fmt = loc->block_fmt;
194 				return 1;
195 			}
196 		}
197 	}
198 
199 	loc = TAILQ_FIRST(&v->locations);
200 	*code = loc->block_code;
201 	*fmt = loc->block_fmt;
202 	return loc->block_code != 0;
203 }
204 
205 int
206 vhost_strip(struct vhost *v, const char *path)
207 {
208 	struct location *loc;
209 
210 	if (v == NULL || path == NULL)
211 		return 0;
212 
213 	loc = TAILQ_FIRST(&v->locations);
214 	while ((loc = TAILQ_NEXT(loc, locations)) != NULL) {
215 		if (loc->strip != 0) {
216 			if (matches(loc->match, path))
217 				return loc->strip;
218 		}
219 	}
220 
221 	loc = TAILQ_FIRST(&v->locations);
222 	return loc->strip;
223 }
224 
225 X509_STORE *
226 vhost_require_ca(struct vhost *v, const char *path)
227 {
228 	struct location *loc;
229 
230 	if (v == NULL || path == NULL)
231 		return NULL;
232 
233 	loc = TAILQ_FIRST(&v->locations);
234 	while ((loc = TAILQ_NEXT(loc, locations)) != NULL) {
235 		if (loc->reqca != NULL) {
236 			if (matches(loc->match, path))
237 				return loc->reqca;
238 		}
239 	}
240 
241 	loc = TAILQ_FIRST(&v->locations);
242 	return loc->reqca;
243 }
244 
245 int
246 vhost_disable_log(struct vhost *v, const char *path)
247 {
248 	struct location *loc;
249 
250 	if (v == NULL || path == NULL)
251 		return 0;
252 
253 	loc = TAILQ_FIRST(&v->locations);
254 	while ((loc = TAILQ_NEXT(loc, locations)) != NULL) {
255 		if (loc->disable_log && matches(loc->match, path))
256 				return 1;
257 	}
258 
259 	loc = TAILQ_FIRST(&v->locations);
260 	return loc->disable_log;
261 }
262 
263 static int
264 check_path(struct client *c, const char *path, int *fd)
265 {
266 	struct stat sb;
267 	const char *p;
268 	int flags;
269 
270 	assert(path != NULL);
271 
272 	if (*path == '\0')
273 		p = ".";
274 	else if (*path == '/')
275 		/* in send_dir we add an initial / (to be
276 		 * redirect-friendly), but here we want to skip it */
277 		p = path+1;
278 	else
279 		p = path;
280 
281 	flags = O_RDONLY | O_NOFOLLOW;
282 
283 	if (*fd == -1 && (*fd = openat(c->host->dirfd, p, flags)) == -1)
284 		return FILE_MISSING;
285 
286 	if (fstat(*fd, &sb) == -1) {
287 		log_notice(c, "failed stat for %s: %s", path, strerror(errno));
288 		return FILE_MISSING;
289 	}
290 
291 	if (S_ISDIR(sb.st_mode))
292 		return FILE_DIRECTORY;
293 
294 	if (sb.st_mode & S_IXUSR)
295 		return FILE_EXECUTABLE;
296 
297 	return FILE_EXISTS;
298 }
299 
300 static void
301 open_file(struct client *c)
302 {
303 	switch (check_path(c, c->iri.path, &c->pfd)) {
304 	case FILE_EXECUTABLE:
305 		if (c->host->cgi != NULL && matches(c->host->cgi, c->iri.path)) {
306 			start_cgi(c->iri.path, "", c);
307 			return;
308 		}
309 
310 		/* fallthrough */
311 
312 	case FILE_EXISTS:
313 		c->next = handle_copy;
314 		start_reply(c, SUCCESS, mime(c->host, c->iri.path));
315 		return;
316 
317 	case FILE_DIRECTORY:
318 		open_dir(c);
319 		return;
320 
321 	case FILE_MISSING:
322 		if (c->host->cgi != NULL && matches(c->host->cgi, c->iri.path)) {
323 			check_for_cgi(c);
324 			return;
325 		}
326 		start_reply(c, NOT_FOUND, "not found");
327 		return;
328 
329 	default:
330 		/* unreachable */
331 		abort();
332 	}
333 }
334 
335 /*
336  * the inverse of this algorithm, i.e. starting from the start of the
337  * path + strlen(cgi), and checking if each component, should be
338  * faster.  But it's tedious to write.  This does the opposite: starts
339  * from the end and strip one component at a time, until either an
340  * executable is found or we emptied the path.
341  */
342 static void
343 check_for_cgi(struct client *c)
344 {
345 	char path[PATH_MAX];
346 	char *end;
347 
348 	strlcpy(path, c->iri.path, sizeof(path));
349 	end = strchr(path, '\0');
350 
351 	while (end > path) {
352 		/* go up one level.  UNIX paths are simple and POSIX
353 		 * dirname, with its ambiguities on if the given path
354 		 * is changed or not, gives me headaches. */
355 		while (*end != '/')
356 			end--;
357 		*end = '\0';
358 
359 		switch (check_path(c, path, &c->pfd)) {
360 		case FILE_EXECUTABLE:
361 			start_cgi(path, end+1, c);
362 			return;
363 		case FILE_MISSING:
364 			break;
365 		default:
366 			goto err;
367 		}
368 
369 		*end = '/';
370 		end--;
371 	}
372 
373 err:
374 	start_reply(c, NOT_FOUND, "not found");
375 	return;
376 }
377 
378 void
379 mark_nonblock(int fd)
380 {
381 	int flags;
382 
383 	if ((flags = fcntl(fd, F_GETFL)) == -1)
384 		fatal("fcntl(F_GETFL): %s", strerror(errno));
385 	if (fcntl(fd, F_SETFL, flags | O_NONBLOCK) == -1)
386 		fatal("fcntl(F_SETFL): %s", strerror(errno));
387 }
388 
389 static void
390 handle_handshake(int fd, short ev, void *d)
391 {
392 	struct client *c = d;
393 	struct vhost *h;
394 	const char *servname;
395 	const char *parse_err = "unknown error";
396 
397 	switch (tls_handshake(c->ctx)) {
398 	case 0:  /* success */
399 	case -1: /* already handshaked */
400 		break;
401 	case TLS_WANT_POLLIN:
402 		reschedule_read(fd, c, &handle_handshake);
403 		return;
404 	case TLS_WANT_POLLOUT:
405 		reschedule_write(fd, c, &handle_handshake);
406 		return;
407 	default:
408 		/* unreachable */
409 		abort();
410 	}
411 
412 	servname = tls_conn_servername(c->ctx);
413 	if (!puny_decode(servname, c->domain, sizeof(c->domain), &parse_err)) {
414 		log_info(c, "puny_decode: %s", parse_err);
415 		goto err;
416 	}
417 
418 	TAILQ_FOREACH(h, &hosts, vhosts) {
419 		if (matches(h->domain, c->domain))
420 			break;
421 	}
422 
423 	log_debug(c, "handshake: SNI: \"%s\"; decoded: \"%s\"; matched: \"%s\"",
424 	    servname != NULL ? servname : "(null)",
425 	    c->domain,
426 	    h != NULL ? h->domain : "(null)");
427 
428 	if (h != NULL) {
429 		c->host = h;
430 		handle_open_conn(fd, ev, c);
431 		return;
432 	}
433 
434 err:
435 	if (servname != NULL)
436 		strncpy(c->req, servname, sizeof(c->req));
437 	else
438 		strncpy(c->req, "null", sizeof(c->req));
439 
440 	start_reply(c, BAD_REQUEST, "Wrong/malformed host or missing SNI");
441 }
442 
443 static char *
444 strip_path(char *path, int strip)
445 {
446 	char *t;
447 
448 	while (strip > 0) {
449 		if ((t = strchr(path, '/')) == NULL) {
450 			path = strchr(path, '\0');
451 			break;
452 		}
453 		path = t;
454 		strip--;
455 	}
456 
457 	return path;
458 }
459 
460 static void
461 fmt_sbuf(const char *fmt, struct client *c, const char *path)
462 {
463 	size_t i;
464         char buf[32];
465 
466 	memset(buf, 0, sizeof(buf));
467 	for (i = 0; *fmt; ++fmt) {
468 		if (i == sizeof(buf)-1 || *fmt == '%') {
469 			strlcat(c->sbuf, buf, sizeof(c->sbuf));
470 			memset(buf, 0, sizeof(buf));
471 			i = 0;
472 		}
473 
474 		if (*fmt != '%') {
475 			buf[i++] = *fmt;
476 			continue;
477 		}
478 
479 		switch (*++fmt) {
480 		case '%':
481 			strlcat(c->sbuf, "%", sizeof(c->sbuf));
482 			break;
483 		case 'p':
484 			strlcat(c->sbuf, path, sizeof(c->sbuf));
485 			break;
486 		case 'q':
487 			strlcat(c->sbuf, c->iri.query, sizeof(c->sbuf));
488 			break;
489 		case 'P':
490 			snprintf(buf, sizeof(buf), "%d", conf.port);
491 			strlcat(c->sbuf, buf, sizeof(c->sbuf));
492 			memset(buf, 0, sizeof(buf));
493 			break;
494 		case 'N':
495 			strlcat(c->sbuf, c->domain, sizeof(c->sbuf));
496 			break;
497 		default:
498 			fatal("%s: unknown fmt specifier %c",
499 			    __func__, *fmt);
500 		}
501 	}
502 
503 	if (i != 0)
504 		strlcat(c->sbuf, buf, sizeof(c->sbuf));
505 }
506 
507 /* 1 if a matching `block return' (and apply it), 0 otherwise */
508 static int
509 apply_block_return(struct client *c)
510 {
511 	const char *fmt, *path;
512 	int code;
513 
514 	if (!vhost_block_return(c->host, c->iri.path, &code, &fmt))
515 		return 0;
516 
517 	path = strip_path(c->iri.path, vhost_strip(c->host, c->iri.path));
518 	fmt_sbuf(fmt, c, path);
519 
520 	start_reply(c, code, c->sbuf);
521 	return 1;
522 }
523 
524 /* 1 if matching `require client ca' fails (and apply it), 0 otherwise */
525 static int
526 apply_require_ca(struct client *c)
527 {
528 	X509_STORE	*store;
529 	const uint8_t	*cert;
530 	size_t		 len;
531 
532 	if ((store = vhost_require_ca(c->host, c->iri.path)) == NULL)
533 		return 0;
534 
535 	if (!tls_peer_cert_provided(c->ctx)) {
536 		start_reply(c, CLIENT_CERT_REQ, "client certificate required");
537 		return 1;
538 	}
539 
540 	cert = tls_peer_cert_chain_pem(c->ctx, &len);
541 	if (!validate_against_ca(store, cert, len)) {
542 		start_reply(c, CERT_NOT_AUTH, "certificate not authorised");
543 		return 1;
544 	}
545 
546 	return 0;
547 }
548 
549 static void
550 handle_open_conn(int fd, short ev, void *d)
551 {
552 	struct client *c = d;
553 	const char *parse_err = "invalid request";
554 	char decoded[DOMAIN_NAME_LEN];
555 
556 	bzero(c->req, sizeof(c->req));
557 	bzero(&c->iri, sizeof(c->iri));
558 
559 	switch (tls_read(c->ctx, c->req, sizeof(c->req)-1)) {
560 	case -1:
561 		log_err(c, "tls_read: %s", tls_error(c->ctx));
562 		close_conn(fd, ev, c);
563 		return;
564 
565 	case TLS_WANT_POLLIN:
566 		reschedule_read(fd, c, &handle_open_conn);
567 		return;
568 
569 	case TLS_WANT_POLLOUT:
570 		reschedule_write(fd, c, &handle_open_conn);
571 		return;
572 	}
573 
574 	if (!trim_req_iri(c->req, &parse_err)
575 	    || !parse_iri(c->req, &c->iri, &parse_err)
576 	    || !puny_decode(c->iri.host, decoded, sizeof(decoded), &parse_err)) {
577 		log_info(c, "iri parse error: %s", parse_err);
578 		start_reply(c, BAD_REQUEST, "invalid request");
579 		return;
580 	}
581 
582 	if (c->iri.port_no != conf.port
583 	    || strcmp(c->iri.schema, "gemini")
584 	    || strcmp(decoded, c->domain)) {
585 		start_reply(c, PROXY_REFUSED, "won't proxy request");
586 		return;
587 	}
588 
589 	if (apply_require_ca(c))
590 		return;
591 
592 	if (apply_block_return(c))
593 		return;
594 
595 	if (c->host->entrypoint != NULL) {
596 		start_cgi(c->host->entrypoint, c->iri.path, c);
597 		return;
598 	}
599 
600 	open_file(c);
601 }
602 
603 static void
604 start_reply(struct client *c, int code, const char *meta)
605 {
606 	c->code = code;
607 	c->meta = meta;
608 	handle_start_reply(c->fd, 0, c);
609 }
610 
611 static void
612 handle_start_reply(int fd, short ev, void *d)
613 {
614 	struct client *c = d;
615 	char buf[1030];		/* status + ' ' + max reply len + \r\n\0 */
616 	const char *lang;
617 	size_t len;
618 
619 	lang = vhost_lang(c->host, c->iri.path);
620 
621 	snprintf(buf, sizeof(buf), "%d ", c->code);
622 	strlcat(buf, c->meta, sizeof(buf));
623 	if (!strcmp(c->meta, "text/gemini") && lang != NULL) {
624 		strlcat(buf, "; lang=", sizeof(buf));
625 		strlcat(buf, lang, sizeof(buf));
626 	}
627 
628 	len = strlcat(buf, "\r\n", sizeof(buf));
629 	assert(len < sizeof(buf));
630 
631 	switch (tls_write(c->ctx, buf, len)) {
632 	case -1:
633 		close_conn(fd, ev, c);
634 		return;
635 	case TLS_WANT_POLLIN:
636 		reschedule_read(fd, c, &handle_start_reply);
637 		return;
638 	case TLS_WANT_POLLOUT:
639 		reschedule_write(fd, c, &handle_start_reply);
640 		return;
641 	}
642 
643 	if (!vhost_disable_log(c->host, c->iri.path))
644 		log_request(c, buf, sizeof(buf));
645 
646 	if (c->code != SUCCESS)
647 		close_conn(fd, ev, c);
648 	else
649 		c->next(fd, ev, c);
650 }
651 
652 static size_t
653 host_nth(struct vhost *h)
654 {
655 	struct vhost	*v;
656 	size_t		 i = 0;
657 
658 	TAILQ_FOREACH(v, &hosts, vhosts) {
659 		if (v == h)
660 			return i;
661 		i++;
662 	}
663 
664 	abort();
665 }
666 
667 static void
668 start_cgi(const char *spath, const char *relpath, struct client *c)
669 {
670 	char addr[NI_MAXHOST];
671 	const char *t;
672 	struct cgireq req;
673 	int e;
674 
675 	e = getnameinfo((struct sockaddr*)&c->addr, sizeof(c->addr),
676 	    addr, sizeof(addr),
677 	    NULL, 0,
678 	    NI_NUMERICHOST);
679 	if (e != 0)
680 		fatal("getnameinfo failed");
681 
682 	memset(&req, 0, sizeof(req));
683 
684 	memcpy(req.buf, c->req, sizeof(req.buf));
685 
686 	req.iri_schema_off = c->iri.schema - c->req;
687 	req.iri_host_off = c->iri.host - c->req;
688 	req.iri_port_off = c->iri.port - c->req;
689 	req.iri_path_off = c->iri.path - c->req;
690 	req.iri_query_off = c->iri.query - c->req;
691 	req.iri_fragment_off = c->iri.fragment - c->req;
692 
693 	req.iri_portno = c->iri.port_no;
694 
695 	strlcpy(req.spath, spath, sizeof(req.spath));
696 	strlcpy(req.relpath, relpath, sizeof(req.relpath));
697 	strlcpy(req.addr, addr, sizeof(req.addr));
698 
699 	if ((t = tls_peer_cert_subject(c->ctx)) != NULL)
700 		strlcpy(req.subject, t, sizeof(req.subject));
701 	if ((t = tls_peer_cert_issuer(c->ctx)) != NULL)
702 		strlcpy(req.issuer, t, sizeof(req.issuer));
703 	if ((t = tls_peer_cert_hash(c->ctx)) != NULL)
704 		strlcpy(req.hash, t, sizeof(req.hash));
705 
706 	req.notbefore = tls_peer_cert_notbefore(c->ctx);
707 	req.notafter = tls_peer_cert_notafter(c->ctx);
708 
709 	req.host_off = host_nth(c->host);
710 
711 	imsg_compose(&exibuf, IMSG_CGI_REQ, c->id, 0, -1, &req, sizeof(req));
712 	imsg_flush(&exibuf);
713 
714 	close(c->pfd);
715 }
716 
717 static void
718 open_dir(struct client *c)
719 {
720 	size_t len;
721 	int dirfd;
722 	char *before_file;
723 
724 	len = strlen(c->iri.path);
725 	if (len > 0 && !ends_with(c->iri.path, "/")) {
726 		redirect_canonical_dir(c);
727 		return;
728 	}
729 
730 	strlcpy(c->sbuf, "/", sizeof(c->sbuf));
731 	strlcat(c->sbuf, c->iri.path, sizeof(c->sbuf));
732 	if (!ends_with(c->sbuf, "/"))
733 		strlcat(c->sbuf, "/", sizeof(c->sbuf));
734 	before_file = strchr(c->sbuf, '\0');
735 	len = strlcat(c->sbuf, vhost_index(c->host, c->iri.path),
736 	    sizeof(c->sbuf));
737 	if (len >= sizeof(c->sbuf)) {
738 		start_reply(c, TEMP_FAILURE, "internal server error");
739 		return;
740 	}
741 
742 	c->iri.path = c->sbuf;
743 
744 	/* close later unless we have to generate the dir listing */
745 	dirfd = c->pfd;
746 	c->pfd = -1;
747 
748 	switch (check_path(c, c->iri.path, &c->pfd)) {
749 	case FILE_EXECUTABLE:
750 		if (c->host->cgi != NULL && matches(c->host->cgi, c->iri.path)) {
751 			start_cgi(c->iri.path, "", c);
752 			break;
753 		}
754 
755 		/* fallthrough */
756 
757 	case FILE_EXISTS:
758 		c->next = handle_copy;
759 		start_reply(c, SUCCESS, mime(c->host, c->iri.path));
760 		break;
761 
762 	case FILE_DIRECTORY:
763 		start_reply(c, TEMP_REDIRECT, c->sbuf);
764 		break;
765 
766 	case FILE_MISSING:
767 		*before_file = '\0';
768 
769 		if (!vhost_auto_index(c->host, c->iri.path)) {
770 			start_reply(c, NOT_FOUND, "not found");
771 			break;
772 		}
773 
774 		c->pfd = dirfd;
775 		c->next = enter_handle_dirlist;
776 
777 		if ((c->dir = fdopendir(c->pfd)) == NULL) {
778 			log_err(c, "fdopendir(%d) (vhost:%s) %s: %s",
779 			    c->pfd, c->host->domain, c->iri.path, strerror(errno));
780 			start_reply(c, TEMP_FAILURE, "internal server error");
781 			return;
782 		}
783 		c->off = 0;
784 
785                 start_reply(c, SUCCESS, "text/gemini");
786 		return;
787 
788 	default:
789 		/* unreachable */
790 		abort();
791 	}
792 
793 	close(dirfd);
794 }
795 
796 static void
797 redirect_canonical_dir(struct client *c)
798 {
799 	size_t len;
800 
801 	strlcpy(c->sbuf, "/", sizeof(c->sbuf));
802 	strlcat(c->sbuf, c->iri.path, sizeof(c->sbuf));
803 	len = strlcat(c->sbuf, "/", sizeof(c->sbuf));
804 
805 	if (len >= sizeof(c->sbuf)) {
806 		start_reply(c, TEMP_FAILURE, "internal server error");
807 		return;
808 	}
809 
810 	start_reply(c, TEMP_REDIRECT, c->sbuf);
811 }
812 
813 static void
814 enter_handle_dirlist(int fd, short ev, void *d)
815 {
816 	struct client *c = d;
817 	char b[PATH_MAX];
818 	size_t l;
819 
820 	strlcpy(b, c->iri.path, sizeof(b));
821 	l = snprintf(c->sbuf, sizeof(c->sbuf),
822 	    "# Index of %s\n\n", b);
823 	if (l >= sizeof(c->sbuf)) {
824 		/* this is impossible, given that we have enough space
825 		 * in c->sbuf to hold the ancilliary string plus the
826 		 * full path; but it wouldn't read nice without some
827 		 * error checking, and I'd like to avoid a strlen. */
828 		close_conn(fd, ev, c);
829 		return;
830 	}
831 
832 	c->len = l;
833 	handle_dirlist(fd, ev, c);
834 }
835 
836 static void
837 handle_dirlist(int fd, short ev, void *d)
838 {
839 	struct client *c = d;
840 	ssize_t r;
841 
842 	while (c->len > 0) {
843 		switch (r = tls_write(c->ctx, c->sbuf + c->off, c->len)) {
844 		case -1:
845 			close_conn(fd, ev, c);
846 			return;
847 		case TLS_WANT_POLLOUT:
848 			reschedule_read(fd, c, &handle_dirlist);
849 			return;
850 		case TLS_WANT_POLLIN:
851 			reschedule_write(fd, c, &handle_dirlist);
852 			return;
853 		default:
854 			c->off += r;
855 			c->len -= r;
856 		}
857 	}
858 
859 	send_directory_listing(fd, ev, c);
860 }
861 
862 static int
863 read_next_dir_entry(struct client *c)
864 {
865 	struct dirent *d;
866 
867 	do {
868 		errno = 0;
869 		if ((d = readdir(c->dir)) == NULL) {
870 			if (errno != 0)
871 				log_err(c, "readdir: %s", strerror(errno));
872 			return 0;
873 		}
874 	} while (!strcmp(d->d_name, "."));
875 
876 	/* XXX: url escape */
877 	snprintf(c->sbuf, sizeof(c->sbuf), "=> %s %s\n",
878 	    d->d_name, d->d_name);
879 	c->len = strlen(c->sbuf);
880 	c->off = 0;
881 
882 	return 1;
883 }
884 
885 static void
886 send_directory_listing(int fd, short ev, void *d)
887 {
888 	struct client *c = d;
889 	ssize_t r;
890 
891 	while (1) {
892 		if (c->len == 0) {
893 			if (!read_next_dir_entry(c))
894 				goto end;
895 		}
896 
897 		while (c->len > 0) {
898 			switch (r = tls_write(c->ctx, c->sbuf + c->off, c->len)) {
899 			case -1:
900 				goto end;
901 
902 			case TLS_WANT_POLLOUT:
903 				reschedule_read(fd, c, &send_directory_listing);
904 				return;
905 
906 			case TLS_WANT_POLLIN:
907 				reschedule_write(fd, c, &send_directory_listing);
908 				return;
909 
910 			default:
911 				c->off += r;
912 				c->len -= r;
913 				break;
914 			}
915 		}
916 	}
917 
918 end:
919 	close_conn(fd, ev, d);
920 }
921 
922 /* accumulate the meta line from the cgi script. */
923 static void
924 handle_cgi_reply(int fd, short ev, void *d)
925 {
926 	struct client *c = d;
927 	void	*buf, *e;
928 	size_t	 len;
929 	ssize_t	 r;
930 
931 
932 	buf = c->sbuf + c->len;
933 	len = sizeof(c->sbuf) - c->len;
934 
935 	r = read(c->pfd, buf, len);
936 	if (r == 0 || r == -1) {
937 		start_reply(c, CGI_ERROR, "CGI error");
938 		return;
939 	}
940 
941 	c->len += r;
942 
943 	/* TODO: error if the CGI script don't reply correctly */
944 	e = strchr(c->sbuf, '\n');
945 	if (e != NULL || c->len == sizeof(c->sbuf)) {
946 		log_request(c, c->sbuf, c->len);
947 
948 		c->off = 0;
949 		handle_copy(fd, ev, c);
950 		return;
951 	}
952 
953 	reschedule_read(fd, c, &handle_cgi_reply);
954 }
955 
956 static void
957 handle_copy(int fd, short ev, void *d)
958 {
959 	struct client *c = d;
960 	ssize_t r;
961 
962 	while (1) {
963 		while (c->len > 0) {
964 			switch (r = tls_write(c->ctx, c->sbuf + c->off, c->len)) {
965 			case -1:
966 				goto end;
967 
968 			case TLS_WANT_POLLOUT:
969 				reschedule_write(c->fd, c, &handle_copy);
970 				return;
971 
972 			case TLS_WANT_POLLIN:
973 				reschedule_read(c->fd, c, &handle_copy);
974 				return;
975 
976 			default:
977                                 c->off += r;
978 				c->len -= r;
979 				break;
980 			}
981 		}
982 
983 		switch (r = read(c->pfd, c->sbuf, sizeof(c->sbuf))) {
984 		case 0:
985 			goto end;
986 		case -1:
987 			if (errno == EAGAIN || errno == EWOULDBLOCK) {
988 				reschedule_read(c->pfd, c, &handle_copy);
989 				return;
990 			}
991 			goto end;
992 		default:
993 			c->len = r;
994 			c->off = 0;
995 		}
996 	}
997 
998 end:
999 	close_conn(c->fd, ev, d);
1000 }
1001 
1002 static void
1003 close_conn(int fd, short ev, void *d)
1004 {
1005 	struct client *c = d;
1006 
1007 	switch (tls_close(c->ctx)) {
1008 	case TLS_WANT_POLLIN:
1009 		reschedule_read(fd, c, &close_conn);
1010 		return;
1011 	case TLS_WANT_POLLOUT:
1012 		reschedule_read(fd, c, &close_conn);
1013 		return;
1014 	}
1015 
1016 	connected_clients--;
1017 
1018 	tls_free(c->ctx);
1019 	c->ctx = NULL;
1020 
1021 	if (c->pfd != -1)
1022 		close(c->pfd);
1023 
1024 	if (c->dir != NULL)
1025 		closedir(c->dir);
1026 
1027 	close(c->fd);
1028 	c->fd = -1;
1029 }
1030 
1031 static void
1032 do_accept(int sock, short et, void *d)
1033 {
1034 	struct client *c;
1035 	struct sockaddr_storage addr;
1036 	struct sockaddr *saddr;
1037 	socklen_t len;
1038 	int i, fd;
1039 
1040 	(void)et;
1041 
1042 	saddr = (struct sockaddr*)&addr;
1043 	len = sizeof(addr);
1044 	if ((fd = accept(sock, saddr, &len)) == -1) {
1045 		if (errno == EWOULDBLOCK || errno == EAGAIN)
1046 			return;
1047 		fatal("accept: %s", strerror(errno));
1048 	}
1049 
1050 	mark_nonblock(fd);
1051 
1052 	for (i = 0; i < MAX_USERS; ++i) {
1053 		c = &clients[i];
1054 		if (c->fd == -1) {
1055 			memset(c, 0, sizeof(*c));
1056 			c->id = i;
1057 			if (tls_accept_socket(ctx, &c->ctx, fd) == -1)
1058 				break; /* goodbye fd! */
1059 
1060 			c->fd = fd;
1061 			c->pfd = -1;
1062 			c->dir = NULL;
1063 			c->addr = addr;
1064 
1065 			reschedule_read(fd, c, &handle_handshake);
1066 			connected_clients++;
1067 			return;
1068 		}
1069 	}
1070 
1071 	close(fd);
1072 }
1073 
1074 struct client *
1075 client_by_id(int id)
1076 {
1077 	if ((size_t)id > sizeof(clients)/sizeof(clients[0]))
1078 		fatal("in client_by_id: invalid id %d", id);
1079 	return &clients[id];
1080 }
1081 
1082 static void
1083 handle_imsg_cgi_res(struct imsgbuf *ibuf, struct imsg *imsg, size_t len)
1084 {
1085 	struct client *c;
1086 
1087 	c = client_by_id(imsg->hdr.peerid);
1088 
1089 	if ((c->pfd = imsg->fd) == -1)
1090 		start_reply(c, TEMP_FAILURE, "internal server error");
1091 	else
1092 		reschedule_read(c->pfd, c, &handle_cgi_reply);
1093 }
1094 
1095 static void
1096 handle_imsg_quit(struct imsgbuf *ibuf, struct imsg *imsg, size_t len)
1097 {
1098 	(void)imsg;
1099 	(void)len;
1100 
1101 	/* don't call event_loopbreak since we want to finish to
1102 	 * handle the ongoing connections. */
1103 
1104 	event_del(&e4);
1105 	if (has_ipv6)
1106 		event_del(&e6);
1107 	if (has_siginfo)
1108 		signal_del(&siginfo);
1109 	event_del(&imsgev);
1110 	signal_del(&sigusr2);
1111 }
1112 
1113 static void
1114 handle_dispatch_imsg(int fd, short ev, void *d)
1115 {
1116 	struct imsgbuf *ibuf = d;
1117 	dispatch_imsg(ibuf, handlers, sizeof(handlers));
1118 }
1119 
1120 static void
1121 handle_siginfo(int fd, short ev, void *d)
1122 {
1123 	(void)fd;
1124 	(void)ev;
1125 	(void)d;
1126 
1127 	log_info(NULL, "%d connected clients", connected_clients);
1128 }
1129 
1130 void
1131 loop(struct tls *ctx_, int sock4, int sock6, struct imsgbuf *ibuf)
1132 {
1133 	size_t i;
1134 
1135 	ctx = ctx_;
1136 
1137 	event_init();
1138 
1139 	memset(&clients, 0, sizeof(clients));
1140 	for (i = 0; i < MAX_USERS; ++i)
1141 		clients[i].fd = -1;
1142 
1143 	event_set(&e4, sock4, EV_READ | EV_PERSIST, &do_accept, NULL);
1144 	event_add(&e4, NULL);
1145 
1146 	if (sock6 != -1) {
1147 		has_ipv6 = 1;
1148 		event_set(&e6, sock6, EV_READ | EV_PERSIST, &do_accept, NULL);
1149 		event_add(&e6, NULL);
1150 	}
1151 
1152 	event_set(&imsgev, ibuf->fd, EV_READ | EV_PERSIST, handle_dispatch_imsg, ibuf);
1153 	event_add(&imsgev, NULL);
1154 
1155 #ifdef SIGINFO
1156 	has_siginfo = 1;
1157 	signal_set(&siginfo, SIGINFO, &handle_siginfo, NULL);
1158 	signal_add(&siginfo, NULL);
1159 #endif
1160 	signal_set(&sigusr2, SIGUSR2, &handle_siginfo, NULL);
1161 	signal_add(&sigusr2, NULL);
1162 
1163 	sandbox_server_process();
1164 	event_dispatch();
1165 	_exit(0);
1166 }