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 <event.h>
25 #include <fcntl.h>
26 #include <fnmatch.h>
27 #include <limits.h>
28 #include <string.h>
29 
30 #include "gmid.h"
31 
32 struct server {
33 	struct client	 clients[MAX_USERS];
34 	struct tls	*ctx;
35 };
36 
37 struct event e4, e6, sighup, siginfo, sigusr2;
38 int has_ipv6, has_siginfo;
39 
40 int connected_clients;
41 
42 static inline int matches(const char*, const char*);
43 
44 static inline void reschedule_read(int, struct client*, statefn);
45 static inline void reschedule_write(int, struct client*, statefn);
46 
47 static int	 check_path(struct client*, const char*, int*);
48 static void	 open_file(struct client*);
49 static void	 load_file(struct client*);
50 static void	 check_for_cgi(struct client*);
51 static void	 handle_handshake(int, short, void*);
52 static char	*strip_path(char*, int);
53 static void	 fmt_sbuf(const char*, struct client*, const char*);
54 static int	 apply_block_return(struct client*);
55 static int	 apply_require_ca(struct client*);
56 static void	 handle_open_conn(int, short, void*);
57 static void	 start_reply(struct client*, int, const char*);
58 static void	 handle_start_reply(int, short, void*);
59 static void	 start_cgi(const char*, const char*, struct client*);
60 static void	 send_file(int, short, void*);
61 static void	 open_dir(struct client*);
62 static void	 redirect_canonical_dir(struct client*);
63 static void	 enter_handle_dirlist(int, short, void*);
64 static void	 handle_dirlist(int, short, void*);
65 static int 	 read_next_dir_entry(struct client*);
66 static void	 send_directory_listing(int, short, void*);
67 static void	 handle_cgi_reply(int, short, void*);
68 static void	 handle_cgi(int, short, void*);
69 static void	 close_conn(int, short, void*);
70 static void	 do_accept(int, short, void*);
71 static void	 handle_sighup(int, short, void*);
72 
73 static inline int
74 matches(const char *pattern, const char *path)
75 {
76 	if (*path == '/')
77 		path++;
78 	return !fnmatch(pattern, path, 0);
79 }
80 
81 static inline void
82 reschedule_read(int fd, struct client *c, statefn fn)
83 {
84 	event_once(fd, EV_READ, fn, c, NULL);
85 }
86 
87 void
88 reschedule_write(int fd, struct client *c, statefn fn)
89 {
90 	event_once(fd, EV_WRITE, fn, c, NULL);
91 }
92 
93 const char *
94 vhost_lang(struct vhost *v, const char *path)
95 {
96 	struct location *loc;
97 
98 	if (v == NULL || path == NULL)
99 		return NULL;
100 
101 	for (loc = &v->locations[1]; loc->match != NULL; ++loc) {
102 		if (loc->lang != NULL) {
103 			if (matches(loc->match, path))
104 				return loc->lang;
105 		}
106 	}
107 
108 	return v->locations[0].lang;
109 }
110 
111 const char *
112 vhost_default_mime(struct vhost *v, const char *path)
113 {
114 	struct location *loc;
115 	const char *default_mime = "application/octet-stream";
116 
117 	if (v == NULL || path == NULL)
118 		return default_mime;
119 
120 	for (loc = &v->locations[1]; loc->match != NULL; ++loc) {
121 		if (loc->default_mime != NULL) {
122 			if (matches(loc->match, path))
123 				return loc->default_mime;
124 		}
125 	}
126 
127 	if (v->locations[0].default_mime != NULL)
128 		return v->locations[0].default_mime;
129 	return default_mime;
130 }
131 
132 const char *
133 vhost_index(struct vhost *v, const char *path)
134 {
135 	struct location *loc;
136 	const char *index = "index.gmi";
137 
138 	if (v == NULL || path == NULL)
139 		return index;
140 
141 	for (loc = &v->locations[1]; loc->match != NULL; ++loc) {
142 		if (loc->index != NULL) {
143 			if (matches(loc->match, path))
144 				return loc->index;
145 		}
146 	}
147 
148 	if (v->locations[0].index != NULL)
149 		return v->locations[0].index;
150 	return index;
151 }
152 
153 int
154 vhost_auto_index(struct vhost *v, const char *path)
155 {
156 	struct location *loc;
157 
158 	if (v == NULL || path == NULL)
159 		return 0;
160 
161 	for (loc = &v->locations[1]; loc->match != NULL; ++loc) {
162 		if (loc->auto_index != 0) {
163 			if (matches(loc->match, path))
164 				return loc->auto_index == 1;
165 		}
166 	}
167 
168 	return v->locations[0].auto_index == 1;
169 }
170 
171 int
172 vhost_block_return(struct vhost *v, const char *path, int *code, const char **fmt)
173 {
174 	struct location *loc;
175 
176 	if (v == NULL || path == NULL)
177 		return 0;
178 
179 	for (loc = &v->locations[1]; loc->match != NULL; ++loc) {
180 		if (loc->block_code != 0) {
181 			if (matches(loc->match, path)) {
182 				*code = loc->block_code;
183 				*fmt = loc->block_fmt;
184 				return 1;
185 			}
186 		}
187 	}
188 
189 	*code = v->locations[0].block_code;
190 	*fmt = v->locations[0].block_fmt;
191 	return v->locations[0].block_code != 0;
192 }
193 
194 int
195 vhost_strip(struct vhost *v, const char *path)
196 {
197 	struct location *loc;
198 
199 	if (v == NULL || path == NULL)
200 		return 0;
201 
202 	for (loc = &v->locations[1]; loc->match != NULL; ++loc) {
203 		if (loc->strip != 0) {
204 			if (matches(loc->match, path))
205 				return loc->strip;
206 		}
207 	}
208 
209 	return v->locations[0].strip;
210 }
211 
212 X509_STORE *
213 vhost_require_ca(struct vhost *v, const char *path)
214 {
215 	struct location *loc;
216 
217 	if (v == NULL || path == NULL)
218 		return NULL;
219 
220 	for (loc = &v->locations[1]; loc->match != NULL; ++loc) {
221 		if (loc->reqca != NULL) {
222 			if (matches(loc->match, path))
223 				return loc->reqca;
224 		}
225 	}
226 
227 	return v->locations[0].reqca;
228 }
229 
230 static int
231 check_path(struct client *c, const char *path, int *fd)
232 {
233 	struct stat sb;
234 	const char *p;
235 	int flags;
236 
237 	assert(path != NULL);
238 
239 	if (*path == '\0')
240 		p = ".";
241 	else if (*path == '/')
242 		/* in send_dir we add an initial / (to be
243 		 * redirect-friendly), but here we want to skip it */
244 		p = path+1;
245 	else
246 		p = path;
247 
248 	flags = O_RDONLY | O_NOFOLLOW;
249 
250 	if (*fd == -1 && (*fd = openat(c->host->dirfd, p, flags)) == -1)
251 		return FILE_MISSING;
252 
253 	if (fstat(*fd, &sb) == -1) {
254 		log_notice(c, "failed stat for %s: %s", path, strerror(errno));
255 		return FILE_MISSING;
256 	}
257 
258 	if (S_ISDIR(sb.st_mode))
259 		return FILE_DIRECTORY;
260 
261 	if (sb.st_mode & S_IXUSR)
262 		return FILE_EXECUTABLE;
263 
264 	return FILE_EXISTS;
265 }
266 
267 static void
268 open_file(struct client *c)
269 {
270 	switch (check_path(c, c->iri.path, &c->pfd)) {
271 	case FILE_EXECUTABLE:
272 		if (c->host->cgi != NULL && !fnmatch(c->host->cgi, c->iri.path, 0)) {
273 			start_cgi(c->iri.path, "", c);
274 			return;
275 		}
276 
277 		/* fallthrough */
278 
279 	case FILE_EXISTS:
280 		load_file(c);
281 		return;
282 
283 	case FILE_DIRECTORY:
284 		open_dir(c);
285 		return;
286 
287 	case FILE_MISSING:
288 		if (c->host->cgi != NULL && !fnmatch(c->host->cgi, c->iri.path, 0)) {
289 			check_for_cgi(c);
290 			return;
291 		}
292 		start_reply(c, NOT_FOUND, "not found");
293 		return;
294 
295 	default:
296 		/* unreachable */
297 		abort();
298 	}
299 }
300 
301 static void
302 load_file(struct client *c)
303 {
304 	if ((c->len = filesize(c->pfd)) == -1) {
305 		log_err(c, "failed to get file size for %s: %s",
306 		    c->iri.path, strerror(errno));
307 		start_reply(c, TEMP_FAILURE, "internal server error");
308 		return;
309 	}
310 
311 	if ((c->buf = mmap(NULL, c->len, PROT_READ, MAP_PRIVATE,
312 		    c->pfd, 0)) == MAP_FAILED) {
313 		log_err(c, "mmap: %s: %s", c->iri.path, strerror(errno));
314 		start_reply(c, TEMP_FAILURE, "internal server error");
315 		return;
316 	}
317 	c->i = c->buf;
318 	c->next = send_file;
319 	start_reply(c, SUCCESS, mime(c->host, c->iri.path));
320 }
321 
322 /*
323  * the inverse of this algorithm, i.e. starting from the start of the
324  * path + strlen(cgi), and checking if each component, should be
325  * faster.  But it's tedious to write.  This does the opposite: starts
326  * from the end and strip one component at a time, until either an
327  * executable is found or we emptied the path.
328  */
329 static void
330 check_for_cgi(struct client *c)
331 {
332 	char path[PATH_MAX];
333 	char *end;
334 
335 	strlcpy(path, c->iri.path, sizeof(path));
336 	end = strchr(path, '\0');
337 
338 	while (end > path) {
339 		/* go up one level.  UNIX paths are simple and POSIX
340 		 * dirname, with its ambiguities on if the given path
341 		 * is changed or not, gives me headaches. */
342 		while (*end != '/')
343 			end--;
344 		*end = '\0';
345 
346 		switch (check_path(c, path, &c->pfd)) {
347 		case FILE_EXECUTABLE:
348 			start_cgi(path, end+1, c);
349 			return;
350 		case FILE_MISSING:
351 			break;
352 		default:
353 			goto err;
354 		}
355 
356 		*end = '/';
357 		end--;
358 	}
359 
360 err:
361 	start_reply(c, NOT_FOUND, "not found");
362 	return;
363 }
364 
365 void
366 mark_nonblock(int fd)
367 {
368 	int flags;
369 
370 	if ((flags = fcntl(fd, F_GETFL)) == -1)
371 		fatal("fcntl(F_GETFL): %s", strerror(errno));
372 	if (fcntl(fd, F_SETFL, flags | O_NONBLOCK) == -1)
373 		fatal("fcntl(F_SETFL): %s", strerror(errno));
374 }
375 
376 static void
377 handle_handshake(int fd, short ev, void *d)
378 {
379 	struct client *c = d;
380 	struct vhost *h;
381 	const char *servname;
382 	const char *parse_err = "unknown error";
383 
384 	switch (tls_handshake(c->ctx)) {
385 	case 0:  /* success */
386 	case -1: /* already handshaked */
387 		break;
388 	case TLS_WANT_POLLIN:
389 		reschedule_read(fd, c, &handle_handshake);
390 		return;
391 	case TLS_WANT_POLLOUT:
392 		reschedule_write(fd, c, &handle_handshake);
393 		return;
394 	default:
395 		/* unreachable */
396 		abort();
397 	}
398 
399 	servname = tls_conn_servername(c->ctx);
400 	if (!puny_decode(servname, c->domain, sizeof(c->domain), &parse_err)) {
401 		log_info(c, "puny_decode: %s", parse_err);
402 		goto err;
403 	}
404 
405 	for (h = hosts; h->domain != NULL; ++h) {
406 		if (!fnmatch(h->domain, c->domain, 0))
407 			break;
408 	}
409 
410 	log_debug(c, "handshake: SNI: \"%s\"; decoded: \"%s\"; matched: \"%s\"",
411 	    servname != NULL ? servname : "(null)",
412 	    c->domain,
413 	    h->domain != NULL ? h->domain : "(null)");
414 
415 	if (h->domain != NULL) {
416 		c->host = h;
417 		handle_open_conn(fd, ev, c);
418 		return;
419 	}
420 
421 err:
422 	if (servname != NULL)
423 		strncpy(c->req, servname, sizeof(c->req));
424 	else
425 		strncpy(c->req, "null", sizeof(c->req));
426 
427 	start_reply(c, BAD_REQUEST, "Wrong/malformed host or missing SNI");
428 }
429 
430 static char *
431 strip_path(char *path, int strip)
432 {
433 	char *t;
434 
435 	while (strip > 0) {
436 		if ((t = strchr(path, '/')) == NULL) {
437 			path = strchr(path, '\0');
438 			break;
439 		}
440 		path = t;
441 		strip--;
442 	}
443 
444 	return path;
445 }
446 
447 static void
448 fmt_sbuf(const char *fmt, struct client *c, const char *path)
449 {
450 	size_t i;
451         char buf[32];
452 
453 	memset(buf, 0, sizeof(buf));
454 	for (i = 0; *fmt; ++fmt) {
455 		if (i == sizeof(buf)-1 || *fmt == '%') {
456 			strlcat(c->sbuf, buf, sizeof(c->sbuf));
457 			memset(buf, 0, sizeof(buf));
458 			i = 0;
459 		}
460 
461 		if (*fmt != '%') {
462 			buf[i++] = *fmt;
463 			continue;
464 		}
465 
466 		switch (*++fmt) {
467 		case '%':
468 			strlcat(c->sbuf, "%", sizeof(c->sbuf));
469 			break;
470 		case 'p':
471 			strlcat(c->sbuf, path, sizeof(c->sbuf));
472 			break;
473 		case 'q':
474 			strlcat(c->sbuf, c->iri.query, sizeof(c->sbuf));
475 			break;
476 		case 'P':
477 			snprintf(buf, sizeof(buf), "%d", conf.port);
478 			strlcat(c->sbuf, buf, sizeof(c->sbuf));
479 			memset(buf, 0, sizeof(buf));
480 			break;
481 		case 'N':
482 			strlcat(c->sbuf, c->domain, sizeof(c->sbuf));
483 			break;
484 		default:
485 			fatal("%s: unknown fmt specifier %c",
486 			    __func__, *fmt);
487 		}
488 	}
489 
490 	if (i != 0)
491 		strlcat(c->sbuf, buf, sizeof(c->sbuf));
492 }
493 
494 /* 1 if a matching `block return' (and apply it), 0 otherwise */
495 static int
496 apply_block_return(struct client *c)
497 {
498 	const char *fmt, *path;
499 	int code;
500 
501 	if (!vhost_block_return(c->host, c->iri.path, &code, &fmt))
502 		return 0;
503 
504 	path = strip_path(c->iri.path, vhost_strip(c->host, c->iri.path));
505 	fmt_sbuf(fmt, c, path);
506 
507 	start_reply(c, code, c->sbuf);
508 	return 1;
509 }
510 
511 /* 1 if matching `require client ca' fails (and apply it), 0 otherwise */
512 static int
513 apply_require_ca(struct client *c)
514 {
515 	X509_STORE	*store;
516 	const uint8_t	*cert;
517 	size_t		 len;
518 
519 	if ((store = vhost_require_ca(c->host, c->iri.path)) == NULL)
520 		return 0;
521 
522 	if (!tls_peer_cert_provided(c->ctx)) {
523 		start_reply(c, CLIENT_CERT_REQ, "client certificate required");
524 		return 1;
525 	}
526 
527 	cert = tls_peer_cert_chain_pem(c->ctx, &len);
528 	if (!validate_against_ca(store, cert, len)) {
529 		start_reply(c, CERT_NOT_AUTH, "certificate not authorised");
530 		return 1;
531 	}
532 
533 	return 0;
534 }
535 
536 static void
537 handle_open_conn(int fd, short ev, void *d)
538 {
539 	struct client *c = d;
540 	const char *parse_err = "invalid request";
541 	char decoded[DOMAIN_NAME_LEN];
542 
543 	bzero(c->req, sizeof(c->req));
544 	bzero(&c->iri, sizeof(c->iri));
545 
546 	switch (tls_read(c->ctx, c->req, sizeof(c->req)-1)) {
547 	case -1:
548 		log_err(c, "tls_read: %s", tls_error(c->ctx));
549 		close_conn(fd, ev, c);
550 		return;
551 
552 	case TLS_WANT_POLLIN:
553 		reschedule_read(fd, c, &handle_open_conn);
554 		return;
555 
556 	case TLS_WANT_POLLOUT:
557 		reschedule_write(fd, c, &handle_open_conn);
558 		return;
559 	}
560 
561 	if (!trim_req_iri(c->req, &parse_err)
562 	    || !parse_iri(c->req, &c->iri, &parse_err)
563 	    || !puny_decode(c->iri.host, decoded, sizeof(decoded), &parse_err)) {
564 		log_info(c, "iri parse error: %s", parse_err);
565 		start_reply(c, BAD_REQUEST, "invalid request");
566 		return;
567 	}
568 
569 	if (c->iri.port_no != conf.port
570 	    || strcmp(c->iri.schema, "gemini")
571 	    || strcmp(decoded, c->domain)) {
572 		start_reply(c, PROXY_REFUSED, "won't proxy request");
573 		return;
574 	}
575 
576 	if (apply_require_ca(c))
577 		return;
578 
579 	if (apply_block_return(c))
580 		return;
581 
582 	if (c->host->entrypoint != NULL) {
583 		start_cgi(c->host->entrypoint, c->iri.path, c);
584 		return;
585 	}
586 
587 	open_file(c);
588 }
589 
590 static void
591 start_reply(struct client *c, int code, const char *meta)
592 {
593 	c->code = code;
594 	c->meta = meta;
595 	handle_start_reply(c->fd, 0, c);
596 }
597 
598 static void
599 handle_start_reply(int fd, short ev, void *d)
600 {
601 	struct client *c = d;
602 	char buf[1030];		/* status + ' ' + max reply len + \r\n\0 */
603 	const char *lang;
604 	size_t len;
605 
606 	lang = vhost_lang(c->host, c->iri.path);
607 
608 	snprintf(buf, sizeof(buf), "%d ", c->code);
609 	strlcat(buf, c->meta, sizeof(buf));
610 	if (!strcmp(c->meta, "text/gemini") && lang != NULL) {
611 		strlcat(buf, "; lang=", sizeof(buf));
612 		strlcat(buf, lang, sizeof(buf));
613 	}
614 
615 	len = strlcat(buf, "\r\n", sizeof(buf));
616 	assert(len < sizeof(buf));
617 
618 	switch (tls_write(c->ctx, buf, len)) {
619 	case -1:
620 		close_conn(fd, ev, c);
621 		return;
622 	case TLS_WANT_POLLIN:
623 		reschedule_read(fd, c, &handle_start_reply);
624 		return;
625 	case TLS_WANT_POLLOUT:
626 		reschedule_write(fd, c, &handle_start_reply);
627 		return;
628 	}
629 
630 	log_request(c, buf, sizeof(buf));
631 
632 	if (c->code != SUCCESS)
633 		close_conn(fd, ev, c);
634 	else
635 		c->next(fd, ev, c);
636 }
637 
638 static void
639 start_cgi(const char *spath, const char *relpath, struct client *c)
640 {
641 	char addr[NI_MAXHOST];
642 	int e;
643 
644 	e = getnameinfo((struct sockaddr*)&c->addr, sizeof(c->addr),
645 	    addr, sizeof(addr),
646 	    NULL, 0,
647 	    NI_NUMERICHOST);
648 	if (e != 0)
649 		goto err;
650 
651 	if (!send_iri(exfd, &c->iri)
652 	    || !send_string(exfd, spath)
653 	    || !send_string(exfd, relpath)
654 	    || !send_string(exfd, addr)
655 	    || !send_string(exfd, tls_peer_cert_subject(c->ctx))
656 	    || !send_string(exfd, tls_peer_cert_issuer(c->ctx))
657 	    || !send_string(exfd, tls_peer_cert_hash(c->ctx))
658 	    || !send_time(exfd, tls_peer_cert_notbefore(c->ctx))
659 	    || !send_time(exfd, tls_peer_cert_notafter(c->ctx))
660 	    || !send_vhost(exfd, c->host))
661 		goto err;
662 
663 	close(c->pfd);
664 	if ((c->pfd = recv_fd(exfd)) == -1) {
665 		start_reply(c, TEMP_FAILURE, "internal server error");
666 		return;
667 	}
668 
669 	reschedule_read(c->pfd, c, &handle_cgi_reply);
670 	return;
671 
672 err:
673 	/* fatal("cannot talk to the executor process: %s", strerror(errno)); */
674 	fatal("cannot talk to the executor process");
675 }
676 
677 static void
678 send_file(int fd, short ev, void *d)
679 {
680 	struct client *c = d;
681 	ssize_t ret, len;
682 
683 	len = (c->buf + c->len) - c->i;
684 
685 	while (len > 0) {
686 		switch (ret = tls_write(c->ctx, c->i, len)) {
687 		case -1:
688 			log_err(c, "tls_write: %s", tls_error(c->ctx));
689 			close_conn(fd, ev, c);
690 			return;
691 
692 		case TLS_WANT_POLLIN:
693 			reschedule_read(fd, c, &send_file);
694 			return;
695 
696 		case TLS_WANT_POLLOUT:
697 			reschedule_write(fd, c, &send_file);
698 			return;
699 
700 		default:
701 			c->i += ret;
702 			len -= ret;
703 			break;
704 		}
705 	}
706 
707 	close_conn(fd, ev, c);
708 }
709 
710 static void
711 open_dir(struct client *c)
712 {
713 	size_t len;
714 	int dirfd;
715 	char *before_file;
716 
717 	len = strlen(c->iri.path);
718 	if (len > 0 && !ends_with(c->iri.path, "/")) {
719 		redirect_canonical_dir(c);
720 		return;
721 	}
722 
723 	strlcpy(c->sbuf, "/", sizeof(c->sbuf));
724 	strlcat(c->sbuf, c->iri.path, sizeof(c->sbuf));
725 	if (!ends_with(c->sbuf, "/"))
726 		strlcat(c->sbuf, "/", sizeof(c->sbuf));
727 	before_file = strchr(c->sbuf, '\0');
728 	len = strlcat(c->sbuf, vhost_index(c->host, c->iri.path),
729 	    sizeof(c->sbuf));
730 	if (len >= sizeof(c->sbuf)) {
731 		start_reply(c, TEMP_FAILURE, "internal server error");
732 		return;
733 	}
734 
735 	c->iri.path = c->sbuf;
736 
737 	/* close later unless we have to generate the dir listing */
738 	dirfd = c->pfd;
739 	c->pfd = -1;
740 
741 	switch (check_path(c, c->iri.path, &c->pfd)) {
742 	case FILE_EXECUTABLE:
743 		if (c->host->cgi != NULL && !fnmatch(c->host->cgi, c->iri.path, 0)) {
744 			start_cgi(c->iri.path, "", c);
745 			break;
746 		}
747 
748 		/* fallthrough */
749 
750 	case FILE_EXISTS:
751                 load_file(c);
752 		break;
753 
754 	case FILE_DIRECTORY:
755 		start_reply(c, TEMP_REDIRECT, c->sbuf);
756 		break;
757 
758 	case FILE_MISSING:
759 		*before_file = '\0';
760 
761 		if (!vhost_auto_index(c->host, c->iri.path)) {
762 			start_reply(c, NOT_FOUND, "not found");
763 			break;
764 		}
765 
766 		c->pfd = dirfd;
767 		c->next = enter_handle_dirlist;
768 
769 		if ((c->dir = fdopendir(c->pfd)) == NULL) {
770 			log_err(c, "fdopendir(%d) (vhost:%s) %s: %s",
771 			    c->pfd, c->host->domain, c->iri.path, strerror(errno));
772 			start_reply(c, TEMP_FAILURE, "internal server error");
773 			return;
774 		}
775 		c->off = 0;
776 
777                 start_reply(c, SUCCESS, "text/gemini");
778 		return;
779 
780 	default:
781 		/* unreachable */
782 		abort();
783 	}
784 
785 	close(dirfd);
786 }
787 
788 static void
789 redirect_canonical_dir(struct client *c)
790 {
791 	size_t len;
792 
793 	strlcpy(c->sbuf, "/", sizeof(c->sbuf));
794 	strlcat(c->sbuf, c->iri.path, sizeof(c->sbuf));
795 	len = strlcat(c->sbuf, "/", sizeof(c->sbuf));
796 
797 	if (len >= sizeof(c->sbuf)) {
798 		start_reply(c, TEMP_FAILURE, "internal server error");
799 		return;
800 	}
801 
802 	start_reply(c, TEMP_REDIRECT, c->sbuf);
803 }
804 
805 static void
806 enter_handle_dirlist(int fd, short ev, void *d)
807 {
808 	struct client *c = d;
809 	char b[PATH_MAX];
810 	size_t l;
811 
812 	strlcpy(b, c->iri.path, sizeof(b));
813 	l = snprintf(c->sbuf, sizeof(c->sbuf),
814 	    "# Index of %s\n\n", b);
815 	if (l >= sizeof(c->sbuf)) {
816 		/* this is impossible, given that we have enough space
817 		 * in c->sbuf to hold the ancilliary string plus the
818 		 * full path; but it wouldn't read nice without some
819 		 * error checking, and I'd like to avoid a strlen. */
820 		close_conn(fd, ev, c);
821 		return;
822 	}
823 
824 	c->len = l;
825 	handle_dirlist(fd, ev, c);
826 }
827 
828 static void
829 handle_dirlist(int fd, short ev, void *d)
830 {
831 	struct client *c = d;
832 	ssize_t r;
833 
834 	while (c->len > 0) {
835 		switch (r = tls_write(c->ctx, c->sbuf + c->off, c->len)) {
836 		case -1:
837 			close_conn(fd, ev, c);
838 			return;
839 		case TLS_WANT_POLLOUT:
840 			reschedule_read(fd, c, &handle_dirlist);
841 			return;
842 		case TLS_WANT_POLLIN:
843 			reschedule_write(fd, c, &handle_dirlist);
844 			return;
845 		default:
846 			c->off += r;
847 			c->len -= r;
848 		}
849 	}
850 
851 	send_directory_listing(fd, ev, c);
852 }
853 
854 static int
855 read_next_dir_entry(struct client *c)
856 {
857 	struct dirent *d;
858 
859 	do {
860 		errno = 0;
861 		if ((d = readdir(c->dir)) == NULL) {
862 			if (errno != 0)
863 				log_err(c, "readdir: %s", strerror(errno));
864 			return 0;
865 		}
866 	} while (!strcmp(d->d_name, "."));
867 
868 	/* XXX: url escape */
869 	snprintf(c->sbuf, sizeof(c->sbuf), "=> %s %s\n",
870 	    d->d_name, d->d_name);
871 	c->len = strlen(c->sbuf);
872 	c->off = 0;
873 
874 	return 1;
875 }
876 
877 static void
878 send_directory_listing(int fd, short ev, void *d)
879 {
880 	struct client *c = d;
881 	ssize_t r;
882 
883 	while (1) {
884 		if (c->len == 0) {
885 			if (!read_next_dir_entry(c))
886 				goto end;
887 		}
888 
889 		while (c->len > 0) {
890 			switch (r = tls_write(c->ctx, c->sbuf + c->off, c->len)) {
891 			case -1:
892 				goto end;
893 
894 			case TLS_WANT_POLLOUT:
895 				reschedule_read(fd, c, &send_directory_listing);
896 				return;
897 
898 			case TLS_WANT_POLLIN:
899 				reschedule_write(fd, c, &send_directory_listing);
900 				return;
901 
902 			default:
903 				c->off += r;
904 				c->len -= r;
905 				break;
906 			}
907 		}
908 	}
909 
910 end:
911 	close_conn(fd, ev, d);
912 }
913 
914 /* accumulate the meta line from the cgi script. */
915 static void
916 handle_cgi_reply(int fd, short ev, void *d)
917 {
918 	struct client *c = d;
919 	void	*buf, *e;
920 	size_t	 len;
921 	ssize_t	 r;
922 
923 
924 	buf = c->sbuf + c->len;
925 	len = sizeof(c->sbuf) - c->len;
926 
927 	r = read(c->pfd, buf, len);
928 	if (r == 0 || r == -1) {
929 		start_reply(c, CGI_ERROR, "CGI error");
930 		return;
931 	}
932 
933 	c->len += r;
934 
935 	/* TODO: error if the CGI script don't reply correctly */
936 	e = strchr(c->sbuf, '\n');
937 	if (e != NULL || c->len == sizeof(c->sbuf)) {
938 		log_request(c, c->sbuf, c->len);
939 
940 		c->off = 0;
941 		handle_cgi(fd, ev, c);
942 		return;
943 	}
944 
945 	reschedule_read(fd, c, &handle_cgi_reply);
946 }
947 
948 static void
949 handle_cgi(int fd, short ev, void *d)
950 {
951 	struct client *c = d;
952 	ssize_t r;
953 
954 	while (1) {
955 		if (c->len == 0) {
956 			switch (r = read(c->pfd, c->sbuf, sizeof(c->sbuf))) {
957 			case 0:
958 				goto end;
959 			case -1:
960 				if (errno == EAGAIN || errno == EWOULDBLOCK) {
961 					reschedule_read(c->pfd, c, &handle_cgi);
962 					return;
963 				}
964 				goto end;
965 			default:
966 				c->len = r;
967 				c->off = 0;
968 			}
969 		}
970 
971 		while (c->len > 0) {
972 			switch (r = tls_write(c->ctx, c->sbuf + c->off, c->len)) {
973 			case -1:
974 				goto end;
975 
976 			case TLS_WANT_POLLOUT:
977 				reschedule_read(c->fd, c, &handle_cgi);
978 				return;
979 
980 			case TLS_WANT_POLLIN:
981 				reschedule_write(c->fd, c, &handle_cgi);
982 				return;
983 
984 			default:
985                                 c->off += r;
986 				c->len -= r;
987 				break;
988 			}
989 		}
990 	}
991 
992 end:
993 	close_conn(c->fd, ev, d);
994 }
995 
996 static void
997 close_conn(int fd, short ev, void *d)
998 {
999 	struct client *c = d;
1000 
1001 	switch (tls_close(c->ctx)) {
1002 	case TLS_WANT_POLLIN:
1003 		reschedule_read(fd, c, &close_conn);
1004 		return;
1005 	case TLS_WANT_POLLOUT:
1006 		reschedule_read(fd, c, &close_conn);
1007 		return;
1008 	}
1009 
1010 	connected_clients--;
1011 
1012 	tls_free(c->ctx);
1013 	c->ctx = NULL;
1014 
1015 	if (c->buf != MAP_FAILED)
1016 		munmap(c->buf, c->len);
1017 
1018 	if (c->pfd != -1)
1019 		close(c->pfd);
1020 
1021 	if (c->dir != NULL)
1022 		closedir(c->dir);
1023 
1024 	close(c->fd);
1025 	c->fd = -1;
1026 }
1027 
1028 static void
1029 do_accept(int sock, short et, void *d)
1030 {
1031 	struct client *c;
1032 	struct server *s = d;
1033 	struct sockaddr_storage addr;
1034 	struct sockaddr *saddr;
1035 	socklen_t len;
1036 	int i, fd;
1037 
1038 	(void)et;
1039 
1040 
1041 	saddr = (struct sockaddr*)&addr;
1042 	len = sizeof(addr);
1043 	if ((fd = accept4(sock, saddr, &len, SOCK_NONBLOCK)) == -1) {
1044 		if (errno == EWOULDBLOCK || errno == EAGAIN)
1045 			return;
1046 		fatal("accept: %s", strerror(errno));
1047 	}
1048 
1049 	for (i = 0; i < MAX_USERS; ++i) {
1050 		c = &s->clients[i];
1051 		if (c->fd == -1) {
1052 			memset(c, 0, sizeof(*c));
1053 			if (tls_accept_socket(s->ctx, &c->ctx, fd) == -1)
1054 				break; /* goodbye fd! */
1055 
1056 			c->fd = fd;
1057 			c->pfd = -1;
1058 			c->buf = MAP_FAILED;
1059 			c->dir = NULL;
1060 			c->addr = addr;
1061 
1062 			reschedule_read(fd, c, &handle_handshake);
1063 			connected_clients++;
1064 			return;
1065 		}
1066 	}
1067 
1068 	close(fd);
1069 }
1070 
1071 static void
1072 handle_sighup(int fd, short ev, void *d)
1073 {
1074 	(void)fd;
1075 	(void)ev;
1076 
1077 	event_del(&e4);
1078 	if (has_ipv6)
1079 		event_del(&e6);
1080 	if (has_siginfo)
1081 		signal_del(&siginfo);
1082 	signal_del(&sigusr2);
1083 	signal_del(&sighup);
1084 }
1085 
1086 static void
1087 handle_siginfo(int fd, short ev, void *d)
1088 {
1089 	(void)fd;
1090 	(void)ev;
1091 	(void)d;
1092 
1093 	log_info(NULL, "%d connected clients", connected_clients);
1094 }
1095 
1096 void
1097 loop(struct tls *ctx, int sock4, int sock6)
1098 {
1099 	struct server server;
1100 	size_t i;
1101 
1102 	event_init();
1103 
1104 	memset(&server, 0, sizeof(server));
1105 	for (i = 0; i < MAX_USERS; ++i)
1106 		server.clients[i].fd = -1;
1107 
1108 	event_set(&e4, sock4, EV_READ | EV_PERSIST, &do_accept, &server);
1109 	event_add(&e4, NULL);
1110 
1111 	if (sock6 != -1) {
1112 		has_ipv6 = 1;
1113 		event_set(&e6, sock6, EV_READ | EV_PERSIST, &do_accept, &server);
1114 		event_add(&e6, NULL);
1115 	}
1116 
1117 	signal_set(&sighup, SIGHUP, &handle_sighup, NULL);
1118 	signal_add(&sighup, NULL);
1119 
1120 #ifdef SIGINFO
1121 	has_siginfo = 1;
1122 	signal_set(&siginfo, SIGINFO, &handle_siginfo, NULL);
1123 	signal_add(&siginfo, NULL);
1124 #endif
1125 	signal_set(&sigusr2, SIGINFO, &handle_siginfo, NULL);
1126 	signal_add(&sigusr2, NULL);
1127 
1128 	server.ctx = ctx;
1129 
1130 	sandbox();
1131 	event_dispatch();
1132 	_exit(0);
1133 }