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