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Date:: Sun Feb 7 21:47:01 2021 UTC
Message:: define TLS_CLIENT_NOT_BEFORE/NOT_AFTER in CGI scripts
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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 <limits.h>
27 #include <string.h>
28 
29 #include "gmid.h"
30 
31 int connected_clients;
32 
33 static int	 check_path(struct client*, const char*, int*);
34 static void	 open_file(struct pollfd*, struct client*);
35 static void	 load_file(struct pollfd*, struct client*);
36 static void	 check_for_cgi(struct pollfd*, struct client*);
37 static void	 handle_handshake(struct pollfd*, struct client*);
38 static int	 apply_block_return(struct pollfd*, struct client*);
39 static void	 handle_open_conn(struct pollfd*, struct client*);
40 static void	 start_reply(struct pollfd*, struct client*, int, const char*);
41 static void	 handle_start_reply(struct pollfd*, struct client*);
42 static void	 start_cgi(const char*, const char*, struct pollfd*, struct client*);
43 static void	 send_file(struct pollfd*, struct client*);
44 static void	 open_dir(struct pollfd*, struct client*);
45 static void	 redirect_canonical_dir(struct pollfd*, struct client*);
46 static void	 enter_handle_dirlist(struct pollfd*, struct client*);
47 static void	 handle_dirlist(struct pollfd*, struct client*);
48 static int 	 read_next_dir_entry(struct client*);
49 static void	 send_directory_listing(struct pollfd*, struct client*);
50 static void	 cgi_poll_on_child(struct pollfd*, struct client*);
51 static void	 cgi_poll_on_client(struct pollfd*, struct client*);
52 static void	 handle_cgi_reply(struct pollfd*, struct client*);
53 static void	 handle_cgi(struct pollfd*, struct client*);
54 static void	 close_conn(struct pollfd*, struct client*);
55 static void	 do_accept(int, struct tls*, struct pollfd*, struct client*);
56 
57 const char *
58 vhost_lang(struct vhost *v, const char *path)
59 {
60 	struct location *loc;
61 
62 	if (v == NULL || path == NULL)
63 		return NULL;
64 
65 	for (loc = &v->locations[1]; loc->match != NULL; ++loc) {
66 		if (loc->lang != NULL) {
67 			if (!fnmatch(loc->match, path, 0))
68 				return loc->lang;
69 		}
70 	}
71 
72 	return v->locations[0].lang;
73 }
74 
75 const char *
76 vhost_default_mime(struct vhost *v, const char *path)
77 {
78 	struct location *loc;
79 	const char *default_mime = "application/octet-stream";
80 
81 	if (v == NULL || path == NULL)
82 		return default_mime;
83 
84 	for (loc = &v->locations[1]; loc->match != NULL; ++loc) {
85 		if (loc->default_mime != NULL) {
86 			if (!fnmatch(loc->match, path, 0))
87 				return loc->default_mime;
88 		}
89 	}
90 
91 	if (v->locations[0].default_mime != NULL)
92 		return v->locations[0].default_mime;
93 	return default_mime;
94 }
95 
96 const char *
97 vhost_index(struct vhost *v, const char *path)
98 {
99 	struct location *loc;
100 	const char *index = "index.gmi";
101 
102 	if (v == NULL || path == NULL)
103 		return index;
104 
105 	for (loc = &v->locations[1]; loc->match != NULL; ++loc) {
106 		if (loc->index != NULL) {
107 			if (!fnmatch(loc->match, path, 0))
108 				return loc->index;
109 		}
110 	}
111 
112 	if (v->locations[0].index != NULL)
113 		return v->locations[0].index;
114 	return index;
115 }
116 
117 int
118 vhost_auto_index(struct vhost *v, const char *path)
119 {
120 	struct location *loc;
121 
122 	if (v == NULL || path == NULL)
123 		return 0;
124 
125 	for (loc = &v->locations[1]; loc->match != NULL; ++loc) {
126 		if (loc->auto_index != 0) {
127 			if (!fnmatch(loc->match, path, 0))
128 				return loc->auto_index == 1;
129 		}
130 	}
131 
132 	return v->locations[0].auto_index == 1;
133 }
134 
135 int
136 vhost_block_return(struct vhost *v, const char *path, int *code, const char **fmt)
137 {
138 	struct location *loc;
139 
140 	if (v == NULL || path == NULL)
141 		return 0;
142 
143 	for (loc = &v->locations[1]; loc->match != NULL; ++loc) {
144 		if (loc->block_code != 0) {
145 			if (!fnmatch(loc->match, path, 0)) {
146 				*code = loc->block_code;
147 				*fmt = loc->block_fmt;
148 				return 1;
149 			}
150 		}
151 	}
152 
153 	*code = v->locations[0].block_code;
154 	*fmt = v->locations[0].block_fmt;
155 	return v->locations[0].block_code != 0;
156 }
157 
158 int
159 vhost_strip(struct vhost *v, const char *path)
160 {
161 	struct location *loc;
162 
163 	if (v == NULL || path == NULL)
164 		return 0;
165 
166 	for (loc = &v->locations[1]; loc->match != NULL; ++loc) {
167 		if (loc->strip != 0) {
168 			if (!fnmatch(loc->match, path, 0))
169 				return loc->strip;
170 		}
171 	}
172 
173 	return v->locations[0].strip;
174 }
175 
176 static int
177 check_path(struct client *c, const char *path, int *fd)
178 {
179 	struct stat sb;
180 	const char *p;
181 	int flags;
182 
183 	assert(path != NULL);
184 
185 	if (*path == '\0')
186 		p = ".";
187 	else if (*path == '/')
188 		/* in send_dir we add an initial / (to be
189 		 * redirect-friendly), but here we want to skip it */
190 		p = path+1;
191 	else
192 		p = path;
193 
194 	flags = O_RDONLY | O_NOFOLLOW;
195 
196 	if (*fd == -1 && (*fd = openat(c->host->dirfd, p, flags)) == -1)
197 		return FILE_MISSING;
198 
199 	if (fstat(*fd, &sb) == -1) {
200 		log_notice(c, "failed stat for %s: %s", path, strerror(errno));
201 		return FILE_MISSING;
202 	}
203 
204 	if (S_ISDIR(sb.st_mode))
205 		return FILE_DIRECTORY;
206 
207 	if (sb.st_mode & S_IXUSR)
208 		return FILE_EXECUTABLE;
209 
210 	return FILE_EXISTS;
211 }
212 
213 static void
214 open_file(struct pollfd *fds, struct client *c)
215 {
216 	switch (check_path(c, c->iri.path, &c->fd)) {
217 	case FILE_EXECUTABLE:
218 		if (c->host->cgi != NULL && !fnmatch(c->host->cgi, c->iri.path, 0)) {
219 			start_cgi(c->iri.path, "", fds, c);
220 			return;
221 		}
222 
223 		/* fallthrough */
224 
225 	case FILE_EXISTS:
226 		load_file(fds, c);
227 		return;
228 
229 	case FILE_DIRECTORY:
230 		open_dir(fds, c);
231 		return;
232 
233 	case FILE_MISSING:
234 		if (c->host->cgi != NULL && !fnmatch(c->host->cgi, c->iri.path, 0)) {
235 			check_for_cgi(fds, c);
236 			return;
237 		}
238 		start_reply(fds, c, NOT_FOUND, "not found");
239 		return;
240 
241 	default:
242 		/* unreachable */
243 		abort();
244 	}
245 }
246 
247 static void
248 load_file(struct pollfd *fds, struct client *c)
249 {
250 	if ((c->len = filesize(c->fd)) == -1) {
251 		log_err(c, "failed to get file size for %s: %s",
252 		    c->iri.path, strerror(errno));
253 		start_reply(fds, c, TEMP_FAILURE, "internal server error");
254 		return;
255 	}
256 
257 	if ((c->buf = mmap(NULL, c->len, PROT_READ, MAP_PRIVATE,
258 		    c->fd, 0)) == MAP_FAILED) {
259 		log_err(c, "mmap: %s: %s", c->iri.path, strerror(errno));
260 		start_reply(fds, c, TEMP_FAILURE, "internal server error");
261 		return;
262 	}
263 	c->i = c->buf;
264 	c->next = send_file;
265 	start_reply(fds, c, SUCCESS, mime(c->host, c->iri.path));
266 }
267 
268 /*
269  * the inverse of this algorithm, i.e. starting from the start of the
270  * path + strlen(cgi), and checking if each component, should be
271  * faster.  But it's tedious to write.  This does the opposite: starts
272  * from the end and strip one component at a time, until either an
273  * executable is found or we emptied the path.
274  */
275 static void
276 check_for_cgi(struct pollfd *fds, struct client *c)
277 {
278 	char path[PATH_MAX];
279 	char *end;
280 
281 	strlcpy(path, c->iri.path, sizeof(path));
282 	end = strchr(path, '\0');
283 
284 	/* NB: assume CGI is enabled and path matches cgi */
285 
286 	while (end > path) {
287 		/* go up one level.  UNIX paths are simple and POSIX
288 		 * dirname, with its ambiguities on if the given path
289 		 * is changed or not, gives me headaches. */
290 		while (*end != '/')
291 			end--;
292 		*end = '\0';
293 
294 		switch (check_path(c, path, &c->fd)) {
295 		case FILE_EXECUTABLE:
296 			start_cgi(path, end+1, fds, c);
297 			return;
298 		case FILE_MISSING:
299 			break;
300 		default:
301 			goto err;
302 		}
303 
304 		*end = '/';
305 		end--;
306 	}
307 
308 err:
309 	start_reply(fds, c, NOT_FOUND, "not found");
310 	return;
311 }
312 
313 void
314 mark_nonblock(int fd)
315 {
316 	int flags;
317 
318 	if ((flags = fcntl(fd, F_GETFL)) == -1)
319 		fatal("fcntl(F_GETFL): %s", strerror(errno));
320 	if (fcntl(fd, F_SETFL, flags | O_NONBLOCK) == -1)
321 		fatal("fcntl(F_SETFL): %s", strerror(errno));
322 }
323 
324 static void
325 handle_handshake(struct pollfd *fds, struct client *c)
326 {
327 	struct vhost *h;
328 	const char *servname;
329 	const char *parse_err = "unknown error";
330 
331 	switch (tls_handshake(c->ctx)) {
332 	case 0:  /* success */
333 	case -1: /* already handshaked */
334 		break;
335 	case TLS_WANT_POLLIN:
336 		fds->events = POLLIN;
337 		return;
338 	case TLS_WANT_POLLOUT:
339 		fds->events = POLLOUT;
340 		return;
341 	default:
342 		/* unreachable */
343 		abort();
344 	}
345 
346 	servname = tls_conn_servername(c->ctx);
347 	if (!puny_decode(servname, c->domain, sizeof(c->domain), &parse_err)) {
348 		log_info(c, "puny_decode: %s", parse_err);
349 		goto err;
350 	}
351 
352 	for (h = hosts; h->domain != NULL; ++h) {
353 		if (!fnmatch(h->domain, c->domain, 0))
354 			break;
355 	}
356 
357 	log_debug(c, "handshake: SNI: \"%s\"; decoded: \"%s\"; matched: \"%s\"",
358 	    servname != NULL ? servname : "(null)",
359 	    c->domain,
360 	    h->domain != NULL ? h->domain : "(null)");
361 
362 	if (h->domain != NULL) {
363 		c->host = h;
364 		c->state = handle_open_conn;
365 		c->state(fds, c);
366 		return;
367 	}
368 
369 err:
370 	if (servname != NULL)
371 		strncpy(c->req, servname, sizeof(c->req));
372 	else
373 		strncpy(c->req, "null", sizeof(c->req));
374 
375 	start_reply(fds, c, BAD_REQUEST, "Wrong/malformed host or missing SNI");
376 }
377 
378 /* 1 if a matching `block return' (and apply it), 0 otherwise */
379 static int
380 apply_block_return(struct pollfd *fds, struct client *c)
381 {
382 	char *t, *path, buf[32];
383 	const char *fmt;
384 	int strip, code;
385 	size_t i;
386 
387 	if (!vhost_block_return(c->host, c->iri.path, &code, &fmt))
388 		return 0;
389 
390 	strip = vhost_strip(c->host, c->iri.path);
391 	path = c->iri.path;
392 	while (strip > 0) {
393 		if ((t = strchr(path, '/')) == NULL) {
394 			path = strchr(path, '\0');
395 			break;
396 		}
397 		path = t;
398 		strip--;
399 	}
400 
401 	memset(buf, 0, sizeof(buf));
402 	for (i = 0; *fmt; ++fmt) {
403 		if (i == sizeof(buf)-1 || *fmt == '%') {
404 			strlcat(c->sbuf, buf, sizeof(c->sbuf));
405 			memset(buf, 0, sizeof(buf));
406 			i = 0;
407 		}
408 
409 		if (*fmt != '%') {
410 			buf[i++] = *fmt;
411 			continue;
412 		}
413 
414 		switch (*++fmt) {
415 		case '%':
416 			strlcat(c->sbuf, "%", sizeof(c->sbuf));
417 			break;
418 		case 'p':
419 			strlcat(c->sbuf, path, sizeof(c->sbuf));
420 			break;
421 		case 'q':
422 			strlcat(c->sbuf, c->iri.query, sizeof(c->sbuf));
423 			break;
424 		case 'P':
425 			snprintf(buf, sizeof(buf), "%d", conf.port);
426 			strlcat(c->sbuf, buf, sizeof(c->sbuf));
427 			memset(buf, 0, sizeof(buf));
428 			break;
429 		case 'N':
430 			strlcat(c->sbuf, c->domain, sizeof(c->sbuf));
431 			break;
432 		default:
433 			fatal("%s: unknown fmt specifier %c",
434 			    __func__, *fmt);
435 		}
436 	}
437 
438 	if (i != 0)
439 		strlcat(c->sbuf, buf, sizeof(c->sbuf));
440 
441 	start_reply(fds, c, code, c->sbuf);
442 	return 1;
443 }
444 
445 static void
446 handle_open_conn(struct pollfd *fds, struct client *c)
447 {
448 	const char *parse_err = "invalid request";
449 	char decoded[DOMAIN_NAME_LEN];
450 
451 	bzero(c->req, sizeof(c->req));
452 	bzero(&c->iri, sizeof(c->iri));
453 
454 	switch (tls_read(c->ctx, c->req, sizeof(c->req)-1)) {
455 	case -1:
456 		log_err(c, "tls_read: %s", tls_error(c->ctx));
457 		close_conn(fds, c);
458 		return;
459 
460 	case TLS_WANT_POLLIN:
461 		fds->events = POLLIN;
462 		return;
463 
464 	case TLS_WANT_POLLOUT:
465 		fds->events = POLLOUT;
466 		return;
467 	}
468 
469 	if (!trim_req_iri(c->req, &parse_err)
470 	    || !parse_iri(c->req, &c->iri, &parse_err)
471 	    || !puny_decode(c->iri.host, decoded, sizeof(decoded), &parse_err)) {
472 		log_info(c, "iri parse error: %s", parse_err);
473 		start_reply(fds, c, BAD_REQUEST, "invalid request");
474 		return;
475 	}
476 
477 	if (c->iri.port_no != conf.port
478 	    || strcmp(c->iri.schema, "gemini")
479 	    || strcmp(decoded, c->domain)) {
480 		start_reply(fds, c, PROXY_REFUSED, "won't proxy request");
481 		return;
482 	}
483 
484 	if (apply_block_return(fds, c))
485 		return;
486 
487 	if (c->host->entrypoint != NULL) {
488 		start_cgi(c->host->entrypoint, c->iri.path, fds, c);
489 		return;
490 	}
491 
492 	open_file(fds, c);
493 }
494 
495 static void
496 start_reply(struct pollfd *pfd, struct client *c, int code, const char *meta)
497 {
498 	c->code = code;
499 	c->meta = meta;
500 	c->state = handle_start_reply;
501 	handle_start_reply(pfd, c);
502 }
503 
504 static void
505 handle_start_reply(struct pollfd *pfd, struct client *c)
506 {
507 	char buf[1030];		/* status + ' ' + max reply len + \r\n\0 */
508 	const char *lang;
509 	size_t len;
510 
511 	lang = vhost_lang(c->host, c->iri.path);
512 
513 	snprintf(buf, sizeof(buf), "%d ", c->code);
514 	strlcat(buf, c->meta, sizeof(buf));
515 	if (!strcmp(c->meta, "text/gemini") && lang != NULL) {
516 		strlcat(buf, "; lang=", sizeof(buf));
517 		strlcat(buf, lang, sizeof(buf));
518 	}
519 
520 	len = strlcat(buf, "\r\n", sizeof(buf));
521 	assert(len < sizeof(buf));
522 
523 	switch (tls_write(c->ctx, buf, len)) {
524 	case -1:
525 		close_conn(pfd, c);
526 		return;
527 	case TLS_WANT_POLLIN:
528 		pfd->events = POLLIN;
529 		return;
530 	case TLS_WANT_POLLOUT:
531 		pfd->events = POLLOUT;
532 		return;
533 	}
534 
535 	log_request(c, buf, sizeof(buf));
536 
537 	/* we don't need a body */
538 	if (c->code != SUCCESS) {
539 		close_conn(pfd, c);
540 		return;
541 	}
542 
543 	/* advance the state machine */
544 	c->state = c->next;
545 	c->state(pfd, c);
546 }
547 
548 static void
549 start_cgi(const char *spath, const char *relpath,
550     struct pollfd *fds, struct client *c)
551 {
552 	char addr[NI_MAXHOST];
553 	int e;
554 
555 	e = getnameinfo((struct sockaddr*)&c->addr, sizeof(c->addr),
556 	    addr, sizeof(addr),
557 	    NULL, 0,
558 	    NI_NUMERICHOST);
559 	if (e != 0)
560 		goto err;
561 
562 	if (!send_iri(exfd, &c->iri)
563 	    || !send_string(exfd, spath)
564 	    || !send_string(exfd, relpath)
565 	    || !send_string(exfd, addr)
566 	    || !send_string(exfd, tls_peer_cert_subject(c->ctx))
567 	    || !send_string(exfd, tls_peer_cert_issuer(c->ctx))
568 	    || !send_string(exfd, tls_peer_cert_hash(c->ctx))
569 	    || !send_time(exfd, tls_peer_cert_notbefore(c->ctx))
570 	    || !send_time(exfd, tls_peer_cert_notafter(c->ctx))
571 	    || !send_vhost(exfd, c->host))
572 		goto err;
573 
574 	close(c->fd);
575 	if ((c->fd = recv_fd(exfd)) == -1) {
576 		start_reply(fds, c, TEMP_FAILURE, "internal server error");
577 		return;
578 	}
579 
580 	cgi_poll_on_child(fds, c);
581 	c->state = handle_cgi_reply;
582 	return;
583 
584 err:
585 	/* fatal("cannot talk to the executor process: %s", strerror(errno)); */
586 	fatal("cannot talk to the executor process");
587 }
588 
589 static void
590 send_file(struct pollfd *fds, struct client *c)
591 {
592 	ssize_t ret, len;
593 
594 	len = (c->buf + c->len) - c->i;
595 
596 	while (len > 0) {
597 		switch (ret = tls_write(c->ctx, c->i, len)) {
598 		case -1:
599 			log_err(c, "tls_write: %s", tls_error(c->ctx));
600 			close_conn(fds, c);
601 			return;
602 
603 		case TLS_WANT_POLLIN:
604 			fds->events = POLLIN;
605 			return;
606 
607 		case TLS_WANT_POLLOUT:
608 			fds->events = POLLOUT;
609 			return;
610 
611 		default:
612 			c->i += ret;
613 			len -= ret;
614 			break;
615 		}
616 	}
617 
618 	close_conn(fds, c);
619 }
620 
621 static void
622 open_dir(struct pollfd *fds, struct client *c)
623 {
624 	size_t len;
625 	int dirfd;
626 	char *before_file;
627 
628 	len = strlen(c->iri.path);
629 	if (len > 0 && !ends_with(c->iri.path, "/")) {
630 		redirect_canonical_dir(fds, c);
631 		return;
632 	}
633 
634 	strlcpy(c->sbuf, "/", sizeof(c->sbuf));
635 	strlcat(c->sbuf, c->iri.path, sizeof(c->sbuf));
636 	if (!ends_with(c->sbuf, "/"))
637 		strlcat(c->sbuf, "/", sizeof(c->sbuf));
638 	before_file = strchr(c->sbuf, '\0');
639 	len = strlcat(c->sbuf, vhost_index(c->host, c->iri.path),
640 	    sizeof(c->sbuf));
641 	if (len >= sizeof(c->sbuf)) {
642 		start_reply(fds, c, TEMP_FAILURE, "internal server error");
643 		return;
644 	}
645 
646 	c->iri.path = c->sbuf;
647 
648 	/* close later unless we have to generate the dir listing */
649 	dirfd = c->fd;
650 	c->fd = -1;
651 
652 	switch (check_path(c, c->iri.path, &c->fd)) {
653 	case FILE_EXECUTABLE:
654 		if (c->host->cgi != NULL && !fnmatch(c->host->cgi, c->iri.path, 0)) {
655 			start_cgi(c->iri.path, "", fds, c);
656 			break;
657 		}
658 
659 		/* fallthrough */
660 
661 	case FILE_EXISTS:
662                 load_file(fds, c);
663 		break;
664 
665 	case FILE_DIRECTORY:
666 		start_reply(fds, c, TEMP_REDIRECT, c->sbuf);
667 		break;
668 
669 	case FILE_MISSING:
670 		*before_file = '\0';
671 
672 		if (!vhost_auto_index(c->host, c->iri.path)) {
673 			start_reply(fds, c, NOT_FOUND, "not found");
674 			break;
675 		}
676 
677 		c->fd = dirfd;
678 		c->next = enter_handle_dirlist;
679 
680 		if ((c->dir = fdopendir(c->fd)) == NULL) {
681 			log_err(c, "fdopendir(%d) (vhost:%s) %s: %s",
682 			    c->fd, c->host->domain, c->iri.path, strerror(errno));
683 			start_reply(fds, c, TEMP_FAILURE, "internal server error");
684 			return;
685 		}
686 		c->off = 0;
687 
688                 start_reply(fds, c, SUCCESS, "text/gemini");
689 		return;
690 
691 	default:
692 		/* unreachable */
693 		abort();
694 	}
695 
696 	close(dirfd);
697 }
698 
699 static void
700 redirect_canonical_dir(struct pollfd *fds, struct client *c)
701 {
702 	size_t len;
703 
704 	strlcpy(c->sbuf, "/", sizeof(c->sbuf));
705 	strlcat(c->sbuf, c->iri.path, sizeof(c->sbuf));
706 	len = strlcat(c->sbuf, "/", sizeof(c->sbuf));
707 
708 	if (len >= sizeof(c->sbuf)) {
709 		start_reply(fds, c, TEMP_FAILURE, "internal server error");
710 		return;
711 	}
712 
713 	start_reply(fds, c, TEMP_REDIRECT, c->sbuf);
714 }
715 
716 static void
717 enter_handle_dirlist(struct pollfd *fds, struct client *c)
718 {
719 	char b[PATH_MAX];
720 	size_t l;
721 
722 	strlcpy(b, c->iri.path, sizeof(b));
723 	l = snprintf(c->sbuf, sizeof(c->sbuf),
724 	    "# Index of %s\n\n", b);
725 	if (l >= sizeof(c->sbuf)) {
726 		/* this is impossible, given that we have enough space
727 		 * in c->sbuf to hold the ancilliary string plus the
728 		 * full path; but it wouldn't read nice without some
729 		 * error checking, and I'd like to avoid a strlen. */
730 		close_conn(fds, c);
731 		return;
732 	}
733 	c->len = l;
734 
735 	c->state = handle_dirlist;
736 	handle_dirlist(fds, c);
737 }
738 
739 static void
740 handle_dirlist(struct pollfd *fds, struct client *c)
741 {
742 	ssize_t r;
743 
744 	while (c->len > 0) {
745 		switch (r = tls_write(c->ctx, c->sbuf + c->off, c->len)) {
746 		case -1:
747 			close_conn(fds, c);
748 			return;
749 		case TLS_WANT_POLLOUT:
750 			fds->events = POLLOUT;
751 			return;
752 		case TLS_WANT_POLLIN:
753 			fds->events = POLLIN;
754 			return;
755 		default:
756 			c->off += r;
757 			c->len -= r;
758 		}
759 	}
760 
761 	c->state = send_directory_listing;
762 	send_directory_listing(fds, c);
763 }
764 
765 static int
766 read_next_dir_entry(struct client *c)
767 {
768 	struct dirent *d;
769 
770 	do {
771 		errno = 0;
772 		if ((d = readdir(c->dir)) == NULL) {
773 			if (errno != 0)
774 				log_err(c, "readdir: %s", strerror(errno));
775 			return 0;
776 		}
777 	} while (!strcmp(d->d_name, "."));
778 
779 	/* XXX: url escape */
780 	snprintf(c->sbuf, sizeof(c->sbuf), "=> %s %s\n",
781 	    d->d_name, d->d_name);
782 	c->len = strlen(c->sbuf);
783 	c->off = 0;
784 
785 	return 1;
786 }
787 
788 static void
789 send_directory_listing(struct pollfd *fds, struct client *c)
790 {
791 	ssize_t r;
792 
793 	while (1) {
794 		if (c->len == 0) {
795 			if (!read_next_dir_entry(c))
796 				goto end;
797 		}
798 
799 		while (c->len > 0) {
800 			switch (r = tls_write(c->ctx, c->sbuf + c->off, c->len)) {
801 			case -1:
802 				goto end;
803 
804 			case TLS_WANT_POLLOUT:
805 				fds->events = POLLOUT;
806 				return;
807 
808 			case TLS_WANT_POLLIN:
809 				fds->events = POLLIN;
810 				return;
811 
812 			default:
813 				c->off += r;
814 				c->len -= r;
815 				break;
816 			}
817 		}
818 	}
819 
820 end:
821 	close_conn(fds, c);
822 }
823 
824 static inline void
825 cgi_poll_on_child(struct pollfd *fds, struct client *c)
826 {
827 	int fd;
828 
829 	if (c->waiting_on_child)
830 		return;
831 	c->waiting_on_child = 1;
832 
833 	fds->events = POLLIN;
834 
835 	fd = fds->fd;
836 	fds->fd = c->fd;
837 	c->fd = fd;
838 }
839 
840 static inline void
841 cgi_poll_on_client(struct pollfd *fds, struct client *c)
842 {
843 	int fd;
844 
845 	if (!c->waiting_on_child)
846 		return;
847 	c->waiting_on_child = 0;
848 
849 	fd = fds->fd;
850 	fds->fd = c->fd;
851 	c->fd = fd;
852 }
853 
854 /* accumulate the meta line from the cgi script. */
855 static void
856 handle_cgi_reply(struct pollfd *fds, struct client *c)
857 {
858 	void	*buf, *e;
859 	size_t	 len;
860 	ssize_t	 r;
861 
862 	buf = c->sbuf + c->len;
863 	len = sizeof(c->sbuf) - c->len;
864 
865 	/* we're polling on the child! */
866 	r = read(fds->fd, buf, len);
867 	if (r == 0 || r == -1) {
868 		cgi_poll_on_client(fds, c);
869 		start_reply(fds, c, CGI_ERROR, "CGI error");
870 		return;
871 	}
872 
873 	c->len += r;
874 
875 	/* TODO: error if the CGI script don't reply correctly */
876 	e = strchr(c->sbuf, '\n');
877 	if (e != NULL || c->len == sizeof(c->sbuf)) {
878 		log_request(c, c->sbuf, c->len);
879 
880 		c->off = 0;
881 		c->state = handle_cgi;
882 		c->state(fds, c);
883 		return;
884 	}
885 }
886 
887 static void
888 handle_cgi(struct pollfd *fds, struct client *c)
889 {
890 	ssize_t r;
891 
892 	/* ensure c->fd is the child and fds->fd the client */
893 	cgi_poll_on_client(fds, c);
894 
895 	while (1) {
896 		if (c->len == 0) {
897 			switch (r = read(c->fd, c->sbuf, sizeof(c->sbuf))) {
898 			case 0:
899 				goto end;
900 			case -1:
901 				if (errno == EAGAIN || errno == EWOULDBLOCK) {
902 					cgi_poll_on_child(fds, c);
903 					return;
904 				}
905 				goto end;
906 			default:
907 				c->len = r;
908 				c->off = 0;
909 			}
910 		}
911 
912 		while (c->len > 0) {
913 			switch (r = tls_write(c->ctx, c->sbuf + c->off, c->len)) {
914 			case -1:
915 				goto end;
916 
917 			case TLS_WANT_POLLOUT:
918 				fds->events = POLLOUT;
919 				return;
920 
921 			case TLS_WANT_POLLIN:
922 				fds->events = POLLIN;
923 				return;
924 
925 			default:
926                                 c->off += r;
927 				c->len -= r;
928 				break;
929 			}
930 		}
931 	}
932 
933 end:
934 	close_conn(fds, c);
935 }
936 
937 static void
938 close_conn(struct pollfd *pfd, struct client *c)
939 {
940 	c->state = close_conn;
941 
942 	switch (tls_close(c->ctx)) {
943 	case TLS_WANT_POLLIN:
944 		pfd->events = POLLIN;
945 		return;
946 	case TLS_WANT_POLLOUT:
947 		pfd->events = POLLOUT;
948 		return;
949 	}
950 
951 	connected_clients--;
952 
953 	tls_free(c->ctx);
954 	c->ctx = NULL;
955 
956 	if (c->buf != MAP_FAILED)
957 		munmap(c->buf, c->len);
958 
959 	if (c->fd != -1)
960 		close(c->fd);
961 
962 	if (c->dir != NULL)
963 		closedir(c->dir);
964 
965 	close(pfd->fd);
966 	pfd->fd = -1;
967 }
968 
969 static void
970 do_accept(int sock, struct tls *ctx, struct pollfd *fds, struct client *clients)
971 {
972 	int i, fd;
973 	struct sockaddr_storage addr;
974 	socklen_t len;
975 
976 	len = sizeof(addr);
977 	if ((fd = accept(sock, (struct sockaddr*)&addr, &len)) == -1) {
978 		if (errno == EWOULDBLOCK || errno == EAGAIN)
979 			return;
980 		fatal("accept: %s", strerror(errno));
981 	}
982 
983 	mark_nonblock(fd);
984 
985 	for (i = 0; i < MAX_USERS; ++i) {
986 		if (fds[i].fd == -1) {
987 			bzero(&clients[i], sizeof(struct client));
988 			if (tls_accept_socket(ctx, &clients[i].ctx, fd) == -1)
989 				break; /* goodbye fd! */
990 
991 			fds[i].fd = fd;
992 			fds[i].events = POLLIN;
993 
994 			clients[i].state = handle_handshake;
995 			clients[i].next = send_file;
996 			clients[i].fd = -1;
997 			clients[i].waiting_on_child = 0;
998 			clients[i].buf = MAP_FAILED;
999 			clients[i].dir = NULL;
1000 			clients[i].addr = addr;
1001 
1002 			connected_clients++;
1003 			return;
1004 		}
1005 	}
1006 
1007 	close(fd);
1008 }
1009 
1010 void
1011 loop(struct tls *ctx, int sock4, int sock6)
1012 {
1013 	int i, n;
1014 	struct client clients[MAX_USERS];
1015 	struct pollfd fds[MAX_USERS];
1016 
1017 	for (i = 0; i < MAX_USERS; ++i) {
1018 		fds[i].fd = -1;
1019 		fds[i].events = POLLIN;
1020 		bzero(&clients[i], sizeof(struct client));
1021 	}
1022 
1023 	fds[0].fd = sock4;
1024 	fds[1].fd = sock6;
1025 
1026 	for (;;) {
1027 		if ((n = poll(fds, MAX_USERS, INFTIM)) == -1) {
1028 			if (errno == EINTR) {
1029 				log_info(NULL, "%d connected clients",
1030 				    connected_clients);
1031 			} else
1032 				fatal("poll: %s", strerror(errno));
1033 		}
1034 
1035 		for (i = 0; i < MAX_USERS && n > 0; i++) {
1036 			if (fds[i].revents == 0)
1037 				continue;
1038 
1039 			if (fds[i].revents & (POLLERR|POLLNVAL))
1040 				fatal("bad fd %d: %s", fds[i].fd,
1041 				    strerror(errno));
1042 
1043 			n--;
1044 
1045 			if (fds[i].revents & POLLHUP) {
1046 				/* fds[i] may be the fd of the stdin
1047 				 * of a cgi script that has exited. */
1048 				if (!clients[i].waiting_on_child) {
1049 					close_conn(&fds[i], &clients[i]);
1050 					continue;
1051 				}
1052 			}
1053 
1054 			if (fds[i].fd == sock4)
1055 				do_accept(sock4, ctx, fds, clients);
1056 			else if (fds[i].fd == sock6)
1057 				do_accept(sock6, ctx, fds, clients);
1058 			else
1059 				clients[i].state(&fds[i], &clients[i]);
1060 		}
1061 
1062 		if (hupped) {
1063 			if (connected_clients == 0)
1064 				return;
1065 
1066 			fds[0].fd = -1;
1067 			if (sock6 != -1)
1068 				fds[1].fd = -1;
1069 		}
1070 	}
1071 }