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Date:: Tue Nov 3 14:48:26 2020 UTC
Message:: ignore SIGPIPE bad clients can shutdown the socket and we will exit due to a SIGPIPE. it ain’t fun.
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1 /*
2  * Copyright (c) 2020 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/socket.h>
19 #include <sys/stat.h>
20 
21 #include <netinet/in.h>
22 
23 #include <assert.h>
24 #include <err.h>
25 #include <errno.h>
26 #include <fcntl.h>
27 #include <poll.h>
28 #include <signal.h>
29 #include <stdio.h>
30 #include <stdlib.h>
31 #include <string.h>
32 #include <tls.h>
33 #include <unistd.h>
34 
35 #ifndef __OpenBSD__
36 # define pledge(a, b) 0
37 # define unveil(a, b) 0
38 #endif /* __OpenBSD__ */
39 
40 #ifndef INFTIM
41 # define INFTIM -1
42 #endif /* INFTIM */
43 
44 #define GEMINI_URL_LEN (1024+3)	/* URL max len + \r\n + \0 */
45 
46 /* large enough to hold a copy of a gemini URL and still have extra room */
47 #define PATHBUF		2048
48 
49 #define SUCCESS		20
50 #define NOT_FOUND	51
51 #define BAD_REQUEST	59
52 
53 #ifndef MAX_USERS
54 #define MAX_USERS	64
55 #endif
56 
57 enum {
58 	S_OPEN,
59 	S_INITIALIZING,
60 	S_SENDING,
61 	S_CLOSING,
62 };
63 
64 struct client {
65 	struct tls	*ctx;
66 	int		 state;
67 	int		 code;
68 	const char	*meta;
69 	int		 fd;
70 	void		*buf, *i;
71 	ssize_t		 len, off;
72 };
73 
74 struct etm {			/* file extension to mime */
75 	const char	*mime;
76 	const char	*ext;
77 } filetypes[] = {
78 	{"application/pdf",	"pdf"},
79 
80 	{"image/gif",		"gif"},
81 	{"image/jpeg",		"jpg"},
82 	{"image/jpeg",		"jpeg"},
83 	{"image/png",		"png"},
84 	{"image/svg+xml",	"svg"},
85 
86 	{"text/gemini",		"gemini"},
87 	{"text/gemini",		"gmi"},
88 	{"text/markdown",	"markdown"},
89 	{"text/markdown",	"md"},
90 	{"text/plain",		"txt"},
91 
92 	{NULL, NULL}
93 };
94 
95 int dirfd;
96 
97 char		*url_after_proto(char*);
98 char		*url_start_of_request(char*);
99 int		 url_trim(char*);
100 void		 adjust_path(char*);
101 int		 path_isdir(char*);
102 ssize_t		 filesize(int);
103 
104 int		 start_reply(struct pollfd*, struct client*, int, const char*);
105 int		 isdir(int);
106 const char	*path_ext(const char*);
107 const char	*mime(const char*);
108 int		 open_file(char*, struct pollfd*, struct client*);
109 void		 send_file(char*, struct pollfd*, struct client*);
110 void		 send_dir(char*, struct pollfd*, struct client*);
111 void		 handle(struct pollfd*, struct client*);
112 
113 void		 mark_nonblock(int);
114 int		 make_soket(int);
115 void		 do_accept(int, struct tls*, struct pollfd*, struct client*);
116 void		 goodbye(struct pollfd*, struct client*);
117 void		 loop(struct tls*, int);
118 
119 void		 usage(const char*);
120 
121 char *
122 url_after_proto(char *url)
123 {
124 	char *s;
125 	const char *proto = "gemini";
126 	const char *marker = "://";
127 
128 	if ((s = strstr(url, marker)) == NULL)
129 		return url;
130 
131 	/* not a gemini:// URL */
132 
133 	if (s - strlen(proto) < url)
134 		return NULL;
135 	/* TODO: */
136 	/* if (strcmp(s - strlen(proto), proto)) */
137 	/* 	return NULL; */
138 
139 	/* a valid gemini:// URL */
140 	return s + strlen(marker);
141 }
142 
143 char *
144 url_start_of_request(char *url)
145 {
146 	char *s, *t;
147 
148 	if ((s = url_after_proto(url)) == NULL)
149 		return NULL;
150 
151 	if ((t = strstr(s, "/")) == NULL)
152 		return s + strlen(s);
153 	return t;
154 }
155 
156 int
157 url_trim(char *url)
158 {
159 	const char *e = "\r\n";
160 	char *s;
161 
162 	if ((s = strstr(url, e)) == NULL)
163 		return 0;
164 	s[0] = '\0';
165 	s[1] = '\0';
166 
167 	if (s[2] != '\0') {
168 		fprintf(stderr, "the request was longer than 1024 bytes\n");
169 		return 0;
170 	}
171 
172 	return 1;
173 }
174 
175 void
176 adjust_path(char *path)
177 {
178 	char *s;
179 	size_t len;
180 
181 	/* /.. -> / */
182 	len = strlen(path);
183 	if (len >= 3) {
184 		if (!strcmp(&path[len-3], "/..")) {
185 			path[len-2] = '\0';
186 		}
187 	}
188 
189 	/* if the path is only `..` trim out and exit */
190 	if (!strcmp(path, "..")) {
191 		path[0] = '\0';
192 		return;
193 	}
194 
195 	/* remove every ../ in the path */
196 	while (1) {
197 		if ((s = strstr(path, "../")) == NULL)
198 			return;
199 		memmove(s, s+3, strlen(s)+1);	/* copy also the \0 */
200 	}
201 }
202 
203 int
204 path_isdir(char *path)
205 {
206 	if (*path == '\0')
207 		return 1;
208 	return path[strlen(path)-1] == '/';
209 }
210 
211 int
212 start_reply(struct pollfd *pfd, struct client *client, int code, const char *reason)
213 {
214 	char buf[1030] = {0}; 	/* status + ' ' + max reply len + \r\n\0 */
215 	int len;
216 	int ret;
217 
218 	client->code = code;
219 	client->meta = reason;
220 	client->state = S_INITIALIZING;
221 
222 	len = snprintf(buf, sizeof(buf), "%d %s\r\n", code, reason);
223 	assert(len < (int)sizeof(buf));
224 	ret = tls_write(client->ctx, buf, len);
225 	if (ret == TLS_WANT_POLLIN) {
226 		pfd->events = POLLIN;
227 		return 0;
228 	}
229 
230 	if (ret == TLS_WANT_POLLOUT) {
231 		pfd->events = POLLOUT;
232 		return 0;
233 	}
234 
235 	return 1;
236 }
237 
238 int
239 isdir(int fd)
240 {
241 	struct stat sb;
242 
243 	if (fstat(fd, &sb) == -1) {
244 		warn("fstat");
245 		return 1; 	/* we'll probably fail later on anyway */
246 	}
247 
248 	return S_ISDIR(sb.st_mode);
249 }
250 
251 ssize_t
252 filesize(int fd)
253 {
254 	ssize_t len;
255 
256 	if ((len = lseek(fd, 0, SEEK_END)) == -1)
257 		return -1;
258 	if (lseek(fd, 0, SEEK_SET) == -1)
259 		return -1;
260 	return len;
261 }
262 
263 const char *
264 path_ext(const char *path)
265 {
266 	const char *end;
267 
268 	end = path + strlen(path)-1; /* the last byte before the NUL */
269 	for (; end != path; --end) {
270 		if (*end == '.')
271 			return end+1;
272 		if (*end == '/')
273 			break;
274 	}
275 
276 	return NULL;
277 }
278 
279 const char *
280 mime(const char *path)
281 {
282 	const char *ext, *def = "application/octet-stream";
283 	struct etm *t;
284 
285 	if ((ext = path_ext(path)) == NULL)
286 		return def;
287 
288 	for (t = filetypes; t->mime != NULL; ++t)
289 		if (!strcmp(ext, t->ext))
290 			return t->mime;
291 
292 	return def;
293 }
294 
295 int
296 open_file(char *path, struct pollfd *fds, struct client *c)
297 {
298 	char fpath[PATHBUF];
299 
300 	assert(path != NULL);
301 
302 	bzero(fpath, sizeof(fpath));
303 
304 	if (*path != '.')
305 		fpath[0] = '.';
306 	strlcat(fpath, path, PATHBUF);
307 
308 	if ((c->fd = openat(dirfd, fpath, O_RDONLY | O_NOFOLLOW)) == -1) {
309 		warn("open: %s", fpath);
310 		if (!start_reply(fds, c, NOT_FOUND, "not found"))
311 			return 0;
312 		goodbye(fds, c);
313 		return 0;
314 	}
315 
316 	if (isdir(c->fd)) {
317 		warnx("%s is a directory, trying %s/index.gmi", fpath, fpath);
318 		close(c->fd);
319 		c->fd = -1;
320 		send_dir(fpath, fds, c);
321 		return 0;
322 	}
323 
324 	if ((c->len = filesize(c->fd)) == -1) {
325 		warn("filesize: %s", fpath);
326 		goodbye(fds, c);
327 		return 0;
328 	}
329 
330 	if ((c->buf = mmap(NULL, c->len, PROT_READ, MAP_PRIVATE,
331 		    c->fd, 0)) == MAP_FAILED) {
332 		warn("mmap: %s", fpath);
333 		goodbye(fds, c);
334 		return 0;
335 	}
336 	c->i = c->buf;
337 
338 	return start_reply(fds, c, SUCCESS, mime(fpath));
339 }
340 
341 void
342 send_file(char *path, struct pollfd *fds, struct client *c)
343 {
344 	ssize_t ret, len;
345 
346 	if (c->fd == -1) {
347 		if (!open_file(path, fds, c))
348 			return;
349 		c->state = S_SENDING;
350 	}
351 
352 	len = (c->buf + c->len) - c->i;
353 
354 	while (len > 0) {
355 		switch (ret = tls_write(c->ctx, c->i, len)) {
356 		case -1:
357 			warnx("tls_write: %s", tls_error(c->ctx));
358 			goodbye(fds, c);
359 			return;
360 
361 		case TLS_WANT_POLLIN:
362 			fds->events = POLLIN;
363 			return;
364 
365 		case TLS_WANT_POLLOUT:
366 			fds->events = POLLOUT;
367 			return;
368 
369 		default:
370 			c->i += ret;
371 			len -= ret;
372 			break;
373 		}
374 	}
375 
376 	goodbye(fds, c);
377 }
378 
379 void
380 send_dir(char *path, struct pollfd *fds, struct client *client)
381 {
382 	char fpath[PATHBUF];
383 	size_t len;
384 
385 	bzero(fpath, PATHBUF);
386 
387 	if (path[0] != '.')
388 		fpath[0] = '.';
389 
390 	/* this cannot fail since sizeof(fpath) > maxlen of path */
391 	strlcat(fpath, path, PATHBUF);
392 	len = strlen(fpath);
393 
394 	/* add a trailing / in case. */
395 	if (fpath[len-1] != '/') {
396 		fpath[len] = '/';
397 	}
398 
399 	strlcat(fpath, "index.gmi", sizeof(fpath));
400 
401 	send_file(fpath, fds, client);
402 }
403 
404 void
405 handle(struct pollfd *fds, struct client *client)
406 {
407 	char buf[GEMINI_URL_LEN];
408 	char *path;
409 
410 	switch (client->state) {
411 	case S_OPEN:
412 		bzero(buf, GEMINI_URL_LEN);
413 		switch (tls_read(client->ctx, buf, sizeof(buf)-1)) {
414 		case -1:
415 			warnx("tls_read: %s", tls_error(client->ctx));
416 			goodbye(fds, client);
417 			return;
418 
419 		case TLS_WANT_POLLIN:
420 			fds->events = POLLIN;
421 			return;
422 
423 		case TLS_WANT_POLLOUT:
424 			fds->events = POLLOUT;
425 			return;
426 		}
427 
428 		if (!url_trim(buf)) {
429 			if (!start_reply(fds, client, BAD_REQUEST, "bad request"))
430 				return;
431 			goodbye(fds, client);
432 			return;
433 		}
434 
435 		if ((path = url_start_of_request(buf)) == NULL) {
436 			if (!start_reply(fds, client, BAD_REQUEST, "bad request"))
437 				return;
438 			goodbye(fds, client);
439 			return;
440 		}
441 
442 		adjust_path(path);
443 		fprintf(stderr, "requested path: %s\n", path);
444 
445 		if (path_isdir(path))
446 			send_dir(path, fds, client);
447 		else
448 			send_file(path, fds, client);
449 		break;
450 
451 	case S_INITIALIZING:
452 		if (!start_reply(fds, client, client->code, client->meta))
453 			return;
454 
455 		if (client->code != SUCCESS) {
456 			/* we don't need a body */
457 			goodbye(fds, client);
458 			return;
459 		}
460 
461 		client->state = S_SENDING;
462 
463 		/* fallthrough */
464 
465 	case S_SENDING:
466 		send_file(NULL, fds, client);
467 		break;
468 
469 	case S_CLOSING:
470 		goodbye(fds, client);
471 		break;
472 
473 	default:
474 		/* unreachable */
475 		abort();
476 	}
477 }
478 
479 void
480 mark_nonblock(int fd)
481 {
482 	int flags;
483 
484 	if ((flags = fcntl(fd, F_GETFL)) == -1)
485 		err(1, "fcntl(F_GETFL)");
486 	if (fcntl(fd, F_SETFL, flags | O_NONBLOCK) == -1)
487 		err(1, "fcntl(F_SETFL)");
488 }
489 
490 int
491 make_socket(int port, int family)
492 {
493 	int sock, v;
494 	struct sockaddr_in addr4;
495 	struct sockaddr_in6 addr6;
496 	struct sockaddr *addr;
497 	socklen_t len;
498 
499         switch (family) {
500 	case AF_INET:
501 		bzero(&addr4, sizeof(addr4));
502 		addr4.sin_family = family;
503 		addr4.sin_port = htons(port);
504 		addr4.sin_addr.s_addr = INADDR_ANY;
505 		addr = (struct sockaddr*)&addr4;
506 		len = sizeof(addr4);
507 		break;
508 
509 	case AF_INET6:
510 		bzero(&addr6, sizeof(addr6));
511 		addr6.sin6_family = AF_INET6;
512 		addr6.sin6_port = htons(port);
513 		addr6.sin6_addr = in6addr_any;
514 		addr = (struct sockaddr*)&addr6;
515 		len = sizeof(addr6);
516 		break;
517 
518 	default:
519 		/* unreachable */
520 		abort();
521 	}
522 
523 	if ((sock = socket(family, SOCK_STREAM, 0)) == -1)
524 		err(1, "socket");
525 
526 	v = 1;
527 	if (setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &v, sizeof(v)) == -1)
528 		err(1, "setsockopt(SO_REUSEADDR)");
529 
530 	v = 1;
531 	if (setsockopt(sock, SOL_SOCKET, SO_REUSEPORT, &v, sizeof(v)) == -1)
532 		err(1, "setsockopt(SO_REUSEPORT)");
533 
534 	mark_nonblock(sock);
535 
536 	if (bind(sock, addr, len) == -1)
537 		err(1, "bind");
538 
539 	if (listen(sock, 16) == -1)
540 		err(1, "listen");
541 
542 	return sock;
543 }
544 
545 void
546 do_accept(int sock, struct tls *ctx, struct pollfd *fds, struct client *clients)
547 {
548 	int i, fd;
549 	struct sockaddr_in addr;
550 	socklen_t len;
551 
552 	len = sizeof(addr);
553 	if ((fd = accept(sock, (struct sockaddr*)&addr, &len)) == -1) {
554 		if (errno == EWOULDBLOCK)
555 			return;
556 		err(1, "accept");
557 	}
558 
559 	mark_nonblock(fd);
560 
561 	for (i = 0; i < MAX_USERS; ++i) {
562 		if (fds[i].fd == -1) {
563 			bzero(&clients[i], sizeof(struct client));
564 			if (tls_accept_socket(ctx, &clients[i].ctx, fd) == -1)
565 				break; /* goodbye fd! */
566 
567 			fds[i].fd = fd;
568 			fds[i].events = POLLIN;
569 
570 			clients[i].state = S_OPEN;
571 			clients[i].fd = -1;
572 			clients[i].buf = MAP_FAILED;
573 
574 			return;
575 		}
576 	}
577 
578 	close(fd);
579 }
580 
581 void
582 goodbye(struct pollfd *pfd, struct client *c)
583 {
584 	ssize_t ret;
585 
586 	c->state = S_CLOSING;
587 
588 	ret = tls_close(c->ctx);
589 	if (ret == TLS_WANT_POLLIN) {
590 		pfd->events = POLLIN;
591 		return;
592 	}
593 	if (ret == TLS_WANT_POLLOUT) {
594 		pfd->events = POLLOUT;
595 		return;
596 	}
597 
598 	tls_free(c->ctx);
599 	c->ctx = NULL;
600 
601 	if (c->buf != MAP_FAILED)
602 		munmap(c->buf, c->len);
603 
604 	if (c->fd != -1)
605 		close(c->fd);
606 
607 	close(pfd->fd);
608 	pfd->fd = -1;
609 }
610 
611 void
612 loop(struct tls *ctx, int sock)
613 {
614 	int i, todo;
615 	struct client clients[MAX_USERS];
616 	struct pollfd fds[MAX_USERS];
617 
618 	for (i = 0; i < MAX_USERS; ++i) {
619 		fds[i].fd = -1;
620 		fds[i].events = POLLIN;
621 		bzero(&clients[i], sizeof(struct client));
622 	}
623 
624 	fds[0].fd = sock;
625 
626 	for (;;) {
627 		if ((todo = poll(fds, MAX_USERS, INFTIM)) == -1)
628 			err(1, "poll");
629 
630 		for (i = 0; i < MAX_USERS; i++) {
631 			assert(i < MAX_USERS);
632 
633 			if (fds[i].revents == 0)
634 				continue;
635 
636 			if (fds[i].revents & (POLLERR|POLLNVAL))
637 				err(1, "bad fd %d", fds[i].fd);
638 
639 			if (fds[i].revents & POLLHUP) {
640 				goodbye(&fds[i], &clients[i]);
641 				continue;
642 			}
643 
644 			todo--;
645 
646 			if (i == 0) { /* new client */
647 				do_accept(sock, ctx, fds, clients);
648 				continue;
649 			}
650 
651 			handle(&fds[i], &clients[i]);
652 		}
653 	}
654 }
655 
656 void
657 usage(const char *me)
658 {
659 	fprintf(stderr,
660 	    "USAGE: %s [-h] [-c cert.pem] [-d docs] [-k key.pem]\n",
661 	    me);
662 }
663 
664 int
665 main(int argc, char **argv)
666 {
667 	const char *cert = "cert.pem", *key = "key.pem", *dir = "docs";
668 	struct tls *ctx = NULL;
669 	struct tls_config *conf;
670 	int sock, ch;
671 
672 	signal(SIGPIPE, SIG_IGN);
673 
674 	while ((ch = getopt(argc, argv, "c:d:hk:")) != -1) {
675 		switch (ch) {
676 		case 'c':
677 			cert = optarg;
678 			break;
679 
680 		case 'd':
681 			dir = optarg;
682 			break;
683 
684 		case 'h':
685 			usage(*argv);
686 			return 0;
687 
688 		case 'k':
689 			key = optarg;
690 			break;
691 
692 		default:
693 			usage(*argv);
694 			return 1;
695 		}
696 	}
697 
698 	if ((conf = tls_config_new()) == NULL)
699 		err(1, "tls_config_new");
700 
701 	if (tls_config_set_protocols(conf,
702 	    TLS_PROTOCOL_TLSv1_2 | TLS_PROTOCOL_TLSv1_3) == -1)
703 		err(1, "tls_config_set_protocols");
704 
705 	if (tls_config_set_cert_file(conf, cert) == -1)
706 		err(1, "tls_config_set_cert_file: %s", cert);
707 
708 	if (tls_config_set_key_file(conf, key) == -1)
709 		err(1, "tls_config_set_key_file: %s", key);
710 
711 	if ((ctx = tls_server()) == NULL)
712 		err(1, "tls_server");
713 
714 	if (tls_configure(ctx, conf) == -1)
715 		errx(1, "tls_configure: %s", tls_error(ctx));
716 
717 	sock = make_socket(1965, AF_INET);
718 
719 	if ((dirfd = open(dir, O_RDONLY | O_DIRECTORY)) == -1)
720 		err(1, "open: %s", dir);
721 
722 	if (unveil(dir, "r") == -1)
723 		err(1, "unveil");
724 
725 	if (pledge("stdio rpath inet", "") == -1)
726 		err(1, "pledge");
727 
728 	loop(ctx, sock);
729 
730 	close(sock);
731 	tls_free(ctx);
732 	tls_config_free(conf);
733 }