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