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