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 /*
18  * TODO:
19  *  - move the various
20  *	imsg_compose(...);
21  *	imsg_flush(...);
22  *    to something more asynchronous
23  */
24 
25 #include <telescope.h>
26 
27 #include <sys/types.h>
28 #include <sys/socket.h>
29 
30 #include <netinet/in.h>
31 
32 #include <assert.h>
33 #include <ctype.h>
34 #include <errno.h>
35 #include <event.h>
36 #include <netdb.h>
37 #include <stdarg.h>
38 #include <stdio.h>
39 #include <stdlib.h>
40 #include <string.h>
41 #include <tls.h>
42 #include <unistd.h>
43 
44 static struct tls_config	*tlsconf;
45 static struct imsgbuf		*ibuf;
46 
47 struct req;
48 
49 static void		 die(void) __attribute__((__noreturn__));
50 static char		*xasprintf(const char*, ...);
51 static int 		 conn_towards(struct url*, char**);
52 
53 static void		 close_with_err(struct req*, const char *err);
54 static struct req	*req_by_id(uint32_t);
55 
56 static void		 do_handshake(int, short, void*);
57 static void		 write_request(int, short, void*);
58 static void		 read_reply(int, short, void*);
59 static void		 parse_reply(struct req*);
60 static void		 copy_body(int, short, void*);
61 
62 static void		 check_special_page(struct req*, const char*);
63 
64 static void		 handle_get(struct imsg*, size_t);
65 static void		 handle_cert_status(struct imsg*, size_t);
66 static void		 handle_proceed(struct imsg*, size_t);
67 static void		 handle_stop(struct imsg*, size_t);
68 static void		 handle_quit(struct imsg*, size_t);
69 
70 /* TODO: making this customizable */
71 struct timeval timeout_for_handshake = { 5, 0 };
72 
73 static imsg_handlerfn *handlers[] = {
74 	[IMSG_GET] = handle_get,
75 	[IMSG_CERT_STATUS] = handle_cert_status,
76 	[IMSG_PROCEED] = handle_proceed,
77 	[IMSG_STOP] = handle_stop,
78 	[IMSG_QUIT] = handle_quit,
79 };
80 
81 typedef void (*statefn)(int, short, void*);
82 
83 TAILQ_HEAD(, req) reqhead;
84 /* a pending request */
85 struct req {
86 	struct event		 ev;
87 	struct url		 url;
88 	uint32_t		 id;
89 	int			 fd;
90 	struct tls		*ctx;
91 	char			 buf[1024];
92 	size_t			 off;
93 	TAILQ_ENTRY(req)	 reqs;
94 };
95 
96 static inline void
97 yield_r(struct req *req, statefn fn, struct timeval *tv)
98 {
99 	event_once(req->fd, EV_READ, fn, req, tv);
100 }
101 
102 static inline void
103 yield_w(struct req *req, statefn fn, struct timeval *tv)
104 {
105 	event_once(req->fd, EV_WRITE, fn, req, tv);
106 }
107 
108 static inline void
109 advance_buf(struct req *req, size_t len)
110 {
111 	assert(len <= req->off);
112 
113 	req->off -= len;
114 	memmove(req->buf, req->buf + len, req->off);
115 }
116 
117 static void __attribute__((__noreturn__))
118 die(void)
119 {
120 	abort(); 		/* TODO */
121 }
122 
123 static char *
124 xasprintf(const char *fmt, ...)
125 {
126 	va_list ap;
127 	char *s;
128 
129 	va_start(ap, fmt);
130 	if (vasprintf(&s, fmt, ap) == -1)
131 		s = NULL;
132 	va_end(ap);
133 
134 	return s;
135 }
136 
137 static int
138 conn_towards(struct url *url, char **err)
139 {
140 	struct addrinfo	 hints, *servinfo, *p;
141 	int		 status, sock;
142 	const char	*proto = "1965";
143 
144 	*err = NULL;
145 
146 	if (*url->port != '\0')
147 		proto = url->port;
148 
149 	memset(&hints, 0, sizeof(hints));
150 	hints.ai_family = AF_UNSPEC;
151 	hints.ai_socktype = SOCK_STREAM;
152 
153 	if ((status = getaddrinfo(url->host, proto, &hints, &servinfo))) {
154 		*err = xasprintf("failed to resolve %s: %s",
155 		    url->host, gai_strerror(status));
156 		return -1;
157 	}
158 
159 	sock = -1;
160 	for (p = servinfo; p != NULL; p = p->ai_next) {
161 		if ((sock = socket(p->ai_family, p->ai_socktype, p->ai_protocol)) == -1)
162 			continue;
163 		if (connect(sock, p->ai_addr, p->ai_addrlen) != -1)
164 			break;
165 		close(sock);
166 	}
167 
168 	if (sock == -1)
169 		*err = xasprintf("couldn't connect to %s", url->host);
170 	else
171 		mark_nonblock(sock);
172 
173 	freeaddrinfo(servinfo);
174 	return sock;
175 }
176 
177 static struct req *
178 req_by_id(uint32_t id)
179 {
180 	struct req *r;
181 
182 	TAILQ_FOREACH(r, &reqhead, reqs) {
183 		if (r->id == id)
184 			return r;
185 	}
186 
187 	die();
188 }
189 
190 static void
191 close_conn(int fd, short ev, void *d)
192 {
193 	struct req	*req = d;
194 
195 	if (req->ctx != NULL) {
196 		switch (tls_close(req->ctx)) {
197 		case TLS_WANT_POLLIN:
198 			yield_r(req, close_conn, NULL);
199 			return;
200 		case TLS_WANT_POLLOUT:
201 			yield_w(req, close_conn, NULL);
202 			return;
203 		}
204 
205 		tls_free(req->ctx);
206 	}
207 
208 	TAILQ_REMOVE(&reqhead, req, reqs);
209 	if (req->fd != -1)
210 		close(req->fd);
211 	free(req);
212 }
213 
214 static void
215 close_with_err(struct req *req, const char *err)
216 {
217 	imsg_compose(ibuf, IMSG_ERR, req->id, 0, -1, err, strlen(err)+1);
218 	imsg_flush(ibuf);
219 	close_conn(0, 0, req);
220 }
221 
222 static void
223 do_handshake(int fd, short ev, void *d)
224 {
225 	struct req	*req = d;
226 	const char	*hash;
227 
228 	if (ev == EV_TIMEOUT) {
229 		close_with_err(req, "Timeout loading page");
230 		return;
231 	}
232 
233 	switch (tls_handshake(req->ctx)) {
234 	case TLS_WANT_POLLIN:
235 		yield_r(req, do_handshake, NULL);
236 		return;
237 	case TLS_WANT_POLLOUT:
238 		yield_w(req, do_handshake, NULL);
239 		return;
240 	}
241 
242 	hash = tls_peer_cert_hash(req->ctx);
243 	imsg_compose(ibuf, IMSG_CHECK_CERT, req->id, 0, -1, hash, strlen(hash)+1);
244 	imsg_flush(ibuf);
245 }
246 
247 static void
248 write_request(int fd, short ev, void *d)
249 {
250 	struct req	*req = d;
251 	ssize_t		 r;
252 	size_t		 len;
253 	char		 buf[1024], *err;
254 
255 	strlcpy(buf, "gemini://", sizeof(buf));
256 	strlcat(buf, req->url.host, sizeof(buf));
257 	strlcat(buf, "/", sizeof(buf));
258 	strlcat(buf, req->url.path, sizeof(buf));
259 
260 	if (req->url.query[0] != '\0') {
261 		strlcat(buf, "?", sizeof(buf));
262 		strlcat(buf, req->url.query, sizeof(buf));
263 	}
264 
265 	len = strlcat(buf, "\r\n", sizeof(buf));
266 
267 	assert(len <= sizeof(buf));
268 
269 	switch (r = tls_write(req->ctx, buf, len)) {
270 	case -1:
271 		err = xasprintf("tls_write: %s", tls_error(req->ctx));
272 		close_with_err(req, err);
273 		free(err);
274 		break;
275 	case TLS_WANT_POLLIN:
276 		yield_r(req, write_request, NULL);
277 		break;
278 	case TLS_WANT_POLLOUT:
279 		yield_w(req, write_request, NULL);
280 		break;
281 	default:
282 		/* assume r == len */
283 		(void)r;
284 		yield_r(req, read_reply, NULL);
285 		break;
286 	}
287 }
288 
289 static void
290 read_reply(int fd, short ev, void *d)
291 {
292 	struct req	*req = d;
293 	size_t		 len;
294 	ssize_t		 r;
295 	char		*buf, *e;
296 
297 	buf = req->buf + req->off;
298 	len = sizeof(req->buf) - req->off;
299 
300 	switch (r = tls_read(req->ctx, buf, len)) {
301 	case -1:
302 		e = xasprintf("tls_read: %s", tls_error(req->ctx));
303 		close_with_err(req, e);
304 		free(e);
305 		break;
306 	case TLS_WANT_POLLIN:
307 		yield_r(req, read_reply, NULL);
308 		break;
309 	case TLS_WANT_POLLOUT:
310 		yield_w(req, read_reply, NULL);
311 		break;
312 	default:
313 		req->off += r;
314 
315 		/* TODO: really watch for \r\n not \n alone */
316 		if ((e = telescope_strnchr(req->buf, '\n', req->off)) != NULL)
317 			parse_reply(req);
318 		else if (req->off == sizeof(req->buf))
319 			close_with_err(req, "invalid response");
320 		else
321 			yield_r(req, read_reply, NULL);
322 		break;
323 	}
324 }
325 
326 static void
327 parse_reply(struct req *req)
328 {
329 	int	 code;
330 	char	*e;
331 	size_t	 len;
332 
333 	if (req->off < 4)
334 		goto err;
335 
336 	if (!isdigit(req->buf[0]) || !isdigit(req->buf[1]))
337 		goto err;
338 
339 	code = (req->buf[0] - '0')*10 + (req->buf[1] - '0');
340 
341 	if (!isspace(req->buf[2]))
342 		goto err;
343 
344 	advance_buf(req, 3);
345 	if ((e = telescope_strnchr(req->buf, '\r', req->off)) == NULL)
346 		goto err;
347 
348 	*e = '\0';
349 	e++;
350 	len = e - req->buf;
351 	imsg_compose(ibuf, IMSG_GOT_CODE, req->id, 0, -1, &code, sizeof(code));
352 	imsg_compose(ibuf, IMSG_GOT_META, req->id, 0, -1,
353 	    req->buf, len);
354 	imsg_flush(ibuf);
355 
356 	if (code != 20)
357 		close_conn(0, 0, req);
358 
359 	return;
360 
361 err:
362 	close_with_err(req, "malformed request");
363 }
364 
365 static void
366 copy_body(int fd, short ev, void *d)
367 {
368 	struct req	*req = d;
369 	char		 buf[BUFSIZ];
370 	ssize_t		 r;
371 
372 	for (;;) {
373 		switch (r = tls_read(req->ctx, buf, sizeof(buf))) {
374 		case TLS_WANT_POLLIN:
375 			yield_r(req, copy_body, NULL);
376 			return;
377 		case TLS_WANT_POLLOUT:
378 			yield_w(req, copy_body, NULL);
379 			return;
380 		case -1:
381 		case 0:
382 			imsg_compose(ibuf, IMSG_EOF, req->id, 0, -1, NULL, 0);
383 			imsg_flush(ibuf);
384 			close_conn(0, 0, req);
385 			return;
386 		default:
387 			imsg_compose(ibuf, IMSG_BUF, req->id, 0, -1, buf, r);
388 			imsg_flush(ibuf);
389 			break;
390 		}
391 	}
392 }
393 
394 static void
395 handle_get(struct imsg *imsg, size_t datalen)
396 {
397 	struct req	*req;
398 	const char	*e;
399 	char		*data, *err = NULL;
400 
401 	data = imsg->data;
402 
403 	if (data[datalen-1] != '\0')
404 		die();
405 
406 	if ((req = calloc(1, sizeof(*req))) == NULL)
407 		die();
408 
409 	req->id = imsg->hdr.peerid;
410 
411         if (!url_parse(imsg->data, &req->url, &e)) {
412 		fprintf(stderr, "failed to parse url: %s\n", e);
413 		close_with_err(req, e);
414 		return;
415 	}
416 
417 	if ((req->fd = conn_towards(&req->url, &err)) == -1)
418 		goto err;
419 	if ((req->ctx = tls_client()) == NULL)
420 		goto err;
421 	if (tls_configure(req->ctx, tlsconf) == -1) {
422 		err = xasprintf("tls_configure: %s", tls_error(req->ctx));
423 		goto err;
424 	}
425 	if (tls_connect_socket(req->ctx, req->fd, req->url.host) == -1) {
426 		err = xasprintf("tls_connect_socket: %s", tls_error(req->ctx));
427 		goto err;
428 	}
429 
430 	TAILQ_INSERT_HEAD(&reqhead, req, reqs);
431 	yield_w(req, do_handshake, &timeout_for_handshake);
432 	return;
433 
434 err:
435         close_with_err(req, err);
436 	free(err);
437 }
438 
439 static void
440 handle_cert_status(struct imsg *imsg, size_t datalen)
441 {
442 	struct req	*req;
443 	int		 is_ok;
444 
445 	req = req_by_id(imsg->hdr.peerid);
446 
447 	if (datalen < sizeof(is_ok))
448 		die();
449 	memcpy(&is_ok, imsg->data, sizeof(is_ok));
450 
451 	if (is_ok)
452 		yield_w(req, write_request, NULL);
453 	else
454 		close_conn(0, 0, req);
455 }
456 
457 static void
458 handle_proceed(struct imsg *imsg, size_t datalen)
459 {
460 	struct req	*req;
461 
462 	req = req_by_id(imsg->hdr.peerid);
463 	yield_r(req, copy_body, NULL);
464 }
465 
466 static void
467 handle_stop(struct imsg *imsg, size_t datalen)
468 {
469 	struct req	*req;
470 
471 	req = req_by_id(imsg->hdr.peerid);
472 	close_conn(0, 0, req);
473 }
474 
475 static void
476 handle_quit(struct imsg *imsg, size_t datalen)
477 {
478 	event_loopbreak();
479 }
480 
481 static void
482 dispatch_imsg(int fd, short ev, void *d)
483 {
484 	struct imsgbuf	*ibuf = d;
485 	struct imsg	 imsg;
486 	ssize_t		 n;
487 	size_t		 datalen;
488 
489 	if ((n = imsg_read(ibuf)) == -1) {
490 		if (errno == EAGAIN || errno == EWOULDBLOCK)
491 			return;
492 		_exit(1);
493 	}
494 
495 	if (n == 0)
496 		_exit(1);
497 
498 	for (;;) {
499 		if ((n = imsg_get(ibuf, &imsg)) == -1)
500 			_exit(1);
501 		if (n == 0)
502 			return;
503 		datalen = imsg.hdr.len - IMSG_HEADER_SIZE;
504 		handlers[imsg.hdr.type](&imsg, datalen);
505 		imsg_free(&imsg);
506 	}
507 }
508 
509 int
510 client_main(struct imsgbuf *b)
511 {
512 	ibuf = b;
513 
514 	TAILQ_INIT(&reqhead);
515 
516 	if ((tlsconf = tls_config_new()) == NULL)
517 		die();
518 	tls_config_insecure_noverifycert(tlsconf);
519 
520 	event_init();
521 
522 	event_set(&imsgev, ibuf->fd, EV_READ | EV_PERSIST, dispatch_imsg, ibuf);
523 	event_add(&imsgev, NULL);
524 
525 	event_dispatch();
526 	return 0;
527 }