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 <netdb.h>
36 #include <stdarg.h>
37 #include <stdio.h>
38 #include <stdlib.h>
39 #include <string.h>
40 #include <tls.h>
41 #include <unistd.h>
42 
43 static struct event		 imsgev;
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 static struct req	*req_by_id_try(uint32_t);
56 
57 static void		 do_handshake(int, short, void*);
58 static void		 write_request(int, short, void*);
59 static void		 read_reply(int, short, void*);
60 static void		 parse_reply(struct req*);
61 static void		 copy_body(int, short, void*);
62 
63 static void		 handle_get(struct imsg*, size_t);
64 static void		 handle_cert_status(struct imsg*, size_t);
65 static void		 handle_proceed(struct imsg*, size_t);
66 static void		 handle_stop(struct imsg*, size_t);
67 static void		 handle_quit(struct imsg*, size_t);
68 
69 /* TODO: making this customizable */
70 struct timeval timeout_for_handshake = { 5, 0 };
71 
72 static imsg_handlerfn *handlers[] = {
73 	[IMSG_GET] = handle_get,
74 	[IMSG_CERT_STATUS] = handle_cert_status,
75 	[IMSG_PROCEED] = handle_proceed,
76 	[IMSG_STOP] = handle_stop,
77 	[IMSG_QUIT] = handle_quit,
78 };
79 
80 typedef void (*statefn)(int, short, void*);
81 
82 TAILQ_HEAD(, req) reqhead;
83 /* a pending request */
84 struct req {
85 	struct event		 ev;
86 	struct url		 url;
87 	uint32_t		 id;
88 	int			 fd;
89 	struct tls		*ctx;
90 	char			 buf[1024];
91 	size_t			 off;
92 	TAILQ_ENTRY(req)	 reqs;
93 };
94 
95 static inline void
96 yield_r(struct req *req, statefn fn, struct timeval *tv)
97 {
98 	event_once(req->fd, EV_READ, fn, req, tv);
99 }
100 
101 static inline void
102 yield_w(struct req *req, statefn fn, struct timeval *tv)
103 {
104 	event_once(req->fd, EV_WRITE, fn, req, tv);
105 }
106 
107 static inline void
108 advance_buf(struct req *req, size_t len)
109 {
110 	assert(len <= req->off);
111 
112 	req->off -= len;
113 	memmove(req->buf, req->buf + len, req->off);
114 }
115 
116 static void __attribute__((__noreturn__))
117 die(void)
118 {
119 	abort(); 		/* TODO */
120 }
121 
122 static char *
123 xasprintf(const char *fmt, ...)
124 {
125 	va_list ap;
126 	char *s;
127 
128 	va_start(ap, fmt);
129 	if (vasprintf(&s, fmt, ap) == -1)
130 		s = NULL;
131 	va_end(ap);
132 
133 	return s;
134 }
135 
136 static int
137 conn_towards(struct url *url, char **err)
138 {
139 	struct addrinfo	 hints, *servinfo, *p;
140 	int		 status, sock;
141 	const char	*proto = "1965";
142 
143 	*err = NULL;
144 
145 	if (*url->port != '\0')
146 		proto = url->port;
147 
148 	memset(&hints, 0, sizeof(hints));
149 	hints.ai_family = AF_UNSPEC;
150 	hints.ai_socktype = SOCK_STREAM;
151 
152 	if ((status = getaddrinfo(url->host, proto, &hints, &servinfo))) {
153 		*err = xasprintf("failed to resolve %s: %s",
154 		    url->host, gai_strerror(status));
155 		return -1;
156 	}
157 
158 	sock = -1;
159 	for (p = servinfo; p != NULL; p = p->ai_next) {
160 		if ((sock = socket(p->ai_family, p->ai_socktype, p->ai_protocol)) == -1)
161 			continue;
162 		if (connect(sock, p->ai_addr, p->ai_addrlen) != -1)
163 			break;
164 		close(sock);
165 	}
166 
167 	if (sock == -1)
168 		*err = xasprintf("couldn't connect to %s", url->host);
169 	else
170 		mark_nonblock(sock);
171 
172 	freeaddrinfo(servinfo);
173 	return sock;
174 }
175 
176 static struct req *
177 req_by_id(uint32_t id)
178 {
179 	struct req *r;
180 
181 	if ((r = req_by_id_try(id)) == NULL)
182 		die();
183 	return r;
184 }
185 
186 static struct req *
187 req_by_id_try(uint32_t id)
188 {
189 	struct req *r;
190 
191 	TAILQ_FOREACH(r, &reqhead, reqs) {
192 		if (r->id == id)
193 			return r;
194 	}
195 
196 	return NULL;
197 }
198 
199 static void
200 close_conn(int fd, short ev, void *d)
201 {
202 	struct req	*req = d;
203 
204 	if (req->ctx != NULL) {
205 		switch (tls_close(req->ctx)) {
206 		case TLS_WANT_POLLIN:
207 			yield_r(req, close_conn, NULL);
208 			return;
209 		case TLS_WANT_POLLOUT:
210 			yield_w(req, close_conn, NULL);
211 			return;
212 		}
213 
214 		tls_free(req->ctx);
215 	}
216 
217 	TAILQ_REMOVE(&reqhead, req, reqs);
218 	if (req->fd != -1)
219 		close(req->fd);
220 	free(req);
221 }
222 
223 static void
224 close_with_err(struct req *req, const char *err)
225 {
226 	imsg_compose(ibuf, IMSG_ERR, req->id, 0, -1, err, strlen(err)+1);
227 	imsg_flush(ibuf);
228 	close_conn(0, 0, req);
229 }
230 
231 static void
232 do_handshake(int fd, short ev, void *d)
233 {
234 	struct req	*req = d;
235 	const char	*hash;
236 
237 	if (ev == EV_TIMEOUT) {
238 		close_with_err(req, "Timeout loading page");
239 		return;
240 	}
241 
242 	switch (tls_handshake(req->ctx)) {
243 	case TLS_WANT_POLLIN:
244 		yield_r(req, do_handshake, NULL);
245 		return;
246 	case TLS_WANT_POLLOUT:
247 		yield_w(req, do_handshake, NULL);
248 		return;
249 	}
250 
251 	hash = tls_peer_cert_hash(req->ctx);
252 	imsg_compose(ibuf, IMSG_CHECK_CERT, req->id, 0, -1, hash, strlen(hash)+1);
253 	imsg_flush(ibuf);
254 }
255 
256 static void
257 write_request(int fd, short ev, void *d)
258 {
259 	struct req	*req = d;
260 	ssize_t		 r;
261 	size_t		 len;
262 	char		 buf[1024], *err;
263 
264 	strlcpy(buf, "gemini://", sizeof(buf));
265 	strlcat(buf, req->url.host, sizeof(buf));
266 	strlcat(buf, "/", sizeof(buf));
267 	strlcat(buf, req->url.path, sizeof(buf));
268 
269 	if (req->url.query[0] != '\0') {
270 		strlcat(buf, "?", sizeof(buf));
271 		strlcat(buf, req->url.query, sizeof(buf));
272 	}
273 
274 	len = strlcat(buf, "\r\n", sizeof(buf));
275 
276 	assert(len <= sizeof(buf));
277 
278 	switch (r = tls_write(req->ctx, buf, len)) {
279 	case -1:
280 		err = xasprintf("tls_write: %s", tls_error(req->ctx));
281 		close_with_err(req, err);
282 		free(err);
283 		break;
284 	case TLS_WANT_POLLIN:
285 		yield_r(req, write_request, NULL);
286 		break;
287 	case TLS_WANT_POLLOUT:
288 		yield_w(req, write_request, NULL);
289 		break;
290 	default:
291 		/* assume r == len */
292 		(void)r;
293 		yield_r(req, read_reply, NULL);
294 		break;
295 	}
296 }
297 
298 static void
299 read_reply(int fd, short ev, void *d)
300 {
301 	struct req	*req = d;
302 	size_t		 len;
303 	ssize_t		 r;
304 	char		*buf, *e;
305 
306 	buf = req->buf + req->off;
307 	len = sizeof(req->buf) - req->off;
308 
309 	switch (r = tls_read(req->ctx, buf, len)) {
310 	case -1:
311 		e = xasprintf("tls_read: %s", tls_error(req->ctx));
312 		close_with_err(req, e);
313 		free(e);
314 		break;
315 	case TLS_WANT_POLLIN:
316 		yield_r(req, read_reply, NULL);
317 		break;
318 	case TLS_WANT_POLLOUT:
319 		yield_w(req, read_reply, NULL);
320 		break;
321 	default:
322 		req->off += r;
323 
324 		/* TODO: really watch for \r\n not \n alone */
325 		if ((e = telescope_strnchr(req->buf, '\n', req->off)) != NULL)
326 			parse_reply(req);
327 		else if (req->off == sizeof(req->buf))
328 			close_with_err(req, "invalid response");
329 		else
330 			yield_r(req, read_reply, NULL);
331 		break;
332 	}
333 }
334 
335 static void
336 parse_reply(struct req *req)
337 {
338 	int	 code;
339 	char	*e;
340 	size_t	 len;
341 
342 	if (req->off < 4)
343 		goto err;
344 
345 	if (!isdigit(req->buf[0]) || !isdigit(req->buf[1]))
346 		goto err;
347 
348 	code = (req->buf[0] - '0')*10 + (req->buf[1] - '0');
349 
350 	if (!isspace(req->buf[2]))
351 		goto err;
352 
353 	advance_buf(req, 3);
354 	if ((e = telescope_strnchr(req->buf, '\r', req->off)) == NULL)
355 		goto err;
356 
357 	*e = '\0';
358 	e++;
359 	len = e - req->buf;
360 	imsg_compose(ibuf, IMSG_GOT_CODE, req->id, 0, -1, &code, sizeof(code));
361 	imsg_compose(ibuf, IMSG_GOT_META, req->id, 0, -1,
362 	    req->buf, len);
363 	imsg_flush(ibuf);
364 
365 	if (code != 20)
366 		close_conn(0, 0, req);
367 	advance_buf(req, len+1); /* skip \n too */
368 
369 	return;
370 
371 err:
372 	close_with_err(req, "malformed request");
373 }
374 
375 static void
376 copy_body(int fd, short ev, void *d)
377 {
378 	struct req	*req = d;
379 	ssize_t		 r;
380 
381 	for (;;) {
382 		if (req->off != 0) {
383 			imsg_compose(ibuf, IMSG_BUF, req->id, 0, -1,
384 			    req->buf, req->off);
385 			imsg_flush(ibuf);
386 			req->off = 0;
387 		}
388 
389 		switch (r = tls_read(req->ctx, req->buf, sizeof(req->buf))) {
390 		case TLS_WANT_POLLIN:
391 			yield_r(req, copy_body, NULL);
392 			return;
393 		case TLS_WANT_POLLOUT:
394 			yield_w(req, copy_body, NULL);
395 			return;
396 		case 0:
397 			imsg_compose(ibuf, IMSG_EOF, req->id, 0, -1, NULL, 0);
398 			imsg_flush(ibuf);
399 			close_conn(0, 0, req);
400 			return;
401 		default:
402 			req->off = r;
403 		}
404 	}
405 }
406 
407 static void
408 handle_get(struct imsg *imsg, size_t datalen)
409 {
410 	struct req	*req;
411 	const char	*e;
412 	char		*data, *err = NULL;
413 
414 	data = imsg->data;
415 
416 	if (data[datalen-1] != '\0')
417 		die();
418 
419 	if ((req = calloc(1, sizeof(*req))) == NULL)
420 		die();
421 
422 	req->id = imsg->hdr.peerid;
423 	TAILQ_INSERT_HEAD(&reqhead, req, reqs);
424 
425         if (!url_parse(imsg->data, &req->url, &e)) {
426 		close_with_err(req, e);
427 		return;
428 	}
429 
430 	if ((req->fd = conn_towards(&req->url, &err)) == -1)
431 		goto err;
432 	if ((req->ctx = tls_client()) == NULL)
433 		goto err;
434 	if (tls_configure(req->ctx, tlsconf) == -1) {
435 		err = xasprintf("tls_configure: %s", tls_error(req->ctx));
436 		goto err;
437 	}
438 	if (tls_connect_socket(req->ctx, req->fd, req->url.host) == -1) {
439 		err = xasprintf("tls_connect_socket: %s", tls_error(req->ctx));
440 		goto err;
441 	}
442 
443 	yield_w(req, do_handshake, &timeout_for_handshake);
444 	return;
445 
446 err:
447         close_with_err(req, err);
448 	free(err);
449 }
450 
451 static void
452 handle_cert_status(struct imsg *imsg, size_t datalen)
453 {
454 	struct req	*req;
455 	int		 is_ok;
456 
457 	req = req_by_id(imsg->hdr.peerid);
458 
459 	if (datalen < sizeof(is_ok))
460 		die();
461 	memcpy(&is_ok, imsg->data, sizeof(is_ok));
462 
463 	if (is_ok)
464 		yield_w(req, write_request, NULL);
465 	else
466 		close_conn(0, 0, req);
467 }
468 
469 static void
470 handle_proceed(struct imsg *imsg, size_t datalen)
471 {
472 	yield_r(req_by_id(imsg->hdr.peerid),
473 	    copy_body, NULL);
474 }
475 
476 static void
477 handle_stop(struct imsg *imsg, size_t datalen)
478 {
479 	struct req	*req;
480 
481 	if ((req = req_by_id_try(imsg->hdr.peerid)) == NULL)
482 		return;
483 	close_conn(0, 0, req);
484 }
485 
486 static void
487 handle_quit(struct imsg *imsg, size_t datalen)
488 {
489 	event_loopbreak();
490 }
491 
492 static void
493 dispatch_imsg(int fd, short ev, void *d)
494 {
495 	struct imsgbuf	*ibuf = d;
496 	struct imsg	 imsg;
497 	ssize_t		 n;
498 	size_t		 datalen;
499 
500 	if ((n = imsg_read(ibuf)) == -1) {
501 		if (errno == EAGAIN || errno == EWOULDBLOCK)
502 			return;
503 		_exit(1);
504 	}
505 
506 	if (n == 0)
507 		_exit(1);
508 
509 	for (;;) {
510 		if ((n = imsg_get(ibuf, &imsg)) == -1)
511 			_exit(1);
512 		if (n == 0)
513 			return;
514 		datalen = imsg.hdr.len - IMSG_HEADER_SIZE;
515 		handlers[imsg.hdr.type](&imsg, datalen);
516 		imsg_free(&imsg);
517 	}
518 }
519 
520 int
521 client_main(struct imsgbuf *b)
522 {
523 	ibuf = b;
524 
525 	TAILQ_INIT(&reqhead);
526 
527 	if ((tlsconf = tls_config_new()) == NULL)
528 		die();
529 	tls_config_insecure_noverifycert(tlsconf);
530 
531 	event_init();
532 
533 	event_set(&imsgev, ibuf->fd, EV_READ | EV_PERSIST, dispatch_imsg, ibuf);
534 	event_add(&imsgev, NULL);
535 
536 	sandbox_network_process();
537 
538 	event_dispatch();
539 	return 0;
540 }