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