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 static void		 handle_dispatch_imsg(int, short, void*);
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 	if ((r = req_by_id_try(id)) == NULL)
183 		die();
184 	return r;
185 }
186 
187 static struct req *
188 req_by_id_try(uint32_t id)
189 {
190 	struct req *r;
191 
192 	TAILQ_FOREACH(r, &reqhead, reqs) {
193 		if (r->id == id)
194 			return r;
195 	}
196 
197 	return NULL;
198 }
199 
200 static void
201 close_conn(int fd, short ev, void *d)
202 {
203 	struct req	*req = d;
204 
205 	if (req->ctx != NULL) {
206 		switch (tls_close(req->ctx)) {
207 		case TLS_WANT_POLLIN:
208 			yield_r(req, close_conn, NULL);
209 			return;
210 		case TLS_WANT_POLLOUT:
211 			yield_w(req, close_conn, NULL);
212 			return;
213 		}
214 
215 		tls_free(req->ctx);
216 	}
217 
218 	TAILQ_REMOVE(&reqhead, req, reqs);
219 	if (req->fd != -1)
220 		close(req->fd);
221 	free(req);
222 }
223 
224 static void
225 close_with_err(struct req *req, const char *err)
226 {
227 	imsg_compose(ibuf, IMSG_ERR, req->id, 0, -1, err, strlen(err)+1);
228 	imsg_flush(ibuf);
229 	close_conn(0, 0, req);
230 }
231 
232 static void
233 do_handshake(int fd, short ev, void *d)
234 {
235 	struct req	*req = d;
236 	const char	*hash;
237 
238 	if (ev == EV_TIMEOUT) {
239 		close_with_err(req, "Timeout loading page");
240 		return;
241 	}
242 
243 	switch (tls_handshake(req->ctx)) {
244 	case TLS_WANT_POLLIN:
245 		yield_r(req, do_handshake, NULL);
246 		return;
247 	case TLS_WANT_POLLOUT:
248 		yield_w(req, do_handshake, NULL);
249 		return;
250 	}
251 
252 	hash = tls_peer_cert_hash(req->ctx);
253 	imsg_compose(ibuf, IMSG_CHECK_CERT, req->id, 0, -1, hash, strlen(hash)+1);
254 	imsg_flush(ibuf);
255 }
256 
257 static void
258 write_request(int fd, short ev, void *d)
259 {
260 	struct req	*req = d;
261 	ssize_t		 r;
262 	size_t		 len;
263 	char		 buf[1024], *err;
264 
265 	strlcpy(buf, "gemini://", sizeof(buf));
266 	strlcat(buf, req->url.host, sizeof(buf));
267 	strlcat(buf, "/", sizeof(buf));
268 	strlcat(buf, req->url.path, sizeof(buf));
269 
270 	if (req->url.query[0] != '\0') {
271 		strlcat(buf, "?", sizeof(buf));
272 		strlcat(buf, req->url.query, sizeof(buf));
273 	}
274 
275 	len = strlcat(buf, "\r\n", sizeof(buf));
276 
277 	assert(len <= sizeof(buf));
278 
279 	switch (r = tls_write(req->ctx, buf, len)) {
280 	case -1:
281 		err = xasprintf("tls_write: %s", tls_error(req->ctx));
282 		close_with_err(req, err);
283 		free(err);
284 		break;
285 	case TLS_WANT_POLLIN:
286 		yield_r(req, write_request, NULL);
287 		break;
288 	case TLS_WANT_POLLOUT:
289 		yield_w(req, write_request, NULL);
290 		break;
291 	default:
292 		/* assume r == len */
293 		(void)r;
294 		yield_r(req, read_reply, NULL);
295 		break;
296 	}
297 }
298 
299 static void
300 read_reply(int fd, short ev, void *d)
301 {
302 	struct req	*req = d;
303 	size_t		 len;
304 	ssize_t		 r;
305 	char		*buf, *e;
306 
307 	buf = req->buf + req->off;
308 	len = sizeof(req->buf) - req->off;
309 
310 	switch (r = tls_read(req->ctx, buf, len)) {
311 	case -1:
312 		e = xasprintf("tls_read: %s", tls_error(req->ctx));
313 		close_with_err(req, e);
314 		free(e);
315 		break;
316 	case TLS_WANT_POLLIN:
317 		yield_r(req, read_reply, NULL);
318 		break;
319 	case TLS_WANT_POLLOUT:
320 		yield_w(req, read_reply, NULL);
321 		break;
322 	default:
323 		req->off += r;
324 
325 		/* TODO: really watch for \r\n not \n alone */
326 		if ((e = telescope_strnchr(req->buf, '\n', req->off)) != NULL)
327 			parse_reply(req);
328 		else if (req->off == sizeof(req->buf))
329 			close_with_err(req, "invalid response");
330 		else
331 			yield_r(req, read_reply, NULL);
332 		break;
333 	}
334 }
335 
336 static void
337 parse_reply(struct req *req)
338 {
339 	int	 code;
340 	char	*e;
341 	size_t	 len;
342 
343 	if (req->off < 4)
344 		goto err;
345 
346 	if (!isdigit(req->buf[0]) || !isdigit(req->buf[1]))
347 		goto err;
348 
349 	code = (req->buf[0] - '0')*10 + (req->buf[1] - '0');
350 
351 	if (!isspace(req->buf[2]))
352 		goto err;
353 
354 	advance_buf(req, 3);
355 	if ((e = telescope_strnchr(req->buf, '\r', req->off)) == NULL)
356 		goto err;
357 
358 	*e = '\0';
359 	e++;
360 	len = e - req->buf;
361 	imsg_compose(ibuf, IMSG_GOT_CODE, req->id, 0, -1, &code, sizeof(code));
362 	imsg_compose(ibuf, IMSG_GOT_META, req->id, 0, -1,
363 	    req->buf, len);
364 	imsg_flush(ibuf);
365 
366 	if (code != 20)
367 		close_conn(0, 0, req);
368 	advance_buf(req, len+1); /* skip \n too */
369 
370 	return;
371 
372 err:
373 	close_with_err(req, "malformed request");
374 }
375 
376 static void
377 copy_body(int fd, short ev, void *d)
378 {
379 	struct req	*req = d;
380 	ssize_t		 r;
381 
382 	for (;;) {
383 		if (req->off != 0) {
384 			imsg_compose(ibuf, IMSG_BUF, req->id, 0, -1,
385 			    req->buf, req->off);
386 			imsg_flush(ibuf);
387 			req->off = 0;
388 		}
389 
390 		switch (r = tls_read(req->ctx, req->buf, sizeof(req->buf))) {
391 		case TLS_WANT_POLLIN:
392 			yield_r(req, copy_body, NULL);
393 			return;
394 		case TLS_WANT_POLLOUT:
395 			yield_w(req, copy_body, NULL);
396 			return;
397 		case 0:
398 			imsg_compose(ibuf, IMSG_EOF, req->id, 0, -1, NULL, 0);
399 			imsg_flush(ibuf);
400 			close_conn(0, 0, req);
401 			return;
402 		default:
403 			req->off = r;
404 		}
405 	}
406 }
407 
408 static void
409 handle_get(struct imsg *imsg, size_t datalen)
410 {
411 	struct req	*req;
412 	const char	*e;
413 	char		*data, *err = NULL;
414 
415 	data = imsg->data;
416 
417 	if (data[datalen-1] != '\0')
418 		die();
419 
420 	if ((req = calloc(1, sizeof(*req))) == NULL)
421 		die();
422 
423 	req->id = imsg->hdr.peerid;
424 	TAILQ_INSERT_HEAD(&reqhead, req, reqs);
425 
426         if (!url_parse(imsg->data, &req->url, &e)) {
427 		close_with_err(req, e);
428 		return;
429 	}
430 
431 	if ((req->fd = conn_towards(&req->url, &err)) == -1)
432 		goto err;
433 	if ((req->ctx = tls_client()) == NULL)
434 		goto err;
435 	if (tls_configure(req->ctx, tlsconf) == -1) {
436 		err = xasprintf("tls_configure: %s", tls_error(req->ctx));
437 		goto err;
438 	}
439 	if (tls_connect_socket(req->ctx, req->fd, req->url.host) == -1) {
440 		err = xasprintf("tls_connect_socket: %s", tls_error(req->ctx));
441 		goto err;
442 	}
443 
444 	yield_w(req, do_handshake, &timeout_for_handshake);
445 	return;
446 
447 err:
448         close_with_err(req, err);
449 	free(err);
450 }
451 
452 static void
453 handle_cert_status(struct imsg *imsg, size_t datalen)
454 {
455 	struct req	*req;
456 	int		 is_ok;
457 
458 	req = req_by_id(imsg->hdr.peerid);
459 
460 	if (datalen < sizeof(is_ok))
461 		die();
462 	memcpy(&is_ok, imsg->data, sizeof(is_ok));
463 
464 	if (is_ok)
465 		yield_w(req, write_request, NULL);
466 	else
467 		close_conn(0, 0, req);
468 }
469 
470 static void
471 handle_proceed(struct imsg *imsg, size_t datalen)
472 {
473 	yield_r(req_by_id(imsg->hdr.peerid),
474 	    copy_body, NULL);
475 }
476 
477 static void
478 handle_stop(struct imsg *imsg, size_t datalen)
479 {
480 	struct req	*req;
481 
482 	if ((req = req_by_id_try(imsg->hdr.peerid)) == NULL)
483 		return;
484 	close_conn(0, 0, req);
485 }
486 
487 static void
488 handle_quit(struct imsg *imsg, size_t datalen)
489 {
490 	event_loopbreak();
491 }
492 
493 static void
494 handle_dispatch_imsg(int fd, short ev, void *d)
495 {
496 	struct imsgbuf	*ibuf = d;
497 	dispatch_imsg(ibuf, handlers, sizeof(handlers));
498 }
499 
500 int
501 client_main(struct imsgbuf *b)
502 {
503 	ibuf = b;
504 
505 	TAILQ_INIT(&reqhead);
506 
507 	if ((tlsconf = tls_config_new()) == NULL)
508 		die();
509 	tls_config_insecure_noverifycert(tlsconf);
510 
511 	event_init();
512 
513 	event_set(&imsgev, ibuf->fd, EV_READ | EV_PERSIST, handle_dispatch_imsg, ibuf);
514 	event_add(&imsgev, NULL);
515 
516 	sandbox_network_process();
517 
518 	event_dispatch();
519 	return 0;
520 }