1 /*
2  * Copyright (c) 2022 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/queue.h>
18 #include <sys/tree.h>
19 #include <sys/socket.h>
20 
21 #include <netinet/in.h>
22 #include <arpa/inet.h>
23 
24 #include <errno.h>
25 #include <event.h>
26 #include <limits.h>
27 #include <stdarg.h>
28 #include <stdio.h>
29 #include <stdlib.h>
30 #include <stdint.h>
31 #include <string.h>
32 #include <unistd.h>
33 
34 #include "log.h"
35 
36 #include "galileo.h"
37 
38 #define MIN(a, b)	((a) < (b) ? (a) : (b))
39 
40 struct fcgi_header {
41 	unsigned char version;
42 	unsigned char type;
43 	unsigned char req_id1;
44 	unsigned char req_id0;
45 	unsigned char content_len1;
46 	unsigned char content_len0;
47 	unsigned char padding;
48 	unsigned char reserved;
49 } __attribute__((packed));
50 
51 /*
52  * number of bytes in a FCGI_HEADER.  Future version of the protocol
53  * will not reduce this number.
54  */
55 #define FCGI_HEADER_LEN	8
56 
57 /*
58  * values for the version component
59  */
60 #define FCGI_VERSION_1	1
61 
62 /*
63  * values for the type component
64  */
65 #define FCGI_BEGIN_REQUEST	 1
66 #define FCGI_ABORT_REQUEST	 2
67 #define FCGI_END_REQUEST	 3
68 #define FCGI_PARAMS		 4
69 #define FCGI_STDIN		 5
70 #define FCGI_STDOUT		 6
71 #define FCGI_STDERR		 7
72 #define FCGI_DATA		 8
73 #define FCGI_GET_VALUES		 9
74 #define FCGI_GET_VALUES_RESULT	10
75 #define FCGI_UNKNOWN_TYPE	11
76 #define FCGI_MAXTYPE		(FCGI_UNKNOWN_TYPE)
77 
78 struct fcgi_begin_req {
79 	unsigned char role1;
80 	unsigned char role0;
81 	unsigned char flags;
82 	unsigned char reserved[5];
83 };
84 
85 struct fcgi_begin_req_record {
86 	struct fcgi_header	header;
87 	struct fcgi_begin_req	body;
88 };
89 
90 /*
91  * mask for flags;
92  */
93 #define FCGI_KEEP_CONN		1
94 
95 /*
96  * values for the role
97  */
98 #define FCGI_RESPONDER	1
99 #define FCGI_AUTHORIZER	2
100 #define FCGI_FILTER	3
101 
102 struct fcgi_end_req_body {
103 	unsigned char app_status3;
104 	unsigned char app_status2;
105 	unsigned char app_status1;
106 	unsigned char app_status0;
107 	unsigned char proto_status;
108 	unsigned char reserved[3];
109 };
110 
111 /*
112  * values for proto_status
113  */
114 #define FCGI_REQUEST_COMPLETE	0
115 #define FCGI_CANT_MPX_CONN	1
116 #define FCGI_OVERLOADED		2
117 #define FCGI_UNKNOWN_ROLE	3
118 
119 /*
120  * Variable names for FCGI_GET_VALUES / FCGI_GET_VALUES_RESULT
121  * records.
122  */
123 #define FCGI_MAX_CONNS	"FCGI_MAX_CONNS"
124 #define FCGI_MAX_REQS	"FCGI_MAX_REQS"
125 #define FCGI_MPXS_CONNS	"FCGI_MPXS_CONNS"
126 
127 #define CAT(f0, f1)	((f0) + ((f1) << 8))
128 
129 enum {
130 	FCGI_RECORD_HEADER,
131 	FCGI_RECORD_BODY,
132 };
133 
134 volatile int fcgi_inflight;
135 
136 static int
137 fcgi_send_end_req(struct fcgi *fcgi, int id, int as, int ps)
138 {
139 	struct bufferevent	*bev = fcgi->fcg_bev;
140 	struct fcgi_header	 hdr;
141 	struct fcgi_end_req_body end;
142 
143 	memset(&hdr, 0, sizeof(hdr));
144 	memset(&end, 0, sizeof(end));
145 
146 	hdr.version = FCGI_VERSION_1;
147 	hdr.type = FCGI_END_REQUEST;
148 	hdr.req_id0 = (id & 0xFF);
149 	hdr.req_id1 = (id >> 8);
150 	hdr.content_len0 = sizeof(end);
151 
152 	end.app_status0 = (unsigned char)as;
153 	end.proto_status = (unsigned char)ps;
154 
155 	if (bufferevent_write(bev, &hdr, sizeof(hdr)) == -1)
156 		return (-1);
157 	if (bufferevent_write(bev, &end, sizeof(end)) == -1)
158 		return (-1);
159 	return (0);
160 }
161 
162 static int
163 end_request(struct client *clt, int status, int proto_status)
164 {
165 	struct fcgi		*fcgi = clt->clt_fcgi;
166 	int			 r;
167 
168 	if (clt_flush(clt) == -1)
169 		return (-1);
170 
171 	r = fcgi_send_end_req(fcgi, clt->clt_id, status,
172 	    proto_status);
173 	if (r == -1) {
174 		fcgi_error(fcgi->fcg_bev, EV_WRITE, fcgi);
175 		return (-1);
176 	}
177 
178 	SPLAY_REMOVE(client_tree, &fcgi->fcg_clients, clt);
179 	proxy_client_free(clt);
180 	return (0);
181 }
182 
183 int
184 fcgi_end_request(struct client *clt, int status)
185 {
186 	return (end_request(clt, status, FCGI_REQUEST_COMPLETE));
187 }
188 
189 int
190 fcgi_abort_request(struct client *clt)
191 {
192 	return (end_request(clt, 1, FCGI_OVERLOADED));
193 }
194 
195 static void
196 fcgi_inflight_dec(const char *why)
197 {
198 	fcgi_inflight--;
199 	log_debug("%s: fcgi inflight decremented, now %d, %s",
200 	    __func__, fcgi_inflight, why);
201 }
202 
203 void
204 fcgi_accept(int fd, short event, void *arg)
205 {
206 	struct galileo		*env = arg;
207 	struct fcgi		*fcgi = NULL;
208 	socklen_t		 slen;
209 	struct sockaddr_storage	 ss;
210 	int			 s = -1;
211 
212 	event_add(&env->sc_evpause, NULL);
213 	if ((event & EV_TIMEOUT))
214 		return;
215 
216 	slen = sizeof(ss);
217 	if ((s = accept_reserve(env->sc_sock_fd, (struct sockaddr *)&ss,
218 	    &slen, FD_RESERVE, &fcgi_inflight)) == -1) {
219 		/*
220 		 * Pause accept if we are out of file descriptors, or
221 		 * libevent will haunt us here too.
222 		 */
223 		if (errno == ENFILE || errno == EMFILE) {
224 			struct timeval evtpause = { 1, 0 };
225 
226 			event_del(&env->sc_evsock);
227 			evtimer_add(&env->sc_evpause, &evtpause);
228 			log_debug("%s: deferring connections", __func__);
229 		}
230 		return;
231 	}
232 
233 	if ((fcgi = calloc(1, sizeof(*fcgi))) == NULL)
234 		goto err;
235 
236 	fcgi->fcg_id = ++proxy_fcg_id;
237 	fcgi->fcg_s = s;
238 	fcgi->fcg_env = env;
239 	fcgi->fcg_want = FCGI_RECORD_HEADER;
240 	fcgi->fcg_toread = sizeof(struct fcgi_header);
241 	SPLAY_INIT(&fcgi->fcg_clients);
242 
243 	/* assume it's enabled until we get a FCGI_BEGIN_REQUEST */
244 	fcgi->fcg_keep_conn = 1;
245 
246 	fcgi->fcg_bev = bufferevent_new(fcgi->fcg_s, fcgi_read, fcgi_write,
247 	    fcgi_error, fcgi);
248 	if (fcgi->fcg_bev == NULL)
249 		goto err;
250 
251 	bufferevent_enable(fcgi->fcg_bev, EV_READ | EV_WRITE);
252 	return;
253 
254 err:
255 	if (s != -1) {
256 		close(s);
257 		free(fcgi);
258 		fcgi_inflight_dec(__func__);
259 	}
260 }
261 
262 static int
263 parse_len(struct fcgi *fcgi, struct evbuffer *src)
264 {
265 	unsigned char		 c, x[3];
266 
267 	fcgi->fcg_toread--;
268 	evbuffer_remove(src, &c, 1);
269 	if (c >> 7 == 0)
270 		return (c);
271 
272 	if (fcgi->fcg_toread < 3)
273 		return (-1);
274 
275 	fcgi->fcg_toread -= 3;
276 	evbuffer_remove(src, x, sizeof(x));
277 	return (((c & 0x7F) << 24) | (x[0] << 16) | (x[1] << 8) | x[2]);
278 }
279 
280 static int
281 fcgi_parse_params(struct fcgi *fcgi, struct evbuffer *src, struct client *clt)
282 {
283 	char			 pname[32];
284 	char			 server[HOST_NAME_MAX + 1];
285 	char			 path[PATH_MAX];
286 	int			 nlen, vlen;
287 
288 	while (fcgi->fcg_toread > 0) {
289 		if ((nlen = parse_len(fcgi, src)) < 0 ||
290 		    (vlen = parse_len(fcgi, src)) < 0)
291 			return (-1);
292 
293 		if (fcgi->fcg_toread < nlen + vlen)
294 			return (-1);
295 
296 		if ((size_t)nlen > sizeof(pname) - 1) {
297 			/* ignore this parameter */
298 			fcgi->fcg_toread -= nlen - vlen;
299 			evbuffer_drain(src, nlen + vlen);
300 			continue;
301 		}
302 
303 		fcgi->fcg_toread -= nlen;
304 		evbuffer_remove(src, &pname, nlen);
305 		pname[nlen] = '\0';
306 
307 		if (!strcmp(pname, "SERVER_NAME") &&
308 		    (size_t)vlen < sizeof(server)) {
309 			fcgi->fcg_toread -= vlen;
310 			evbuffer_remove(src, &server, vlen);
311 			server[vlen] = '\0';
312 
313 			if ((clt->clt_server_name = strdup(server)) == NULL)
314 				return (-1);
315 			log_debug("clt %d: server_name: %s", clt->clt_id,
316 			    clt->clt_server_name);
317 			continue;
318 		}
319 
320 		if (!strcmp(pname, "SCRIPT_NAME") &&
321 		    (size_t)vlen < sizeof(path)) {
322 			fcgi->fcg_toread -= vlen;
323 			evbuffer_remove(src, &path, vlen);
324 			path[vlen] = '\0';
325 
326 			if ((clt->clt_script_name = strdup(path)) == NULL)
327 				return (-1);
328 			log_debug("clt %d: script_name: %s", clt->clt_id,
329 			    clt->clt_script_name);
330 			continue;
331 		}
332 
333 		if (!strcmp(pname, "PATH_INFO") &&
334 		    (size_t)vlen < sizeof(path)) {
335 			fcgi->fcg_toread -= vlen;
336 			evbuffer_remove(src, &path, vlen);
337 			path[vlen] = '\0';
338 
339 			if ((clt->clt_path_info = strdup(path)) == NULL)
340 				return (-1);
341 			log_debug("clt %d: path_info: %s", clt->clt_id,
342 			    clt->clt_path_info);
343 			continue;
344 		}
345 
346 		fcgi->fcg_toread -= vlen;
347 		evbuffer_drain(src, vlen);
348 	}
349 
350 	return (0);
351 }
352 
353 void
354 fcgi_read(struct bufferevent *bev, void *d)
355 {
356 	struct fcgi		*fcgi = d;
357 	struct galileo		*env = fcgi->fcg_env;
358 	struct evbuffer		*src = EVBUFFER_INPUT(bev);
359 	struct fcgi_header	 hdr;
360 	struct fcgi_begin_req	 breq;
361 	struct client		*clt, q;
362 	int			 role;
363 
364 	memset(&q, 0, sizeof(q));
365 
366 	for (;;) {
367 		if (EVBUFFER_LENGTH(src) < (size_t)fcgi->fcg_toread)
368 			return;
369 
370 		if (fcgi->fcg_want == FCGI_RECORD_HEADER) {
371 			fcgi->fcg_want = FCGI_RECORD_BODY;
372 			bufferevent_read(bev, &hdr, sizeof(hdr));
373 
374 #ifdef DEBUG
375 			log_warnx("header: v=%d t=%d id=%d len=%d p=%d",
376 			    hdr.version, hdr.type,
377 			    CAT(hdr.req_id0, hdr.req_id1),
378 			    CAT(hdr.content_len0, hdr.content_len1),
379 			    hdr.padding);
380 #endif
381 
382 			if (hdr.version != FCGI_VERSION_1) {
383 				log_warnx("unknown fastcgi version: %d",
384 				    hdr.version);
385 				fcgi_error(bev, EV_READ, d);
386 				return;
387 			}
388 
389 			fcgi->fcg_toread = CAT(hdr.content_len0,
390 			    hdr.content_len1);
391 			if (fcgi->fcg_toread < 0) {
392 				log_warnx("invalid record length: %d",
393 				    fcgi->fcg_toread);
394 				fcgi_error(bev, EV_READ, d);
395 				return;
396 			}
397 
398 			fcgi->fcg_padding = hdr.padding;
399 			if (fcgi->fcg_padding < 0) {
400 				log_warnx("invalid padding: %d",
401 				    fcgi->fcg_padding);
402 				fcgi_error(bev, EV_READ, d);
403 				return;
404 			}
405 
406 			fcgi->fcg_type = hdr.type;
407 			fcgi->fcg_rec_id = CAT(hdr.req_id0, hdr.req_id1);
408 			continue;
409 		}
410 
411 		q.clt_id = fcgi->fcg_rec_id;
412 		clt = SPLAY_FIND(client_tree, &fcgi->fcg_clients, &q);
413 
414 		switch (fcgi->fcg_type) {
415 		case FCGI_BEGIN_REQUEST:
416 			if (sizeof(breq) != fcgi->fcg_toread) {
417 				log_warnx("unexpected size for "
418 				    "FCGI_BEGIN_REQUEST");
419 				fcgi_error(bev, EV_READ, d);
420 				return;
421 			}
422 
423 			evbuffer_remove(src, &breq, sizeof(breq));
424 
425 			role = CAT(breq.role0, breq.role1);
426 			if (role != FCGI_RESPONDER) {
427 				log_warnx("unknown fastcgi role: %d",
428 				    role);
429 				if (fcgi_send_end_req(fcgi, fcgi->fcg_rec_id,
430 				    1, FCGI_UNKNOWN_ROLE) == -1) {
431 					fcgi_error(bev, EV_READ, d);
432 					return;
433 				}
434 				break;
435 			}
436 
437 			if (!fcgi->fcg_keep_conn) {
438 				log_warnx("trying to reuse the fastcgi "
439 				    "socket without marking it as so.");
440 				fcgi_error(bev, EV_READ, d);
441 				return;
442 			}
443 			fcgi->fcg_keep_conn = breq.flags & FCGI_KEEP_CONN;
444 
445 			if (clt != NULL) {
446 				log_warnx("ignoring attemp to re-use an "
447 				    "active request id (%d)",
448 				    fcgi->fcg_rec_id);
449 				break;
450 			}
451 
452 			if ((clt = calloc(1, sizeof(*clt))) == NULL) {
453 				log_warnx("calloc");
454 				break;
455 			}
456 
457 			clt->clt_id = fcgi->fcg_rec_id;
458 			clt->clt_fd = -1;
459 			clt->clt_fcgi = fcgi;
460 			SPLAY_INSERT(client_tree, &fcgi->fcg_clients, clt);
461 			break;
462 		case FCGI_PARAMS:
463 			if (clt == NULL) {
464 				log_warnx("got FCGI_PARAMS for inactive id "
465 				    "(%d)", fcgi->fcg_rec_id);
466 				evbuffer_drain(src, fcgi->fcg_toread);
467 				break;
468 			}
469 			if (fcgi->fcg_toread == 0) {
470 				evbuffer_drain(src, fcgi->fcg_toread);
471 				proxy_start_request(env, clt);
472 				break;
473 			}
474 			if (fcgi_parse_params(fcgi, src, clt) == -1) {
475 				log_warnx("fcgi_parse_params failed");
476 				fcgi_error(bev, EV_READ, d);
477 				return;
478 			}
479 			break;
480 		case FCGI_STDIN:
481 			/* ignore */
482 			evbuffer_drain(src, fcgi->fcg_toread);
483 			break;
484 		case FCGI_ABORT_REQUEST:
485 			if (clt == NULL) {
486 				log_warnx("got FCGI_ABORT_REQUEST for inactive"
487 				    " id (%d)", fcgi->fcg_rec_id);
488 				evbuffer_drain(src, fcgi->fcg_toread);
489 				break;
490 			}
491 			if (fcgi_end_request(clt, 1) == -1) {
492 				/* calls fcgi_error on failure */
493 				return;
494 			}
495 			break;
496 		default:
497 			log_warnx("unknown fastcgi record type %d",
498 			    fcgi->fcg_type);
499 			evbuffer_drain(src, fcgi->fcg_toread);
500 			break;
501 		}
502 
503 		/* Prepare for the next record. */
504 		evbuffer_drain(src, fcgi->fcg_padding);
505 		fcgi->fcg_want = FCGI_RECORD_HEADER;
506 		fcgi->fcg_toread = sizeof(struct fcgi_header);
507 	}
508 }
509 
510 void
511 fcgi_write(struct bufferevent *bev, void *d)
512 {
513 	struct fcgi		*fcgi = d;
514 
515 	(void)fcgi;
516 }
517 
518 void
519 fcgi_error(struct bufferevent *bev, short event, void *d)
520 {
521 	struct fcgi		*fcgi = d;
522 	struct galileo		*env = fcgi->fcg_env;
523 	struct client		*clt;
524 
525 	log_debug("fcgi failure, shutting down connection (ev: %x)",
526 	    event);
527 	fcgi_inflight_dec(__func__);
528 
529 	while ((clt = SPLAY_MIN(client_tree, &fcgi->fcg_clients)) != NULL) {
530 		SPLAY_REMOVE(client_tree, &fcgi->fcg_clients, clt);
531 		proxy_client_free(clt);
532 	}
533 
534 	close(fcgi->fcg_s);
535 	bufferevent_free(fcgi->fcg_bev);
536 	SPLAY_REMOVE(fcgi_tree, &env->sc_fcgi_socks, fcgi);
537 	free(fcgi);
538 
539 	return;
540 }
541 
542 int
543 clt_flush(struct client *clt)
544 {
545 	struct fcgi		*fcgi = clt->clt_fcgi;
546 	struct bufferevent	*bev = fcgi->fcg_bev;
547 	struct fcgi_header	 hdr;
548 
549 	if (clt->clt_buflen == 0)
550 		return (0);
551 
552 	memset(&hdr, 0, sizeof(hdr));
553 	hdr.version = FCGI_VERSION_1;
554 	hdr.type = FCGI_STDOUT;
555 	hdr.req_id0 = (clt->clt_id & 0xFF);
556 	hdr.req_id1 = (clt->clt_id >> 8);
557 	hdr.content_len0 = (clt->clt_buflen & 0xFF);
558 	hdr.content_len1 = (clt->clt_buflen >> 8);
559 
560 	if (bufferevent_write(bev, &hdr, sizeof(hdr)) == -1 ||
561 	    bufferevent_write(bev, clt->clt_buf, clt->clt_buflen) == -1) {
562 		fcgi_error(bev, EV_WRITE, fcgi);
563 		return (-1);
564 	}
565 
566 	clt->clt_buflen = 0;
567 
568 	return (0);
569 }
570 
571 int
572 clt_write(struct client *clt, const uint8_t *buf, size_t len)
573 {
574 	size_t			 left, copy;
575 
576 	while (len > 0) {
577 		left = sizeof(clt->clt_buf) - clt->clt_buflen;
578 		if (left == 0) {
579 			if (clt_flush(clt) == -1)
580 				return (-1);
581 			left = sizeof(clt->clt_buf);
582 		}
583 
584 		copy = MIN(left, len);
585 
586 		memcpy(&clt->clt_buf[clt->clt_buflen], buf, copy);
587 		clt->clt_buflen += copy;
588 		buf += copy;
589 		len -= copy;
590 	}
591 
592 	return (0);
593 }
594 
595 int
596 clt_write_bufferevent(struct client *clt, struct bufferevent *bev)
597 {
598 	struct evbuffer		*src = EVBUFFER_INPUT(bev);
599 	size_t			 len, left, copy;
600 
601 	len = EVBUFFER_LENGTH(src);
602 	while (len > 0) {
603 		left = sizeof(clt->clt_buf) - clt->clt_buflen;
604 		if (left == 0) {
605 			if (clt_flush(clt) == -1)
606 				return (-1);
607 			left = sizeof(clt->clt_buf);
608 		}
609 
610 		copy = bufferevent_read(bev, &clt->clt_buf[clt->clt_buflen],
611 		    MIN(left, len));
612 		clt->clt_buflen += copy;
613 
614 		len = EVBUFFER_LENGTH(src);
615 	}
616 
617 	return (0);
618 }
619 
620 int
621 clt_printf(struct client *clt, const char *fmt, ...)
622 {
623 	struct fcgi		*fcgi = clt->clt_fcgi;
624 	struct bufferevent	*bev = fcgi->fcg_bev;
625 	char			*str;
626 	va_list			 ap;
627 	int			 r;
628 
629 	va_start(ap, fmt);
630 	r = vasprintf(&str, fmt, ap);
631 	va_end(ap);
632 	if (r == -1) {
633 		fcgi_error(bev, EV_WRITE, fcgi);
634 		return (-1);
635 	}
636 
637 	r = clt_write(clt, str, r);
638 	free(str);
639 	return (r);
640 }
641 
642 int
643 fcgi_cmp(struct fcgi *a, struct fcgi *b)
644 {
645 	return ((int)a->fcg_id - b->fcg_id);
646 }
647 
648 int
649 fcgi_client_cmp(struct client *a, struct client *b)
650 {
651 	return ((int)a->clt_id - b->clt_id);
652 }
653 
654 SPLAY_GENERATE(fcgi_tree, fcgi, fcg_nodes, fcgi_cmp);
655 SPLAY_GENERATE(client_tree, client, clt_nodes, fcgi_client_cmp);
656