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(struct galileo *env)
205 {
206 	struct fcgi		*fcgi = NULL;
207 	socklen_t		 slen;
208 	struct sockaddr_storage	 ss;
209 	int			 s = -1;
210 
211 	slen = sizeof(ss);
212 	if ((s = accept_reserve(env->sc_sock_fd, (struct sockaddr *)&ss,
213 	    &slen, FD_RESERVE, &fcgi_inflight)) == -1) {
214 		/*
215 		 * Pause accept if we are out of file descriptors, or
216 		 * libevent will haunt us here too.
217 		 */
218 		if (errno == ENFILE || errno == EMFILE) {
219 			struct timeval evtpause = { 1, 0 };
220 
221 			event_del(&env->sc_evsock);
222 			evtimer_add(&env->sc_evpause, &evtpause);
223 			log_debug("%s: deferring connections", __func__);
224 		}
225 		return;
226 	}
227 
228 	if ((fcgi = calloc(1, sizeof(*fcgi))) == NULL)
229 		goto err;
230 
231 	fcgi->fcg_id = ++proxy_fcg_id;
232 	fcgi->fcg_s = s;
233 	fcgi->fcg_env = env;
234 	fcgi->fcg_want = FCGI_RECORD_HEADER;
235 	fcgi->fcg_toread = sizeof(struct fcgi_header);
236 	SPLAY_INIT(&fcgi->fcg_clients);
237 
238 	/* assume it's enabled until we get a FCGI_BEGIN_REQUEST */
239 	fcgi->fcg_keep_conn = 1;
240 
241 	fcgi->fcg_bev = bufferevent_new(fcgi->fcg_s, fcgi_read, fcgi_write,
242 	    fcgi_error, fcgi);
243 	if (fcgi->fcg_bev == NULL)
244 		goto err;
245 
246 	bufferevent_enable(fcgi->fcg_bev, EV_READ | EV_WRITE);
247 	return;
248 
249 err:
250 	if (s != -1) {
251 		close(s);
252 		free(fcgi);
253 		fcgi_inflight_dec(__func__);
254 	}
255 }
256 
257 static int
258 parse_len(struct fcgi *fcgi, struct evbuffer *src)
259 {
260 	unsigned char		 c, x[3];
261 
262 	fcgi->fcg_toread--;
263 	evbuffer_remove(src, &c, 1);
264 	if (c >> 7 == 0)
265 		return (c);
266 
267 	if (fcgi->fcg_toread < 3)
268 		return (-1);
269 
270 	fcgi->fcg_toread -= 3;
271 	evbuffer_remove(src, x, sizeof(x));
272 	return (((c & 0x7F) << 24) | (x[0] << 16) | (x[1] << 8) | x[2]);
273 }
274 
275 static int
276 fcgi_parse_params(struct fcgi *fcgi, struct evbuffer *src, struct client *clt)
277 {
278 	char			 pname[32];
279 	char			 server[HOST_NAME_MAX + 1];
280 	char			 path[PATH_MAX];
281 	int			 nlen, vlen;
282 
283 	while (fcgi->fcg_toread > 0) {
284 		if ((nlen = parse_len(fcgi, src)) < 0 ||
285 		    (vlen = parse_len(fcgi, src)) < 0)
286 			return (-1);
287 
288 		if (fcgi->fcg_toread < nlen + vlen)
289 			return (-1);
290 
291 		if ((size_t)nlen > sizeof(pname) - 1) {
292 			/* ignore this parameter */
293 			fcgi->fcg_toread -= nlen - vlen;
294 			evbuffer_drain(src, nlen + vlen);
295 			continue;
296 		}
297 
298 		fcgi->fcg_toread -= nlen;
299 		evbuffer_remove(src, &pname, nlen);
300 		pname[nlen] = '\0';
301 
302 		if (!strcmp(pname, "SERVER_NAME") &&
303 		    (size_t)vlen < sizeof(server)) {
304 			fcgi->fcg_toread -= vlen;
305 			evbuffer_remove(src, &server, vlen);
306 			server[vlen] = '\0';
307 
308 			if ((clt->clt_server_name = strdup(server)) == NULL)
309 				return (-1);
310 			log_debug("clt %d: server_name: %s", clt->clt_id,
311 			    clt->clt_server_name);
312 			continue;
313 		}
314 
315 		if (!strcmp(pname, "SCRIPT_NAME") &&
316 		    (size_t)vlen < sizeof(path)) {
317 			fcgi->fcg_toread -= vlen;
318 			evbuffer_remove(src, &path, vlen);
319 			path[vlen] = '\0';
320 
321 			if ((clt->clt_script_name = strdup(path)) == NULL)
322 				return (-1);
323 			log_debug("clt %d: script_name: %s", clt->clt_id,
324 			    clt->clt_script_name);
325 			continue;
326 		}
327 
328 		if (!strcmp(pname, "PATH_INFO") &&
329 		    (size_t)vlen < sizeof(path)) {
330 			fcgi->fcg_toread -= vlen;
331 			evbuffer_remove(src, &path, vlen);
332 			path[vlen] = '\0';
333 
334 			if ((clt->clt_path_info = strdup(path)) == NULL)
335 				return (-1);
336 			log_debug("clt %d: path_info: %s", clt->clt_id,
337 			    clt->clt_path_info);
338 			continue;
339 		}
340 
341 		fcgi->fcg_toread -= vlen;
342 		evbuffer_drain(src, vlen);
343 	}
344 
345 	return (0);
346 }
347 
348 void
349 fcgi_read(struct bufferevent *bev, void *d)
350 {
351 	struct fcgi		*fcgi = d;
352 	struct galileo		*env = fcgi->fcg_env;
353 	struct evbuffer		*src = EVBUFFER_INPUT(bev);
354 	struct fcgi_header	 hdr;
355 	struct fcgi_begin_req	 breq;
356 	struct client		*clt, q;
357 	int			 role;
358 
359 	memset(&q, 0, sizeof(q));
360 
361 	for (;;) {
362 		if (EVBUFFER_LENGTH(src) < (size_t)fcgi->fcg_toread)
363 			return;
364 
365 		if (fcgi->fcg_want == FCGI_RECORD_HEADER) {
366 			fcgi->fcg_want = FCGI_RECORD_BODY;
367 			bufferevent_read(bev, &hdr, sizeof(hdr));
368 
369 #ifdef DEBUG
370 			log_warnx("header: v=%d t=%d id=%d len=%d p=%d",
371 			    hdr.version, hdr.type,
372 			    CAT(hdr.req_id0, hdr.req_id1),
373 			    CAT(hdr.content_len0, hdr.content_len1),
374 			    hdr.padding);
375 #endif
376 
377 			if (hdr.version != FCGI_VERSION_1) {
378 				log_warnx("unknown fastcgi version: %d",
379 				    hdr.version);
380 				fcgi_error(bev, EV_READ, d);
381 				return;
382 			}
383 
384 			fcgi->fcg_toread = CAT(hdr.content_len0,
385 			    hdr.content_len1);
386 			if (fcgi->fcg_toread < 0) {
387 				log_warnx("invalid record length: %d",
388 				    fcgi->fcg_toread);
389 				fcgi_error(bev, EV_READ, d);
390 				return;
391 			}
392 
393 			fcgi->fcg_padding = hdr.padding;
394 			if (fcgi->fcg_padding < 0) {
395 				log_warnx("invalid padding: %d",
396 				    fcgi->fcg_padding);
397 				fcgi_error(bev, EV_READ, d);
398 				return;
399 			}
400 
401 			fcgi->fcg_type = hdr.type;
402 			fcgi->fcg_rec_id = CAT(hdr.req_id0, hdr.req_id1);
403 			continue;
404 		}
405 
406 		q.clt_id = fcgi->fcg_rec_id;
407 		clt = SPLAY_FIND(client_tree, &fcgi->fcg_clients, &q);
408 
409 		switch (fcgi->fcg_type) {
410 		case FCGI_BEGIN_REQUEST:
411 			if (sizeof(breq) != fcgi->fcg_toread) {
412 				log_warnx("unexpected size for "
413 				    "FCGI_BEGIN_REQUEST");
414 				fcgi_error(bev, EV_READ, d);
415 				return;
416 			}
417 
418 			evbuffer_remove(src, &breq, sizeof(breq));
419 
420 			role = CAT(breq.role0, breq.role1);
421 			if (role != FCGI_RESPONDER) {
422 				log_warnx("unknown fastcgi role: %d",
423 				    role);
424 				if (fcgi_send_end_req(fcgi, fcgi->fcg_rec_id,
425 				    1, FCGI_UNKNOWN_ROLE) == -1) {
426 					fcgi_error(bev, EV_READ, d);
427 					return;
428 				}
429 				break;
430 			}
431 
432 			if (!fcgi->fcg_keep_conn) {
433 				log_warnx("trying to reuse the fastcgi "
434 				    "socket without marking it as so.");
435 				fcgi_error(bev, EV_READ, d);
436 				return;
437 			}
438 			fcgi->fcg_keep_conn = breq.flags & FCGI_KEEP_CONN;
439 
440 			if (clt != NULL) {
441 				log_warnx("ignoring attemp to re-use an "
442 				    "active request id (%d)",
443 				    fcgi->fcg_rec_id);
444 				break;
445 			}
446 
447 			if ((clt = calloc(1, sizeof(*clt))) == NULL) {
448 				log_warnx("calloc");
449 				break;
450 			}
451 
452 			clt->clt_id = fcgi->fcg_rec_id;
453 			clt->clt_fd = -1;
454 			clt->clt_fcgi = fcgi;
455 			SPLAY_INSERT(client_tree, &fcgi->fcg_clients, clt);
456 			break;
457 		case FCGI_PARAMS:
458 			if (clt == NULL) {
459 				log_warnx("got FCGI_PARAMS for inactive id "
460 				    "(%d)", fcgi->fcg_rec_id);
461 				evbuffer_drain(src, fcgi->fcg_toread);
462 				break;
463 			}
464 			if (fcgi->fcg_toread == 0) {
465 				evbuffer_drain(src, fcgi->fcg_toread);
466 				proxy_start_request(env, clt);
467 				break;
468 			}
469 			if (fcgi_parse_params(fcgi, src, clt) == -1) {
470 				log_warnx("fcgi_parse_params failed");
471 				fcgi_error(bev, EV_READ, d);
472 				return;
473 			}
474 			break;
475 		case FCGI_STDIN:
476 			/* ignore */
477 			evbuffer_drain(src, fcgi->fcg_toread);
478 			break;
479 		case FCGI_ABORT_REQUEST:
480 			if (clt == NULL) {
481 				log_warnx("got FCGI_ABORT_REQUEST for inactive"
482 				    " id (%d)", fcgi->fcg_rec_id);
483 				evbuffer_drain(src, fcgi->fcg_toread);
484 				break;
485 			}
486 			if (fcgi_end_request(clt, 1) == -1) {
487 				/* calls fcgi_error on failure */
488 				return;
489 			}
490 			break;
491 		default:
492 			log_warnx("unknown fastcgi record type %d",
493 			    fcgi->fcg_type);
494 			evbuffer_drain(src, fcgi->fcg_toread);
495 			break;
496 		}
497 
498 		/* Prepare for the next record. */
499 		evbuffer_drain(src, fcgi->fcg_padding);
500 		fcgi->fcg_want = FCGI_RECORD_HEADER;
501 		fcgi->fcg_toread = sizeof(struct fcgi_header);
502 	}
503 }
504 
505 void
506 fcgi_write(struct bufferevent *bev, void *d)
507 {
508 	struct fcgi		*fcgi = d;
509 
510 	(void)fcgi;
511 }
512 
513 void
514 fcgi_error(struct bufferevent *bev, short event, void *d)
515 {
516 	struct fcgi		*fcgi = d;
517 	struct galileo		*env = fcgi->fcg_env;
518 	struct client		*clt;
519 
520 	log_debug("fcgi failure, shutting down connection (ev: %x)",
521 	    event);
522 	fcgi_inflight_dec(__func__);
523 
524 	while ((clt = SPLAY_MIN(client_tree, &fcgi->fcg_clients)) != NULL) {
525 		SPLAY_REMOVE(client_tree, &fcgi->fcg_clients, clt);
526 		proxy_client_free(clt);
527 	}
528 
529 	close(fcgi->fcg_s);
530 	bufferevent_free(fcgi->fcg_bev);
531 	SPLAY_REMOVE(fcgi_tree, &env->sc_fcgi_socks, fcgi);
532 	free(fcgi);
533 
534 	return;
535 }
536 
537 int
538 clt_flush(struct client *clt)
539 {
540 	struct fcgi		*fcgi = clt->clt_fcgi;
541 	struct bufferevent	*bev = fcgi->fcg_bev;
542 	struct fcgi_header	 hdr;
543 
544 	if (clt->clt_buflen == 0)
545 		return (0);
546 
547 	memset(&hdr, 0, sizeof(hdr));
548 	hdr.version = FCGI_VERSION_1;
549 	hdr.type = FCGI_STDOUT;
550 	hdr.req_id0 = (clt->clt_id & 0xFF);
551 	hdr.req_id1 = (clt->clt_id >> 8);
552 	hdr.content_len0 = (clt->clt_buflen & 0xFF);
553 	hdr.content_len1 = (clt->clt_buflen >> 8);
554 
555 	if (bufferevent_write(bev, &hdr, sizeof(hdr)) == -1 ||
556 	    bufferevent_write(bev, clt->clt_buf, clt->clt_buflen) == -1) {
557 		fcgi_error(bev, EV_WRITE, fcgi);
558 		return (-1);
559 	}
560 
561 	clt->clt_buflen = 0;
562 
563 	return (0);
564 }
565 
566 int
567 clt_write(struct client *clt, const uint8_t *buf, size_t len)
568 {
569 	size_t			 left, copy;
570 
571 	while (len > 0) {
572 		left = sizeof(clt->clt_buf) - clt->clt_buflen;
573 		if (left == 0) {
574 			if (clt_flush(clt) == -1)
575 				return (-1);
576 			left = sizeof(clt->clt_buf);
577 		}
578 
579 		copy = MIN(left, len);
580 
581 		memcpy(&clt->clt_buf[clt->clt_buflen], buf, copy);
582 		clt->clt_buflen += copy;
583 		buf += copy;
584 		len -= copy;
585 	}
586 
587 	return (0);
588 }
589 
590 int
591 clt_write_bufferevent(struct client *clt, struct bufferevent *bev)
592 {
593 	struct evbuffer		*src = EVBUFFER_INPUT(bev);
594 	size_t			 len, left, copy;
595 
596 	len = EVBUFFER_LENGTH(src);
597 	while (len > 0) {
598 		left = sizeof(clt->clt_buf) - clt->clt_buflen;
599 		if (left == 0) {
600 			if (clt_flush(clt) == -1)
601 				return (-1);
602 			left = sizeof(clt->clt_buf);
603 		}
604 
605 		copy = bufferevent_read(bev, &clt->clt_buf[clt->clt_buflen],
606 		    MIN(left, len));
607 		clt->clt_buflen += copy;
608 
609 		len = EVBUFFER_LENGTH(src);
610 	}
611 
612 	return (0);
613 }
614 
615 int
616 clt_printf(struct client *clt, const char *fmt, ...)
617 {
618 	struct fcgi		*fcgi = clt->clt_fcgi;
619 	struct bufferevent	*bev = fcgi->fcg_bev;
620 	char			*str;
621 	va_list			 ap;
622 	int			 r;
623 
624 	va_start(ap, fmt);
625 	r = vasprintf(&str, fmt, ap);
626 	va_end(ap);
627 	if (r == -1) {
628 		fcgi_error(bev, EV_WRITE, fcgi);
629 		return (-1);
630 	}
631 
632 	r = clt_write(clt, str, r);
633 	free(str);
634 	return (r);
635 }
636 
637 int
638 fcgi_cmp(struct fcgi *a, struct fcgi *b)
639 {
640 	return ((int)a->fcg_id - b->fcg_id);
641 }
642 
643 int
644 fcgi_client_cmp(struct client *a, struct client *b)
645 {
646 	return ((int)a->clt_id - b->clt_id);
647 }
648 
649 SPLAY_GENERATE(fcgi_tree, fcgi, fcg_nodes, fcgi_cmp);
650 SPLAY_GENERATE(client_tree, client, clt_nodes, fcgi_client_cmp);
651