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Date:: Sat Feb 4 13:58:02 2023 UTC
Message:: include sha2.h where sha1.h was included
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1 /*
2  * Copyright (c) 2022 Stefan Sperling <stsp@openbsd.org>
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/types.h>
18 #include <sys/queue.h>
19 #include <sys/socket.h>
20 #include <sys/uio.h>
21 
22 #include <errno.h>
23 #include <event.h>
24 #include <siphash.h>
25 #include <stdint.h>
26 #include <stdio.h>
27 #include <stdlib.h>
28 #include <string.h>
29 #include <imsg.h>
30 #include <limits.h>
31 #include <sha1.h>
32 #include <sha2.h>
33 #include <signal.h>
34 #include <unistd.h>
35 
36 #include "got_error.h"
37 
38 #include "gotd.h"
39 #include "log.h"
40 #include "listen.h"
41 
42 #ifndef nitems
43 #define nitems(_a)	(sizeof((_a)) / sizeof((_a)[0]))
44 #endif
45 
46 struct gotd_listen_client {
47 	STAILQ_ENTRY(gotd_listen_client)	 entry;
48 	uint32_t			 id;
49 	int				 fd;
50 	uid_t				 euid;
51 };
52 STAILQ_HEAD(gotd_listen_clients, gotd_listen_client);
53 
54 static struct gotd_listen_clients gotd_listen_clients[GOTD_CLIENT_TABLE_SIZE];
55 static SIPHASH_KEY clients_hash_key;
56 static volatile int listen_client_cnt;
57 static int inflight;
58 
59 struct gotd_uid_connection_counter {
60 	STAILQ_ENTRY(gotd_uid_connection_counter) entry;
61 	uid_t euid;
62 	int nconnections;
63 };
64 STAILQ_HEAD(gotd_client_uids, gotd_uid_connection_counter);
65 static struct gotd_client_uids gotd_client_uids[GOTD_CLIENT_TABLE_SIZE];
66 static SIPHASH_KEY uid_hash_key;
67 
68 static struct {
69 	pid_t pid;
70 	const char *title;
71 	int fd;
72 	struct gotd_imsgev iev;
73 	struct gotd_imsgev pause;
74 	struct gotd_uid_connection_limit *connection_limits;
75 	size_t nconnection_limits;
76 } gotd_listen;
77 
78 static int inflight;
79 
80 static void listen_shutdown(void);
81 
82 static void
83 listen_sighdlr(int sig, short event, void *arg)
84 {
85 	/*
86 	 * Normal signal handler rules don't apply because libevent
87 	 * decouples for us.
88 	 */
89 
90 	switch (sig) {
91 	case SIGHUP:
92 		break;
93 	case SIGUSR1:
94 		break;
95 	case SIGTERM:
96 	case SIGINT:
97 		listen_shutdown();
98 		/* NOTREACHED */
99 		break;
100 	default:
101 		fatalx("unexpected signal");
102 	}
103 }
104 
105 static uint64_t
106 client_hash(uint32_t client_id)
107 {
108 	return SipHash24(&clients_hash_key, &client_id, sizeof(client_id));
109 }
110 
111 static void
112 add_client(struct gotd_listen_client *client)
113 {
114 	uint64_t slot = client_hash(client->id) % nitems(gotd_listen_clients);
115 	STAILQ_INSERT_HEAD(&gotd_listen_clients[slot], client, entry);
116 	listen_client_cnt++;
117 }
118 
119 static struct gotd_listen_client *
120 find_client(uint32_t client_id)
121 {
122 	uint64_t slot;
123 	struct gotd_listen_client *c;
124 
125 	slot = client_hash(client_id) % nitems(gotd_listen_clients);
126 	STAILQ_FOREACH(c, &gotd_listen_clients[slot], entry) {
127 		if (c->id == client_id)
128 			return c;
129 	}
130 
131 	return NULL;
132 }
133 
134 static uint32_t
135 get_client_id(void)
136 {
137 	int duplicate = 0;
138 	uint32_t id;
139 
140 	do {
141 		id = arc4random();
142 		duplicate = (find_client(id) != NULL);
143 	} while (duplicate || id == 0);
144 
145 	return id;
146 }
147 
148 static uint64_t
149 uid_hash(uid_t euid)
150 {
151 	return SipHash24(&uid_hash_key, &euid, sizeof(euid));
152 }
153 
154 static void
155 add_uid_connection_counter(struct gotd_uid_connection_counter *counter)
156 {
157 	uint64_t slot = uid_hash(counter->euid) % nitems(gotd_client_uids);
158 	STAILQ_INSERT_HEAD(&gotd_client_uids[slot], counter, entry);
159 }
160 
161 static void
162 remove_uid_connection_counter(struct gotd_uid_connection_counter *counter)
163 {
164 	uint64_t slot = uid_hash(counter->euid) % nitems(gotd_client_uids);
165 	STAILQ_REMOVE(&gotd_client_uids[slot], counter,
166 	    gotd_uid_connection_counter, entry);
167 }
168 
169 static struct gotd_uid_connection_counter *
170 find_uid_connection_counter(uid_t euid)
171 {
172 	uint64_t slot;
173 	struct gotd_uid_connection_counter *c;
174 
175 	slot = uid_hash(euid) % nitems(gotd_client_uids);
176 	STAILQ_FOREACH(c, &gotd_client_uids[slot], entry) {
177 		if (c->euid == euid)
178 			return c;
179 	}
180 
181 	return NULL;
182 }
183 
184 struct gotd_uid_connection_limit *
185 gotd_find_uid_connection_limit(struct gotd_uid_connection_limit *limits,
186     size_t nlimits, uid_t uid)
187 {
188 	/* This array is always sorted to allow for binary search. */
189 	int i, left = 0, right = nlimits - 1;
190 
191 	while (left <= right) {
192 		i = ((left + right) / 2);
193 		if (limits[i].uid == uid)
194 			return &limits[i];
195 		if (limits[i].uid > uid)
196 			left = i + 1;
197 		else
198 			right = i - 1;
199 	}
200 
201 	return NULL;
202 }
203 
204 static const struct got_error *
205 disconnect(struct gotd_listen_client *client)
206 {
207 	struct gotd_uid_connection_counter *counter;
208 	uint64_t slot;
209 	int client_fd;
210 
211 	log_debug("client on fd %d disconnecting", client->fd);
212 
213 	slot = client_hash(client->id) % nitems(gotd_listen_clients);
214 	STAILQ_REMOVE(&gotd_listen_clients[slot], client,
215 	    gotd_listen_client, entry);
216 
217 	counter = find_uid_connection_counter(client->euid);
218 	if (counter) {
219 		if (counter->nconnections > 0)
220 			counter->nconnections--;
221 		if (counter->nconnections == 0) {
222 			remove_uid_connection_counter(counter);
223 			free(counter);
224 		}
225 	}
226 
227 	client_fd = client->fd;
228 	free(client);
229 	inflight--;
230 	listen_client_cnt--;
231 	if (close(client_fd) == -1)
232 		return got_error_from_errno("close");
233 
234 	return NULL;
235 }
236 
237 static int
238 accept_reserve(int fd, struct sockaddr *addr, socklen_t *addrlen,
239     int reserve, volatile int *counter)
240 {
241 	int ret;
242 
243 	if (getdtablecount() + reserve +
244 	    ((*counter + 1) * GOTD_FD_NEEDED) >= getdtablesize()) {
245 		log_debug("inflight fds exceeded");
246 		errno = EMFILE;
247 		return -1;
248 	}
249 
250 	if ((ret = accept4(fd, addr, addrlen,
251 	    SOCK_NONBLOCK | SOCK_CLOEXEC)) > -1) {
252 		(*counter)++;
253 	}
254 
255 	return ret;
256 }
257 
258 static void
259 gotd_accept_paused(int fd, short event, void *arg)
260 {
261 	event_add(&gotd_listen.iev.ev, NULL);
262 }
263 
264 static void
265 gotd_accept(int fd, short event, void *arg)
266 {
267 	struct gotd_imsgev *iev = arg;
268 	struct sockaddr_storage ss;
269 	struct timeval backoff;
270 	socklen_t len;
271 	int s = -1;
272 	struct gotd_listen_client *client = NULL;
273 	struct gotd_uid_connection_counter *counter = NULL;
274 	struct gotd_imsg_connect iconn;
275 	uid_t euid;
276 	gid_t egid;
277 
278 	backoff.tv_sec = 1;
279 	backoff.tv_usec = 0;
280 
281 	if (event_add(&gotd_listen.iev.ev, NULL) == -1) {
282 		log_warn("event_add");
283 		return;
284 	}
285 	if (event & EV_TIMEOUT)
286 		return;
287 
288 	len = sizeof(ss);
289 
290 	/* Other backoff conditions apart from EMFILE/ENFILE? */
291 	s = accept_reserve(fd, (struct sockaddr *)&ss, &len, GOTD_FD_RESERVE,
292 	    &inflight);
293 	if (s == -1) {
294 		switch (errno) {
295 		case EINTR:
296 		case EWOULDBLOCK:
297 		case ECONNABORTED:
298 			return;
299 		case EMFILE:
300 		case ENFILE:
301 			event_del(&gotd_listen.iev.ev);
302 			evtimer_add(&gotd_listen.pause.ev, &backoff);
303 			return;
304 		default:
305 			log_warn("accept");
306 			return;
307 		}
308 	}
309 
310 	if (listen_client_cnt >= GOTD_MAXCLIENTS)
311 		goto err;
312 
313 	if (getpeereid(s, &euid, &egid) == -1) {
314 		log_warn("getpeerid");
315 		goto err;
316 	}
317 
318 	counter = find_uid_connection_counter(euid);
319 	if (counter == NULL) {
320 		counter = calloc(1, sizeof(*counter));
321 		if (counter == NULL) {
322 			log_warn("%s: calloc", __func__);
323 			goto err;
324 		}
325 		counter->euid = euid;
326 		counter->nconnections = 1;
327 		add_uid_connection_counter(counter);
328 	} else {
329 		int max_connections = GOTD_MAX_CONN_PER_UID;
330 		struct gotd_uid_connection_limit *limit;
331 
332 		limit = gotd_find_uid_connection_limit(
333 		    gotd_listen.connection_limits,
334 		    gotd_listen.nconnection_limits, euid);
335 		if (limit)
336 			max_connections = limit->max_connections;
337 
338 		if (counter->nconnections >= max_connections) {
339 			log_warnx("maximum connections exceeded for uid %d",
340 			    euid);
341 			goto err;
342 		}
343 		counter->nconnections++;
344 	}
345 
346 	client = calloc(1, sizeof(*client));
347 	if (client == NULL) {
348 		log_warn("%s: calloc", __func__);
349 		goto err;
350 	}
351 	client->id = get_client_id();
352 	client->fd = s;
353 	client->euid = euid;
354 	s = -1;
355 	add_client(client);
356 	log_debug("%s: new client connected on fd %d uid %d gid %d", __func__,
357 	    client->fd, euid, egid);
358 
359 	memset(&iconn, 0, sizeof(iconn));
360 	iconn.client_id = client->id;
361 	iconn.euid = euid;
362 	iconn.egid = egid;
363 	s = dup(client->fd);
364 	if (s == -1) {
365 		log_warn("%s: dup", __func__);
366 		goto err;
367 	}
368 	if (gotd_imsg_compose_event(iev, GOTD_IMSG_CONNECT, PROC_LISTEN, s,
369 	    &iconn, sizeof(iconn)) == -1) {
370 		log_warn("imsg compose CONNECT");
371 		goto err;
372 	}
373 
374 	return;
375 err:
376 	inflight--;
377 	if (client)
378 		disconnect(client);
379 	if (s != -1)
380 		close(s);
381 }
382 
383 static const struct got_error *
384 recv_disconnect(struct imsg *imsg)
385 {
386 	struct gotd_imsg_disconnect idisconnect;
387 	size_t datalen;
388 	struct gotd_listen_client *client = NULL;
389 
390 	datalen = imsg->hdr.len - IMSG_HEADER_SIZE;
391 	if (datalen != sizeof(idisconnect))
392 		return got_error(GOT_ERR_PRIVSEP_LEN);
393 	memcpy(&idisconnect, imsg->data, sizeof(idisconnect));
394 
395 	log_debug("client disconnecting");
396 
397 	client = find_client(idisconnect.client_id);
398 	if (client == NULL)
399 		return got_error(GOT_ERR_CLIENT_ID);
400 
401 	return disconnect(client);
402 }
403 
404 static void
405 listen_dispatch(int fd, short event, void *arg)
406 {
407 	const struct got_error *err = NULL;
408 	struct gotd_imsgev *iev = arg;
409 	struct imsgbuf *ibuf = &iev->ibuf;
410 	struct imsg imsg;
411 	ssize_t n;
412 	int shut = 0;
413 
414 	if (event & EV_READ) {
415 		if ((n = imsg_read(ibuf)) == -1 && errno != EAGAIN)
416 			fatal("imsg_read error");
417 		if (n == 0)	/* Connection closed. */
418 			shut = 1;
419 	}
420 
421 	if (event & EV_WRITE) {
422 		n = msgbuf_write(&ibuf->w);
423 		if (n == -1 && errno != EAGAIN)
424 			fatal("msgbuf_write");
425 		if (n == 0)	/* Connection closed. */
426 			shut = 1;
427 	}
428 
429 	for (;;) {
430 		if ((n = imsg_get(ibuf, &imsg)) == -1)
431 			fatal("%s: imsg_get", __func__);
432 		if (n == 0)	/* No more messages. */
433 			break;
434 
435 		switch (imsg.hdr.type) {
436 		case GOTD_IMSG_DISCONNECT:
437 			err = recv_disconnect(&imsg);
438 			if (err)
439 				log_warnx("%s: disconnect: %s",
440 				    gotd_listen.title, err->msg);
441 			break;
442 		default:
443 			log_debug("%s: unexpected imsg %d", gotd_listen.title,
444 			    imsg.hdr.type);
445 			break;
446 		}
447 
448 		imsg_free(&imsg);
449 	}
450 
451 	if (!shut) {
452 		gotd_imsg_event_add(iev);
453 	} else {
454 		/* This pipe is dead. Remove its event handler */
455 		event_del(&iev->ev);
456 		event_loopexit(NULL);
457 	}
458 }
459 
460 void
461 listen_main(const char *title, int gotd_socket,
462     struct gotd_uid_connection_limit *connection_limits,
463     size_t nconnection_limits)
464 {
465 	struct gotd_imsgev iev;
466 	struct event evsigint, evsigterm, evsighup, evsigusr1;
467 
468 	arc4random_buf(&clients_hash_key, sizeof(clients_hash_key));
469 	arc4random_buf(&uid_hash_key, sizeof(uid_hash_key));
470 
471 	gotd_listen.title = title;
472 	gotd_listen.pid = getpid();
473 	gotd_listen.fd = gotd_socket;
474 	gotd_listen.connection_limits = connection_limits;
475 	gotd_listen.nconnection_limits = nconnection_limits;
476 
477 	signal_set(&evsigint, SIGINT, listen_sighdlr, NULL);
478 	signal_set(&evsigterm, SIGTERM, listen_sighdlr, NULL);
479 	signal_set(&evsighup, SIGHUP, listen_sighdlr, NULL);
480 	signal_set(&evsigusr1, SIGUSR1, listen_sighdlr, NULL);
481 	signal(SIGPIPE, SIG_IGN);
482 
483 	signal_add(&evsigint, NULL);
484 	signal_add(&evsigterm, NULL);
485 	signal_add(&evsighup, NULL);
486 	signal_add(&evsigusr1, NULL);
487 
488 	imsg_init(&iev.ibuf, GOTD_FILENO_MSG_PIPE);
489 	iev.handler = listen_dispatch;
490 	iev.events = EV_READ;
491 	iev.handler_arg = NULL;
492 	event_set(&iev.ev, iev.ibuf.fd, EV_READ, listen_dispatch, &iev);
493 	if (event_add(&iev.ev, NULL) == -1)
494 		fatalx("event add");
495 
496 	event_set(&gotd_listen.iev.ev, gotd_listen.fd, EV_READ | EV_PERSIST,
497 	    gotd_accept, &iev);
498 	if (event_add(&gotd_listen.iev.ev, NULL))
499 		fatalx("event add");
500 	evtimer_set(&gotd_listen.pause.ev, gotd_accept_paused, NULL);
501 
502 	event_dispatch();
503 
504 	listen_shutdown();
505 }
506 
507 static void
508 listen_shutdown(void)
509 {
510 	log_debug("%s: shutting down", gotd_listen.title);
511 
512 	free(gotd_listen.connection_limits);
513 	if (gotd_listen.fd != -1)
514 		close(gotd_listen.fd);
515 
516 	exit(0);
517 }