service.c revision 370004 
1/*-
2 * Copyright (c) 2013 The FreeBSD Foundation
3 * Copyright (c) 2015 Mariusz Zaborski <oshogbo@FreeBSD.org>
4 * All rights reserved.
5 *
6 * This software was developed by Pawel Jakub Dawidek under sponsorship from
7 * the FreeBSD Foundation.
8 *
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
11 * are met:
12 * 1. Redistributions of source code must retain the above copyright
13 *    notice, this list of conditions and the following disclaimer.
14 * 2. Redistributions in binary form must reproduce the above copyright
15 *    notice, this list of conditions and the following disclaimer in the
16 *    documentation and/or other materials provided with the distribution.
17 *
18 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
19 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
20 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
21 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
22 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
23 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
24 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
25 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
26 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
27 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
28 * SUCH DAMAGE.
29 */
30
31#include <sys/cdefs.h>
32__FBSDID("$FreeBSD: stable/11/lib/libcasper/libcasper/service.c 370004 2021-06-16 20:30:46Z git2svn $");
33
34#include <sys/types.h>
35#include <sys/queue.h>
36#include <sys/socket.h>
37#include <sys/nv.h>
38
39#include <assert.h>
40#include <dirent.h>
41#include <err.h>
42#include <errno.h>
43#include <fcntl.h>
44#include <paths.h>
45#include <stdbool.h>
46#include <stdio.h>
47#include <stdlib.h>
48#include <string.h>
49#include <strings.h>
50#include <unistd.h>
51
52#include "libcasper.h"
53#include "libcasper_impl.h"
54
55/*
56 * Currently there is only one service_connection per service.
57 * In the future we may want multiple connections from multiple clients
58 * per one service instance, but it has to be carefully designed.
59 * The problem is that we may restrict/sandbox service instance according
60 * to the limits provided. When new connection comes in with different
61 * limits we won't be able to access requested resources.
62 * Not to mention one process will serve to mutiple mutually untrusted
63 * clients and compromise of this service instance by one of its clients
64 * can lead to compromise of the other clients.
65 */
66
67/*
68 * Client connections to the given service.
69 */
70#define	SERVICE_CONNECTION_MAGIC	0x5e91c0ec
71struct service_connection {
72	int		 sc_magic;
73	cap_channel_t	*sc_chan;
74	nvlist_t	*sc_limits;
75	TAILQ_ENTRY(service_connection) sc_next;
76};
77
78#define	SERVICE_MAGIC	0x5e91ce
79struct service {
80	int			 s_magic;
81	char			*s_name;
82	uint64_t		 s_flags;
83	service_limit_func_t	*s_limit;
84	service_command_func_t	*s_command;
85	TAILQ_HEAD(, service_connection) s_connections;
86};
87
88struct service *
89service_alloc(const char *name, service_limit_func_t *limitfunc,
90    service_command_func_t *commandfunc, uint64_t flags)
91{
92	struct service *service;
93
94	service = malloc(sizeof(*service));
95	if (service == NULL)
96		return (NULL);
97	service->s_name = strdup(name);
98	if (service->s_name == NULL) {
99		free(service);
100		return (NULL);
101	}
102	service->s_limit = limitfunc;
103	service->s_command = commandfunc;
104	service->s_flags = flags;
105	TAILQ_INIT(&service->s_connections);
106	service->s_magic = SERVICE_MAGIC;
107
108	return (service);
109}
110
111void
112service_free(struct service *service)
113{
114	struct service_connection *sconn;
115
116	assert(service->s_magic == SERVICE_MAGIC);
117
118	service->s_magic = 0;
119	while ((sconn = service_connection_first(service)) != NULL)
120		service_connection_remove(service, sconn);
121	free(service->s_name);
122	free(service);
123}
124
125struct service_connection *
126service_connection_add(struct service *service, int sock,
127    const nvlist_t *limits)
128{
129	struct service_connection *sconn;
130	int serrno;
131
132	assert(service->s_magic == SERVICE_MAGIC);
133
134	sconn = malloc(sizeof(*sconn));
135	if (sconn == NULL)
136		return (NULL);
137	sconn->sc_chan = cap_wrap(sock);
138	if (sconn->sc_chan == NULL) {
139		serrno = errno;
140		free(sconn);
141		errno = serrno;
142		return (NULL);
143	}
144	if (limits == NULL) {
145		sconn->sc_limits = NULL;
146	} else {
147		sconn->sc_limits = nvlist_clone(limits);
148		if (sconn->sc_limits == NULL) {
149			serrno = errno;
150			(void)cap_unwrap(sconn->sc_chan);
151			free(sconn);
152			errno = serrno;
153			return (NULL);
154		}
155	}
156	sconn->sc_magic = SERVICE_CONNECTION_MAGIC;
157	TAILQ_INSERT_TAIL(&service->s_connections, sconn, sc_next);
158	return (sconn);
159}
160
161void
162service_connection_remove(struct service *service,
163    struct service_connection *sconn)
164{
165
166	assert(service->s_magic == SERVICE_MAGIC);
167	assert(sconn->sc_magic == SERVICE_CONNECTION_MAGIC);
168
169	TAILQ_REMOVE(&service->s_connections, sconn, sc_next);
170	sconn->sc_magic = 0;
171	nvlist_destroy(sconn->sc_limits);
172	cap_close(sconn->sc_chan);
173	free(sconn);
174}
175
176int
177service_connection_clone(struct service *service,
178    struct service_connection *sconn)
179{
180	struct service_connection *newsconn;
181	int serrno, sock[2];
182
183	if (socketpair(PF_UNIX, SOCK_STREAM | SOCK_NONBLOCK, 0, sock) < 0)
184		return (-1);
185
186	newsconn = service_connection_add(service, sock[0],
187	    service_connection_get_limits(sconn));
188	if (newsconn == NULL) {
189		serrno = errno;
190		close(sock[0]);
191		close(sock[1]);
192		errno = serrno;
193		return (-1);
194	}
195
196	return (sock[1]);
197}
198
199struct service_connection *
200service_connection_first(struct service *service)
201{
202	struct service_connection *sconn;
203
204	assert(service->s_magic == SERVICE_MAGIC);
205
206	sconn = TAILQ_FIRST(&service->s_connections);
207	assert(sconn == NULL ||
208	    sconn->sc_magic == SERVICE_CONNECTION_MAGIC);
209	return (sconn);
210}
211
212struct service_connection *
213service_connection_next(struct service_connection *sconn)
214{
215
216	assert(sconn->sc_magic == SERVICE_CONNECTION_MAGIC);
217
218	sconn = TAILQ_NEXT(sconn, sc_next);
219	assert(sconn == NULL ||
220	    sconn->sc_magic == SERVICE_CONNECTION_MAGIC);
221	return (sconn);
222}
223
224cap_channel_t *
225service_connection_get_chan(const struct service_connection *sconn)
226{
227
228	assert(sconn->sc_magic == SERVICE_CONNECTION_MAGIC);
229
230	return (sconn->sc_chan);
231}
232
233int
234service_connection_get_sock(const struct service_connection *sconn)
235{
236
237	assert(sconn->sc_magic == SERVICE_CONNECTION_MAGIC);
238
239	return (cap_sock(sconn->sc_chan));
240}
241
242const nvlist_t *
243service_connection_get_limits(const struct service_connection *sconn)
244{
245
246	assert(sconn->sc_magic == SERVICE_CONNECTION_MAGIC);
247
248	return (sconn->sc_limits);
249}
250
251void
252service_connection_set_limits(struct service_connection *sconn,
253    nvlist_t *limits)
254{
255
256	assert(sconn->sc_magic == SERVICE_CONNECTION_MAGIC);
257
258	nvlist_destroy(sconn->sc_limits);
259	sconn->sc_limits = limits;
260}
261
262void
263service_message(struct service *service, struct service_connection *sconn)
264{
265	nvlist_t *nvlin, *nvlout;
266	const char *cmd;
267	int error;
268
269	nvlin = cap_recv_nvlist(service_connection_get_chan(sconn), 0);
270	if (nvlin == NULL) {
271		service_connection_remove(service, sconn);
272		return;
273	}
274
275	error = EDOOFUS;
276	nvlout = nvlist_create(0);
277
278	cmd = nvlist_get_string(nvlin, "cmd");
279	if (strcmp(cmd, "limit_set") == 0) {
280		nvlist_t *nvllim;
281
282		nvllim = nvlist_take_nvlist(nvlin, "limits");
283		if (service->s_limit == NULL) {
284			error = EOPNOTSUPP;
285		} else {
286			error = service->s_limit(
287			    service_connection_get_limits(sconn), nvllim);
288		}
289		if (error == 0) {
290			service_connection_set_limits(sconn, nvllim);
291			/* Function consumes nvllim. */
292		} else {
293			nvlist_destroy(nvllim);
294		}
295	} else if (strcmp(cmd, "limit_get") == 0) {
296		const nvlist_t *nvllim;
297
298		nvllim = service_connection_get_limits(sconn);
299		if (nvllim != NULL)
300			nvlist_add_nvlist(nvlout, "limits", nvllim);
301		else
302			nvlist_add_null(nvlout, "limits");
303		error = 0;
304	} else if (strcmp(cmd, "clone") == 0) {
305		int sock;
306
307		sock = service_connection_clone(service, sconn);
308		if (sock == -1) {
309			error = errno;
310		} else {
311			nvlist_move_descriptor(nvlout, "sock", sock);
312			error = 0;
313		}
314	} else {
315		error = service->s_command(cmd,
316		    service_connection_get_limits(sconn), nvlin, nvlout);
317	}
318
319	nvlist_destroy(nvlin);
320	nvlist_add_number(nvlout, "error", (uint64_t)error);
321
322	if (cap_send_nvlist(service_connection_get_chan(sconn), nvlout) == -1)
323		service_connection_remove(service, sconn);
324
325	nvlist_destroy(nvlout);
326}
327
328static int
329fd_add(fd_set *fdsp, int maxfd, int fd)
330{
331
332	FD_SET(fd, fdsp);
333	return (fd > maxfd ? fd : maxfd);
334}
335
336const char *
337service_name(struct service *service)
338{
339
340	assert(service->s_magic == SERVICE_MAGIC);
341	return (service->s_name);
342}
343
344static void
345stdnull(void)
346{
347	int fd;
348
349	fd = open(_PATH_DEVNULL, O_RDWR);
350	if (fd == -1)
351		errx(1, "Unable to open %s", _PATH_DEVNULL);
352
353	if (setsid() == -1)
354		errx(1, "Unable to detach from session");
355
356	if (dup2(fd, STDIN_FILENO) == -1)
357		errx(1, "Unable to cover stdin");
358	if (dup2(fd, STDOUT_FILENO) == -1)
359		errx(1, "Unable to cover stdout");
360	if (dup2(fd, STDERR_FILENO) == -1)
361		errx(1, "Unable to cover stderr");
362
363	if (fd > STDERR_FILENO)
364		close(fd);
365}
366
367static void
368service_clean(int *sockp, int *procfdp, uint64_t flags)
369{
370	int fd, maxfd, minfd;
371
372	fd_fix_environment(sockp);
373	fd_fix_environment(procfdp);
374
375	assert(*sockp > STDERR_FILENO);
376	assert(*procfdp > STDERR_FILENO);
377	assert(*sockp != *procfdp);
378
379	if ((flags & CASPER_SERVICE_STDIO) == 0)
380		stdnull();
381
382	if ((flags & CASPER_SERVICE_FD) == 0) {
383		if (*procfdp > *sockp) {
384			maxfd = *procfdp;
385			minfd = *sockp;
386		} else {
387			maxfd = *sockp;
388			minfd = *procfdp;
389		}
390
391		for (fd = STDERR_FILENO + 1; fd < maxfd; fd++) {
392			if (fd != minfd)
393				close(fd);
394		}
395		closefrom(maxfd + 1);
396	}
397}
398
399void
400service_start(struct service *service, int sock, int procfd)
401{
402	struct service_connection *sconn, *sconntmp;
403	fd_set fds;
404	int maxfd, nfds;
405
406	assert(service != NULL);
407	assert(service->s_magic == SERVICE_MAGIC);
408	setproctitle("%s", service->s_name);
409	service_clean(&sock, &procfd, service->s_flags);
410
411	if (service_connection_add(service, sock, NULL) == NULL)
412		exit(1);
413
414	for (;;) {
415		FD_ZERO(&fds);
416		maxfd = -1;
417		for (sconn = service_connection_first(service); sconn != NULL;
418		    sconn = service_connection_next(sconn)) {
419			maxfd = fd_add(&fds, maxfd,
420			    service_connection_get_sock(sconn));
421		}
422
423		assert(maxfd >= 0);
424		assert(maxfd + 1 <= (int)FD_SETSIZE);
425		nfds = select(maxfd + 1, &fds, NULL, NULL, NULL);
426		if (nfds < 0) {
427			if (errno != EINTR)
428				exit(1);
429			continue;
430		} else if (nfds == 0) {
431			/* Timeout. */
432			abort();
433		}
434
435		for (sconn = service_connection_first(service); sconn != NULL;
436		    sconn = sconntmp) {
437			/*
438			 * Prepare for connection to be removed from the list
439			 * on failure.
440			 */
441			sconntmp = service_connection_next(sconn);
442			if (FD_ISSET(service_connection_get_sock(sconn), &fds))
443				service_message(service, sconn);
444		}
445		if (service_connection_first(service) == NULL) {
446			/*
447			 * No connections left, exiting.
448			 */
449			break;
450		}
451	}
452
453	exit(0);
454}
455