4 This file is part of avahi.
6 avahi is free software; you can redistribute it and/or modify it
7 under the terms of the GNU Lesser General Public License as
8 published by the Free Software Foundation; either version 2.1 of the
9 License, or (at your option) any later version.
11 avahi is distributed in the hope that it will be useful, but WITHOUT
12 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
13 or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General
14 Public License for more details.
16 You should have received a copy of the GNU Lesser General Public
17 License along with avahi; if not, write to the Free Software
18 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
27 #include <sys/socket.h>
28 #include <sys/types.h>
37 #include <avahi-core/log.h>
38 #include <libdaemon/dfork.h>
42 #include "setproctitle.h"
45 AVAHI_CHROOT_SUCCESS = 0,
47 AVAHI_CHROOT_GET_RESOLV_CONF,
49 AVAHI_CHROOT_GET_SERVER_INTROSPECT,
50 AVAHI_CHROOT_GET_ENTRY_GROUP_INTROSPECT,
51 AVAHI_CHROOT_GET_ADDRESS_RESOLVER_INTROSPECT,
52 AVAHI_CHROOT_GET_DOMAIN_BROWSER_INTROSPECT,
53 AVAHI_CHROOT_GET_HOST_NAME_RESOLVER_INTROSPECT,
54 AVAHI_CHROOT_GET_SERVICE_BROWSER_INTROSPECT,
55 AVAHI_CHROOT_GET_SERVICE_RESOLVER_INTROSPECT,
56 AVAHI_CHROOT_GET_SERVICE_TYPE_BROWSER_INTROSPECT,
58 AVAHI_CHROOT_UNLINK_PID,
59 AVAHI_CHROOT_UNLINK_SOCKET,
63 static const char* const get_file_name_table[AVAHI_CHROOT_MAX] = {
68 AVAHI_DBUS_INTROSPECTION_DIR"/Server.introspect",
69 AVAHI_DBUS_INTROSPECTION_DIR"/EntryGroup.introspect",
70 AVAHI_DBUS_INTROSPECTION_DIR"/AddressResolver.introspect",
71 AVAHI_DBUS_INTROSPECTION_DIR"/DomainBrowser.introspect",
72 AVAHI_DBUS_INTROSPECTION_DIR"/HostNameResolver.introspect",
73 AVAHI_DBUS_INTROSPECTION_DIR"/ServiceBrowser.introspect",
74 AVAHI_DBUS_INTROSPECTION_DIR"/ServiceResolver.introspect",
75 AVAHI_DBUS_INTROSPECTION_DIR"/ServiceTypeBrowser.introspect",
81 static const char *const unlink_file_name_table[AVAHI_CHROOT_MAX] = {
95 AVAHI_DAEMON_RUNTIME_DIR"/pid",
99 static int helper_fd = -1;
101 static int send_fd(int fd, int payload_fd) {
102 uint8_t dummy = AVAHI_CHROOT_SUCCESS;
107 char buf[CMSG_SPACE(sizeof(int))];
110 /* Send a file descriptor over the socket */
112 memset(&iov, 0, sizeof(iov));
113 memset(&msg, 0, sizeof(msg));
114 memset(&cmsg, 0, sizeof(cmsg));
116 iov.iov_base = &dummy;
117 iov.iov_len = sizeof(dummy);
124 msg.msg_control = &cmsg;
125 msg.msg_controllen = sizeof(cmsg);
128 cmsg.hdr.cmsg_len = CMSG_LEN(sizeof(int));
129 cmsg.hdr.cmsg_level = SOL_SOCKET;
130 cmsg.hdr.cmsg_type = SCM_RIGHTS;
131 *((int*) CMSG_DATA(&cmsg.hdr)) = payload_fd;
133 if (sendmsg(fd, &msg, 0) < 0) {
134 avahi_log_error("sendmsg() failed: %s", strerror(errno));
141 static int recv_fd(int fd) {
147 char buf[CMSG_SPACE(sizeof(int))];
150 /* Receive a file descriptor from a socket */
152 memset(&iov, 0, sizeof(iov));
153 memset(&msg, 0, sizeof(msg));
154 memset(&cmsg, 0, sizeof(cmsg));
156 iov.iov_base = &dummy;
157 iov.iov_len = sizeof(dummy);
164 msg.msg_control = cmsg.buf;
165 msg.msg_controllen = sizeof(cmsg);
168 cmsg.hdr.cmsg_len = CMSG_LEN(sizeof(int));
169 cmsg.hdr.cmsg_level = SOL_SOCKET;
170 cmsg.hdr.cmsg_type = SCM_RIGHTS;
171 *((int*) CMSG_DATA(&cmsg.hdr)) = -1;
173 if (recvmsg(fd, &msg, 0) <= 0) {
174 avahi_log_error("recvmsg() failed: %s", strerror(errno));
179 if (dummy != AVAHI_CHROOT_SUCCESS) {
184 if (!(h = CMSG_FIRSTHDR(&msg))) {
185 avahi_log_error("recvmsg() sent no fd.");
190 assert(h->cmsg_len = CMSG_LEN(sizeof(int)));
191 assert(h->cmsg_level = SOL_SOCKET);
192 assert(h->cmsg_type == SCM_RIGHTS);
194 return *((int*)CMSG_DATA(h));
198 static int helper_main(int fd) {
202 /* This is the main function of our helper process which is forked
203 * off to access files outside the chroot environment. Keep in
204 * mind that this code is security sensitive! */
206 avahi_log_debug(__FILE__": chroot() helper started");
212 if ((r = read(fd, &command, sizeof(command))) <= 0) {
218 avahi_log_error(__FILE__": read() failed: %s", strerror(errno));
222 assert(r == sizeof(command));
224 avahi_log_debug(__FILE__": chroot() helper got command %02x", command);
228 case AVAHI_CHROOT_GET_SERVER_INTROSPECT:
229 case AVAHI_CHROOT_GET_ENTRY_GROUP_INTROSPECT:
230 case AVAHI_CHROOT_GET_ADDRESS_RESOLVER_INTROSPECT:
231 case AVAHI_CHROOT_GET_DOMAIN_BROWSER_INTROSPECT:
232 case AVAHI_CHROOT_GET_HOST_NAME_RESOLVER_INTROSPECT:
233 case AVAHI_CHROOT_GET_SERVICE_BROWSER_INTROSPECT:
234 case AVAHI_CHROOT_GET_SERVICE_RESOLVER_INTROSPECT:
235 case AVAHI_CHROOT_GET_SERVICE_TYPE_BROWSER_INTROSPECT:
237 case AVAHI_CHROOT_GET_RESOLV_CONF: {
240 if ((payload = open(get_file_name_table[(int) command], O_RDONLY)) < 0) {
241 uint8_t c = AVAHI_CHROOT_FAILURE;
243 avahi_log_error(__FILE__": open() failed: %s", strerror(errno));
245 if (write(fd, &c, sizeof(c)) != sizeof(c)) {
246 avahi_log_error(__FILE__": write() failed: %s\n", strerror(errno));
253 if (send_fd(fd, payload) < 0)
261 case AVAHI_CHROOT_UNLINK_SOCKET:
262 case AVAHI_CHROOT_UNLINK_PID: {
263 uint8_t c = AVAHI_CHROOT_SUCCESS;
265 unlink(unlink_file_name_table[(int) command]);
267 if (write(fd, &c, sizeof(c)) != sizeof(c)) {
268 avahi_log_error(__FILE__": write() failed: %s\n", strerror(errno));
276 avahi_log_error(__FILE__": Unknown command %02x.", command);
285 avahi_log_debug(__FILE__": chroot() helper exiting with return value %i", ret);
290 int avahi_chroot_helper_start(const char *argv0) {
294 assert(helper_fd < 0);
296 if (socketpair(AF_UNIX, SOCK_STREAM, 0, sock) < 0) {
297 avahi_log_error("socketpair() failed: %s", strerror(errno));
301 if ((pid = fork()) < 0) {
304 avahi_log_error(__FILE__": fork() failed: %s", strerror(errno));
306 } else if (pid == 0) {
310 /* Drop all remaining capabilities */
311 avahi_caps_drop_all();
313 avahi_set_proc_title("%s: chroot helper process", argv0);
316 helper_main(sock[1]);
326 void avahi_chroot_helper_shutdown(void) {
335 int avahi_chroot_helper_get_fd(const char *fname) {
337 if (helper_fd >= 0) {
340 for (command = 2; command < AVAHI_CHROOT_MAX; command++)
341 if (get_file_name_table[(int) command] &&
342 strcmp(fname, get_file_name_table[(int) command]) == 0)
345 if (command >= AVAHI_CHROOT_MAX) {
346 avahi_log_error("chroot() helper accessed for invalid file name");
351 assert(get_file_name_table[(int) command]);
353 if (write(helper_fd, &command, sizeof(command)) < 0) {
354 avahi_log_error("write() failed: %s\n", strerror(errno));
358 return recv_fd(helper_fd);
361 return open(fname, O_RDONLY);
365 FILE *avahi_chroot_helper_get_file(const char *fname) {
369 if ((fd = avahi_chroot_helper_get_fd(fname)) < 0)
378 int avahi_chroot_helper_unlink(const char *fname) {
380 if (helper_fd >= 0) {
384 for (command = 2; command < AVAHI_CHROOT_MAX; command++)
385 if (unlink_file_name_table[(int) command] &&
386 strcmp(fname, unlink_file_name_table[(int) command]) == 0)
389 if (command >= AVAHI_CHROOT_MAX) {
390 avahi_log_error("chroot() helper accessed for invalid file name");
395 if (write(helper_fd, &command, sizeof(command)) < 0) {
396 avahi_log_error("write() failed: %s\n", strerror(errno));
400 if ((r = read(helper_fd, &c, sizeof(c))) < 0) {
401 avahi_log_error("read() failed: %s\n", r < 0 ? strerror(errno) : "EOF");
409 return unlink(fname);