property_service.cpp revision db3f267c99411b10144998c6c1f1a6288d0191bc 
1/*
2 * Copyright (C) 2007 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#include <stdio.h>
18#include <stdlib.h>
19#include <unistd.h>
20#include <string.h>
21#include <ctype.h>
22#include <fcntl.h>
23#include <stdarg.h>
24#include <dirent.h>
25#include <limits.h>
26#include <errno.h>
27#include <sys/poll.h>
28
29#include <cutils/misc.h>
30#include <cutils/sockets.h>
31#include <cutils/multiuser.h>
32
33#define _REALLY_INCLUDE_SYS__SYSTEM_PROPERTIES_H_
34#include <sys/_system_properties.h>
35
36#include <sys/socket.h>
37#include <sys/un.h>
38#include <sys/select.h>
39#include <sys/types.h>
40#include <netinet/in.h>
41#include <sys/mman.h>
42#include <private/android_filesystem_config.h>
43
44#include <selinux/selinux.h>
45#include <selinux/label.h>
46
47#include "property_service.h"
48#include "init.h"
49#include "util.h"
50#include "log.h"
51
52#define PERSISTENT_PROPERTY_DIR  "/data/property"
53
54static int persistent_properties_loaded = 0;
55static int property_area_inited = 0;
56
57static int property_set_fd = -1;
58
59struct workspace {
60    size_t size;
61    int fd;
62};
63
64static int init_workspace(workspace *w, size_t size)
65{
66    int fd = open(PROP_FILENAME, O_RDONLY | O_NOFOLLOW);
67    if (fd < 0)
68        return -1;
69
70    w->size = size;
71    w->fd = fd;
72    return 0;
73}
74
75static workspace pa_workspace;
76
77static int init_property_area(void)
78{
79    if (property_area_inited)
80        return -1;
81
82    if(__system_property_area_init())
83        return -1;
84
85    if(init_workspace(&pa_workspace, 0))
86        return -1;
87
88    fcntl(pa_workspace.fd, F_SETFD, FD_CLOEXEC);
89
90    property_area_inited = 1;
91    return 0;
92}
93
94static int check_mac_perms(const char *name, char *sctx)
95{
96    if (is_selinux_enabled() <= 0)
97        return 1;
98
99    char *tctx = NULL;
100    int result = 0;
101
102    if (!sctx)
103        goto err;
104
105    if (!sehandle_prop)
106        goto err;
107
108    if (selabel_lookup(sehandle_prop, &tctx, name, 1) != 0)
109        goto err;
110
111    if (selinux_check_access(sctx, tctx, "property_service", "set", (void*) name) == 0)
112        result = 1;
113
114    freecon(tctx);
115 err:
116    return result;
117}
118
119static int check_control_mac_perms(const char *name, char *sctx)
120{
121    /*
122     *  Create a name prefix out of ctl.<service name>
123     *  The new prefix allows the use of the existing
124     *  property service backend labeling while avoiding
125     *  mislabels based on true property prefixes.
126     */
127    char ctl_name[PROP_VALUE_MAX+4];
128    int ret = snprintf(ctl_name, sizeof(ctl_name), "ctl.%s", name);
129
130    if (ret < 0 || (size_t) ret >= sizeof(ctl_name))
131        return 0;
132
133    return check_mac_perms(ctl_name, sctx);
134}
135
136/*
137 * Checks permissions for setting system properties.
138 * Returns 1 if uid allowed, 0 otherwise.
139 */
140static int check_perms(const char *name, char *sctx)
141{
142    if(!strncmp(name, "ro.", 3))
143        name +=3;
144
145    return check_mac_perms(name, sctx);
146}
147
148int __property_get(const char *name, char *value)
149{
150    return __system_property_get(name, value);
151}
152
153static void write_persistent_property(const char *name, const char *value)
154{
155    char tempPath[PATH_MAX];
156    char path[PATH_MAX];
157    int fd;
158
159    snprintf(tempPath, sizeof(tempPath), "%s/.temp.XXXXXX", PERSISTENT_PROPERTY_DIR);
160    fd = mkstemp(tempPath);
161    if (fd < 0) {
162        ERROR("Unable to write persistent property to temp file %s errno: %d\n", tempPath, errno);
163        return;
164    }
165    write(fd, value, strlen(value));
166    fsync(fd);
167    close(fd);
168
169    snprintf(path, sizeof(path), "%s/%s", PERSISTENT_PROPERTY_DIR, name);
170    if (rename(tempPath, path)) {
171        unlink(tempPath);
172        ERROR("Unable to rename persistent property file %s to %s\n", tempPath, path);
173    }
174}
175
176static bool is_legal_property_name(const char* name, size_t namelen)
177{
178    size_t i;
179    if (namelen >= PROP_NAME_MAX) return false;
180    if (namelen < 1) return false;
181    if (name[0] == '.') return false;
182    if (name[namelen - 1] == '.') return false;
183
184    /* Only allow alphanumeric, plus '.', '-', or '_' */
185    /* Don't allow ".." to appear in a property name */
186    for (i = 0; i < namelen; i++) {
187        if (name[i] == '.') {
188            // i=0 is guaranteed to never have a dot. See above.
189            if (name[i-1] == '.') return false;
190            continue;
191        }
192        if (name[i] == '_' || name[i] == '-') continue;
193        if (name[i] >= 'a' && name[i] <= 'z') continue;
194        if (name[i] >= 'A' && name[i] <= 'Z') continue;
195        if (name[i] >= '0' && name[i] <= '9') continue;
196        return false;
197    }
198
199    return true;
200}
201
202static int property_set_impl(const char* name, const char* value) {
203    size_t namelen = strlen(name);
204    size_t valuelen = strlen(value);
205
206    if (!is_legal_property_name(name, namelen)) return -1;
207    if (valuelen >= PROP_VALUE_MAX) return -1;
208
209    prop_info* pi = (prop_info*) __system_property_find(name);
210
211    if(pi != 0) {
212        /* ro.* properties may NEVER be modified once set */
213        if(!strncmp(name, "ro.", 3)) return -1;
214
215        __system_property_update(pi, value, valuelen);
216    } else {
217        int rc = __system_property_add(name, namelen, value, valuelen);
218        if (rc < 0) {
219            return rc;
220        }
221    }
222    /* If name starts with "net." treat as a DNS property. */
223    if (strncmp("net.", name, strlen("net.")) == 0)  {
224        if (strcmp("net.change", name) == 0) {
225            return 0;
226        }
227       /*
228        * The 'net.change' property is a special property used track when any
229        * 'net.*' property name is updated. It is _ONLY_ updated here. Its value
230        * contains the last updated 'net.*' property.
231        */
232        property_set("net.change", name);
233    } else if (persistent_properties_loaded &&
234            strncmp("persist.", name, strlen("persist.")) == 0) {
235        /*
236         * Don't write properties to disk until after we have read all default properties
237         * to prevent them from being overwritten by default values.
238         */
239        write_persistent_property(name, value);
240    } else if (strcmp("selinux.reload_policy", name) == 0 &&
241               strcmp("1", value) == 0) {
242        selinux_reload_policy();
243    }
244    property_changed(name, value);
245    return 0;
246}
247
248int property_set(const char* name, const char* value) {
249    int rc = property_set_impl(name, value);
250    if (rc == -1) {
251        ERROR("property_set(\"%s\", \"%s\" failed\n", name, value);
252    }
253    return rc;
254}
255
256void handle_property_set_fd()
257{
258    prop_msg msg;
259    int s;
260    int r;
261    struct ucred cr;
262    struct sockaddr_un addr;
263    socklen_t addr_size = sizeof(addr);
264    socklen_t cr_size = sizeof(cr);
265    char * source_ctx = NULL;
266    struct pollfd ufds[1];
267    const int timeout_ms = 2 * 1000;  /* Default 2 sec timeout for caller to send property. */
268    int nr;
269
270    if ((s = accept(property_set_fd, (struct sockaddr *) &addr, &addr_size)) < 0) {
271        return;
272    }
273
274    /* Check socket options here */
275    if (getsockopt(s, SOL_SOCKET, SO_PEERCRED, &cr, &cr_size) < 0) {
276        close(s);
277        ERROR("Unable to receive socket options\n");
278        return;
279    }
280
281    ufds[0].fd = s;
282    ufds[0].events = POLLIN;
283    ufds[0].revents = 0;
284    nr = TEMP_FAILURE_RETRY(poll(ufds, 1, timeout_ms));
285    if (nr == 0) {
286        ERROR("sys_prop: timeout waiting for uid=%d to send property message.\n", cr.uid);
287        close(s);
288        return;
289    } else if (nr < 0) {
290        ERROR("sys_prop: error waiting for uid=%d to send property message. err=%d %s\n", cr.uid, errno, strerror(errno));
291        close(s);
292        return;
293    }
294
295    r = TEMP_FAILURE_RETRY(recv(s, &msg, sizeof(msg), MSG_DONTWAIT));
296    if(r != sizeof(prop_msg)) {
297        ERROR("sys_prop: mis-match msg size received: %d expected: %zu errno: %d\n",
298              r, sizeof(prop_msg), errno);
299        close(s);
300        return;
301    }
302
303    switch(msg.cmd) {
304    case PROP_MSG_SETPROP:
305        msg.name[PROP_NAME_MAX-1] = 0;
306        msg.value[PROP_VALUE_MAX-1] = 0;
307
308        if (!is_legal_property_name(msg.name, strlen(msg.name))) {
309            ERROR("sys_prop: illegal property name. Got: \"%s\"\n", msg.name);
310            close(s);
311            return;
312        }
313
314        getpeercon(s, &source_ctx);
315
316        if(memcmp(msg.name,"ctl.",4) == 0) {
317            // Keep the old close-socket-early behavior when handling
318            // ctl.* properties.
319            close(s);
320            if (check_control_mac_perms(msg.value, source_ctx)) {
321                handle_control_message((char*) msg.name + 4, (char*) msg.value);
322            } else {
323                ERROR("sys_prop: Unable to %s service ctl [%s] uid:%d gid:%d pid:%d\n",
324                        msg.name + 4, msg.value, cr.uid, cr.gid, cr.pid);
325            }
326        } else {
327            if (check_perms(msg.name, source_ctx)) {
328                property_set((char*) msg.name, (char*) msg.value);
329            } else {
330                ERROR("sys_prop: permission denied uid:%d  name:%s\n",
331                      cr.uid, msg.name);
332            }
333
334            // Note: bionic's property client code assumes that the
335            // property server will not close the socket until *AFTER*
336            // the property is written to memory.
337            close(s);
338        }
339        freecon(source_ctx);
340        break;
341
342    default:
343        close(s);
344        break;
345    }
346}
347
348void get_property_workspace(int *fd, int *sz)
349{
350    *fd = pa_workspace.fd;
351    *sz = pa_workspace.size;
352}
353
354static void load_properties_from_file(const char *, const char *);
355
356/*
357 * Filter is used to decide which properties to load: NULL loads all keys,
358 * "ro.foo.*" is a prefix match, and "ro.foo.bar" is an exact match.
359 */
360static void load_properties(char *data, const char *filter)
361{
362    char *key, *value, *eol, *sol, *tmp, *fn;
363    size_t flen = 0;
364
365    if (filter) {
366        flen = strlen(filter);
367    }
368
369    sol = data;
370    while ((eol = strchr(sol, '\n'))) {
371        key = sol;
372        *eol++ = 0;
373        sol = eol;
374
375        while (isspace(*key)) key++;
376        if (*key == '#') continue;
377
378        tmp = eol - 2;
379        while ((tmp > key) && isspace(*tmp)) *tmp-- = 0;
380
381        if (!strncmp(key, "import ", 7) && flen == 0) {
382            fn = key + 7;
383            while (isspace(*fn)) fn++;
384
385            key = strchr(fn, ' ');
386            if (key) {
387                *key++ = 0;
388                while (isspace(*key)) key++;
389            }
390
391            load_properties_from_file(fn, key);
392
393        } else {
394            value = strchr(key, '=');
395            if (!value) continue;
396            *value++ = 0;
397
398            tmp = value - 2;
399            while ((tmp > key) && isspace(*tmp)) *tmp-- = 0;
400
401            while (isspace(*value)) value++;
402
403            if (flen > 0) {
404                if (filter[flen - 1] == '*') {
405                    if (strncmp(key, filter, flen - 1)) continue;
406                } else {
407                    if (strcmp(key, filter)) continue;
408                }
409            }
410
411            property_set(key, value);
412        }
413    }
414}
415
416/*
417 * Filter is used to decide which properties to load: NULL loads all keys,
418 * "ro.foo.*" is a prefix match, and "ro.foo.bar" is an exact match.
419 */
420static void load_properties_from_file(const char *fn, const char *filter)
421{
422    std::string data;
423    if (read_file(fn, &data)) {
424        load_properties(&data[0], filter);
425    }
426}
427
428static void load_persistent_properties()
429{
430    DIR* dir = opendir(PERSISTENT_PROPERTY_DIR);
431    int dir_fd;
432    struct dirent*  entry;
433    char value[PROP_VALUE_MAX];
434    int fd, length;
435    struct stat sb;
436
437    if (dir) {
438        dir_fd = dirfd(dir);
439        while ((entry = readdir(dir)) != NULL) {
440            if (strncmp("persist.", entry->d_name, strlen("persist.")))
441                continue;
442            if (entry->d_type != DT_REG)
443                continue;
444            /* open the file and read the property value */
445            fd = openat(dir_fd, entry->d_name, O_RDONLY | O_NOFOLLOW);
446            if (fd < 0) {
447                ERROR("Unable to open persistent property file \"%s\" errno: %d\n",
448                      entry->d_name, errno);
449                continue;
450            }
451            if (fstat(fd, &sb) < 0) {
452                ERROR("fstat on property file \"%s\" failed errno: %d\n", entry->d_name, errno);
453                close(fd);
454                continue;
455            }
456
457            // File must not be accessible to others, be owned by root/root, and
458            // not be a hard link to any other file.
459            if (((sb.st_mode & (S_IRWXG | S_IRWXO)) != 0)
460                    || (sb.st_uid != 0)
461                    || (sb.st_gid != 0)
462                    || (sb.st_nlink != 1)) {
463                ERROR("skipping insecure property file %s (uid=%u gid=%u nlink=%u mode=%o)\n",
464                      entry->d_name, (unsigned int)sb.st_uid, (unsigned int)sb.st_gid,
465                      (unsigned int)sb.st_nlink, sb.st_mode);
466                close(fd);
467                continue;
468            }
469
470            length = read(fd, value, sizeof(value) - 1);
471            if (length >= 0) {
472                value[length] = 0;
473                property_set(entry->d_name, value);
474            } else {
475                ERROR("Unable to read persistent property file %s errno: %d\n",
476                      entry->d_name, errno);
477            }
478            close(fd);
479        }
480        closedir(dir);
481    } else {
482        ERROR("Unable to open persistent property directory %s errno: %d\n", PERSISTENT_PROPERTY_DIR, errno);
483    }
484
485    persistent_properties_loaded = 1;
486}
487
488void property_init(void)
489{
490    init_property_area();
491}
492
493void property_load_boot_defaults(void)
494{
495    load_properties_from_file(PROP_PATH_RAMDISK_DEFAULT, NULL);
496}
497
498int properties_inited(void)
499{
500    return property_area_inited;
501}
502
503static void load_override_properties() {
504    if (ALLOW_LOCAL_PROP_OVERRIDE) {
505        char debuggable[PROP_VALUE_MAX];
506        int ret = property_get("ro.debuggable", debuggable);
507        if (ret && (strcmp(debuggable, "1") == 0)) {
508            load_properties_from_file(PROP_PATH_LOCAL_OVERRIDE, NULL);
509        }
510    }
511}
512
513
514/* When booting an encrypted system, /data is not mounted when the
515 * property service is started, so any properties stored there are
516 * not loaded.  Vold triggers init to load these properties once it
517 * has mounted /data.
518 */
519void load_persist_props(void)
520{
521    load_override_properties();
522    /* Read persistent properties after all default values have been loaded. */
523    load_persistent_properties();
524}
525
526void load_all_props(void)
527{
528    load_properties_from_file(PROP_PATH_SYSTEM_BUILD, NULL);
529    load_properties_from_file(PROP_PATH_SYSTEM_DEFAULT, NULL);
530    load_properties_from_file(PROP_PATH_VENDOR_BUILD, NULL);
531    load_properties_from_file(PROP_PATH_BOOTIMAGE_BUILD, NULL);
532    load_properties_from_file(PROP_PATH_FACTORY, "ro.*");
533
534    load_override_properties();
535
536    /* Read persistent properties after all default values have been loaded. */
537    load_persistent_properties();
538}
539
540void start_property_service(void)
541{
542    int fd;
543
544    fd = create_socket(PROP_SERVICE_NAME, SOCK_STREAM, 0666, 0, 0, NULL);
545    if(fd < 0) return;
546    fcntl(fd, F_SETFD, FD_CLOEXEC);
547    fcntl(fd, F_SETFL, O_NONBLOCK);
548
549    listen(fd, 8);
550    property_set_fd = fd;
551}
552
553int get_property_set_fd()
554{
555    return property_set_fd;
556}
557