property_service.c revision 51e06618dbd87c4374c56d9193a5e567aa3d02ac 
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
28#include <cutils/misc.h>
29#include <cutils/sockets.h>
30
31#define _REALLY_INCLUDE_SYS__SYSTEM_PROPERTIES_H_
32#include <sys/_system_properties.h>
33
34#include <sys/socket.h>
35#include <sys/un.h>
36#include <sys/select.h>
37#include <sys/types.h>
38#include <netinet/in.h>
39#include <sys/mman.h>
40#include <sys/atomics.h>
41#include <private/android_filesystem_config.h>
42
43#include <selinux/selinux.h>
44#include <selinux/label.h>
45
46#include "property_service.h"
47#include "init.h"
48#include "util.h"
49#include "log.h"
50
51#define PERSISTENT_PROPERTY_DIR  "/data/property"
52
53static int persistent_properties_loaded = 0;
54static int property_area_inited = 0;
55
56static int property_set_fd = -1;
57
58/* White list of permissions for setting property services. */
59struct {
60    const char *prefix;
61    unsigned int uid;
62    unsigned int gid;
63} property_perms[] = {
64    { "net.rmnet0.",      AID_RADIO,    0 },
65    { "net.gprs.",        AID_RADIO,    0 },
66    { "net.ppp",          AID_RADIO,    0 },
67    { "net.qmi",          AID_RADIO,    0 },
68    { "net.lte",          AID_RADIO,    0 },
69    { "net.cdma",         AID_RADIO,    0 },
70    { "ril.",             AID_RADIO,    0 },
71    { "gsm.",             AID_RADIO,    0 },
72    { "persist.radio",    AID_RADIO,    0 },
73    { "net.dns",          AID_RADIO,    0 },
74    { "sys.usb.config",   AID_RADIO,    0 },
75    { "net.",             AID_SYSTEM,   0 },
76    { "dev.",             AID_SYSTEM,   0 },
77    { "runtime.",         AID_SYSTEM,   0 },
78    { "hw.",              AID_SYSTEM,   0 },
79    { "sys.",             AID_SYSTEM,   0 },
80    { "service.",         AID_SYSTEM,   0 },
81    { "wlan.",            AID_SYSTEM,   0 },
82    { "bluetooth.",       AID_BLUETOOTH,   0 },
83    { "dhcp.",            AID_SYSTEM,   0 },
84    { "dhcp.",            AID_DHCP,     0 },
85    { "debug.",           AID_SYSTEM,   0 },
86    { "debug.",           AID_SHELL,    0 },
87    { "log.",             AID_SHELL,    0 },
88    { "service.adb.root", AID_SHELL,    0 },
89    { "service.adb.tcp.port", AID_SHELL,    0 },
90    { "persist.sys.",     AID_SYSTEM,   0 },
91    { "persist.service.", AID_SYSTEM,   0 },
92    { "persist.security.", AID_SYSTEM,   0 },
93    { "persist.service.bdroid.", AID_BLUETOOTH,   0 },
94    { "selinux."         , AID_SYSTEM,   0 },
95    { NULL, 0, 0 }
96};
97
98/*
99 * White list of UID that are allowed to start/stop services.
100 * Currently there are no user apps that require.
101 */
102struct {
103    const char *service;
104    unsigned int uid;
105    unsigned int gid;
106} control_perms[] = {
107    { "dumpstate",AID_SHELL, AID_LOG },
108    { "ril-daemon",AID_RADIO, AID_RADIO },
109     {NULL, 0, 0 }
110};
111
112typedef struct {
113    void *data;
114    size_t size;
115} workspace;
116
117static int init_workspace(workspace *w, size_t size)
118{
119    void *data;
120    int fd;
121
122    /* dev is a tmpfs that we can use to carve a shared workspace
123     * out of, so let's do that...
124     */
125    fd = open(PROP_FILENAME, O_RDWR | O_CREAT | O_NOFOLLOW, 0644);
126    if (fd < 0)
127        return -1;
128
129    if (ftruncate(fd, size) < 0)
130        goto out;
131
132    data = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
133    if(data == MAP_FAILED)
134        goto out;
135
136    close(fd);
137
138    w->data = data;
139    w->size = size;
140    return 0;
141
142out:
143    close(fd);
144    return -1;
145}
146
147/* (8 header words + 247 toc words) = 1020 bytes */
148/* 1024 bytes header and toc + 247 prop_infos @ 128 bytes = 32640 bytes */
149
150#define PA_COUNT_MAX  247
151#define PA_INFO_START 1024
152#define PA_SIZE       32768
153
154static workspace pa_workspace;
155static prop_info *pa_info_array;
156
157extern prop_area *__system_property_area__;
158
159static int init_property_area(void)
160{
161    prop_area *pa;
162
163    if(pa_info_array)
164        return -1;
165
166    if(init_workspace(&pa_workspace, PA_SIZE))
167        return -1;
168
169    pa_info_array = (void*) (((char*) pa_workspace.data) + PA_INFO_START);
170
171    pa = pa_workspace.data;
172    memset(pa, 0, PA_SIZE);
173    pa->magic = PROP_AREA_MAGIC;
174    pa->version = PROP_AREA_VERSION;
175
176        /* plug into the lib property services */
177    __system_property_area__ = pa;
178    property_area_inited = 1;
179    return 0;
180}
181
182static void update_prop_info(prop_info *pi, const char *value, unsigned len)
183{
184    pi->serial = pi->serial | 1;
185    memcpy(pi->value, value, len + 1);
186    pi->serial = (len << 24) | ((pi->serial + 1) & 0xffffff);
187    __futex_wake(&pi->serial, INT32_MAX);
188}
189
190static int check_mac_perms(const char *name, char *sctx)
191{
192    if (is_selinux_enabled() <= 0)
193        return 1;
194
195    char *tctx = NULL;
196    const char *class = "property_service";
197    const char *perm = "set";
198    int result = 0;
199
200    if (!sctx)
201        goto err;
202
203    if (!sehandle_prop)
204        goto err;
205
206    if (selabel_lookup(sehandle_prop, &tctx, name, 1) != 0)
207        goto err;
208
209    if (selinux_check_access(sctx, tctx, class, perm, name) == 0)
210        result = 1;
211
212    freecon(tctx);
213 err:
214    return result;
215}
216
217static int check_control_mac_perms(const char *name, char *sctx)
218{
219    /*
220     *  Create a name prefix out of ctl.<service name>
221     *  The new prefix allows the use of the existing
222     *  property service backend labeling while avoiding
223     *  mislabels based on true property prefixes.
224     */
225    char ctl_name[PROP_VALUE_MAX+4];
226    int ret = snprintf(ctl_name, sizeof(ctl_name), "ctl.%s", name);
227
228    if (ret < 0 || (size_t) ret >= sizeof(ctl_name))
229        return 0;
230
231    return check_mac_perms(ctl_name, sctx);
232}
233
234/*
235 * Checks permissions for starting/stoping system services.
236 * AID_SYSTEM and AID_ROOT are always allowed.
237 *
238 * Returns 1 if uid allowed, 0 otherwise.
239 */
240static int check_control_perms(const char *name, unsigned int uid, unsigned int gid, char *sctx) {
241
242    int i;
243    if (uid == AID_SYSTEM || uid == AID_ROOT)
244      return check_control_mac_perms(name, sctx);
245
246    /* Search the ACL */
247    for (i = 0; control_perms[i].service; i++) {
248        if (strcmp(control_perms[i].service, name) == 0) {
249            if ((uid && control_perms[i].uid == uid) ||
250                (gid && control_perms[i].gid == gid)) {
251                return check_control_mac_perms(name, sctx);
252            }
253        }
254    }
255    return 0;
256}
257
258/*
259 * Checks permissions for setting system properties.
260 * Returns 1 if uid allowed, 0 otherwise.
261 */
262static int check_perms(const char *name, unsigned int uid, unsigned int gid, char *sctx)
263{
264    int i;
265    if(!strncmp(name, "ro.", 3))
266        name +=3;
267
268    if (uid == 0)
269        return check_mac_perms(name, sctx);
270
271    for (i = 0; property_perms[i].prefix; i++) {
272        if (strncmp(property_perms[i].prefix, name,
273                    strlen(property_perms[i].prefix)) == 0) {
274            if ((uid && property_perms[i].uid == uid) ||
275                (gid && property_perms[i].gid == gid)) {
276
277                return check_mac_perms(name, sctx);
278            }
279        }
280    }
281
282    return 0;
283}
284
285const char* property_get(const char *name)
286{
287    prop_info *pi;
288
289    if(strlen(name) >= PROP_NAME_MAX) return 0;
290
291    pi = (prop_info*) __system_property_find(name);
292
293    if(pi != 0) {
294        return pi->value;
295    } else {
296        return 0;
297    }
298}
299
300static void write_persistent_property(const char *name, const char *value)
301{
302    char tempPath[PATH_MAX];
303    char path[PATH_MAX];
304    int fd;
305
306    snprintf(tempPath, sizeof(tempPath), "%s/.temp.XXXXXX", PERSISTENT_PROPERTY_DIR);
307    fd = mkstemp(tempPath);
308    if (fd < 0) {
309        ERROR("Unable to write persistent property to temp file %s errno: %d\n", tempPath, errno);
310        return;
311    }
312    write(fd, value, strlen(value));
313    close(fd);
314
315    snprintf(path, sizeof(path), "%s/%s", PERSISTENT_PROPERTY_DIR, name);
316    if (rename(tempPath, path)) {
317        unlink(tempPath);
318        ERROR("Unable to rename persistent property file %s to %s\n", tempPath, path);
319    }
320}
321
322int property_set(const char *name, const char *value)
323{
324    prop_area *pa;
325    prop_info *pi;
326
327    size_t namelen = strlen(name);
328    size_t valuelen = strlen(value);
329
330    if(namelen >= PROP_NAME_MAX) return -1;
331    if(valuelen >= PROP_VALUE_MAX) return -1;
332    if(namelen < 1) return -1;
333
334    pi = (prop_info*) __system_property_find(name);
335
336    if(pi != 0) {
337        /* ro.* properties may NEVER be modified once set */
338        if(!strncmp(name, "ro.", 3)) return -1;
339
340        pa = __system_property_area__;
341        update_prop_info(pi, value, valuelen);
342        pa->serial++;
343        __futex_wake(&pa->serial, INT32_MAX);
344    } else {
345        pa = __system_property_area__;
346        if(pa->count == PA_COUNT_MAX) return -1;
347
348        pi = pa_info_array + pa->count;
349        pi->serial = (valuelen << 24);
350        memcpy(pi->name, name, namelen + 1);
351        memcpy(pi->value, value, valuelen + 1);
352
353        pa->toc[pa->count] =
354            (namelen << 24) | (((unsigned) pi) - ((unsigned) pa));
355
356        pa->count++;
357        pa->serial++;
358        __futex_wake(&pa->serial, INT32_MAX);
359    }
360    /* If name starts with "net." treat as a DNS property. */
361    if (strncmp("net.", name, strlen("net.")) == 0)  {
362        if (strcmp("net.change", name) == 0) {
363            return 0;
364        }
365       /*
366        * The 'net.change' property is a special property used track when any
367        * 'net.*' property name is updated. It is _ONLY_ updated here. Its value
368        * contains the last updated 'net.*' property.
369        */
370        property_set("net.change", name);
371    } else if (persistent_properties_loaded &&
372            strncmp("persist.", name, strlen("persist.")) == 0) {
373        /*
374         * Don't write properties to disk until after we have read all default properties
375         * to prevent them from being overwritten by default values.
376         */
377        write_persistent_property(name, value);
378    } else if (strcmp("selinux.reload_policy", name) == 0 &&
379               strcmp("1", value) == 0) {
380        selinux_reload_policy();
381    }
382    property_changed(name, value);
383    return 0;
384}
385
386void handle_property_set_fd()
387{
388    prop_msg msg;
389    int s;
390    int r;
391    int res;
392    struct ucred cr;
393    struct sockaddr_un addr;
394    socklen_t addr_size = sizeof(addr);
395    socklen_t cr_size = sizeof(cr);
396    char * source_ctx = NULL;
397
398    if ((s = accept(property_set_fd, (struct sockaddr *) &addr, &addr_size)) < 0) {
399        return;
400    }
401
402    /* Check socket options here */
403    if (getsockopt(s, SOL_SOCKET, SO_PEERCRED, &cr, &cr_size) < 0) {
404        close(s);
405        ERROR("Unable to receive socket options\n");
406        return;
407    }
408
409    r = TEMP_FAILURE_RETRY(recv(s, &msg, sizeof(msg), 0));
410    if(r != sizeof(prop_msg)) {
411        ERROR("sys_prop: mis-match msg size received: %d expected: %d errno: %d\n",
412              r, sizeof(prop_msg), errno);
413        close(s);
414        return;
415    }
416
417    switch(msg.cmd) {
418    case PROP_MSG_SETPROP:
419        msg.name[PROP_NAME_MAX-1] = 0;
420        msg.value[PROP_VALUE_MAX-1] = 0;
421
422        getpeercon(s, &source_ctx);
423
424        if(memcmp(msg.name,"ctl.",4) == 0) {
425            // Keep the old close-socket-early behavior when handling
426            // ctl.* properties.
427            close(s);
428            if (check_control_perms(msg.value, cr.uid, cr.gid, source_ctx)) {
429                handle_control_message((char*) msg.name + 4, (char*) msg.value);
430            } else {
431                ERROR("sys_prop: Unable to %s service ctl [%s] uid:%d gid:%d pid:%d\n",
432                        msg.name + 4, msg.value, cr.uid, cr.gid, cr.pid);
433            }
434        } else {
435            if (check_perms(msg.name, cr.uid, cr.gid, source_ctx)) {
436                property_set((char*) msg.name, (char*) msg.value);
437            } else {
438                ERROR("sys_prop: permission denied uid:%d  name:%s\n",
439                      cr.uid, msg.name);
440            }
441
442            // Note: bionic's property client code assumes that the
443            // property server will not close the socket until *AFTER*
444            // the property is written to memory.
445            close(s);
446        }
447        freecon(source_ctx);
448        break;
449
450    default:
451        close(s);
452        break;
453    }
454}
455
456static void load_properties(char *data)
457{
458    char *key, *value, *eol, *sol, *tmp;
459
460    sol = data;
461    while((eol = strchr(sol, '\n'))) {
462        key = sol;
463        *eol++ = 0;
464        sol = eol;
465
466        value = strchr(key, '=');
467        if(value == 0) continue;
468        *value++ = 0;
469
470        while(isspace(*key)) key++;
471        if(*key == '#') continue;
472        tmp = value - 2;
473        while((tmp > key) && isspace(*tmp)) *tmp-- = 0;
474
475        while(isspace(*value)) value++;
476        tmp = eol - 2;
477        while((tmp > value) && isspace(*tmp)) *tmp-- = 0;
478
479        property_set(key, value);
480    }
481}
482
483static void load_properties_from_file(const char *fn)
484{
485    char *data;
486    unsigned sz;
487
488    data = read_file(fn, &sz);
489
490    if(data != 0) {
491        load_properties(data);
492        free(data);
493    }
494}
495
496static void load_persistent_properties()
497{
498    DIR* dir = opendir(PERSISTENT_PROPERTY_DIR);
499    int dir_fd;
500    struct dirent*  entry;
501    char value[PROP_VALUE_MAX];
502    int fd, length;
503    struct stat sb;
504
505    if (dir) {
506        dir_fd = dirfd(dir);
507        while ((entry = readdir(dir)) != NULL) {
508            if (strncmp("persist.", entry->d_name, strlen("persist.")))
509                continue;
510#if HAVE_DIRENT_D_TYPE
511            if (entry->d_type != DT_REG)
512                continue;
513#endif
514            /* open the file and read the property value */
515            fd = openat(dir_fd, entry->d_name, O_RDONLY | O_NOFOLLOW);
516            if (fd < 0) {
517                ERROR("Unable to open persistent property file \"%s\" errno: %d\n",
518                      entry->d_name, errno);
519                continue;
520            }
521            if (fstat(fd, &sb) < 0) {
522                ERROR("fstat on property file \"%s\" failed errno: %d\n", entry->d_name, errno);
523                close(fd);
524                continue;
525            }
526
527            // File must not be accessible to others, be owned by root/root, and
528            // not be a hard link to any other file.
529            if (((sb.st_mode & (S_IRWXG | S_IRWXO)) != 0)
530                    || (sb.st_uid != 0)
531                    || (sb.st_gid != 0)
532                    || (sb.st_nlink != 1)) {
533                ERROR("skipping insecure property file %s (uid=%lu gid=%lu nlink=%d mode=%o)\n",
534                      entry->d_name, sb.st_uid, sb.st_gid, sb.st_nlink, sb.st_mode);
535                close(fd);
536                continue;
537            }
538
539            length = read(fd, value, sizeof(value) - 1);
540            if (length >= 0) {
541                value[length] = 0;
542                property_set(entry->d_name, value);
543            } else {
544                ERROR("Unable to read persistent property file %s errno: %d\n",
545                      entry->d_name, errno);
546            }
547            close(fd);
548        }
549        closedir(dir);
550    } else {
551        ERROR("Unable to open persistent property directory %s errno: %d\n", PERSISTENT_PROPERTY_DIR, errno);
552    }
553
554    persistent_properties_loaded = 1;
555}
556
557void property_init(void)
558{
559    init_property_area();
560}
561
562void property_load_boot_defaults(void)
563{
564    load_properties_from_file(PROP_PATH_RAMDISK_DEFAULT);
565}
566
567int properties_inited(void)
568{
569    return property_area_inited;
570}
571
572static void load_override_properties() {
573#ifdef ALLOW_LOCAL_PROP_OVERRIDE
574    const char *debuggable = property_get("ro.debuggable");
575    if (debuggable && (strcmp(debuggable, "1") == 0)) {
576        load_properties_from_file(PROP_PATH_LOCAL_OVERRIDE);
577    }
578#endif /* ALLOW_LOCAL_PROP_OVERRIDE */
579}
580
581
582/* When booting an encrypted system, /data is not mounted when the
583 * property service is started, so any properties stored there are
584 * not loaded.  Vold triggers init to load these properties once it
585 * has mounted /data.
586 */
587void load_persist_props(void)
588{
589    load_override_properties();
590    /* Read persistent properties after all default values have been loaded. */
591    load_persistent_properties();
592}
593
594void start_property_service(void)
595{
596    int fd;
597
598    load_properties_from_file(PROP_PATH_SYSTEM_BUILD);
599    load_properties_from_file(PROP_PATH_SYSTEM_DEFAULT);
600    load_override_properties();
601    /* Read persistent properties after all default values have been loaded. */
602    load_persistent_properties();
603
604    fd = create_socket(PROP_SERVICE_NAME, SOCK_STREAM, 0666, 0, 0);
605    if(fd < 0) return;
606    fcntl(fd, F_SETFD, FD_CLOEXEC);
607    fcntl(fd, F_SETFL, O_NONBLOCK);
608
609    listen(fd, 8);
610    property_set_fd = fd;
611}
612
613int get_property_set_fd()
614{
615    return property_set_fd;
616}
617