property_service.c revision fd7ffb1089cf3ce43a33a157ed748641adb7b95b 
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    int fd;
116} workspace;
117
118static int init_workspace(workspace *w, size_t size)
119{
120    void *data;
121    int fd;
122
123        /* dev is a tmpfs that we can use to carve a shared workspace
124         * out of, so let's do that...
125         */
126    fd = open("/dev/__properties__", O_RDWR | O_CREAT | O_NOFOLLOW, 0600);
127    if (fd < 0)
128        return -1;
129
130    if (ftruncate(fd, size) < 0)
131        goto out;
132
133    data = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
134    if(data == MAP_FAILED)
135        goto out;
136
137    close(fd);
138
139    fd = open("/dev/__properties__", O_RDONLY | O_NOFOLLOW);
140    if (fd < 0)
141        return -1;
142
143    unlink("/dev/__properties__");
144
145    w->data = data;
146    w->size = size;
147    w->fd = fd;
148    return 0;
149
150out:
151    close(fd);
152    return -1;
153}
154
155/* (8 header words + 247 toc words) = 1020 bytes */
156/* 1024 bytes header and toc + 247 prop_infos @ 128 bytes = 32640 bytes */
157
158#define PA_COUNT_MAX  247
159#define PA_INFO_START 1024
160#define PA_SIZE       32768
161
162static workspace pa_workspace;
163static prop_info *pa_info_array;
164
165extern prop_area *__system_property_area__;
166
167static int init_property_area(void)
168{
169    prop_area *pa;
170
171    if(pa_info_array)
172        return -1;
173
174    if(init_workspace(&pa_workspace, PA_SIZE))
175        return -1;
176
177    fcntl(pa_workspace.fd, F_SETFD, FD_CLOEXEC);
178
179    pa_info_array = (void*) (((char*) pa_workspace.data) + PA_INFO_START);
180
181    pa = pa_workspace.data;
182    memset(pa, 0, PA_SIZE);
183    pa->magic = PROP_AREA_MAGIC;
184    pa->version = PROP_AREA_VERSION;
185
186        /* plug into the lib property services */
187    __system_property_area__ = pa;
188    property_area_inited = 1;
189    return 0;
190}
191
192static void update_prop_info(prop_info *pi, const char *value, unsigned len)
193{
194    pi->serial = pi->serial | 1;
195    memcpy(pi->value, value, len + 1);
196    pi->serial = (len << 24) | ((pi->serial + 1) & 0xffffff);
197    __futex_wake(&pi->serial, INT32_MAX);
198}
199
200static int check_mac_perms(const char *name, char *sctx)
201{
202    if (is_selinux_enabled() <= 0)
203        return 1;
204
205    char *tctx = NULL;
206    const char *class = "property_service";
207    const char *perm = "set";
208    int result = 0;
209
210    if (!sctx)
211        goto err;
212
213    if (!sehandle_prop)
214        goto err;
215
216    if (selabel_lookup(sehandle_prop, &tctx, name, 1) != 0)
217        goto err;
218
219    if (selinux_check_access(sctx, tctx, class, perm, name) == 0)
220        result = 1;
221
222    freecon(tctx);
223 err:
224    return result;
225}
226
227static int check_control_mac_perms(const char *name, char *sctx)
228{
229    /*
230     *  Create a name prefix out of ctl.<service name>
231     *  The new prefix allows the use of the existing
232     *  property service backend labeling while avoiding
233     *  mislabels based on true property prefixes.
234     */
235    char ctl_name[PROP_VALUE_MAX+4];
236    int ret = snprintf(ctl_name, sizeof(ctl_name), "ctl.%s", name);
237
238    if (ret < 0 || (size_t) ret >= sizeof(ctl_name))
239        return 0;
240
241    return check_mac_perms(ctl_name, sctx);
242}
243
244/*
245 * Checks permissions for starting/stoping system services.
246 * AID_SYSTEM and AID_ROOT are always allowed.
247 *
248 * Returns 1 if uid allowed, 0 otherwise.
249 */
250static int check_control_perms(const char *name, unsigned int uid, unsigned int gid, char *sctx) {
251
252    int i;
253    if (uid == AID_SYSTEM || uid == AID_ROOT)
254      return check_control_mac_perms(name, sctx);
255
256    /* Search the ACL */
257    for (i = 0; control_perms[i].service; i++) {
258        if (strcmp(control_perms[i].service, name) == 0) {
259            if ((uid && control_perms[i].uid == uid) ||
260                (gid && control_perms[i].gid == gid)) {
261                return check_control_mac_perms(name, sctx);
262            }
263        }
264    }
265    return 0;
266}
267
268/*
269 * Checks permissions for setting system properties.
270 * Returns 1 if uid allowed, 0 otherwise.
271 */
272static int check_perms(const char *name, unsigned int uid, unsigned int gid, char *sctx)
273{
274    int i;
275    if(!strncmp(name, "ro.", 3))
276        name +=3;
277
278    if (uid == 0)
279        return check_mac_perms(name, sctx);
280
281    for (i = 0; property_perms[i].prefix; i++) {
282        if (strncmp(property_perms[i].prefix, name,
283                    strlen(property_perms[i].prefix)) == 0) {
284            if ((uid && property_perms[i].uid == uid) ||
285                (gid && property_perms[i].gid == gid)) {
286
287                return check_mac_perms(name, sctx);
288            }
289        }
290    }
291
292    return 0;
293}
294
295const char* property_get(const char *name)
296{
297    prop_info *pi;
298
299    if(strlen(name) >= PROP_NAME_MAX) return 0;
300
301    pi = (prop_info*) __system_property_find(name);
302
303    if(pi != 0) {
304        return pi->value;
305    } else {
306        return 0;
307    }
308}
309
310static void write_persistent_property(const char *name, const char *value)
311{
312    char tempPath[PATH_MAX];
313    char path[PATH_MAX];
314    int fd;
315
316    snprintf(tempPath, sizeof(tempPath), "%s/.temp.XXXXXX", PERSISTENT_PROPERTY_DIR);
317    fd = mkstemp(tempPath);
318    if (fd < 0) {
319        ERROR("Unable to write persistent property to temp file %s errno: %d\n", tempPath, errno);
320        return;
321    }
322    write(fd, value, strlen(value));
323    close(fd);
324
325    snprintf(path, sizeof(path), "%s/%s", PERSISTENT_PROPERTY_DIR, name);
326    if (rename(tempPath, path)) {
327        unlink(tempPath);
328        ERROR("Unable to rename persistent property file %s to %s\n", tempPath, path);
329    }
330}
331
332int property_set(const char *name, const char *value)
333{
334    prop_area *pa;
335    prop_info *pi;
336
337    size_t namelen = strlen(name);
338    size_t valuelen = strlen(value);
339
340    if(namelen >= PROP_NAME_MAX) return -1;
341    if(valuelen >= PROP_VALUE_MAX) return -1;
342    if(namelen < 1) return -1;
343
344    pi = (prop_info*) __system_property_find(name);
345
346    if(pi != 0) {
347        /* ro.* properties may NEVER be modified once set */
348        if(!strncmp(name, "ro.", 3)) return -1;
349
350        pa = __system_property_area__;
351        update_prop_info(pi, value, valuelen);
352        pa->serial++;
353        __futex_wake(&pa->serial, INT32_MAX);
354    } else {
355        pa = __system_property_area__;
356        if(pa->count == PA_COUNT_MAX) {
357            ERROR("Failed to set '%s'='%s',  property pool is exhausted at %d entries",
358                    name, value, PA_COUNT_MAX);
359            return -1;
360        }
361
362        pi = pa_info_array + pa->count;
363        pi->serial = (valuelen << 24);
364        memcpy(pi->name, name, namelen + 1);
365        memcpy(pi->value, value, valuelen + 1);
366
367        pa->toc[pa->count] =
368            (namelen << 24) | (((unsigned) pi) - ((unsigned) pa));
369
370        pa->count++;
371        pa->serial++;
372        __futex_wake(&pa->serial, INT32_MAX);
373    }
374    /* If name starts with "net." treat as a DNS property. */
375    if (strncmp("net.", name, strlen("net.")) == 0)  {
376        if (strcmp("net.change", name) == 0) {
377            return 0;
378        }
379       /*
380        * The 'net.change' property is a special property used track when any
381        * 'net.*' property name is updated. It is _ONLY_ updated here. Its value
382        * contains the last updated 'net.*' property.
383        */
384        property_set("net.change", name);
385    } else if (persistent_properties_loaded &&
386            strncmp("persist.", name, strlen("persist.")) == 0) {
387        /*
388         * Don't write properties to disk until after we have read all default properties
389         * to prevent them from being overwritten by default values.
390         */
391        write_persistent_property(name, value);
392    } else if (strcmp("selinux.reload_policy", name) == 0 &&
393               strcmp("1", value) == 0) {
394        selinux_reload_policy();
395    }
396    property_changed(name, value);
397    return 0;
398}
399
400void handle_property_set_fd()
401{
402    prop_msg msg;
403    int s;
404    int r;
405    int res;
406    struct ucred cr;
407    struct sockaddr_un addr;
408    socklen_t addr_size = sizeof(addr);
409    socklen_t cr_size = sizeof(cr);
410    char * source_ctx = NULL;
411
412    if ((s = accept(property_set_fd, (struct sockaddr *) &addr, &addr_size)) < 0) {
413        return;
414    }
415
416    /* Check socket options here */
417    if (getsockopt(s, SOL_SOCKET, SO_PEERCRED, &cr, &cr_size) < 0) {
418        close(s);
419        ERROR("Unable to receive socket options\n");
420        return;
421    }
422
423    r = TEMP_FAILURE_RETRY(recv(s, &msg, sizeof(msg), 0));
424    if(r != sizeof(prop_msg)) {
425        ERROR("sys_prop: mis-match msg size received: %d expected: %d errno: %d\n",
426              r, sizeof(prop_msg), errno);
427        close(s);
428        return;
429    }
430
431    switch(msg.cmd) {
432    case PROP_MSG_SETPROP:
433        msg.name[PROP_NAME_MAX-1] = 0;
434        msg.value[PROP_VALUE_MAX-1] = 0;
435
436        getpeercon(s, &source_ctx);
437
438        if(memcmp(msg.name,"ctl.",4) == 0) {
439            // Keep the old close-socket-early behavior when handling
440            // ctl.* properties.
441            close(s);
442            if (check_control_perms(msg.value, cr.uid, cr.gid, source_ctx)) {
443                handle_control_message((char*) msg.name + 4, (char*) msg.value);
444            } else {
445                ERROR("sys_prop: Unable to %s service ctl [%s] uid:%d gid:%d pid:%d\n",
446                        msg.name + 4, msg.value, cr.uid, cr.gid, cr.pid);
447            }
448        } else {
449            if (check_perms(msg.name, cr.uid, cr.gid, source_ctx)) {
450                property_set((char*) msg.name, (char*) msg.value);
451            } else {
452                ERROR("sys_prop: permission denied uid:%d  name:%s\n",
453                      cr.uid, msg.name);
454            }
455
456            // Note: bionic's property client code assumes that the
457            // property server will not close the socket until *AFTER*
458            // the property is written to memory.
459            close(s);
460        }
461        freecon(source_ctx);
462        break;
463
464    default:
465        close(s);
466        break;
467    }
468}
469
470void get_property_workspace(int *fd, int *sz)
471{
472    *fd = pa_workspace.fd;
473    *sz = pa_workspace.size;
474}
475
476static void load_properties(char *data)
477{
478    char *key, *value, *eol, *sol, *tmp;
479
480    sol = data;
481    while((eol = strchr(sol, '\n'))) {
482        key = sol;
483        *eol++ = 0;
484        sol = eol;
485
486        value = strchr(key, '=');
487        if(value == 0) continue;
488        *value++ = 0;
489
490        while(isspace(*key)) key++;
491        if(*key == '#') continue;
492        tmp = value - 2;
493        while((tmp > key) && isspace(*tmp)) *tmp-- = 0;
494
495        while(isspace(*value)) value++;
496        tmp = eol - 2;
497        while((tmp > value) && isspace(*tmp)) *tmp-- = 0;
498
499        property_set(key, value);
500    }
501}
502
503static void load_properties_from_file(const char *fn)
504{
505    char *data;
506    unsigned sz;
507
508    data = read_file(fn, &sz);
509
510    if(data != 0) {
511        load_properties(data);
512        free(data);
513    }
514}
515
516static void load_persistent_properties()
517{
518    DIR* dir = opendir(PERSISTENT_PROPERTY_DIR);
519    int dir_fd;
520    struct dirent*  entry;
521    char value[PROP_VALUE_MAX];
522    int fd, length;
523    struct stat sb;
524
525    if (dir) {
526        dir_fd = dirfd(dir);
527        while ((entry = readdir(dir)) != NULL) {
528            if (strncmp("persist.", entry->d_name, strlen("persist.")))
529                continue;
530#if HAVE_DIRENT_D_TYPE
531            if (entry->d_type != DT_REG)
532                continue;
533#endif
534            /* open the file and read the property value */
535            fd = openat(dir_fd, entry->d_name, O_RDONLY | O_NOFOLLOW);
536            if (fd < 0) {
537                ERROR("Unable to open persistent property file \"%s\" errno: %d\n",
538                      entry->d_name, errno);
539                continue;
540            }
541            if (fstat(fd, &sb) < 0) {
542                ERROR("fstat on property file \"%s\" failed errno: %d\n", entry->d_name, errno);
543                close(fd);
544                continue;
545            }
546
547            // File must not be accessible to others, be owned by root/root, and
548            // not be a hard link to any other file.
549            if (((sb.st_mode & (S_IRWXG | S_IRWXO)) != 0)
550                    || (sb.st_uid != 0)
551                    || (sb.st_gid != 0)
552                    || (sb.st_nlink != 1)) {
553                ERROR("skipping insecure property file %s (uid=%lu gid=%lu nlink=%d mode=%o)\n",
554                      entry->d_name, sb.st_uid, sb.st_gid, sb.st_nlink, sb.st_mode);
555                close(fd);
556                continue;
557            }
558
559            length = read(fd, value, sizeof(value) - 1);
560            if (length >= 0) {
561                value[length] = 0;
562                property_set(entry->d_name, value);
563            } else {
564                ERROR("Unable to read persistent property file %s errno: %d\n",
565                      entry->d_name, errno);
566            }
567            close(fd);
568        }
569        closedir(dir);
570    } else {
571        ERROR("Unable to open persistent property directory %s errno: %d\n", PERSISTENT_PROPERTY_DIR, errno);
572    }
573
574    persistent_properties_loaded = 1;
575}
576
577void property_init(void)
578{
579    init_property_area();
580}
581
582void property_load_boot_defaults(void)
583{
584    load_properties_from_file(PROP_PATH_RAMDISK_DEFAULT);
585}
586
587int properties_inited(void)
588{
589    return property_area_inited;
590}
591
592static void load_override_properties() {
593#ifdef ALLOW_LOCAL_PROP_OVERRIDE
594    const char *debuggable = property_get("ro.debuggable");
595    if (debuggable && (strcmp(debuggable, "1") == 0)) {
596        load_properties_from_file(PROP_PATH_LOCAL_OVERRIDE);
597    }
598#endif /* ALLOW_LOCAL_PROP_OVERRIDE */
599}
600
601
602/* When booting an encrypted system, /data is not mounted when the
603 * property service is started, so any properties stored there are
604 * not loaded.  Vold triggers init to load these properties once it
605 * has mounted /data.
606 */
607void load_persist_props(void)
608{
609    load_override_properties();
610    /* Read persistent properties after all default values have been loaded. */
611    load_persistent_properties();
612}
613
614void start_property_service(void)
615{
616    int fd;
617
618    load_properties_from_file(PROP_PATH_SYSTEM_BUILD);
619    load_properties_from_file(PROP_PATH_SYSTEM_DEFAULT);
620    load_override_properties();
621    /* Read persistent properties after all default values have been loaded. */
622    load_persistent_properties();
623
624    fd = create_socket(PROP_SERVICE_NAME, SOCK_STREAM, 0666, 0, 0);
625    if(fd < 0) return;
626    fcntl(fd, F_SETFD, FD_CLOEXEC);
627    fcntl(fd, F_SETFL, O_NONBLOCK);
628
629    listen(fd, 8);
630    property_set_fd = fd;
631}
632
633int get_property_set_fd()
634{
635    return property_set_fd;
636}
637