property_service.c revision 4f6e8d7a00cbeda1e70cc15be9c4af1018bdad53 
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#include <cutils/ashmem.h>
31
32#define _REALLY_INCLUDE_SYS__SYSTEM_PROPERTIES_H_
33#include <sys/_system_properties.h>
34
35#include <sys/socket.h>
36#include <sys/un.h>
37#include <sys/select.h>
38#include <sys/types.h>
39#include <netinet/in.h>
40#include <sys/mman.h>
41#include <sys/atomics.h>
42#include <private/android_filesystem_config.h>
43
44#include "property_service.h"
45#include "init.h"
46
47#define PERSISTENT_PROPERTY_DIR  "/data/property"
48
49static int persistent_properties_loaded = 0;
50
51/* White list of permissions for setting property services. */
52struct {
53    const char *prefix;
54    unsigned int uid;
55} property_perms[] = {
56    { "net.rmnet0.",    AID_RADIO },
57    { "net.gprs.",      AID_RADIO },
58    { "ril.",           AID_RADIO },
59    { "gsm.",           AID_RADIO },
60    { "net.dns",        AID_RADIO },
61    { "net.",           AID_SYSTEM },
62    { "dev.",           AID_SYSTEM },
63    { "runtime.",       AID_SYSTEM },
64    { "hw.",            AID_SYSTEM },
65    { "sys.",		AID_SYSTEM },
66    { "service.",	AID_SYSTEM },
67    { "wlan.",		AID_SYSTEM },
68    { "dhcp.",		AID_SYSTEM },
69    { "dhcp.",		AID_DHCP },
70    { "debug.",		AID_SHELL },
71    { "log.",		AID_SHELL },
72    { "persist.sys.",	AID_SYSTEM },
73    { "persist.service.",   AID_SYSTEM },
74    { NULL, 0 }
75};
76
77/*
78 * White list of UID that are allowed to start/stop services.
79 * Currently there are no user apps that require.
80 */
81struct {
82    const char *service;
83    unsigned int uid;
84} control_perms[] = {
85     {NULL, 0 }
86};
87
88typedef struct {
89    void *data;
90    size_t size;
91    int fd;
92} workspace;
93
94static int init_workspace(workspace *w, size_t size)
95{
96    void *data;
97    int fd;
98
99    fd = ashmem_create_region("system_properties", size);
100    if(fd < 0)
101        return -1;
102
103    data = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
104    if(data == MAP_FAILED)
105        goto out;
106
107    /* allow the wolves we share with to do nothing but read */
108    ashmem_set_prot_region(fd, PROT_READ);
109
110    w->data = data;
111    w->size = size;
112    w->fd = fd;
113
114    return 0;
115
116out:
117    close(fd);
118    return -1;
119}
120
121/* (8 header words + 247 toc words) = 1020 bytes */
122/* 1024 bytes header and toc + 247 prop_infos @ 128 bytes = 32640 bytes */
123
124#define PA_COUNT_MAX  247
125#define PA_INFO_START 1024
126#define PA_SIZE       32768
127
128static workspace pa_workspace;
129static prop_info *pa_info_array;
130
131extern prop_area *__system_property_area__;
132
133static int init_property_area(void)
134{
135    prop_area *pa;
136
137    if(pa_info_array)
138        return -1;
139
140    if(init_workspace(&pa_workspace, PA_SIZE))
141        return -1;
142
143    fcntl(pa_workspace.fd, F_SETFD, FD_CLOEXEC);
144
145    pa_info_array = (void*) (((char*) pa_workspace.data) + PA_INFO_START);
146
147    pa = pa_workspace.data;
148    memset(pa, 0, PA_SIZE);
149    pa->magic = PROP_AREA_MAGIC;
150    pa->version = PROP_AREA_VERSION;
151
152        /* plug into the lib property services */
153    __system_property_area__ = pa;
154
155    return 0;
156}
157
158static void update_prop_info(prop_info *pi, const char *value, unsigned len)
159{
160    pi->serial = pi->serial | 1;
161    memcpy(pi->value, value, len + 1);
162    pi->serial = (len << 24) | ((pi->serial + 1) & 0xffffff);
163    __futex_wake(&pi->serial, INT32_MAX);
164}
165
166static int property_write(prop_info *pi, const char *value)
167{
168    int valuelen = strlen(value);
169    if(valuelen >= PROP_VALUE_MAX) return -1;
170    update_prop_info(pi, value, valuelen);
171    return 0;
172}
173
174
175/*
176 * Checks permissions for starting/stoping system services.
177 * AID_SYSTEM and AID_ROOT are always allowed.
178 *
179 * Returns 1 if uid allowed, 0 otherwise.
180 */
181static int check_control_perms(const char *name, int uid) {
182    int i;
183    if (uid == AID_SYSTEM || uid == AID_ROOT)
184        return 1;
185
186    /* Search the ACL */
187    for (i = 0; control_perms[i].service; i++) {
188        if (strcmp(control_perms[i].service, name) == 0) {
189            if (control_perms[i].uid == uid)
190                return 1;
191        }
192    }
193    return 0;
194}
195
196/*
197 * Checks permissions for setting system properties.
198 * Returns 1 if uid allowed, 0 otherwise.
199 */
200static int check_perms(const char *name, unsigned int uid)
201{
202    int i;
203    if (uid == 0)
204        return 1;
205
206    if(!strncmp(name, "ro.", 3))
207        name +=3;
208
209    for (i = 0; property_perms[i].prefix; i++) {
210        int tmp;
211        if (strncmp(property_perms[i].prefix, name,
212                    strlen(property_perms[i].prefix)) == 0) {
213            if (property_perms[i].uid == uid) {
214                return 1;
215            }
216        }
217    }
218
219    return 0;
220}
221
222const char* property_get(const char *name)
223{
224    prop_info *pi;
225
226    if(strlen(name) >= PROP_NAME_MAX) return 0;
227
228    pi = (prop_info*) __system_property_find(name);
229
230    if(pi != 0) {
231        return pi->value;
232    } else {
233        return 0;
234    }
235}
236
237static void write_peristent_property(const char *name, const char *value)
238{
239    const char *tempPath = PERSISTENT_PROPERTY_DIR "/.temp";
240    char path[PATH_MAX];
241    int fd, length;
242
243    snprintf(path, sizeof(path), "%s/%s", PERSISTENT_PROPERTY_DIR, name);
244
245    fd = open(tempPath, O_WRONLY|O_CREAT|O_TRUNC, 0600);
246    if (fd < 0) {
247        ERROR("Unable to write persistent property to temp file %s errno: %d\n", tempPath, errno);
248        return;
249    }
250    write(fd, value, strlen(value));
251    close(fd);
252
253    if (rename(tempPath, path)) {
254        unlink(tempPath);
255        ERROR("Unable to rename persistent property file %s to %s\n", tempPath, path);
256    }
257}
258
259int property_set(const char *name, const char *value)
260{
261    prop_area *pa;
262    prop_info *pi;
263
264    int namelen = strlen(name);
265    int valuelen = strlen(value);
266
267    if(namelen >= PROP_NAME_MAX) return -1;
268    if(valuelen >= PROP_VALUE_MAX) return -1;
269    if(namelen < 1) return -1;
270
271    pi = (prop_info*) __system_property_find(name);
272
273    if(pi != 0) {
274        /* ro.* properties may NEVER be modified once set */
275        if(!strncmp(name, "ro.", 3)) return -1;
276
277        pa = __system_property_area__;
278        update_prop_info(pi, value, valuelen);
279        pa->serial++;
280        __futex_wake(&pa->serial, INT32_MAX);
281    } else {
282        pa = __system_property_area__;
283        if(pa->count == PA_COUNT_MAX) return -1;
284
285        pi = pa_info_array + pa->count;
286        pi->serial = (valuelen << 24);
287        memcpy(pi->name, name, namelen + 1);
288        memcpy(pi->value, value, valuelen + 1);
289
290        pa->toc[pa->count] =
291            (namelen << 24) | (((unsigned) pi) - ((unsigned) pa));
292
293        pa->count++;
294        pa->serial++;
295        __futex_wake(&pa->serial, INT32_MAX);
296    }
297    /* If name starts with "net." treat as a DNS property. */
298    if (strncmp("net.", name, sizeof("net.") - 1) == 0)  {
299        if (strcmp("net.change", name) == 0) {
300            return 0;
301        }
302       /*
303        * The 'net.change' property is a special property used track when any
304        * 'net.*' property name is updated. It is _ONLY_ updated here. Its value
305        * contains the last updated 'net.*' property.
306        */
307        property_set("net.change", name);
308    } else if (persistent_properties_loaded &&
309            strncmp("persist.", name, sizeof("persist.") - 1) == 0) {
310        /*
311         * Don't write properties to disk until after we have read all default properties
312         * to prevent them from being overwritten by default values.
313         */
314        write_peristent_property(name, value);
315    }
316    property_changed(name, value);
317    return 0;
318}
319
320static int property_list(void (*propfn)(const char *key, const char *value, void *cookie),
321                  void *cookie)
322{
323    char name[PROP_NAME_MAX];
324    char value[PROP_VALUE_MAX];
325    const prop_info *pi;
326    unsigned n;
327
328    for(n = 0; (pi = __system_property_find_nth(n)); n++) {
329        __system_property_read(pi, name, value);
330        propfn(name, value, cookie);
331    }
332    return 0;
333}
334
335void handle_property_set_fd(int fd)
336{
337    prop_msg msg;
338    int s;
339    int r;
340    int res;
341    struct ucred cr;
342    struct sockaddr_un addr;
343    socklen_t addr_size = sizeof(addr);
344    socklen_t cr_size = sizeof(cr);
345
346    if ((s = accept(fd, &addr, &addr_size)) < 0) {
347        return;
348    }
349
350    /* Check socket options here */
351    if (getsockopt(s, SOL_SOCKET, SO_PEERCRED, &cr, &cr_size) < 0) {
352        close(s);
353        ERROR("Unable to recieve socket options\n");
354        return;
355    }
356
357    r = recv(s, &msg, sizeof(msg), 0);
358    close(s);
359    if(r != sizeof(prop_msg)) {
360        ERROR("sys_prop: mis-match msg size recieved: %d expected: %d\n",
361              r, sizeof(prop_msg));
362        return;
363    }
364
365    switch(msg.cmd) {
366    case PROP_MSG_SETPROP:
367        msg.name[PROP_NAME_MAX-1] = 0;
368        msg.value[PROP_VALUE_MAX-1] = 0;
369
370        if(memcmp(msg.name,"ctl.",4) == 0) {
371            if (check_control_perms(msg.value, cr.uid)) {
372                handle_control_message((char*) msg.name + 4, (char*) msg.value);
373            } else {
374                ERROR("sys_prop: Unable to %s service ctl [%s] uid: %d pid:%d\n",
375                        msg.name + 4, msg.value, cr.uid, cr.pid);
376            }
377        } else {
378            if (check_perms(msg.name, cr.uid)) {
379                property_set((char*) msg.name, (char*) msg.value);
380            } else {
381                ERROR("sys_prop: permission denied uid:%d  name:%s\n",
382                      cr.uid, msg.name);
383            }
384        }
385        break;
386
387    default:
388        break;
389    }
390}
391
392void get_property_workspace(int *fd, int *sz)
393{
394    *fd = pa_workspace.fd;
395    *sz = pa_workspace.size;
396}
397
398static void load_properties(char *data)
399{
400    char *key, *value, *eol, *sol, *tmp;
401
402    sol = data;
403    while((eol = strchr(sol, '\n'))) {
404        key = sol;
405        *eol++ = 0;
406        sol = eol;
407
408        value = strchr(key, '=');
409        if(value == 0) continue;
410        *value++ = 0;
411
412        while(isspace(*key)) key++;
413        if(*key == '#') continue;
414        tmp = value - 2;
415        while((tmp > key) && isspace(*tmp)) *tmp-- = 0;
416
417        while(isspace(*value)) value++;
418        tmp = eol - 2;
419        while((tmp > value) && isspace(*tmp)) *tmp-- = 0;
420
421        property_set(key, value);
422    }
423}
424
425static void load_properties_from_file(const char *fn)
426{
427    char *data;
428    unsigned sz;
429
430    data = read_file(fn, &sz);
431
432    if(data != 0) {
433        load_properties(data);
434        free(data);
435    }
436}
437
438static void load_persistent_properties()
439{
440    DIR* dir = opendir(PERSISTENT_PROPERTY_DIR);
441    struct dirent*  entry;
442    char path[PATH_MAX];
443    char value[PROP_VALUE_MAX];
444    int fd, length;
445
446    if (dir) {
447        while ((entry = readdir(dir)) != NULL) {
448            if (!strcmp(entry->d_name, ".") || !strcmp(entry->d_name, "..") ||
449                    strncmp("persist.", entry->d_name, sizeof("persist.") - 1))
450                continue;
451#if HAVE_DIRENT_D_TYPE
452            if (entry->d_type != DT_REG)
453                continue;
454#endif
455            /* open the file and read the property value */
456            snprintf(path, sizeof(path), "%s/%s", PERSISTENT_PROPERTY_DIR, entry->d_name);
457            fd = open(path, O_RDONLY);
458            if (fd >= 0) {
459                length = read(fd, value, sizeof(value) - 1);
460                if (length >= 0) {
461                    value[length] = 0;
462                    property_set(entry->d_name, value);
463                } else {
464                    ERROR("Unable to read persistent property file %s errno: %d\n", path, errno);
465                }
466                close(fd);
467            } else {
468                ERROR("Unable to open persistent property file %s errno: %d\n", path, errno);
469            }
470        }
471        closedir(dir);
472    } else {
473        ERROR("Unable to open persistent property directory %s errno: %d\n", PERSISTENT_PROPERTY_DIR, errno);
474    }
475
476    persistent_properties_loaded = 1;
477}
478
479void property_init(void)
480{
481    init_property_area();
482    load_properties_from_file(PROP_PATH_RAMDISK_DEFAULT);
483}
484
485int start_property_service(void)
486{
487    int fd;
488
489    load_properties_from_file(PROP_PATH_SYSTEM_BUILD);
490    load_properties_from_file(PROP_PATH_SYSTEM_DEFAULT);
491    load_properties_from_file(PROP_PATH_LOCAL_OVERRIDE);
492    /* Read persistent properties after all default values have been loaded. */
493    load_persistent_properties();
494
495    fd = create_socket(PROP_SERVICE_NAME, SOCK_STREAM, 0666, 0, 0);
496    if(fd < 0) return -1;
497    fcntl(fd, F_SETFD, FD_CLOEXEC);
498    fcntl(fd, F_SETFL, O_NONBLOCK);
499
500    listen(fd, 8);
501    return fd;
502}
503