property_service.c revision b3779558dcfbe99f0b9c1ef796e3728edad25672 
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    { "service.adb.root",	AID_SHELL },
73    { "persist.sys.",	AID_SYSTEM },
74    { "persist.service.",   AID_SYSTEM },
75    { NULL, 0 }
76};
77
78/*
79 * White list of UID that are allowed to start/stop services.
80 * Currently there are no user apps that require.
81 */
82struct {
83    const char *service;
84    unsigned int uid;
85} control_perms[] = {
86     {NULL, 0 }
87};
88
89typedef struct {
90    void *data;
91    size_t size;
92    int fd;
93} workspace;
94
95static int init_workspace(workspace *w, size_t size)
96{
97    void *data;
98    int fd;
99
100    fd = ashmem_create_region("system_properties", size);
101    if(fd < 0)
102        return -1;
103
104    data = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
105    if(data == MAP_FAILED)
106        goto out;
107
108    /* allow the wolves we share with to do nothing but read */
109    ashmem_set_prot_region(fd, PROT_READ);
110
111    w->data = data;
112    w->size = size;
113    w->fd = fd;
114
115    return 0;
116
117out:
118    close(fd);
119    return -1;
120}
121
122/* (8 header words + 247 toc words) = 1020 bytes */
123/* 1024 bytes header and toc + 247 prop_infos @ 128 bytes = 32640 bytes */
124
125#define PA_COUNT_MAX  247
126#define PA_INFO_START 1024
127#define PA_SIZE       32768
128
129static workspace pa_workspace;
130static prop_info *pa_info_array;
131
132extern prop_area *__system_property_area__;
133
134static int init_property_area(void)
135{
136    prop_area *pa;
137
138    if(pa_info_array)
139        return -1;
140
141    if(init_workspace(&pa_workspace, PA_SIZE))
142        return -1;
143
144    fcntl(pa_workspace.fd, F_SETFD, FD_CLOEXEC);
145
146    pa_info_array = (void*) (((char*) pa_workspace.data) + PA_INFO_START);
147
148    pa = pa_workspace.data;
149    memset(pa, 0, PA_SIZE);
150    pa->magic = PROP_AREA_MAGIC;
151    pa->version = PROP_AREA_VERSION;
152
153        /* plug into the lib property services */
154    __system_property_area__ = pa;
155
156    return 0;
157}
158
159static void update_prop_info(prop_info *pi, const char *value, unsigned len)
160{
161    pi->serial = pi->serial | 1;
162    memcpy(pi->value, value, len + 1);
163    pi->serial = (len << 24) | ((pi->serial + 1) & 0xffffff);
164    __futex_wake(&pi->serial, INT32_MAX);
165}
166
167static int property_write(prop_info *pi, const char *value)
168{
169    int valuelen = strlen(value);
170    if(valuelen >= PROP_VALUE_MAX) return -1;
171    update_prop_info(pi, value, valuelen);
172    return 0;
173}
174
175
176/*
177 * Checks permissions for starting/stoping system services.
178 * AID_SYSTEM and AID_ROOT are always allowed.
179 *
180 * Returns 1 if uid allowed, 0 otherwise.
181 */
182static int check_control_perms(const char *name, int uid) {
183    int i;
184    if (uid == AID_SYSTEM || uid == AID_ROOT)
185        return 1;
186
187    /* Search the ACL */
188    for (i = 0; control_perms[i].service; i++) {
189        if (strcmp(control_perms[i].service, name) == 0) {
190            if (control_perms[i].uid == uid)
191                return 1;
192        }
193    }
194    return 0;
195}
196
197/*
198 * Checks permissions for setting system properties.
199 * Returns 1 if uid allowed, 0 otherwise.
200 */
201static int check_perms(const char *name, unsigned int uid)
202{
203    int i;
204    if (uid == 0)
205        return 1;
206
207    if(!strncmp(name, "ro.", 3))
208        name +=3;
209
210    for (i = 0; property_perms[i].prefix; i++) {
211        int tmp;
212        if (strncmp(property_perms[i].prefix, name,
213                    strlen(property_perms[i].prefix)) == 0) {
214            if (property_perms[i].uid == uid) {
215                return 1;
216            }
217        }
218    }
219
220    return 0;
221}
222
223const char* property_get(const char *name)
224{
225    prop_info *pi;
226
227    if(strlen(name) >= PROP_NAME_MAX) return 0;
228
229    pi = (prop_info*) __system_property_find(name);
230
231    if(pi != 0) {
232        return pi->value;
233    } else {
234        return 0;
235    }
236}
237
238static void write_peristent_property(const char *name, const char *value)
239{
240    const char *tempPath = PERSISTENT_PROPERTY_DIR "/.temp";
241    char path[PATH_MAX];
242    int fd, length;
243
244    snprintf(path, sizeof(path), "%s/%s", PERSISTENT_PROPERTY_DIR, name);
245
246    fd = open(tempPath, O_WRONLY|O_CREAT|O_TRUNC, 0600);
247    if (fd < 0) {
248        ERROR("Unable to write persistent property to temp file %s errno: %d\n", tempPath, errno);
249        return;
250    }
251    write(fd, value, strlen(value));
252    close(fd);
253
254    if (rename(tempPath, path)) {
255        unlink(tempPath);
256        ERROR("Unable to rename persistent property file %s to %s\n", tempPath, path);
257    }
258}
259
260int property_set(const char *name, const char *value)
261{
262    prop_area *pa;
263    prop_info *pi;
264
265    int namelen = strlen(name);
266    int valuelen = strlen(value);
267
268    if(namelen >= PROP_NAME_MAX) return -1;
269    if(valuelen >= PROP_VALUE_MAX) return -1;
270    if(namelen < 1) return -1;
271
272    pi = (prop_info*) __system_property_find(name);
273
274    if(pi != 0) {
275        /* ro.* properties may NEVER be modified once set */
276        if(!strncmp(name, "ro.", 3)) return -1;
277
278        pa = __system_property_area__;
279        update_prop_info(pi, value, valuelen);
280        pa->serial++;
281        __futex_wake(&pa->serial, INT32_MAX);
282    } else {
283        pa = __system_property_area__;
284        if(pa->count == PA_COUNT_MAX) return -1;
285
286        pi = pa_info_array + pa->count;
287        pi->serial = (valuelen << 24);
288        memcpy(pi->name, name, namelen + 1);
289        memcpy(pi->value, value, valuelen + 1);
290
291        pa->toc[pa->count] =
292            (namelen << 24) | (((unsigned) pi) - ((unsigned) pa));
293
294        pa->count++;
295        pa->serial++;
296        __futex_wake(&pa->serial, INT32_MAX);
297    }
298    /* If name starts with "net." treat as a DNS property. */
299    if (strncmp("net.", name, strlen("net.")) == 0)  {
300        if (strcmp("net.change", name) == 0) {
301            return 0;
302        }
303       /*
304        * The 'net.change' property is a special property used track when any
305        * 'net.*' property name is updated. It is _ONLY_ updated here. Its value
306        * contains the last updated 'net.*' property.
307        */
308        property_set("net.change", name);
309    } else if (persistent_properties_loaded &&
310            strncmp("persist.", name, strlen("persist.")) == 0) {
311        /*
312         * Don't write properties to disk until after we have read all default properties
313         * to prevent them from being overwritten by default values.
314         */
315        write_peristent_property(name, value);
316    }
317    property_changed(name, value);
318    return 0;
319}
320
321static int property_list(void (*propfn)(const char *key, const char *value, void *cookie),
322                  void *cookie)
323{
324    char name[PROP_NAME_MAX];
325    char value[PROP_VALUE_MAX];
326    const prop_info *pi;
327    unsigned n;
328
329    for(n = 0; (pi = __system_property_find_nth(n)); n++) {
330        __system_property_read(pi, name, value);
331        propfn(name, value, cookie);
332    }
333    return 0;
334}
335
336void handle_property_set_fd(int fd)
337{
338    prop_msg msg;
339    int s;
340    int r;
341    int res;
342    struct ucred cr;
343    struct sockaddr_un addr;
344    socklen_t addr_size = sizeof(addr);
345    socklen_t cr_size = sizeof(cr);
346
347    if ((s = accept(fd, (struct sockaddr *) &addr, &addr_size)) < 0) {
348        return;
349    }
350
351    /* Check socket options here */
352    if (getsockopt(s, SOL_SOCKET, SO_PEERCRED, &cr, &cr_size) < 0) {
353        close(s);
354        ERROR("Unable to recieve socket options\n");
355        return;
356    }
357
358    r = recv(s, &msg, sizeof(msg), 0);
359    close(s);
360    if(r != sizeof(prop_msg)) {
361        ERROR("sys_prop: mis-match msg size recieved: %d expected: %d\n",
362              r, sizeof(prop_msg));
363        return;
364    }
365
366    switch(msg.cmd) {
367    case PROP_MSG_SETPROP:
368        msg.name[PROP_NAME_MAX-1] = 0;
369        msg.value[PROP_VALUE_MAX-1] = 0;
370
371        if(memcmp(msg.name,"ctl.",4) == 0) {
372            if (check_control_perms(msg.value, cr.uid)) {
373                handle_control_message((char*) msg.name + 4, (char*) msg.value);
374            } else {
375                ERROR("sys_prop: Unable to %s service ctl [%s] uid: %d pid:%d\n",
376                        msg.name + 4, msg.value, cr.uid, cr.pid);
377            }
378        } else {
379            if (check_perms(msg.name, cr.uid)) {
380                property_set((char*) msg.name, (char*) msg.value);
381            } else {
382                ERROR("sys_prop: permission denied uid:%d  name:%s\n",
383                      cr.uid, msg.name);
384            }
385        }
386        break;
387
388    default:
389        break;
390    }
391}
392
393void get_property_workspace(int *fd, int *sz)
394{
395    *fd = pa_workspace.fd;
396    *sz = pa_workspace.size;
397}
398
399static void load_properties(char *data)
400{
401    char *key, *value, *eol, *sol, *tmp;
402
403    sol = data;
404    while((eol = strchr(sol, '\n'))) {
405        key = sol;
406        *eol++ = 0;
407        sol = eol;
408
409        value = strchr(key, '=');
410        if(value == 0) continue;
411        *value++ = 0;
412
413        while(isspace(*key)) key++;
414        if(*key == '#') continue;
415        tmp = value - 2;
416        while((tmp > key) && isspace(*tmp)) *tmp-- = 0;
417
418        while(isspace(*value)) value++;
419        tmp = eol - 2;
420        while((tmp > value) && isspace(*tmp)) *tmp-- = 0;
421
422        property_set(key, value);
423    }
424}
425
426static void load_properties_from_file(const char *fn)
427{
428    char *data;
429    unsigned sz;
430
431    data = read_file(fn, &sz);
432
433    if(data != 0) {
434        load_properties(data);
435        free(data);
436    }
437}
438
439static void load_persistent_properties()
440{
441    DIR* dir = opendir(PERSISTENT_PROPERTY_DIR);
442    struct dirent*  entry;
443    char path[PATH_MAX];
444    char value[PROP_VALUE_MAX];
445    int fd, length;
446
447    if (dir) {
448        while ((entry = readdir(dir)) != NULL) {
449            if (strncmp("persist.", entry->d_name, strlen("persist.")))
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