property_service.c revision 88dc657d50cb3289a9011828c497eee996ed958c 
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    { "vpn.",		AID_SYSTEM },
71    { "vpn.",		AID_VPN },
72    { "debug.",		AID_SHELL },
73    { "log.",		AID_SHELL },
74    { "service.adb.root",	AID_SHELL },
75    { "persist.sys.",	AID_SYSTEM },
76    { "persist.service.",   AID_SYSTEM },
77    { NULL, 0 }
78};
79
80/*
81 * White list of UID that are allowed to start/stop services.
82 * Currently there are no user apps that require.
83 */
84struct {
85    const char *service;
86    unsigned int uid;
87} control_perms[] = {
88     {NULL, 0 }
89};
90
91typedef struct {
92    void *data;
93    size_t size;
94    int fd;
95} workspace;
96
97static int init_workspace(workspace *w, size_t size)
98{
99    void *data;
100    int fd;
101
102    fd = ashmem_create_region("system_properties", size);
103    if(fd < 0)
104        return -1;
105
106    data = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
107    if(data == MAP_FAILED)
108        goto out;
109
110    /* allow the wolves we share with to do nothing but read */
111    ashmem_set_prot_region(fd, PROT_READ);
112
113    w->data = data;
114    w->size = size;
115    w->fd = fd;
116
117    return 0;
118
119out:
120    close(fd);
121    return -1;
122}
123
124/* (8 header words + 247 toc words) = 1020 bytes */
125/* 1024 bytes header and toc + 247 prop_infos @ 128 bytes = 32640 bytes */
126
127#define PA_COUNT_MAX  247
128#define PA_INFO_START 1024
129#define PA_SIZE       32768
130
131static workspace pa_workspace;
132static prop_info *pa_info_array;
133
134extern prop_area *__system_property_area__;
135
136static int init_property_area(void)
137{
138    prop_area *pa;
139
140    if(pa_info_array)
141        return -1;
142
143    if(init_workspace(&pa_workspace, PA_SIZE))
144        return -1;
145
146    fcntl(pa_workspace.fd, F_SETFD, FD_CLOEXEC);
147
148    pa_info_array = (void*) (((char*) pa_workspace.data) + PA_INFO_START);
149
150    pa = pa_workspace.data;
151    memset(pa, 0, PA_SIZE);
152    pa->magic = PROP_AREA_MAGIC;
153    pa->version = PROP_AREA_VERSION;
154
155        /* plug into the lib property services */
156    __system_property_area__ = pa;
157
158    return 0;
159}
160
161static void update_prop_info(prop_info *pi, const char *value, unsigned len)
162{
163    pi->serial = pi->serial | 1;
164    memcpy(pi->value, value, len + 1);
165    pi->serial = (len << 24) | ((pi->serial + 1) & 0xffffff);
166    __futex_wake(&pi->serial, INT32_MAX);
167}
168
169static int property_write(prop_info *pi, const char *value)
170{
171    int valuelen = strlen(value);
172    if(valuelen >= PROP_VALUE_MAX) return -1;
173    update_prop_info(pi, value, valuelen);
174    return 0;
175}
176
177
178/*
179 * Checks permissions for starting/stoping system services.
180 * AID_SYSTEM and AID_ROOT are always allowed.
181 *
182 * Returns 1 if uid allowed, 0 otherwise.
183 */
184static int check_control_perms(const char *name, int uid) {
185    int i;
186    if (uid == AID_SYSTEM || uid == AID_ROOT)
187        return 1;
188
189    /* Search the ACL */
190    for (i = 0; control_perms[i].service; i++) {
191        if (strcmp(control_perms[i].service, name) == 0) {
192            if (control_perms[i].uid == uid)
193                return 1;
194        }
195    }
196    return 0;
197}
198
199/*
200 * Checks permissions for setting system properties.
201 * Returns 1 if uid allowed, 0 otherwise.
202 */
203static int check_perms(const char *name, unsigned int uid)
204{
205    int i;
206    if (uid == 0)
207        return 1;
208
209    if(!strncmp(name, "ro.", 3))
210        name +=3;
211
212    for (i = 0; property_perms[i].prefix; i++) {
213        int tmp;
214        if (strncmp(property_perms[i].prefix, name,
215                    strlen(property_perms[i].prefix)) == 0) {
216            if (property_perms[i].uid == uid) {
217                return 1;
218            }
219        }
220    }
221
222    return 0;
223}
224
225const char* property_get(const char *name)
226{
227    prop_info *pi;
228
229    if(strlen(name) >= PROP_NAME_MAX) return 0;
230
231    pi = (prop_info*) __system_property_find(name);
232
233    if(pi != 0) {
234        return pi->value;
235    } else {
236        return 0;
237    }
238}
239
240static void write_peristent_property(const char *name, const char *value)
241{
242    const char *tempPath = PERSISTENT_PROPERTY_DIR "/.temp";
243    char path[PATH_MAX];
244    int fd, length;
245
246    snprintf(path, sizeof(path), "%s/%s", PERSISTENT_PROPERTY_DIR, name);
247
248    fd = open(tempPath, O_WRONLY|O_CREAT|O_TRUNC, 0600);
249    if (fd < 0) {
250        ERROR("Unable to write persistent property to temp file %s errno: %d\n", tempPath, errno);
251        return;
252    }
253    write(fd, value, strlen(value));
254    close(fd);
255
256    if (rename(tempPath, path)) {
257        unlink(tempPath);
258        ERROR("Unable to rename persistent property file %s to %s\n", tempPath, path);
259    }
260}
261
262int property_set(const char *name, const char *value)
263{
264    prop_area *pa;
265    prop_info *pi;
266
267    int namelen = strlen(name);
268    int valuelen = strlen(value);
269
270    if(namelen >= PROP_NAME_MAX) return -1;
271    if(valuelen >= PROP_VALUE_MAX) return -1;
272    if(namelen < 1) return -1;
273
274    pi = (prop_info*) __system_property_find(name);
275
276    if(pi != 0) {
277        /* ro.* properties may NEVER be modified once set */
278        if(!strncmp(name, "ro.", 3)) return -1;
279
280        pa = __system_property_area__;
281        update_prop_info(pi, value, valuelen);
282        pa->serial++;
283        __futex_wake(&pa->serial, INT32_MAX);
284    } else {
285        pa = __system_property_area__;
286        if(pa->count == PA_COUNT_MAX) return -1;
287
288        pi = pa_info_array + pa->count;
289        pi->serial = (valuelen << 24);
290        memcpy(pi->name, name, namelen + 1);
291        memcpy(pi->value, value, valuelen + 1);
292
293        pa->toc[pa->count] =
294            (namelen << 24) | (((unsigned) pi) - ((unsigned) pa));
295
296        pa->count++;
297        pa->serial++;
298        __futex_wake(&pa->serial, INT32_MAX);
299    }
300    /* If name starts with "net." treat as a DNS property. */
301    if (strncmp("net.", name, strlen("net.")) == 0)  {
302        if (strcmp("net.change", name) == 0) {
303            return 0;
304        }
305       /*
306        * The 'net.change' property is a special property used track when any
307        * 'net.*' property name is updated. It is _ONLY_ updated here. Its value
308        * contains the last updated 'net.*' property.
309        */
310        property_set("net.change", name);
311    } else if (persistent_properties_loaded &&
312            strncmp("persist.", name, strlen("persist.")) == 0) {
313        /*
314         * Don't write properties to disk until after we have read all default properties
315         * to prevent them from being overwritten by default values.
316         */
317        write_peristent_property(name, value);
318    }
319    property_changed(name, value);
320    return 0;
321}
322
323static int property_list(void (*propfn)(const char *key, const char *value, void *cookie),
324                  void *cookie)
325{
326    char name[PROP_NAME_MAX];
327    char value[PROP_VALUE_MAX];
328    const prop_info *pi;
329    unsigned n;
330
331    for(n = 0; (pi = __system_property_find_nth(n)); n++) {
332        __system_property_read(pi, name, value);
333        propfn(name, value, cookie);
334    }
335    return 0;
336}
337
338void handle_property_set_fd(int fd)
339{
340    prop_msg msg;
341    int s;
342    int r;
343    int res;
344    struct ucred cr;
345    struct sockaddr_un addr;
346    socklen_t addr_size = sizeof(addr);
347    socklen_t cr_size = sizeof(cr);
348
349    if ((s = accept(fd, (struct sockaddr *) &addr, &addr_size)) < 0) {
350        return;
351    }
352
353    /* Check socket options here */
354    if (getsockopt(s, SOL_SOCKET, SO_PEERCRED, &cr, &cr_size) < 0) {
355        close(s);
356        ERROR("Unable to recieve socket options\n");
357        return;
358    }
359
360    r = recv(s, &msg, sizeof(msg), 0);
361    close(s);
362    if(r != sizeof(prop_msg)) {
363        ERROR("sys_prop: mis-match msg size recieved: %d expected: %d\n",
364              r, sizeof(prop_msg));
365        return;
366    }
367
368    switch(msg.cmd) {
369    case PROP_MSG_SETPROP:
370        msg.name[PROP_NAME_MAX-1] = 0;
371        msg.value[PROP_VALUE_MAX-1] = 0;
372
373        if(memcmp(msg.name,"ctl.",4) == 0) {
374            if (check_control_perms(msg.value, cr.uid)) {
375                handle_control_message((char*) msg.name + 4, (char*) msg.value);
376            } else {
377                ERROR("sys_prop: Unable to %s service ctl [%s] uid: %d pid:%d\n",
378                        msg.name + 4, msg.value, cr.uid, cr.pid);
379            }
380        } else {
381            if (check_perms(msg.name, cr.uid)) {
382                property_set((char*) msg.name, (char*) msg.value);
383            } else {
384                ERROR("sys_prop: permission denied uid:%d  name:%s\n",
385                      cr.uid, msg.name);
386            }
387        }
388        break;
389
390    default:
391        break;
392    }
393}
394
395void get_property_workspace(int *fd, int *sz)
396{
397    *fd = pa_workspace.fd;
398    *sz = pa_workspace.size;
399}
400
401static void load_properties(char *data)
402{
403    char *key, *value, *eol, *sol, *tmp;
404
405    sol = data;
406    while((eol = strchr(sol, '\n'))) {
407        key = sol;
408        *eol++ = 0;
409        sol = eol;
410
411        value = strchr(key, '=');
412        if(value == 0) continue;
413        *value++ = 0;
414
415        while(isspace(*key)) key++;
416        if(*key == '#') continue;
417        tmp = value - 2;
418        while((tmp > key) && isspace(*tmp)) *tmp-- = 0;
419
420        while(isspace(*value)) value++;
421        tmp = eol - 2;
422        while((tmp > value) && isspace(*tmp)) *tmp-- = 0;
423
424        property_set(key, value);
425    }
426}
427
428static void load_properties_from_file(const char *fn)
429{
430    char *data;
431    unsigned sz;
432
433    data = read_file(fn, &sz);
434
435    if(data != 0) {
436        load_properties(data);
437        free(data);
438    }
439}
440
441static void load_persistent_properties()
442{
443    DIR* dir = opendir(PERSISTENT_PROPERTY_DIR);
444    struct dirent*  entry;
445    char path[PATH_MAX];
446    char value[PROP_VALUE_MAX];
447    int fd, length;
448
449    if (dir) {
450        while ((entry = readdir(dir)) != NULL) {
451            if (strncmp("persist.", entry->d_name, strlen("persist.")))
452                continue;
453#if HAVE_DIRENT_D_TYPE
454            if (entry->d_type != DT_REG)
455                continue;
456#endif
457            /* open the file and read the property value */
458            snprintf(path, sizeof(path), "%s/%s", PERSISTENT_PROPERTY_DIR, entry->d_name);
459            fd = open(path, O_RDONLY);
460            if (fd >= 0) {
461                length = read(fd, value, sizeof(value) - 1);
462                if (length >= 0) {
463                    value[length] = 0;
464                    property_set(entry->d_name, value);
465                } else {
466                    ERROR("Unable to read persistent property file %s errno: %d\n", path, errno);
467                }
468                close(fd);
469            } else {
470                ERROR("Unable to open persistent property file %s errno: %d\n", path, errno);
471            }
472        }
473        closedir(dir);
474    } else {
475        ERROR("Unable to open persistent property directory %s errno: %d\n", PERSISTENT_PROPERTY_DIR, errno);
476    }
477
478    persistent_properties_loaded = 1;
479}
480
481void property_init(void)
482{
483    init_property_area();
484    load_properties_from_file(PROP_PATH_RAMDISK_DEFAULT);
485}
486
487int start_property_service(void)
488{
489    int fd;
490
491    load_properties_from_file(PROP_PATH_SYSTEM_BUILD);
492    load_properties_from_file(PROP_PATH_SYSTEM_DEFAULT);
493    load_properties_from_file(PROP_PATH_LOCAL_OVERRIDE);
494    /* Read persistent properties after all default values have been loaded. */
495    load_persistent_properties();
496
497    fd = create_socket(PROP_SERVICE_NAME, SOCK_STREAM, 0666, 0, 0);
498    if(fd < 0) return -1;
499    fcntl(fd, F_SETFD, FD_CLOEXEC);
500    fcntl(fd, F_SETFL, O_NONBLOCK);
501
502    listen(fd, 8);
503    return fd;
504}
505