property_service.c revision c5e7ef24308f5a993ecfd5ac438d347e786f5e42 
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    unsigned int gid;
56} property_perms[] = {
57    { "net.rmnet0.",      AID_RADIO,    0 },
58    { "net.gprs.",        AID_RADIO,    0 },
59    { "net.ppp",          AID_RADIO,    0 },
60    { "ril.",             AID_RADIO,    0 },
61    { "gsm.",             AID_RADIO,    0 },
62    { "persist.radio",    AID_RADIO,    0 },
63    { "net.dns",          AID_RADIO,    0 },
64    { "net.",             AID_SYSTEM,   0 },
65    { "dev.",             AID_SYSTEM,   0 },
66    { "runtime.",         AID_SYSTEM,   0 },
67    { "hw.",              AID_SYSTEM,   0 },
68    { "sys.",             AID_SYSTEM,   0 },
69    { "service.",         AID_SYSTEM,   0 },
70    { "wlan.",            AID_SYSTEM,   0 },
71    { "dhcp.",            AID_SYSTEM,   0 },
72    { "dhcp.",            AID_DHCP,     0 },
73    { "vpn.",             AID_SYSTEM,   0 },
74    { "vpn.",             AID_VPN,      0 },
75    { "debug.",           AID_SHELL,    0 },
76    { "log.",             AID_SHELL,    0 },
77    { "service.adb.root", AID_SHELL,    0 },
78    { "persist.sys.",     AID_SYSTEM,   0 },
79    { "persist.service.", AID_SYSTEM,   0 },
80    { NULL, 0, 0 }
81};
82
83/*
84 * White list of UID that are allowed to start/stop services.
85 * Currently there are no user apps that require.
86 */
87struct {
88    const char *service;
89    unsigned int uid;
90    unsigned int gid;
91} control_perms[] = {
92    { "dumpstate",AID_SHELL, AID_LOG },
93     {NULL, 0, 0 }
94};
95
96typedef struct {
97    void *data;
98    size_t size;
99    int fd;
100} workspace;
101
102static int init_workspace(workspace *w, size_t size)
103{
104    void *data;
105    int fd;
106
107    fd = ashmem_create_region("system_properties", size);
108    if(fd < 0)
109        return -1;
110
111    data = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
112    if(data == MAP_FAILED)
113        goto out;
114
115    /* allow the wolves we share with to do nothing but read */
116    ashmem_set_prot_region(fd, PROT_READ);
117
118    w->data = data;
119    w->size = size;
120    w->fd = fd;
121
122    return 0;
123
124out:
125    close(fd);
126    return -1;
127}
128
129/* (8 header words + 247 toc words) = 1020 bytes */
130/* 1024 bytes header and toc + 247 prop_infos @ 128 bytes = 32640 bytes */
131
132#define PA_COUNT_MAX  247
133#define PA_INFO_START 1024
134#define PA_SIZE       32768
135
136static workspace pa_workspace;
137static prop_info *pa_info_array;
138
139extern prop_area *__system_property_area__;
140
141static int init_property_area(void)
142{
143    prop_area *pa;
144
145    if(pa_info_array)
146        return -1;
147
148    if(init_workspace(&pa_workspace, PA_SIZE))
149        return -1;
150
151    fcntl(pa_workspace.fd, F_SETFD, FD_CLOEXEC);
152
153    pa_info_array = (void*) (((char*) pa_workspace.data) + PA_INFO_START);
154
155    pa = pa_workspace.data;
156    memset(pa, 0, PA_SIZE);
157    pa->magic = PROP_AREA_MAGIC;
158    pa->version = PROP_AREA_VERSION;
159
160        /* plug into the lib property services */
161    __system_property_area__ = pa;
162
163    return 0;
164}
165
166static void update_prop_info(prop_info *pi, const char *value, unsigned len)
167{
168    pi->serial = pi->serial | 1;
169    memcpy(pi->value, value, len + 1);
170    pi->serial = (len << 24) | ((pi->serial + 1) & 0xffffff);
171    __futex_wake(&pi->serial, INT32_MAX);
172}
173
174static int property_write(prop_info *pi, const char *value)
175{
176    int valuelen = strlen(value);
177    if(valuelen >= PROP_VALUE_MAX) return -1;
178    update_prop_info(pi, value, valuelen);
179    return 0;
180}
181
182
183/*
184 * Checks permissions for starting/stoping system services.
185 * AID_SYSTEM and AID_ROOT are always allowed.
186 *
187 * Returns 1 if uid allowed, 0 otherwise.
188 */
189static int check_control_perms(const char *name, int uid, int gid) {
190    int i;
191    if (uid == AID_SYSTEM || uid == AID_ROOT)
192        return 1;
193
194    /* Search the ACL */
195    for (i = 0; control_perms[i].service; i++) {
196        if (strcmp(control_perms[i].service, name) == 0) {
197            if ((uid && control_perms[i].uid == uid) ||
198                (gid && control_perms[i].gid == gid)) {
199                return 1;
200            }
201        }
202    }
203    return 0;
204}
205
206/*
207 * Checks permissions for setting system properties.
208 * Returns 1 if uid allowed, 0 otherwise.
209 */
210static int check_perms(const char *name, unsigned int uid, int gid)
211{
212    int i;
213    if (uid == 0)
214        return 1;
215
216    if(!strncmp(name, "ro.", 3))
217        name +=3;
218
219    for (i = 0; property_perms[i].prefix; i++) {
220        int tmp;
221        if (strncmp(property_perms[i].prefix, name,
222                    strlen(property_perms[i].prefix)) == 0) {
223            if ((uid && property_perms[i].uid == uid) ||
224                (gid && property_perms[i].gid == gid)) {
225                return 1;
226            }
227        }
228    }
229
230    return 0;
231}
232
233const char* property_get(const char *name)
234{
235    prop_info *pi;
236
237    if(strlen(name) >= PROP_NAME_MAX) return 0;
238
239    pi = (prop_info*) __system_property_find(name);
240
241    if(pi != 0) {
242        return pi->value;
243    } else {
244        return 0;
245    }
246}
247
248static void write_persistent_property(const char *name, const char *value)
249{
250    const char *tempPath = PERSISTENT_PROPERTY_DIR "/.temp";
251    char path[PATH_MAX];
252    int fd, length;
253
254    snprintf(path, sizeof(path), "%s/%s", PERSISTENT_PROPERTY_DIR, name);
255
256    fd = open(tempPath, O_WRONLY|O_CREAT|O_TRUNC, 0600);
257    if (fd < 0) {
258        ERROR("Unable to write persistent property to temp file %s errno: %d\n", tempPath, errno);
259        return;
260    }
261    write(fd, value, strlen(value));
262    close(fd);
263
264    if (rename(tempPath, path)) {
265        unlink(tempPath);
266        ERROR("Unable to rename persistent property file %s to %s\n", tempPath, path);
267    }
268}
269
270int property_set(const char *name, const char *value)
271{
272    prop_area *pa;
273    prop_info *pi;
274
275    int namelen = strlen(name);
276    int valuelen = strlen(value);
277
278    if(namelen >= PROP_NAME_MAX) return -1;
279    if(valuelen >= PROP_VALUE_MAX) return -1;
280    if(namelen < 1) return -1;
281
282    pi = (prop_info*) __system_property_find(name);
283
284    if(pi != 0) {
285        /* ro.* properties may NEVER be modified once set */
286        if(!strncmp(name, "ro.", 3)) return -1;
287
288        pa = __system_property_area__;
289        update_prop_info(pi, value, valuelen);
290        pa->serial++;
291        __futex_wake(&pa->serial, INT32_MAX);
292    } else {
293        pa = __system_property_area__;
294        if(pa->count == PA_COUNT_MAX) return -1;
295
296        pi = pa_info_array + pa->count;
297        pi->serial = (valuelen << 24);
298        memcpy(pi->name, name, namelen + 1);
299        memcpy(pi->value, value, valuelen + 1);
300
301        pa->toc[pa->count] =
302            (namelen << 24) | (((unsigned) pi) - ((unsigned) pa));
303
304        pa->count++;
305        pa->serial++;
306        __futex_wake(&pa->serial, INT32_MAX);
307    }
308    /* If name starts with "net." treat as a DNS property. */
309    if (strncmp("net.", name, strlen("net.")) == 0)  {
310        if (strcmp("net.change", name) == 0) {
311            return 0;
312        }
313       /*
314        * The 'net.change' property is a special property used track when any
315        * 'net.*' property name is updated. It is _ONLY_ updated here. Its value
316        * contains the last updated 'net.*' property.
317        */
318        property_set("net.change", name);
319    } else if (persistent_properties_loaded &&
320            strncmp("persist.", name, strlen("persist.")) == 0) {
321        /*
322         * Don't write properties to disk until after we have read all default properties
323         * to prevent them from being overwritten by default values.
324         */
325        write_persistent_property(name, value);
326    }
327    property_changed(name, value);
328    return 0;
329}
330
331static int property_list(void (*propfn)(const char *key, const char *value, void *cookie),
332                  void *cookie)
333{
334    char name[PROP_NAME_MAX];
335    char value[PROP_VALUE_MAX];
336    const prop_info *pi;
337    unsigned n;
338
339    for(n = 0; (pi = __system_property_find_nth(n)); n++) {
340        __system_property_read(pi, name, value);
341        propfn(name, value, cookie);
342    }
343    return 0;
344}
345
346void handle_property_set_fd(int fd)
347{
348    prop_msg msg;
349    int s;
350    int r;
351    int res;
352    struct ucred cr;
353    struct sockaddr_un addr;
354    socklen_t addr_size = sizeof(addr);
355    socklen_t cr_size = sizeof(cr);
356
357    if ((s = accept(fd, (struct sockaddr *) &addr, &addr_size)) < 0) {
358        return;
359    }
360
361    /* Check socket options here */
362    if (getsockopt(s, SOL_SOCKET, SO_PEERCRED, &cr, &cr_size) < 0) {
363        close(s);
364        ERROR("Unable to recieve socket options\n");
365        return;
366    }
367
368    r = recv(s, &msg, sizeof(msg), 0);
369    close(s);
370    if(r != sizeof(prop_msg)) {
371        ERROR("sys_prop: mis-match msg size recieved: %d expected: %d\n",
372              r, sizeof(prop_msg));
373        return;
374    }
375
376    switch(msg.cmd) {
377    case PROP_MSG_SETPROP:
378        msg.name[PROP_NAME_MAX-1] = 0;
379        msg.value[PROP_VALUE_MAX-1] = 0;
380
381        if(memcmp(msg.name,"ctl.",4) == 0) {
382            if (check_control_perms(msg.value, cr.uid, cr.gid)) {
383                handle_control_message((char*) msg.name + 4, (char*) msg.value);
384            } else {
385                ERROR("sys_prop: Unable to %s service ctl [%s] uid: %d pid:%d\n",
386                        msg.name + 4, msg.value, cr.uid, cr.pid);
387            }
388        } else {
389            if (check_perms(msg.name, cr.uid, cr.gid)) {
390                property_set((char*) msg.name, (char*) msg.value);
391            } else {
392                ERROR("sys_prop: permission denied uid:%d  name:%s\n",
393                      cr.uid, msg.name);
394            }
395        }
396        break;
397
398    default:
399        break;
400    }
401}
402
403void get_property_workspace(int *fd, int *sz)
404{
405    *fd = pa_workspace.fd;
406    *sz = pa_workspace.size;
407}
408
409static void load_properties(char *data)
410{
411    char *key, *value, *eol, *sol, *tmp;
412
413    sol = data;
414    while((eol = strchr(sol, '\n'))) {
415        key = sol;
416        *eol++ = 0;
417        sol = eol;
418
419        value = strchr(key, '=');
420        if(value == 0) continue;
421        *value++ = 0;
422
423        while(isspace(*key)) key++;
424        if(*key == '#') continue;
425        tmp = value - 2;
426        while((tmp > key) && isspace(*tmp)) *tmp-- = 0;
427
428        while(isspace(*value)) value++;
429        tmp = eol - 2;
430        while((tmp > value) && isspace(*tmp)) *tmp-- = 0;
431
432        property_set(key, value);
433    }
434}
435
436static void load_properties_from_file(const char *fn)
437{
438    char *data;
439    unsigned sz;
440
441    data = read_file(fn, &sz);
442
443    if(data != 0) {
444        load_properties(data);
445        free(data);
446    }
447}
448
449static void load_persistent_properties()
450{
451    DIR* dir = opendir(PERSISTENT_PROPERTY_DIR);
452    struct dirent*  entry;
453    char path[PATH_MAX];
454    char value[PROP_VALUE_MAX];
455    int fd, length;
456
457    if (dir) {
458        while ((entry = readdir(dir)) != NULL) {
459            if (strncmp("persist.", entry->d_name, strlen("persist.")))
460                continue;
461#if HAVE_DIRENT_D_TYPE
462            if (entry->d_type != DT_REG)
463                continue;
464#endif
465            /* open the file and read the property value */
466            snprintf(path, sizeof(path), "%s/%s", PERSISTENT_PROPERTY_DIR, entry->d_name);
467            fd = open(path, O_RDONLY);
468            if (fd >= 0) {
469                length = read(fd, value, sizeof(value) - 1);
470                if (length >= 0) {
471                    value[length] = 0;
472                    property_set(entry->d_name, value);
473                } else {
474                    ERROR("Unable to read persistent property file %s errno: %d\n", path, errno);
475                }
476                close(fd);
477            } else {
478                ERROR("Unable to open persistent property file %s errno: %d\n", path, errno);
479            }
480        }
481        closedir(dir);
482    } else {
483        ERROR("Unable to open persistent property directory %s errno: %d\n", PERSISTENT_PROPERTY_DIR, errno);
484    }
485
486    persistent_properties_loaded = 1;
487}
488
489void property_init(void)
490{
491    init_property_area();
492    load_properties_from_file(PROP_PATH_RAMDISK_DEFAULT);
493}
494
495int start_property_service(void)
496{
497    int fd;
498
499    load_properties_from_file(PROP_PATH_SYSTEM_BUILD);
500    load_properties_from_file(PROP_PATH_SYSTEM_DEFAULT);
501    load_properties_from_file(PROP_PATH_LOCAL_OVERRIDE);
502    /* Read persistent properties after all default values have been loaded. */
503    load_persistent_properties();
504
505    fd = create_socket(PROP_SERVICE_NAME, SOCK_STREAM, 0666, 0, 0);
506    if(fd < 0) return -1;
507    fcntl(fd, F_SETFD, FD_CLOEXEC);
508    fcntl(fd, F_SETFL, O_NONBLOCK);
509
510    listen(fd, 8);
511    return fd;
512}
513