property_service.cpp revision 98ff77204cef9bb8f0f27420833233622060a09e 
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#include <sys/poll.h>
28
29#include <cutils/misc.h>
30#include <cutils/sockets.h>
31#include <cutils/multiuser.h>
32
33#define _REALLY_INCLUDE_SYS__SYSTEM_PROPERTIES_H_
34#include <sys/_system_properties.h>
35
36#include <sys/socket.h>
37#include <sys/un.h>
38#include <sys/select.h>
39#include <sys/types.h>
40#include <netinet/in.h>
41#include <sys/mman.h>
42#include <private/android_filesystem_config.h>
43
44#include <selinux/selinux.h>
45#include <selinux/label.h>
46
47#include "property_service.h"
48#include "init.h"
49#include "util.h"
50#include "log.h"
51
52#define PERSISTENT_PROPERTY_DIR  "/data/property"
53
54static int persistent_properties_loaded = 0;
55static int property_area_inited = 0;
56
57static int property_set_fd = -1;
58
59struct workspace {
60    size_t size;
61    int fd;
62};
63
64static int init_workspace(workspace *w, size_t size)
65{
66    int fd = open(PROP_FILENAME, O_RDONLY | O_NOFOLLOW);
67    if (fd < 0)
68        return -1;
69
70    w->size = size;
71    w->fd = fd;
72    return 0;
73}
74
75static workspace pa_workspace;
76
77static int init_property_area(void)
78{
79    if (property_area_inited)
80        return -1;
81
82    if(__system_property_area_init())
83        return -1;
84
85    if(init_workspace(&pa_workspace, 0))
86        return -1;
87
88    fcntl(pa_workspace.fd, F_SETFD, FD_CLOEXEC);
89
90    property_area_inited = 1;
91    return 0;
92}
93
94static int check_mac_perms(const char *name, char *sctx)
95{
96    if (is_selinux_enabled() <= 0)
97        return 1;
98
99    char *tctx = NULL;
100    int result = 0;
101
102    if (!sctx)
103        goto err;
104
105    if (!sehandle_prop)
106        goto err;
107
108    if (selabel_lookup(sehandle_prop, &tctx, name, 1) != 0)
109        goto err;
110
111    if (selinux_check_access(sctx, tctx, "property_service", "set", (void*) name) == 0)
112        result = 1;
113
114    freecon(tctx);
115 err:
116    return result;
117}
118
119static int check_control_mac_perms(const char *name, char *sctx)
120{
121    /*
122     *  Create a name prefix out of ctl.<service name>
123     *  The new prefix allows the use of the existing
124     *  property service backend labeling while avoiding
125     *  mislabels based on true property prefixes.
126     */
127    char ctl_name[PROP_VALUE_MAX+4];
128    int ret = snprintf(ctl_name, sizeof(ctl_name), "ctl.%s", name);
129
130    if (ret < 0 || (size_t) ret >= sizeof(ctl_name))
131        return 0;
132
133    return check_mac_perms(ctl_name, sctx);
134}
135
136/*
137 * Checks permissions for setting system properties.
138 * Returns 1 if uid allowed, 0 otherwise.
139 */
140static int check_perms(const char *name, char *sctx)
141{
142    if(!strncmp(name, "ro.", 3))
143        name +=3;
144
145    return check_mac_perms(name, sctx);
146}
147
148int __property_get(const char *name, char *value)
149{
150    return __system_property_get(name, value);
151}
152
153static void write_persistent_property(const char *name, const char *value)
154{
155    char tempPath[PATH_MAX];
156    char path[PATH_MAX];
157    int fd;
158
159    snprintf(tempPath, sizeof(tempPath), "%s/.temp.XXXXXX", PERSISTENT_PROPERTY_DIR);
160    fd = mkstemp(tempPath);
161    if (fd < 0) {
162        ERROR("Unable to write persistent property to temp file %s errno: %d\n", tempPath, errno);
163        return;
164    }
165    write(fd, value, strlen(value));
166    fsync(fd);
167    close(fd);
168
169    snprintf(path, sizeof(path), "%s/%s", PERSISTENT_PROPERTY_DIR, name);
170    if (rename(tempPath, path)) {
171        unlink(tempPath);
172        ERROR("Unable to rename persistent property file %s to %s\n", tempPath, path);
173    }
174}
175
176static bool is_legal_property_name(const char* name, size_t namelen)
177{
178    size_t i;
179    if (namelen >= PROP_NAME_MAX) return false;
180    if (namelen < 1) return false;
181    if (name[0] == '.') return false;
182    if (name[namelen - 1] == '.') return false;
183
184    /* Only allow alphanumeric, plus '.', '-', or '_' */
185    /* Don't allow ".." to appear in a property name */
186    for (i = 0; i < namelen; i++) {
187        if (name[i] == '.') {
188            // i=0 is guaranteed to never have a dot. See above.
189            if (name[i-1] == '.') return false;
190            continue;
191        }
192        if (name[i] == '_' || name[i] == '-') continue;
193        if (name[i] >= 'a' && name[i] <= 'z') continue;
194        if (name[i] >= 'A' && name[i] <= 'Z') continue;
195        if (name[i] >= '0' && name[i] <= '9') continue;
196        return false;
197    }
198
199    return true;
200}
201
202int property_set(const char *name, const char *value)
203{
204    prop_info *pi;
205    int ret;
206
207    size_t namelen = strlen(name);
208    size_t valuelen = strlen(value);
209
210    if (!is_legal_property_name(name, namelen)) return -1;
211    if (valuelen >= PROP_VALUE_MAX) return -1;
212
213    pi = (prop_info*) __system_property_find(name);
214
215    if(pi != 0) {
216        /* ro.* properties may NEVER be modified once set */
217        if(!strncmp(name, "ro.", 3)) return -1;
218
219        __system_property_update(pi, value, valuelen);
220    } else {
221        ret = __system_property_add(name, namelen, value, valuelen);
222        if (ret < 0) {
223            ERROR("Failed to set '%s'='%s'\n", name, value);
224            return ret;
225        }
226    }
227    /* If name starts with "net." treat as a DNS property. */
228    if (strncmp("net.", name, strlen("net.")) == 0)  {
229        if (strcmp("net.change", name) == 0) {
230            return 0;
231        }
232       /*
233        * The 'net.change' property is a special property used track when any
234        * 'net.*' property name is updated. It is _ONLY_ updated here. Its value
235        * contains the last updated 'net.*' property.
236        */
237        property_set("net.change", name);
238    } else if (persistent_properties_loaded &&
239            strncmp("persist.", name, strlen("persist.")) == 0) {
240        /*
241         * Don't write properties to disk until after we have read all default properties
242         * to prevent them from being overwritten by default values.
243         */
244        write_persistent_property(name, value);
245    } else if (strcmp("selinux.reload_policy", name) == 0 &&
246               strcmp("1", value) == 0) {
247        selinux_reload_policy();
248    }
249    property_changed(name, value);
250    return 0;
251}
252
253void handle_property_set_fd()
254{
255    prop_msg msg;
256    int s;
257    int r;
258    struct ucred cr;
259    struct sockaddr_un addr;
260    socklen_t addr_size = sizeof(addr);
261    socklen_t cr_size = sizeof(cr);
262    char * source_ctx = NULL;
263    struct pollfd ufds[1];
264    const int timeout_ms = 2 * 1000;  /* Default 2 sec timeout for caller to send property. */
265    int nr;
266
267    if ((s = accept(property_set_fd, (struct sockaddr *) &addr, &addr_size)) < 0) {
268        return;
269    }
270
271    /* Check socket options here */
272    if (getsockopt(s, SOL_SOCKET, SO_PEERCRED, &cr, &cr_size) < 0) {
273        close(s);
274        ERROR("Unable to receive socket options\n");
275        return;
276    }
277
278    ufds[0].fd = s;
279    ufds[0].events = POLLIN;
280    ufds[0].revents = 0;
281    nr = TEMP_FAILURE_RETRY(poll(ufds, 1, timeout_ms));
282    if (nr == 0) {
283        ERROR("sys_prop: timeout waiting for uid=%d to send property message.\n", cr.uid);
284        close(s);
285        return;
286    } else if (nr < 0) {
287        ERROR("sys_prop: error waiting for uid=%d to send property message. err=%d %s\n", cr.uid, errno, strerror(errno));
288        close(s);
289        return;
290    }
291
292    r = TEMP_FAILURE_RETRY(recv(s, &msg, sizeof(msg), MSG_DONTWAIT));
293    if(r != sizeof(prop_msg)) {
294        ERROR("sys_prop: mis-match msg size received: %d expected: %zu errno: %d\n",
295              r, sizeof(prop_msg), errno);
296        close(s);
297        return;
298    }
299
300    switch(msg.cmd) {
301    case PROP_MSG_SETPROP:
302        msg.name[PROP_NAME_MAX-1] = 0;
303        msg.value[PROP_VALUE_MAX-1] = 0;
304
305        if (!is_legal_property_name(msg.name, strlen(msg.name))) {
306            ERROR("sys_prop: illegal property name. Got: \"%s\"\n", msg.name);
307            close(s);
308            return;
309        }
310
311        getpeercon(s, &source_ctx);
312
313        if(memcmp(msg.name,"ctl.",4) == 0) {
314            // Keep the old close-socket-early behavior when handling
315            // ctl.* properties.
316            close(s);
317            if (check_control_mac_perms(msg.value, source_ctx)) {
318                handle_control_message((char*) msg.name + 4, (char*) msg.value);
319            } else {
320                ERROR("sys_prop: Unable to %s service ctl [%s] uid:%d gid:%d pid:%d\n",
321                        msg.name + 4, msg.value, cr.uid, cr.gid, cr.pid);
322            }
323        } else {
324            if (check_perms(msg.name, source_ctx)) {
325                property_set((char*) msg.name, (char*) msg.value);
326            } else {
327                ERROR("sys_prop: permission denied uid:%d  name:%s\n",
328                      cr.uid, msg.name);
329            }
330
331            // Note: bionic's property client code assumes that the
332            // property server will not close the socket until *AFTER*
333            // the property is written to memory.
334            close(s);
335        }
336        freecon(source_ctx);
337        break;
338
339    default:
340        close(s);
341        break;
342    }
343}
344
345void get_property_workspace(int *fd, int *sz)
346{
347    *fd = pa_workspace.fd;
348    *sz = pa_workspace.size;
349}
350
351static void load_properties_from_file(const char *, const char *);
352
353/*
354 * Filter is used to decide which properties to load: NULL loads all keys,
355 * "ro.foo.*" is a prefix match, and "ro.foo.bar" is an exact match.
356 */
357static void load_properties(char *data, const char *filter)
358{
359    char *key, *value, *eol, *sol, *tmp, *fn;
360    size_t flen = 0;
361
362    if (filter) {
363        flen = strlen(filter);
364    }
365
366    sol = data;
367    while ((eol = strchr(sol, '\n'))) {
368        key = sol;
369        *eol++ = 0;
370        sol = eol;
371
372        while (isspace(*key)) key++;
373        if (*key == '#') continue;
374
375        tmp = eol - 2;
376        while ((tmp > key) && isspace(*tmp)) *tmp-- = 0;
377
378        if (!strncmp(key, "import ", 7) && flen == 0) {
379            fn = key + 7;
380            while (isspace(*fn)) fn++;
381
382            key = strchr(fn, ' ');
383            if (key) {
384                *key++ = 0;
385                while (isspace(*key)) key++;
386            }
387
388            load_properties_from_file(fn, key);
389
390        } else {
391            value = strchr(key, '=');
392            if (!value) continue;
393            *value++ = 0;
394
395            tmp = value - 2;
396            while ((tmp > key) && isspace(*tmp)) *tmp-- = 0;
397
398            while (isspace(*value)) value++;
399
400            if (flen > 0) {
401                if (filter[flen - 1] == '*') {
402                    if (strncmp(key, filter, flen - 1)) continue;
403                } else {
404                    if (strcmp(key, filter)) continue;
405                }
406            }
407
408            property_set(key, value);
409        }
410    }
411}
412
413/*
414 * Filter is used to decide which properties to load: NULL loads all keys,
415 * "ro.foo.*" is a prefix match, and "ro.foo.bar" is an exact match.
416 */
417static void load_properties_from_file(const char *fn, const char *filter)
418{
419    std::string data;
420    if (read_file(fn, &data)) {
421        load_properties(&data[0], filter);
422    }
423}
424
425static void load_persistent_properties()
426{
427    DIR* dir = opendir(PERSISTENT_PROPERTY_DIR);
428    int dir_fd;
429    struct dirent*  entry;
430    char value[PROP_VALUE_MAX];
431    int fd, length;
432    struct stat sb;
433
434    if (dir) {
435        dir_fd = dirfd(dir);
436        while ((entry = readdir(dir)) != NULL) {
437            if (strncmp("persist.", entry->d_name, strlen("persist.")))
438                continue;
439            if (entry->d_type != DT_REG)
440                continue;
441            /* open the file and read the property value */
442            fd = openat(dir_fd, entry->d_name, O_RDONLY | O_NOFOLLOW);
443            if (fd < 0) {
444                ERROR("Unable to open persistent property file \"%s\" errno: %d\n",
445                      entry->d_name, errno);
446                continue;
447            }
448            if (fstat(fd, &sb) < 0) {
449                ERROR("fstat on property file \"%s\" failed errno: %d\n", entry->d_name, errno);
450                close(fd);
451                continue;
452            }
453
454            // File must not be accessible to others, be owned by root/root, and
455            // not be a hard link to any other file.
456            if (((sb.st_mode & (S_IRWXG | S_IRWXO)) != 0)
457                    || (sb.st_uid != 0)
458                    || (sb.st_gid != 0)
459                    || (sb.st_nlink != 1)) {
460                ERROR("skipping insecure property file %s (uid=%u gid=%u nlink=%u mode=%o)\n",
461                      entry->d_name, (unsigned int)sb.st_uid, (unsigned int)sb.st_gid,
462                      (unsigned int)sb.st_nlink, sb.st_mode);
463                close(fd);
464                continue;
465            }
466
467            length = read(fd, value, sizeof(value) - 1);
468            if (length >= 0) {
469                value[length] = 0;
470                property_set(entry->d_name, value);
471            } else {
472                ERROR("Unable to read persistent property file %s errno: %d\n",
473                      entry->d_name, errno);
474            }
475            close(fd);
476        }
477        closedir(dir);
478    } else {
479        ERROR("Unable to open persistent property directory %s errno: %d\n", PERSISTENT_PROPERTY_DIR, errno);
480    }
481
482    persistent_properties_loaded = 1;
483}
484
485void property_init(void)
486{
487    init_property_area();
488}
489
490void property_load_boot_defaults(void)
491{
492    load_properties_from_file(PROP_PATH_RAMDISK_DEFAULT, NULL);
493}
494
495int properties_inited(void)
496{
497    return property_area_inited;
498}
499
500static void load_override_properties() {
501    if (ALLOW_LOCAL_PROP_OVERRIDE) {
502        char debuggable[PROP_VALUE_MAX];
503        int ret = property_get("ro.debuggable", debuggable);
504        if (ret && (strcmp(debuggable, "1") == 0)) {
505            load_properties_from_file(PROP_PATH_LOCAL_OVERRIDE, NULL);
506        }
507    }
508}
509
510
511/* When booting an encrypted system, /data is not mounted when the
512 * property service is started, so any properties stored there are
513 * not loaded.  Vold triggers init to load these properties once it
514 * has mounted /data.
515 */
516void load_persist_props(void)
517{
518    load_override_properties();
519    /* Read persistent properties after all default values have been loaded. */
520    load_persistent_properties();
521}
522
523void load_all_props(void)
524{
525    load_properties_from_file(PROP_PATH_SYSTEM_BUILD, NULL);
526    load_properties_from_file(PROP_PATH_SYSTEM_DEFAULT, NULL);
527    load_properties_from_file(PROP_PATH_VENDOR_BUILD, NULL);
528    load_properties_from_file(PROP_PATH_BOOTIMAGE_BUILD, NULL);
529    load_properties_from_file(PROP_PATH_FACTORY, "ro.*");
530
531    load_override_properties();
532
533    /* Read persistent properties after all default values have been loaded. */
534    load_persistent_properties();
535}
536
537void start_property_service(void)
538{
539    int fd;
540
541    fd = create_socket(PROP_SERVICE_NAME, SOCK_STREAM, 0666, 0, 0, NULL);
542    if(fd < 0) return;
543    fcntl(fd, F_SETFD, FD_CLOEXEC);
544    fcntl(fd, F_SETFL, O_NONBLOCK);
545
546    listen(fd, 8);
547    property_set_fd = fd;
548}
549
550int get_property_set_fd()
551{
552    return property_set_fd;
553}
554