property_service.cpp revision 62b3f91d142e8c0b698729d3d7f3f4a9b8924c2f 
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 <memory>
30
31#include <cutils/misc.h>
32#include <cutils/sockets.h>
33#include <cutils/multiuser.h>
34
35#define _REALLY_INCLUDE_SYS__SYSTEM_PROPERTIES_H_
36#include <sys/_system_properties.h>
37
38#include <sys/socket.h>
39#include <sys/un.h>
40#include <sys/select.h>
41#include <sys/types.h>
42#include <netinet/in.h>
43#include <sys/mman.h>
44#include <private/android_filesystem_config.h>
45
46#include <selinux/selinux.h>
47#include <selinux/label.h>
48
49#include <fs_mgr.h>
50#include <base/file.h>
51#include "bootimg.h"
52
53#include "property_service.h"
54#include "init.h"
55#include "util.h"
56#include "log.h"
57
58#define PERSISTENT_PROPERTY_DIR  "/data/property"
59#define FSTAB_PREFIX "/fstab."
60#define RECOVERY_MOUNT_POINT "/recovery"
61
62static int persistent_properties_loaded = 0;
63static bool property_area_initialized = false;
64
65static int property_set_fd = -1;
66
67struct workspace {
68    size_t size;
69    int fd;
70};
71
72static workspace pa_workspace;
73
74void property_init() {
75    if (property_area_initialized) {
76        return;
77    }
78
79    property_area_initialized = true;
80
81    if (__system_property_area_init()) {
82        return;
83    }
84
85    pa_workspace.size = 0;
86    pa_workspace.fd = open(PROP_FILENAME, O_RDONLY | O_NOFOLLOW | O_CLOEXEC);
87    if (pa_workspace.fd == -1) {
88        ERROR("Failed to open %s: %s\n", PROP_FILENAME, strerror(errno));
89        return;
90    }
91}
92
93static int check_mac_perms(const char *name, char *sctx)
94{
95    char *tctx = NULL;
96    int result = 0;
97
98    if (!sctx)
99        goto err;
100
101    if (!sehandle_prop)
102        goto err;
103
104    if (selabel_lookup(sehandle_prop, &tctx, name, 1) != 0)
105        goto err;
106
107    if (selinux_check_access(sctx, tctx, "property_service", "set", (void*) name) == 0)
108        result = 1;
109
110    freecon(tctx);
111 err:
112    return result;
113}
114
115static int check_control_mac_perms(const char *name, char *sctx)
116{
117    /*
118     *  Create a name prefix out of ctl.<service name>
119     *  The new prefix allows the use of the existing
120     *  property service backend labeling while avoiding
121     *  mislabels based on true property prefixes.
122     */
123    char ctl_name[PROP_VALUE_MAX+4];
124    int ret = snprintf(ctl_name, sizeof(ctl_name), "ctl.%s", name);
125
126    if (ret < 0 || (size_t) ret >= sizeof(ctl_name))
127        return 0;
128
129    return check_mac_perms(ctl_name, sctx);
130}
131
132/*
133 * Checks permissions for setting system properties.
134 * Returns 1 if uid allowed, 0 otherwise.
135 */
136static int check_perms(const char *name, char *sctx)
137{
138    if(!strncmp(name, "ro.", 3))
139        name +=3;
140
141    return check_mac_perms(name, sctx);
142}
143
144std::string property_get(const char* name) {
145    char value[PROP_VALUE_MAX] = {0};
146    __system_property_get(name, value);
147    return value;
148}
149
150static void write_persistent_property(const char *name, const char *value)
151{
152    char tempPath[PATH_MAX];
153    char path[PATH_MAX];
154    int fd;
155
156    snprintf(tempPath, sizeof(tempPath), "%s/.temp.XXXXXX", PERSISTENT_PROPERTY_DIR);
157    fd = mkstemp(tempPath);
158    if (fd < 0) {
159        ERROR("Unable to write persistent property to temp file %s: %s\n", tempPath, strerror(errno));
160        return;
161    }
162    write(fd, value, strlen(value));
163    fsync(fd);
164    close(fd);
165
166    snprintf(path, sizeof(path), "%s/%s", PERSISTENT_PROPERTY_DIR, name);
167    if (rename(tempPath, path)) {
168        unlink(tempPath);
169        ERROR("Unable to rename persistent property file %s to %s\n", tempPath, path);
170    }
171}
172
173static bool is_legal_property_name(const char* name, size_t namelen)
174{
175    size_t i;
176    if (namelen >= PROP_NAME_MAX) return false;
177    if (namelen < 1) return false;
178    if (name[0] == '.') return false;
179    if (name[namelen - 1] == '.') return false;
180
181    /* Only allow alphanumeric, plus '.', '-', or '_' */
182    /* Don't allow ".." to appear in a property name */
183    for (i = 0; i < namelen; i++) {
184        if (name[i] == '.') {
185            // i=0 is guaranteed to never have a dot. See above.
186            if (name[i-1] == '.') return false;
187            continue;
188        }
189        if (name[i] == '_' || name[i] == '-') continue;
190        if (name[i] >= 'a' && name[i] <= 'z') continue;
191        if (name[i] >= 'A' && name[i] <= 'Z') continue;
192        if (name[i] >= '0' && name[i] <= '9') continue;
193        return false;
194    }
195
196    return true;
197}
198
199static int property_set_impl(const char* name, const char* value) {
200    size_t namelen = strlen(name);
201    size_t valuelen = strlen(value);
202
203    if (!is_legal_property_name(name, namelen)) return -1;
204    if (valuelen >= PROP_VALUE_MAX) return -1;
205
206    if (strcmp("selinux.reload_policy", name) == 0 && strcmp("1", value) == 0) {
207        if (selinux_reload_policy() != 0) {
208            ERROR("Failed to reload policy\n");
209        }
210    } else if (strcmp("selinux.restorecon_recursive", name) == 0 && valuelen > 0) {
211        if (restorecon_recursive(value) != 0) {
212            ERROR("Failed to restorecon_recursive %s\n", value);
213        }
214    }
215
216    prop_info* pi = (prop_info*) __system_property_find(name);
217
218    if(pi != 0) {
219        /* ro.* properties may NEVER be modified once set */
220        if(!strncmp(name, "ro.", 3)) return -1;
221
222        __system_property_update(pi, value, valuelen);
223    } else {
224        int rc = __system_property_add(name, namelen, value, valuelen);
225        if (rc < 0) {
226            return rc;
227        }
228    }
229    /* If name starts with "net." treat as a DNS property. */
230    if (strncmp("net.", name, strlen("net.")) == 0)  {
231        if (strcmp("net.change", name) == 0) {
232            return 0;
233        }
234       /*
235        * The 'net.change' property is a special property used track when any
236        * 'net.*' property name is updated. It is _ONLY_ updated here. Its value
237        * contains the last updated 'net.*' property.
238        */
239        property_set("net.change", name);
240    } else if (persistent_properties_loaded &&
241            strncmp("persist.", name, strlen("persist.")) == 0) {
242        /*
243         * Don't write properties to disk until after we have read all default properties
244         * to prevent them from being overwritten by default values.
245         */
246        write_persistent_property(name, value);
247    }
248    property_changed(name, value);
249    return 0;
250}
251
252int property_set(const char* name, const char* value) {
253    int rc = property_set_impl(name, value);
254    if (rc == -1) {
255        ERROR("property_set(\"%s\", \"%s\") failed\n", name, value);
256    }
257    return rc;
258}
259
260static void handle_property_set_fd()
261{
262    prop_msg msg;
263    int s;
264    int r;
265    struct ucred cr;
266    struct sockaddr_un addr;
267    socklen_t addr_size = sizeof(addr);
268    socklen_t cr_size = sizeof(cr);
269    char * source_ctx = NULL;
270    struct pollfd ufds[1];
271    const int timeout_ms = 2 * 1000;  /* Default 2 sec timeout for caller to send property. */
272    int nr;
273
274    if ((s = accept(property_set_fd, (struct sockaddr *) &addr, &addr_size)) < 0) {
275        return;
276    }
277
278    /* Check socket options here */
279    if (getsockopt(s, SOL_SOCKET, SO_PEERCRED, &cr, &cr_size) < 0) {
280        close(s);
281        ERROR("Unable to receive socket options\n");
282        return;
283    }
284
285    ufds[0].fd = s;
286    ufds[0].events = POLLIN;
287    ufds[0].revents = 0;
288    nr = TEMP_FAILURE_RETRY(poll(ufds, 1, timeout_ms));
289    if (nr == 0) {
290        ERROR("sys_prop: timeout waiting for uid=%d to send property message.\n", cr.uid);
291        close(s);
292        return;
293    } else if (nr < 0) {
294        ERROR("sys_prop: error waiting for uid=%d to send property message: %s\n", cr.uid, strerror(errno));
295        close(s);
296        return;
297    }
298
299    r = TEMP_FAILURE_RETRY(recv(s, &msg, sizeof(msg), MSG_DONTWAIT));
300    if(r != sizeof(prop_msg)) {
301        ERROR("sys_prop: mis-match msg size received: %d expected: %zu: %s\n",
302              r, sizeof(prop_msg), strerror(errno));
303        close(s);
304        return;
305    }
306
307    switch(msg.cmd) {
308    case PROP_MSG_SETPROP:
309        msg.name[PROP_NAME_MAX-1] = 0;
310        msg.value[PROP_VALUE_MAX-1] = 0;
311
312        if (!is_legal_property_name(msg.name, strlen(msg.name))) {
313            ERROR("sys_prop: illegal property name. Got: \"%s\"\n", msg.name);
314            close(s);
315            return;
316        }
317
318        getpeercon(s, &source_ctx);
319
320        if(memcmp(msg.name,"ctl.",4) == 0) {
321            // Keep the old close-socket-early behavior when handling
322            // ctl.* properties.
323            close(s);
324            if (check_control_mac_perms(msg.value, source_ctx)) {
325                handle_control_message((char*) msg.name + 4, (char*) msg.value);
326            } else {
327                ERROR("sys_prop: Unable to %s service ctl [%s] uid:%d gid:%d pid:%d\n",
328                        msg.name + 4, msg.value, cr.uid, cr.gid, cr.pid);
329            }
330        } else {
331            if (check_perms(msg.name, source_ctx)) {
332                property_set((char*) msg.name, (char*) msg.value);
333            } else {
334                ERROR("sys_prop: permission denied uid:%d  name:%s\n",
335                      cr.uid, msg.name);
336            }
337
338            // Note: bionic's property client code assumes that the
339            // property server will not close the socket until *AFTER*
340            // the property is written to memory.
341            close(s);
342        }
343        freecon(source_ctx);
344        break;
345
346    default:
347        close(s);
348        break;
349    }
350}
351
352void get_property_workspace(int *fd, int *sz)
353{
354    *fd = pa_workspace.fd;
355    *sz = pa_workspace.size;
356}
357
358static void load_properties_from_file(const char *, const char *);
359
360/*
361 * Filter is used to decide which properties to load: NULL loads all keys,
362 * "ro.foo.*" is a prefix match, and "ro.foo.bar" is an exact match.
363 */
364static void load_properties(char *data, const char *filter)
365{
366    char *key, *value, *eol, *sol, *tmp, *fn;
367    size_t flen = 0;
368
369    if (filter) {
370        flen = strlen(filter);
371    }
372
373    sol = data;
374    while ((eol = strchr(sol, '\n'))) {
375        key = sol;
376        *eol++ = 0;
377        sol = eol;
378
379        while (isspace(*key)) key++;
380        if (*key == '#') continue;
381
382        tmp = eol - 2;
383        while ((tmp > key) && isspace(*tmp)) *tmp-- = 0;
384
385        if (!strncmp(key, "import ", 7) && flen == 0) {
386            fn = key + 7;
387            while (isspace(*fn)) fn++;
388
389            key = strchr(fn, ' ');
390            if (key) {
391                *key++ = 0;
392                while (isspace(*key)) key++;
393            }
394
395            load_properties_from_file(fn, key);
396
397        } else {
398            value = strchr(key, '=');
399            if (!value) continue;
400            *value++ = 0;
401
402            tmp = value - 2;
403            while ((tmp > key) && isspace(*tmp)) *tmp-- = 0;
404
405            while (isspace(*value)) value++;
406
407            if (flen > 0) {
408                if (filter[flen - 1] == '*') {
409                    if (strncmp(key, filter, flen - 1)) continue;
410                } else {
411                    if (strcmp(key, filter)) continue;
412                }
413            }
414
415            property_set(key, value);
416        }
417    }
418}
419
420/*
421 * Filter is used to decide which properties to load: NULL loads all keys,
422 * "ro.foo.*" is a prefix match, and "ro.foo.bar" is an exact match.
423 */
424static void load_properties_from_file(const char* filename, const char* filter) {
425    Timer t;
426    std::string data;
427    if (read_file(filename, &data)) {
428        data.push_back('\n');
429        load_properties(&data[0], filter);
430    }
431    NOTICE("(Loading properties from %s took %.2fs.)\n", filename, t.duration());
432}
433
434static void load_persistent_properties() {
435    persistent_properties_loaded = 1;
436
437    std::unique_ptr<DIR, int(*)(DIR*)> dir(opendir(PERSISTENT_PROPERTY_DIR), closedir);
438    if (!dir) {
439        ERROR("Unable to open persistent property directory \"%s\": %s\n",
440              PERSISTENT_PROPERTY_DIR, strerror(errno));
441        return;
442    }
443
444    struct dirent* entry;
445    while ((entry = readdir(dir.get())) != NULL) {
446        if (strncmp("persist.", entry->d_name, strlen("persist."))) {
447            continue;
448        }
449        if (entry->d_type != DT_REG) {
450            continue;
451        }
452
453        // Open the file and read the property value.
454        int fd = openat(dirfd(dir.get()), entry->d_name, O_RDONLY | O_NOFOLLOW);
455        if (fd == -1) {
456            ERROR("Unable to open persistent property file \"%s\": %s\n",
457                  entry->d_name, strerror(errno));
458            continue;
459        }
460
461        struct stat sb;
462        if (fstat(fd, &sb) == -1) {
463            ERROR("fstat on property file \"%s\" failed: %s\n", entry->d_name, strerror(errno));
464            close(fd);
465            continue;
466        }
467
468        // File must not be accessible to others, be owned by root/root, and
469        // not be a hard link to any other file.
470        if (((sb.st_mode & (S_IRWXG | S_IRWXO)) != 0) || (sb.st_uid != 0) || (sb.st_gid != 0) ||
471                (sb.st_nlink != 1)) {
472            ERROR("skipping insecure property file %s (uid=%u gid=%u nlink=%u mode=%o)\n",
473                  entry->d_name, (unsigned int)sb.st_uid, (unsigned int)sb.st_gid,
474                  (unsigned int)sb.st_nlink, sb.st_mode);
475            close(fd);
476            continue;
477        }
478
479        char value[PROP_VALUE_MAX];
480        int length = read(fd, value, sizeof(value) - 1);
481        if (length >= 0) {
482            value[length] = 0;
483            property_set(entry->d_name, value);
484        } else {
485            ERROR("Unable to read persistent property file %s: %s\n",
486                  entry->d_name, strerror(errno));
487        }
488        close(fd);
489    }
490}
491
492void property_load_boot_defaults() {
493    load_properties_from_file(PROP_PATH_RAMDISK_DEFAULT, NULL);
494}
495
496bool properties_initialized() {
497    return property_area_initialized;
498}
499
500static void load_override_properties() {
501    if (ALLOW_LOCAL_PROP_OVERRIDE) {
502        std::string debuggable = property_get("ro.debuggable");
503        if (debuggable == "1") {
504            load_properties_from_file(PROP_PATH_LOCAL_OVERRIDE, NULL);
505        }
506    }
507}
508
509/* When booting an encrypted system, /data is not mounted when the
510 * property service is started, so any properties stored there are
511 * not loaded.  Vold triggers init to load these properties once it
512 * has mounted /data.
513 */
514void load_persist_props(void) {
515    load_override_properties();
516    /* Read persistent properties after all default values have been loaded. */
517    load_persistent_properties();
518}
519
520void load_recovery_id_prop() {
521    std::string ro_hardware = property_get("ro.hardware");
522    if (ro_hardware.empty()) {
523        ERROR("ro.hardware not set - unable to load recovery id\n");
524        return;
525    }
526    std::string fstab_filename = FSTAB_PREFIX + ro_hardware;
527
528    std::unique_ptr<fstab, void(*)(fstab*)> tab(fs_mgr_read_fstab(fstab_filename.c_str()),
529            fs_mgr_free_fstab);
530    if (!tab) {
531        ERROR("unable to read fstab %s: %s\n", fstab_filename.c_str(), strerror(errno));
532        return;
533    }
534
535    fstab_rec* rec = fs_mgr_get_entry_for_mount_point(tab.get(), RECOVERY_MOUNT_POINT);
536    if (rec == NULL) {
537        ERROR("/recovery not specified in fstab\n");
538        return;
539    }
540
541    int fd = open(rec->blk_device, O_RDONLY);
542    if (fd == -1) {
543        ERROR("error opening block device %s: %s\n", rec->blk_device, strerror(errno));
544        return;
545    }
546
547    boot_img_hdr hdr;
548    if (android::base::ReadFully(fd, &hdr, sizeof(hdr))) {
549        std::string hex = bytes_to_hex(reinterpret_cast<uint8_t*>(hdr.id), sizeof(hdr.id));
550        property_set("ro.recovery_id", hex.c_str());
551    } else {
552        ERROR("error reading /recovery: %s\n", strerror(errno));
553    }
554
555    close(fd);
556}
557
558void load_all_props() {
559    load_properties_from_file(PROP_PATH_SYSTEM_BUILD, NULL);
560    load_properties_from_file(PROP_PATH_VENDOR_BUILD, NULL);
561    load_properties_from_file(PROP_PATH_FACTORY, "ro.*");
562
563    load_override_properties();
564
565    /* Read persistent properties after all default values have been loaded. */
566    load_persistent_properties();
567
568    load_recovery_id_prop();
569}
570
571void start_property_service() {
572    property_set_fd = create_socket(PROP_SERVICE_NAME, SOCK_STREAM | SOCK_CLOEXEC | SOCK_NONBLOCK,
573                                    0666, 0, 0, NULL);
574    if (property_set_fd == -1) {
575        ERROR("start_property_service socket creation failed: %s\n", strerror(errno));
576        exit(1);
577    }
578
579    listen(property_set_fd, 8);
580
581    register_epoll_handler(property_set_fd, handle_property_set_fd);
582}
583