property_service.cpp revision cce7e93b287835ffe9cdc3dad3fac52972d84560 
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    if (is_selinux_enabled() <= 0)
96        return 1;
97
98    char *tctx = NULL;
99    int result = 0;
100
101    if (!sctx)
102        goto err;
103
104    if (!sehandle_prop)
105        goto err;
106
107    if (selabel_lookup(sehandle_prop, &tctx, name, 1) != 0)
108        goto err;
109
110    if (selinux_check_access(sctx, tctx, "property_service", "set", (void*) name) == 0)
111        result = 1;
112
113    freecon(tctx);
114 err:
115    return result;
116}
117
118static int check_control_mac_perms(const char *name, char *sctx)
119{
120    /*
121     *  Create a name prefix out of ctl.<service name>
122     *  The new prefix allows the use of the existing
123     *  property service backend labeling while avoiding
124     *  mislabels based on true property prefixes.
125     */
126    char ctl_name[PROP_VALUE_MAX+4];
127    int ret = snprintf(ctl_name, sizeof(ctl_name), "ctl.%s", name);
128
129    if (ret < 0 || (size_t) ret >= sizeof(ctl_name))
130        return 0;
131
132    return check_mac_perms(ctl_name, sctx);
133}
134
135/*
136 * Checks permissions for setting system properties.
137 * Returns 1 if uid allowed, 0 otherwise.
138 */
139static int check_perms(const char *name, char *sctx)
140{
141    if(!strncmp(name, "ro.", 3))
142        name +=3;
143
144    return check_mac_perms(name, sctx);
145}
146
147int __property_get(const char *name, char *value)
148{
149    return __system_property_get(name, value);
150}
151
152static void write_persistent_property(const char *name, const char *value)
153{
154    char tempPath[PATH_MAX];
155    char path[PATH_MAX];
156    int fd;
157
158    snprintf(tempPath, sizeof(tempPath), "%s/.temp.XXXXXX", PERSISTENT_PROPERTY_DIR);
159    fd = mkstemp(tempPath);
160    if (fd < 0) {
161        ERROR("Unable to write persistent property to temp file %s: %s\n", tempPath, strerror(errno));
162        return;
163    }
164    write(fd, value, strlen(value));
165    fsync(fd);
166    close(fd);
167
168    snprintf(path, sizeof(path), "%s/%s", PERSISTENT_PROPERTY_DIR, name);
169    if (rename(tempPath, path)) {
170        unlink(tempPath);
171        ERROR("Unable to rename persistent property file %s to %s\n", tempPath, path);
172    }
173}
174
175static bool is_legal_property_name(const char* name, size_t namelen)
176{
177    size_t i;
178    if (namelen >= PROP_NAME_MAX) return false;
179    if (namelen < 1) return false;
180    if (name[0] == '.') return false;
181    if (name[namelen - 1] == '.') return false;
182
183    /* Only allow alphanumeric, plus '.', '-', or '_' */
184    /* Don't allow ".." to appear in a property name */
185    for (i = 0; i < namelen; i++) {
186        if (name[i] == '.') {
187            // i=0 is guaranteed to never have a dot. See above.
188            if (name[i-1] == '.') return false;
189            continue;
190        }
191        if (name[i] == '_' || name[i] == '-') continue;
192        if (name[i] >= 'a' && name[i] <= 'z') continue;
193        if (name[i] >= 'A' && name[i] <= 'Z') continue;
194        if (name[i] >= '0' && name[i] <= '9') continue;
195        return false;
196    }
197
198    return true;
199}
200
201static int property_set_impl(const char* name, const char* value) {
202    size_t namelen = strlen(name);
203    size_t valuelen = strlen(value);
204
205    if (!is_legal_property_name(name, namelen)) return -1;
206    if (valuelen >= PROP_VALUE_MAX) return -1;
207
208    prop_info* pi = (prop_info*) __system_property_find(name);
209
210    if(pi != 0) {
211        /* ro.* properties may NEVER be modified once set */
212        if(!strncmp(name, "ro.", 3)) return -1;
213
214        __system_property_update(pi, value, valuelen);
215    } else {
216        int rc = __system_property_add(name, namelen, value, valuelen);
217        if (rc < 0) {
218            return rc;
219        }
220    }
221    /* If name starts with "net." treat as a DNS property. */
222    if (strncmp("net.", name, strlen("net.")) == 0)  {
223        if (strcmp("net.change", name) == 0) {
224            return 0;
225        }
226       /*
227        * The 'net.change' property is a special property used track when any
228        * 'net.*' property name is updated. It is _ONLY_ updated here. Its value
229        * contains the last updated 'net.*' property.
230        */
231        property_set("net.change", name);
232    } else if (persistent_properties_loaded &&
233            strncmp("persist.", name, strlen("persist.")) == 0) {
234        /*
235         * Don't write properties to disk until after we have read all default properties
236         * to prevent them from being overwritten by default values.
237         */
238        write_persistent_property(name, value);
239    } else if (strcmp("selinux.reload_policy", name) == 0 &&
240               strcmp("1", value) == 0) {
241        selinux_reload_policy();
242    }
243    property_changed(name, value);
244    return 0;
245}
246
247int property_set(const char* name, const char* value) {
248    int rc = property_set_impl(name, value);
249    if (rc == -1) {
250        ERROR("property_set(\"%s\", \"%s\") failed\n", name, value);
251    }
252    return rc;
253}
254
255static void handle_property_set_fd()
256{
257    prop_msg msg;
258    int s;
259    int r;
260    struct ucred cr;
261    struct sockaddr_un addr;
262    socklen_t addr_size = sizeof(addr);
263    socklen_t cr_size = sizeof(cr);
264    char * source_ctx = NULL;
265    struct pollfd ufds[1];
266    const int timeout_ms = 2 * 1000;  /* Default 2 sec timeout for caller to send property. */
267    int nr;
268
269    if ((s = accept(property_set_fd, (struct sockaddr *) &addr, &addr_size)) < 0) {
270        return;
271    }
272
273    /* Check socket options here */
274    if (getsockopt(s, SOL_SOCKET, SO_PEERCRED, &cr, &cr_size) < 0) {
275        close(s);
276        ERROR("Unable to receive socket options\n");
277        return;
278    }
279
280    ufds[0].fd = s;
281    ufds[0].events = POLLIN;
282    ufds[0].revents = 0;
283    nr = TEMP_FAILURE_RETRY(poll(ufds, 1, timeout_ms));
284    if (nr == 0) {
285        ERROR("sys_prop: timeout waiting for uid=%d to send property message.\n", cr.uid);
286        close(s);
287        return;
288    } else if (nr < 0) {
289        ERROR("sys_prop: error waiting for uid=%d to send property message: %s\n", cr.uid, strerror(errno));
290        close(s);
291        return;
292    }
293
294    r = TEMP_FAILURE_RETRY(recv(s, &msg, sizeof(msg), MSG_DONTWAIT));
295    if(r != sizeof(prop_msg)) {
296        ERROR("sys_prop: mis-match msg size received: %d expected: %zu: %s\n",
297              r, sizeof(prop_msg), strerror(errno));
298        close(s);
299        return;
300    }
301
302    switch(msg.cmd) {
303    case PROP_MSG_SETPROP:
304        msg.name[PROP_NAME_MAX-1] = 0;
305        msg.value[PROP_VALUE_MAX-1] = 0;
306
307        if (!is_legal_property_name(msg.name, strlen(msg.name))) {
308            ERROR("sys_prop: illegal property name. Got: \"%s\"\n", msg.name);
309            close(s);
310            return;
311        }
312
313        getpeercon(s, &source_ctx);
314
315        if(memcmp(msg.name,"ctl.",4) == 0) {
316            // Keep the old close-socket-early behavior when handling
317            // ctl.* properties.
318            close(s);
319            if (check_control_mac_perms(msg.value, source_ctx)) {
320                handle_control_message((char*) msg.name + 4, (char*) msg.value);
321            } else {
322                ERROR("sys_prop: Unable to %s service ctl [%s] uid:%d gid:%d pid:%d\n",
323                        msg.name + 4, msg.value, cr.uid, cr.gid, cr.pid);
324            }
325        } else {
326            if (check_perms(msg.name, source_ctx)) {
327                property_set((char*) msg.name, (char*) msg.value);
328            } else {
329                ERROR("sys_prop: permission denied uid:%d  name:%s\n",
330                      cr.uid, msg.name);
331            }
332
333            // Note: bionic's property client code assumes that the
334            // property server will not close the socket until *AFTER*
335            // the property is written to memory.
336            close(s);
337        }
338        freecon(source_ctx);
339        break;
340
341    default:
342        close(s);
343        break;
344    }
345}
346
347void get_property_workspace(int *fd, int *sz)
348{
349    *fd = pa_workspace.fd;
350    *sz = pa_workspace.size;
351}
352
353static void load_properties_from_file(const char *, const char *);
354
355/*
356 * Filter is used to decide which properties to load: NULL loads all keys,
357 * "ro.foo.*" is a prefix match, and "ro.foo.bar" is an exact match.
358 */
359static void load_properties(char *data, const char *filter)
360{
361    char *key, *value, *eol, *sol, *tmp, *fn;
362    size_t flen = 0;
363
364    if (filter) {
365        flen = strlen(filter);
366    }
367
368    sol = data;
369    while ((eol = strchr(sol, '\n'))) {
370        key = sol;
371        *eol++ = 0;
372        sol = eol;
373
374        while (isspace(*key)) key++;
375        if (*key == '#') continue;
376
377        tmp = eol - 2;
378        while ((tmp > key) && isspace(*tmp)) *tmp-- = 0;
379
380        if (!strncmp(key, "import ", 7) && flen == 0) {
381            fn = key + 7;
382            while (isspace(*fn)) fn++;
383
384            key = strchr(fn, ' ');
385            if (key) {
386                *key++ = 0;
387                while (isspace(*key)) key++;
388            }
389
390            load_properties_from_file(fn, key);
391
392        } else {
393            value = strchr(key, '=');
394            if (!value) continue;
395            *value++ = 0;
396
397            tmp = value - 2;
398            while ((tmp > key) && isspace(*tmp)) *tmp-- = 0;
399
400            while (isspace(*value)) value++;
401
402            if (flen > 0) {
403                if (filter[flen - 1] == '*') {
404                    if (strncmp(key, filter, flen - 1)) continue;
405                } else {
406                    if (strcmp(key, filter)) continue;
407                }
408            }
409
410            property_set(key, value);
411        }
412    }
413}
414
415/*
416 * Filter is used to decide which properties to load: NULL loads all keys,
417 * "ro.foo.*" is a prefix match, and "ro.foo.bar" is an exact match.
418 */
419static void load_properties_from_file(const char* filename, const char* filter) {
420    Timer t;
421    std::string data;
422    if (read_file(filename, &data)) {
423        data.push_back('\n');
424        load_properties(&data[0], filter);
425    }
426    NOTICE("(Loading properties from %s took %.2fs.)\n", filename, t.duration());
427}
428
429static void load_persistent_properties() {
430    persistent_properties_loaded = 1;
431
432    std::unique_ptr<DIR, int(*)(DIR*)> dir(opendir(PERSISTENT_PROPERTY_DIR), closedir);
433    if (!dir) {
434        ERROR("Unable to open persistent property directory \"%s\": %s\n",
435              PERSISTENT_PROPERTY_DIR, strerror(errno));
436        return;
437    }
438
439    struct dirent* entry;
440    while ((entry = readdir(dir.get())) != NULL) {
441        if (strncmp("persist.", entry->d_name, strlen("persist."))) {
442            continue;
443        }
444        if (entry->d_type != DT_REG) {
445            continue;
446        }
447
448        // Open the file and read the property value.
449        int fd = openat(dirfd(dir.get()), entry->d_name, O_RDONLY | O_NOFOLLOW);
450        if (fd == -1) {
451            ERROR("Unable to open persistent property file \"%s\": %s\n",
452                  entry->d_name, strerror(errno));
453            continue;
454        }
455
456        struct stat sb;
457        if (fstat(fd, &sb) == -1) {
458            ERROR("fstat on property file \"%s\" failed: %s\n", entry->d_name, strerror(errno));
459            close(fd);
460            continue;
461        }
462
463        // File must not be accessible to others, be owned by root/root, and
464        // not be a hard link to any other file.
465        if (((sb.st_mode & (S_IRWXG | S_IRWXO)) != 0) || (sb.st_uid != 0) || (sb.st_gid != 0) ||
466                (sb.st_nlink != 1)) {
467            ERROR("skipping insecure property file %s (uid=%u gid=%u nlink=%u mode=%o)\n",
468                  entry->d_name, (unsigned int)sb.st_uid, (unsigned int)sb.st_gid,
469                  (unsigned int)sb.st_nlink, sb.st_mode);
470            close(fd);
471            continue;
472        }
473
474        char value[PROP_VALUE_MAX];
475        int length = read(fd, value, sizeof(value) - 1);
476        if (length >= 0) {
477            value[length] = 0;
478            property_set(entry->d_name, value);
479        } else {
480            ERROR("Unable to read persistent property file %s: %s\n",
481                  entry->d_name, strerror(errno));
482        }
483        close(fd);
484    }
485}
486
487void property_load_boot_defaults() {
488    load_properties_from_file(PROP_PATH_RAMDISK_DEFAULT, NULL);
489}
490
491bool properties_initialized() {
492    return property_area_initialized;
493}
494
495static void load_override_properties() {
496    if (ALLOW_LOCAL_PROP_OVERRIDE) {
497        char debuggable[PROP_VALUE_MAX];
498        int ret = property_get("ro.debuggable", debuggable);
499        if (ret && (strcmp(debuggable, "1") == 0)) {
500            load_properties_from_file(PROP_PATH_LOCAL_OVERRIDE, NULL);
501        }
502    }
503}
504
505/* When booting an encrypted system, /data is not mounted when the
506 * property service is started, so any properties stored there are
507 * not loaded.  Vold triggers init to load these properties once it
508 * has mounted /data.
509 */
510void load_persist_props(void) {
511    load_override_properties();
512    /* Read persistent properties after all default values have been loaded. */
513    load_persistent_properties();
514}
515
516void load_recovery_id_prop() {
517    char fstab_filename[PROP_VALUE_MAX + sizeof(FSTAB_PREFIX)];
518    char propbuf[PROP_VALUE_MAX];
519    int ret = property_get("ro.hardware", propbuf);
520    if (!ret) {
521        ERROR("ro.hardware not set - unable to load recovery id\n");
522        return;
523    }
524    snprintf(fstab_filename, sizeof(fstab_filename), FSTAB_PREFIX "%s", propbuf);
525
526    std::unique_ptr<fstab, void(*)(fstab*)> tab(fs_mgr_read_fstab(fstab_filename),
527            fs_mgr_free_fstab);
528    if (!tab) {
529        ERROR("unable to read fstab %s: %s\n", fstab_filename, strerror(errno));
530        return;
531    }
532
533    fstab_rec* rec = fs_mgr_get_entry_for_mount_point(tab.get(), RECOVERY_MOUNT_POINT);
534    if (rec == NULL) {
535        ERROR("/recovery not specified in fstab\n");
536        return;
537    }
538
539    int fd = open(rec->blk_device, O_RDONLY);
540    if (fd == -1) {
541        ERROR("error opening block device %s: %s\n", rec->blk_device, strerror(errno));
542        return;
543    }
544
545    boot_img_hdr hdr;
546    if (android::base::ReadFully(fd, &hdr, sizeof(hdr))) {
547        std::string hex = bytes_to_hex(reinterpret_cast<uint8_t*>(hdr.id), sizeof(hdr.id));
548        property_set("ro.recovery_id", hex.c_str());
549    } else {
550        ERROR("error reading /recovery: %s\n", strerror(errno));
551    }
552
553    close(fd);
554}
555
556void load_all_props() {
557    load_properties_from_file(PROP_PATH_SYSTEM_BUILD, NULL);
558    load_properties_from_file(PROP_PATH_VENDOR_BUILD, NULL);
559    load_properties_from_file(PROP_PATH_FACTORY, "ro.*");
560
561    load_override_properties();
562
563    /* Read persistent properties after all default values have been loaded. */
564    load_persistent_properties();
565
566    load_recovery_id_prop();
567}
568
569void start_property_service() {
570    property_set_fd = create_socket(PROP_SERVICE_NAME, SOCK_STREAM | SOCK_CLOEXEC | SOCK_NONBLOCK,
571                                    0666, 0, 0, NULL);
572    if (property_set_fd == -1) {
573        ERROR("start_property_service socket creation failed: %s\n", strerror(errno));
574        exit(1);
575    }
576
577    listen(property_set_fd, 8);
578
579    register_epoll_handler(property_set_fd, handle_property_set_fd);
580}
581