property_service.cpp revision dff18174d2779d65815a5b03956a30c13dd8e71c 
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 "property_service.h"
50#include "init.h"
51#include "util.h"
52#include "log.h"
53
54#define PERSISTENT_PROPERTY_DIR  "/data/property"
55
56static int persistent_properties_loaded = 0;
57static bool property_area_initialized = false;
58
59static int property_set_fd = -1;
60
61struct workspace {
62    size_t size;
63    int fd;
64};
65
66static workspace pa_workspace;
67
68void property_init() {
69    if (property_area_initialized) {
70        return;
71    }
72
73    property_area_initialized = true;
74
75    if (__system_property_area_init()) {
76        return;
77    }
78
79    pa_workspace.size = 0;
80    pa_workspace.fd = open(PROP_FILENAME, O_RDONLY | O_NOFOLLOW | O_CLOEXEC);
81    if (pa_workspace.fd == -1) {
82        ERROR("Failed to open %s: %s\n", PROP_FILENAME, strerror(errno));
83        return;
84    }
85}
86
87static int check_mac_perms(const char *name, char *sctx)
88{
89    if (is_selinux_enabled() <= 0)
90        return 1;
91
92    char *tctx = NULL;
93    int result = 0;
94
95    if (!sctx)
96        goto err;
97
98    if (!sehandle_prop)
99        goto err;
100
101    if (selabel_lookup(sehandle_prop, &tctx, name, 1) != 0)
102        goto err;
103
104    if (selinux_check_access(sctx, tctx, "property_service", "set", (void*) name) == 0)
105        result = 1;
106
107    freecon(tctx);
108 err:
109    return result;
110}
111
112static int check_control_mac_perms(const char *name, char *sctx)
113{
114    /*
115     *  Create a name prefix out of ctl.<service name>
116     *  The new prefix allows the use of the existing
117     *  property service backend labeling while avoiding
118     *  mislabels based on true property prefixes.
119     */
120    char ctl_name[PROP_VALUE_MAX+4];
121    int ret = snprintf(ctl_name, sizeof(ctl_name), "ctl.%s", name);
122
123    if (ret < 0 || (size_t) ret >= sizeof(ctl_name))
124        return 0;
125
126    return check_mac_perms(ctl_name, sctx);
127}
128
129/*
130 * Checks permissions for setting system properties.
131 * Returns 1 if uid allowed, 0 otherwise.
132 */
133static int check_perms(const char *name, char *sctx)
134{
135    if(!strncmp(name, "ro.", 3))
136        name +=3;
137
138    return check_mac_perms(name, sctx);
139}
140
141int __property_get(const char *name, char *value)
142{
143    return __system_property_get(name, value);
144}
145
146static void write_persistent_property(const char *name, const char *value)
147{
148    char tempPath[PATH_MAX];
149    char path[PATH_MAX];
150    int fd;
151
152    snprintf(tempPath, sizeof(tempPath), "%s/.temp.XXXXXX", PERSISTENT_PROPERTY_DIR);
153    fd = mkstemp(tempPath);
154    if (fd < 0) {
155        ERROR("Unable to write persistent property to temp file %s: %s\n", tempPath, strerror(errno));
156        return;
157    }
158    write(fd, value, strlen(value));
159    fsync(fd);
160    close(fd);
161
162    snprintf(path, sizeof(path), "%s/%s", PERSISTENT_PROPERTY_DIR, name);
163    if (rename(tempPath, path)) {
164        unlink(tempPath);
165        ERROR("Unable to rename persistent property file %s to %s\n", tempPath, path);
166    }
167}
168
169static bool is_legal_property_name(const char* name, size_t namelen)
170{
171    size_t i;
172    if (namelen >= PROP_NAME_MAX) return false;
173    if (namelen < 1) return false;
174    if (name[0] == '.') return false;
175    if (name[namelen - 1] == '.') return false;
176
177    /* Only allow alphanumeric, plus '.', '-', or '_' */
178    /* Don't allow ".." to appear in a property name */
179    for (i = 0; i < namelen; i++) {
180        if (name[i] == '.') {
181            // i=0 is guaranteed to never have a dot. See above.
182            if (name[i-1] == '.') return false;
183            continue;
184        }
185        if (name[i] == '_' || name[i] == '-') continue;
186        if (name[i] >= 'a' && name[i] <= 'z') continue;
187        if (name[i] >= 'A' && name[i] <= 'Z') continue;
188        if (name[i] >= '0' && name[i] <= '9') continue;
189        return false;
190    }
191
192    return true;
193}
194
195static int property_set_impl(const char* name, const char* value) {
196    size_t namelen = strlen(name);
197    size_t valuelen = strlen(value);
198
199    if (!is_legal_property_name(name, namelen)) return -1;
200    if (valuelen >= PROP_VALUE_MAX) return -1;
201
202    prop_info* pi = (prop_info*) __system_property_find(name);
203
204    if(pi != 0) {
205        /* ro.* properties may NEVER be modified once set */
206        if(!strncmp(name, "ro.", 3)) return -1;
207
208        __system_property_update(pi, value, valuelen);
209    } else {
210        int rc = __system_property_add(name, namelen, value, valuelen);
211        if (rc < 0) {
212            return rc;
213        }
214    }
215    /* If name starts with "net." treat as a DNS property. */
216    if (strncmp("net.", name, strlen("net.")) == 0)  {
217        if (strcmp("net.change", name) == 0) {
218            return 0;
219        }
220       /*
221        * The 'net.change' property is a special property used track when any
222        * 'net.*' property name is updated. It is _ONLY_ updated here. Its value
223        * contains the last updated 'net.*' property.
224        */
225        property_set("net.change", name);
226    } else if (persistent_properties_loaded &&
227            strncmp("persist.", name, strlen("persist.")) == 0) {
228        /*
229         * Don't write properties to disk until after we have read all default properties
230         * to prevent them from being overwritten by default values.
231         */
232        write_persistent_property(name, value);
233    } else if (strcmp("selinux.reload_policy", name) == 0 &&
234               strcmp("1", value) == 0) {
235        selinux_reload_policy();
236    }
237    property_changed(name, value);
238    return 0;
239}
240
241int property_set(const char* name, const char* value) {
242    int rc = property_set_impl(name, value);
243    if (rc == -1) {
244        ERROR("property_set(\"%s\", \"%s\") failed\n", name, value);
245    }
246    return rc;
247}
248
249static void handle_property_set_fd()
250{
251    prop_msg msg;
252    int s;
253    int r;
254    struct ucred cr;
255    struct sockaddr_un addr;
256    socklen_t addr_size = sizeof(addr);
257    socklen_t cr_size = sizeof(cr);
258    char * source_ctx = NULL;
259    struct pollfd ufds[1];
260    const int timeout_ms = 2 * 1000;  /* Default 2 sec timeout for caller to send property. */
261    int nr;
262
263    if ((s = accept(property_set_fd, (struct sockaddr *) &addr, &addr_size)) < 0) {
264        return;
265    }
266
267    /* Check socket options here */
268    if (getsockopt(s, SOL_SOCKET, SO_PEERCRED, &cr, &cr_size) < 0) {
269        close(s);
270        ERROR("Unable to receive socket options\n");
271        return;
272    }
273
274    ufds[0].fd = s;
275    ufds[0].events = POLLIN;
276    ufds[0].revents = 0;
277    nr = TEMP_FAILURE_RETRY(poll(ufds, 1, timeout_ms));
278    if (nr == 0) {
279        ERROR("sys_prop: timeout waiting for uid=%d to send property message.\n", cr.uid);
280        close(s);
281        return;
282    } else if (nr < 0) {
283        ERROR("sys_prop: error waiting for uid=%d to send property message: %s\n", cr.uid, strerror(errno));
284        close(s);
285        return;
286    }
287
288    r = TEMP_FAILURE_RETRY(recv(s, &msg, sizeof(msg), MSG_DONTWAIT));
289    if(r != sizeof(prop_msg)) {
290        ERROR("sys_prop: mis-match msg size received: %d expected: %zu: %s\n",
291              r, sizeof(prop_msg), strerror(errno));
292        close(s);
293        return;
294    }
295
296    switch(msg.cmd) {
297    case PROP_MSG_SETPROP:
298        msg.name[PROP_NAME_MAX-1] = 0;
299        msg.value[PROP_VALUE_MAX-1] = 0;
300
301        if (!is_legal_property_name(msg.name, strlen(msg.name))) {
302            ERROR("sys_prop: illegal property name. Got: \"%s\"\n", msg.name);
303            close(s);
304            return;
305        }
306
307        getpeercon(s, &source_ctx);
308
309        if(memcmp(msg.name,"ctl.",4) == 0) {
310            // Keep the old close-socket-early behavior when handling
311            // ctl.* properties.
312            close(s);
313            if (check_control_mac_perms(msg.value, source_ctx)) {
314                handle_control_message((char*) msg.name + 4, (char*) msg.value);
315            } else {
316                ERROR("sys_prop: Unable to %s service ctl [%s] uid:%d gid:%d pid:%d\n",
317                        msg.name + 4, msg.value, cr.uid, cr.gid, cr.pid);
318            }
319        } else {
320            if (check_perms(msg.name, source_ctx)) {
321                property_set((char*) msg.name, (char*) msg.value);
322            } else {
323                ERROR("sys_prop: permission denied uid:%d  name:%s\n",
324                      cr.uid, msg.name);
325            }
326
327            // Note: bionic's property client code assumes that the
328            // property server will not close the socket until *AFTER*
329            // the property is written to memory.
330            close(s);
331        }
332        freecon(source_ctx);
333        break;
334
335    default:
336        close(s);
337        break;
338    }
339}
340
341void get_property_workspace(int *fd, int *sz)
342{
343    *fd = pa_workspace.fd;
344    *sz = pa_workspace.size;
345}
346
347static void load_properties_from_file(const char *, const char *);
348
349/*
350 * Filter is used to decide which properties to load: NULL loads all keys,
351 * "ro.foo.*" is a prefix match, and "ro.foo.bar" is an exact match.
352 */
353static void load_properties(char *data, const char *filter)
354{
355    char *key, *value, *eol, *sol, *tmp, *fn;
356    size_t flen = 0;
357
358    if (filter) {
359        flen = strlen(filter);
360    }
361
362    sol = data;
363    while ((eol = strchr(sol, '\n'))) {
364        key = sol;
365        *eol++ = 0;
366        sol = eol;
367
368        while (isspace(*key)) key++;
369        if (*key == '#') continue;
370
371        tmp = eol - 2;
372        while ((tmp > key) && isspace(*tmp)) *tmp-- = 0;
373
374        if (!strncmp(key, "import ", 7) && flen == 0) {
375            fn = key + 7;
376            while (isspace(*fn)) fn++;
377
378            key = strchr(fn, ' ');
379            if (key) {
380                *key++ = 0;
381                while (isspace(*key)) key++;
382            }
383
384            load_properties_from_file(fn, key);
385
386        } else {
387            value = strchr(key, '=');
388            if (!value) continue;
389            *value++ = 0;
390
391            tmp = value - 2;
392            while ((tmp > key) && isspace(*tmp)) *tmp-- = 0;
393
394            while (isspace(*value)) value++;
395
396            if (flen > 0) {
397                if (filter[flen - 1] == '*') {
398                    if (strncmp(key, filter, flen - 1)) continue;
399                } else {
400                    if (strcmp(key, filter)) continue;
401                }
402            }
403
404            property_set(key, value);
405        }
406    }
407}
408
409/*
410 * Filter is used to decide which properties to load: NULL loads all keys,
411 * "ro.foo.*" is a prefix match, and "ro.foo.bar" is an exact match.
412 */
413static void load_properties_from_file(const char* filename, const char* filter) {
414    Timer t;
415    std::string data;
416    if (read_file(filename, &data)) {
417        load_properties(&data[0], filter);
418    }
419    NOTICE("(Loading properties from %s took %.2fs.)\n", filename, t.duration());
420}
421
422static void load_persistent_properties() {
423    persistent_properties_loaded = 1;
424
425    std::unique_ptr<DIR, int(*)(DIR*)> dir(opendir(PERSISTENT_PROPERTY_DIR), closedir);
426    if (!dir) {
427        ERROR("Unable to open persistent property directory \"%s\": %s\n",
428              PERSISTENT_PROPERTY_DIR, strerror(errno));
429        return;
430    }
431
432    struct dirent* entry;
433    while ((entry = readdir(dir.get())) != NULL) {
434        if (strncmp("persist.", entry->d_name, strlen("persist."))) {
435            continue;
436        }
437        if (entry->d_type != DT_REG) {
438            continue;
439        }
440
441        // Open the file and read the property value.
442        int fd = openat(dirfd(dir.get()), entry->d_name, O_RDONLY | O_NOFOLLOW);
443        if (fd == -1) {
444            ERROR("Unable to open persistent property file \"%s\": %s\n",
445                  entry->d_name, strerror(errno));
446            continue;
447        }
448
449        struct stat sb;
450        if (fstat(fd, &sb) == -1) {
451            ERROR("fstat on property file \"%s\" failed: %s\n", entry->d_name, strerror(errno));
452            close(fd);
453            continue;
454        }
455
456        // File must not be accessible to others, be owned by root/root, and
457        // not be a hard link to any other file.
458        if (((sb.st_mode & (S_IRWXG | S_IRWXO)) != 0) || (sb.st_uid != 0) || (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        char value[PROP_VALUE_MAX];
468        int length = read(fd, value, sizeof(value) - 1);
469        if (length >= 0) {
470            value[length] = 0;
471            property_set(entry->d_name, value);
472        } else {
473            ERROR("Unable to read persistent property file %s: %s\n",
474                  entry->d_name, strerror(errno));
475        }
476        close(fd);
477    }
478}
479
480void property_load_boot_defaults() {
481    load_properties_from_file(PROP_PATH_RAMDISK_DEFAULT, NULL);
482}
483
484bool properties_initialized() {
485    return property_area_initialized;
486}
487
488static void load_override_properties() {
489    if (ALLOW_LOCAL_PROP_OVERRIDE) {
490        char debuggable[PROP_VALUE_MAX];
491        int ret = property_get("ro.debuggable", debuggable);
492        if (ret && (strcmp(debuggable, "1") == 0)) {
493            load_properties_from_file(PROP_PATH_LOCAL_OVERRIDE, NULL);
494        }
495    }
496}
497
498/* When booting an encrypted system, /data is not mounted when the
499 * property service is started, so any properties stored there are
500 * not loaded.  Vold triggers init to load these properties once it
501 * has mounted /data.
502 */
503void load_persist_props(void) {
504    load_override_properties();
505    /* Read persistent properties after all default values have been loaded. */
506    load_persistent_properties();
507}
508
509void load_all_props() {
510    load_properties_from_file(PROP_PATH_SYSTEM_BUILD, NULL);
511    load_properties_from_file(PROP_PATH_VENDOR_BUILD, NULL);
512    load_properties_from_file(PROP_PATH_FACTORY, "ro.*");
513
514    load_override_properties();
515
516    /* Read persistent properties after all default values have been loaded. */
517    load_persistent_properties();
518}
519
520void start_property_service() {
521    property_set_fd = create_socket(PROP_SERVICE_NAME, SOCK_STREAM | SOCK_CLOEXEC | SOCK_NONBLOCK,
522                                    0666, 0, 0, NULL);
523    if (property_set_fd == -1) {
524        ERROR("start_property_service socket creation failed: %s\n", strerror(errno));
525        exit(1);
526    }
527
528    listen(property_set_fd, 8);
529
530    register_epoll_handler(property_set_fd, handle_property_set_fd);
531}
532