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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/multiuser.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 <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 
54 static int persistent_properties_loaded = 0;
55 static int property_area_inited = 0;
56 
57 static int property_set_fd = -1;
58 
59 /* White list of permissions for setting property services. */
60 struct {
61     const char *prefix;
62     unsigned int uid;
63     unsigned int gid;
64 } property_perms[] = {
65     { "net.rmnet0.",      AID_RADIO,    0 },
66     { "net.gprs.",        AID_RADIO,    0 },
67     { "net.ppp",          AID_RADIO,    0 },
68     { "net.qmi",          AID_RADIO,    0 },
69     { "net.lte",          AID_RADIO,    0 },
70     { "net.cdma",         AID_RADIO,    0 },
71     { "ril.",             AID_RADIO,    0 },
72     { "gsm.",             AID_RADIO,    0 },
73     { "persist.radio",    AID_RADIO,    0 },
74     { "net.dns",          AID_RADIO,    0 },
75     { "sys.usb.config",   AID_RADIO,    0 },
76     { "net.",             AID_SYSTEM,   0 },
77     { "dev.",             AID_SYSTEM,   0 },
78     { "runtime.",         AID_SYSTEM,   0 },
79     { "hw.",              AID_SYSTEM,   0 },
80     { "sys.",             AID_SYSTEM,   0 },
81     { "service.",         AID_SYSTEM,   0 },
82     { "wlan.",            AID_SYSTEM,   0 },
83     { "bluetooth.",       AID_BLUETOOTH,   0 },
84     { "dhcp.",            AID_SYSTEM,   0 },
85     { "dhcp.",            AID_DHCP,     0 },
86     { "debug.",           AID_SYSTEM,   0 },
87     { "debug.",           AID_SHELL,    0 },
88     { "log.",             AID_SHELL,    0 },
89     { "service.adb.root", AID_SHELL,    0 },
90     { "service.adb.tcp.port", AID_SHELL,    0 },
91     { "persist.sys.",     AID_SYSTEM,   0 },
92     { "persist.service.", AID_SYSTEM,   0 },
93     { "persist.security.", AID_SYSTEM,   0 },
94     { "persist.service.bdroid.", AID_BLUETOOTH,   0 },
95     { "selinux."         , AID_SYSTEM,   0 },
96     { NULL, 0, 0 }
97 };
98 
99 /*
100  * White list of UID that are allowed to start/stop services.
101  * Currently there are no user apps that require.
102  */
103 struct {
104     const char *service;
105     unsigned int uid;
106     unsigned int gid;
107 } control_perms[] = {
108     { "dumpstate",AID_SHELL, AID_LOG },
109     { "ril-daemon",AID_RADIO, AID_RADIO },
110      {NULL, 0, 0 }
111 };
112 
113 typedef struct {
114     void *data;
115     size_t size;
116     int fd;
117 } workspace;
118 
init_workspace(workspace * w,size_t size)119 static int init_workspace(workspace *w, size_t size)
120 {
121     void *data;
122     int fd;
123 
124         /* dev is a tmpfs that we can use to carve a shared workspace
125          * out of, so let's do that...
126          */
127     fd = open(PROP_FILENAME, O_RDWR | O_CREAT | O_NOFOLLOW, 0644);
128     if (fd < 0)
129         return -1;
130 
131     if (ftruncate(fd, size) < 0)
132         goto out;
133 
134     data = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
135     if(data == MAP_FAILED)
136         goto out;
137 
138     close(fd);
139 
140     fd = open(PROP_FILENAME, O_RDONLY | O_NOFOLLOW);
141     if (fd < 0)
142         return -1;
143 
144     w->data = data;
145     w->size = size;
146     w->fd = fd;
147     return 0;
148 
149 out:
150     close(fd);
151     return -1;
152 }
153 
154 /* (8 header words + 247 toc words) = 1020 bytes */
155 /* 1024 bytes header and toc + 247 prop_infos @ 128 bytes = 32640 bytes */
156 
157 #define PA_COUNT_MAX  247
158 #define PA_INFO_START 1024
159 #define PA_SIZE       32768
160 
161 static workspace pa_workspace;
162 static prop_info *pa_info_array;
163 
164 extern prop_area *__system_property_area__;
165 
init_property_area(void)166 static int init_property_area(void)
167 {
168     prop_area *pa;
169 
170     if(pa_info_array)
171         return -1;
172 
173     if(init_workspace(&pa_workspace, PA_SIZE))
174         return -1;
175 
176     fcntl(pa_workspace.fd, F_SETFD, FD_CLOEXEC);
177 
178     pa_info_array = (void*) (((char*) pa_workspace.data) + PA_INFO_START);
179 
180     pa = pa_workspace.data;
181     memset(pa, 0, PA_SIZE);
182     pa->magic = PROP_AREA_MAGIC;
183     pa->version = PROP_AREA_VERSION;
184 
185         /* plug into the lib property services */
186     __system_property_area__ = pa;
187     property_area_inited = 1;
188     return 0;
189 }
190 
update_prop_info(prop_info * pi,const char * value,unsigned len)191 static void update_prop_info(prop_info *pi, const char *value, unsigned len)
192 {
193     pi->serial = pi->serial | 1;
194     memcpy(pi->value, value, len + 1);
195     pi->serial = (len << 24) | ((pi->serial + 1) & 0xffffff);
196     __futex_wake(&pi->serial, INT32_MAX);
197 }
198 
check_mac_perms(const char * name,char * sctx)199 static int check_mac_perms(const char *name, char *sctx)
200 {
201     if (is_selinux_enabled() <= 0)
202         return 1;
203 
204     char *tctx = NULL;
205     const char *class = "property_service";
206     const char *perm = "set";
207     int result = 0;
208 
209     if (!sctx)
210         goto err;
211 
212     if (!sehandle_prop)
213         goto err;
214 
215     if (selabel_lookup(sehandle_prop, &tctx, name, 1) != 0)
216         goto err;
217 
218     if (selinux_check_access(sctx, tctx, class, perm, name) == 0)
219         result = 1;
220 
221     freecon(tctx);
222  err:
223     return result;
224 }
225 
check_control_mac_perms(const char * name,char * sctx)226 static int check_control_mac_perms(const char *name, char *sctx)
227 {
228     /*
229      *  Create a name prefix out of ctl.<service name>
230      *  The new prefix allows the use of the existing
231      *  property service backend labeling while avoiding
232      *  mislabels based on true property prefixes.
233      */
234     char ctl_name[PROP_VALUE_MAX+4];
235     int ret = snprintf(ctl_name, sizeof(ctl_name), "ctl.%s", name);
236 
237     if (ret < 0 || (size_t) ret >= sizeof(ctl_name))
238         return 0;
239 
240     return check_mac_perms(ctl_name, sctx);
241 }
242 
243 /*
244  * Checks permissions for starting/stoping system services.
245  * AID_SYSTEM and AID_ROOT are always allowed.
246  *
247  * Returns 1 if uid allowed, 0 otherwise.
248  */
check_control_perms(const char * name,unsigned int uid,unsigned int gid,char * sctx)249 static int check_control_perms(const char *name, unsigned int uid, unsigned int gid, char *sctx) {
250 
251     int i;
252     if (uid == AID_SYSTEM || uid == AID_ROOT)
253       return check_control_mac_perms(name, sctx);
254 
255     /* Search the ACL */
256     for (i = 0; control_perms[i].service; i++) {
257         if (strcmp(control_perms[i].service, name) == 0) {
258             if ((uid && control_perms[i].uid == uid) ||
259                 (gid && control_perms[i].gid == gid)) {
260                 return check_control_mac_perms(name, sctx);
261             }
262         }
263     }
264     return 0;
265 }
266 
267 /*
268  * Checks permissions for setting system properties.
269  * Returns 1 if uid allowed, 0 otherwise.
270  */
check_perms(const char * name,unsigned int uid,unsigned int gid,char * sctx)271 static int check_perms(const char *name, unsigned int uid, unsigned int gid, char *sctx)
272 {
273     int i;
274     unsigned int app_id;
275 
276     if(!strncmp(name, "ro.", 3))
277         name +=3;
278 
279     if (uid == 0)
280         return check_mac_perms(name, sctx);
281 
282     app_id = multiuser_get_app_id(uid);
283     if (app_id == AID_BLUETOOTH) {
284         uid = app_id;
285     }
286 
287     for (i = 0; property_perms[i].prefix; i++) {
288         if (strncmp(property_perms[i].prefix, name,
289                     strlen(property_perms[i].prefix)) == 0) {
290             if ((uid && property_perms[i].uid == uid) ||
291                 (gid && property_perms[i].gid == gid)) {
292 
293                 return check_mac_perms(name, sctx);
294             }
295         }
296     }
297 
298     return 0;
299 }
300 
property_get(const char * name)301 const char* property_get(const char *name)
302 {
303     prop_info *pi;
304 
305     if(strlen(name) >= PROP_NAME_MAX) return 0;
306 
307     pi = (prop_info*) __system_property_find(name);
308 
309     if(pi != 0) {
310         return pi->value;
311     } else {
312         return 0;
313     }
314 }
315 
write_persistent_property(const char * name,const char * value)316 static void write_persistent_property(const char *name, const char *value)
317 {
318     char tempPath[PATH_MAX];
319     char path[PATH_MAX];
320     int fd;
321 
322     snprintf(tempPath, sizeof(tempPath), "%s/.temp.XXXXXX", PERSISTENT_PROPERTY_DIR);
323     fd = mkstemp(tempPath);
324     if (fd < 0) {
325         ERROR("Unable to write persistent property to temp file %s errno: %d\n", tempPath, errno);
326         return;
327     }
328     write(fd, value, strlen(value));
329     close(fd);
330 
331     snprintf(path, sizeof(path), "%s/%s", PERSISTENT_PROPERTY_DIR, name);
332     if (rename(tempPath, path)) {
333         unlink(tempPath);
334         ERROR("Unable to rename persistent property file %s to %s\n", tempPath, path);
335     }
336 }
337 
property_set(const char * name,const char * value)338 int property_set(const char *name, const char *value)
339 {
340     prop_area *pa;
341     prop_info *pi;
342 
343     size_t namelen = strlen(name);
344     size_t valuelen = strlen(value);
345 
346     if(namelen >= PROP_NAME_MAX) return -1;
347     if(valuelen >= PROP_VALUE_MAX) return -1;
348     if(namelen < 1) return -1;
349 
350     pi = (prop_info*) __system_property_find(name);
351 
352     if(pi != 0) {
353         /* ro.* properties may NEVER be modified once set */
354         if(!strncmp(name, "ro.", 3)) return -1;
355 
356         pa = __system_property_area__;
357         update_prop_info(pi, value, valuelen);
358         pa->serial++;
359         __futex_wake(&pa->serial, INT32_MAX);
360     } else {
361         pa = __system_property_area__;
362         if(pa->count == PA_COUNT_MAX) return -1;
363 
364         pi = pa_info_array + pa->count;
365         pi->serial = (valuelen << 24);
366         memcpy(pi->name, name, namelen + 1);
367         memcpy(pi->value, value, valuelen + 1);
368 
369         pa->toc[pa->count] =
370             (namelen << 24) | (((unsigned) pi) - ((unsigned) pa));
371 
372         pa->count++;
373         pa->serial++;
374         __futex_wake(&pa->serial, INT32_MAX);
375     }
376     /* If name starts with "net." treat as a DNS property. */
377     if (strncmp("net.", name, strlen("net.")) == 0)  {
378         if (strcmp("net.change", name) == 0) {
379             return 0;
380         }
381        /*
382         * The 'net.change' property is a special property used track when any
383         * 'net.*' property name is updated. It is _ONLY_ updated here. Its value
384         * contains the last updated 'net.*' property.
385         */
386         property_set("net.change", name);
387     } else if (persistent_properties_loaded &&
388             strncmp("persist.", name, strlen("persist.")) == 0) {
389         /*
390          * Don't write properties to disk until after we have read all default properties
391          * to prevent them from being overwritten by default values.
392          */
393         write_persistent_property(name, value);
394     } else if (strcmp("selinux.reload_policy", name) == 0 &&
395                strcmp("1", value) == 0) {
396         selinux_reload_policy();
397     }
398     property_changed(name, value);
399     return 0;
400 }
401 
handle_property_set_fd()402 void handle_property_set_fd()
403 {
404     prop_msg msg;
405     int s;
406     int r;
407     int res;
408     struct ucred cr;
409     struct sockaddr_un addr;
410     socklen_t addr_size = sizeof(addr);
411     socklen_t cr_size = sizeof(cr);
412     char * source_ctx = NULL;
413 
414     if ((s = accept(property_set_fd, (struct sockaddr *) &addr, &addr_size)) < 0) {
415         return;
416     }
417 
418     /* Check socket options here */
419     if (getsockopt(s, SOL_SOCKET, SO_PEERCRED, &cr, &cr_size) < 0) {
420         close(s);
421         ERROR("Unable to receive socket options\n");
422         return;
423     }
424 
425     r = TEMP_FAILURE_RETRY(recv(s, &msg, sizeof(msg), 0));
426     if(r != sizeof(prop_msg)) {
427         ERROR("sys_prop: mis-match msg size received: %d expected: %d errno: %d\n",
428               r, sizeof(prop_msg), errno);
429         close(s);
430         return;
431     }
432 
433     switch(msg.cmd) {
434     case PROP_MSG_SETPROP:
435         msg.name[PROP_NAME_MAX-1] = 0;
436         msg.value[PROP_VALUE_MAX-1] = 0;
437 
438         getpeercon(s, &source_ctx);
439 
440         if(memcmp(msg.name,"ctl.",4) == 0) {
441             // Keep the old close-socket-early behavior when handling
442             // ctl.* properties.
443             close(s);
444             if (check_control_perms(msg.value, cr.uid, cr.gid, source_ctx)) {
445                 handle_control_message((char*) msg.name + 4, (char*) msg.value);
446             } else {
447                 ERROR("sys_prop: Unable to %s service ctl [%s] uid:%d gid:%d pid:%d\n",
448                         msg.name + 4, msg.value, cr.uid, cr.gid, cr.pid);
449             }
450         } else {
451             if (check_perms(msg.name, cr.uid, cr.gid, source_ctx)) {
452                 property_set((char*) msg.name, (char*) msg.value);
453             } else {
454                 ERROR("sys_prop: permission denied uid:%d  name:%s\n",
455                       cr.uid, msg.name);
456             }
457 
458             // Note: bionic's property client code assumes that the
459             // property server will not close the socket until *AFTER*
460             // the property is written to memory.
461             close(s);
462         }
463         freecon(source_ctx);
464         break;
465 
466     default:
467         close(s);
468         break;
469     }
470 }
471 
get_property_workspace(int * fd,int * sz)472 void get_property_workspace(int *fd, int *sz)
473 {
474     *fd = pa_workspace.fd;
475     *sz = pa_workspace.size;
476 }
477 
load_properties(char * data)478 static void load_properties(char *data)
479 {
480     char *key, *value, *eol, *sol, *tmp;
481 
482     sol = data;
483     while((eol = strchr(sol, '\n'))) {
484         key = sol;
485         *eol++ = 0;
486         sol = eol;
487 
488         value = strchr(key, '=');
489         if(value == 0) continue;
490         *value++ = 0;
491 
492         while(isspace(*key)) key++;
493         if(*key == '#') continue;
494         tmp = value - 2;
495         while((tmp > key) && isspace(*tmp)) *tmp-- = 0;
496 
497         while(isspace(*value)) value++;
498         tmp = eol - 2;
499         while((tmp > value) && isspace(*tmp)) *tmp-- = 0;
500 
501         property_set(key, value);
502     }
503 }
504 
load_properties_from_file(const char * fn)505 static void load_properties_from_file(const char *fn)
506 {
507     char *data;
508     unsigned sz;
509 
510     data = read_file(fn, &sz);
511 
512     if(data != 0) {
513         load_properties(data);
514         free(data);
515     }
516 }
517 
load_persistent_properties()518 static void load_persistent_properties()
519 {
520     DIR* dir = opendir(PERSISTENT_PROPERTY_DIR);
521     int dir_fd;
522     struct dirent*  entry;
523     char value[PROP_VALUE_MAX];
524     int fd, length;
525     struct stat sb;
526 
527     if (dir) {
528         dir_fd = dirfd(dir);
529         while ((entry = readdir(dir)) != NULL) {
530             if (strncmp("persist.", entry->d_name, strlen("persist.")))
531                 continue;
532 #if HAVE_DIRENT_D_TYPE
533             if (entry->d_type != DT_REG)
534                 continue;
535 #endif
536             /* open the file and read the property value */
537             fd = openat(dir_fd, entry->d_name, O_RDONLY | O_NOFOLLOW);
538             if (fd < 0) {
539                 ERROR("Unable to open persistent property file \"%s\" errno: %d\n",
540                       entry->d_name, errno);
541                 continue;
542             }
543             if (fstat(fd, &sb) < 0) {
544                 ERROR("fstat on property file \"%s\" failed errno: %d\n", entry->d_name, errno);
545                 close(fd);
546                 continue;
547             }
548 
549             // File must not be accessible to others, be owned by root/root, and
550             // not be a hard link to any other file.
551             if (((sb.st_mode & (S_IRWXG | S_IRWXO)) != 0)
552                     || (sb.st_uid != 0)
553                     || (sb.st_gid != 0)
554                     || (sb.st_nlink != 1)) {
555                 ERROR("skipping insecure property file %s (uid=%lu gid=%lu nlink=%d mode=%o)\n",
556                       entry->d_name, sb.st_uid, sb.st_gid, sb.st_nlink, sb.st_mode);
557                 close(fd);
558                 continue;
559             }
560 
561             length = read(fd, value, sizeof(value) - 1);
562             if (length >= 0) {
563                 value[length] = 0;
564                 property_set(entry->d_name, value);
565             } else {
566                 ERROR("Unable to read persistent property file %s errno: %d\n",
567                       entry->d_name, errno);
568             }
569             close(fd);
570         }
571         closedir(dir);
572     } else {
573         ERROR("Unable to open persistent property directory %s errno: %d\n", PERSISTENT_PROPERTY_DIR, errno);
574     }
575 
576     persistent_properties_loaded = 1;
577 }
578 
property_init(void)579 void property_init(void)
580 {
581     init_property_area();
582 }
583 
property_load_boot_defaults(void)584 void property_load_boot_defaults(void)
585 {
586     load_properties_from_file(PROP_PATH_RAMDISK_DEFAULT);
587 }
588 
properties_inited(void)589 int properties_inited(void)
590 {
591     return property_area_inited;
592 }
593 
load_override_properties()594 static void load_override_properties() {
595 #ifdef ALLOW_LOCAL_PROP_OVERRIDE
596     const char *debuggable = property_get("ro.debuggable");
597     if (debuggable && (strcmp(debuggable, "1") == 0)) {
598         load_properties_from_file(PROP_PATH_LOCAL_OVERRIDE);
599     }
600 #endif /* ALLOW_LOCAL_PROP_OVERRIDE */
601 }
602 
603 
604 /* When booting an encrypted system, /data is not mounted when the
605  * property service is started, so any properties stored there are
606  * not loaded.  Vold triggers init to load these properties once it
607  * has mounted /data.
608  */
load_persist_props(void)609 void load_persist_props(void)
610 {
611     load_override_properties();
612     /* Read persistent properties after all default values have been loaded. */
613     load_persistent_properties();
614 }
615 
start_property_service(void)616 void start_property_service(void)
617 {
618     int fd;
619 
620     load_properties_from_file(PROP_PATH_SYSTEM_BUILD);
621     load_properties_from_file(PROP_PATH_SYSTEM_DEFAULT);
622     load_override_properties();
623     /* Read persistent properties after all default values have been loaded. */
624     load_persistent_properties();
625 
626     fd = create_socket(PROP_SERVICE_NAME, SOCK_STREAM, 0666, 0, 0);
627     if(fd < 0) return;
628     fcntl(fd, F_SETFD, FD_CLOEXEC);
629     fcntl(fd, F_SETFL, O_NONBLOCK);
630 
631     listen(fd, 8);
632     property_set_fd = fd;
633 }
634 
get_property_set_fd()635 int get_property_set_fd()
636 {
637     return property_set_fd;
638 }
639