1 /* Copyright 2008 The Android Open Source Project
2 */
3
4 #include <errno.h>
5 #include <fcntl.h>
6 #include <inttypes.h>
7 #include <stdio.h>
8 #include <stdlib.h>
9 #include <string.h>
10
11 #include <cutils/android_filesystem_config.h>
12 #include <cutils/multiuser.h>
13
14 #include <selinux/android.h>
15 #include <selinux/avc.h>
16
17 #include "binder.h"
18
19 #ifdef VENDORSERVICEMANAGER
20 #define LOG_TAG "VendorServiceManager"
21 #else
22 #define LOG_TAG "ServiceManager"
23 #endif
24 #include <log/log.h>
25
26 struct audit_data {
27 pid_t pid;
28 uid_t uid;
29 const char *name;
30 };
31
str8(const uint16_t * x,size_t x_len)32 const char *str8(const uint16_t *x, size_t x_len)
33 {
34 static char buf[128];
35 size_t max = 127;
36 char *p = buf;
37
38 if (x_len < max) {
39 max = x_len;
40 }
41
42 if (x) {
43 while ((max > 0) && (*x != '\0')) {
44 *p++ = *x++;
45 max--;
46 }
47 }
48 *p++ = 0;
49 return buf;
50 }
51
str16eq(const uint16_t * a,const char * b)52 int str16eq(const uint16_t *a, const char *b)
53 {
54 while (*a && *b)
55 if (*a++ != *b++) return 0;
56 if (*a || *b)
57 return 0;
58 return 1;
59 }
60
61 static char *service_manager_context;
62 static struct selabel_handle* sehandle;
63
check_mac_perms(pid_t spid,uid_t uid,const char * tctx,const char * perm,const char * name)64 static bool check_mac_perms(pid_t spid, uid_t uid, const char *tctx, const char *perm, const char *name)
65 {
66 char *sctx = NULL;
67 const char *class = "service_manager";
68 bool allowed;
69 struct audit_data ad;
70
71 if (getpidcon(spid, &sctx) < 0) {
72 ALOGE("SELinux: getpidcon(pid=%d) failed to retrieve pid context.\n", spid);
73 return false;
74 }
75
76 ad.pid = spid;
77 ad.uid = uid;
78 ad.name = name;
79
80 int result = selinux_check_access(sctx, tctx, class, perm, (void *) &ad);
81 allowed = (result == 0);
82
83 freecon(sctx);
84 return allowed;
85 }
86
check_mac_perms_from_getcon(pid_t spid,uid_t uid,const char * perm)87 static bool check_mac_perms_from_getcon(pid_t spid, uid_t uid, const char *perm)
88 {
89 return check_mac_perms(spid, uid, service_manager_context, perm, NULL);
90 }
91
check_mac_perms_from_lookup(pid_t spid,uid_t uid,const char * perm,const char * name)92 static bool check_mac_perms_from_lookup(pid_t spid, uid_t uid, const char *perm, const char *name)
93 {
94 bool allowed;
95 char *tctx = NULL;
96
97 if (!sehandle) {
98 ALOGE("SELinux: Failed to find sehandle. Aborting service_manager.\n");
99 abort();
100 }
101
102 if (selabel_lookup(sehandle, &tctx, name, 0) != 0) {
103 ALOGE("SELinux: No match for %s in service_contexts.\n", name);
104 return false;
105 }
106
107 allowed = check_mac_perms(spid, uid, tctx, perm, name);
108 freecon(tctx);
109 return allowed;
110 }
111
svc_can_register(const uint16_t * name,size_t name_len,pid_t spid,uid_t uid)112 static int svc_can_register(const uint16_t *name, size_t name_len, pid_t spid, uid_t uid)
113 {
114 const char *perm = "add";
115
116 if (multiuser_get_app_id(uid) >= AID_APP) {
117 return 0; /* Don't allow apps to register services */
118 }
119
120 return check_mac_perms_from_lookup(spid, uid, perm, str8(name, name_len)) ? 1 : 0;
121 }
122
svc_can_list(pid_t spid,uid_t uid)123 static int svc_can_list(pid_t spid, uid_t uid)
124 {
125 const char *perm = "list";
126 return check_mac_perms_from_getcon(spid, uid, perm) ? 1 : 0;
127 }
128
svc_can_find(const uint16_t * name,size_t name_len,pid_t spid,uid_t uid)129 static int svc_can_find(const uint16_t *name, size_t name_len, pid_t spid, uid_t uid)
130 {
131 const char *perm = "find";
132 return check_mac_perms_from_lookup(spid, uid, perm, str8(name, name_len)) ? 1 : 0;
133 }
134
135 struct svcinfo
136 {
137 struct svcinfo *next;
138 uint32_t handle;
139 struct binder_death death;
140 int allow_isolated;
141 uint32_t dumpsys_priority;
142 size_t len;
143 uint16_t name[0];
144 };
145
146 struct svcinfo *svclist = NULL;
147
find_svc(const uint16_t * s16,size_t len)148 struct svcinfo *find_svc(const uint16_t *s16, size_t len)
149 {
150 struct svcinfo *si;
151
152 for (si = svclist; si; si = si->next) {
153 if ((len == si->len) &&
154 !memcmp(s16, si->name, len * sizeof(uint16_t))) {
155 return si;
156 }
157 }
158 return NULL;
159 }
160
svcinfo_death(struct binder_state * bs,void * ptr)161 void svcinfo_death(struct binder_state *bs, void *ptr)
162 {
163 struct svcinfo *si = (struct svcinfo* ) ptr;
164
165 ALOGI("service '%s' died\n", str8(si->name, si->len));
166 if (si->handle) {
167 binder_release(bs, si->handle);
168 si->handle = 0;
169 }
170 }
171
172 uint16_t svcmgr_id[] = {
173 'a','n','d','r','o','i','d','.','o','s','.',
174 'I','S','e','r','v','i','c','e','M','a','n','a','g','e','r'
175 };
176
177
do_find_service(const uint16_t * s,size_t len,uid_t uid,pid_t spid)178 uint32_t do_find_service(const uint16_t *s, size_t len, uid_t uid, pid_t spid)
179 {
180 struct svcinfo *si = find_svc(s, len);
181
182 if (!si || !si->handle) {
183 return 0;
184 }
185
186 if (!si->allow_isolated) {
187 // If this service doesn't allow access from isolated processes,
188 // then check the uid to see if it is isolated.
189 uid_t appid = uid % AID_USER;
190 if (appid >= AID_ISOLATED_START && appid <= AID_ISOLATED_END) {
191 return 0;
192 }
193 }
194
195 if (!svc_can_find(s, len, spid, uid)) {
196 return 0;
197 }
198
199 return si->handle;
200 }
201
do_add_service(struct binder_state * bs,const uint16_t * s,size_t len,uint32_t handle,uid_t uid,int allow_isolated,uint32_t dumpsys_priority,pid_t spid)202 int do_add_service(struct binder_state *bs, const uint16_t *s, size_t len, uint32_t handle,
203 uid_t uid, int allow_isolated, uint32_t dumpsys_priority, pid_t spid) {
204 struct svcinfo *si;
205
206 //ALOGI("add_service('%s',%x,%s) uid=%d\n", str8(s, len), handle,
207 // allow_isolated ? "allow_isolated" : "!allow_isolated", uid);
208
209 if (!handle || (len == 0) || (len > 127))
210 return -1;
211
212 if (!svc_can_register(s, len, spid, uid)) {
213 ALOGE("add_service('%s',%x) uid=%d - PERMISSION DENIED\n",
214 str8(s, len), handle, uid);
215 return -1;
216 }
217
218 si = find_svc(s, len);
219 if (si) {
220 if (si->handle) {
221 ALOGE("add_service('%s',%x) uid=%d - ALREADY REGISTERED, OVERRIDE\n",
222 str8(s, len), handle, uid);
223 svcinfo_death(bs, si);
224 }
225 si->handle = handle;
226 } else {
227 si = malloc(sizeof(*si) + (len + 1) * sizeof(uint16_t));
228 if (!si) {
229 ALOGE("add_service('%s',%x) uid=%d - OUT OF MEMORY\n",
230 str8(s, len), handle, uid);
231 return -1;
232 }
233 si->handle = handle;
234 si->len = len;
235 memcpy(si->name, s, (len + 1) * sizeof(uint16_t));
236 si->name[len] = '\0';
237 si->death.func = (void*) svcinfo_death;
238 si->death.ptr = si;
239 si->allow_isolated = allow_isolated;
240 si->dumpsys_priority = dumpsys_priority;
241 si->next = svclist;
242 svclist = si;
243 }
244
245 binder_acquire(bs, handle);
246 binder_link_to_death(bs, handle, &si->death);
247 return 0;
248 }
249
svcmgr_handler(struct binder_state * bs,struct binder_transaction_data * txn,struct binder_io * msg,struct binder_io * reply)250 int svcmgr_handler(struct binder_state *bs,
251 struct binder_transaction_data *txn,
252 struct binder_io *msg,
253 struct binder_io *reply)
254 {
255 struct svcinfo *si;
256 uint16_t *s;
257 size_t len;
258 uint32_t handle;
259 uint32_t strict_policy;
260 int allow_isolated;
261 uint32_t dumpsys_priority;
262
263 //ALOGI("target=%p code=%d pid=%d uid=%d\n",
264 // (void*) txn->target.ptr, txn->code, txn->sender_pid, txn->sender_euid);
265
266 if (txn->target.ptr != BINDER_SERVICE_MANAGER)
267 return -1;
268
269 if (txn->code == PING_TRANSACTION)
270 return 0;
271
272 // Equivalent to Parcel::enforceInterface(), reading the RPC
273 // header with the strict mode policy mask and the interface name.
274 // Note that we ignore the strict_policy and don't propagate it
275 // further (since we do no outbound RPCs anyway).
276 strict_policy = bio_get_uint32(msg);
277 s = bio_get_string16(msg, &len);
278 if (s == NULL) {
279 return -1;
280 }
281
282 if ((len != (sizeof(svcmgr_id) / 2)) ||
283 memcmp(svcmgr_id, s, sizeof(svcmgr_id))) {
284 fprintf(stderr,"invalid id %s\n", str8(s, len));
285 return -1;
286 }
287
288 if (sehandle && selinux_status_updated() > 0) {
289 #ifdef VENDORSERVICEMANAGER
290 struct selabel_handle *tmp_sehandle = selinux_android_vendor_service_context_handle();
291 #else
292 struct selabel_handle *tmp_sehandle = selinux_android_service_context_handle();
293 #endif
294 if (tmp_sehandle) {
295 selabel_close(sehandle);
296 sehandle = tmp_sehandle;
297 }
298 }
299
300 switch(txn->code) {
301 case SVC_MGR_GET_SERVICE:
302 case SVC_MGR_CHECK_SERVICE:
303 s = bio_get_string16(msg, &len);
304 if (s == NULL) {
305 return -1;
306 }
307 handle = do_find_service(s, len, txn->sender_euid, txn->sender_pid);
308 if (!handle)
309 break;
310 bio_put_ref(reply, handle);
311 return 0;
312
313 case SVC_MGR_ADD_SERVICE:
314 s = bio_get_string16(msg, &len);
315 if (s == NULL) {
316 return -1;
317 }
318 handle = bio_get_ref(msg);
319 allow_isolated = bio_get_uint32(msg) ? 1 : 0;
320 dumpsys_priority = bio_get_uint32(msg);
321 if (do_add_service(bs, s, len, handle, txn->sender_euid, allow_isolated, dumpsys_priority,
322 txn->sender_pid))
323 return -1;
324 break;
325
326 case SVC_MGR_LIST_SERVICES: {
327 uint32_t n = bio_get_uint32(msg);
328 uint32_t req_dumpsys_priority = bio_get_uint32(msg);
329
330 if (!svc_can_list(txn->sender_pid, txn->sender_euid)) {
331 ALOGE("list_service() uid=%d - PERMISSION DENIED\n",
332 txn->sender_euid);
333 return -1;
334 }
335 si = svclist;
336 // walk through the list of services n times skipping services that
337 // do not support the requested priority
338 while (si) {
339 if (si->dumpsys_priority & req_dumpsys_priority) {
340 if (n == 0) break;
341 n--;
342 }
343 si = si->next;
344 }
345 if (si) {
346 bio_put_string16(reply, si->name);
347 return 0;
348 }
349 return -1;
350 }
351 default:
352 ALOGE("unknown code %d\n", txn->code);
353 return -1;
354 }
355
356 bio_put_uint32(reply, 0);
357 return 0;
358 }
359
360
audit_callback(void * data,__unused security_class_t cls,char * buf,size_t len)361 static int audit_callback(void *data, __unused security_class_t cls, char *buf, size_t len)
362 {
363 struct audit_data *ad = (struct audit_data *)data;
364
365 if (!ad || !ad->name) {
366 ALOGE("No service manager audit data");
367 return 0;
368 }
369
370 snprintf(buf, len, "service=%s pid=%d uid=%d", ad->name, ad->pid, ad->uid);
371 return 0;
372 }
373
main(int argc,char ** argv)374 int main(int argc, char** argv)
375 {
376 struct binder_state *bs;
377 union selinux_callback cb;
378 char *driver;
379
380 if (argc > 1) {
381 driver = argv[1];
382 } else {
383 driver = "/dev/binder";
384 }
385
386 bs = binder_open(driver, 128*1024);
387 if (!bs) {
388 #ifdef VENDORSERVICEMANAGER
389 ALOGW("failed to open binder driver %s\n", driver);
390 while (true) {
391 sleep(UINT_MAX);
392 }
393 #else
394 ALOGE("failed to open binder driver %s\n", driver);
395 #endif
396 return -1;
397 }
398
399 if (binder_become_context_manager(bs)) {
400 ALOGE("cannot become context manager (%s)\n", strerror(errno));
401 return -1;
402 }
403
404 cb.func_audit = audit_callback;
405 selinux_set_callback(SELINUX_CB_AUDIT, cb);
406 cb.func_log = selinux_log_callback;
407 selinux_set_callback(SELINUX_CB_LOG, cb);
408
409 #ifdef VENDORSERVICEMANAGER
410 sehandle = selinux_android_vendor_service_context_handle();
411 #else
412 sehandle = selinux_android_service_context_handle();
413 #endif
414 selinux_status_open(true);
415
416 if (sehandle == NULL) {
417 ALOGE("SELinux: Failed to acquire sehandle. Aborting.\n");
418 abort();
419 }
420
421 if (getcon(&service_manager_context) != 0) {
422 ALOGE("SELinux: Failed to acquire service_manager context. Aborting.\n");
423 abort();
424 }
425
426
427 binder_loop(bs, svcmgr_handler);
428
429 return 0;
430 }
431