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