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
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 int selinux_enabled;
62 static char *service_manager_context;
63 static struct selabel_handle* sehandle;
64
check_mac_perms(pid_t spid,uid_t uid,const char * tctx,const char * perm,const char * name)65 static bool check_mac_perms(pid_t spid, uid_t uid, const char *tctx, const char *perm, const char *name)
66 {
67 char *sctx = NULL;
68 const char *class = "service_manager";
69 bool allowed;
70 struct audit_data ad;
71
72 if (getpidcon(spid, &sctx) < 0) {
73 ALOGE("SELinux: getpidcon(pid=%d) failed to retrieve pid context.\n", spid);
74 return false;
75 }
76
77 ad.pid = spid;
78 ad.uid = uid;
79 ad.name = name;
80
81 int result = selinux_check_access(sctx, tctx, class, perm, (void *) &ad);
82 allowed = (result == 0);
83
84 freecon(sctx);
85 return allowed;
86 }
87
check_mac_perms_from_getcon(pid_t spid,uid_t uid,const char * perm)88 static bool check_mac_perms_from_getcon(pid_t spid, uid_t uid, const char *perm)
89 {
90 if (selinux_enabled <= 0) {
91 return true;
92 }
93
94 return check_mac_perms(spid, uid, service_manager_context, perm, NULL);
95 }
96
check_mac_perms_from_lookup(pid_t spid,uid_t uid,const char * perm,const char * name)97 static bool check_mac_perms_from_lookup(pid_t spid, uid_t uid, const char *perm, const char *name)
98 {
99 bool allowed;
100 char *tctx = NULL;
101
102 if (selinux_enabled <= 0) {
103 return true;
104 }
105
106 if (!sehandle) {
107 ALOGE("SELinux: Failed to find sehandle. Aborting service_manager.\n");
108 abort();
109 }
110
111 if (selabel_lookup(sehandle, &tctx, name, 0) != 0) {
112 ALOGE("SELinux: No match for %s in service_contexts.\n", name);
113 return false;
114 }
115
116 allowed = check_mac_perms(spid, uid, tctx, perm, name);
117 freecon(tctx);
118 return allowed;
119 }
120
svc_can_register(const uint16_t * name,size_t name_len,pid_t spid,uid_t uid)121 static int svc_can_register(const uint16_t *name, size_t name_len, pid_t spid, uid_t uid)
122 {
123 const char *perm = "add";
124 return check_mac_perms_from_lookup(spid, uid, perm, str8(name, name_len)) ? 1 : 0;
125 }
126
svc_can_list(pid_t spid,uid_t uid)127 static int svc_can_list(pid_t spid, uid_t uid)
128 {
129 const char *perm = "list";
130 return check_mac_perms_from_getcon(spid, uid, perm) ? 1 : 0;
131 }
132
svc_can_find(const uint16_t * name,size_t name_len,pid_t spid,uid_t uid)133 static int svc_can_find(const uint16_t *name, size_t name_len, pid_t spid, uid_t uid)
134 {
135 const char *perm = "find";
136 return check_mac_perms_from_lookup(spid, uid, perm, str8(name, name_len)) ? 1 : 0;
137 }
138
139 struct svcinfo
140 {
141 struct svcinfo *next;
142 uint32_t handle;
143 struct binder_death death;
144 int allow_isolated;
145 size_t len;
146 uint16_t name[0];
147 };
148
149 struct svcinfo *svclist = NULL;
150
find_svc(const uint16_t * s16,size_t len)151 struct svcinfo *find_svc(const uint16_t *s16, size_t len)
152 {
153 struct svcinfo *si;
154
155 for (si = svclist; si; si = si->next) {
156 if ((len == si->len) &&
157 !memcmp(s16, si->name, len * sizeof(uint16_t))) {
158 return si;
159 }
160 }
161 return NULL;
162 }
163
svcinfo_death(struct binder_state * bs,void * ptr)164 void svcinfo_death(struct binder_state *bs, void *ptr)
165 {
166 struct svcinfo *si = (struct svcinfo* ) ptr;
167
168 ALOGI("service '%s' died\n", str8(si->name, si->len));
169 if (si->handle) {
170 binder_release(bs, si->handle);
171 si->handle = 0;
172 }
173 }
174
175 uint16_t svcmgr_id[] = {
176 'a','n','d','r','o','i','d','.','o','s','.',
177 'I','S','e','r','v','i','c','e','M','a','n','a','g','e','r'
178 };
179
180
do_find_service(const uint16_t * s,size_t len,uid_t uid,pid_t spid)181 uint32_t do_find_service(const uint16_t *s, size_t len, uid_t uid, pid_t spid)
182 {
183 struct svcinfo *si = find_svc(s, len);
184
185 if (!si || !si->handle) {
186 return 0;
187 }
188
189 if (!si->allow_isolated) {
190 // If this service doesn't allow access from isolated processes,
191 // then check the uid to see if it is isolated.
192 uid_t appid = uid % AID_USER;
193 if (appid >= AID_ISOLATED_START && appid <= AID_ISOLATED_END) {
194 return 0;
195 }
196 }
197
198 if (!svc_can_find(s, len, spid, uid)) {
199 return 0;
200 }
201
202 return si->handle;
203 }
204
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)205 int do_add_service(struct binder_state *bs,
206 const uint16_t *s, size_t len,
207 uint32_t handle, uid_t uid, int allow_isolated,
208 pid_t spid)
209 {
210 struct svcinfo *si;
211
212 //ALOGI("add_service('%s',%x,%s) uid=%d\n", str8(s, len), handle,
213 // allow_isolated ? "allow_isolated" : "!allow_isolated", uid);
214
215 if (!handle || (len == 0) || (len > 127))
216 return -1;
217
218 if (!svc_can_register(s, len, spid, uid)) {
219 ALOGE("add_service('%s',%x) uid=%d - PERMISSION DENIED\n",
220 str8(s, len), handle, uid);
221 return -1;
222 }
223
224 si = find_svc(s, len);
225 if (si) {
226 if (si->handle) {
227 ALOGE("add_service('%s',%x) uid=%d - ALREADY REGISTERED, OVERRIDE\n",
228 str8(s, len), handle, uid);
229 svcinfo_death(bs, si);
230 }
231 si->handle = handle;
232 } else {
233 si = malloc(sizeof(*si) + (len + 1) * sizeof(uint16_t));
234 if (!si) {
235 ALOGE("add_service('%s',%x) uid=%d - OUT OF MEMORY\n",
236 str8(s, len), handle, uid);
237 return -1;
238 }
239 si->handle = handle;
240 si->len = len;
241 memcpy(si->name, s, (len + 1) * sizeof(uint16_t));
242 si->name[len] = '\0';
243 si->death.func = (void*) svcinfo_death;
244 si->death.ptr = si;
245 si->allow_isolated = allow_isolated;
246 si->next = svclist;
247 svclist = si;
248 }
249
250 binder_acquire(bs, handle);
251 binder_link_to_death(bs, handle, &si->death);
252 return 0;
253 }
254
svcmgr_handler(struct binder_state * bs,struct binder_transaction_data * txn,struct binder_io * msg,struct binder_io * reply)255 int svcmgr_handler(struct binder_state *bs,
256 struct binder_transaction_data *txn,
257 struct binder_io *msg,
258 struct binder_io *reply)
259 {
260 struct svcinfo *si;
261 uint16_t *s;
262 size_t len;
263 uint32_t handle;
264 uint32_t strict_policy;
265 int allow_isolated;
266
267 //ALOGI("target=%p code=%d pid=%d uid=%d\n",
268 // (void*) txn->target.ptr, txn->code, txn->sender_pid, txn->sender_euid);
269
270 if (txn->target.ptr != BINDER_SERVICE_MANAGER)
271 return -1;
272
273 if (txn->code == PING_TRANSACTION)
274 return 0;
275
276 // Equivalent to Parcel::enforceInterface(), reading the RPC
277 // header with the strict mode policy mask and the interface name.
278 // Note that we ignore the strict_policy and don't propagate it
279 // further (since we do no outbound RPCs anyway).
280 strict_policy = bio_get_uint32(msg);
281 s = bio_get_string16(msg, &len);
282 if (s == NULL) {
283 return -1;
284 }
285
286 if ((len != (sizeof(svcmgr_id) / 2)) ||
287 memcmp(svcmgr_id, s, sizeof(svcmgr_id))) {
288 fprintf(stderr,"invalid id %s\n", str8(s, len));
289 return -1;
290 }
291
292 if (sehandle && selinux_status_updated() > 0) {
293 struct selabel_handle *tmp_sehandle = selinux_android_service_context_handle();
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 if (do_add_service(bs, s, len, handle, txn->sender_euid,
321 allow_isolated, txn->sender_pid))
322 return -1;
323 break;
324
325 case SVC_MGR_LIST_SERVICES: {
326 uint32_t n = bio_get_uint32(msg);
327
328 if (!svc_can_list(txn->sender_pid, txn->sender_euid)) {
329 ALOGE("list_service() uid=%d - PERMISSION DENIED\n",
330 txn->sender_euid);
331 return -1;
332 }
333 si = svclist;
334 while ((n-- > 0) && si)
335 si = si->next;
336 if (si) {
337 bio_put_string16(reply, si->name);
338 return 0;
339 }
340 return -1;
341 }
342 default:
343 ALOGE("unknown code %d\n", txn->code);
344 return -1;
345 }
346
347 bio_put_uint32(reply, 0);
348 return 0;
349 }
350
351
audit_callback(void * data,__unused security_class_t cls,char * buf,size_t len)352 static int audit_callback(void *data, __unused security_class_t cls, char *buf, size_t len)
353 {
354 struct audit_data *ad = (struct audit_data *)data;
355
356 if (!ad || !ad->name) {
357 ALOGE("No service manager audit data");
358 return 0;
359 }
360
361 snprintf(buf, len, "service=%s pid=%d uid=%d", ad->name, ad->pid, ad->uid);
362 return 0;
363 }
364
main()365 int main()
366 {
367 struct binder_state *bs;
368
369 bs = binder_open(128*1024);
370 if (!bs) {
371 ALOGE("failed to open binder driver\n");
372 return -1;
373 }
374
375 if (binder_become_context_manager(bs)) {
376 ALOGE("cannot become context manager (%s)\n", strerror(errno));
377 return -1;
378 }
379
380 selinux_enabled = is_selinux_enabled();
381 sehandle = selinux_android_service_context_handle();
382 selinux_status_open(true);
383
384 if (selinux_enabled > 0) {
385 if (sehandle == NULL) {
386 ALOGE("SELinux: Failed to acquire sehandle. Aborting.\n");
387 abort();
388 }
389
390 if (getcon(&service_manager_context) != 0) {
391 ALOGE("SELinux: Failed to acquire service_manager context. Aborting.\n");
392 abort();
393 }
394 }
395
396 union selinux_callback cb;
397 cb.func_audit = audit_callback;
398 selinux_set_callback(SELINUX_CB_AUDIT, cb);
399 cb.func_log = selinux_log_callback;
400 selinux_set_callback(SELINUX_CB_LOG, cb);
401
402 binder_loop(bs, svcmgr_handler);
403
404 return 0;
405 }
406