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