Add MAC for remaining service_manager functionality.

Add SELinux MAC for the list and find functionality
to service_manager. By default the list action uses
the service_manager_type attribute as its target
object.

Change-Id: I7630f21a9f3232ae3d6d8b9a1119230b40899aef

cmds/servicemanager/service_manager.c

@@ -52,46 +52,18 @@ int str16eq(const uint16_t *a, const char *b)
     return 1;
 }
 
+static int selinux_enabled;
+static char *service_manager_context;
 static struct selabel_handle* sehandle;
 
-static bool check_mac_perms(const char *name, pid_t spid)
+static bool check_mac_perms(pid_t spid, const char *tctx, const char *perm, const char *name)
 {
-    if (is_selinux_enabled() <= 0) {
-        return true;
-    }
-
-    bool allowed = false;
-
-    const char *class = "service_manager";
-    const char *perm = "add";
-
-    char *tctx = NULL;
     char *sctx = NULL;
-
-    if (!sehandle) {
-        ALOGE("SELinux: Failed to find sehandle %s.\n", name);
-        return false;
-    }
+    const char *class = "service_manager";
+    bool allowed;
 
     if (getpidcon(spid, &sctx) < 0) {
-        ALOGE("SELinux: getpidcon failed to retrieve pid context.\n");
-        return false;
-    }
-
-    if (!sctx) {
-        ALOGE("SELinux: Failed to find sctx for %s.\n", name);
-        return false;
-    }
-
-    if (selabel_lookup(sehandle, &tctx, name, 1) != 0) {
-        ALOGE("SELinux: selabel_lookup failed to set tctx for %s.\n", name);
-        freecon(sctx);
-        return false;
-    }
-
-    if (!tctx) {
-        ALOGE("SELinux: Failed to find tctx for %s.\n", name);
-        freecon(sctx);
+        ALOGE("SELinux: getpidcon(pid=%d) failed to retrieve pid context.\n", spid);
         return false;
     }
 
@@ -99,13 +71,58 @@ static bool check_mac_perms(const char *name, pid_t spid)
     allowed = (result == 0);
 
     freecon(sctx);
+    return allowed;
+}
+
+static bool check_mac_perms_from_getcon(pid_t spid, const char *perm)
+{
+    if (selinux_enabled <= 0) {
+        return true;
+    }
+
+    return check_mac_perms(spid, service_manager_context, perm, NULL);
+}
+
+static bool check_mac_perms_from_lookup(pid_t spid, const char *perm, const char *name)
+{
+    bool allowed;
+    char *tctx = NULL;
+
+    if (selinux_enabled <= 0) {
+        return true;
+    }
+
+    if (!sehandle) {
+        ALOGE("SELinux: Failed to find sehandle. Aborting service_manager.\n");
+        abort();
+    }
+
+    if (selabel_lookup(sehandle, &tctx, name, 0) != 0) {
+        ALOGE("SELinux: No match for %s in service_contexts.\n", name);
+        return false;
+    }
+
+    allowed = check_mac_perms(spid, tctx, perm, name);
     freecon(tctx);
     return allowed;
 }
 
-static int svc_can_register(uid_t uid, const uint16_t *name, size_t name_len, pid_t spid)
+static int svc_can_register(const uint16_t *name, size_t name_len, pid_t spid)
 {
-    return check_mac_perms(str8(name, name_len), spid) ? 1 : 0;
+    const char *perm = "add";
+    return check_mac_perms_from_lookup(spid, perm, str8(name, name_len)) ? 1 : 0;
+}
+
+static int svc_can_list(pid_t spid)
+{
+    const char *perm = "list";
+    return check_mac_perms_from_getcon(spid, perm) ? 1 : 0;
+}
+
+static int svc_can_find(const uint16_t *name, size_t name_len, pid_t spid)
+{
+    const char *perm = "find";
+    return check_mac_perms_from_lookup(spid, perm, str8(name, name_len)) ? 1 : 0;
 }
 
 struct svcinfo
@@ -150,10 +167,15 @@ uint16_t svcmgr_id[] = {
 };
 
 
-uint32_t do_find_service(struct binder_state *bs, const uint16_t *s, size_t len, uid_t uid)
+uint32_t do_find_service(struct binder_state *bs, const uint16_t *s, size_t len, uid_t uid, pid_t spid)
 {
     struct svcinfo *si;
 
+    if (!svc_can_find(s, len, spid)) {
+        ALOGE("find_service('%s') uid=%d - PERMISSION DENIED\n",
+             str8(s, len), uid);
+        return 0;
+    }
     si = find_svc(s, len);
     //ALOGI("check_service('%s') handle = %x\n", str8(s, len), si ? si->handle : 0);
     if (si && si->handle) {
@@ -184,7 +206,7 @@ int do_add_service(struct binder_state *bs,
     if (!handle || (len == 0) || (len > 127))
         return -1;
 
-    if (!svc_can_register(uid, s, len, spid)) {
+    if (!svc_can_register(s, len, spid)) {
         ALOGE("add_service('%s',%x) uid=%d - PERMISSION DENIED\n",
              str8(s, len), handle, uid);
         return -1;
@@ -273,7 +295,7 @@ int svcmgr_handler(struct binder_state *bs,
         if (s == NULL) {
             return -1;
         }
-        handle = do_find_service(bs, s, len, txn->sender_euid);
+        handle = do_find_service(bs, s, len, txn->sender_euid, txn->sender_pid);
         if (!handle)
             break;
         bio_put_ref(reply, handle);
@@ -294,6 +316,11 @@ int svcmgr_handler(struct binder_state *bs,
     case SVC_MGR_LIST_SERVICES: {
         uint32_t n = bio_get_uint32(msg);
 
+        if (!svc_can_list(txn->sender_pid)) {
+            ALOGE("list_service() uid=%d - PERMISSION DENIED\n",
+                    txn->sender_euid);
+            return -1;
+        }
         si = svclist;
         while ((n-- > 0) && si)
             si = si->next;
@@ -334,8 +361,21 @@ int main(int argc, char **argv)
         return -1;
     }
 
+    selinux_enabled = is_selinux_enabled();
     sehandle = selinux_android_service_context_handle();
 
+    if (selinux_enabled > 0) {
+        if (sehandle == NULL) {
+            ALOGE("SELinux: Failed to acquire sehandle. Aborting.\n");
+            abort();
+        }
+
+        if (getcon(&service_manager_context) != 0) {
+            ALOGE("SELinux: Failed to acquire service_manager context. Aborting.\n");
+            abort();
+        }
+    }
+
     union selinux_callback cb;
     cb.func_audit = audit_callback;
     selinux_set_callback(SELINUX_CB_AUDIT, cb);