adbd: switch to su domain when running as root

When adbd runs as root, it should transition into the
su domain. This is needed to run the adbd and shell
domains in enforcing on userdebug / eng devices without
breaking developer workflows.

Introduce a new device_banner command line option.

Change-Id: Ib33c0dd2dd6172035230514ac84fcaed2ecf44d6

adb/adb.c

@@ -39,6 +39,8 @@
 #include <sys/capability.h>
 #include <linux/prctl.h>
 #include <sys/mount.h>
+#include <getopt.h>
+#include <selinux/selinux.h>
 #else
 #include "usb_vendors.h"
 #endif
@@ -54,6 +56,7 @@ static int auth_enabled = 0;
 
 #if !ADB_HOST
 static const char *adb_device_banner = "device";
+static const char *root_seclabel = NULL;
 #endif
 
 void fatal(const char *fmt, ...)
@@ -1356,6 +1359,12 @@ int adb_main(int is_daemon, int server_port)
         D("Local port disabled\n");
     } else {
         char local_name[30];
+        if ((root_seclabel != NULL) && (is_selinux_enabled() > 0)) {
+            // b/12587913: fix setcon to allow const pointers
+            if (setcon((char *)root_seclabel) < 0) {
+                exit(1);
+            }
+        }
         build_local_name(local_name, sizeof(local_name), server_port);
         if(install_listener(local_name, "*smartsocket*", NULL, 0)) {
             exit(1);
@@ -1642,10 +1651,6 @@ int handle_host_request(char *service, transport_type ttype, char* serial, int r
     return -1;
 }
 
-#if !ADB_HOST
-int recovery_mode = 0;
-#endif
-
 int main(int argc, char **argv)
 {
 #if ADB_HOST
@@ -1657,9 +1662,26 @@ int main(int argc, char **argv)
     /* If adbd runs inside the emulator this will enable adb tracing via
      * adb-debug qemud service in the emulator. */
     adb_qemu_trace_init();
-    if((argc > 1) && (!strcmp(argv[1],"recovery"))) {
-        adb_device_banner = "recovery";
-        recovery_mode = 1;
+    while(1) {
+        int c;
+        int option_index = 0;
+        static struct option opts[] = {
+            {"root_seclabel", required_argument, 0, 's' },
+            {"device_banner", required_argument, 0, 'b' }
+        };
+        c = getopt_long(argc, argv, "", opts, &option_index);
+        if (c == -1)
+            break;
+        switch (c) {
+        case 's':
+            root_seclabel = optarg;
+            break;
+        case 'b':
+            adb_device_banner = optarg;
+            break;
+        default:
+            break;
+        }
     }
 
     start_device_log();

rootdir/init.rc

@@ -442,7 +442,7 @@ on property:ro.debuggable=1
     start console
 
 # adbd is controlled via property triggers in init.<platform>.usb.rc
-service adbd /sbin/adbd
+service adbd /sbin/adbd --root_seclabel=u:r:su:s0
     class core
     socket adbd stream 660 system system
     disabled