adb daemon: Don't drop privileges

Running adbd as root via the 'adb root' command causes
adbd to stop and not respawn, so avoid dropping
privileges altogether in favor of running as root.

Author: fredldotme

adb/daemon/main.cpp

@@ -43,122 +43,6 @@
 
 static const char* root_seclabel = nullptr;
 
-static void drop_capabilities_bounding_set_if_needed() {
-#ifdef ALLOW_ADBD_ROOT
-    char value[PROPERTY_VALUE_MAX];
-    property_get("ro.debuggable", value, "");
-    if (strcmp(value, "1") == 0) {
-        return;
-    }
-#endif
-    for (int i = 0; prctl(PR_CAPBSET_READ, i, 0, 0, 0) >= 0; i++) {
-        if (i == CAP_SETUID || i == CAP_SETGID) {
-            // CAP_SETUID CAP_SETGID needed by /system/bin/run-as
-            continue;
-        }
-
-        if (prctl(PR_CAPBSET_DROP, i, 0, 0, 0) == -1) {
-            PLOG(FATAL) << "Could not drop capabilities";
-        }
-    }
-}
-
-static bool should_drop_privileges() {
-#if defined(ALLOW_ADBD_ROOT)
-    char value[PROPERTY_VALUE_MAX];
-
-    // The properties that affect `adb root` and `adb unroot` are ro.secure and
-    // ro.debuggable. In this context the names don't make the expected behavior
-    // particularly obvious.
-    //
-    // ro.debuggable:
-    //   Allowed to become root, but not necessarily the default. Set to 1 on
-    //   eng and userdebug builds.
-    //
-    // ro.secure:
-    //   Drop privileges by default. Set to 1 on userdebug and user builds.
-    property_get("ro.secure", value, "1");
-    bool ro_secure = (strcmp(value, "1") == 0);
-
-    property_get("ro.debuggable", value, "");
-    bool ro_debuggable = (strcmp(value, "1") == 0);
-
-    // Drop privileges if ro.secure is set...
-    bool drop = ro_secure;
-
-    property_get("service.adb.root", value, "");
-    bool adb_root = (strcmp(value, "1") == 0);
-    bool adb_unroot = (strcmp(value, "0") == 0);
-
-    // ... except "adb root" lets you keep privileges in a debuggable build.
-    if (ro_debuggable && adb_root) {
-        drop = false;
-    }
-
-    // ... and "adb unroot" lets you explicitly drop privileges.
-    if (adb_unroot) {
-        drop = true;
-    }
-
-    return drop;
-#else
-    return true; // "adb root" not allowed, always drop privileges.
-#endif // ALLOW_ADBD_ROOT
-}
-
-static void drop_privileges(int server_port) {
-    std::unique_ptr<minijail, void (*)(minijail*)> jail(minijail_new(),
-                                                        &minijail_destroy);
-
-    // Add extra groups:
-    // AID_ADB to access the USB driver
-    // AID_LOG to read system logs (adb logcat)
-    // AID_INPUT to diagnose input issues (getevent)
-    // AID_INET to diagnose network issues (ping)
-    // AID_NET_BT and AID_NET_BT_ADMIN to diagnose bluetooth (hcidump)
-    // AID_SDCARD_R to allow reading from the SD card
-    // AID_SDCARD_RW to allow writing to the SD card
-    // AID_NET_BW_STATS to read out qtaguid statistics
-    // AID_READPROC for reading /proc entries across UID boundaries
-    gid_t groups[] = {AID_ADB,      AID_LOG,       AID_INPUT,
-                      AID_INET,     AID_NET_BT,    AID_NET_BT_ADMIN,
-                      AID_SDCARD_R, AID_SDCARD_RW, AID_NET_BW_STATS,
-                      AID_READPROC};
-    minijail_set_supplementary_gids(jail.get(),
-                                    sizeof(groups) / sizeof(groups[0]),
-                                    groups);
-
-    // Don't listen on a port (default 5037) if running in secure mode.
-    // Don't run as root if running in secure mode.
-    if (should_drop_privileges()) {
-        drop_capabilities_bounding_set_if_needed();
-
-        minijail_change_gid(jail.get(), AID_SHELL);
-        minijail_change_uid(jail.get(), AID_SHELL);
-        // minijail_enter() will abort if any priv-dropping step fails.
-        minijail_enter(jail.get());
-
-        D("Local port disabled");
-    } else {
-        // minijail_enter() will abort if any priv-dropping step fails.
-        minijail_enter(jail.get());
-
-        if (root_seclabel != nullptr) {
-            if (selinux_android_setcon(root_seclabel) < 0) {
-                LOG(FATAL) << "Could not set SELinux context";
-            }
-        }
-        std::string error;
-        std::string local_name =
-            android::base::StringPrintf("tcp:%d", server_port);
-        if (install_listener(local_name, "*smartsocket*", nullptr, 0,
-                             &error)) {
-            LOG(FATAL) << "Could not install *smartsocket* listener: "
-                       << error;
-        }
-    }
-}
-
 int adbd_main(int server_port) {
     umask(0);
 
@@ -186,8 +70,6 @@ int adbd_main(int server_port) {
           " unchanged.\n");
     }
 
-    drop_privileges(server_port);
-
     bool is_usb = false;
     if (access(USB_ADB_PATH, F_OK) == 0 || access(USB_FFS_ADB_EP0, F_OK) == 0) {
         // Listen on USB.