Credential FRP: keep gatekeeperd credentials after reset

Gatekeeperd now delays clearing all user credentials
until the device setup is complete or we enroll a new
credential (whichever comes first).

Bug: 36814845
Test: Set lockscreen credential, "adb reboot-bootloader && fastboot -w", "adb shell am start -a android.app.action.CONFIRM_FRP_CREDENTIAL", verify that credential still works
Change-Id: If2ad78ff5b80a6ddffd997be0949b03ed11797f4

gatekeeperd/IGateKeeperService.cpp

@@ -158,6 +158,12 @@ status_t BnGateKeeperService::onTransact(
             reply->writeNoException();
             return NO_ERROR;
         }
+        case REPORT_DEVICE_SETUP_COMPLETE: {
+            CHECK_INTERFACE(IGateKeeperService, data, reply);
+            reportDeviceSetupComplete();
+            reply->writeNoException();
+            return NO_ERROR;
+        }
         default:
             return BBinder::onTransact(code, data, reply, flags);
     }

gatekeeperd/IGateKeeperService.h

@@ -33,6 +33,7 @@ public:
         VERIFY_CHALLENGE = IBinder::FIRST_CALL_TRANSACTION + 2,
         GET_SECURE_USER_ID = IBinder::FIRST_CALL_TRANSACTION + 3,
         CLEAR_SECURE_USER_ID = IBinder::FIRST_CALL_TRANSACTION + 4,
+        REPORT_DEVICE_SETUP_COMPLETE = IBinder::FIRST_CALL_TRANSACTION + 5,
     };
 
     enum {
@@ -95,6 +96,12 @@ public:
      * Clears the secure user ID associated with the user.
      */
     virtual void clearSecureUserId(uint32_t uid) = 0;
+
+    /**
+     * Notifies gatekeeper that device setup has been completed and any potentially still existing
+     * state from before a factory reset can be cleaned up (if it has not been already).
+     */
+    virtual void reportDeviceSetupComplete() = 0;
 };
 
 // ----------------------------------------------------------------------------

gatekeeperd/gatekeeperd.cpp

@@ -56,19 +56,13 @@ static const String16 DUMP_PERMISSION("android.permission.DUMP");
 class GateKeeperProxy : public BnGateKeeperService {
 public:
     GateKeeperProxy() {
+        clear_state_if_needed_done = false;
         hw_device = IGatekeeper::getService();
 
         if (hw_device == nullptr) {
             ALOGW("falling back to software GateKeeper");
             soft_device.reset(new SoftGateKeeperDevice());
         }
-
-        if (mark_cold_boot()) {
-            ALOGI("cold boot: clearing state");
-            if (hw_device != nullptr) {
-                hw_device->deleteAllUsers([](const GatekeeperResponse &){});
-            }
-        }
     }
 
     virtual ~GateKeeperProxy() {
@@ -86,6 +80,21 @@ public:
         close(fd);
     }
 
+    void clear_state_if_needed() {
+        if (clear_state_if_needed_done) {
+            return;
+        }
+
+        if (mark_cold_boot()) {
+            ALOGI("cold boot: clearing state");
+            if (hw_device != nullptr) {
+                hw_device->deleteAllUsers([](const GatekeeperResponse &){});
+            }
+        }
+
+        clear_state_if_needed_done = true;
+    }
+
     bool mark_cold_boot() {
         const char *filename = ".coldboot";
         if (access(filename, F_OK) == -1) {
@@ -140,6 +149,10 @@ public:
             return PERMISSION_DENIED;
         }
 
+        // Make sure to clear any state from before factory reset as soon as a credential is
+        // enrolled (which may happen during device setup).
+        clear_state_if_needed();
+
         // need a desired password to enroll
         if (desired_password_length == 0) return -EINVAL;
 
@@ -354,6 +367,18 @@ public:
         }
     }
 
+    virtual void reportDeviceSetupComplete() {
+        IPCThreadState* ipc = IPCThreadState::self();
+        const int calling_pid = ipc->getCallingPid();
+        const int calling_uid = ipc->getCallingUid();
+        if (!PermissionCache::checkPermission(KEYGUARD_PERMISSION, calling_pid, calling_uid)) {
+            ALOGE("%s: permission denied for [%d:%d]", __func__, calling_pid, calling_uid);
+            return;
+        }
+
+        clear_state_if_needed();
+    }
+
     virtual status_t dump(int fd, const Vector<String16> &) {
         IPCThreadState* ipc = IPCThreadState::self();
         const int pid = ipc->getCallingPid();
@@ -376,6 +401,8 @@ public:
 private:
     sp<IGatekeeper> hw_device;
     UniquePtr<SoftGateKeeperDevice> soft_device;
+
+    bool clear_state_if_needed_done;
 };
 }// namespace android