V2: Use resolution to round sensor event values
Add method to utilize a sensor's specified resolution value to ensure
data isn't provided that is more fine-grained than expected. This
helps mitigate sensor calibration fingerprinting attacks.
Bug: 147725937
Test: Verify accel sensor data isn't more fine grained than its
specified resolution
Test: Verify that the max range specified is a multiple of the
resolution
Change-Id: I30ff66d9deb10c84319a63f9964477d8e469650d
diff --git a/services/sensorservice/SensorDeviceUtils.h b/services/sensorservice/SensorDeviceUtils.h
index e2eb606..d7e621c 100644
--- a/services/sensorservice/SensorDeviceUtils.h
+++ b/services/sensorservice/SensorDeviceUtils.h
@@ -18,7 +18,9 @@
#define ANDROID_SENSOR_DEVICE_UTIL
#include <android/hidl/manager/1.0/IServiceNotification.h>
+#include <hardware/sensors.h>
+#include <cmath>
#include <condition_variable>
#include <thread>
@@ -29,6 +31,21 @@
namespace android {
namespace SensorDeviceUtils {
+// Quantizes a single value using a sensor's resolution.
+inline void quantizeValue(float *value, double resolution) {
+ // Increase the value of the sensor's nominal resolution to ensure that
+ // sensor accuracy improvements, like runtime calibration, are not masked
+ // during requantization.
+ double incRes = 0.25 * resolution;
+ *value = round(static_cast<double>(*value) / incRes) * incRes;
+}
+
+// Ensures a sensor event doesn't provide values finer grained than its sensor resolution allows.
+void quantizeSensorEventValues(sensors_event_t *event, float resolution);
+
+// Provides a default resolution for simple sensor types if one wasn't provided by the HAL.
+float defaultResolutionForType(int type);
+
class HidlServiceRegistrationWaiter : public IServiceNotification {
public: