Add HmacKeyManager to InputDispatcher (342c9270) · Commits · e / os / android_frameworks_native

services/inputflinger/Android.bp

+1 −0

Original line number	Diff line number	Diff line
		@@ -40,6 +40,7 @@ cc_library_shared {
		"libinputreporter",
		"libinputreader",
		"libbinder",
		"libcrypto",
		"libcutils",
		"libhidlbase",
		"libinput",

services/inputflinger/dispatcher/Android.bp

+1 −0

Original line number	Diff line number	Diff line
		@@ -28,6 +28,7 @@ cc_library_static {
		],
		shared_libs: [
		"libbase",
		"libcrypto",
		"libcutils",
		"libinput",
		"libinputreporter",

services/inputflinger/dispatcher/InputDispatcher.cpp

+51 −0

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		@@ -61,6 +61,8 @@ static constexpr bool DEBUG_FOCUS = false;
		#include <android-base/stringprintf.h>
		#include <binder/Binder.h>
		#include <log/log.h>
		#include <openssl/hmac.h>
		#include <openssl/rand.h>
		#include <powermanager/PowerManager.h>
		#include <utils/Trace.h>

		@@ -325,6 +327,55 @@ static std::unique_ptr<DispatchEntry> createDispatchEntry(const InputTarget& inp
		return dispatchEntry;
		}

		static std::array<uint8_t, 128> getRandomKey() {
		std::array<uint8_t, 128> key;
		if (RAND_bytes(key.data(), key.size()) != 1) {
		LOG_ALWAYS_FATAL("Can't generate HMAC key");
		}
		return key;
		}

		// --- HmacKeyManager ---

		HmacKeyManager::HmacKeyManager() : mHmacKey(getRandomKey()) {}

		std::array<uint8_t, 32> HmacKeyManager::sign(const VerifiedInputEvent& event) const {
		size_t size;
		switch (event.type) {
		case VerifiedInputEvent::Type::KEY: {
		size = sizeof(VerifiedKeyEvent);
		break;
		}
		case VerifiedInputEvent::Type::MOTION: {
		size = sizeof(VerifiedMotionEvent);
		break;
		}
		}
		std::vector<uint8_t> data;
		const uint8_t* start = reinterpret_cast<const uint8_t*>(&event);
		data.assign(start, start + size);
		return sign(data);
		}

		std::array<uint8_t, 32> HmacKeyManager::sign(const std::vector<uint8_t>& data) const {
		// SHA256 always generates 32-bytes result
		std::array<uint8_t, 32> hash;
		unsigned int hashLen = 0;
		uint8_t* result = HMAC(EVP_sha256(), mHmacKey.data(), mHmacKey.size(), data.data(), data.size(),
		hash.data(), &hashLen);
		if (result == nullptr) {
		ALOGE("Could not sign the data using HMAC");
		return INVALID_HMAC;
		}

		if (hashLen != hash.size()) {
		ALOGE("HMAC-SHA256 has unexpected length");
		return INVALID_HMAC;
		}

		return hash;
		}

		// --- InputDispatcher ---

		InputDispatcher::InputDispatcher(const sp<InputDispatcherPolicyInterface>& policy)

services/inputflinger/dispatcher/InputDispatcher.h

+10 −0

Original line number	Diff line number	Diff line
		@@ -56,6 +56,16 @@ namespace android::inputdispatcher {

		class Connection;

		class HmacKeyManager {
		public:
		HmacKeyManager();
		std::array<uint8_t, 32> sign(const VerifiedInputEvent& event) const;

		private:
		std::array<uint8_t, 32> sign(const std::vector<uint8_t>& data) const;
		const std::array<uint8_t, 128> mHmacKey;
		};

		/* Dispatches events to input targets. Some functions of the input dispatcher, such as
		* identifying input targets, are controlled by a separate policy object.
		*

services/inputflinger/tests/InputDispatcher_test.cpp

+75 −0

Original line number	Diff line number	Diff line
		@@ -43,6 +43,18 @@ struct PointF {
		float y;
		};

		/**
		* Return a DOWN key event with KEYCODE_A.
		*/
		static KeyEvent getTestKeyEvent() {
		KeyEvent event;

		event.initialize(DEVICE_ID, AINPUT_SOURCE_KEYBOARD, ADISPLAY_ID_NONE, INVALID_HMAC,
		AKEY_EVENT_ACTION_DOWN, 0, AKEYCODE_A, KEY_A, AMETA_NONE, 0, ARBITRARY_TIME,
		ARBITRARY_TIME);
		return event;
		}

		// --- FakeInputDispatcherPolicy ---

		class FakeInputDispatcherPolicy : public InputDispatcherPolicyInterface {
		@@ -197,6 +209,69 @@ private:
		}
		};

		// --- HmacKeyManagerTest ---

		class HmacKeyManagerTest : public testing::Test {
		protected:
		HmacKeyManager mHmacKeyManager;
		};

		/**
		* Ensure that separate calls to sign the same data are generating the same key.
		* We avoid asserting against INVALID_HMAC. Since the key is random, there is a non-zero chance
		* that a specific key and data combination would produce INVALID_HMAC, which would cause flaky
		* tests.
		*/
		TEST_F(HmacKeyManagerTest, GeneratedHmac_IsConsistent) {
		KeyEvent event = getTestKeyEvent();
		VerifiedKeyEvent verifiedEvent = verifiedKeyEventFromKeyEvent(event);

		std::array<uint8_t, 32> hmac1 = mHmacKeyManager.sign(verifiedEvent);
		std::array<uint8_t, 32> hmac2 = mHmacKeyManager.sign(verifiedEvent);
		ASSERT_EQ(hmac1, hmac2);
		}

		/**
		* Ensure that changes in VerifiedKeyEvent produce a different hmac.
		*/
		TEST_F(HmacKeyManagerTest, GeneratedHmac_ChangesWhenFieldsChange) {
		KeyEvent event = getTestKeyEvent();
		VerifiedKeyEvent verifiedEvent = verifiedKeyEventFromKeyEvent(event);
		std::array<uint8_t, 32> initialHmac = mHmacKeyManager.sign(verifiedEvent);

		verifiedEvent.deviceId += 1;
		ASSERT_NE(initialHmac, mHmacKeyManager.sign(verifiedEvent));

		verifiedEvent.source += 1;
		ASSERT_NE(initialHmac, mHmacKeyManager.sign(verifiedEvent));

		verifiedEvent.eventTimeNanos += 1;
		ASSERT_NE(initialHmac, mHmacKeyManager.sign(verifiedEvent));

		verifiedEvent.displayId += 1;
		ASSERT_NE(initialHmac, mHmacKeyManager.sign(verifiedEvent));

		verifiedEvent.action += 1;
		ASSERT_NE(initialHmac, mHmacKeyManager.sign(verifiedEvent));

		verifiedEvent.downTimeNanos += 1;
		ASSERT_NE(initialHmac, mHmacKeyManager.sign(verifiedEvent));

		verifiedEvent.flags += 1;
		ASSERT_NE(initialHmac, mHmacKeyManager.sign(verifiedEvent));

		verifiedEvent.keyCode += 1;
		ASSERT_NE(initialHmac, mHmacKeyManager.sign(verifiedEvent));

		verifiedEvent.scanCode += 1;
		ASSERT_NE(initialHmac, mHmacKeyManager.sign(verifiedEvent));

		verifiedEvent.metaState += 1;
		ASSERT_NE(initialHmac, mHmacKeyManager.sign(verifiedEvent));

		verifiedEvent.repeatCount += 1;
		ASSERT_NE(initialHmac, mHmacKeyManager.sign(verifiedEvent));
		}

		// --- InputDispatcherTest ---