Use hmac to sign events in InputDispatcher
InputDispatcher will now be able to sign events. Add two static methods
to InputDispatcher class, for signing events, and for checking the event
signature.
The new methods can verify whether a MotionEntry object was actually created by
the Input system and whether the MotionEntry object was modified
afterwards.
Bug: 134977432
Test: none
Change-Id: Ica11bccd0c3fb065b02634bd236ae5a46f6b19ee
diff --git a/services/inputflinger/dispatcher/InputDispatcher.cpp b/services/inputflinger/dispatcher/InputDispatcher.cpp
index 75bc0aa..f9a86dd 100644
--- a/services/inputflinger/dispatcher/InputDispatcher.cpp
+++ b/services/inputflinger/dispatcher/InputDispatcher.cpp
@@ -2433,12 +2433,16 @@
switch (eventEntry->type) {
case EventEntry::Type::KEY: {
KeyEntry* keyEntry = static_cast<KeyEntry*>(eventEntry);
+ VerifiedKeyEvent verifiedEvent = verifiedKeyEventFromKeyEntry(*keyEntry);
+ verifiedEvent.flags = dispatchEntry->resolvedFlags & VERIFIED_KEY_EVENT_FLAGS;
+ verifiedEvent.action = dispatchEntry->resolvedAction;
+ std::array<uint8_t, 32> hmac = mHmacKeyManager.sign(verifiedEvent);
// Publish the key event.
status = connection->inputPublisher
.publishKeyEvent(dispatchEntry->seq, keyEntry->deviceId,
keyEntry->source, keyEntry->displayId,
- INVALID_HMAC, dispatchEntry->resolvedAction,
+ std::move(hmac), dispatchEntry->resolvedAction,
dispatchEntry->resolvedFlags, keyEntry->keyCode,
keyEntry->scanCode, keyEntry->metaState,
keyEntry->repeatCount, keyEntry->downTime,
@@ -2482,12 +2486,18 @@
usingCoords = scaledCoords;
}
}
+ VerifiedMotionEvent verifiedEvent =
+ verifiedMotionEventFromMotionEntry(*motionEntry);
+ verifiedEvent.actionMasked =
+ dispatchEntry->resolvedAction & AMOTION_EVENT_ACTION_MASK;
+ verifiedEvent.flags = dispatchEntry->resolvedFlags & VERIFIED_MOTION_EVENT_FLAGS;
+ std::array<uint8_t, 32> hmac = mHmacKeyManager.sign(verifiedEvent);
// Publish the motion event.
status = connection->inputPublisher
.publishMotionEvent(dispatchEntry->seq, motionEntry->deviceId,
motionEntry->source, motionEntry->displayId,
- INVALID_HMAC, dispatchEntry->resolvedAction,
+ std::move(hmac), dispatchEntry->resolvedAction,
motionEntry->actionButton,
dispatchEntry->resolvedFlags,
motionEntry->edgeFlags, motionEntry->metaState,
@@ -3392,7 +3402,36 @@
}
std::unique_ptr<VerifiedInputEvent> InputDispatcher::verifyInputEvent(const InputEvent& event) {
- return nullptr;
+ std::array<uint8_t, 32> calculatedHmac;
+ std::unique_ptr<VerifiedInputEvent> result;
+ switch (event.getType()) {
+ case AINPUT_EVENT_TYPE_KEY: {
+ const KeyEvent& keyEvent = static_cast<const KeyEvent&>(event);
+ VerifiedKeyEvent verifiedKeyEvent = verifiedKeyEventFromKeyEvent(keyEvent);
+ result = std::make_unique<VerifiedKeyEvent>(verifiedKeyEvent);
+ calculatedHmac = mHmacKeyManager.sign(verifiedKeyEvent);
+ break;
+ }
+ case AINPUT_EVENT_TYPE_MOTION: {
+ const MotionEvent& motionEvent = static_cast<const MotionEvent&>(event);
+ VerifiedMotionEvent verifiedMotionEvent =
+ verifiedMotionEventFromMotionEvent(motionEvent);
+ result = std::make_unique<VerifiedMotionEvent>(verifiedMotionEvent);
+ calculatedHmac = mHmacKeyManager.sign(verifiedMotionEvent);
+ break;
+ }
+ default: {
+ ALOGE("Cannot verify events of type %" PRId32, event.getType());
+ return nullptr;
+ }
+ }
+ if (calculatedHmac == INVALID_HMAC) {
+ return nullptr;
+ }
+ if (calculatedHmac != event.getHmac()) {
+ return nullptr;
+ }
+ return result;
}
bool InputDispatcher::hasInjectionPermission(int32_t injectorPid, int32_t injectorUid) {