Fix HMAC Compare time attack
Added constant time HMAC comparison preventing attackers being able to
forge HMAC for input by measuring the time difference between
non-constant time comparison of HMAC
Bug: 261085213
Test: None
Tag: #security
Change-Id: I7cd6b68589fd0042b9396dc599b917a0f3220ff7
diff --git a/services/inputflinger/dispatcher/InputDispatcher.cpp b/services/inputflinger/dispatcher/InputDispatcher.cpp
index cd427f0..5ea543f 100644
--- a/services/inputflinger/dispatcher/InputDispatcher.cpp
+++ b/services/inputflinger/dispatcher/InputDispatcher.cpp
@@ -31,6 +31,7 @@
#endif
#include <input/InputDevice.h>
#include <input/PrintTools.h>
+#include <openssl/mem.h>
#include <powermanager/PowerManager.h>
#include <unistd.h>
#include <utils/Trace.h>
@@ -4629,7 +4630,7 @@
if (calculatedHmac == INVALID_HMAC) {
return nullptr;
}
- if (calculatedHmac != event.getHmac()) {
+ if (0 != CRYPTO_memcmp(calculatedHmac.data(), event.getHmac().data(), calculatedHmac.size())) {
return nullptr;
}
return result;