Merge pull request #33 from neXenio/feature/32-Constant-Time-Algorith…

…m-for-MAC-Verification Feature/32 constant time algorithm for mac verification
neXenio · Aug 16, 2021 · 9ec410b · 9ec410b
2 parents a086049 + 0cf5f6e
commit 9ec410b
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Showing 2 changed files with 13 additions and 5 deletions.
diff --git a/rxkeystore/src/androidTest/java/com/nexenio/rxkeystore/provider/mac/BaseMacProviderTest.java b/rxkeystore/src/androidTest/java/com/nexenio/rxkeystore/provider/mac/BaseMacProviderTest.java
@@ -11,7 +11,6 @@
 import org.junit.Test;
 
 import java.nio.charset.StandardCharsets;
-import java.util.Arrays;
 
 import javax.crypto.SecretKey;
 
@@ -66,7 +65,7 @@ public void sign_validData_emitsSignature() {
     public void sign_subsequentCallsWithSameKey_emitsSameSignature() {
         Single<byte[]> signSingle = macProvider.sign(MESSAGE, firstSecretKey);
 
-        Single.zip(signSingle, signSingle, Arrays::equals)
+        Single.zip(signSingle, signSingle, BaseMacProvider::isEqual)
                 .test()
                 .assertValue(true);
     }

diff --git a/rxkeystore/src/main/java/com/nexenio/rxkeystore/provider/mac/BaseMacProvider.java b/rxkeystore/src/main/java/com/nexenio/rxkeystore/provider/mac/BaseMacProvider.java
@@ -3,8 +3,6 @@
 import com.nexenio.rxkeystore.RxKeyStore;
 import com.nexenio.rxkeystore.provider.BaseCryptoProvider;
 
-import java.util.Arrays;
-
 import javax.crypto.Mac;
 import javax.crypto.SecretKey;
 
@@ -48,7 +46,7 @@ public Completable verify(@NonNull byte[] data, @NonNull byte[] signature, @NonN
     @Override
     public Single<Boolean> getVerificationResult(@NonNull byte[] data, @NonNull byte[] signature, @NonNull SecretKey secretKey) {
         return sign(data, secretKey)
-                .map(computedSignature -> Arrays.equals(computedSignature, signature))
+                .map(computedSignature -> isEqual(computedSignature, signature))
                 .onErrorReturnItem(false);
     }
 
@@ -66,6 +64,17 @@ protected Single<Mac> getMacInstance() {
         ));
     }
 
+    public static boolean isEqual(byte[] a, byte[] b) {
+        if (a.length != b.length) {
+            return false;
+        }
+        byte result = 0;
+        for (byte i = 0; i < a.length; i++) {
+            result |= (byte) (a[i] ^ b[i]);
+        }
+        return result == 0;
+    }
+
     public String getMacAlgorithm() {
         return macAlgorithm;
     }