Merge pull request #2034 from IABTechLab/sch-UID2-5854_key_id_patch

writing key id as 3 bytes big endian format

Author: gmsdelmundo

src/main/java/com/uid2/operator/service/V4TokenUtils.java

@@ -4,7 +4,6 @@
 import javax.crypto.spec.IvParameterSpec;
 import javax.crypto.spec.SecretKeySpec;
 import io.vertx.core.buffer.Buffer;
-
 import java.io.ByteArrayOutputStream;
 import java.util.Arrays;
 
@@ -14,18 +13,22 @@ public final class V4TokenUtils {
     private V4TokenUtils() {
     }
 
+    private static byte[] getKeyIdBytes(int keyId) {
+        return new byte[] {
+                (byte) ((keyId >> 16) & 0xFF),   // MSB
+                (byte) ((keyId >> 8) & 0xFF),    // Middle
+                (byte) (keyId & 0xFF),           // LSB
+        };
+    }
+
     public static byte[] buildAdvertisingIdV4(byte metadata, byte[] firstLevelHash, int keyId, String key, String salt) throws Exception {
         byte[] firstLevelHashLast16Bytes = Arrays.copyOfRange(firstLevelHash, firstLevelHash.length - 16, firstLevelHash.length);
         byte[] iv = V4TokenUtils.generateIV(salt, firstLevelHashLast16Bytes, metadata, keyId);
         byte[] encryptedFirstLevelHash = V4TokenUtils.encryptHash(key, firstLevelHashLast16Bytes, iv);
 
         Buffer buffer = Buffer.buffer();
         buffer.appendByte(metadata);
-        buffer.appendBytes(new byte[] {
-                (byte) (keyId & 0xFF),           // LSB
-                (byte) ((keyId >> 8) & 0xFF),    // Middle
-                (byte) ((keyId >> 16) & 0xFF)    // MSB
-        });
+        buffer.appendBytes(getKeyIdBytes(keyId));
         buffer.appendBytes(iv);
         buffer.appendBytes(encryptedFirstLevelHash);
 
@@ -40,7 +43,7 @@ public static byte[] generateIV(String salt, byte[] firstLevelHashLast16Bytes, b
         ivBase.write(salt.getBytes());
         ivBase.write(firstLevelHashLast16Bytes);
         ivBase.write(metadata);
-        ivBase.write(keyId);
+        ivBase.write(getKeyIdBytes(keyId));
         return Arrays.copyOfRange(EncodingUtils.getSha256Bytes(ivBase.toByteArray()), 0, IV_LENGTH);
     }
 

src/test/java/com/uid2/operator/service/V4TokenUtilsTest.java

@@ -28,7 +28,7 @@ void testBuildAdvertisingIdV4() throws Exception {
 
         byte extractedMetadata = v4UID[0];
         byte[] keyIdBytes = Arrays.copyOfRange(v4UID, 1, 4);
-        int extractedKeyId = (keyIdBytes[0] & 0xFF) | ((keyIdBytes[1] & 0xFF) << 8) | ((keyIdBytes[2] & 0xFF) << 16);
+        int extractedKeyId = ((keyIdBytes[0] & 0xFF) << 16) | ((keyIdBytes[1] & 0xFF) << 8) | (keyIdBytes[2] & 0xFF);
         byte[] extractedIV = Arrays.copyOfRange(v4UID, 4, 16);
         byte[] extractedEncryptedHash = Arrays.copyOfRange(v4UID, 16, 32);
         byte extractedChecksum = v4UID[32];