Fixed MLS test: converted encoded P521 private keys to match required length

Author: royb

Diff for: mls/src/test/java/org/bouncycastle/mls/test/ClientVectorTest.java

@@ -3,6 +3,7 @@
 import java.io.BufferedReader;
 import java.io.InputStream;
 import java.io.InputStreamReader;
+import java.math.BigInteger;
 import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
@@ -11,6 +12,7 @@
 
 import junit.framework.TestCase;
 import org.bouncycastle.crypto.AsymmetricCipherKeyPair;
+import org.bouncycastle.crypto.params.ECPrivateKeyParameters;
 import org.bouncycastle.mls.TreeKEM.TreeKEMPublicKey;
 import org.bouncycastle.mls.codec.MLSInputStream;
 import org.bouncycastle.mls.codec.MLSMessage;
@@ -20,6 +22,7 @@
 import org.bouncycastle.mls.protocol.Group;
 import org.bouncycastle.test.TestResourceFinder;
 import org.bouncycastle.util.Arrays;
+import org.bouncycastle.util.BigIntegers;
 import org.bouncycastle.util.encoders.Hex;
 
 public class ClientVectorTest
@@ -134,6 +137,14 @@ public Epoch(List<byte[]> proposals, byte[] commit, byte[] epoch_authenticator)
                         }
 
                         MlsCipherSuite suite = MlsCipherSuite.getSuite(cipherSuite);
+
+                        if(cipherSuite == MlsCipherSuite.MLS_256_DHKEMP521_AES256GCM_SHA512_P521)
+                        {
+                            //Converts encoded HPKE private key for P521 to comply with length constraints
+                            encryption_priv =  BigIntegers.asUnsignedByteArray(66, new BigInteger(1, encryption_priv));
+                            init_priv =  BigIntegers.asUnsignedByteArray(66, new BigInteger(1, init_priv));
+                        }
+
                         AsymmetricCipherKeyPair leafKeyPair = suite.getHPKE().deserializePrivateKey(encryption_priv, null);
                         Map<Secret, byte[]> externalPsks = new HashMap<Secret, byte[]>();
                         for (PreSharedKeyID ext : externalPSKs)