Fix legacy Ed448 signature field parsing

Author: vanitasvitae

pg/src/main/java/org/bouncycastle/openpgp/PGPSignature.java

@@ -19,6 +19,7 @@
 import org.bouncycastle.bcpg.SignatureSubpacket;
 import org.bouncycastle.bcpg.TrustPacket;
 import org.bouncycastle.math.ec.rfc8032.Ed25519;
+import org.bouncycastle.math.ec.rfc8032.Ed448;
 import org.bouncycastle.openpgp.operator.PGPContentVerifier;
 import org.bouncycastle.openpgp.operator.PGPContentVerifierBuilder;
 import org.bouncycastle.openpgp.operator.PGPContentVerifierBuilderProvider;
@@ -454,9 +455,19 @@ else if (getKeyAlgorithm() == PublicKeyAlgorithmTags.EDDSA_LEGACY)
             {
                 byte[] a = BigIntegers.asUnsignedByteArray(sigValues[0].getValue());
                 byte[] b = BigIntegers.asUnsignedByteArray(sigValues[1].getValue());
-                signature = new byte[Ed25519.SIGNATURE_SIZE];
-                System.arraycopy(a, 0, signature, Ed25519.PUBLIC_KEY_SIZE - a.length, a.length);
-                System.arraycopy(b, 0, signature, Ed25519.SIGNATURE_SIZE - b.length, b.length);
+                if (a.length + b.length == Ed25519.SIGNATURE_SIZE)
+                {
+                    signature = new byte[Ed25519.SIGNATURE_SIZE];
+                    System.arraycopy(a, 0, signature, Ed25519.PUBLIC_KEY_SIZE - a.length, a.length);
+                    System.arraycopy(b, 0, signature, Ed25519.SIGNATURE_SIZE - b.length, b.length);
+                }
+                else
+                {
+                    signature = new byte[Ed448.SIGNATURE_SIZE];
+                    System.arraycopy(a, 0, signature, Ed448.PUBLIC_KEY_SIZE - a.length, a.length);
+                    System.arraycopy(b, 0, signature, Ed448.SIGNATURE_SIZE - b.length, b.length);
+                }
+
             }
             else
             {