Crypto: Change RFC 7748 DH error to a checked exception

so things are cleaned up properly

core/java/src/com/southernstorm/noise/crypto/x25519/Curve25519.java

@@ -22,6 +22,7 @@
 
 package com.southernstorm.noise.crypto.x25519;
 
+import java.security.GeneralSecurityException;
 import java.util.Arrays;
 
 /**
@@ -471,9 +472,9 @@ public final class Curve25519 {
 	 * @param publicKey The public key to use in the evaluation, or null
 	 *                  MUST have MSB high bit cleared, i.e. publicKey[31] & 0x80 == 0
 	 * if the base point of the curve should be used.
-	 * @throws IllegalArgumentException on low-order input see RFC 7748
+	 * @throws GeneralSecurityException on low-order input see RFC 7748
 	 */
-	public static void eval(byte[] result, int offset, byte[] privateKey, byte[] publicKey)
+	public static void eval(byte[] result, int offset, byte[] privateKey, byte[] publicKey) throws GeneralSecurityException
 	{
 		Curve25519 state = new Curve25519();
 		try {
@@ -530,7 +531,7 @@ public final class Curve25519 {
 			b |= result[offset + index];
 		    }
 		    if (b == 0)
-			throw new IllegalArgumentException("low order input RFC 7748");
+			throw new GeneralSecurityException("low order input RFC 7748");
 		} finally {
 			// Clean up all temporary state before we exit.
 			state.destroy();

core/java/src/net/i2p/crypto/KeyGenerator.java

@@ -206,7 +206,11 @@ public final class KeyGenerator {
                 // worth doing?
             } while (bpriv[31] == 0);
             byte[] bpub = new byte[32];
-            Curve25519.eval(bpub, 0, bpriv, null);
+            try {
+                Curve25519.eval(bpub, 0, bpriv, null);
+            } catch (GeneralSecurityException gse) {
+                throw new IllegalArgumentException("Bad keys", gse);
+            }
             pub = new PublicKey(type, bpub);
             priv = new PrivateKey(type, bpriv, pub);
             break;
@@ -245,7 +249,11 @@ public final class KeyGenerator {
           case MLKEM768_X25519:
           case MLKEM1024_X25519:
             data = new byte[32];
-            Curve25519.eval(data, 0, priv.getData(), null);
+            try {
+                Curve25519.eval(data, 0, priv.getData(), null);
+            } catch (GeneralSecurityException gse) {
+                throw new IllegalArgumentException("Bad keys", gse);
+            }
             break;
 
           default:

core/java/src/net/i2p/crypto/x25519/X25519DH.java

@@ -1,5 +1,7 @@
 package net.i2p.crypto.x25519;
 
+import java.security.GeneralSecurityException;
+
 import com.southernstorm.noise.crypto.x25519.Curve25519;
 
 import net.i2p.crypto.EncType;
@@ -30,7 +32,11 @@ public class X25519DH {
         if (priv.getType() != TYPE || pub.getType() != TYPE)
             throw new IllegalArgumentException();
         byte[] rv = new byte[32];
-        Curve25519.eval(rv, 0, priv.getData(), pub.getData());
+        try {
+            Curve25519.eval(rv, 0, priv.getData(), pub.getData());
+        } catch (GeneralSecurityException gse) {
+            throw new IllegalArgumentException("Bad keys", gse);
+        }
         return new SessionKey(rv);
     }