Java Security: Illegal key size or default parameters?

Question

I had asked a question about this earlier, but it didn\'t get answered right and led nowhere.

So I\'ve clarified few details on the problem and I would really like t

Answer 1

This is a code only solution. No need to download or mess with configuration files.

It's a reflection based solution, tested on java 8

Call this method once, early in your program.

//Imports

import javax.crypto.Cipher;
import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.Modifier;
import java.util.Map;

//method

public static void fixKeyLength() {
    String errorString = "Failed manually overriding key-length permissions.";
    int newMaxKeyLength;
    try {
        if ((newMaxKeyLength = Cipher.getMaxAllowedKeyLength("AES")) < 256) {
            Class c = Class.forName("javax.crypto.CryptoAllPermissionCollection");
            Constructor con = c.getDeclaredConstructor();
            con.setAccessible(true);
            Object allPermissionCollection = con.newInstance();
            Field f = c.getDeclaredField("all_allowed");
            f.setAccessible(true);
            f.setBoolean(allPermissionCollection, true);

            c = Class.forName("javax.crypto.CryptoPermissions");
            con = c.getDeclaredConstructor();
            con.setAccessible(true);
            Object allPermissions = con.newInstance();
            f = c.getDeclaredField("perms");
            f.setAccessible(true);
            ((Map) f.get(allPermissions)).put("*", allPermissionCollection);

            c = Class.forName("javax.crypto.JceSecurityManager");
            f = c.getDeclaredField("defaultPolicy");
            f.setAccessible(true);
            Field mf = Field.class.getDeclaredField("modifiers");
            mf.setAccessible(true);
            mf.setInt(f, f.getModifiers() & ~Modifier.FINAL);
            f.set(null, allPermissions);

            newMaxKeyLength = Cipher.getMaxAllowedKeyLength("AES");
        }
    } catch (Exception e) {
        throw new RuntimeException(errorString, e);
    }
    if (newMaxKeyLength < 256)
        throw new RuntimeException(errorString); // hack failed
}

Credits: Delthas