java.security.InvalidKeyException: Illegal key size or default parameters AES加密报错的解决办法

java.security.InvalidKeyException: Illegal key size or default parameters

这样一个错。查了下说 JDK8 默认的加密长度是 128 位的，超过这个长度就需要自己安装扩展。安装扩展比较麻烦，后来在 stackoverflow 上找到了比较简单的方法，只需要加代码就可以，不用安装扩展文件。

具体代码

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

static {
    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
}