Java的：从applet的修补客户端安全策略AES256 [英] Java: Patching client side security policy from applet for AES256

问题描述

我需要在商业Web应用程序AES256加密/解密。
目前一切都很好用的128密钥大小这不是加密满意，所以我的问题是如何最好地克​​服这个问题，而不需要用户手动安装任何东西。

I require AES256 encryption/decryption in a commercial web application. Currently everything is good with a key size of 128. This is not satisfactory cryptographically so my problem is how best to get round this issue without requiring the user to install anything manually.

我有Oracle的无限管辖权的jar文件，但我不知道，如果用户的JRE / lib / security目录替换这些都将是与旧版本兼容。很显然，我不想破坏用户的JRE。我也有写权限到我的JRE安全目录，但我认为有些用户不具备这些权限。

I have the unlimited jurisdiction jar files from Oracle but I have no idea if replacing these in the user's JRE/lib/security directory will be compatible with older versions. Obviously I don't want to corrupt the user's JRE. Also I have write permission to my JRE security directory but I assume some user's will not have these privileges.

有没有解决这个问题，一个简单的办法，还是我坚持要么弱加密或者用户潜在的问题环节？

Is there a simple way around this issue, or am I stuck with either weak encryption or a potentially problematic step for users?

更新unrestricting javax.crypto.JceSecurity

Update for "unrestricting" javax.crypto.JceSecurity

@ntoskml你是正确的。 getMaxAllowedKeyLength 仍返回有限密钥大小，但加密与密钥大小== 256 :)成功。我会更新我的测试方法，并设置密钥长度，如果强加密可用。谢谢

@ntoskml You are correct. getMaxAllowedKeyLength still returns the limited key size but the encryption succeeds with key size == 256 :). I will update my test method and set the key size if strong encryption is available. Thanks

>>> from javax.crypto import Cipher
>>> Cipher.getMaxAllowedKeyLength("AES")
128
>>> from java.lang import Class
>>> c = Class.forName("javax.crypto.JceSecurity")
>>> isRestricted = c.getDeclaredField("isRestricted")
>>> isRestricted.setAccessible(True)
>>> isRestricted.set(None, False)
>>> isRestricted.get(None)
False
>>> Cipher.getMaxAllowedKeyLength("AES")
128
>>> from javax.crypto import KeyGenerator
>>> kge = KeyGenerator.getInstance("AES")
>>> kge.init(256)
>>> aesKey = kgen.generateKey()
>>> c2 = Cipher.getInstance("AES")
>>> c2.init(Cipher.ENCRYPT_MODE, aesKey)
>>> c2.doFinal("test")
array('b', [-81, 99, -61, -51, 93, -42, -68, -28, 107, 59, -109, -98, -25, 127, 37, 23])

和重启后的测试案例的Jython控制台

And the test case after restarting Jython console

>>> # Reflection as above
>>> isRestricted.get(None)
True
>>> kge.init(256)
>>> aesKey = kge.generateKey()
>>> c2.init(Cipher.ENCRYPT_MODE, aesKey)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
        at javax.crypto.Cipher.checkCryptoPerm(Cipher.java:1011)
        at javax.crypto.Cipher.implInit(Cipher.java:786)
        at javax.crypto.Cipher.chooseProvider(Cipher.java:849)
        at javax.crypto.Cipher.init(Cipher.java:1213)
        at javax.crypto.Cipher.init(Cipher.java:1153)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
        at java.lang.reflect.Method.invoke(Unknown Source)

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

宾果:)感谢分享@ntoskml

Bingo :) Thanks for sharing @ntoskml

推荐答案

编辑：下面是一个更新的回答这个问题：<一href=\"http://stackoverflow.com/questions/1179672/unlimited-strength-jce-policy-files/22492582#22492582\">"Unlimited实力＆QUOT; JCE策略文件

Here's an updated answer to this question: "Unlimited Strength" JCE Policy Files

这是可能简单地通过使用反射几行禁用键的大小限制。我们用我们的节目这个方法，需要访问256位加密技术的互操作性。

It is possible to disable the key size restrictions simply by using a few lines of reflection. We use this method in our program which needs access to 256-bit cryptography for interoperability purposes.

private static void removeCryptographyRestrictions() {
    if (!isRestrictedCryptography()) {
        return;
    }
    try {
        java.lang.reflect.Field isRestricted;
        try {
            final Class<?> c = Class.forName("javax.crypto.JceSecurity");
            isRestricted = c.getDeclaredField("isRestricted");
        } catch (final ClassNotFoundException e) {
            try {
                // Java 6 has obfuscated JCE classes
                final Class<?> c = Class.forName("javax.crypto.SunJCE_b");
                isRestricted = c.getDeclaredField("g");
            } catch (final ClassNotFoundException e2) {
                throw e;
            }
        }
        isRestricted.setAccessible(true);
        isRestricted.set(null, false);
    } catch (final Throwable e) {
        logger.log(Level.WARNING,
                "Failed to remove cryptography restrictions", e);
    }
}

private static boolean isRestrictedCryptography() {
    return "Java(TM) SE Runtime Environment"
            .equals(System.getProperty("java.runtime.name"));
}

然而，我们的程序是不是一个小程序，我不知道小程序是否有权访问该反射API。

However, our program is not an applet, and I am not sure whether applets have access to the reflection API.

有关合法性问题也依然存在。有该限制的原因。如果您担心咨询律师。

The question about legality also remains. There is a reason for that limit. Consult a lawyer if you are concerned.

如果可能，尽量保持它的128位密钥。即使考虑当考虑摩尔定律，打破了128位AES将需要数十亿美元在数十亿年。更长的密钥提供了在现实世界中没有的好处 - 尤其是当密钥是从密码，不具有熵任何接近256位反正衍生

If possible, try to keep it to 128-bit keys. Even when taking Moore's law into consideration, breaking 128-bit AES would take billions upon billions of years. Longer keys offer no benefit in the real world – particularly when the keys are derived from passwords, which don't have anywhere near 256 bits of entropy anyway.

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