我需要解密从服务器接收到的一些数据，制作 API 的程序员将我指向这个 Encrypter类，看看他用什么来加密。

现在根据那个类，我发现使用的算法是AES128 CBC，而且我收到的字符串是Base64编码的并且包含其他数据，而不仅仅是密文。

也就是说，如果我收到以下字符串:

eyJpdiI6InJsSzRlU3pDZTBBUVNwMzdXMjVcL0tBPT0iLCJ2YWx1ZSI6Ik5JOENsSVVWaWk2RGNhNlwvWjJNeG94UzVkclwvMGJOREQreWUyS1UzclRMND0iLCJtYWMiOiJhZTZkYjNkNGM2ZTliNmU0ZTc0MTRiNDBmMzFlZTJhNTczZWIxMjk4N2YwMjlhODA1NTIyMDEzODljNDY2OTk2In0

base64解码后我得到:

{"iv":"rlK4eSzCe0AQSp37W25\/KA==","value":"NI8ClIUVii6Dca6\/Z2MxoxS5dr\/0bNDD+ye2KU3rTL4=","mac":"ae6db3d4c6e9b6e4e7414b40f31ee2a573eb12987f029a80552201389c466996"}

基于 Encrypter 类的 line 99 ( iv = base64_decode($payload['iv']); )，我执行了另一个对 iv 和 value 进行 base64 解码，得到长度为 16 的 iv。我将这些作为参数传递给以下函数:

    public static String decrypt(String iv, String encryptedData) throws Exception {
    byte[] keyValue = "zy2dEd1pKG5i3WuWbvOBolFQR84AYbvN".getBytes();
    Key key = new SecretKeySpec(keyValue, "AES");        
    Cipher c = Cipher.getInstance("AES/CBC/PKCS7Padding");
    c.init(Cipher.DECRYPT_MODE, key, new IvParameterSpec(iv.getBytes()));
    byte[] decordedValue = Base64.decode(encryptedData.getBytes(), Base64.DEFAULT);
    byte[] decValue = c.doFinal(decordedValue);
    return new String(decValue);
}

但我收到以下错误:

10-06 19:13:33.601 12895-12895/? W/System.err: java.security.InvalidAlgorithmParameterException: expected IV length of 16
10-06 19:13:33.601 12895-12895/? W/System.err:     at com.android.org.conscrypt.OpenSSLCipher.engineInitInternal(OpenSSLCipher.java:281)
10-06 19:13:33.601 12895-12895/? W/System.err:     at com.android.org.conscrypt.OpenSSLCipher.engineInit(OpenSSLCipher.java:323)
10-06 19:13:33.601 12895-12895/? W/System.err:     at javax.crypto.Cipher.init(Cipher.java:751)
10-06 19:13:33.601 12895-12895/? W/System.err:     at javax.crypto.Cipher.init(Cipher.java:701)
10-06 19:13:33.601 12895-12895/? W/System.err:     at com.example.kushtrim.testproject.MainActivity.decrypt(MainActivity.java:62)
10-06 19:13:33.601 12895-12895/? W/System.err:     at com.example.kushtrim.testproject.MainActivity.onCreate(MainActivity.java:45)
10-06 19:13:33.601 12895-12895/? W/System.err:     at android.app.Activity.performCreate(Activity.java:5990)
10-06 19:13:33.601 12895-12895/? W/System.err:     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106)
10-06 19:13:33.601 12895-12895/? W/System.err:     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2278)
10-06 19:13:33.601 12895-12895/? W/System.err:     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387)
10-06 19:13:33.601 12895-12895/? W/System.err:     at android.app.ActivityThread.access$800(ActivityThread.java:151)
10-06 19:13:33.601 12895-12895/? W/System.err:     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
10-06 19:13:33.602 12895-12895/? W/System.err:     at android.os.Handler.dispatchMessage(Handler.java:102)
10-06 19:13:33.602 12895-12895/? W/System.err:     at android.os.Looper.loop(Looper.java:135)
10-06 19:13:33.602 12895-12895/? W/System.err:     at android.app.ActivityThread.main(ActivityThread.java:5254)
10-06 19:13:33.602 12895-12895/? W/System.err:     at java.lang.reflect.Method.invoke(Native Method)
10-06 19:13:33.602 12895-12895/? W/System.err:     at java.lang.reflect.Method.invoke(Method.java:372)
10-06 19:13:33.602 12895-12895/? W/System.err:     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
10-06 19:13:33.602 12895-12895/? W/System.err:     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)

注意字符串iv的长度为16，但是iv.getBytes()返回的是一个长度为26的数组。

谁能指出我哪里出错了，我该如何解决。 谢谢/

编辑
评论之后，我做了一些修改，解决了上面的错误:
在我使用 base64 解码 iv 之前，将字节转换为 String，然后将该 String 传递给 decrypt 方法，后者在其上调用 getBytes() 作为返回。这使得字节数组的长度为 26。
将base64解码后得到的byte数组发送给decrypt方法解决了问题。
现在方法如下:

public static String decrypt(byte[] iv, String encryptedData) throws Exception {
    byte[] keyValue = "zy2dEd1pKG5i3WuWbvOBolFQR84AYbvN".getBytes();
    Key key = new SecretKeySpec(keyValue, "AES");
    Cipher c = Cipher.getInstance("AES/CBC/PKCS7Padding");
    c.init(Cipher.DECRYPT_MODE, key, new IvParameterSpec(iv));
    byte[] decordedValue = Base64.decode(encryptedData.getBytes(), Base64.DEFAULT);
    byte[] decValue = c.doFinal(decordedValue);
    return new String(decValue);
}

现在我有另一个奇怪问题:
我首先加密的文本是 KushtrimPacaj ，但解密后的文本是 s:13:"KushtrimPacaj"; 。 其他部分来自哪里？ 13 可能代表 KushtrimPacaj 的长度？

编辑
这是工作代码，以备不时之需:
https://gist.github.com/KushtrimPacaj/43a383ab419fc222f80e

最佳答案

你可以在padAndMcrypt() function中看到, 给定的 $value 是使用 PHP 的 serialize() function 序列化的.你可以re-implement Java 中的 unserialize() 函数，或者如果您总是在 PHP 中加密字符串，您可以自己拆分字节数组。

int firstQuoteIndex = 0;
while(decValue[firstQuoteIndex] != (byte)'"') firstQuoteIndex++;
return new String(Arrays.copyOfRange(decValue, firstQuoteIndex + 1, decValue.length-2));

完整代码:

public static String decrypt(byte[] keyValue, String ivValue, String encryptedData) throws Exception {
    Key key = new SecretKeySpec(keyValue, "AES");
    byte[] iv = Base64.decode(ivValue.getBytes("UTF-8"), Base64.DEFAULT);
    byte[] decodedValue = Base64.decode(encryptedData.getBytes("UTF-8"), Base64.DEFAULT);

    Cipher c = Cipher.getInstance("AES/CBC/PKCS7Padding"); // or PKCS5Padding
    c.init(Cipher.DECRYPT_MODE, key, new IvParameterSpec(iv));
    byte[] decValue = c.doFinal(decodedValue);

    int firstQuoteIndex = 0;
    while(decValue[firstQuoteIndex] != (byte)'"') firstQuoteIndex++;
    return new String(Arrays.copyOfRange(decValue, firstQuoteIndex + 1, decValue.length-2));
}

验证 MAC 始终是一个好主意，因为它可以防止某些攻击，例如 padding oracle 攻击。这也是一种非常好的检测密文一般修改的方法。

带MAC验证的完整代码:

public static String decrypt(byte[] keyValue, String ivValue, String encryptedData, String macValue) throws Exception {
    Key key = new SecretKeySpec(keyValue, "AES");
    byte[] iv = Base64.decode(ivValue.getBytes("UTF-8"), Base64.DEFAULT);
    byte[] decodedValue = Base64.decode(encryptedData.getBytes("UTF-8"), Base64.DEFAULT);

    SecretKeySpec macKey = new SecretKeySpec(keyValue, "HmacSHA256");
    Mac hmacSha256 = Mac.getInstance("HmacSHA256");
    hmacSha256.init(macKey);
    hmacSha256.update(ivValue.getBytes("UTF-8"));
    byte[] calcMac = hmacSha256.doFinal(encryptedData.getBytes("UTF-8"));
    byte[] mac = Hex.decodeHex(macValue.toCharArray());
    if (!secureEquals(calcMac, mac))
        return null; // or throw exception

    Cipher c = Cipher.getInstance("AES/CBC/PKCS7Padding"); // or PKCS5Padding
    c.init(Cipher.DECRYPT_MODE, key, new IvParameterSpec(iv));
    byte[] decValue = c.doFinal(decodedValue);

    int firstQuoteIndex = 0;
    while(decValue[firstQuoteIndex] != (byte)'"') firstQuoteIndex++;
    return new String(Arrays.copyOfRange(decValue, firstQuoteIndex + 1, decValue.length-2));
}

/* Constant-time compare to prevent timing attacks on invalid authentication tags. */
public static boolean secureEquals(final byte[] known, final byte[] user) {
    int knownLen = known.length;
    int userLen = user.length;

    int result = knownLen ^ userLen;
    for (int i = 0; i < knownLen; i++) {
        result |= known[i] ^ user[i % userLen];
    }
    return result == 0;
}

关于java - 如何解密在 Laravel 中使用 Crypt 加密的 Java (Android) 文本？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/32975822/