使用特定密钥的AES解密不起作用 [英] AES decryption using a specific key not working

问题描述

我有一个PowerShell脚本（如下），该脚本使用特定的密钥（作为字符串）成功地加密和解密了字符串值。

I have a PowerShell script (below) that successfully encrypt and decrypt string values using a specific key (as a string).

现在我正在尝试编写一种C＃方法，可以使用相同的密钥解密值，但是我不确定如何正确使用PasswordDeriveBytes。

Now I'm trying to write a C# method that can decrypt a value using the same key, but I'm not sure how to use PasswordDeriveBytes correctly.

此外，我正在尝试指定Mode和填充AesManaged对象以匹配PowerShell脚本（我知道CBC模式是最安全的，但是如果其他方法工作得更好，我会对其进行更改。）

Also, I'm trying to specify the Mode and Padding for the AesManaged object to match the PowerShell script (I understand that CBC mode is most secured, but I would change it if something else is working better).

任何

测试代码（.Net Framework 4.7）：

// Note: values are hardcoded based on the results from the PowerShell script
var keyString = "8CBaNtMYwAuu2K/xleoRfgPkURaLK82QidlIyg+nFY4=";
var keyBytes = Convert.FromBase64String(keyString.PadLeft(32)); // Not so sure about this
var ivBytes = Convert.FromBase64String(keyString.PadLeft(16)); // Not so sure about this
var encryptedString = "JW9CDowP0tRGr0Xi7vLxxXv0+fvMzQzopQucLOaeU7s=";
var encryptedByteArray = Convert.FromBase64String(encryptedString);
var test = Cryptography.DecryptStringFromBytes_Aes(encryptedByteArray, keyBytes, ivBytes);

解密方法（不起作用）：

namespace Test.Security
{
    using System;
    using System.IO;
    using System.Security.Cryptography;

    public class Cryptography
    {
        // Note: this method is a Microsoft example, adding PasswordDeriveBytes and specific settings
        // https://docs.microsoft.com/en-us/dotnet/api/system.security.cryptography.aesmanaged?view=netframework-4.7.2
        public static string DecryptStringFromBytes_Aes(byte[] cipherText, byte[] key, byte[] iv)
        {
            // Check arguments.
            if (cipherText == null || cipherText.Length <= 0)
                throw new ArgumentNullException("cipherText");
            if (key == null || key.Length <= 0)
                throw new ArgumentNullException("Key");
            if (iv == null || iv.Length <= 0)
                throw new ArgumentNullException("IV");

            string plaintext = null;

            using (AesManaged aesAlg = new AesManaged())
            {
                var passwordDerivedbytes = new PasswordDeriveBytes(key, iv);
                aesAlg.Key = passwordDerivedbytes.GetBytes(aesAlg.KeySize / 8);
                aesAlg.IV = passwordDerivedbytes.GetBytes(aesAlg.BlockSize / 8);
                aesAlg.Mode = CipherMode.CBC;
                aesAlg.Padding = PaddingMode.Zeros;
                aesAlg.KeySize = 256;
                aesAlg.BlockSize = 128;

                ICryptoTransform decryptor = aesAlg.CreateDecryptor(aesAlg.Key, aesAlg.IV);

                using (MemoryStream msDecrypt = new MemoryStream(cipherText))
                {
                    using (CryptoStream csDecrypt = new CryptoStream(msDecrypt, decryptor, CryptoStreamMode.Read))
                    {
                        using (StreamReader srDecrypt = new StreamReader(csDecrypt))
                        {
                            plaintext = srDecrypt.ReadToEnd();
                        }
                    }
                }

            }

            return plaintext;
        }
    }
}

PowerShell脚本（ PowerShell_AES_Encryption_Example.ps1）：

function Create-AesManagedObject($key, $IV) {
    $aesManaged = New-Object "System.Security.Cryptography.AesManaged"
    $aesManaged.Mode = [System.Security.Cryptography.CipherMode]::CBC
    $aesManaged.Padding = [System.Security.Cryptography.PaddingMode]::Zeros
    $aesManaged.BlockSize = 128
    $aesManaged.KeySize = 256
    if ($IV) {
        if ($IV.getType().Name -eq "String") {
            $aesManaged.IV = [System.Convert]::FromBase64String($IV)
        }
        else {
            $aesManaged.IV = $IV
        }
    }
    if ($key) {
        if ($key.getType().Name -eq "String") {
            $aesManaged.Key = [System.Convert]::FromBase64String($key)
        }
        else {
            $aesManaged.Key = $key
        }
    }
    $aesManaged
}

function Create-AesKey() {
    $aesManaged = Create-AesManagedObject
    $aesManaged.GenerateKey()
    [System.Convert]::ToBase64String($aesManaged.Key)
}

function Encrypt-String($key, $unencryptedString) {
    $bytes = [System.Text.Encoding]::UTF8.GetBytes($unencryptedString)
    $aesManaged = Create-AesManagedObject $key
    $encryptor = $aesManaged.CreateEncryptor()
    $encryptedData = $encryptor.TransformFinalBlock($bytes, 0, $bytes.Length);
    [byte[]] $fullData = $aesManaged.IV + $encryptedData
    $aesManaged.Dispose()
    [System.Convert]::ToBase64String($fullData)
}

function Decrypt-String($key, $encryptedStringWithIV) {
    $bytes = [System.Convert]::FromBase64String($encryptedStringWithIV)
    $IV = $bytes[0..15]
    $aesManaged = Create-AesManagedObject $key $IV
    $decryptor = $aesManaged.CreateDecryptor();
    $unencryptedData = $decryptor.TransformFinalBlock($bytes, 16, $bytes.Length - 16);
    $aesManaged.Dispose()
    [System.Text.Encoding]::UTF8.GetString($unencryptedData).Trim([char]0)
}


cls

<#
# This will generate a new valid AES 256 key if needed:
# $key = Create-AesKey
#>

<# 
# This is the hard coded key
#>
$key = "8CBaNtMYwAuu2K/xleoRfgPkURaLK82QidlIyg+nFY4="
Write-Host "key = $key"

$unencryptedString = "blahblahblah"
Write-Host "unencryptedString = $unencryptedString"

$encryptedString = Encrypt-String $key $unencryptedString
Write-Host "encryptedString  = $encryptedString "

$backToPlainText = Decrypt-String $key $encryptedString
Write-Host "backToPlainText = $backToPlainText"


<#
# To run this PowerShell script:
#
# In Windows PowerShell:
# .\PowerShell_AES_Encryption_Example.ps1
# C:\Test\PowerShell_AES_Encryption_Example.ps1
# 
# In Command Prompt:
# powershell -noexit "& ""C:\Test\PowerShell_AES_Encryption_Example.ps1"""
#>

推荐答案

我发现我缺少一些东西，因为加密-在对iv（盐）和加密的数据进行加密和合并时创建一个随机IV（盐），以进行解密-根据加密的字符串创建IV（盐）并在末尾修剪零（因为I' m使用PaddingMode.Zeros）。在以下位置上也找到了一些有用的示例： mark-adams / aes_example.cs

I found out that I was missing few things, for the Encryption - create a random IV (salt) when encrypting and combining the iv (salt) and the encrypted data, for the decryption - create the IV (salt) based on the encrypted string and trim the zeros at the end (because I'm using PaddingMode.Zeros). Also found some useful examples on: mark-adams/aes_example.cs

现在它可以与PowerShell脚本创建的加密值一起使用，因此，我最终编写了一个包装器类，让我知道您是否发现任何错误或任何改进建议：

Now it works with encrypted values created by the PowerShell script, so, I ended up writing a wrapper class, let me know if you can find anything wrong or any suggestions for improvement:

测试代码

var keyString = "8CBaNtMYwAuu2K/xleoRfgPkURaLK82QidlIyg+nFY4=";
var keyBytes = Convert.FromBase64String(keyString);
var encryptedValue = "JW9CDowP0tRGr0Xi7vLxxXv0+fvMzQzopQucLOaeU7s=";

var testValue = AesWrapper.Decrypt(encryptedValue, keyBytes);
var testEncrypted = AesWrapper.Encrypt(@"Test String", keyBytes);
var testDecrypted = AesWrapper.Decrypt(testEncrypted, keyBytes);
var testReEncrypted = AesWrapper.Encrypt(testEncrypted, keyBytes);

AesWrapper

namespace Yovav.Security
{
    using System;
    using System.Diagnostics;
    using System.IO;
    using System.Security.Cryptography;

    /// <summary>
    /// AES wrapper implementation by Yovav Gad using the AesManaged algorithm.
    /// <para>http://en.wikipedia.org/wiki/Advanced_Encryption_Standard</para>
    /// </summary>
    public sealed class AesWrapper
    {
        /// <summary>
        /// Create a SymmetricAlgorithm using AesManaged
        /// </summary>
        /// <param name="key">Byte array representing the key values, please note, 
        /// for better performance, use Convert.FromBase64String() outside of this method.</param>
        /// <param name="blockSize">BlockSize, default is 128</param>
        /// <param name="paddingMode">PaddingMode, default is PaddingMode.Zeros</param>
        /// <param name="cipherMode">CipherMode, default is CipherMode.CBC</param>
        /// <returns></returns>
        private static SymmetricAlgorithm CreateCrypto(
            byte[] key, 
            int blockSize = 128,
            PaddingMode paddingMode = PaddingMode.Zeros,
            CipherMode cipherMode = CipherMode.CBC
            )
        {
            SymmetricAlgorithm crypto = new AesManaged
            {
                Key = key,
                Mode = cipherMode,
                Padding = paddingMode,
                BlockSize = blockSize
            };

            crypto.IV = new byte[crypto.IV.Length];

            return (crypto);
        }

        /// <summary>
        /// Decrypt an encrypted string using a specific key.
        /// </summary>
        /// <param name="str">String to decrypt</param>
        /// <param name="key">Byte array representing the key values, please note, 
        /// for better performance, use Convert.FromBase64String() outside of this method.</param>
        /// <param name="blockSize">BlockSize, default is 128</param>
        /// <param name="paddingMode">PaddingMode, default is PaddingMode.Zeros</param>
        /// <param name="cipherMode">CipherMode, default is CipherMode.CBC</param>
        /// <returns></returns>
        [DebuggerStepThrough()]
        public static string Decrypt(
            string str, 
            byte[] key,
            int blockSize = 128,
            PaddingMode paddingMode = PaddingMode.Zeros,
            CipherMode cipherMode = CipherMode.CBC
            )
        {
            if (str == null || str.Length < 1 ||
                key == null || key.Length < 1)
            {
                return null;
            }

            var result = string.Empty;

            using (var crypto = CreateCrypto(key, blockSize, paddingMode, cipherMode))
            {
                var strCombined = Convert.FromBase64String(str);
                var iv = new byte[crypto.BlockSize / 8];
                var cipherText = new byte[strCombined.Length - iv.Length];
                Array.Copy(strCombined, iv, iv.Length);
                Array.Copy(strCombined, iv.Length, cipherText, 0, cipherText.Length);

                crypto.IV = iv;
                ICryptoTransform decryptor = crypto.CreateDecryptor(key, iv);

                using (var msDecrypt = new MemoryStream(cipherText))
                {
                    using (var csDecrypt = new CryptoStream(msDecrypt, decryptor, CryptoStreamMode.Read))
                    {
                        using (var srDecrypt = new StreamReader(csDecrypt))
                        {
                            result = srDecrypt.ReadToEnd();
                        }
                    }
                }

                if (paddingMode == PaddingMode.Zeros)
                    {
                        // This is required when using PaddingMode.Zeros for values shorted than the block size.
                        // Note: using .TrimEnd('\0') to remove nulls and not .TrimEnd("\0") to allow the string values.
                        result = result.TrimEnd('\0');
                    }

                return (result);
            }
        }

        /// <summary>
        /// Encrypt a string using a specific key.
        /// </summary>
        /// <param name="str">String to encrypt</param>
        /// <param name="key">Byte array representing the key values, please note, 
        /// for better performance, use Convert.FromBase64String() outside of this method.</param>
        /// <param name="blockSize">BlockSize, default is 128</param>
        /// <param name="paddingMode">PaddingMode, default is PaddingMode.Zeros</param>
        /// <param name="cipherMode">CipherMode, default is CipherMode.CBC</param>
        /// <returns></returns>
        [DebuggerStepThrough()]
        public static string Encrypt(
            string str,
            byte[] key,
            int blockSize = 128,
            PaddingMode paddingMode = PaddingMode.Zeros,
            CipherMode cipherMode = CipherMode.CBC
            )
        {
            if (str == null || str.Length < 1 ||
                key == null || key.Length < 1)
            {
                return null;
            }

            byte[] encryptedData;

            using (SymmetricAlgorithm crypto = CreateCrypto(key, blockSize, paddingMode, cipherMode))
            {
                byte[] data;
                crypto.GenerateIV();
                var iv = crypto.IV;
                var encryptor = crypto.CreateEncryptor(key, iv);

                using (MemoryStream ms = new MemoryStream())
                {
                    using (CryptoStream cs = new CryptoStream(ms, encryptor, CryptoStreamMode.Write))
                    {
                        using (StreamWriter sw = new StreamWriter(cs))
                        {
                            sw.Write(str);
                        }

                        data = ms.ToArray();
                    }
                }

                // Combine the iv (salt) and the encrypted data
                encryptedData = new byte[iv.Length + data.Length];
                Array.Copy(iv, 0, encryptedData, 0, iv.Length);
                Array.Copy(data, 0, encryptedData, iv.Length, data.Length);
            }

            return Convert.ToBase64String(encryptedData);
        }
    }
}

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