c# - .NET 文件解密 - 错误数据

Question

我正在重写一个旧的应用程序。旧应用程序将数据存储在使用以下代码加密的记分板文件中:

private const String SSecretKey = @"?B?n?Mj?";
public DataTable GetScoreboardFromFile()
{
    FileInfo f = new FileInfo(scoreBoardLocation);
    if (!f.Exists)
    {
        return setupNewScoreBoard();
    }

    DESCryptoServiceProvider DES = new DESCryptoServiceProvider();
    //A 64 bit key and IV is required for this provider.
    //Set secret key For DES algorithm.
    DES.Key = ASCIIEncoding.ASCII.GetBytes(SSecretKey);
    //Set initialization vector.
    DES.IV = ASCIIEncoding.ASCII.GetBytes(SSecretKey);

    //Create a file stream to read the encrypted file back.
    FileStream fsread = new FileStream(scoreBoardLocation, FileMode.Open, FileAccess.Read);
    //Create a DES decryptor from the DES instance.
    ICryptoTransform desdecrypt = DES.CreateDecryptor();
    //Create crypto stream set to read and do a 
    //DES decryption transform on incoming bytes.
    CryptoStream cryptostreamDecr = new CryptoStream(fsread, desdecrypt, CryptoStreamMode.Read);

    DataTable dTable = new DataTable("scoreboard");
    dTable.ReadXml(new StreamReader(cryptostreamDecr));

    cryptostreamDecr.Close();
    fsread.Close();

    return dTable;
}

这很好用。我已将代码复制到新应用程序中，以便我可以创建旧加载程序并将数据转换为新格式。问题是我收到“错误数据”错误:

System.Security.Cryptography.CryptographicException 未处理 消息=“错误数据。\r\n” 来源=“mscorlib”

此行触发错误:

dTable.ReadXml(new StreamReader(cryptostreamDecr));

今天使用旧代码在同一台计算机上创建了加密文件。我想加密/解密过程可能使用应用程序名称/文件或其他内容，因此意味着我无法打开它。

有人有这样的想法吗:

A)能够解释为什么这不起作用吗？ B) 请提供一个解决方案，使我能够打开使用旧应用程序创建的文件并能够转换它们？

这是处理加载和保存记分板的整个类:

using System;
using System.Collections.Generic;
using System.Text;
using System.Security.Cryptography;
using System.Runtime.InteropServices;
using System.IO;
using System.Data;
using System.Xml;
using System.Threading;

namespace JawBreaker
{
[Serializable]
class ScoreBoardLoader
{
    private Jawbreaker jawbreaker;
    private String sSecretKey = @"?B?n?Mj?";
    private String scoreBoardFileLocation = "";
    private bool keepScoreBoardUpdated = true;
    private int intTimer = 180000;

    public ScoreBoardLoader(Jawbreaker jawbreaker, String scoreBoardFileLocation)
    {
        this.jawbreaker = jawbreaker;
        this.scoreBoardFileLocation = scoreBoardFileLocation;
    }

    //  Call this function to remove the key from memory after use for security
    [System.Runtime.InteropServices.DllImport("KERNEL32.DLL", EntryPoint = "RtlZeroMemory")]
    public static extern bool ZeroMemory(IntPtr Destination, int Length);

    // Function to Generate a 64 bits Key.
    private string GenerateKey()
    {
        // Create an instance of Symetric Algorithm. Key and IV is generated automatically.
        DESCryptoServiceProvider desCrypto = (DESCryptoServiceProvider)DESCryptoServiceProvider.Create();

        // Use the Automatically generated key for Encryption. 
        return ASCIIEncoding.ASCII.GetString(desCrypto.Key);
    }

    public void writeScoreboardToFile()
    {
        DataTable tempScoreBoard = getScoreboardFromFile();
        //add in the new scores to the end of the file.
        for (int i = 0; i < jawbreaker.Scoreboard.Rows.Count; i++)
        {
            DataRow row = tempScoreBoard.NewRow();
            row.ItemArray = jawbreaker.Scoreboard.Rows[i].ItemArray;
            tempScoreBoard.Rows.Add(row);
        }

        //before it is written back to the file make sure we update the sync info
        if (jawbreaker.SyncScoreboard)
        {
            //connect to webservice, login and update all the scores that have not been synced.

            for (int i = 0; i < tempScoreBoard.Rows.Count; i++)
            {
                try
                {
                    //check to see if that row has been synced to the server
                    if (!Boolean.Parse(tempScoreBoard.Rows[i].ItemArray[7].ToString()))
                    {
                        //sync info to server

                        //update the row to say that it has been updated
                        object[] tempArray = tempScoreBoard.Rows[i].ItemArray;
                        tempArray[7] = true;
                        tempScoreBoard.Rows[i].ItemArray = tempArray;
                        tempScoreBoard.AcceptChanges();
                    }
                }
                catch (Exception ex)
                {
                    jawbreaker.writeErrorToLog("ERROR OCCURED DURING SYNC TO SERVER UPDATE: " + ex.Message);
                }
            }
        }

        FileStream fsEncrypted = new FileStream(scoreBoardFileLocation, FileMode.Create, FileAccess.Write);
        DESCryptoServiceProvider DES = new DESCryptoServiceProvider();
        DES.Key = ASCIIEncoding.ASCII.GetBytes(sSecretKey);
        DES.IV = ASCIIEncoding.ASCII.GetBytes(sSecretKey);
        ICryptoTransform desencrypt = DES.CreateEncryptor();
        CryptoStream cryptostream = new CryptoStream(fsEncrypted, desencrypt, CryptoStreamMode.Write);

        MemoryStream ms = new MemoryStream();
        tempScoreBoard.WriteXml(ms, XmlWriteMode.WriteSchema);

        ms.Position = 0;

        byte[] bitarray = new byte[ms.Length];
        ms.Read(bitarray, 0, bitarray.Length);

        cryptostream.Write(bitarray, 0, bitarray.Length);
        cryptostream.Close();
        ms.Close();

        //now the scores have been added to the file remove them from the datatable
        jawbreaker.Scoreboard.Rows.Clear();
    }

    public void startPeriodicScoreboardWriteToFile()
    {
        while (keepScoreBoardUpdated)
        {
            //three minute sleep.
            Thread.Sleep(intTimer);
            writeScoreboardToFile();
        }
    }

    public void stopPeriodicScoreboardWriteToFile()
    {
        keepScoreBoardUpdated = false;
    }

    public int IntTimer
    {
        get
        {
            return intTimer;
        }
        set
        {
            intTimer = value;
        }
    }

    public DataTable getScoreboardFromFile()
    {
        FileInfo f = new FileInfo(scoreBoardFileLocation);
        if (!f.Exists)
        {
            jawbreaker.writeInfoToLog("Scoreboard not there so creating new one");
            return setupNewScoreBoard();
        }
        else
        {
            DESCryptoServiceProvider DES = new DESCryptoServiceProvider();
            //A 64 bit key and IV is required for this provider.
            //Set secret key For DES algorithm.
            DES.Key = ASCIIEncoding.ASCII.GetBytes(sSecretKey);
            //Set initialization vector.
            DES.IV = ASCIIEncoding.ASCII.GetBytes(sSecretKey);

            //Create a file stream to read the encrypted file back.
            FileStream fsread = new FileStream(scoreBoardFileLocation, FileMode.Open, FileAccess.Read);
            //Create a DES decryptor from the DES instance.
            ICryptoTransform desdecrypt = DES.CreateDecryptor();
            //Create crypto stream set to read and do a 
            //DES decryption transform on incoming bytes.
            CryptoStream cryptostreamDecr = new CryptoStream(fsread, desdecrypt, CryptoStreamMode.Read);

            DataTable dTable = new DataTable("scoreboard");
            dTable.ReadXml(new StreamReader(cryptostreamDecr));

            cryptostreamDecr.Close();
            fsread.Close();

            return dTable;
        }
    }

    public DataTable setupNewScoreBoard()
    {
        //scoreboard info into dataset
        DataTable scoreboard = new DataTable("scoreboard");
        scoreboard.Columns.Add(new DataColumn("playername", System.Type.GetType("System.String")));
        scoreboard.Columns.Add(new DataColumn("score", System.Type.GetType("System.Int32")));
        scoreboard.Columns.Add(new DataColumn("ballnumber", System.Type.GetType("System.Int32")));
        scoreboard.Columns.Add(new DataColumn("xsize", System.Type.GetType("System.Int32")));
        scoreboard.Columns.Add(new DataColumn("ysize", System.Type.GetType("System.Int32")));
        scoreboard.Columns.Add(new DataColumn("gametype", System.Type.GetType("System.String")));
        scoreboard.Columns.Add(new DataColumn("date", System.Type.GetType("System.DateTime")));
        scoreboard.Columns.Add(new DataColumn("synced", System.Type.GetType("System.Boolean")));

        scoreboard.AcceptChanges();
        return scoreboard;
    }

    private void Run()
    {
        // For additional security Pin the key.
        GCHandle gch = GCHandle.Alloc(sSecretKey, GCHandleType.Pinned);

        // Remove the Key from memory. 
        ZeroMemory(gch.AddrOfPinnedObject(), sSecretKey.Length * 2);
        gch.Free();
    }
}
}

Answer 1

这看起来像是解密文件并从中反序列化记分板对象的代码。我们确实需要查看原始加密方面进行比较(如果您可以发布的话)。

我从解密代码中得到两个观察结果:

• 将 IV 设置为与 key 相同的方式看起来不太正确(但如果您的加密代码就是这么做的，则可能是正确的)
• 这些真的是 SSecretKey 中的问号吗？它们是否可能是控制字符或高字节集字符，导致错误编码和/或粘贴错误？

已添加:感谢您的更新。一些谷歌搜索表明，坏数据通常是由解密的数据不完全是加密输出的数据引起的，这是一个需要关注的地方(但请继续检查 key 字符串是否正确)。我必须承认我对 C# 的了解有点不够深入，所以以下只是建议:

• 在 writeScoreboardToFile 中，您将 XML 写入 MemoryStream，然后将该流的内容写入 CryptoStream。有什么理由不直接写入 CryptoStream 吗？
• 直接设置ms.Position是否合法？ ms.Seek(0,SeekOrigin.Begin) 有什么区别吗？
• 您可能需要在关闭之前调用 cryptostream.FlushFinalBlock()，MSDN 上并不清楚它是否会自动调用。
• 加密数据是二进制的，您可能需要使用 BinaryReader 和 BinaryWriter 来避免它被编码破坏，正如 Chris 指出的那样。
• Run() 到底什么时候被调用？如果我理解正确的话，那就是将 key 字符串归零 - 显然您不希望在完成创建加密转换之前发生这种情况。

除此之外，我想说的是，将 IV 设置为等于 key 在密码学上并不是很合理；每次使用一个 key 加密时，IV 确实应该不同。