Cryptostream troubles

[kettch]

I am trying to decrypt an xmldocument object from a memory stream:

        Dim rm As New RijndaelManaged()
        rm.Key = rsa.Decrypt(symmetricKey, False)
        rm.IV = rsa.Decrypt(symmetricIV, False)
        'Dim doc As Byte()
        Dim cryptDoc As Byte() = My.Computer.FileSystem.ReadAllBytes("c:\temp\encryptedxmlbytestream")
        Dim ms As New MemoryStream
        For Each b As Byte In cryptDoc
            ms.WriteByte(b)
        Next
        'ms.Flush()

        Dim CryptStream As New CryptoStream(ms, rm.CreateDecryptor(rm.Key, rm.IV), CryptoStreamMode.Read)
        Dim settings As New XmlReaderSettings
        Dim reader As XmlReader = XmlReader.Create(CryptStream)

        Dim decryptedXML As New XmlDocument
        decryptedXML.LoadXml(reader.ReadOuterXml)

the problem is that when it gets to the XmlReader.Create line, it throws an indexoutofrangeexception. Here is the stack trace:

   at System.Security.Cryptography.RijndaelManagedTransform.DecryptData(Byte[] inputBuffer, Int32 inputOffset, Int32 inputCount, Byte[]& outputBuffer, Int32 outputOffset, PaddingMode paddingMode, Boolean fLast)
   at System.Security.Cryptography.RijndaelManagedTransform.TransformFinalBlock(Byte[] inputBuffer, Int32 inputOffset, Int32 inputCount)
   at System.Security.Cryptography.CryptoStream.Read(Byte[] buffer, Int32 offset, Int32 count)
   at System.Xml.XmlTextReaderImpl.InitStreamInput(Uri baseUri, String baseUriStr, Stream stream, Byte[] bytes, Int32 byteCount, Encoding encoding)
   at System.Xml.XmlTextReaderImpl..ctor(Stream stream, Byte[] bytes, Int32 byteCount, XmlReaderSettings settings, Uri baseUri, String baseUriStr, XmlParserContext context, Boolean closeInput)
   at System.Xml.XmlReader.CreateReaderImpl(Stream input, XmlReaderSettings settings, Uri baseUri, String baseUriStr, XmlParserContext inputContext, Boolean closeInput)
   at System.Xml.XmlReader.Create(Stream input)
   at ProductActivation.Form1.btnDecrypt_Click(Object sender, EventArgs e) in C:\Software Projects\ProductActivation\ProductActivation\Form1.vb:line 164
   at System.Windows.Forms.Control.OnClick(EventArgs e)
   at System.Windows.Forms.Button.OnClick(EventArgs e)
   at System.Windows.Forms.Button.OnMouseUp(MouseEventArgs mevent)
   at System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks)
   at System.Windows.Forms.Control.WndProc(Message& m)
   at System.Windows.Forms.ButtonBase.WndProc(Message& m)
   at System.Windows.Forms.Button.WndProc(Message& m)
   at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
   at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
   at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
   at System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg)
   at System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(Int32 dwComponentID, Int32 reason, Int32 pvLoopData)
   at System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context)
   at System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context)
   at System.Windows.Forms.Application.Run(ApplicationContext context)
   at Microsoft.VisualBasic.ApplicationServices.WindowsFormsApplicationBase.OnRun()
   at Microsoft.VisualBasic.ApplicationServices.WindowsFormsApplicationBase.DoApplicationModel()
   at Microsoft.VisualBasic.ApplicationServices.WindowsFormsApplicationBase.Run(String[] commandLine)
   at ProductActivation.My.MyApplication.Main(String[] Args) in 17d14f5c-a337-4978-8281-53493378c1071.vb:line 81
   at System.AppDomain.nExecuteAssembly(Assembly assembly, String[] args)
   at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args)
   at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
   at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
   at System.Threading.ThreadHelper.ThreadStart()

I'm new to the crypto libraries, so I'm sure I've got something boogered up.

Thanks for any help.

 

[tperri]

try this


StreamReader sr = new StreamReader(CryptoStream);

then read the StreamReader into an XMLDoc

 

[kettch]

I rearranged it to look like this:

        Dim rsa As New RSACryptoServiceProvider()
        rsa.ImportParameters(privateKey)

        Dim rm As New RijndaelManaged()
        rm.Key = rsa.Decrypt(symmetricKey, False)
        rm.IV = rsa.Decrypt(symmetricIV, False)
        Dim cryptDoc As Byte() = My.Computer.FileSystem.ReadAllBytes("c:\temp\cryptedDoc")
    
        Dim ms As New MemoryStream
        ms.Write(cryptDoc, 0, cryptDoc.Length)
        ms.Position = 0

        Dim CryptStream As New CryptoStream(ms, rm.CreateDecryptor(rm.Key, rm.IV), CryptoStreamMode.Read)
       
               Dim reader As New StreamReader(CryptStream)
        txtDecryptedXML.Text = reader.ReadToEnd

It happens at the line with reader.readtoend
The stacktrace says that it's happening inside the cryptostream's decryption.

I've been working on this for a week and it's starting to get annoying. Every error i've been getting ends up with the only search results on google being my own posts in forums.

 

[tperri]

what is the error message you're getting on the ReadToEnd line now?

 

[kettch]

interesting, if I set the memorstream's position to 0 I get "Length of the data to decrypt is invalid" at the readtoend line. If I don't set it to 0 I get an IndexOutOfRangeException.

 

[tperri]

put a breakpoint on the line txtDecryptedXML.Text = reader.ReadToEnd and then see what the size of the CryptStream is

 

[kettch]

by size do you mean length? CryptoStreams don't support seeking which is required to get the length.

 

[tperri]

It does in VS 2005 ... my intellisense gives me Length and Seek....

 

[kettch]

Yes, they are supported by the base class, but it is overriden and disabled for the cryptostream.

 

[tperri]

I dunno what to tell you. Here is some code I use that works just fine.

    public static string DecryptCreditCardInfo(string strItem)
    {
        DESCryptoServiceProvider cryptoProvider = new DESCryptoServiceProvider();
        byte[] buffer = Convert.FromBase64String(strItem);
        MemoryStream ms = new MemoryStream(buffer);
        CryptoStream cs = new CryptoStream(ms, cryptoProvider.CreateDecryptor(KEY_64, IV_64), CryptoStreamMode.Read);
        StreamReader sr = new StreamReader(cs);
        return sr.ReadToEnd();

    }