Visual Basic

Re: Changing Assembly Properties through Reflection

14-Nov-12 9:38

Is it possible to change an external assembly's property using reflection; specifically the GUID? The reason I'm trying to do this is for when a customer logs into my website and purchases a plug-in for the application. The server would then change the GUID within the plug-in's DLL and then allow the custom to download it. When they then go to install the plug-in, the application check the assembly's GUID to see if it matches what it's supposed to. This is part of the security system I have designed (within my head at the moment) to ensure that the assembly is allowed to be used, and can only be used by that specific person. So is there anyway to change the GUID of an assembly through reflection?

Thanks

Eddy Vluggen15-Nov-12 1:18

Eddy Vluggen

15-Nov-12 1:18

You can't make modifications using reflection; it's a read-only game. There are multiple ways to generate a new assembly; using the CompilerService[^] would be an option, but "modifying" an existing assembly would be easier using Mono's Cecil.

Bastard Programmer from Hell Suspicious | :suss:

If you can't read my code, try converting it here[^]
They hate us for our freedom![^]

Re: Changing Assembly Properties through Reflection

Dominick Marciano15-Nov-12 17:14

Re: Changing Assembly Properties through Reflection

15-Nov-12 17:14

So if I understand correctly, based on my quick read of the link you provided, with the Mono's Cecil I could open up an assembly that I created, modify the GUID assembly attribute, and then save it to a new file and server it to the customer for download?

Eddy Vluggen16-Nov-12 0:06

Eddy Vluggen

16-Nov-12 0:06

Yes

Bastard Programmer from Hell Suspicious | :suss:

If you can't read my code, try converting it here[^]
They hate us for our freedom![^]

messagebeep

Gil Goodridge14-Nov-12 8:00

Gil Goodridge

14-Nov-12 8:00

I am looking for an example of how to call MessageBeep in Visual Basic 8/net?

Re: messagebeep

Dave Kreskowiak14-Nov-12 8:31

Dave Kreskowiak

14-Nov-12 8:31

You can start with this[^].

And then move on to these[^].

Honestly, this was not very hard to find. You just Google for "MessageBeep VB.NET" and you come up with all kinds of examples.

A guide to posting questions on CodeProject[^]

Dave Kreskowiak

Rijndael encryption not working

maskrtnik0114-Nov-12 2:20

14-Nov-12 2:20

Hi,

I am working on program to be used to process confidential data. That data must be well-encrypted. I have built method, that exports data from memory to XML, encrypts XMl document and saves it to file. But, what seems strange to me is, that encryption method doesn’t work. After its execution, file, which may contain encrypted data is created, but remains empty. I don’ t see any bug in the code. Could you help me to get it working, please?

Here is code used to encrypt and save XML.

Public Sub Save(ByVal carrier As DataCarrier, ByVal password As String, ByVal filename As String)
            Try
                Using sha As New SHA512Managed
                    Dim salt As Byte() = sha.ComputeHash(Encoding.Default.GetBytes(password))
                    Using pdb As New Rfc2898DeriveBytes(password, salt), aes As New RijndaelManaged, filestr As New FileStream(filename, FileMode.Create, FileAccess.Write)
                        Using cryptostr As New CryptoStream(filestr, aes.CreateEncryptor(pdb.GetBytes(32), pdb.GetBytes(16)), CryptoStreamMode.Write)
                            ExportData(carrier).Save(cryptostr)
                        End Using
                    End Using
                End Using
            Catch ex As Exception
                Logging.Instance.WriteException(ex, TraceEventType.Error)
                MessageBox.Show(String.Format(My.Resources.UnhandledExceptionExString, ex.Message, ex.ToString), My.Application.Info.Title, MessageBoxButtons.OK, MessageBoxIcon.Error)
            End Try
        End Sub

Also, is that encryption algorithm OK, or there is some way to break it? I must be sure that there is no way to break encryption, that is used.

Stanislav Husár

Keith Barrow14-Nov-12 2:52

14-Nov-12 2:52

Have you tried putting a breakpoint to see if an Exception is thrown?

After a brief glance, the code itself looks fine AFAICT, though the problem could be in the ExportData method, is there a reason you aren't calling the cryptostream's Write directly?

My knowledge about this is four years out of date, but Rijndael was considered secure. I vaguely recall reading they'd found a way to crack it in theory, but applying the crack it in practise hasn't happened yet and isn't likely to be feasible soon.

Sort of a cross between Lawrence of Arabia and Dilbert.[^]
-Or-
A Dead ringer for Kate Winslett[^]

maskrtnik0114-Nov-12 3:08

14-Nov-12 3:08

It does not throw any exception.

ExportData method only creates XML document with data to be encrypted. I have checked, that result of ExportData contains, what it should cotain.

I have also tried following, again, empty file is generated.

Public Sub Save(ByVal carrier As DataCarrier, ByVal password As String, ByVal filename As String)
            Try
                Using sha As New SHA512Managed
                    Dim salt As Byte() = sha.ComputeHash(Encoding.Default.GetBytes(password))
                    Using pdb As New Rfc2898DeriveBytes(password, salt), aes As New RijndaelManaged, filestr As New FileStream(filename, FileMode.Create, FileAccess.Write)
                        Using cryptostr As New CryptoStream(filestr, aes.CreateEncryptor(pdb.GetBytes(32), pdb.GetBytes(16)), CryptoStreamMode.Write)
                            Dim str = ExportData(carrier).ToString()
                            Using w As New StreamWriter(cryptostr)
                                w.Write(str)
                            End Using
                        End Using
                    End Using
                End Using
            Catch ex As Exception
                Logging.Instance.WriteException(ex, TraceEventType.Error)
                MessageBox.Show(String.Format(My.Resources.UnhandledExceptionExString, ex.Message, ex.ToString), My.Application.Info.Title, MessageBoxButtons.OK, MessageBoxIcon.Error)
            End Try
        End Sub

Moreover, I have tried simply writing string literal to CryptoStream, this approach generates empty file too.

Strange is, that when I run this version:

Public Sub Save(ByVal carrier As DataCarrier, ByVal password As String, ByVal filename As String)
           Try
               Using sha As New SHA512Managed
                   Dim salt As Byte() = sha.ComputeHash(Encoding.Default.GetBytes(password))
                   Using pdb As New Rfc2898DeriveBytes(password, salt), aes As New RijndaelManaged, filestr As New MemoryStream() 'filestr As New FileStream(filename, FileMode.Create, FileAccess.Write)
                       Using cryptostr As New CryptoStream(filestr, aes.CreateEncryptor(pdb.GetBytes(32), pdb.GetBytes(16)), CryptoStreamMode.Write)
                           ExportData(carrier).Save(cryptostr)
                           Dim str = New String(Encoding.Default.GetChars(filestr.ToArray()))
                           Debugger.Break()
                       End Using
                   End Using
               End Using
           Catch ex As Exception
               Logging.Instance.WriteException(ex, TraceEventType.Error)
               MessageBox.Show(String.Format(My.Resources.UnhandledExceptionExString, ex.Message, ex.ToString), My.Application.Info.Title, MessageBoxButtons.OK, MessageBoxIcon.Error)
           End Try
       End Sub

Then at Debugger.Break statement str variable cotains data, which should be in the file.

While this and simmilar solutions generate empty file.

Public Sub Save(ByVal carrier As DataCarrier, ByVal password As String, ByVal filename As String)
            Try
                Using sha As New SHA512Managed
                    Dim salt As Byte() = sha.ComputeHash(Encoding.Default.GetBytes(password))
                    Using pdb As New Rfc2898DeriveBytes(password, salt), aes As New RijndaelManaged, filestr As New MemoryStream() 'filestr As New FileStream(filename, FileMode.Create, FileAccess.Write)
                        Using cryptostr As New CryptoStream(filestr, aes.CreateEncryptor(pdb.GetBytes(32), pdb.GetBytes(16)), CryptoStreamMode.Write)
                            ExportData(carrier).Save(cryptostr)
                            File.WriteAllBytes(filename, filestr.ToArray())
                            Debugger.Break()
                        End Using
                    End Using
                End Using
            Catch ex As Exception
                Logging.Instance.WriteException(ex, TraceEventType.Error)
                MessageBox.Show(String.Format(My.Resources.UnhandledExceptionExString, ex.Message, ex.ToString), My.Application.Info.Title, MessageBoxButtons.OK, MessageBoxIcon.Error)
            End Try
        End Sub

I am really confused on what it does.

Keith Barrow14-Nov-12 3:26

14-Nov-12 3:26

I'm not surprised at your confusion. The only thing I can suggest is to simplify as far as possible and re-factor back to what you want.

Comment out the export line and perform the crypto-stream write directly.
Create two byte arrays for the key and IV and make sure pdb is creating a sensible key & IV, I would have thought that the if these were incorrect the encryption algorithm would throw. I've not used the derived bytes thing, so it is new to me
If the above isn't working, hard-code the key and IV byte arrays

If all else fails, you could go back to square one, and write a console app that uses hard-coded byte arrays.

Sort of a cross between Lawrence of Arabia and Dilbert.[^]
-Or-
A Dead ringer for Kate Winslett[^]

Keith Barrow14-Nov-12 3:35

14-Nov-12 3:35

I think I may have figured it out!

The cryptostream writes to a filestream. The XML can't write to the same stream, and if you use a different stream you'll either overwrite (this is probably your situation) or it'll append the XML after the encrypted information. The other option is the XML is written first, then appended or overwitten with the encrypted information, neith seems to apply in your case.

In your position I'd replace the file stream with a memory stream for the cryptography stuff. I'd perform the write immediately, reset the position to 0 and pass the memory stream into the Export method. Then all the XML writer has to do is to read the Memory stream into the file stream when you've reached the correct point in the file (or set a property to its contents).

The other problem you might face is that you need to encode the encrypted bytes (e.g. into Hex characters), otherwise you'll get non-printing characters in the XML document, fouling it up.

Sort of a cross between Lawrence of Arabia and Dilbert.[^]
-Or-
A Dead ringer for Kate Winslett[^]

maskrtnik0114-Nov-12 3:48

14-Nov-12 3:48

Hmm, now it works, even with using the same code as the one that didn´t work.I di d nothing more, than copying binaries from bin/Debug/ and running them on another computer. I can´t understand this behaviour.

Keith Barrow14-Nov-12 4:05

14-Nov-12 4:05

I think that is properly called a heisenbug[^].

That is odd behaviour. Something to do with a 64/32 bit compilation on a 32/64 bit machine Unsure | :~

(I mean really unsure)! The only other things that spring to mind immediately is the framework version or that restarting your machine might be a good idea, in case VS has screwed up. Hope you get it stable.

Sort of a cross between Lawrence of Arabia and Dilbert.[^]
-Or-
A Dead ringer for Kate Winslett[^]

maskrtnik0115-Nov-12 19:40

15-Nov-12 19:40

Maybe it is stable now. But there is new problem. I have tried decrypting encrypted file, but it fails to decrypt, decrypted data absolutely do not match data which was encrypted. I am using this code:

Public Sub Save(ByVal carrier As DataCarrier, ByVal password As String, ByVal filename As String)
        Try
            Using sha As New SHA512Managed
                Dim hash = sha.ComputeHash(Encoding.Default.GetBytes(password))
                Dim key As Byte() = New Byte(31) {}
                Dim iv As Byte() = New Byte(15) {}
                Array.Copy(hash, 0, key, 0, 32)
                Array.Copy(hash, 32, iv, 0, 16)
                Using aes As New RijndaelManaged, filestr As New FileStream(filename, FileMode.Create, FileAccess.Write)
                    Using cryptostr As New CryptoStream(filestr, aes.CreateEncryptor(key, iv), CryptoStreamMode.Write)
                        ExportData(carrier).Save(cryptostr)
                    End Using
                End Using
            End Using
        Catch ex As Exception
            Logging.Instance.WriteException(ex, TraceEventType.Error)
            MessageBox.Show(String.Format(My.Resources.UnhandledExceptionExString, ex.Message, ex.ToString), My.Application.Info.Title, MessageBoxButtons.OK, MessageBoxIcon.Error)
        End Try
    End Sub
    Public Function Load(ByVal password As String, ByVal filename As String) As XDocument
        Dim sha As SHA512Managed
        Dim aes As RijndaelManaged
        Dim trans As ICryptoTransform
        Dim cryptostr As CryptoStream
        Dim filestr As FileStream
        Try
            sha = New SHA512Managed()
            Dim hash = sha.ComputeHash(Encoding.Default.GetBytes(password))
            aes = New RijndaelManaged()
            Dim key As Byte() = New Byte(31) {}
            Dim iv As Byte() = New Byte(15) {}
            Array.Copy(hash, 0, key, 0, 32)
            Array.Copy(hash, 32, iv, 0, 16)
            trans = aes.CreateEncryptor(key, iv)
            filestr = New FileStream(filename, FileMode.Open)
            cryptostr = New CryptoStream(filestr, trans, CryptoStreamMode.Read)
            Return XDocument.Load(cryptostr)
        Catch ex As Exception
            Logging.Instance.WriteException(ex, TraceEventType.Error)
            MessageBox.Show(String.Format(My.Resources.UnhandledExceptionExString, ex.Message, ex.ToString), My.Application.Info.Title, MessageBoxButtons.OK, MessageBoxIcon.Error)
        Finally
            If cryptostr IsNot Nothing Then cryptostr.Dispose()
            If filestr IsNot Nothing Then filestr.Dispose()
            If trans IsNot Nothing Then trans.Dispose()
            If aes IsNot Nothing Then aes.Dispose()
            If sha IsNot Nothing Then sha.Dispose()
        End Try
    End Function

modified 17-Nov-12 11:23am.

Dominick Marciano14-Nov-12 9:34

14-Nov-12 9:34

Can you post the code for the Export.Save method so we can see how you are using the cryptostream?

maskrtnik0114-Nov-12 18:21

14-Nov-12 18:21

Do you mean ExportData(carrier).Save(cryptostr) ? That is System.Xml.Linq.Save method.

Dominick Marciano15-Nov-12 17:37

15-Nov-12 17:37

I've never tried encrypting something exactly as you are trying, but I believe the problem is that you're not calling the write method of the crypto stream. Check out the information on the write method of the crypto stream for for information. Below is a function I use to encrypt a string. As you can see I call the write method of the crypto stream and pass in a byte array of the data I want to encrypt. Hopefully the code below helps you.

Public Shared Function Encrypt(value As String, key() As Byte, iv() As Byte) As string
    Dim bytValue() As Byte      'The data to be encrypted
    Dim bytEncoded() As Byte    'The data after encryption
    Dim rijndael As New Rijndael Managed
    Dim ms As New MemoryStream  'The stream to write the encrypted data to
    
    bytValue = Encoding.ASCII.GetBytes(value.ToCharArray)   'Convert plain text to byte array
    'Create the crypto stream with the stream to write the encrypted data to (ms = Memory Stream)
    Using CryptoStream As New CryptoStream(ms, rijnadel.CreateEncryptor(key, iv), CryptoStreamMode.Write)
        'Encrypt the plaint text byte array (bytValue) to the memory stream (ms)
        CryptoStream.Write(bytValue, 0, bytValue.Length)
        'Flush crypto stream
        CryptoStream.FlushFinalBlock()
        'Get the encrypted byte array from the memory stream (ms)
        bytEncoded = ms.ToArray
        'Close memory stream
        ms.Close()
    End Using
    
    'Convert the encrypted byte array (bytEncoded) to a Base64 string and return it
    Return Convert.ToBase64String(bytEncoded)
End Function

maskrtnik0115-Nov-12 19:37