decrypt file being downloaded from azure [Answered]RSS

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  E.RU

  Member

  44 Points

  155 Posts

  decrypt file being downloaded from azure

  Feb 24, 2020 08:41 AM|E.RU|LINK

  I have tried the following code below to decrypt my file which is being downloaded from azure. Unfortunatly the decrypt code is not working fully as it decrypts a file from local files not straight from azure therefore the path of the file is not correct. how would I go about changing my decrypt code to work for this situation?

  any help on this would be great!

  many thanks

      '--DOWNLOAD FROM AZURE 
      Protected Sub DwnLd_Click(ByVal sender As Object, ByVal e As EventArgs)
  ")
  
          '--get id in gridview row
          Dim lb As LinkButton = CType(sender, LinkButton)
          Dim row As GridViewRow = CType(lb.NamingContainer, GridViewRow)
  
          If row IsNot Nothing Then
              Dim index As Integer = row.RowIndex
  
              If index <> -1 Then
  
                  Dim id = GridView1.DataKeys(index).Values(0).ToString()
  
                  Dim path2 = "file\path\" & id.ToString
  
                  Dim StorageConnStr As String = "xxxxxxxxxxxxxx"
                  Dim containerName = "xxxxxxxxxxxx"
                  Dim BlobstorageConnection As String = CloudConfigurationManager.GetSetting(StorageConnStr)
                  Dim MycloudStorageAccount As CloudStorageAccount = CloudStorageAccount.Parse(StorageConnStr)
                  Dim MyblobClient As CloudBlobClient = MycloudStorageAccount.CreateCloudBlobClient()
                  Dim MycloudBlobContainer As CloudBlobContainer = MyblobClient.GetContainerReference(containerName)
                  Dim MYblockBlob As CloudBlockBlob = MycloudBlobContainer.GetBlockBlobReference(path2)
  
                  '--Decrypt file here before download 
  
                  'Build the File Path for the original (input) and the decrypted (output) file  
                  Dim input As String = path2
                  Dim output As String = path2 & "_dec"
  
                  'Save the Input File, Decrypt it and save the decrypted file in output path.  
                  MsgBox(output.ToString)
  
  
                  Me.Decrypt(input, output)
  
                  'Dim newMYblockBlob As CloudBlockBlob = MycloudBlobContainer.GetBlockBlobReference(output)
  
  
  
                  Dim memStream As MemoryStream = New MemoryStream()
                  MYblockBlob.DownloadToStream(memStream)
                  HttpContext.Current.Response.ContentType = MYblockBlob.Properties.ContentType.ToString()
                  HttpContext.Current.Response.AddHeader("Content-Disposition", "Attachment; filename=" & MYblockBlob.ToString())
                  HttpContext.Current.Response.AddHeader("Content-Length", MYblockBlob.Properties.Length.ToString())
                  HttpContext.Current.Response.BinaryWrite(memStream.ToArray())
                  HttpContext.Current.Response.Flush()
                  HttpContext.Current.Response.Close()
  
                  Response.Redirect("~/")
  
              End If
          End If
  
      End Sub
  
      '----------Decrypt----------
      Private Sub Decrypt(inputFilePath As String, outputfilePath As String)
          Dim EncryptionKey As String = ConfigurationManager.AppSettings("Encrypt")
          Using encryptor As Aes = Aes.Create()
              Dim pdb As New Rfc2898DeriveBytes(EncryptionKey, New Byte() {&H49, &H76, &H61, &H6E, &H20, &H4D, &H65, &H64, &H76, &H65, &H64, &H65, &H76})
              encryptor.Key = pdb.GetBytes(32)
              encryptor.IV = pdb.GetBytes(16)
              Using fs As New FileStream(inputFilePath, FileMode.Open)
                  Using cs As New CryptoStream(fs, encryptor.CreateDecryptor(), CryptoStreamMode.Read)
                      Using fsOutput As New FileStream(outputfilePath, FileMode.Create)
                          Dim data As Integer
                          While (Assign(data, cs.ReadByte())) <> -1
                              fsOutput.WriteByte(CByte(data))
                          End While
                      End Using
                  End Using
              End Using
          End Using
  
      End Sub
  

• • Reply
  Brando ZWZ

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  9791 Points

  3119 Posts

  Re: decrypt file being downloaded from azure

  Feb 25, 2020 02:45 AM|Brando ZWZ|LINK

  Hi E.RU ,

  As far as I know, we couldn't use azure blob path to decript the file.  We need firstly download it and then decript it. 

  The right way is you directly download the file to a path and then use that path instead of azure blob file path directly.

  Best Regards,

  Brando

  MSDN Community Support
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• • Reply
  E.RU

  Member

  44 Points

  155 Posts

  Re: decrypt file being downloaded from azure

  Feb 25, 2020 08:38 AM|E.RU|LINK

  Hi Brando

  Thank you For your help, I will try this method. How should I code this ? I have code that downloads the encrypted file from azure but how should I go about saving the enc file to a (temp local)path ?

  Many thanks