加密.txt文件错误-进程无法访问文件 [英] Encrypting .txt File Erroring - Process Cannot Access File

问题描述

我正在尝试加密在应用程序中创建的 .txt 文件.

I'm trying to encrypt a .txt file which is created in my application.

要创建此文件，我使用以下代码:

To create this file, I'm using the following code:

Dim fileExists As Boolean = File.Exists(directorypath & "dbpw.txt")
If File.Exists(directorypath & "dbpw.txt") = False Then
   Using sw As New StreamWriter(File.Open(directorypath & "dbpw.txt", FileMode.Create))
         IIf(fileExists, "", "")
         sw.Close()
   End Using
End If

然后，要编写和加密文件，我使用以下代码，调用从Internet上的示例中调整的子例程.

Then, to write and encrypt the file, I'm using the following code, calling subroutines that I tweaked from examples on the internet.

bytKey = CreateKey(txtCode.Text)
bytIV = CreateIV(txtCode.Text)

EncryptOrDecryptFile(directorypath & "dbpw.txt", directorypath & "dbpw.txt", bytKey, bytIV, CryptoAction.ActionEncrypt)

当代码到达最后一行时，调用 EncryptOrDecrypt 子例程，则会引发错误提示

When the code gets to the final line, calling the EncryptOrDecrypt subroutine, an error is thrown saying

该进程无法访问文件'myDirectoryPath \ dbpw.txt'，因为该文件正在被另一个进程使用

The process cannot access the file 'myDirectoryPath\dbpw.txt' because it is being used by another process

我需要怎么做才能释放文件?

What do I need to do to release the file?

我也尝试只使用 File.Create 和 File.Encrypt ，但是无论哪种方式都抛出相同的错误.

I also tried just using File.Create along with File.Encrypt but the same error was thrown either way.

EncryptOrDecryptFile()

Public Sub EncryptOrDecryptFile(ByVal strInputFile As String, ByVal strOutputFile As String, ByVal bytKey() As Byte, ByVal bytIV() As Byte, ByVal Direction As CryptoAction)

    Try
        fsInput = New System.IO.FileStream(strInputFile, FileMode.Open, FileAccess.Read)
        fsOutput = New System.IO.FileStream(strOutputFile, FileMode.OpenOrCreate, FileAccess.Write)
        fsOutput.SetLength(0)
        ' Currently fails, file not being released for read/write once it's created.

        Dim bytBuffer(4096) As Byte
        Dim lngBytesProcessed As Long = 0
        Dim lngFileLength As Long = fsInput.Length
        Dim intBytesInCurrentBlock As Integer
        Dim csCryptoStream As CryptoStream

        Dim cspRijndael As New System.Security.Cryptography.RijndaelManaged

        Select Case Direction
            Case CryptoAction.ActionEncrypt
                csCryptoStream = New CryptoStream(fsOutput, _
                cspRijndael.CreateEncryptor(bytKey, bytIV), _
                CryptoStreamMode.Write)

            Case CryptoAction.ActionDecrypt
                csCryptoStream = New CryptoStream(fsOutput, _
                cspRijndael.CreateDecryptor(bytKey, bytIV), _
                CryptoStreamMode.Write)
        End Select

        While lngBytesProcessed < lngFileLength
            intBytesInCurrentBlock = fsInput.Read(bytBuffer, 0, 4096)

            csCryptoStream.Write(bytBuffer, 0, intBytesInCurrentBlock)

            lngBytesProcessed = lngBytesProcessed + _
                                    CLng(intBytesInCurrentBlock)
        End While

        csCryptoStream.Close()
        fsInput.Close()
        fsOutput.Close()

    Catch ex As Exception
        errorLog(ex)

    End Try
End Sub

推荐答案

连同您传递的参数一起，您要在 EncryptOrDecryptFile()方法中尝试打开两个流( fsInput和 fsOutput )复制到同一文件.打开 fsInput 后，它就具有对该文件的独占访问权限，这使得 fsOutput 无法打开该文件进行写入.

Together with the parameters you pass it, in your EncryptOrDecryptFile() method you are trying to open two streams (fsInput and fsOutput) to the same file. Once you've opened fsInput it has exclusive access to the file, making fsOutput unable to open it for writing.

您唯一的选择是:

• 重命名输入文件或输出文件，以便两个流打开两个不同的文件，或者:

• Rename either the input file or the output file so that the two streams open two different files, or:

对文件保持全局"加密流，您每次要向其写入数据时都会使用该加密流.

Keep a "global" encryption stream open to the file, which you use every time you want to write data to it.

注意::将来有人可能会建议您使用 FileShare.Write 打开 fsInput ，以便允许其他进程打开文件.用于写入，因此也允许 fsOutput 流也对其进行写入.-不要这样做！

NOTE: Someone in the future might suggest that you open fsInput with FileShare.Write in order to allow other processes to open the file for writing, thus also allowing the fsOutput stream to write to it as well. - DON'T DO THAT!

即使您是 fsOutput 流，在读取文件时允许其他进程写入该文件也可能会导致问题.这是因为您永远无法知道多少数据 fsOutput 将要写入.如果加密数据 比原始数据长 怎么办?这将导致它覆盖 fsInput 接下来要读取的内容，从而损坏文件.

Allowing other processes to write to the file while you're reading from it can cause problems, even if it's your fsOutput stream. This is because you'll never be able to know how much data fsOutput is going to write. What if the encrypted data is longer than the original? That would result in it overwriting what fsInput is going to read next, thus corrupting the file.

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