Implementing Secure User Authentication in VBA with Token Expiration Management
I'm reviewing some code and Currently developing a local application in Excel using VBA that requires secure user authentication. The aim is to implement a system where users can log in and have their session managed with token expiration. My plan involves generating a unique token upon successful login and storing it temporarily in a hidden worksheet to track session activity. I've set up a basic user interface where users input their credentials and a button to trigger the authentication process. Here’s a snippet of the login function I've implemented: ```vba Sub UserLogin() Dim username As String Dim password As String Dim token As String username = Sheets("Login").Cells(2, 1).Value password = Sheets("Login").Cells(2, 2).Value If AuthenticateUser(username, password) Then token = CreateToken(username) StoreToken token MsgBox "Login successful! Token: " & token Else MsgBox "Invalid credentials!" End If End Sub ``` The `AuthenticateUser` function verifies credentials against stored values, while `CreateToken` generates a random token. However, I haven't yet implemented the logic for token expiration, which I believe is crucial for security. Here's a draft of the `CreateToken` function: ```vba Function CreateToken(user As String) As String Dim token As String token = user & "_" & Format(Now, "YYYYMMDDHHMMSS") ' Add additional encoding or hashing as needed CreateToken = token End Function ``` For token expiration, I’m thinking about setting a timer to invalidate the token after a specified duration, such as 30 minutes. However, I'm unsure how to best implement this in a way that aligns with VBA’s capabilities. I have considered using a background process or a hidden worksheet to track login timestamps but I’m open to better approaches. Additionally, should I incorporate more encryption for the stored tokens? Any examples or guidance related to session management in VBA that ensures security and efficiency would be greatly appreciated. Is there a simpler solution I'm overlooking? Am I approaching this the right way?