A Login in VB.NET using Drupal Credentials June 28, 2008
Posted by tuse in : Tips and Tricks, VB.NET , add a commentThis is an interesting post in which we see the integration of the open-source technology Drupal with Microsoft .NET.
What we have already is a ‘users’ table made by Drupal. Drupal is a popular Content Management System. Whenever a user is created in a website made using Drupal, the username and password details are stored in the ‘users’ table. This password is encrypted using the MD5 algorithm and then stored in the database.
In a VB.NET application (we could as well have made a ASP.NET webpage) what we will try to do is create a login system in which the user credentials are checked against the Drupal created ‘users’ table.
In our Login form, we would need 2 Labels, 2 Textboxes, a Button and an ErrorProvider Control (We will talk about this soon). The first Tetbox is meant for the user to enter the username and the second one is meant for the password. The ErrorProvider is used to display an error message for an unsuccessful attempt at login. Once the username and password are entered, the login Button will be clicked, so we need to code the program logic in the ‘Button_Click’ event.
However, the catch here is that the password entered into the second Textbox needs to be first encrypted into its MD5 hash code before checking it against the value in the database. To accomplish this, we make use of the Function named MD5 in the code.
To check whether the value is present, we have used a DataReader object to read through the records as specified by the SQL Command Object. Note the manner in which the SQL Command is constructed. It may look to be a bit complicated at the moment, but once we tell you about connecting to databases, you will get a hold on it. The connection string that was talked about in a previous post makes an appearence here.
The code for our ‘Login’ form is as follows-
Imports System.Text
Imports System.Security.Cryptography
'This is a comment. (In case you are seeing this for the first time!)
Public Class Login
'Function to compute MD5 for a string
Public Function MD5(ByVal number As String) As String
'Create an encoding object to ensure the encoding standard for the source text
Dim ASCIIenc As New ASCIIEncoding
Dim strReturn
'Retrieve a byte array based on the source text
Dim ByteSourceText() As Byte = ASCIIenc.GetBytes(number)
'Instantiate an MD5 Provider object
Dim Md5Hash As New MD5CryptoServiceProvider
'Compute the hash value from the source
Dim ByteHash() As Byte = Md5Hash.ComputeHash(ByteSourceText)
'Cycle through the hash and convert to string
For Each b As Byte In ByteHash
'Convert byte(s) to string
strReturn &= b.ToString("x2")
Next
'Return the result
Return strReturn
End Function
Dim cn As New Odbc.OdbcConnection("Driver={MySQL ODBC 3.51 Driver};Server=localhost;Database=mydrupaldb; User=root;Password=;")
Private Sub login_FormClosing(ByVal sender As Object, ByVal e As System.Windows.Forms.FormClosingEventArgs) Handles Me.FormClosing
cn.Close()
End Sub
Private Sub login_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
cn.Open()
Me.Button1.Enabled = False
End Sub
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
'Define the SQL Command to retrieve records from the database
Dim cmd As New Odbc.OdbcCommand("select * from users where name=? and pass=?", cn)
cmd.Parameters.Add("@name", Odbc.OdbcType.VarChar, 60)
cmd.Parameters("@name").Value = Me.TextBox1.Text
Dim a, b As String
a = Me.TextBox2.Text
b = MD5(a)
'MD5 hash code for the password string is now held in variable b
cmd.Parameters.Add("@pass", Odbc.OdbcType.VarChar, 32)
cmd.Parameters("@pass").Value = b
'We have a Data Reader to read the values returned by the SQL Command Execution
Dim dr As Odbc.OdbcDataReader
dr = cmd.ExecuteReader
'Check if username and password exist.
If dr.HasRows = True Then
'If exists, then we show the next form which contains the application, in my case its Form1
Form1.Show()
Else
' Incorrect Login Details Supplied
Me.ErrorProvider1.SetError(Me.Button1, "Incorrect Login...Try again")
Me.TextBox1.Clear()
Me.TextBox2.Clear()
Me.Button1.Enabled = False
End If
End Sub
Private Sub TextBox2_LostFocus(ByVal sender As Object, ByVal e As System.EventArgs) Handles TextBox2.LostFocus
Me.Button1.Enabled = True
Me.ErrorProvider1.Clear()
End Sub
