用户名和密码验证vb.net

Question

我的程序检查userName和密码是否在数据库中（用Visual Basic编写并使用Access数据库）。但是，当我在不同的情况下输入userName或密码时，该程序仍可正常工作。例如，如果我的数据库的userName为“john”，密码为“johnspassword”，我的程序接受用户名为“JOHN”，密码为“JOHNSPASSWORD”。

我该如何解决这个问题？

Dim con As New OleDbConnection("Provider=Microsoft.jet.oledb.4.0;data source=C:\Users\jacob\Desktop\MS Office\project.mdb")
    Dim cmd As OleDbCommand = New OleDbCommand("SELECT * FROM tblUsers WHERE UserID = '" & txtUserName_Field.Text & "' AND userPassword = '" & txtUserPassword_Field.Text & "' ", con)
    con.Open()
    Dim sdr As OleDbDataReader = cmd.ExecuteReader()
    'If the record can be queried, it means passing verification, then open another form.
    Dim empty =
    Me.Controls.OfType(Of TextBox)().Where(Function(txt) txt.Text.Length = 0)
    If empty.Any Then
        MessageBox.Show(String.Format("Please fill in all the fields required"))
    Else
        If (sdr.Read() = True) Then
            MessageBox.Show("The is valid!")
            Form4.Show()
            Me.Hide()
        Else
            MessageBox.Show("Invalid name or password!")
        End If
    End If
    con.Close()
End Sub

Answer 1

如果您使用密码的哈希值，那么您可以解决两个问题：

• 您不应将密码存储为纯文本
• 哈希会使密码区分大小写

Rfc2898DeriveBytes Class适合创建哈希;您还需要为每个用户在数据库中存储随机生成的盐。

有许多网站，例如Salted Password Hashing - Doing it Right，解释了为什么需要腌制和散列。

您仍然需要确定是否需要用户名区分大小写。

修改

似乎Access doesn't have an efficient（即sargable）方式进行区分大小写的比较，因此您只需从数据库中获取用户名并在程序中进行检查，如下所示：< / p>

Option Infer On
Option Strict On

Imports System.Data.OleDb
Imports System.Security.Cryptography

Public Class SomeClass

    'TODO: decide on the sizes for the salt and hash
    'TODO: create binary fields in the database of appropriate sizes
    'TODO: consider storing the number of iterations in the database
    Const SALTLENGTH As Integer = 8
    Const HASHLENGTH As Integer = 16
    Const PBKDF2ITERATIONS As Integer = 20000

    Friend Function PBKDF2Hash(password As String, salt As Byte(), iterations As Integer, hashSize As Integer) As Byte()
        Dim hasher As New Rfc2898DeriveBytes(password, salt, iterations)
        Return hasher.GetBytes(hashSize)

    End Function

    Function IsLoginValid(username As String, password As String) As Boolean

        Dim salt(SALTLENGTH - 1) As Byte
        Dim hashedPassword(HASHLENGTH - 1) As Byte
        Dim usernameIsValid = False

        Dim csb As New OleDbConnectionStringBuilder With {
            .Provider = "Microsoft.jet.oledb.4.0",
            .DataSource = "C:\Users\jacob\Desktop\MS Office\project.mdb"
        }

        Using conn As New OleDbConnection(csb.ConnectionString)
            'TODO: use the actual column names
            Using cmd As New OleDbCommand("SELECT UserID, salt, password FROM tblUsers WHERE UserID = ?", conn)
                'TODO: use type of column as specified in the database
                cmd.Parameters.Add(New OleDbParameter With {.OleDbType = OleDbType.VarWChar, .Value = username})
                conn.Open()
                Dim rdr = cmd.ExecuteReader()
                If rdr.HasRows Then
                    rdr.Read()
                    If String.Compare(rdr.GetString(0), username, StringComparison.Ordinal) = 0 Then
                        rdr.GetBytes(1, 0, salt, 0, SALTLENGTH)
                        rdr.GetBytes(2, 0, hashedPassword, 0, HASHLENGTH)
                        usernameIsValid = True
                    End If
                End If

                conn.Close()
            End Using
        End Using

        Dim expectedHash = PBKDF2Hash(password, salt, PBKDF2ITERATIONS, HASHLENGTH)

        If usernameIsValid AndAlso hashedPassword.SequenceEqual(expectedHash) Then
            Return True
        End If

        Return False

    End Function

    Private Sub bnLogin_Click(sender As Object, e As EventArgs) Handles bnLogin.Click
        Dim username = txtUserName_Field.Text
        Dim password = txtUserPassword_Field.Text

        If username.Length = 0 OrElse password.Length = 0 Then
            MessageBox.Show("Please fill in all the fields required.")
            Exit Sub
        End If

        If IsLoginValid(username, password) Then
            ' user has supplied valid credentials
        Else
            MessageBox.Show("Invalid username or password.")
        End If

    End Sub

End Class

当然，您仍然需要创建代码，以便在用户注册时将适当的数据放入数据库中。