散列出错

Question

我使用相同的函数来哈希值以在登录期间进行比较，就像我在用户注册时哈希密码一样：

Public Shared Function Compute(ByVal text As String, ByVal algorithm As String, Optional ByVal salt() As Byte = Nothing) As String
    If salt Is Nothing Then
        Dim saltSize As Integer = 8
        salt = New Byte(saltSize - 1) {}

        Dim rng As New RNGCryptoServiceProvider
        rng.GetNonZeroBytes(salt)
    End If

    Dim textBytes As Byte() = Encoding.UTF8.GetBytes(text)
    Dim saltedTextBytes() As Byte = New Byte(textBytes.Length + salt.Length - 1) {}
    For i As Integer = 0 To textBytes.Length - 1
        saltedTextBytes(i) = textBytes(i)
    Next i

    For i As Integer = 0 To salt.Length - 1
        saltedTextBytes(textBytes.Length + i) = salt(i)
    Next i

    Dim hash As HashAlgorithm
    If algorithm Is Nothing Then
        algorithm = ""
    End If

    Select Case algorithm.ToUpper
        Case "SHA1" : hash = New SHA1Managed
        Case "SHA256" : hash = New SHA256Managed
        Case "SHA384" : hash = New SHA384Managed
        Case "SHA512" : hash = New SHA512Managed
        Case Else : hash = New MD5CryptoServiceProvider
    End Select

    Dim hashBytes As Byte() = hash.ComputeHash(saltedTextBytes)
    Dim saltedHash() As Byte = New Byte(hashBytes.Length + salt.Length - 1) {}
    For i As Integer = 0 To hashBytes.Length - 1
        saltedHash(i) = hashBytes(i)
    Next i

    For i As Integer = 0 To salt.Length - 1
        saltedHash(hashBytes.Length + i) = salt(i)
    Next i

    Dim hashValue As String = Convert.ToBase64String(saltedHash)

    Return Left(hashValue, 36)
End Function

我的问题是，当我尝试登录其密码已通过此函数哈希的帐户时，哈希值不会不匹配。我想我跳过了一个步骤或其他什么。

以下是创建用户帐户的代码：

        ' The email address needs to be valid
        Dim pattern As String = "^(?("")("".+?""@)|(([0-9a-zA-Z]((\.(?!\.))|[-!#\$%&'\*\+/=\?\^`\{\}\|~\w])*)(?<=[0-9a-zA-Z])@))(?(\[)(\[(\d{1,3}\.){3}\d{1,3}\])|(([0-9a-zA-Z][-\w]*[0-9a-zA-Z]\.)+[a-zA-Z]{2,6}))$"
        Dim match As Match = Regex.Match(txtEmail.Text, pattern)
        If match.Success Then
            'Hash the user's password before entering it into the database.
            Dim pass As String = Crypt.Compute(txtPass.Text, "SHA512", Nothing)

            ' Enter the information from the form into the database.
            Dim sql As String = "INSERT INTO Users(Username, Password, EmailAddress) " & _
                "VALUES(@User, @Pass, @Email)"
            Dim cmd As New SqlCommand(sql, conn)
            cmd.Parameters.AddWithValue("@User", txtName.Text)
            cmd.Parameters.AddWithValue("@Pass", pass)
            cmd.Parameters.AddWithValue("@Email", txtEmail.Text)

            conn.Open()
            cmd.ExecuteNonQuery()
            conn.Close()
        Else
            lblError.Text = "Invalid email address. Please correct."
            lblError.ForeColor = Drawing.Color.Red
        End If

这里未包含更多与我的问题无关的检查。

这是我的用户登录：

            Dim pass As String = Crypt.Compute(txtPass.Text, "SHA512", Nothing)

            Dim UserData As New DataSet
            Dim UserAdapter As New SqlDataAdapter
            UserAdapter.SelectCommand = New SqlCommand("SELECT * FROM Users " & _
                                                       "WHERE Username = @User AND Password = @Pass", conn)
            UserAdapter.SelectCommand.Parameters.AddWithValue("@User", txtUser.Text)
            UserAdapter.SelectCommand.Parameters.AddWithValue("@Pass", pass)
            UserAdapter.Fill(UserData)

            If UserData.Tables(0).Rows.Count <> 1 Then
                lblError.Text = "Invalid username or password."
                lblError.ForeColor = Drawing.Color.Red
                Session("LoginAttempt") = CInt(Session("LoginAttempt")) + 1
            Else
                Session("LoggedIn") = True
                Response.Redirect("Home.aspx")
            End If

据我所知，我在这里所做的哈希没有任何区别。

有人有什么想法吗？

Answer 1

1. 当您通过插入表来创建帐户时，您将使用 txtName.Text 作为用户名，但在检查凭据时，您将使用 txtUser.Text。

2. 为什么使用随机盐？每个加密的盐值是否都必须相同？我已将您的代码粘贴到一个新项目中，当我对同一密码连续运行 Compute 方法两次时，我得到两个不同的结果......显然这是行不通的。尝试传入盐值而不是Nothing，并使用相同的盐来创建帐户和比较登录。以下是一些有效的示例代码：

   将 thePass 调暗为字符串 = "MyPassword"
   将盐调暗为字符串=“盐”
   
   Dim pass As String = Compute(thePass, "SHA512", Encoding.UTF8.GetBytes(theSalt))
   Console.WriteLine(通过)
   Dim pass2 As String = Compute(thePass, "SHA512", Encoding.UTF8.GetBytes(theSalt))
   Console.WriteLine(pass2) 'pass 和 pass2 相同
   

希望这有帮助！

Answer 2

除非我错过了（不太熟悉该语言），否则您不会将盐存储在任何地方。

您必须使用在创建验证帐户时使用的相同盐。

附带说明：您可以为每个用户帐户生成随机盐，也可以为所有帐户使用固定盐。任何一种方法都有效。第一个在理论上更安全，但如果盐足够长，则两种方法都可以用于实际目的。