Sanitizing SQL data

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我寻月下人不归
我寻月下人不归 2021-01-04 18:13

Google turns up all sorts of discussions on sanitizing queries for web access but I\'m not finding anything addressing what I\'m concerned with:

Sanitizing user inpu

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  •  醉梦人生
    2021-01-04 18:57

    It depends on what SQL Database you are using. For instance if you want a single quote literal in MySQL you need to use a backslash, Dangerous: ' and an escaped escaped character literal: \'. For MS-SQL things are completely different, Dangerous: ' escaped:''. Nothing is removed when you escape data in this fashion, it a way of representing a control character such as a quote mark in its literal form.

    Here is an example of using parameterized queries for MS-SQL and C#, taken from the Docs:

    private static void UpdateDemographics(Int32 customerID,
        string demoXml, string connectionString)
    {
        // Update the demographics for a store, which is stored 
        // in an xml column. 
        string commandText = "UPDATE Sales.Store SET Demographics = @demographics "
            + "WHERE CustomerID = @ID;";
    
        using (SqlConnection connection = new SqlConnection(connectionString))
        {
            SqlCommand command = new SqlCommand(commandText, connection);
            command.Parameters.Add("@ID", SqlDbType.Int);
            command.Parameters["@ID"].Value = customerID;
    
            // Use AddWithValue to assign Demographics.
            // SQL Server will implicitly convert strings into XML.
            command.Parameters.AddWithValue("@demographics", demoXml);
    
            try
            {
                connection.Open();
                Int32 rowsAffected = command.ExecuteNonQuery();
                Console.WriteLine("RowsAffected: {0}", rowsAffected);
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.Message);
            }
        }
    }
    

    For MySQL i am not aware of a parameterized query library you can use. You should use mysql_real_escape_string() or opointally you could use this function.:

    public static string MySqlEscape(this string usString)
    {
        if (usString == null)
        {
            return null;
        }
        // SQL Encoding for MySQL Recommended here:
        // http://au.php.net/manual/en/function.mysql-real-escape-string.php
        // it escapes \r, \n, \x00, \x1a, baskslash, single quotes, and double quotes
        return Regex.Replace(usString, @"[\r\n\x00\x1a\\'""]", @"\$0");
    }
    

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