Question

i uwant to cach input, which seems to be like SQL injection. So I wrote the method:

        public static bool IsInjection(string inputText)
    {


        bool isInj = false;


        string regexForTypicalInj = @"/\w*((\%27)|(\'))((\%6F)|o|(\%4F))((\%72)|r|(\%52))/ix";
        Regex reT = new Regex(regexForTypicalInj);
        if (reT.IsMatch(inputText))
            isInj = true;


        string regexForUnion = @"/((\%27)|(\'))union/ix";
        Regex reUn = new Regex(regexForUnion);
        if (reUn.IsMatch(inputText))
            isInj = true;



        string regexForSelect = @"/((\%27)|(\'))select/ix";
        Regex reS = new Regex(regexForSelect);
        if (reS.IsMatch(inputText))
            isInj = true;

        string regexForInsert = @"/((\%27)|(\'))insert/ix";
        Regex reI = new Regex(regexForInsert);
        if (reI.IsMatch(inputText))
            isInj = true;

        string regexForUpdate = @"/((\%27)|(\'))update/ix";
        Regex reU = new Regex(regexForUpdate);
        if (reU.IsMatch(inputText))
            isInj = true;

        string regexForDelete = @"/((\%27)|(\'))delete/ix";
        Regex reDel = new Regex(regexForDelete);
        if (reDel.IsMatch(inputText))
            isInj = true;

        string regexForDrop = @"/((\%27)|(\'))drop/ix";
        Regex reDr = new Regex(regexForDrop);
        if (reDr.IsMatch(inputText))
            isInj = true;

        string regexForAlter = @"/((\%27)|(\'))alter/ix";
        Regex reA = new Regex(regexForAlter);
        if (reA.IsMatch(inputText))
            isInj = true;

        string regexForCreate = @"/((\%27)|(\'))create/ix";
        Regex reC = new Regex(regexForCreate);
        if (reC.IsMatch(inputText))
            isInj = true;

        return isInj;

    }

But seems I have done some mistakes, becouse my code do not detects injections. What i do wrong? I guess theres something wrong in defining Regex expressions?

Answer 1

Don’t try to do this with RegEx – there are too many ways around it. See this classic SO answer about parsing with RegEx – it is specific to HTML, but still applies.

You should use Parameters, these are in the BCL and have anti SQL injection measures built in.

Update: (following comments)

If you really must parse the SQL, do not use RegEx for the reasons outlined in the linked article. RegEx is not a parser and should not be used as one.

Use a SQL parser – this should help with sanitizing attempts. Here is one, here another.

You can continue your scientific investigation with these.