CSHARP.IO.TAINT.REGEX : Tainted Regular Expression (C#)

Summary

Tainted data flows into a field annotated as [RegexTrusted], or into a regular expression.

This is very dangerous because could lead to exponential backtracking, infinite recursion, or untrusted behaviors (steal sensitive data, perform a privilege escalation, etc.).

Checks for this class use the CodeSonar C# taint analysis. See Taint Tracking for CodeSonar C# Warning Classes for more information on this analysis, including lists of the methods that CodeSonar automatically recognizes as relevant and information about specifying additional methods that CodeSonar should recognize as taint sources, sinks, or sanitizers.

Use configuration parameter CSHARP_ANALYSIS_ADVANCED_INJECTION to specify the level of checking to perform for this and other taint-related warning classes:

• For basic checking, set CSHARP_ANALYSIS_ADVANCED_INJECTION=No in your project configuration file.
• For advanced checking, set CSHARP_ANALYSIS_ADVANCED_INJECTION=Yes.

Properties

WARNING_FILTER += discard class="Tainted Regular Expression (C#)"

Example

using com.juliasoft.julia.checkers.injection;
using System;

using System.IO;
using System.Web;
using System.Web.UI;
using System.Text.RegularExpressions;

public class RegexInjection : Page
{

    private string adminUserName;
    
    public void ProcessRequest(HttpRequest request, HttpResponse response)
    {

        String user = request.Params["user"];

        String data = request.Params["data"];

        Regex rx = new Regex(user); // Tainted Regular Expression (C#) warning issued here

        if(rx.IsMatch(adminUserName))
        {
        
            ...
        }
        
    }
    
    ...
    
}

Resolution

Verify that a security error actually corresponds to unconstrained information flow from source locations into sink locations. If this is the case, add a sanitizing algorithm to clean data before it flows into sinks, or use prepared statements for SQL queries rather than free queries built from string concatenation.

Relevant Configuration File Parameters

The following configuration file parameters affect checks for this warning class.

• CSHARP_ANALYSIS_ADVANCED_INJECTION
• CSHARP_ANALYSIS_FIELD_SENSITIVE
• CSHARP_ANALYSIS_MERGE_CREATION_POINTS
• CSHARP_ANALYSIS_TRUST_DATABASE
• CSHARP_ANALYSIS_TRUST_DEVICE
• CSHARP_ANALYSIS_TRUST_ENVIRONMENT
• CSHARP_ANALYSIS_TRUST_EXTERNAL_STREAMS
• CSHARP_ANALYSIS_TRUST_USER_INPUT
• REPORT_SIMILAR_WARNINGS
• WARNING_FILTER