How to configure the XML parser to disable external entity resolution in c#

Question

var xDoc = XDocument.Load(fileName);

I am using above code in a function to load an XML file. Functionality wise its working fine but it is showing following Veracode Flaw after Veracode check.

Description

The product processes an XML document that can contain XML entities with URLs that resolve to documents outside of the intended sphere of control, causing the product to embed incorrect documents into its output. By default, the XML entity resolver will attempt to resolve and retrieve external references. If attacker-controlled XML can be submitted to one of these functions, then the attacker could gain access to information about an internal network, local filesystem, or other sensitive data. This is known as an XML eXternal Entity (XXE) attack.

Recommendations

Configure the XML parser to disable external entity resolution.

What I need to do to resolve it.

Answer 1

Implement a custom XmlResolver and use it for reading the XML. By default, the XmlUrlResolver is used, which automatically downloads the resolved references.

public class CustomResolver : XmlUrlResolver
{
    public override object GetEntity(Uri absoluteUri, string role, Type ofObjectToReturn)
    {
        // base calls XmlUrlResolver.DownloadManager.GetStream(...) here
    }
}

And use it like this:

var settings = new XmlReaderSettings { XmlResolver = new CustomResolver() };
var reader = XmlReader.Create(fileName, settings);
var xDoc = XDocument.Load(reader);