Want a PrincipalPermission SecurityException on REST service to return 403, not 400 Bad Request

Question

Want a PrincipalPermission SecurityException on REST service to return 403, not 400 Bad Request

241 Views Asked by James King At 05 April 2025 at 14:14

I have a RESTful (WCF) service decorated with PrincipalPermission demands. I expected a 403 FORBIDDEN response if the user does not hold the role, but get a 400 BAD REQUEST, instead. Upon reflection, this makes sense - the demand triggers a SecurityException when the principal doesn't hold the role; it's not the same as granting access through an <authorization> tag in the web.config.

However, a 400 BAD REQUEST doesn't make sense... the request wasn't malformed, I just didn't have permission to make the call. A 400 response implies I could fix the request and try again, but that will never succeed.

How could I intercept or map a SecurityException to a more appropriate response (preferably 403 FORBIDDEN)?

Decorated method:

[PrincipalPermission(SecurityAction.Demand, Role = "FST")]
public string TestNoPermissions(string NetworkId) {
    return "Call succeeded";
}

Response:

<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
  <head>
    <title>Request Error</title>
    <style>BODY { color: #000000; ...;}</style>
  </head>
  <body>
    <div id="content">
      <p class="heading1">Request Error</p>
      <p>The server encountered an error processing the request. The exception message is 'Access is denied.'. See server logs for more details. The exception stack trace is: </p>
      <p>   at System.ServiceModel.Dispatcher.SyncMethodInvoker.Invoke(Object instance, Object[] inputs, Object[]&amp; outputs)
            at System.ServiceModel.Dispatcher.DispatchOperationRuntime.InvokeBegin(MessageRpc&amp; rpc)
            at System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage5(MessageRpc&amp; rpc)
            at System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage11(MessageRpc&amp; rpc)
            at System.ServiceModel.Dispatcher.MessageRpc.Process(Boolean isOperationContextSet)</p>
    </div>
  </body>
</html>

Original Q&A

There are 1 best solutions below

**ste-fu** · Accepted Answer

You could implement an IErrorHandler to intercept the SecurityException. and then provide a WebFaultException with the status code.

public void ProvideFault(Exception error, MessageVersion version, ref Message fault)
{
    if (error is SecurityException)
    {
        var faultEx = new WebFaultException<string>("Forbidden", HttpStatusCode.Forbidden)

        fault = Message.CreateMessage(version, faultEx.CreateMessageFault(), null);
    }
}

Note this is untested - security exceptions have a nasty habit of getting lost within frameworks / pipelines but this idea was a bit long for a comment.

Usually you would add your custom IErrorHandler with a behavior, which can be configured in your DI code or in config.

public class ErrorHandlerBehavior : IServiceBehavior
{
    public void AddBindingParameters(ServiceDescription serviceDescription, ServiceHostBase serviceHostBase, Collection<ServiceEndpoint> endpoints, BindingParameterCollection bindingParameters)
    {
        // not implemented
    }

    public void ApplyDispatchBehavior(ServiceDescription serviceDescription, ServiceHostBase serviceHostBase)
    {
        foreach (var dispatcherBase in serviceHostBase.ChannelDispatchers)
        {
            var dispatcher = dispatcherBase as ChannelDispatcher;

            if (dispatcher != null)
                dispatcher.ErrorHandlers.Add(new MyCustomErrorHandler());
        }
    }

    public void Validate(ServiceDescription serviceDescription, ServiceHostBase serviceHostBase)
    {
        // not implemented
    }
}

Want a PrincipalPermission SecurityException on REST service to return 403, not 400 Bad Request

There are 1 best solutions below

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