Archive for the ‘C#’ Category

C# Binding Redirects – Finding and Detecting Assembly Version of Any DLL

Monday, November 30th, 2020

C# Binding Redirects – Finding and Detecting Assembly Version of Any DLL

When dealing with binding redirects, you may not know the newVersion value to use for a recently updated library.  The file version of the DLL is not necessarily the assembly version of the DLL, and when it comes to binding redirects, you must use the correct assembly version for a particular library. 

For example, in the web.config for one of our MVC projects we have the following:

<runtime>
    <assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
       <dependentAssembly>
         <assemblyIdentity name="Antlr3.Runtime" publicKeyToken="eb42632606e9261f">
         <bindingRedirect oldVersion="0.0.0.0-3.5.0.2" newVersion="3.5.0.2">
       </dependentAssembly>
    </assemblyBiding>
</runtime>

If we update the Antlr3.Runtime package to the latest version in the nuget package manager, our binding redirects may not be automatically updated. As such, we will have to update it manually ourselves with the correct newVersion assembly version value for the updated DLL. To find the assembly version, run this PowerShell script (updating the path to the DLL as necessary):

[Reflection.AssemblyName]::GetAssemblyName('C:\development\bin\Antlr3.Runtime.dll').Version

This is the version number that is needed for the updated binding redirect in the "newVersion" attribute.

ASP.NET MVC – Smart Way to Prevent Cross-Site Request Forgery (CSRF) Attempts – WebAPI (AJAX XHR) and Normal POST Operations

Monday, August 12th, 2019

ASP.NET MVC – The Smart Way to Prevent Cross-Site Request Forgery (CSRF) Attempts

WebAPI (AJAX XHR) and Normal POST Operations

If your ASP.NET MVC application uses some WebAPI endpoints which are called using XHR (AJAX) requests from clientside JavaScript, you can still protect against CSRF attacks by validating the origin of such a request (when it is an AJAX request) or perform the default action of validating the anti-CSRF token (for POST form requests).

I modified the below code from https://stackoverflow.com/questions/35085507/set-validateantiforgerytoken-attribute-to-get-post-for-same-action-mvc5#answer-35085970 or ARCHIVE

using System.ComponentModel;
using System.Diagnostics;
using System.Diagnostics.CodeAnalysis;
using System.Web.Helpers;
using System.Linq;
using System.Collections.Generic;
using System.Configuration;
namespace System.Web.Mvc
{
    /// <summary>
    /// Cross-Site Request Forgery (CSRF) Prevention Filter for WebAPI and Normal MVC Controllers
    /// Normal POST operations = token is checked
    /// Normal controller GET operations = ignored
    /// WebAPI requests = check to make sure they were initiated by an AJAX request from a trusted origin
    /// </summary>    [AttributeUsage(AttributeTargets.Class | AttributeTargets.Method, AllowMultiple = false, Inherited = true)]
    public sealed class ValidateAntiForgeryTokenPOSTOrAJAXOrigin : FilterAttribute, IAuthorizationFilter
    {
        private string _salt;        

        public ValidateAntiForgeryTokenAttribute2() : this(AntiForgery.Validate)
        {
        }        

        internal ValidateAntiForgeryTokenAttribute2(Action validateAction)
        {
            Debug.Assert(validateAction != null);
            ValidateAction = validateAction;
        }
        
        [SuppressMessage("Microsoft.Naming", "CA2204:Literals should be spelled correctly", MessageId = "AdditionalDataProvider", Justification = "API name.")]
        [SuppressMessage("Microsoft.Naming", "CA2204:Literals should be spelled correctly", MessageId = "AntiForgeryConfig", Justification = "API name.")]
        [Obsolete("The 'Salt' property is deprecated. To specify custom data to be embedded within the token, use the static AntiForgeryConfig.AdditionalDataProvider property.", error: true)]
        [EditorBrowsable(EditorBrowsableState.Never)]
        
        public string Salt
        {
            get { return _salt; }
            set
            {
                if (!String.IsNullOrEmpty(value))
                {
                    throw new NotSupportedException("The 'Salt' property is deprecated. To specify custom data to be embedded within the token, use the static AntiForgeryConfig.AdditionalDataProvider property.");
                }
                _salt = value;
            }
        }

        internal Action ValidateAction { get; private set; }        
        
        public void OnAuthorization(AuthorizationContext filterContext)
        {
            string validOrigins = ConfigurationManager.AppSettings["AllowedEnvironments"]; // Example in web.config <add key="AllowedEnvironments" value="https://testurl.com:4443,https://testurl.com,https://testurl2.com" />
            bool skipCheck = false;
            
            if(ConfigurationManager.AppSettings["LocalDevMode"] == "1")
            {
                skipCheck = true;
            }
            
            // In AJAX requests, the origin header is always sent (UNLESS IT'S COMING FROM THE SAME ORIGIN), so we can validate that it comes from a trusted location to prevent CSRF attacks - but if one isn't sent, we won't do anything (assume trusted)
            // In which case, we don't need to do any token checking either 🙂
            if(!skipCheck && !string.IsNullOrEmpty(validOrigins))
            {
                List<string> validOriginURLs = validOrigins.Split(',').ToList();
                if(filterContext.HttpContext.Request.Headers["Origin"] != null && !string.IsNullOrEmpty(filterContext.HttpContext.Request.Headers["Origin"].ToString()))
                {
                    string origin = filterContext.HttpContext.Request.Headers["Origin"];
                    if(!validOriginURLs.Contains(origin))
                    {
                        filterContext.Result = new RedirectResult("~/Home/InvalidRequest");
                        skipCheck = true; // Still set to true to prevent additional validation
                    }
                    else
                    {
                        skipCheck = true;
                    }
                }
            }
        
            if(!skipCheck){
                var request = filterContext.HttpContext.Request.HttpMethod;
                if (request != "GET" && (!filterContext.HttpContext.Request.IsAjaxRequest() || (filterContext.HttpContext.Request.IsAjaxRequest() && (filterContext.HttpContext.Request.Headers["X-Request-With"] == null || filterContext.HttpContext.Request.Headers["X-Requested-With"] != "XMLHttpRequest"))))
                {
                    // Do normal form POST antiforgery token check
                    if (filterContext == null)
                    {
                        throw new ArgumentNullException("filterContext");
                    }                    try
                    {
                        ValidateAction();
                    }
                    catch(Exception e)
                    {
                        filterContext.Result = new RedirectResult("~/Home/InvalidRequest");
                    }
                }
            }
        }
    }
}

 

ASP.NET Web API – Accessing Session Information

Monday, August 12th, 2019

ASP.NET Web API – Accessing Session Information

If WebAPI needs access to SESSION information, here's how to do it:

https://stackoverflow.com/questions/9594229/accessing-session-using-asp-net-web-api#answer-17539008 or ARCHIVE

ASP.NET MVC – Using a Global Controller Filter to Add Information to the ViewBag

Monday, August 12th, 2019

Using a Global Controller Filter to Add Information to the ViewBag

There are times where you may want to add information to the ViewBag in ASP.NET MVC that should be available to all of the views referenced within certain controllers.  For this situation, you can create a global filter that can be applied at the controller or action specific level to make certain information available to the view via the usage of the ViewBag.

Here's a basic filter example:

public class TestInformationFilter : ActionFilterAttribute
{
    public override void OnActionExceuting(ActionExecutingContext context){
        // Set ViewBag Vars
        context.Controller.ViewBag.UserFirstName = context.Session["FirstName"];
        
        // Complete normal actions
        base.OnActionExecuting(context);
    }
}

Register your global filter by editing the FilterConfig.cs file found in the App_Start folder like so:

public class FilterConfig{
    public static void RegisterGlobalFilters(GlobalFilterCollection filters){
        filters.Add(new TestInformationFilter());
    }
}

Make all views from a controller have access to this ViewBag information by applying the filter to the controller:

[TestInformationFilter]
public class MyController{
   // My controller code here
}