include::../description.adoc[]

== Noncompliant Code Example

----
using Microsoft.AspNetCore.Mvc;

namespace WebApplicationDotNetCore.Controllers
{
    public class RSPEC5146OpenRedirectNoncompliantController : Controller
    {
        public IActionResult Index()
        {
            return View();
        }

        private readonly string[] whiteList = { "https://www.sonarsource.com" };

        public IActionResult RedirectMe(string url)
        {
            return Redirect(url);
        }
    }
}
----

== Compliant Solution

----
using System.Linq;
using Microsoft.AspNetCore.Mvc;

namespace WebApplicationDotNetCore.Controllers
{
    public class RSPEC5146OpenRedirectCompliantController : Controller
    {
        public IActionResult Index()
        {
            return View();
        }

        private readonly string[] whiteList = { "https://www.sonarsource.com" };

        public IActionResult RedirectMe(string url)
        {
            // Match the incoming URL against a whitelist
            if (!whiteList.Contains(url))
            {
                return BadRequest();
            }

            return Redirect(url);
        }
    }
}
----

== See

* https://docs.microsoft.com/en-us/aspnet/core/security/preventing-open-redirects?view=aspnetcore-3.1[Microsoft Documentation ASP.NET Core] - Prevent Open Redirect Attacks in ASP.NET Core
* https://docs.microsoft.com/en-us/aspnet/mvc/overview/security/preventing-open-redirection-attacks[Microsoft Documentation ASP.NET MVC] - Preventing Open Redirection Attacks
* https://www.owasp.org/index.php/Top_10-2017_A5-Broken_Access_Control[OWASP Top 10 2017 Category A5] - Broken Access Control
* https://cwe.mitre.org/data/definitions/601.html[MITRE, CWE-601] - URL Redirection to Untrusted Site ('Open Redirect')
* https://www.sans.org/top25-software-errors/#cat2[SANS Top 25] - Risky Resource Management