R – ASP.NET URL validation

asp.netiisurl

We have a custom REST handler on ASP.NET that is configured like this to handle all incoming requests:

<add path="*" verb="*" type="REST.RESTProtocolHandler"/>

However, passing it a pipe character, properly encoded or not at all, triggers a validation error that seems to come from inside ASP.NET.

Accessing http://localhost:8080/%7c or http://localhost:8080/| yields this error:

[ArgumentException: Illegal characters in path.]
System.IO.Path.CheckInvalidPathChars(String path) +7489125
System.IO.Path.Combine(String path1, String path2) +40
System.Web.Configuration.UserMapPath.GetPhysicalPathForPath(String path, VirtualDirectoryMapping mapping) +114
System.Web.Configuration.UserMapPath.GetPathConfigFilename(String siteID, VirtualPath path, String& directory, String& baseName) +72
System.Web.Configuration.UserMapPath.MapPath(String siteID, VirtualPath path) +30
System.Web.Configuration.UserMapPath.MapPath(String siteID, String path) +31
System.Web.Hosting.HostingEnvironment.MapPathActual(VirtualPath virtualPath, Boolean permitNull) +297
System.Web.Hosting.HostingEnvironment.MapPathInternal(VirtualPath virtualPath, Boolean permitNull) +51
System.Web.CachedPathData.GetConfigPathData(String configPath) +341
System.Web.CachedPathData.GetVirtualPathData(VirtualPath virtualPath, Boolean permitPathsOutsideApp) +110
System.Web.HttpContext.GetFilePathData() +36
System.Web.HttpContext.GetConfigurationPathData() +26
System.Web.Configuration.RuntimeConfig.GetConfig(HttpContext context) +43
System.Web.Configuration.CustomErrorsSection.GetSettings(HttpContext context, Boolean canThrow) +41
System.Web.HttpResponse.ReportRuntimeError(Exception e, Boolean canThrow, Boolean localExecute) +101
System.Web.HttpRuntime.FinishRequest(HttpWorkerRequest wr, HttpContext context, Exception e) +383

No userland code gets executed. Is this a configuration option somewhere? Reproduced on IIS 7 & VS Studio's 2008 devel server.

Stack Overflow seems to handle this error OK, it looks like a dynamically generated 404 MVC page gets rendered for https://stackoverflow.com/%7c.

Any ideas?

Best Answer

Try to intercept the exception in Global.asax file. Implement there (Global.asax.cs) this method:

protected void Application_Error(Object sender, EventArgs e)
{
    Exception ex = Server.GetLastError();
    //do whatever you want with that exception
    //or get the url from the context, reformat and redirect
}
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