C#/.NET: GETting a URL with an url-encoded slash

Question

I want to send a HTTP GET to http://example.com/%2F. My first guess would be something like this:

using (WebClient webClient = new WebClient())
{
  webClient.DownloadData("http://example.com/%2F");
}

Unfortunately, I can see that what is actually sent on the wire is:

GET // HTTP/1.1
Host: example.com
Connection: Keep-Alive

So http://example.com/%2F gets translated into http://example.com// before transmitting it.

Is there a way to actually send this GET-request?

The OCSP-protocol mandates sending the url-encoding of a base-64-encoding when using OCSP over HTTP/GET, so it is necessary to send an actual %2F rather than an '/' to be compliant.

EDIT:

Here is the relevant part of the OCSP protocol standard (RFC 2560 Appendix A.1.1):

An OCSP request using the GET method is constructed as follows:

GET {url}/{url-encoding of base-64 encoding of the DER encoding of the OCSPRequest}

I am very open to other readings of this, but I cannot see what else could be meant.

Answer 1

%2F can not be used in path, however it can be used after query string like

/?%2F <-- this will be correct one...

Answer 2

Double encode it : %252F

But also if you use HttpWebRequest you can actually tell not to encode the URL, either way it should work.

Also If WebClient accepts URI then you can create a new URI and you can set it to not encode.

Answer 3

Sounds like a bug in the OCSP protocol to me (or, alternatively, a misinterpretation of it).

Answer 4

This is a terrible hack, bound to be uncompatible with future versions of the framework and so on.

But it works!

(on my machine...)

Uri uri = new Uri("http://example.com/%2F");
ForceCanonicalPathAndQuery(uri);
using (WebClient webClient = new WebClient())
{
  webClient.DownloadData(uri);
}

void ForceCanonicalPathAndQuery(Uri uri){
  string paq = uri.PathAndQuery; // need to access PathAndQuery
  FieldInfo flagsFieldInfo = typeof(Uri).GetField("m_Flags", BindingFlags.Instance | BindingFlags.NonPublic);
  ulong flags = (ulong) flagsFieldInfo.GetValue(uri);
  flags &= ~((ulong) 0x30); // Flags.PathNotCanonical|Flags.QueryNotCanonical
  flagsFieldInfo.SetValue(uri, flags);
}