Redirecting HTTPS tunnel issues wrong certificate to the client

[Gavin]

I configured fiddler to redirect all https traffic destined to oldURL.com to newURL.com, using the below fiddlerscript sample from the Telerik Fiddler documentation.

This has been working fine for several months. Today I attempted to execute the same monthly process, but this time it failed.
After some investigation I noticed that fiddler is returning a certificate with the wrong CN
A quick test in Chrome shows that when browsing to https://oldURL.com, fiddler returns a certificate with a subject of CN=newURL.com

This causes the handshake to fail with my application, and the montly process to abort.

I can only assume that this issue crept in when I updated Fiddler last month to: v5.0.20181.14850 for .NET 4.6.1

I have now worked around this by also adding oSession["X-OverrideCertCN"] = "oldURL.com";

What is the correct way to redirect HTTPS request & Tunnel, whilst still providing a correctly named certificate to the client application?

 

https://docs.telerik.com/fiddler/KnowledgeBase/FiddlerScript/ModifyRequestOrResponse

<p>
 //Point all requests for one server to a different server, including HTTPS tunnels<br>
// Redirect traffic, including HTTPS tunnels
</p>
<p>
if (oSession.HTTPMethodIs("CONNECT") && (oSession.PathAndQuery == "www.example.com:443"))<br>
{ <br>
    oSession.PathAndQuery = "beta.example.com:443";<br>
}<br>
<br>
if (oSession.HostnameIs("www.example.com")) oSession.hostname = "beta.example.com";
</p>

[Alexander]

Hello,

What you are experiencing now seems to be the expected and correct behavior. Using the X-OverrideCertCN flag is the proper way to fix it.

However, the original behavior (the one you observed before the update) seems to be incorrect and I want to examine it. Do you, by any chance, remember which version you updated from? If not - at least do you remember when did you update for the last time (before the v5.0.20181.14850 update, of course)?

Regards,
Alexander
Progress Telerik

[Gavin]

I am sorry, but I do not know what version I previously had.

Is there an upgrade log file that might show what version it replaced?

[Alexander]

Hi,

Rather unfortunately, there is not. One thing that we can do is to check the "Date created" of the "%LOCALAPPDATA%\Programs\Fiddler" folder. This can reduce the range of version which I should check in order to reproduce the problem.

Regards,
Alexander
Progress Telerik