Login to start a new topic

Fiddler doesn't honor system-level PAC script proxy setting

Hi,

I'm using a PAC script as a system proxy. When I save the script address, I get a yellow bar on Fiddler with "The system proxy was changed. Click to reenable capturing". When I access the internet, my system honors the PAC script but I don't see the traffic in Fiddler. When I click on the yellow band and enable capturing, I see the traffic flowing in Fiddler but Fiddler doesn't honor the PAC script. 

In the Event Log, I see "Proxy Configuration Script specified an unreachable proxy". Any thoughts on why we are seeing this log? The proxy endpoint(https://azflex.example.com) is reachable and without Fiddler, traffic is flowing through the specified proxy.

-= Progress Telerik Fiddler Classic Event Log =-

11:01:07:1802 [Fiddler] No HTTPS request was received from (chrome:14628) new client socket, port 51199.
11:01:10:4943 HTTPSLint> Warning: ClientHello record was 508 bytes long. Some servers have problems with ClientHello's greater than 255 bytes. https://github.com/ssllabs/research/wiki/Long-Handshake-Intolerance
11:01:53:9461 HTTPSLint> Warning: ClientHello record was 508 bytes long. Some servers have problems with ClientHello's greater than 255 bytes. https://github.com/ssllabs/research/wiki/Long-Handshake-Intolerance
11:01:54:8862 HTTPSLint> Warning: ClientHello record was 508 bytes long. Some servers have problems with ClientHello's greater than 255 bytes. https://github.com/ssllabs/research/wiki/Long-Handshake-Intolerance
11:01:54:9822 WinINET Registry change detected. Verifying proxy keys are intact...
11:01:54:9852 WinINET API indicates that Fiddler is no longer attached.
11:02:03:3497 Proxy Configuration Script specified an unreachable proxy: https://azflex.example.com:443 for URL: https://mail.google.com/
11:02:03:3537 Proxy Configuration Script specified an unreachable proxy: https://azflex.example.com:443 for URL: https://safebrowsing.googleapis.com/
11:02:03:3547 Proxy Configuration Script specified an unreachable proxy: https://azflex.example.com:443 for URL: https://mail.google.com/
11:02:03:6541 Proxy Configuration Script specified an unreachable proxy: https://azflex.example.com:443 for URL: https://people-pa.clients6.google.com/

But if I were to give the below gateway settings, Fiddler is honoring the proxy endpoint and I see traffic captured in Fiddler.

image.png

 

Any help in resolving this issue is much appreciated. Thanks!

1 Comment


Based on the images you have provided, it looks like you are hitting the issue with Fiddler Classic (where this forum is primary for Fiddler Everywhere).

It seems that the proxy is inaccessible, so we can't test the scenario on our side. However, there are a few things you could try:


- Stop Fiddler Classic capturing. Go to Options > Gateway and set the Use System Proxy option. Close the application entirely.

- Save your PAC script in the operating system proxy settings.

- Start Fiddler Classic anew and observe if you can access and capture the HTTP/HTTPS traffic. Check if you are still receiving the unreachable error

Proxy Configuration Script specified an unreachable proxy.



Then test the same scenario in Fiddler Everywhere if the issues persist.


- Stop Fiddler Classic application entirely.

- Start Fiddler Everywhere, go to Settings > Gateway and choose the Use System Proxy option.

- Stop Fiddler Everywhere capturing and close the application entirely.

- Save your PAC script in the operating system proxy settings.

- Start Fiddler Everywhere and observe if you can access and capture the HTTP/HTTPS traffic. Check if you are still receiving the unreachable error.


If you are observing the same error in Fiddler Everywhere, please send us the Fiddler Everywhere application logs (accessible through Help > Open Application Logs Folder).

Login to start a new topic