1535581 - proxy settings for localhost not obeyed unless network.proxy.allow_hijacking_localhost is set

Status: RESOLVED WONTFIX

(Core :: Networking, defect)

Description

[jelle.criel]

Attachment: BSLpmM3.png

User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:67.0) Gecko/20100101 Firefox/67.0

Steps to reproduce:

Set up proxy settings to use a proxy on https://localhost:8080
The website I'm using is running on http://localhost:8010
proxy settings screenshot: https://i.imgur.com/BSLpmM3.png
I tested with a webpage where I opened the Developer tools and checked the "Disable cache" checkbox.

Actual results:

The HTTP-messages are not routed though the HTTP-proxy (burp suite).
Even when I close the proxy all traffic is still sent to localhost:8010

Expected results:

the HTTP-messages should be routed through the HTTP-proxy. When I close the proxy I shouldn't get any HTTP-replies.

Comment 1

[Matthias Versen [:Matti]]

Is this only a problem when you try to access a localhost page through the proxy or is nothing routed through the proxy ?
Is this only happening in Firefox67 or did you used this configuration in the past with other Firefox versions ?
What kind of proxy software you are using ?

Comment 2

[jelle.criel]

Is this only a problem when you try to access a localhost page through the proxy?
yes. I'm trying to do Firefox -> proxy -> localhost.
what I get is Firefox -> localhost. and for any other website I get: Firefox -> proxy -> localhost

or is nothing routed through the proxy?
Everything but localhost is routed through the proxy.

Is this only happening in Firefox67 or did you used this configuration in the past with other Firefox versions?
I used the same configuration in the firefox versions of the past 12 months and I only noticed this issue now.

I'm using burp suite community, an HTTP-proxy.

Let me know if I can clarify anything else. :)

Comment 3

[Matthias Versen [:Matti]]

I can confirm the reported bug with Firefox nightly on windows.
A localhost proxy is not used when the "no proxy" section is empty and you try open a http server with http://localhost:port

This regression is easy to see if you use a complete new profile and open options/general/network settings
In working builds you can see "localhost, 127.0.0.1" in the no proxy section while this field is empty in broken builds.

3:17.29 INFO: No more inbound revisions, bisection finished.
3:17.29 INFO: Last good revision: e92ff56d2be21676b447c6fbb87b4c4479539bc9
3:17.29 INFO: First bad revision: cd28688c1642889442179c459ce5e6cce9a3317e
3:17.29 INFO: Pushlog:
https://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=e92ff56d2be21676b447c6fbb87b4c4479539bc9&tochange=cd28688c1642889442179c459ce5e6cce9a3317e

In that range this checkin looks like the culprit:

Junior Hsu — Bug 1507110 - Allow hijacking localhost only if network.proxy.allow_hijacking_localhost is set r=Gijs,mayhemer,mkaply,jmaher

It looks like this behavior change is wanted when I look at that checkin

Comment 4

[:Gijs (he/him)]

Yes. Set network.proxy.allow_hijacking_localhost to true in about:config if you need this to work.

Comment 5

[Junior [inactive]]

Thanks, :Matti and :Gijs

Comment 7

[Seth Russell]

So this problem unexpectedly broke one of my key use cases for Firefox.

I'm fine with the workaround/wontfix status. However, I would appreciate if changes like this (worked one way in FF66, doesn't work in FF67 or going forward) were better communicated to users. I know many features and bugs are resolved with every release, but it would be nice if breaking changes were better communicated in the release notes shown upon updating FF.

Thanks for all the great work!