1854324 - proxy.onRequest failure to bypass proxy for localhost

Status: NEW

(WebExtensions :: Request Handling, enhancement, P3)

Description

[erosman]

Connections to localhost, 127.0.0.1/8, and ::1 are never proxied.

There are 2 main proxying API in Firefox:

• proxy.settings which sets the values of browser Connection Settings (i.e. an interface for Connection Settings)
• proxy.onRequest which is based on webRequest API and intercepts net requests

Chrome only has proxy.settings.

localhost

• proxy.settings in both Firefox and Chrome implement a default bypass/pass-through for localhost
• proxy.onRequest does not appear to have the above default bypass

In addition to the unexpected behaviour, there are security considerations associated with proxying localhost.

The question is, shouldn't proxy.onRequest have a default bypass/pass-through for localhost to maintain the uniformity of the policy?

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See also:

• Connections to localhost, 127.0.0.1/8, and ::1 are never proxied
• Implicit bypass rules
• Proxy localhost and loopback addresses in Chrome
• https://searchfox.org/mozilla-central/source/toolkit/system/windowsproxy/nsWindowsSystemProxySettings.cpp#127-134
• https://searchfox.org/mozilla-central/source/netwerk/test/gtest/TestProtocolProxyService.cpp#26-37

Comment 1

[Gabriel Corona]

For what it's worth, proxying *.localhost is quite useful for mapping Unix-domain-socket-bound services into http://*.localhost URIs (https://github.com/randomstuff/soxidizer): *.localhost have the good taste of being considered as secure contexts.

However, proxying localhost URIs to remote servers is certainly problematic and considering proxied *.localhost services as secure contexts might not make much sense either.

Comment 2

[Gabriel Corona]

For reference, bug entry for FoxyProxy about the ability to disable the localhost bypass: https://github.com/foxyproxy/browser-extension/issues/50