1678978 - Setting proxy through `proxy.onRequest` API and working with `browser.dns` API will cause DNS leaks

Status: RESOLVED INVALID

(Core :: Networking, defect, P2)

Description

[nayinain]

Attachment: webext-DNSLeaksTest.zip

User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:85.0) Gecko/20100101 Firefox/85.0

Steps to reproduce:

1. Setting a socks5 proxy software to listen on 127.0.0.1:10808.
2. Load webext-DNSLeaksTest as a temporary extension.
3. Using the DNS leaks test service like:
   • https://browserleaks.com/dns
   • https://ipleak.net/
   • https://dnsleaktest.com/
   • http://whatismydnsresolver.com/

Actual results:

You can find the "DNS leaks" exposed your location.

Expected results:

---

Sorry for my bad English.

Comment 1

[BugBot [:suhaib / :marco/ :calixte]]

:nayinain, if you think that's a regression, then could you try to find a regression range in using for example mozregression?

Comment 2

[nayinain]

Attachment: webext-DNSLeaksTest.zip

Comment 3

[Kershaw Chang [:kershaw]]

So, looking at the code in nsDNSService::DNSForbiddenByActiveProxy, it's obvious that we didn't handle the case when proxyDNS is set by an extension.

Comment 4

[Kershaw Chang [:kershaw]]

Actually, I think this bug should be resolved as INVALID or WONTFIX.
Setting proxyDNS to true only indicates the DNS resolution for this web request should be done by the proxy. Therefore, it should not affect other requests globally.