1667195 - Support forwarding browser.dns to proxy

Status: UNCONFIRMED

(Core :: Networking: Proxy, enhancement, P5)

Description

[D Nupy]

Firefox does not currently forward browser.dns requests to a SOCKS5 proxy if a proxy is used. This prevents users who use proxies from fully utilizing extensions that make use of browser.dns API such as the popular uBlock Origin extension.

If there is a way browser.dns API information can be used or forwarded to a SOCKS5 proxy that would be very useful.

Comment 1

[Valentin Gosu [:valentin] {{ PTO 3 July - 3 August }}]

Not really.
The way I understand this works when using a proxy is that we just send the domain names to the proxy, and it performs the resolution itself.
We never have access to the IPs.

From what I understand there's a non-standard way the TOR browser uses the proxy to do just DNS resolution.
I think Tom might be able to point us to some documentation.

Comment 2

[Tom Ritter [:tjr]]

Hm, this is a tricky one. SOCKS5 the protocol does support using UDP for DNS lookups, but I'm not sure that's implemented in Firefox. Tor Browser can do DNS lookups, but it's a not-used-in-normal-operation part of the tor protocol, not actually something Tor Browser does or can do.

Comment 3

[Matthew Finkel [:sysrqb]]

(In reply to Tom Ritter [:tjr] (ni? for response to sec-[advisories/bounties/ratings/cves]) from comment #2)

Hm, this is a tricky one. SOCKS5 the protocol does support using UDP for DNS lookups, but I'm not sure that's implemented in Firefox. Tor Browser can do DNS lookups, but it's a not-used-in-normal-operation part of the tor protocol, not actually something Tor Browser does or can do.

Correct, the Tor client provides a "resolve" command [0] as an extension of the SOCKS5 protocol, but we've never needed that functionality in Tor Browser, so we never implemented (or uplifted) that into necko. I don't know of any other SOCKS5 implementations that support this extension (and if you're using Firefox with Tor, then you probably shouldn't be).

[0] https://spec.torproject.org/socks-extensions

Comment 4

[BMO Automation]

Moving bug to Core/Networking: Proxy.