IP and DNS Leaks in WebKit Affecting Proxy Browsers and iCloud Private Relay

exabrial | 20 hours ago

I love iCloud private relay, but I need a way to turn it off. A command line utility would be amazing, along with the ability to turn off/on DNS-over-HTTP.

TechRemarker | 20 hours ago

You can turn if off in settings > iCloud. Either temporary for a day and auto back on, or permanently until you turn it back on.

exabrial | 19 hours ago

Yep, but one cannot script that, make it a part of a bash or automator actions, which is a problem.

dgsii | 19 hours ago

Have you tried recording UI events in Automator and saving it as an Application? Then you could execute the .app via script. I haven't done this but in theory it should work.

dabbz | 16 hours ago

There's a PLIST entry possibly relevant to it in `~/Library/Preferences/com.apple.networkserviceproxy.plist`

I couldn't figure out how to get any changes to reflect but maybe it's a good pointer towards a solution?

EDIT: Reading into this, looks like they're very intentional about not allowing arbitrary enable/disable calls to it, likely to prevent a hostile entity from switching it off on unsuspecting users. The systems setting calls an XPC into a daemon that makes a web request, then validates the response from the API to update the PLIST structure.

user43928 | 10 hours ago

osascript with System Events seems to work for opening the right modal in Settings and flipping the switch On, in a quick test.

I did not verify whether it works reliably.

If it does, one could probably package it as a .app and grant only that the Accessibility permission.

klausa | 13 hours ago

I desperately wish there was a "Turn off for five minutes, I'm dealing with dumb corpsec auth stuff" option.

pasc1878 | 6 hours ago

In macOS view->reload and show IP address

rickstanley | 19 hours ago

When I go to https://leaks.psylo.app on "Possible IP leaks" side I see only "WebAuthn" with my real IP and, occasionally, WebTransport with an incorrect IP. For "HTTPS Traffic" it always show some other relay. Using Safari 26.5

I'm not sure what would I use WebAuthn for, if ever, maybe I could disable it through "Feature Flags" menu?; regardless, I never treat Apple's services as "premium", since the email fingerprinting thing. I pay mainly for Hide My Email, just to organise things per domain, and it's cheap.

goalieca | 18 hours ago

Webauthn is the api for Passkeys and things.

sam_lowry_ | 12 hours ago

So WebAuthn leaks real IPs, who would have thought!

inigyou | 9 hours ago

Yeah. For authentication. It's important that the large tech company knows who you are.

TeMPOraL | 9 hours ago

Yes, who would've thought Passkeys are a bad idea.

Now for yet another reason.

Semaphor | 8 hours ago

It’s more than just Passkeys, Webauthn is super convenient with my YubiKeys, I even have it set up as 2FA on some selfhosted services.

Semaphor | 8 hours ago

Depends on the browser apparently? Only on Webkit is what it says, it’s not clear if the site doesn’t support FF, or if FF is secure.

[OP] lapcat | 8 hours ago

WebKit passes the request to a separate system process.

On Mac, Firefox and Chrome, which don't use WebKit, handle WebAuthn themselves.

walrus01 | 17 hours ago

Weird advertising on site: "Psylo is our privacy-first browser for iOS and iPadOS"

Correct me if I'm wrong but doesn't Apple disallow any actual 3rd party browser engines? Like, any browser on iOS that isn't the standard safari is just a skin on top of webkit/safari. It doesn't exactly inspire confidence that some third party browser will be able to implement things any better (as compared to like, running Firefox on Android, which actually implements the firefox browser engine).

internet2000 | 17 hours ago

Networking is not handled by the rendering engine, which is an only a part of a browser app. That’s a credible claim.

TingPing | 15 hours ago

Networking is very core to webkit of course. But it has apis to block and modify requests.

afavour | 13 hours ago

But WKWebView does handle its own networking. You’re able to implement block lists, just the same as you can via browser plugin, but in this instance networking definitely is handled by WebKit.

Aaargh20318 | 13 hours ago

Networking is handled by WebKit but based on the article it looks like the app configures itself as a HTTP proxy for WebKit and uses that to handle networking.

inigyou | 11 hours ago

So it can't do anything about proxy leaks.

hnav | 14 hours ago

My read is that the main value prop is that they configure the WKWebView to not share any state cross-tabs. In the post they state that they've disabled DNS prefetch, WebTransport and WebAuthn so obviously they're hardening beyond what ships in Safari (though some of this may already be covered by lockdown mode).

irusensei | 6 hours ago

Apple private relay is very flawed but on the other hand most sites that view connections originating from VPN as suspicious seem to be ok with Apple Private Relay. If you have VPN on your router private relay on top of it could be a good way to do ip address laundering.

lxgr | 5 hours ago

I find it pretty annoying that iCloud Private Relay does not work together with VPNs.

I mainly use VPNs to access bank sites (or other sites that are annoying enough to use IP country as a proxy for traffic being evil/legitimate) when traveling, but I often forget to turn off the VPN afterwards, and then spend the rest of my day browsing from my home IP (that terminates the VPN), which would have been hidden behind Private Relay if I'd actually been browsing from my home Wi-Fi.

Cross-site/app ad targeting getting creepy good despite using different browser profiles for work/personal browsing etc. is usually a good tell (at least on IPv6).

kittikitti | 5 hours ago

Thank you for this report. My real IP on my phone was constantly leaking and I knew that WebKit was a culprit. However, I doubt that this was an accident. This is a backdoor that Apple planted.

solenoid0937 | 4 hours ago

https://psylo.app/legal/privacy/

Lots of these seem unnecessary, especially collecting "bandwidth usage" and "timestamps".