Android NAT-T keepalive offload bypasses VPN lockdown (supuk.ch)
176 pointsby mhitzaa day ago44 comments
jeroenhd 7 hours ago
> FortiClient VPN and SmartVPN have 4,134,648 cumulative Google Play installs between them, while Google reports more than 3 billion active Android devices.
A very strange way to reason about killing an API instead of fixing the VPN issue (as someone from Google already suggested they're planning on doing). "Only 4 million people use this, we should kill it" is exactly the kind of reasoning Microsoft in the 2000s would use to kill the ability to install Linux on a PC.
ValdikSS 6 hours ago
Android has a way to bind the socket to the interface: Network.bindSocket, this is a setsockopt(SO_BINDTODEVICE) wrapper with access control.
The access to it is controlled by the VPN application. Some applications could be allowed to connect directly when the VPN is active and routing all the traffic by default, some could use VPN if configured not to use it by default.
However starting with Linux kernel 5.7, the unprivileged userspace can now call setsockopt(SO_BINDTODEVICE) directly and use VPN or non-VPN interface even if restricted by the VPN client.
Not fixed in any Android (incl. Graphene, which has fixes for other leaks, but not this) to the day.
PoC is as simple as "curl --interface [ifname, not IP] ifconfig.co" in termux.
brinepot 16 hours ago
'Closed without action' is the tell. A leak that Google knows about and leaves in place isn't a bug anymore, it's a feature they're comfortable with.
grapheneos 12 hours ago
Google considers VPN leaks to be valid bugs but unfortunately doesn't consider them security bugs. Internal issues are created for any issue report considered valid. The external one is only used to communicate with people. If it was filed as a security bug, they'll close it if it isn't considered within the scope of the bounty program.
exceptione 12 hours ago
I am not sure why all your comments are flagged, but here is my response to your other comment:
> We plan to heavily overhaul the VPN implementation to make most forms of leaks nearly impossible rather than continuing to use the current system prone to it.
grapheneos 11 hours ago
> I am not sure why all your comments are flagged
The past couple weeks of our replies were maliciously flagged. We've made a post about it on social media as we've had to do before when this happens. This happens very regularly to posts by GrapheneOS or posts which simply support GrapheneOS. There are a bunch of malicious accounts which show up to each thread about GrapheneOS to make personal attacks towards our team, baselessly claim it's a honey pot, promote non-hardened products reducing privacy/security compared to AOSP and to make a bunch of disingenuous attacks towards it. The attacks towards our team often involve fabricated stories about us and harassment content. There's an account active in many of these recent threads making disingenuous replies and spreading Kiwi Farms harassment content in their profile:
That account should clearly be banned rather than a subset of their posts getting flagged. The same applies to several other blatant ones.
exceptione 18 hours ago
This paper goes into much more detail: https://supuk.ch/papers/android-natt-keepalive-vpn-bypass
codedokode 8 hours ago
The stupid thing about Android is that it requires you to set a PIN to use Always-on VPN which is necessary for traffic filtering (as Android doesn't provide access to nft).
driverdan 7 hours ago
Why wouldn't you set a PIN?
codedokode 7 hours ago
What's the point of setting a PIN if Cellebrite can hack almost any phone?
unethical_ban 7 hours ago
Not every pocket thief or drunkard who finds your phone has cellebritr. Security measures consider the threat model.
More specifically, another commenter in this thread says it's to make sure the user is aware of the configuration of a VPN which, if done maliciously, funnels all your traffic toa a hostile place.
codedokode 5 hours ago
A pocket thief will bring the phone to a friend with a laptop and black market software. If the phone has no theft protection, they will factory reset it; if it has, they will use paid software to remove protection. I have not used that software and do not know if it is actual now, but Internet search shows that older phones are completely unlockable.
Just to give an example, here is publicly available information: https://github.com/youngrichu/frp-freedom/blob/main/FRP%20By...
Good thing is that some of the aforementioned exploits can be used to work around locked bootloader and liberate the phone.
Do not rely on any security in Android. It has lot of mistakes, poorly coded high privilege vendor software, so it would be dumb to use it for anything valuable.
> More specifically, another commenter in this thread says it's to make sure the user is aware of the configuration of a VPN which, if done maliciously, funnels all your traffic toa a hostile place.
I do not see how PIN protects the user, especially if user had PIN before installing a malicious VPN. Also, isn't Google Play supposed to check every application for malicious functionality?
jeroenhd 7 hours ago
That seems like a good trick to me if you want to prevent people from installing spyware without any obvious signs.
You can almost hide the warnings (there's one small notification in the bottom of the notification tray you can't disable) and on some phones even the VPN icon, but you can't hide the new lock screen code your victim suddenly needs to enter to use their phone.
It used to be that Android showed random popups and notifications about identified security risks, which were awfully annoying if you have a private CA certificate installed. Luckily Google got rid of those.
In my experience, you can also set up biometrics on basically every phone, and Google has a few "don't lock the phone while it's with you in your pocket" like services you can optionally enable as well. Your backup PIN doesn't have to be four numbers, you can put a whole passphrase in there if you want it to be secure.
You could also do facial unlock. Less secure than Apple's implementation but more than good enough if you didn't have any lock screen set before that.
exceptione 19 hours ago
> A proper fix would require changes in the Android system. The researcher who discovered the leak has reported the issue to the Android Vulnerability Reward Program, but according to the researcher the issue was closed without action. This issue is not public, but based on this information we deem it unlikely that Google will do anything about it. GrapheneOS is aware of the issue and are working on a fix.
jjav 18 hours ago
> we cannot rule out that Google deliberately introduced or wanted to keep the leak in place
I'd say a lot stronger than "cannot rule out". Regardless of how it was introduced, if it is now known and the issue was closed without action, they are actively choosing to keep it.
grapheneos 12 hours ago
Google considers VPN leaks to be valid bugs but unfortunately doesn't consider them security bugs. Internal issues are created for any issue report considered valid. The external one is only used to communicate with people. If it was filed as a security bug, they'll close it if it isn't considered within the scope of the bounty program.
gib444 16 hours ago
The GrapheneOS team did not respond to an email report either [0]. Does that mean we can draw similar conclusions from the GrapheneOS team? I don't think that would be fair or correct, so why assume malice from Google just based on the (lack of) response to the report?
N.B. I don't disagree there is a possibility of foul play on Google's part, but I think more evidence / better argument is required.
[0] https://github.com/GrapheneOS/os-issue-tracker/issues/8617#i...
nvme0n1p1 16 hours ago
There's a big difference between "the issue was closed" and "received no acknowledgment". The former is a deliberate action. The latter could be a case of SMTP-ate-my-email.
gib444 15 hours ago
Issue could have been closed by a mis-click, an AI bot gone wrong, a misunderstanding of the issue etc. You can't assert it was deliberate unless e.g. you work in the team that handled it and have inside knowledge. Agree GOS should have benefit of the doubt (too)
kennethkl 14 hours ago
your logic would assert a similar conclusion with this scenario:
a person walks up to you, punches you in the face, and leaves.
it could have been an accident, an AI bot, or a misunderstanding. definitely not deliberate.
grapheneos 12 hours ago
This is the email we received:
Hello
Check: https://news.ycombinator.com/item?id=49096839
Please upvote/comment/share/mitigate
We have a bunch of internally discovered VPN leaks which are already being worked on and this was added to that workload. We've already shipped a bunch of fixes and will ship more soon. We plan to eventually overhaul the whole system to prevent leaks in a much more systemic way.
nvme0n1p1 11 hours ago
Yep, that's a reasonable response. Thanks for your work.
exceptione 16 hours ago
GOS explicitly stated that they work on a fix, also for other issues and they keep this on their radar.
Google just closed the ticket, without communicating their plan to deal with it. I just stated that we cannot rule out a possibility of foul play, thereby keeping other options open. Keeping that thing in mind which is better known as "the reality" I would be a little bit more wary about Google's stance towards privacy than I would be about GOS though. The difference in how these parties are handling this issue is already a tell.
grapheneos 12 hours ago
Security issues considered outside the scope of what they consider a security vulnerability are closed regardless of what they plan to do about the issue. Google primarily uses internal issues to track issues with Android. Public issues and security issues filed by external parties are only used to communicate externally and an internal issue is created for their actual issue tracking.
A security issue being closed means you aren't getting a bounty and it won't be fixed for existing Android releases. It doesn't mean it won't be fixed in a future Android release. They do track VPN leaks as issues internally and regularly ship fixes in new major releases. They unfortunately don't consider those security issues so they don't get prioritized. If they were considered security issues, then they'd likely consider them Low or Moderate severity which means those wouldn't be backported.
Only a large subset of patches for High and Critical severity issues are backported to older releases of Android. Low and Moderate severity issues stopped having patches backported years ago due to volume. High and Critical severity patch backporting is now being scaled down too due to AI accelerated vulnerability discovery. You need the latest yearly or QPR2 release to get full updates.
GrapheneOS has had to fix a bunch of VPN leak issues and we're in the process of fixing more of the issues. We plan to heavily overhaul the VPN implementation to make most forms of leaks nearly impossible rather than continuing to use the current system prone to it.
nonamesleft 18 hours ago
As a quick kludge use an USB-C wlan network adapter that lacks the functionality for this type of connection (albeit that won't help you with a cellular connection)?
exceptione 18 hours ago
Regarding cellular connection, the proof of concept presented here only works on wifi: https://github.com/GrapheneOS/os-issue-tracker/issues/8617
I have a hunch this leak is bound to wifi hardware only, for details: https://supuk.ch/papers/android-natt-keepalive-vpn-bypass
aucisson_masque 21 hours ago
> This issue is not public, but based on this information we deem it unlikely that Google will do anything about it. GrapheneOS is aware of the issue and are working on a fix.
Good guy Google, as usual.
grapheneos 12 hours ago
dingdong2026 4 hours ago
Just another data point proving what we already know:
Google is Evil.
You might as well use Meta or Microsoft products. Or Phillip Morris. Blame yourself for the fallout.
potatoproduct 16 hours ago
Surprised this hasn't blown up more!
TutleCpt 16 hours ago
Mullvad did a really good job writing up this blog post. And yet again GrapheneOS to the rescue.
gib444 17 hours ago
I guess the best advice remains to only use wifi to connect to a router which forces traffic over a VPN and never use mobile data?
Do any similar leaks exists on iOS currently?
gib444 13 hours ago
GrapheneOS is affected too. They've been aware since at least 29th July and are working on a fix, no ETA.
GOS say security issues are high priority.
There is no update the GitHub issue for 2 weeks except for deleting a comment by the reporter yesterday.
GOS developers have been busy working on a Messages rewrite and that got released in alpha yesterday.
innocent_name 8 hours ago
>There is no update the GitHub issue for 2 weeks except for deleting a comment by the reporter yesterday.
Yeah, i was very confused by that, especially after they invited them to post publicly/privately. They love controlling the public communications when it comes to researchers. I remember ryrona, a guy who found VPN leaks, being censored for no reason whatsoever in their public GitHub issue tracker.
tosti 16 hours ago
You're definately not hiding something if all your traffic goes out to a single IP address and a single pair of source and destination ports.
gib444 14 hours ago
A business: hiding everything is expected. To do otherwise is negligence
An individual: you're a pedo if you use a VPN
Give over.
tosti 13 hours ago
Most people I know use a VPN do it to bypass geo restrictions and/or get a discount with cheaper currencies. (But hey, our "representatives" seem to disagree.)
ck2 8 hours ago
sometimes it's even more basic than that
some sites really really do not like my t-mobile wireless internet IP
I think it's because t-mobile uses a small pool of IPv4 but that's just a guess
I have to use cloudflare-warp to even get on their sites (it's a free VPN)
major sites too like adidas .com
orbital-decay 5 hours ago
Most people I know use a VPN to avoid censorship by several governments and non-governmental organizations targeting them at once.
folienumero 4 hours ago
What an useless comment, you have no idea about privacy or security don't you?