> If a victim logs into a fake Google site, the phishing site passes on their username and password to the real Google login page. Then the spoofed site passes back Google's request for the user's U2F token and collects the Yubikey's unique answer, all via WebUSB. When that answer is then presented to the real Google site, the attackers gain access to the victim's account.
So basically they are somehow able to trick the yubikey neo into accepting a challenge from a different domain, by using the webusb API.
Reading further:
> The technique would only work with U2F keys that offer protocols for connecting to a browser other than the usual way U2F tokens communicate with a computer, known as the Human Interface Device or HID, which isn't vulnerable to the attack. The Yubikey Neo, for instance, can also connect via the CCID interface used by smartcard readers
> An assumption was made by Chrome that all U2F is HID, which doesn't hold for the Neo, whereas Yubico made an assumption that USB will never be accessible by web pages directly
So:
- Don't use a Yubikey Neo anymore
- Don't use Chrome
- Don't use U2F because FireFox doesn't support it
- Never use your yubikey because hardly anything supports it
Sigh
It does! Open about:config and switch security.webauth.u2f to true. It'll Just Work.
I've in the recent past modified a barebones Perl webapp to try and understand U2F better, see https://u2fdemo.darkpan.com/
I've been able to log in / use U2F from:
* FF on Windows and OSX
* Chrome on Windows, OSX
* Chrome on Android using either a OTG cable for a U2F USB key, a Bluetooth U2F key, and a NFC U2F key (works if you install Google Authenticator)
* Unfortunately, not FF on Android as I can't find how to enable U2F there yet :/
Speaking of which, why does Vanguard force you to still have SMS two factor available even when you add a U2F device...
Unfortunately for a large number of users that effectively means it doesn't work.
Which key did you use? I tried Yubikey 4 (via OTG cable) and 4C (directly) and the U2F flow with Authenticator did not work (just like the key would not be recognized for U2F).
but still hardly anything supports U2f :-(
I think WebUSB will enable a lot of cool things, though it will definitely be hard to sandbox.
I want to program an Arduino from a web IDE. I want to control a 3d printer or pen plotter from a web application. I want to store things on a flash drive on my iPhone using a web-based file explorer? This last one sounds strange.
On a tangent, I see application runtimes moving into the browser by default with very few performance-critical applications remaining outside that stack. Photoshop and AAA games might be exceptions. Services like databases and web browsers would not have a need to be in Chrome.
(don't hurt me, I know I'm strange.. ~)
Originally the scale was connected via serial port to the desktop. A little Perl service we called "the scale daemon" exposed the current weight on some localhost port. The backend would constantly poll that service and the web browser would poll the backend to keep the value on the page up to date. It was a nifty solution albeit a bit clumsy and it meant running an extra piece of software on 50+ machines in a warehouse.
At some point our scale vendor stopped selling scales with serial connections or maybe it was that the PC vendor stopped including serial ports. It was 10+ years ago and I can't recall exactly. What I do remember is that the guy that wrote the scale daemon had moved on and I had to figure out how to make it work with USB. It was fun and probably not as hard as it seemed at the time, but wow, being able to get at that scale from inside the browser would have massively simplified things.
So don't do that. It would be nice to know exactly what this dialog looks like, but it seems low risk?
How about you tell users to simply not enter their password into phishing sites?
When users want to do something (sign in) and there are instructions on the page telling them to do something (enter password or accept usb) then the users will do it.
I wish more websites offered the option to use it.
So does Chrome ask for permission to allow USB access? Or maybe there's something about this I'm not getting.
While I understand the reasoning behind that move, I'm not sure I fully agree with it. I don't think users will necessarily understand the implications of granting a site access to a device that wasn't designed with attacks from malicious code as part of its threat model. At the very least, the wording on the permissions dialog should be changed to indicate that the user is granting the site _full control_ over the device they're connecting it to.
Unfortunately though, as with any phishing attack, this flaw is most likely to be effective against uninformed users, and those users are the least likely to take proactive measures to protect themselves beforehand.
Fortunately:
> "We will have a short term mitigation in place in the upcoming version of Chrome, and we're working closely with the FIDO Alliance to develop a longer-term solution as well."
If, when logging in, you see a big modal dialog asking if you want to grant webusb access to the site, then DONT select your yubikey out of the list of connected USB devices and click "Allow".
As long as you can convince yourself to avoid taking that particular unusual action, it sounds like you're fine.
Upon registration, the server also collects a nonce, which is used for verification[0]. The attackers would need to get that nonce from the site. Hopefully, the site disables CORS so a phishing site cannot request a challenge.
Lastly, on Linux (I know, a minority), you need to make an entry in rules.d[1] to even allow Chromium to access USB devices.
I can see how this potentially maybe could catch someone, but I don't see it as much of a risk.
[0]: https://blog.fastmail.com/2016/07/23/how-u2f-security-keys-w... [1]: https://developers.google.com/web/updates/2016/03/access-usb...
While its obviously not a total solution, I do think that maybe the permissions prompt should be a bit more scary: https://developers.google.com/web/updates/images/2016-03-02-...
I'd rephrase that to something more along the lines of "example.com wants full control of". Maybe with an option for device manufacturers to opt-in to support for WebUSB, allowing for protocol enhancements to improve security and a less scary permissions prompt.
>The attackers would need to get that nonce from the site.
The attackers have their own machine with a browser running on it that visits the real site and gets the nonce, then hands that nonce to the victim to be signed by their key.
Or (my assuption) it might be for devices that cannot work without browser and network connection.
[1] https://developers.google.com/web/updates/2016/03/access-usb...
WebUSB terrifies me.
Are there any good writeups about security of different web browsers?
is Chrome a real issue?
As for Chrome being a real issue, some points off the top of my head: - Its extension store breeds out malware in regular intervals (feels like there's headlines about that at least every other month). - Pretty bad autofill exploit that was left unfixed for years: https://github.com/anttiviljami/browser-autofill-phishing (Might've been fixed in the past year, I haven't checked, but I doubt it.) - Chrome Sync is not end-to-end-encrypted without the use of a second password, which effectively means that it is unencrypted for 99.9% of Chrome users. Google also actively uses this data, weaving your browsing history into the profile that they keep of you. So, if they ever have a data leak, a lot of data is going to come from people using Chrome, too. The NSA/CIA/FBI also tap into this data, possibly using it for cyber war attacks, so if you live in a country other than the USA, you're making yourself a prime target and an easy target by inputting this data through Chrome.
Sure, it's vulnerable to the man behind your back. But if such threat exists, you shouldn't type your password anyway.
It looks like this vulnerability is limited to Chrome at the moment. Good to know if using Chrome (or even Epichrome for SSBs) when doing things like online banking.
Yubikey 4 allows openPGP keys as well as OTP Yubikey functionality, making it half HSM/half token. the FIDO keys offered by Yubi only do asymmetric cryptography.
OTP is regularly phishable, not requiring any webusb. Before this webusb attack, u2f was unphishable.
I'm curious (assuming even) that it could be subject to this exploit?
It should be just as if you unplugged your u2f device from your machine and plugged it into the attacker's machine.
On the other hand, it's basically functioning as another keyboard device and not a special USB device so it shouldn't be that surprising, right? (serious question)
Haha it's funny you put it this way because actually it's Firefox that implements FIDO U2F standard correctly and Chrome is not. Chrome uses low level API to communicate with their built in extension and the high level shim that they provide is not 100% spec compliant.
Google did not bother to use the U2F correctly on their accounts site, Github for example did it correctly and their 2FA works on any browser (that is FF and Chrome).
Unfortunately, these same companies often then claim that there is no harm in SMS two factor since "clearly it is stronger than one factor". But they are blind to their own systematic design flaw which is that the same SMS setting to enable two factor also usually enables one-factor password-recovery via this supposedly trusted phone.
Given what we know about SMS security, it is pretty obvious that one-factor SMS is weaker than one-factor good strong password. And if the good strong password can be merrily reset by whomever hijacks your phone, you have really just decreased your security posture while performing this whole security theater around two-factor and hardware tokens.
Not to mention that traffic inside the network is not encrypted so a lot of parties have legitimate access to the messages anyway.
I understand your point but SMS should not be used as the only factor for authentication.
You only need to hijack the victim's phone number so that messages are sent elsewhere. This can be done by technical or social hacks such as porting the subscriber's number to a new provider or pretending a phone was lost and having the phone company register a replacement SIM. There is no need to physically intercept the victim's phone, so it is not in fact a second factor.
Firefox is compliant.
I am kind of surprised that the sites you mention can implement the spec correctly but Facebook and Google can't.
In this case, though, what happened is that Google implemented a different, earlier version of the spec than most everyone else. Mozilla is busy implementing that spec as well to bridge the gap.
I'm not surprised.
I supposed you could trick them by saying that the login process has changed and they need to enable WebUSB to let their YubiKey work
https://www.yubico.com/about/reference-customers/department-...
This phishing attack removes the benefit that Yubikeys provided.
Sure a smart users can decline the permission prompt. But a smart user can also simply not enter their password into phishing pages.
There is an enormous need for some solution resistant to users who aren't good at identifying legitimate vs phishing sites. U2F as it stands is the only practical and deployed solution to that problem. It's infuriating that chrome broke this security promise to compete with microsoft.
In this case it's not even an exploit really; more like social engineering. (Tricking users into granting the phishing site unrestricted access to their Yubikey, then using that access to trick the user into authenticating a login session for the phishing site.)
A browser is more secure than Qubes?
The flaw is in legacy software, not in what is possible. Had humanity spent the effort that was spent on browsers on operating systems instead, we'd have had the same security improvements without all the negatives.
I see nearly no good reason for any of those uses to be web-based, and certainly not with hardware control! If you want to store files on your flash drive, the browser should handle that, not give out direct usb access...
Hearing this exists was a shock, like when the first Android 'Instant' load app showed up on my phone (apps that you don't install, but run themselves if you goto a website or a physical store, and without asking you)
EG, take a few seconds to turn on a flag in configuration, or add a plugin.
Getting 400 students up and running with python is painful alone - without USB. For projects, some small fraction of those used USB, and we again had a pretty good chunk of time spent getting them all working.
What if your unsandboxed native USB utility has an RCE vulnerability?
It comes down to this: if you ever found yourself in a situation where you needed to connect a USB device to a remote service, would you prefer to download that service's unsandboxed native code to your PC and execute it? Or execute some JS in the browser sandbox and grant it limited access to that one specific device?
I have never found myself in that situation. That sounds like a really silly idea.
For those that _do_ require [such use cases][1] though; they can now do so without needing to expose their system to an unsandboxed native app.
The web is a disaster and WebUSB is a prime piece of evidence supporting this.
While obviously we want to do as much as we can to discourage users from shooting themselves in the foot, there are limits. At some point, eventually you _do_ have to trust that the user knows what he's doing.
Giving users a choice on when to allow a page access to one specific USB device is not a "disaster".
