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Bitwarden PINs can be brute-forced

ambiso.github.io

11–20 of 284 posts

Re: Bitwarden PINs can be brute-forced

#11
The moral of the story here seems to be: if you want convenience you'll compromise your security. This is not exclusive to BW.

Or if you want a moral of the story specific to the article: Don't use the PIN feature in BW. And perhaps, instead of a PIN use a physical key (e.g., YubiKey).

Re: Bitwarden PINs can be brute-forced

#13
post #6

The silly thing is that Windows already has Windows Hello and its accompanying APIs which can be used to guard something like it with anti-hammering protections. Ditto for macOS and the Secure Enclave. I know it's not 100% of its market but using those two features could drastically improve security for the vast majority of people who pay no mind to things deep down in the weeds such as this.

Windows Hello and TouchID are supported according to this blog post: https://bitwarden.com/blog/introducing-desktop-biometrics/ Not every device has the necessary hardware, though; most desktops don't have it, so they would need to rely on external hardware such as USB keys. Furthermore, the demonstration video is clearly running on some kind of Linux/BSD system, where support for trust hardware is distinctly lacking…

> I don't know why you would bother with a PIN on your password manager. My guess is that it's a feature designed for mobile devices.

Note that on desktop Bitwarden allows PINs to be alphanumeric, and any length. I use a PIN because my master password is more than 20 characters and I don't want to type it every time I restart my browser. My PIN is a decently strong password in its own right, but shorter than my actual master password.

Re: Bitwarden PINs can be brute-forced

#15
post #5

It's a tricky problem, because on devices without biometric authentication I really don't want to type in my long master password every time! I think I'd appreciate an option such that: 1. If I'm online, I can unlock with a pin. Some critical piece of information would be kept server-side, and the server would limit unlock attempts. 2. If I'm offline and need access to my vault—which happens but not too often—I need…

You don't actually need biometrics, you just need a TPM to handle your pin-to-password function with an attempt limit.

Okay, but my laptop doesn't have that either.

Re: Bitwarden PINs can be brute-forced

#16
> However this 5 guesses limit is enforced completely within the client's logic: it relies on the attacker using the official Bitwarden client.

I'd guess a software engineer working on that part of a security system would probably consider that, while the implementation approach for that part was being decided.

If so, why did it happen anyway? Did they communicate the weakness to users?

Re: Bitwarden PINs can be brute-forced

#17
post #6

The silly thing is that Windows already has Windows Hello and its accompanying APIs which can be used to guard something like it with anti-hammering protections. Ditto for macOS and the Secure Enclave. I know it's not 100% of its market but using those two features could drastically improve security for the vast majority of people who pay no mind to things deep down in the weeds such as this.

Windows Hello and TouchID are supported according to this blog post: https://bitwarden.com/blog/introducing-desktop-biometrics/ Not every device has the necessary hardware, though; most desktops don't have it, so they would need to rely on external hardware such as USB keys. Furthermore, the demonstration video is clearly running on some kind of Linux/BSD system, where support for trust hardware is distinctly lacking…

>Not every device has the necessary hardware, though; most desktops don't have it, so they would need to rely on external hardware such as USB keys.

How?!? There's been an fTPM built into CPUs since Haswell on the Intel side and on the AMD side since before Ryzen. If you OEM it's enabled automatically if you bought a machine after July 28, 2016. If you DIY you literally have to flick one switch in the BIOS if it's not enabled automatically.

Re: Bitwarden PINs can be brute-forced

#18
post #6

Earlier quoted context omitted.

Windows Hello and TouchID are supported according to this blog post: https://bitwarden.com/blog/introducing-desktop-biometrics/ Not every device has the necessary hardware, though; most desktops don't have it, so they would need to rely on external hardware such as USB keys. Furthermore, the demonstration video is clearly running on some kind of Linux/BSD system, where support for trust hardware is distinctly lacking…

>Not every device has the necessary hardware, though; most desktops don't have it, so they would need to rely on external hardware such as USB keys. How?!? There's been an fTPM built into CPUs since Haswell on the Intel side and on the AMD side since before Ryzen. If you OEM it's enabled automatically if you bought a machine after July 28, 2016. If you DIY you literally have to flick one switch in the BIOS if it's no…

Intel only added PTT - their soft TPM - with Coffee Lake.

Re: Bitwarden PINs can be brute-forced

#19
The problem is these password managers are lucrative targets, especially being able to gain access to a person's financial accounts. Simply disregarding the issue and categorizing it as "Attacks requiring physical access to a user's device" isn't good enough. Yes, there's only so much Bitwarden can do from the software side of things, without hardware support to back it up. But Bitwarden should still do what it can to mitigate such attacks, such as significantly increasing the number of PBKDF2 iterations for PINs (at least stored on disk; a key could be cached in RAM with fewer iterations because RAM is far less likely to be compromised than files on disk), and discouraging (or even preventing) users from using short PINs that could be quickly brute forced.

Re: Bitwarden PINs can be brute-forced

#20
The author mentions this finding was marked as out-of-scope when they reported it to Bitwarden. A couple of categories that are considered out-of-scope are listed, namely: attacks requiring physical access to a user's device, and "other side of airtight hatchway"[0] type issues.

The latter seems reasonable, if the assumption is that the device is fully compromised, and ongoing surreptitious monitoring of user activity by an attacker is occurring.

However, users probably have the reasonable expectation that if their laptop is stolen, their device-local vault data(supposedly encrypted on disk) is not compromised as a result. Bitwarden should either disallow weak pins/pin-access altogether, or they should caveat more clearly the weaknesses of pin-only access to device-local vault data.

[0]: https://devblogs.microsoft.com/oldnewthing/20060508-22/?p=31...

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