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Bitwarden PINs can be brute-forced

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Re: Bitwarden PINs can be brute-forced

#151

Post by cryptonector »

intelVISA wrote: post #69
ericpauley wrote: post #59

Earlier quoted context omitted.

Using a TPM: https://en.wikipedia.org/wiki/Trusted_Platform_Module

TPM interdiction is readily possible.

If you have a key object that is not extractable and can only be used and it is password protected, then you can't bypass the TPM. Once the key is unlocked (if you have access to the relevant session, which, you would) you can use it, which is bad enough if the rest of the system is compromised. There's also a concept of restricted keys that can only be used for things like quote signing (for attestation), or credential activation, which means the user doesn't get to specify exactly what to sign or decrypt.

If you couple all of that with running golden/blessed firmwares and OS, and you do secure boot, then you can be pretty certain (early in boot time anyways) that you're not running firmware/software you didn't want to assuming those are not themselves compromised.

Now, for local storage keys you really need those to be in software as a TPM can't perform well enough (not even an fTPM), and even if they did, an attacker could just decrypt local storage w/o having access to the raw keys as long as they can compromise your OS.

So, in a way you're right. But a TPM would still give you something that software-only solutions wouldn't: you get to refuse to enter the password and then the attacker has no choice but to apply rubber hose attacks or mount more expensive attacks on the TPM itself.

Re: Bitwarden PINs can be brute-forced

#152

Post by eviks »

The name is part of the problem You can have shorter alphanumeric password per device for frequent unlocks, it doesn't have to be your typical 4 number PIN that jumps to mind It would not offer the same protection as your main much longer password, but then that longer password protects against a bigger threat than local access, and it's still much more convenient (and not much less inconvenient vs the 4 digit PIN, like on a full computer keyboard typing a longer word is faster than shifting your fingers to the top numbers row)

And it would be nice if password managers explains the much much bigger risk of these very short numbers-only poorly named PINs so that users can make an informed decision

Re: Bitwarden PINs can be brute-forced

#153

Post by cryptonector »

lucb1e wrote: post #81
intelVISA wrote: post #69

Earlier quoted context omitted.

TPM interdiction is readily possible.

I web searched it and found a dedicated wikipedia page https://en.wikipedia.org/wiki/Interdiction but I still can't figure out what TPM interdiction is supposed to mean Anyway if a TPM was trivially bypassable then there would be no point to having them so I'm doubtful of whatever this off-hand comment is supposed to mean

TPMs are not 'trivially' bypassable. There's attacks on how they're used, naturally, but those wouldn't apply in this case. In this case the main issue is that once you've unlocked your storage keys you get to use them, and since storage keys need to be software keys to perform acceptably, you could even steal them. But if your device is off, a TPM would be more than adequate to protect local storage.

Re: Bitwarden PINs can be brute-forced

#154

Post by eviks »

progbits wrote: post #140
asveikau wrote: post #126

Earlier quoted context omitted.

They could make it take more time to derive a key from a pin. That would make it more difficult to brute force.

The pin space is just too small. What's the longest an user is willing to wait? 10 seconds? Times 10k that is just 27 hours. Spend a couple of bucks on a few beefy EC2 instances and you crack that in an hour or two.

It's not too small, your not limited to just numbers in your PIN on a computer

Re: Bitwarden PINs can be brute-forced

#155

Post by jvdvegt »

duxup wrote: post #70
NoZebra120vClip wrote: post #56

Earlier quoted context omitted.

In the case of Windows Hello, a PIN is very different from a password (such as your live.com password). PINs are encrypted per-device, and are never transmitted from the device. They are resilient against rainbow table brute-forcing, and they generate asymmetric cryptographic key-pairs by using the device TPM. So forget what you know about ATM PINs; this is a markedly different concept.

TIL Thanks, when windows moved to the PIN I was wondering how that worked/ they kept it secure but still easy to login.

Indeed! They should have explained this much better when it was introduced.

But of course, Windows PIN was only needed when they made a local login a login to your Microsoft account, so your local password was suddenly transmitted to the internet.

Re: Bitwarden PINs can be brute-forced

#156

Post by cryptonector »

monocasa wrote: post #108
bkettle wrote: post #94

Earlier quoted context omitted.

I think they are talking about the definition under the Espionage section, i.e. a hardware supply chain attack: > The term interdiction is also used by the NSA when an electronics shipment is secretly intercepted by an intelligence agency (domestic or foreign) for the purpose of implanting bugs before they reach their destination.

I read the original comment instead about sniffing the data path between the TPM and the user to get the PIN.

You can encrypt sessions to the TPM. To do that you need to securely know a public key for the TPM.

The protocol spoken to a TPM is like a micro-TLS. You get to encrypt, or not. You get to authenticate the TPM (like a server), or not. You get to do ephemeral-static key exchange (unlike TLS 1.3, which wants ephemeral-ephemeral key exchange). And you get to do PSK (password), and you get to do it in ways that are not subject to off-line dictionary attacks by eavesdroppers.

But you don't have to do encryption or authentication of the TPM, and the easiest thing to do is not to do either, which is what much software does. There's been this assumption that if it's on the motherboard, you can't mount active -or even just passive- attacks, but that is very much not true.

I really did not know what to read into the "TPM interdiction" comment in the context of bitwarden, but I've left comments elsewhere in this sub-thread.

Re: Bitwarden PINs can be brute-forced

#157

Post by jeroenhd »

capitainenemo wrote: post #37
jeroenhd wrote: 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…

I'm not sure what qualifies as "lacking" but fingerprint unlock is definitely a thing in Linux. I set it up on my IBM laptop over a decade ago. These days, the interface even appears to have improved somewhat, to the point where there's nice GUIs and everything. https://help.ubuntu.com/stable/ubuntu-help/session-fingerpri... Also, dongle support is pretty good for things like java PIV cards and yubikeys. I've success…

Fingerprints work great in modern Linux distros (I use them for sudo and sometimes unlocking my display), but the fingerprint hardware and the TPM don't seem to talk to each other. Windows Hello (and I presume TouchID) is set up to handle authentication and authorization together in one well-secured kernel blob with all kinds of TPM trickery to ensure security.

The Linux version of this process, at least as far as I could find so far, consists of identifying and authorizing the user alright, but the TPM's secret management seems to be handled by an entirely different system.

This means that brute-forcing or other attempts at access don't need to go through the biometric system on Linux whereas Windows Hello is more tightly protected against malware like that.

Dongles do work great! With WebAuthn/FIDO(2) we can hopefully soon start to let go of password managers completely. Passwords are useful but passwordless authentication is just better for most single factor authentication mechanisms in my opinion.

Re: Bitwarden PINs can be brute-forced

#158

Post by cryptonector »

Veliladon wrote: post #17
jeroenhd wrote: 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…

I'm not sure if fTPMs have endorsement key certificates. I should know, but mostly I work with dTPMs and vTPMs. Not that an fTPM not having an EK certificate is a big deal -- if you bootstrap a public key for it early enough in OS installation, you can just trust the fTPM.

Re: Bitwarden PINs can be brute-forced

#159

Post by 1attice »

lucb1e wrote: post #97
1attice wrote: post #75

Well, there goes my trust in another old friend. That's a downgrade attack for sure.

> That's a downgrade attack for sure. "... is a form of cryptographic attack on a computer system or communications protocol that makes it abandon a high-quality mode of operation (e.g. an encrypted connection) in favor of an older, lower-quality mode of operation (e.g. cleartext) that is typically provided for backward compatibility with older systems." from https://en.wikipedia.org/wiki/Downgrade_attack Guessing a…

Allowing people to choose an insecure means of securing their work just is a stochastic downgrade attack.

Think it through.

Re: Bitwarden PINs can be brute-forced

#160

Post by cryptonector »

Wowfunhappy wrote: post #15
_cenw wrote: post #5

Earlier quoted context omitted.

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.

How old is your laptop?
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