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Bitwarden PINs can be brute-forced

ambiso.github.io

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Re: Bitwarden PINs can be brute-forced

#91

Post by SV_BubbleTime »

FfejL wrote: post #89

"Let's now assume that the user enables the PIN unlock and configures Bitwarden so that it doesn't require the master password on restart." If the user has setup Bitwarden so the master password is not required, then the user gets what they asked for, namely a password database secured by a 4 digit PIN. Not clear to me why this is a problem Bitwarden needs to fix.

They could make the pin process intentionally slow… maybe with some number of iterations… and as computers get faster they can just update the number of iterations required…

Re: Bitwarden PINs can be brute-forced

#92

Post by mynameisvlad »

generalizations wrote: post #84
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.

Does the TPM limit retries or something? If it's a 4-6 digit number, you can just count upwards and try them all in a trivial amount of time.

Yes.

https://www.dell.com/support/kbdoc/en-us/000142311/tpm-failu...

Re: Bitwarden PINs can be brute-forced

#93

Post by kadoban »

generalizations wrote: post #84
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.

Does the TPM limit retries or something? If it's a 4-6 digit number, you can just count upwards and try them all in a trivial amount of time.

> Does the TPM limit retries or something?

Yes.

TPMs have weaknesses, so this probably isn't a 100% guarantee depending on the attacker and the exact hardware, but it's pretty reliable (and very reliable if your attacker is reasonably small).

Re: Bitwarden PINs can be brute-forced

#94

Post by bkettle »

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

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.

Re: Bitwarden PINs can be brute-forced

#95

Post by mynameisvlad »

poisonborz wrote: post #58
d-z-m wrote: post #36

Earlier quoted context omitted.

Indeed, which is why Bitwarden should disallow pin-only access for offline vault data altogether. Admittedly, I'm valuing a safe interface for users much more highly than one that is convenient or ergonomic.

It's the user's choice.

I mean, sure, but if the user isn’t appropriately informed of the risks (such as this attack) how would you expect them to make a good choice?

Re: Bitwarden PINs can be brute-forced

#96

Post by organsnyder »

Semaphor wrote: post #80
hn_throwaway_99 wrote: post #72

Earlier quoted context omitted.

Lots of people, perhaps the majority, still use master passwords that don't have a ton of entropy. For example, the bad guys that stole the LastPass vaults have definitely cracked a lot of the vaults that were protected with weaker master passwords. 1Password's approach is definitely the right one here, where the master key is basically a combination of the user's master password and a random 128 bit (I think it's 12…

I’d bet (though in all fairness, only a low amount ;)) the intersection between a user that has both a weak master password and attackers willing to spend a ton to rent a GPU farm is pretty low, though.

Eh... plenty of people with weak security hygiene also have high-value credentials.

Re: Bitwarden PINs can be brute-forced

#97

Post by lucb1e »

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 4-digit number with unlimited attempts available is not a downgrade attack but a brute-force attack https://en.wikipedia.org/wiki/Brute-force_attack

Re: Bitwarden PINs can be brute-forced

#98

Post by grapesurgeon »

d-z-m wrote: post #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 activit…

[dead]

Re: Bitwarden PINs can be brute-forced

#99

Post by hnarn »

d-z-m wrote: post #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 activit…

> 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.

If you’re using a four-number pin to encrypt your data with no additional “padding” around that PIN, that is not a reasonable expectation.

However, I also don’t think that it’s reasonable that Bitwarden allows weak passphrases to begin with.

Re: Bitwarden PINs can be brute-forced

#100

Post by morpheuskafka »

SV_BubbleTime wrote: post #91
FfejL wrote: post #89

"Let's now assume that the user enables the PIN unlock and configures Bitwarden so that it doesn't require the master password on restart." If the user has setup Bitwarden so the master password is not required, then the user gets what they asked for, namely a password database secured by a 4 digit PIN. Not clear to me why this is a problem Bitwarden needs to fix.

They could make the pin process intentionally slow… maybe with some number of iterations… and as computers get faster they can just update the number of iterations required…

If the PIN is local, only a secure element type of chip could meaningfully enforce this restriction. Otherwise, whatever memory or disk stores the secret encrypted only by the 4-digit PIN could still be brute forced. Just disabling entering a PIN in the UI would not be enough for security.
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