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Flaws in deterministic password managers

tonyarcieri.com

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Re: Flaws in deterministic password managers

#91

Post by CmdrSprinkles »

Retr0spectrum wrote: post #39

I have an irrational(?) fear of vault password managers. I see it as a single point of failure. Furthermore, the more "useful" they become, with browser extensions etc., the greater the attack surface becomes. Because of this fear, I generate random passwords and memorise them, which is not ideal.

I have a similar fear of a lot of stuff like that

So I just use keepass (synced on spideroak, although I am considering alternatives as they still can't be arsed to do 2FA and I am still sceptical of some of their claims). No browser extension, just the app on my PC (and phone).

If it is a site I use regularly, I actually know the password because I generate it in a memorable way. if it isn't, I unlock the database, find the entry, copy it, and paste it.

To be compromised, I need:

1. My device to already be compromised, at which point I am boned anyway

2. Someone to get a hold of the database through stealing my device: I would know about this and would take action for the more sensitive passwords while filing a police report. The hope is that it would take long enough to compromise the database that I would have time

3. Someone to compromise spideroak and get the database. This is my big worry right now as I won't know about this (see my concerns over spideroak), but I put this in the "it is worth the risk" category as it avoids desync between my devices. But, as mentioned, I am looking in to alternatives or at least an extra layer of security/encryption to add in between.

Re: Flaws in deterministic password managers

#92

Post by gabemart »

stouset wrote: post #73
Gruselbauer wrote: post #45

Earlier quoted context omitted.

For me it was a case of thinking I know better. As in, "no way I'm giving you my passwords" and "who knows how tight their opsec is" ... never even tried anything like LastPass or 1Password until six months ago. Now I cannot imagine going back. My LastPass subscription is among the most vital services I pay for and the sheer freedom of having to remember one diceware-style master password instead of maintaining my ow…

> For me it was a case of thinking I know better. I'm deeply curious: why ? When virtually every reputable security practitioner on this site and others has echoed the advice to just use a password manager for years, how do you come to the conclusion that you know better than them? If it sounds like I'm asking judgmentally, please don't interpret it that way. Your experience mirrors that of many others, and if I can…

>I'm deeply curious: why? When virtually every reputable security practitioner on this site and others has echoed the advice to just use a password manager for years

I think the disconnect is "perfect use" vs. "typical use".

With perfect use, generating a unique passphrase for each service and storing it only in your head is more secure than using any kind of remotely-syncing password manager. It's also more convenient - wherever you are, whatever you have with you, so long as you have an internet connection you can identify and verify yourself. You don't need your phone or an app or anything else.

With typical use, people use weak passphrases, reuse passphrases and forget passphrases, so using a remotely-syncing password manager is more secure, even if it's less convenient.

Some people (possibly wrongly) think they can achieve close enough to perfect use that they're better off not using a manager. Security experts know that virtually no one can achieve perfect use, so they recommend using a manager (which is almost certainly the correct advice to give to a wide audience).

But your apparent absolute confidence in the superior security of password managers, especially closed-source cloud-based password managers, seems to me to be overplaying your hand a little. The failure mode of a closed-source cloud-based password manager, even if very unlikely, is absolutely catastrophic.

Re: Flaws in deterministic password managers

#93

Post by tempestn »

mhaymo wrote: post #87
pwinnski wrote: post #26

Today I learned that many people on Hacker News have really insecure web security practices. :( I don't understand the resistance to using a vault-based password manager. Is it inertia? I mean, if you're using the same one or two passwords on every site, then sure, it may not seem worthwhile to us 1Password. But then, enough password hashes have been leaked this year alone to suggest that you need to do something bet…

I do use a vault-based password manager (KeePass), but investigated using a deterministic one out of fear of losing my database, a risk which is avoided by using a memorable algorithm to generate passwords instead.

Wouldn't good backups be an easy way to deal with this risk? Presumably you have plenty of other data that you wouldn't want to lose (photos is usually the big one), so you need a solid backup plan regardless.

Re: Flaws in deterministic password managers

#94

Post by tempestn »

eridius wrote: post #16
ythn wrote: post #10

Earlier quoted context omitted.

> Worse, an attacker who sees one of your passwords has a pretty decent shot at brute forcing the rules you use, and an attacker who sees two of them has the rules and has totally cracked your scheme. If an attacker is specifically targeting me and thinking about my passwords, there's not much I can do at that point. Password security in general kind of relies on attackers scanning huge quantities of credentials and…

1Password isn't a web-based password manager, it's an offline one that has a syncing component. Syncing is traditionally done either over WiFi (so no exposure to attackers), Dropbox, or iCloud. More recently 1Password now has an optional subscription model that gets you syncing + all updates to the app on all platforms. But the new built-in syncing uses a separate Account Key, which you provide along with your master…

Even for a cloud-based manager like Lastpass, you would have 2FA turned on, so an attacker with just your master password still wouldn't be able to log in. (Although obviously you would still change the master password if it were compromised.)

Re: Flaws in deterministic password managers

#95

Post by tempestn »

ythn wrote: post #12
zeveb wrote: post #9

Earlier quoted context omitted.

A password like that would probably be guessed by a good password cracker pretty quickly. I've taken the liberty of following your procedure for an un-named domain. If anyone's got a password cracker running, I'd be interested how long it takes to break this SHA256 hash: dae640f98b6894d2f6eab5755b22918be46b0d219ea10d3ceea06ebe538a75d1. Post once you've guessed it. Just use 'pwgen -s 22'; it generates 128-bit password…

I too am interested to see how long it takes assuming the attacker knows the generator ruleset (which he will have had to work out previously from two plaintext passwords of mine). Still, I don't think it's that easy to figure out the ruleset of a good password generator if you make it obscure enough. For example: Amazon: NovemberAlphaies12# Facebook: KiloFoxtrototto16& What's the ruleset? Answer: Phoenic alphabet of…

Seems like kind of a lot of work to go through every time you want to log onto a site too, compared to just copying and pasting from your vault. (Or using a browser plugin, depending on your personal convenience/security trade-off preference.)

Re: Flaws in deterministic password managers

#96

Post by stouset »

gabemart wrote: post #92
stouset wrote: post #73

Earlier quoted context omitted.

> For me it was a case of thinking I know better. I'm deeply curious: why ? When virtually every reputable security practitioner on this site and others has echoed the advice to just use a password manager for years, how do you come to the conclusion that you know better than them? If it sounds like I'm asking judgmentally, please don't interpret it that way. Your experience mirrors that of many others, and if I can…

>I'm deeply curious: why? When virtually every reputable security practitioner on this site and others has echoed the advice to just use a password manager for years I think the disconnect is "perfect use" vs. "typical use". With perfect use, generating a unique passphrase for each service and storing it only in your head is more secure than using any kind of remotely-syncing password manager. It's also more convenie…

> But your apparent absolute confidence in the superior security of password managers, especially closed-source cloud-based password managers, seems to me to be overplaying your hand a little. The failure mode of a closed-source cloud-based password manager, even if very unlikely, is absolutely catastrophic.

In fact it's you that's overplayed your hand.

Open-source vs. closed-source is a red herring. Did you download compiled binaries published by the authors of an open source project? Would you be able to tell if they had published backdoored binaries that didn't match the source? Would you be able to tell if they cleverly added backdoors to the source code itself? You might argue that such deception would eventually be discovered. Maybe, but by then the "catastrophic" scenario has already unfolded.

Similarly, if you're downloading and running a third-party deterministic password manager, open-source or not, you're giving the author of that project the ability to run arbitrary code on your machine. Unless you're running it in a container with no network access or access to storage, the failure case is identical — regardless of what the software claims to do on the label, it may do something wildly different (e.g., send all of your passwords to the author).

Re: Flaws in deterministic password managers

#97

Post by problems »

countingteeth wrote: post #83
problems wrote: post #51

Earlier quoted context omitted.

Yes. If you want to see how vulnerable you are to this sort of attack, Nirsoft ships a good tool called WebBrowserPassView: http://www.nirsoft.net/utils/web_browser_password.html Be aware, this may be detected as malware or a "hacking tool" by your AV for obvious reasons.

How is this to supposed to show "how vulnerable you are to this sort of attack"? This runs standalone. 1. As a general rule, if you download and run an untrusted standalone program, it could probably steal your passwords even if you use a password vault (although that would certainly make it a little bit harder). 2. You can just go into the Chrome password manager and click "show" to see any stored password. No tool…

Yeah, this is not an attack itself, just one of the most common post exploitation routes to easy profit. So common that if you have amateur people who try to pirate things, cheat at games or click on the big flashing red banner ad, they're almost certain to come across it and they're almost certain to have common accounts stolen.

Using even a separate password manager, even an integrated one like LastPass raises the bar beyond this extremely basic level and takes it from easy target to medium target, eliminating every common stealer malware I've seen. This definitely doesn't rule out targeted ones of course, like you say, on an objective level there doesn't seem to be much of a difference. At a practical level though based on what's in the wild for non targeted attacks, it's huge.

Re: Flaws in deterministic password managers

#98

Post by Ntrails »

pwinnski wrote: post #26

Today I learned that many people on Hacker News have really insecure web security practices. :( I don't understand the resistance to using a vault-based password manager. Is it inertia? I mean, if you're using the same one or two passwords on every site, then sure, it may not seem worthwhile to us 1Password. But then, enough password hashes have been leaked this year alone to suggest that you need to do something bet…

I literally cannot be bothered. There are 3 kinds of sites:

- Important - Useful - Trash

Trash sites all use pretty much the same password. It's terrible but who cares?

Useful sites all use a standard root with prefix/suffix

Important sites (basically my email since that's the unlocker to everything else) just has it's own unique.

I imagine an attacker could probably post rude things on my linkedin and steal my neopets account? It's a downside risk i'm willing to take in exchange for not having to flick into another program which I have to install on all my devices etc etc etc.

When the government comes for me I'm screwed anyway

Re: Flaws in deterministic password managers

#99

Post by problems »

whyagaindavid wrote: post #81
problems wrote: post #34

Earlier quoted context omitted.

Which is bad. I've reverse engineered script kiddie malware far too many times to find them shipping "iStealer" and similar, which basically just dump browser password stores and send them to a gmail or FTP account. Often these pieces of malware include the SMTP credentials to the same gmail account or FTP access to download the results. And having seen their results, let me just say, these script kiddies can do damn…

I thought browsers store password s encrypted. I use Firefox sync that encrypts and uploads passwords. Do u mean this is also vulnerable? Thx

We're talking about different things:

- Firefox Sync is not vulnerable in the sense that Mozilla, nor any attacker can read your passwords while they're on the wire or on Mozilla servers. Passwords are encrypted client-side only and are effectively unbreakable between your devices assuming your master password is secure.

- The Firefox browser password store is only encrypted if you use a separate master password to unlock your saved passwords each and every time your browser starts up. This master password would defeat the majority of script kiddie malware, but not a targeted attack, similar to separate password managers. However, it's also a real pain, no one wants to have to type all that extra stuff, so they just use the default - remembering passwords without a master password. Even if you use Firefox Sync, your passwords still get sync'd into this store. Firefox Sync keeps them safe everywhere between your devices, but not on your devices.

- If your Firefox password store has no master password set, that means that the Firefox browser must be able to read your passwords from it. They can (and do) encrypt it all they want, but ultimately all it takes it a little bit of reverse engineering to decrypt it, because the key needs to somehow be accessible to Firefox, that means that to read your passwords, malware simply needs to duplicate what Firefox does.

Re: Flaws in deterministic password managers

#100

Post by hackuser »

Gee19 wrote: post #78
hackuser wrote: post #64

Earlier quoted context omitted.

> This is only true for cloud based password managers I agree, in the sense that one successful attack on the supposed centralized database containing all user credentials would have a high ROI. But it also applies to local password managers. If 20 million people use the same password manager and I have an exploit for it, if I'm in the business of stealing data I'm likely to find a use for my exploit.

'If 20 million people use the same password manager and I have an exploit for it' Someone is going to exploit my local password manager remotely?

> Someone is going to exploit my local password manager remotely?

I don't know - who are you?

Even if you are not an especially valuable target, malware is pretty widespread. It steals credit card numbers and other data; if the attacker had a hack for a popular password manager, why wouldn't they go for it?

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