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MEGApwn - Bookmarklet to recover your secret MEGA master key

nzkoz.github.io

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Re: MEGApwn - Bookmarklet to recover your secret MEGA master key

#21

Post by plaguuuuuu »

revelation wrote: post #13

This isn't even exactly about JavaScript cryptography. This is the equivalent to building a program to read the TrueCrypt keys out of memory. The problem here is "the machine doing the cryptography can not be trusted", not "it's JavaScript in a webbrowser", though of course thats also a fundamental problem.

The problem actually isn't "the machine doing the cryptography can not be trusted" - the machine is basically you, the user, obviously once you have your files they're on your computer. If you don't trust your computer, what use do you have for files in the first place.

Problem is actually "the computer that sends you code to run on your PC can't be trusted". Big difference..

Re: MEGApwn - Bookmarklet to recover your secret MEGA master key

#22

Post by Everlag »

austinz wrote: post #7

Thought tptacek's link on Javascript crypto, linked to in the article (and sort of a motivator for the experiment), was well worth a read. http://www.matasano.com/articles/javascript-cryptography/

Okay, this has absolutely nothing to do specifically with javascript in the browser! This attack is applicable to ANY system where the application designer leaves sensitive data in a place that can trivially accessed by malicious applications if they jump through a few simplistic hoops!

Mega left user data in an essentially public place.

Re: MEGApwn - Bookmarklet to recover your secret MEGA master key

#23

Post by e12e »

nly wrote: post #11
traskjd wrote: post #9

Earlier quoted context omitted.

Sure, but don't you think it's important that they make this clear? So far they market heavily on the fact that it's secure when this is simply not true. If you read their security page, they do say you shouldn't use it if you don't trust them. But that's about it for any warning that you're basically sitting there naked. I know no security system is entirely secure, but they aren't generally targeting security minde…

Meh. Should every site using HTTPS make it clear that hundreds of CAs whom you've never heard of have the capability to perform a MITM? At least with MEGA you know the security framework is something they've engineered themselves, so you know you have to trust them. With SSL/TLS you're deferring to authority simply because it's convenient.

You still have to trust SSL, in the case of MEGA, COMODO is their CA, and they appear to use 128bit RC4.

Of course, if you've not cleaned your trusted certificates, someone like CNic can just MTIM you.

Re: MEGApwn - Bookmarklet to recover your secret MEGA master key

#24

Post by fleitz »

revelation wrote: post #13

This isn't even exactly about JavaScript cryptography. This is the equivalent to building a program to read the TrueCrypt keys out of memory. The problem here is "the machine doing the cryptography can not be trusted", not "it's JavaScript in a webbrowser", though of course thats also a fundamental problem.

While they are the same class of attacks they are fundamentally different in the level of complexity required.

There's no 20 line piece of code that any user can run to get your TrueCrypt key, you're looking at an OS exploit to get kernel access, plus the code to find the key, and/or freezing the computer in liquid nitrogen and then reading the contents of memory directly.

Re: MEGApwn - Bookmarklet to recover your secret MEGA master key

#25

Post by e12e »

snissn wrote: post #17

They could AES your keys before storing it in local storage and prompt the user for this extra key whenever they need to access your keys. Otherwise your private keys are just stored in a sqlite file or some other implementation specific file that your browser created on your file system.

And how would you ensure that the passphrase isn't transmitted upstream by a modified js-client?

Re: MEGApwn - Bookmarklet to recover your secret MEGA master key

#27

Post by Mindless2112 »

nhm wrote: post #5
aray wrote: post #3

I hope they submitted this to the MEGA Vulnerability Rewards Program https://mega.co.nz/#blog_6 My guess is that it already has, and has been ruled a side-channel/social-engineering attack (requiring either a compromised browser or to run arbitrary javascript on the site).

Yea, he did. I think the point is more that MEGA can read the key, and your files without permission. This contradicts their claim "Your data is encrypted by you before upload to our system and therefore we do not and cannot access that content"

Their claim is true so long as they don't snatch the key from you when you access the MEGA website.

Re: MEGApwn - Bookmarklet to recover your secret MEGA master key

#29

Post by byroot »

fleitz wrote: post #24
revelation wrote: post #13

This isn't even exactly about JavaScript cryptography. This is the equivalent to building a program to read the TrueCrypt keys out of memory. The problem here is "the machine doing the cryptography can not be trusted", not "it's JavaScript in a webbrowser", though of course thats also a fundamental problem.

While they are the same class of attacks they are fundamentally different in the level of complexity required. There's no 20 line piece of code that any user can run to get your TrueCrypt key, you're looking at an OS exploit to get kernel access, plus the code to find the key, and/or freezing the computer in liquid nitrogen and then reading the contents of memory directly.

It also mean that any of your Chrome / Firefox extension can access it when you open mega.co.nz

Re: MEGApwn - Bookmarklet to recover your secret MEGA master key

#30

Post by alcari »

NotHereNotThere wrote: post #28
tomrod wrote: post #26

What is MEGA?

There's a link to MEGA's website, right at the top of the submitted story's webpage. You might enjoy reading before commenting.

Without Javascript, MEGA's website is a blank white page. Without knowing exactly what MEGA is, why should a sufficiently paranoid user allow js from it to run?
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