CryptoCat iOS Application Penetration Test [pdf] • Hacker News Board

Re: CryptoCat iOS Application Penetration Test [pdf]

#81

Post by tptacek » Thu, Apr 03, 2014, 12:59 AM UTC

kaeporan wrote: post #80

natdempk wrote: post #47

Earlier quoted context omitted.

I don't believe they've had an independent security audit. I think their team however is comprised of more respected cryptographers like Moxie Marlinspike, who introduced the concept of SSL stripping, one of the issues that was found in the CryptoCat app. I mean no disrespect to CryptoCat, and more eyes can always find something someone overlooked, but I think the Open Whisper Systems (TextSecure) team is stronger an…

iSEC also audited TextSecure, but TextSecure chose not to publish the audit.

And? What does this have to do with the parent comment?

Re: CryptoCat iOS Application Penetration Test [pdf]

#82

Post by illumen » Thu, Apr 03, 2014, 1:03 AM UTC

tptacek wrote: post #63

illumen wrote: post #61

Earlier quoted context omitted.

No need for an of audit TextSecure... just go to their github issues page. Plenty of open bugs and regressions, some of them as serious as some of the ones in the latest CryptoCat app audits. For example, one issue where some messages sent are not being encrypted. Even with 'amazing' contributors, bugs are still there in TextSecure.

I just reviewed all open and closed bugs in TextSecure's Issues page and didn't see a single crypto protocol bug. Admittedly, I looked quickly and casually. Could you point us to one?

"I just reviewed all open and closed bugs in TextSecure's Issues page and didn't see a single crypto protocol bug. Admittedly, I looked quickly and casually. Could you point us to one?"

You could not have reviewed all open and closed bugs in 8 minutes ;)

Issue 1073: https://github.com/WhisperSystems/TextSecure/issues/1073

Another one: Just sent an encrypted photo to someone? The photo is stored unencrypted on your phone.

Edit: group messages were also sent unencrypted, but this was fixed. https://github.com/WhisperSystems/TextSecure/issues/32

Edit2: ok, I see your point. Maybe they do crypto well as you say, but they don't seem to do software engineering well, or UI design for secure text messaging well. Sending messages unencrypted, and leaving messages unencrypted on the phone is a big fail in overall security of the app. It's meant to encrypt things, and it doesn't. That it doesn't put in tests for these things, and that it did not publish the independent security audit should cause everyone to reconsider using the TextSecure app for its stated purpose.

Re: CryptoCat iOS Application Penetration Test [pdf]

#83

Post by sneak » Thu, Apr 03, 2014, 1:04 AM UTC

anologwintermut wrote: post #52

kaeporan wrote: post #14

Earlier quoted context omitted.

Fixes and improvements to this, and more, are covered in our blog post. I strongly urge you to read it. This audit alone doesn't give enough context. https://blog.crypto.cat/2014/04/recent-audits-and-coming-imp...

What's your fix for the man-in-the-middle attack on all platforms (including deployed ones) the audit identifies and your blog acknowledges? In your blog post there seems to be little context that can excuse such a mistake and nothing that explains how you fix it? Am I correct in reading your blog post that right now there isn't a fix? I.e. it's an open attack assuming someone compromises a CA or a cryptocat server?…

> In your blog post there seems to be little context that can excuse such a mistake

This is a recurring theme with cryptocat. Stay away for 5-10 years until they get their act together.

Re: CryptoCat iOS Application Penetration Test [pdf]

#84

Post by sneak » Thu, Apr 03, 2014, 1:05 AM UTC

kaeporan wrote: post #18

Hi, I'm the lead developer for Cryptocat. I strongly urge you all to please read our blog post regarding this audit: https://blog.crypto.cat/2014/04/recent-audits-and-coming-imp... This audit document alone does not give enough context. This audit was commissioned by us and concerns a pre-release version of Cryptocat for iPhone. Many of the bugs it found are due to the fact that it was reviewing a prototype with debu…

> It's very unfortunate that this audit is being taken out of context like this and used to attack our effort.

No, what's unfortunate is your continued and repeated claims that cryptocat should be used today by people who expect privacy, when it is not yet safe or secure for private messaging.

You're going to get people killed. You don't seem to care.

Re: CryptoCat iOS Application Penetration Test [pdf]

#85

Post by m0nastic » Thu, Apr 03, 2014, 1:06 AM UTC

rdl wrote: post #66

lincolnq wrote: post #22

This is awesome. I'm sad that CryptoCat is getting slammed for this for being one of the brave few to post this online. I am sure there are an infinite number of "security-critical" apps which would fail an audit like this, but who never even thought to GET an audit -- much less post it online. The software development community is much stronger for being able to see professional stuff like this posted. Does anyone k…

Generally 10-50k is a good starting point for this level. Most firms are full up on work most of the time, but will often try to get interesting new companies or projects even if they're less profitable since 1) they can grow into better stuff 2) good for reputation and for retention of their own employees. Compliance-only is usually cheaper; you can buy rubber stamps for <$10k.

It's important to distinguish that the places offering the Places like that are just running a scanner against your website. In the case of an app like this (which was an iOS app), you might find a cheap place to run it through a source code analyzer (either through a cloud-hosted service like Veracode, or by running an app like AppScan).

Assuming you wanted to hire a "respectable" firm to actually perform a real application assessment, I'd say it's closer to 30-50k.

If you look at the report, it was scoped at 3 man-weeks of testing (which in this case looks like it was 3 engineers for 1 week). Even if you don't include any additional overhead (like hours for the report generation, or project management hours), you're looking at ~24k just for the engineers effort (if they just priced it t&m, which hopefully they don't).

To be fair, this is a pretty exotic application though, compared to what a lot of other people might be working on. The scope for a project to test a more "normal" app would be less. Maybe even half that.

Re: CryptoCat iOS Application Penetration Test [pdf]

#86

Post by sneak » Thu, Apr 03, 2014, 1:07 AM UTC

kaeporan wrote: post #8

natdempk wrote: post #5

Also of interest is their blog post about how they plan to handle the issues described in this report: https://blog.crypto.cat/2014/04/recent-audits-and-coming-imp... Reading that, I still am not sure why anyone would use CryptoCat especially with things like TextSecure on the market that seem to take crypto far more seriously. The only reason I can see for that is that they have clients on more platforms, but if thi…

Thanks for linking to the blog post. This audit concerns a pre-release version of Cryptocat for iPhone. Many of the bugs were due to debugging code and were fixed before release.

Why use donated money to pay for an audit of software that has known bugs and isn't ready yet? That's wasteful. The point of an audit is to find bugs you don't already know about.

Re: CryptoCat iOS Application Penetration Test [pdf]

#87

Post by aeontech » Thu, Apr 03, 2014, 1:09 AM UTC

tptacek wrote: post #81

kaeporan wrote: post #80

Earlier quoted context omitted.

iSEC also audited TextSecure, but TextSecure chose not to publish the audit.

And? What does this have to do with the parent comment?

The grandparent asked whether they have had a security audit, and parent said "I don't believe they've had an independent security audit." Seems like a straightforward reply to those.

Re: CryptoCat iOS Application Penetration Test [pdf]

#88

Post by tptacek » Thu, Apr 03, 2014, 1:10 AM UTC

aeontech wrote: post #87

tptacek wrote: post #81

Earlier quoted context omitted.

And? What does this have to do with the parent comment?

The grandparent asked whether they have had a security audit, and parent said "I don't believe they've had an independent security audit." Seems like a straightforward reply to those.

Oh. Duh. You're right. I was skimming my threads and lost the context. Thanks for pointing this out.

Re: CryptoCat iOS Application Penetration Test [pdf]

#89

Post by kaeporan » Thu, Apr 03, 2014, 1:12 AM UTC

115515 wrote: post #42

kaeporan wrote: post #23

Earlier quoted context omitted.

We commissioned this audit in late December and iSec began working on it in January. They audited a pre-release prototype that we provided. This is noted in the audit document, but it's hard to spot unfortunately. The reason we commissioned this audit is to make sure our prototype was audited before release on the App Store. We're very happy to have benefited from this audit, but linking to this PDF alone de-contextu…

How was this a "pre-release prototype" audit of Cryptocat if the app was for iOS was rejected from the Apple app store in December .... and the audit took place after that in mid January? Seems dubious to say it was all about some extra debug logging when there are some serious flaws here found weeks after it almost was approved on the Apple store. http://www.theverge.com/2013/12/27/5249402/encrypted-chat-se...

We submitted a pre-emptive build just to obtain approval from Apple. We were going to wait to update it with the audited build before actually releasing it (Apple lets you schedule releases in advance.) In retrospect, it was lucky we got Apple's rejection early on, so we were able to deal with it better.

Re: CryptoCat iOS Application Penetration Test [pdf]

#90

Post by tptacek » Thu, Apr 03, 2014, 1:13 AM UTC

illumen wrote: post #82

tptacek wrote: post #63

Earlier quoted context omitted.

I just reviewed all open and closed bugs in TextSecure's Issues page and didn't see a single crypto protocol bug. Admittedly, I looked quickly and casually. Could you point us to one?

"I just reviewed all open and closed bugs in TextSecure's Issues page and didn't see a single crypto protocol bug. Admittedly, I looked quickly and casually. Could you point us to one?" You could not have reviewed all open and closed bugs in 8 minutes ;) Issue 1073: https://github.com/WhisperSystems/TextSecure/issues/1073 Another one: Just sent an encrypted photo to someone? The photo is stored unencrypted on your ph…

I read that issue especially carefully since it was on the front page, and it doesn't look like a crypto protocol bug. I'm actually not sure what that bug is.

A crypto protocol bug is something like "TextSecure tried to implement secure file transfer, used the CTR block cipher mode, and managed to make the keystreams collide, so that passive attackers could recover file contents from encrypted streams".

The general point you made, that all applications have bugs (and thus security bugs) is valid. I'm drawing a line that you're not drawing, between design flaws in cryptosystems and random iOS/Android mistakes.