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CryptoCat iOS Application Penetration Test [pdf]

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Re: CryptoCat iOS Application Penetration Test [pdf]

#11

Post by sentenza »

rancor wrote: post #4

When I saw one of the main CryptoCat developers present in 2012, I came away with the impression that nobody on the core team understood crypto, security, or software engineering. This audit is another rock on the mountain of evidence I've seen supporting this impression in the following years. A really nice job by iSec, though.

It is also important to always remember that a crypto app isn't like other apps. If the protesters in Turkey rely on shoddy crypto today, it might cost them their lives a few months from now. I sincerely hope it doesn't come to that but it is a realistic example.

Always be sure of what you are doing, rely on external review and never, I repeat, _never_ overstate the security of your crypto system.

Re: CryptoCat iOS Application Penetration Test [pdf]

#12

Post by primitivesuave »

This is most alarming.

CryptoCat's OTR implementation on all platforms allows a chat peer to change their OTR key during a chat session without user notification. An attacker performing a man-in-the-middle attack against the client's XMPP or HTTPS stream can inject their own OTR key in the discussion after a user has authenticated their peer's OTR fingerprint. This permits the attacker to decrypt all messages that follow, and no user would have reason to suspect the compromise.

Re: CryptoCat iOS Application Penetration Test [pdf]

#13

Post by computer »

rancor wrote: post #4

When I saw one of the main CryptoCat developers present in 2012, I came away with the impression that nobody on the core team understood crypto, security, or software engineering. This audit is another rock on the mountain of evidence I've seen supporting this impression in the following years. A really nice job by iSec, though.

I wasn't going to post this, but I had the same feeling at a conference. Also, if I remember correctly, the first version that got audited turned out to be extremely insecure as well, with their own custom crypto protocols? I haven't recommended CryptoCat to anyone since, and still wouldn't.

This audit report is another fascinating read to see all the mistakes I would probably have made as well. Secure crypto is so incredibly difficult to get right...

Re: CryptoCat iOS Application Penetration Test [pdf]

#14

Post by kaeporan »

primitivesuave wrote: post #12

This is most alarming. CryptoCat's OTR implementation on all platforms allows a chat peer to change their OTR key during a chat session without user notification. An attacker performing a man-in-the-middle attack against the client's XMPP or HTTPS stream can inject their own OTR key in the discussion after a user has authenticated their peer's OTR fingerprint. This permits the attacker to decrypt all messages that foll…

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...

Re: CryptoCat iOS Application Penetration Test [pdf]

#15

Post by oliwary »

sliverstorm wrote: post #9
venomsnake wrote: post #7

There is a "many ways to skin a cat" joke here somewhere. It is actually terrible - the hmac timing attack requires around 3 minutes of google searching to avoid and is basic public domain knowledge. The other are much worse.

I wish I knew how to find my way into security as a hobby. Such a fun topic.

I am in the same position. Stanford Online started a Coursera course on cryptography yesterday, might be interesting for you.

https://www.coursera.org/course/crypto

Re: CryptoCat iOS Application Penetration Test [pdf]

#16

Post by kaeporan »

computer wrote: post #13
rancor wrote: post #4

When I saw one of the main CryptoCat developers present in 2012, I came away with the impression that nobody on the core team understood crypto, security, or software engineering. This audit is another rock on the mountain of evidence I've seen supporting this impression in the following years. A really nice job by iSec, though.

I wasn't going to post this, but I had the same feeling at a conference. Also, if I remember correctly, the first version that got audited turned out to be extremely insecure as well, with their own custom crypto protocols? I haven't recommended CryptoCat to anyone since, and still wouldn't. This audit report is another fascinating read to see all the mistakes I would probably have made as well. Secure crypto is so i…

It's important to note that this audit concerned a pre-release, debugging version of Cryptocat for iPhone. The audit document alone doesn't give enough context; I strongly urge reading our blog post: https://blog.crypto.cat/2014/04/recent-audits-and-coming-imp...

Re: CryptoCat iOS Application Penetration Test [pdf]

#17

Post by scott_s »

sliverstorm wrote: post #9
venomsnake wrote: post #7

There is a "many ways to skin a cat" joke here somewhere. It is actually terrible - the hmac timing attack requires around 3 minutes of google searching to avoid and is basic public domain knowledge. The other are much worse.

I wish I knew how to find my way into security as a hobby. Such a fun topic.

Long-time HN member tptacek's company has a challenge set that many praise highly: http://www.matasano.com/articles/crypto-challenges/

Re: CryptoCat iOS Application Penetration Test [pdf]

#18

Post by kaeporan »

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 debugging features (such as NSLog) turned on. While this audit definitely does find some vulnerabilities and room for improvement, none of the critical bugs in this audit ever made it to Cryptocat for iPhone's release.

It's very unfortunate that this audit is being taken out of context like this and used to attack our effort. I'd appreciate it if you could please upvote this comment and help me contextualize this audit. Again, please, read the blog post for context (and also for the results of another audit we comissioned in parallel.) We've done our best to address these issues and are working towards an open discussion on how to improve accessible encryption. https://blog.crypto.cat/2014/04/recent-audits-and-coming-imp...

The blog post's last section ("On the Significance of Audits") discusses why it is that Cryptocat has seen more audits published about it than other encryption projects. Please, dare to discern. Read what we're doing to improve the security of accessible encryption and our reasoning for publishing these audits. I'll be grateful for you taking the time to read on what we're doing and I am more than happy to discuss with you and answer your questions.

Re: CryptoCat iOS Application Penetration Test [pdf]

#19

Post by mandalar12 »

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…

Has anyone done the same level of analysis on TextSecure ? I feel like their model/seriousness is better but there might be flaws in the implementation (or protocol) and being audited might highlight some of them.

Re: CryptoCat iOS Application Penetration Test [pdf]

#20

Post by erikano »

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…

Upvoted your comment, flagged OP post. Don't think I've flagged anything on HN before, but I think this warrants that.
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