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CloudFlare's Heartbleed challenge cracked

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Re: CloudFlare's Heartbleed challenge cracked

#81

Post by Theriac25 »

jsmeaton wrote: post #79
pushrax wrote: post #71

Earlier quoted context omitted.

I would call this a "self-induced man in the middle attack". You're telling your computer that cloudflarechallenge.com is his server.

The point is you can connect to it with HTTPS and your browser doesn't throw up big flashy warnings. It's basically proof that he has got the private key, since he can impersonate cloudfarechallenge.com with regards to SSL.

He doesn't have to have the private key, only a private key that was signed by any of the hundreds (counting intermediate CAs, thousands?) CAs trusted by his browser.

Re: CloudFlare's Heartbleed challenge cracked

#82

Post by willvarfar »

dpweb wrote: post #65
nikcub wrote: post #62

Reading Cloudflare's blog post[0], they keep referring to the exploit having a length of 65,536 bytes, and how an allocation of that size is unlikely to find itself lower in the heap. That is true - but this exploit doesn't depend on setting a length of 65,536. The server takes whatever length the client gives it (which is, afterall, the bug). Most of the early exploits just happen to set the maximum packet size to g…

How do you know when you've found a piece of a key?

From a piece? Hard.

But brute force everything you get back? Easy.

Take every key-sized chunk of heap you got back, and see if, when interpreted as the key, it is the private key to the public cert. When found, send it in!

Re: CloudFlare's Heartbleed challenge cracked

#83

Post by paulbaumgart »

Theriac25 wrote: post #81
jsmeaton wrote: post #79

Earlier quoted context omitted.

The point is you can connect to it with HTTPS and your browser doesn't throw up big flashy warnings. It's basically proof that he has got the private key, since he can impersonate cloudfarechallenge.com with regards to SSL.

He doesn't have to have the private key, only a private key that was signed by any of the hundreds (counting intermediate CAs, thousands?) CAs trusted by his browser.

CAs will verify that you at least have control over hostmaster@ or an email listed in the WHOIS info for the domain before issuing certs.

Re: CloudFlare's Heartbleed challenge cracked

#84

Post by gojomo »

Theriac25 wrote: post #81
jsmeaton wrote: post #79

Earlier quoted context omitted.

The point is you can connect to it with HTTPS and your browser doesn't throw up big flashy warnings. It's basically proof that he has got the private key, since he can impersonate cloudfarechallenge.com with regards to SSL.

He doesn't have to have the private key, only a private key that was signed by any of the hundreds (counting intermediate CAs, thousands?) CAs trusted by his browser.

He has to have the private key that matches the certificate he's presenting.

He's presenting the CloudFlare-obtained cert (which the site offers up on request), so the lack of a warning means he's got that private key.

Getting another CA-signed certificate, naming 'www.cloudflarechallenge.com' and matching another private key, would itself be an impressive compromise, though not the challenge CloudFlare made or what he's demonstrating.

Re: CloudFlare's Heartbleed challenge cracked

#85

Post by tomkwok »

nikcub wrote: post #62

Reading Cloudflare's blog post[0], they keep referring to the exploit having a length of 65,536 bytes, and how an allocation of that size is unlikely to find itself lower in the heap. That is true - but this exploit doesn't depend on setting a length of 65,536. The server takes whatever length the client gives it (which is, afterall, the bug). Most of the early exploits just happen to set the maximum packet size to g…

I get your point, but CloudFlare actually fixed that 7 days before the public disclosure, that is 12 days ago.

"We fixed the flaw on Monday March 31, 2014 for all CloudFlare customers, with public notification on Monday April 7, 2014, after the researchers' public announcement." -- https://support.cloudflare.com/hc/en-us/articles/201660084-U...

Re: CloudFlare's Heartbleed challenge cracked

#86

Post by justincormack »

canadev wrote: post #74
patcheudor wrote: post #64

Earlier quoted context omitted.

Example from a memory dump on a vulnerable server (username & password changed to protect the innocent): `..?...t?.R...t> ...ned....userna me=0000000+0ew+0 user&password=my passw0rD.~Jt.... .3z..a.......... One of the things that caught me off guard, but isn't surprising is that some hosting companies don't use VM isolation, thus it was possible to pull memory from other sites which may have been patched. Hopefully h…

"[H]osting vendors that don't have isolated VM's don't also allow users to install their own OpenSSL as this would become a vector to compromise neighboring hosts." Could you explain this please? Here's a possible scenario... I root virtual machine X running on host Z (using heartbleed). Another machine running on Z is virtual machine Y. Because X and Y are not isolated, and I am running whatever I want on X, I can f…

This would only be an issue with shared hosting that shares a web server process.

Re: CloudFlare's Heartbleed challenge cracked

#87

Post by rich90usa »

dpweb wrote: post #65
nikcub wrote: post #62

Reading Cloudflare's blog post[0], they keep referring to the exploit having a length of 65,536 bytes, and how an allocation of that size is unlikely to find itself lower in the heap. That is true - but this exploit doesn't depend on setting a length of 65,536. The server takes whatever length the client gives it (which is, afterall, the bug). Most of the early exploits just happen to set the maximum packet size to g…

How do you know when you've found a piece of a key?

I would think that there could be some application of how genome sequencing is done? From what I understand chains of DNA are cut by restriction enzymes and these random chains are assembled together by some clever algorithms?

Re: CloudFlare's Heartbleed challenge cracked

#88

Post by Blahah »

rich90usa wrote: post #87
dpweb wrote: post #65

Earlier quoted context omitted.

How do you know when you've found a piece of a key?

I would think that there could be some application of how genome sequencing is done? From what I understand chains of DNA are cut by restriction enzymes and these random chains are assembled together by some clever algorithms?

Depending on the nature of the strings, yes. If there is no repetition or errors in the representation of the sequence, you could use overlap layout consensus if it were small, or de-brujn or string graphs if it were large. For repetitive but error free sequences, de-brujn and string graph will do. For error-containing sequences, only the de-brujn graph (with the proviso that you'll reconstruct some false-positive sequences too).

Re: CloudFlare's Heartbleed challenge cracked

#89

Post by btown »

gojomo wrote: post #32
danielpal wrote: post #30

The important thing to know here is that you not only have to change your current certs you ALSO HAVE TO REVOKE THE OLD ONE. If you only change your current cert to get a new key but you don't go through the revocation process of the old certificate if someone managed to get the old one they can still use it for a MiTM attack - as both certs would be valid to any client.

Also, cert revocation just barely works, in some browsers, with EV certificates, after old CRLs expire over a course of months: http://news.netcraft.com/archives/2013/05/13/how-certificate...

Is there a tutorial (for multiple browsers/platforms) for browser users to manually initiate downloading and processing of the latest CRL? Is this even exposed by most modern browsers, i.e. as part of the "clear cache" functionality? If so, I'd want to tell my [self/family/friends/coworkers] to do this in the coming weeks to minimize the amount of time they might happen to send private information to a MITM attacking, say, an e-commerce site.

Specifically, I'd be most interested for such a walkthrough for Google Chrome on OS X, which most people I know use.

Re: CloudFlare's Heartbleed challenge cracked

#90

Post by cpach »

Theriac25 wrote: post #81
jsmeaton wrote: post #79

Earlier quoted context omitted.

The point is you can connect to it with HTTPS and your browser doesn't throw up big flashy warnings. It's basically proof that he has got the private key, since he can impersonate cloudfarechallenge.com with regards to SSL.

He doesn't have to have the private key, only a private key that was signed by any of the hundreds (counting intermediate CAs, thousands?) CAs trusted by his browser.

See here how to verify that Indutny indeed snatched the private key from Cloudflare’s server: http://dankaminsky.com/2014/04/12/bloody-cert-certified/
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