phc-discussions - Re: [PHC] Any "large verifiers" on the panel?

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Date: Sun, 17 Feb 2013 19:40:05 -0800
From: Jeremi Gosney <epixoip@...dshell.nl>
To: Daniel Franke <dfoxfranke@...il.com>
CC: discussions@...sword-hashing.net
Subject: Re: [PHC] Any "large verifiers" on the panel?

On 2/17/2013 4:25 PM, Daniel Franke wrote:
> Jeremi Gosney <epixoip@...dshell.nl> writes:
>
>> You have to assume that if the passwords are compromised, the
>> encryption key is as well.
> I'm with all those who say that we shouldn't be granting this
> assumption. An adversary who has completely compromised a web server
> doesn't have to bother cracking password hashes at all. He can just
> capture unhashed passwords as they arrive over the wire. If we aren't
> completely wasting our time having this competition, then we should
> absolutely be thinking about what constitutes a realistic model of
> common partial-compromise scenarios

I'm assuming that those who say that we should not be granting this
assumption either are not hackers, or do not have an extensive
background in real-world exploitation and post-exploitation. But that's
okay, because as JP stated, one of the goals of this competition & list
is to bring the academic and non-hacker types together with the
"real-world" types.

We are not assuming a complete compromise (i.e., root access) here.
We're merely assuming an attacker who is able to execute arbitrary code
in the context of the web server or webapp.

SQL injection, remote includes, local includes, and straight RCE flaws
are by and large the biggest ways password hashes are compromised. More
often than not, these vulnerabilities can be leveraged to view arbitrary
files, or in the best case scenario, obtain a shell running under the
context of the httpd or webapp.

A majority of the time, it is not possible to escalate our privileges.
But what we can do is leverage our context to read any files that the
httpd or webapp has permission to read. In the case of something like
encryption, where the webapp has to have access to the key to
encrypt/decrypt passwords, you too have access to the encryption key.

And this is not an uncommon practice; config files and the webapp source
code are among the first places we turn to determine exactly how the
passwords have been hashed or otherwise obfuscated. Even if we dump a
database and see what appear to be raw MD5 hashes, we still go to the
code to verify the exact algorithm used. And if we see that the
passwords were encrypted instead of hashed, we go straight to key. (And
yes, this does actually happen on the rare occasion we find someone who
is naive enough to encrypt passwords.)

The same is true for any secrets that are used. If the webapp has
permission to read them (which of course it does), then we have
permission to read them too, and they are no longer secret.

Regards,
Jeremi