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Message-ID: <CACYkhxirraZ9g4HForJBSSTfckHXuinkrz3zwagW_jq0JKLUwA@mail.gmail.com>
Date: Tue, 16 Jun 2015 21:04:52 +1000
From: Michael Samuel <mik@...net.net>
To: oss-security@...ts.openwall.com
Subject: Re: PostgreSQL - Predictable cancel key
Hi,
On 16 June 2015 at 20:15, Pierre Schweitzer <pierre@...ctos.org> wrote:
> Well, I've thought about it, but that's still one million seeds and
> the cancel key you're looking for might have been generated after
> several random() call. So, that means perhaps 10 millions values to
> explore? (If we make the hypothesis that for a given initialization,
> it will only draw 10 PRN)
>
This is CPU, maybe GPU territory. 2^15-2 * 10m =~ 2^38 work offline.
> How relevant would still be your cancel key once you found it?
In the postmaster mainloop:
ConnCreate()
RandomSalt() -- the md5Salt craziness in the original post
BackendStartup()
MyCancelKey = PostmasterRandom();
No other calls to random(), srandom() that I can see, and the other calls
to PostmasterRandom() are generating cancel keys for worker procs.
So if you brute the md5Salt you have a pretty good chance of guessing
something that was/is/will be a cancel key of another session.
Regards,
Michael
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