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Message-ID: <20141204234734.GW18807@outflux.net> Date: Thu, 4 Dec 2014 15:47:34 -0800 From: Kees Cook <keescook@...omium.org> To: oss-security@...ts.openwall.com Cc: Hector Marco <hecmargi@....es> Subject: Re: Offset2lib: bypassing full ASLR on 64bit Linux On Thu, Dec 04, 2014 at 09:19:04PM +0100, Hector Marco wrote: > This is a disclosure of a weakness of the ASLR Linux implementation. > The problem appears when the executable is PIE compiled and it has an > address leak belonging to the executable. We named this weakness: > offset2lib. > > In this scenario, an attacker is able to de-randomize all mmapped > areas (libraries, mapped files, etc.) by knowing only an address > belonging to the application and the offset2lib value. > > We have built a PoC which bypasses on a 64 bit Linux system, the three > most widely adopted and effective protection techniques: No-eXecutable > bit (NX), address space layout randomization (ASLR) and stack smashing > protector (SSP). The exploit obtains a remote shell in less than one > second. > > We have proposed the ASLRv3 which is a small Linux patch which removes > the offset2lib weakness. > > Details of the weakness, steps to exploit the offset2lib weakness, a working > proof of concept exploit, recommendations and a demonstrative video > has been > publish at: http://cybersecurity.upv.es/attacks/offset2lib/offset2lib.html Thanks for the research! Following the submission guidelines[1], please send your ASLRv3 patch to upstream at linux-kernel@...r.kernel.org and CC the following people: Andrew Morton <akpm@...ux-foundation.org> Thomas Gleixner <tglx@...utronix.de> Ingo Molnar <mingo@...hat.com> "H. Peter Anvin" <hpa@...or.com> Russell King <linux@....linux.org.uk> Catalin Marinas <catalin.marinas@....com> Will Deacon <will.deacon@....com> Oleg Nesterov <oleg@...hat.com> Andy Lutomirski <luto@...capital.net> Kees Cook <keescook@...omium.org> I noticed in testing that this hugely reduces the available mmap space available to 32-bit processes. I suspect this is what this wasn't done before. Thanks! -Kees [1] https://www.kernel.org/doc/Documentation/SubmittingPatches -- Kees Cook Chrome OS Security
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