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Offset2lib: bypassing full ASLR on 64bit Linux

Hi, 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 Hector Marco. http://cybersecurity.upv.es _______________________________________________ Sent through the Full Disclosure mailing list http://nmap.org/mailman/listinfo/fulldisclosure Web Archives & RSS: http://seclists.org/fulldisclosure/

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