Messages in this thread | | | Date | Tue, 9 Dec 2014 09:37:33 -0800 | Subject | Re: [PATCH] ASLRv3: randomize_va_space=3 preventing offset2lib attack | From | Kees Cook <> |
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On Mon, Dec 8, 2014 at 12:09 PM, Christian Borntraeger <borntraeger@de.ibm.com> wrote: > Am 05.12.2014 um 01:07 schrieb Hector Marco: >> [PATCH] ASLRv3: randomize_va_space=3 preventing offset2lib attack >> >> The issue appears on PIE linked executables when all memory areas of >> a process are randomized (randomize_va_space=2). In this case, the >> attack "offset2lib" de-randomizes all library areas on 64 bit Linux >> systems in less than one second. >> >> Further details of the PoC attack at: >> http://cybersecurity.upv.es/attacks/offset2lib/offset2lib.html >> >> PIE linked applications are loaded side by side with the dynamic >> libraries, which is exploited by the offset2lib attack. Moving away >> the executable from the mmap_base area (libraries area) prevents the >> attack. >> >> This patch loads the PIE linked executable in a different area than >> the libraries when randomize_va_space=3. >> >> Patch implementation details: >> >> - The ELF_ET_DYN_BASE address is used as the base to load randomly >> the PIE executable. >> >> - The executable image has the same entropy than >> randomize_va_space=2. > [...] >> --- a/arch/arm/mm/mmap.c >> +++ b/arch/arm/mm/mmap.c > [...] >> --- a/arch/arm64/mm/mmap.c >> +++ b/arch/arm64/mm/mmap.c > [...] > >> --- a/arch/x86/mm/mmap.c >> +++ b/arch/x86/mm/mmap.c > [...] > > FWIW, please note that s390 and power (maybe others?) also have PIE support done differently, e.g. > commit d2c9dfccbc3 ("[S390] Randomize PIEs") and commit 501cb16d3cfdc ("powerpc: Randomise PIEs") > > What I can tell from a quick look both architectures should be fine regarding offsetlib, as they place the executable already in a different section and randomize those differently even with randomize_va_space=2. > > Would it make sense to unify the implementations again?
Seems like that would be best. If this is already being done on non-x86 and non-arm, we should just fix x86 and arm to DTRT. :)
-Kees
-- Kees Cook Chrome OS Security
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