Date: Wed, 16 May 2012 01:23:39 +0300 From: Milen Rangelov <gat3way@...il.com> To: john-dev@...ts.openwall.com Subject: Re: RAR early reject P.S by "no rar archiver" I mean two different winrar versions I use to generate rar files - one rather old on a XP machine, and one recent one. Both have the same limits on max order and memory to use for models. Still I am not at all convinced this is always the case. On Wed, May 16, 2012 at 1:21 AM, Milen Rangelov <gat3way@...il.com> wrote: > True. > > If I understand correctly, it should never go beyond 63 as no rar archiver > I've seen allows it. I think a similar check can be done for maxmb (winrar > imposes a limit of 128MB). This helps. But we definitely need some early > reject in the LZ case. > > On Wed, May 16, 2012 at 12:59 AM, magnum <john.magnum@...hmail.com> wrote: > >> On 05/15/2012 09:05 AM, Milen Rangelov wrote: >> > I am reaching the same conclusion. I was able to do another check for >> the >> > PPM part, order should never be more than 63 (as this is the archiver >> > limit) and this is safe I think. >> >> Do you mean max_order in ppm_decode_init() right after reading it from >> rar_get_char()? Or did you test somewhere else? >> >> I also found from original unpack.cpp that filter_pos in add_vm_code() >> should never be > 1024 but I haven't ever seen it happen. Maybe I'll >> drop that test again even though it's there in the original code (for >> some reason it was not in clamav's code). BTW I only recently realized >> how easy it is to compare the original .cpp code with clamav's code. >> They really just ported it. The original code has more comments. >> >> We are currently rejecting 93% of the data on average, compared to >> reading all of the data each time. That may sound good, but for a 500 MB >> file we still need to decrypt and read 3.6 MB on average. >> >> magnum >> >> > Content of type "text/html" skipped
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