Date: Wed, 25 Sep 2013 16:19:29 +0200 From: Sebastian Krahmer <krahmer@...e.de> To: Steve Grubb <sgrubb@...hat.com> Cc: oss-security@...ts.openwall.com Subject: Re: Reproducible Builds for Fedora Hi On Wed, Sep 25, 2013 at 09:59:59AM -0400, Steve Grubb wrote: > Hello, > > On Wednesday, September 25, 2013 10:08:01 AM Sebastian Krahmer wrote: > > I was checking the rpm-compare how it actually is doing the compre > > and you have: > > > > [...] > > base=`basename $f` > > objdump -d rpm1/$f | grep -v $base > dump1 > > objdump -d rpm2/$f | grep -v $base > dump2 > > diff -u dump1 dump2 > /dev/null > > if [ $? -ne 0 ] ; then > > echo "File disassembly differs $f" > > cnt=`expr $cnt + 1` > > fi > > [...] > > > > for ELF files and doing a sha256sum for other file types. My concern is > > that attackers could construct a package that contains function-names that > > match the basename of the binary that you are checking. > > Thanks for the feedback. I think the 'grep -v' can be replaced with sed > '1,2d'. Its purpose was to delete the file path that objdump inserts at the top > which causes miscompares. What about using NT_GNU_BUILD_ID? By reading the ld source, it looks like all ELF sections with content are covered by the hash. Or are there any sections you want to skip? (It'd be a more clean solution IMHO, and probably the first real use-case for NT_GNU_BUILD_ID.) Sebastian -- ~ perl self.pl ~ $_='print"\$_=\47$_\47;eval"';eval ~ krahmer@...e.de - SuSE Security Team
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