Date: Fri, 17 Oct 2014 08:05:57 -0600 From: Warner Losh <imp@bsdimp.com> To: Shawn Webb <lattera@gmail.com> Cc: PaX Team <pageexec@freemail.hu>, FreeBSD Arch <freebsd-arch@freebsd.org> Subject: Re: PIE/PIC support on base Message-ID: <C7C48B02-E65C-4F90-A503-1FDDCB590B7D@bsdimp.com> In-Reply-To: <CADt0fhyCBa3PTnZ3dpc-hpysyC9V0MXR16s-e10V0ioAfaWHuw@mail.gmail.com> References: <CAMe1fxaYn%2BJaKzGXx%2Bywv8F0mKDo72g=W23KUWOKZzpm8wX4Tg@mail.gmail.com> <CAGSa5y3s9r0DRyinfqV=PJc_BT=Em-SLfwhD25nP0=6ki9pHWw@mail.gmail.com> <CAMe1fxaBEc5T77xjpRsMi_kkc5LXwPGooLWTO9C1FJcLSPnO8w@mail.gmail.com> <CAGSa5y2=bKpaeLO_S5W%2B1YGq02WMgCZn_5bbEMw%2Bx3j-MYDOoA@mail.gmail.com> <CADt0fhzg5G1cLEBNfHXSEi9iP7mCP=8sSwpXbFobig=pm=QsFQ@mail.gmail.com> <CAGSa5y1LBxkUNSgKkw=F9_uykXDeBV7_WL0a7Wt%2B%2BGgMTSULEQ@mail.gmail.com> <CADt0fhweiymn2D09%2Be7f44AreWe%2B8cmAtDVeec0NfmuWuOOhbg@mail.gmail.com> <315B4DC5-0E04-4F6B-BBB0-477D049025BF@bsdimp.com> <CADt0fhyCBa3PTnZ3dpc-hpysyC9V0MXR16s-e10V0ioAfaWHuw@mail.gmail.com>
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[-- Attachment #1 --] [[cc trimmed ]] On Oct 17, 2014, at 7:46 AM, Shawn Webb <lattera@gmail.com> wrote: > On Fri, Oct 17, 2014 at 9:41 AM, Warner Losh <imp@bsdimp.com> wrote: > > On Oct 17, 2014, at 2:05 AM, Shawn Webb <lattera@gmail.com> wrote: > > > On Fri, Oct 17, 2014 at 3:53 AM, Jeremie Le Hen <jlh@freebsd.org> wrote: > > > >> On Fri, Oct 17, 2014 at 12:15 AM, Shawn Webb <lattera@gmail.com> wrote: > >>> > >>> > >>> On Thu, Oct 16, 2014 at 5:59 PM, Jeremie Le Hen <jlh@freebsd.org> wrote: > >>>> > >>>> On Thu, Oct 16, 2014 at 8:21 PM, David Carlier > >>>> <david.carlier@hardenedbsd.org> wrote: > >>>>> > >>>>> I chose the "atomic" approach, at the moment very few binaries are > >>>>> concerned at the moment. So I applied INCLUDE_PIC_ARCHIVE in the > >> needed > >>>>> libraries plus created WITH_PIE which add fPIE/fpie -pie flags only if > >>>>> you > >>>>> include <bsd.prog.pie.mk> (which include <bsd.prog.mk>...) otherwise > >>>>> other > >>>>> binaries include <bsd.prog.mk> as usual hence does not apply. Look > >>>>> reasonable approach ? > >>>> > >>>> I think I understand what you mean. But I think PIE is commonplace > >>>> nowadays and I don't understand what you win by not enabling it for > >>>> the whole system. Is it a performance concern? Is it to preserve > >>>> conservative minds from to much change? :) > >>> > >>> > >>> Looping in Kostik, Bryan Drewery, the PaX team, Hunger, and Sean Bruno. > >>> > >>> On i386, there is a performance cost due to not having an extra register > >>> available for the relocation work that has to happen. PIE doesn't carry > >> much > >>> of a performance penalty on amd64, though it still does carry some on > >> first > >>> resolution of functions (due to the extra relocation step the RTLD has to > >>> worry about). On amd64, after symbol resolution has taken place, there > >> is no > >>> further performance penalty due to amd64 having an extra register to use > >> for > >>> PIE/PIC. I'm unsure what, if any, performance penalty PIE carries on ARM, > >>> AArch64, and sparc64. > >>> > >>> Certain folk would prefer to see PIE enabled only in certain > >> applications. > >>> /bin/ls can't really make much use of PIE. But sshd can. I personally > >> would > >>> like to see all of base's applications compiled as PIEs, but that's a > >> long > >>> ways off. It took OpenBSD several years to accomplish that. Having > >> certain > >>> high-visibility applications (like sshd, inetd, etc) is a great start. > >>> Providing a framework for application developers to opt their application > >>> into PIE is another great start. > >>> > >>> Those are my two cents. > >> > >> OK. As long as i386 is still an important architecture, it can make > >> sense to enable this on a per-binary basis if we don't want to have a > >> discrepancy between archs. Also I buy your argument on /bin/ls but I > >> was challenging to enable for the whole system because I wonder if > >> there aren't some unexpected attack surfaces, besides the obvious ones > >> (servers). > >> > >> Do you know what took so much time to OpenBSD? > > > > > > In a private conversation with Theo, I realized that my recollection of the > > time it took OpenBSD to compile all of base as PIEs was wrong. Quoting him: > > > > "It took 5 people approximately 3 months to debug it, activate it, and > > start shipping it the next release. That was on amd64, for all > > dynamically linked binaries, except one (a gcc bug took some time to > > find). The next architectures followed about 1 or 2 per 6-month > > release." > > > > Given that only one person has worked on this in the past (me) and now the > > task has been delegated to another (David Carlier), I think we're doing > > okay on our end. There's a lot of moving parts, and neither of us fully > > understand all of them completely. We're working on it in HardenedBSD, in > > the hardened/current/pie branch. > > > > I'm thinking we might try for a WITH_PIE knob (and *not* use USE_PIE) and > > have certain high-profile applications opt-in to PIE until we work out all > > the details for everything en masse. Baptiste did bring up a good point > > with INTERNALLIB and I'm unsure of how we should handle that. > > WITH_PIE or WITHOUT_PIE controls, on a global basis, via the MK_PIE > variable, whether or not the user wants to turn on this feature for those > program that can do PIE. Designating which programs do, or don’t, > use PIE simply must be done with a different variable. I posted a bit of a > rant about the current state of things that suggested a couple of > alternatives as well as giving some history as to why some options > aren’t to be used and the history behind some of my reactions. :) > > For this reason, I think WITH_PIE, as I understand your proposal, > likely isn’t a good fit with other WITH_xxx variables used in the src > tree today. > > Gotcha. To be honest, I found your email a tad bit confusing. Are you suggesting we create an ENABLE_feature framework? Or are you suggesting we have a USE_PIE flag? Or are you suggesting something different entirely (and if you are, what?)? I’m saying we don’t have a good framework at the moment to do this. We have several bad ones that all have their pitfalls. This is one reason I had the fast reaction to NO_PIE, then a minute later said “go ahead and use it and I’ll fix it.” I’m still cool with that position, btw. As for a name, that can be debated a lot, but I’d like to see something new, easy to use and unambiguous. If you are looking for a suggestion for that name, let’s go with WANTS_PIE. Only Makefiles can set it. WANTS_PIE undefined means do the default behavior as defined by the current MK_PIE setting and perhaps system policy. “Go with this flow." WANTS_PIE=yes means that if MK_PIE is “yes”, then do PIE things for this thing we’re building. If MK_PIE is “no”, though PIE is disabled for everything. WANTS_PIE=no means that if MK_PIE is “yes”, then disable doing PIE things for this component. If MK_PIE is no, it is also disabled. This could also be extended to NEEDS_foo, which says “I need foo to build, and if MK_foo is set to no, don’t build me.” I don’t think anything that you are doing falls into this category though. WANTS/NEEDS also avoids the historical use of USE in the ports tree possibly creating confusion. If you go with WANTS_PIE, then you wouldn’t need bad.*.pie.mk. Comments? 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