Date: Fri, 17 Oct 2014 10:10:15 -0400 From: Shawn Webb <lattera@gmail.com> To: Warner Losh <imp@bsdimp.com>, David Carlier <david.carlier@hardenedbsd.org> Cc: PaX Team <pageexec@freemail.hu>, FreeBSD Arch <freebsd-arch@freebsd.org> Subject: Re: PIE/PIC support on base Message-ID: <CADt0fhyZbnRZVwfvpvZDr5Qqd4X=yfcHR-GO_NFFNZx_ceOjOg@mail.gmail.com> In-Reply-To: <C7C48B02-E65C-4F90-A503-1FDDCB590B7D@bsdimp.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> <C7C48B02-E65C-4F90-A503-1FDDCB590B7D@bsdimp.com>
next in thread | previous in thread | raw e-mail | index | archive | help
On Fri, Oct 17, 2014 at 10:05 AM, Warner Losh <imp@bsdimp.com> wrote: > [[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? I like that idea. I think we need buy off from Kostik. David, what are your thoughts? Thanks, Shawn
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?CADt0fhyZbnRZVwfvpvZDr5Qqd4X=yfcHR-GO_NFFNZx_ceOjOg>