Date: Fri, 17 Oct 2014 09:46:27 -0400 From: Shawn Webb <lattera@gmail.com> To: Warner Losh <imp@bsdimp.com> Cc: hunger@hunger.hu, David Carlier <david.carlier@hardenedbsd.org>, Oliver Pinter <oliver.pntr@gmail.com>, PaX Team <pageexec@freemail.hu>, Sean Bruno <sbruno@freebsd.org>, Konstantin Belousov <kib@freebsd.org>, FreeBSD Arch <freebsd-arch@freebsd.org>, Jeremie Le Hen <jlh@freebsd.org>, Bryan Drewery <bdrewery@freebsd.org> Subject: Re: PIE/PIC support on base Message-ID: <CADt0fhyCBa3PTnZ3dpc-hpysyC9V0MXR16s-e10V0ioAfaWHuw@mail.gmail.com> In-Reply-To: <315B4DC5-0E04-4F6B-BBB0-477D049025BF@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>
next in thread | previous in thread | raw e-mail | index | archive | help
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>...) otherwis= e > >>>>> 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 Brun= o. > >>> > >>> 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 car= ry > >> 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 ha= s > to > >>> worry about). On amd64, after symbol resolution has taken place, ther= e > >> 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) a= nd > > 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=E2=80=99t, > 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=E2=80=99t 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=E2=80=99t 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?)? Thanks, Shawn
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?CADt0fhyCBa3PTnZ3dpc-hpysyC9V0MXR16s-e10V0ioAfaWHuw>