Re: Hardening FreeBSD, does anyone have any documentation that may help?

On Tue, Nov 21, 2006 at 11:59:27AM +0000, Robert Watson wrote:
FYI, Silby gave a nice mini-talk/discussion at EuroBSDCon on the topic of
gcc4 security features. It seems like there's a lot of support for having
these things in FreeBSD, but a strong reluctance to have large outstanding
patchsets against the compiler and build chain, hence the continued
"strategy" of waiting for them to arrive in gcc4. Most questions boiled
down to:

The code is integrated in GCC 4.1, patching if needed at all is quite
contained.

- What are the ABI impacts? Assuming that protection features arrive and
depart, and that reasonable application backward compatibility is required
for programs and libraries. Of particular interest was the case where we
turn on a protection feature in X.Y and discover that this was a bad idea,
so turn it off in X.Y+1.

The ABI impact is limited to the stack guard cookie, the initialisation
function and the failure handler. Three different solutions can be used:
(1) The code can be part of a separate library (libssp).
(2) The code can be part of libc (DragonFly, OpenBSD and glibc do this).
(3) Like (2), but the cookie is part of the Thread Control Block, e.g.
accessible via %gs. This is done on newer glibc systems and has the
advantage of avoiding PIC references.

- What are the performance characteristics in a variety of real-world
workloads?

The original benchmarks done with Propolice by IBM suggest typical
degrations in the area of 2%-5%, depending on how many functions are
called and not inlined and how many of them need to get the protection.
The site of Etoh has more details.

Joerg
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