Re: Hardening

[Ludovic Courtès]

Leo Famulari <address@hidden> skribis:

> On Wed, Dec 30, 2015 at 05:06:30PM +0100, Ludovic Courtès wrote:
>> Alex Vong <address@hidden> skribis:
>> > Yes, I grep for `fstack-protector-strong' in the guix code base and no
>> > matches are found. It appears no packages are setting this flag
>> > currently. I think this flag (perhaps also a couple others) should be
>> > set by default since they help protect against buffer overflow
>> > <https://en.wikipedia.org/wiki/Buffer_overflow_protection>.
>> 
>> I definitely agree, that’s something I’ve been wanting to try out.
>> 
>> The question is more how.  Do we change the default #:configure-flags
>> for ‘gnu-build-system’ to something like:
>> 
>>   '("CPPFLAGS=-D_FORTIFY_SOURCE=2"
>>     "CFLAGS=-O2 -g -fstack-protector-strong")
>> 
>> ?
>> 
>> That sounds like a good starting point, but I expect that (1) one third
>> of the packages will fail to build, and (2) another third of the
>> packages will not get these flags, for instance because they pass their
>> own #:configure-flags.
>> 
>> IOW, it will take a whole rebuild to find out exactly what’s going on
>> and to fix any issues.
>> 
>> Would you like to start working on it?  Then we could create a branch,
>> have Hydra build it, and incrementally fix things.
>
> We should pick this project back up. I was suprised to find we haven't
> done anything like this after reading this recent blog post about Nix's
> hardening effort:
>
> https://blog.mayflower.de/5800-Hardening-Compiler-Flags-for-NixOS.html?utm_source=twitterfeed&utm_medium=twitter

Definitely!  As discussed on IRC, an option would be to add a keyword
parameter to ‘gnu-build-system’:

  #:hardening-flags '(fortify stack-protector)

Then ‘configure’ in (guix build gnu-build-system) would translate that
into CPPFLAGS and CFLAGS options for ‘configure’, as shown above.

The main difficulty with this is that many packages will break.  Thus,
if we make it opt-out, we’ll have to fix packages one by one.  It seems
unavoidable though.

Thoughts?

Ludo’.