Re: Initial implementation of _FORTIFY_SOURCE

On 5/13/24 18:05, Tomoaki AOKI wrote:
> On Mon, 13 May 2024 18:57:26 +0000
> Shawn Webb <shawn.webb@hardenedbsd.org> wrote:
> 
>> On Mon, May 13, 2024 at 11:09:24AM -0700, Cy Schubert wrote:
>>> In message <f8000e6b-226b-45f3-a751-aca790f4f8c8@FreeBSD.org>, Kyle Evans
>>> write
>>> s:
>>>> Hi,
>>>>
>>>> As of 9bfd3b407 ("Add a build knob for _FORTIFY_SOURCE"), I've imported
>>>> an initial version of FORTIFY_SOURCE from FreeBSD.  FORTIFY_SOURCE is an
>>>> improvement over classical SSP, doing compiler-aided checking of stack
>>>> object sizes to detect more fine-grained stack overflow without relying
>>>> on the randomized stack canary just past the stack frame.
>>>>
>>>> This implementation is not yet complete, but we've done a review of
>>>> useful functions and syscalls to add checked variants of and intend to
>>>> complete the implementation over the next month or so.
>>>>
>>>> Please test _FORTIFY_SOURCE out now by setting FORTIFY_SOURCE=2 in the
>>>> buildworld env -- I intend to flip the default to 2 when WITH_SSP is set
>>>> in the next month if nobody complains about serious breakage.  I've
>>>> personally been rolling with FORTIFY_SOURCE=2 for the last three years
>>>> that this has been sitting in a local branch, so I don't really
>>>> anticipate any super-fundamental breakage.
>>>
>>> Should this trigger a __FreeBSD_version bump?
>>
>> I would encourage that so to help the ports tree determine
>> availability of the import.
> 
> If it can be enabled/disabled with sysctls/tunables on runtime/boottime,
> bump should be preferred. Maybe this isn't yet the case here, IIUC.
> 
> But if it could be done only on build time with WITH_ or WITHOUT_ knob
> ad not yet enabled by default for now, now ins't the time to bump.
> Bump should be done when it becomes to be built by default.
> 
> Bump for non-default build time knob should force poudriere[-devel]
> users massive unneeded rebuilds. So should be avoided, if it still
> cannot switch on boot or runtime.
> 

It's strictly build time, and I didn't really see the value in bumping 
__FreeBSD_version for it.  I don't see any reason to, e.g., turn it into 
a per-port option that we may not want to have if the feature isn't 
there, and the knob to build it in is a preprocessor define that's 
harmless if the feature isn't actually available.

Thanks,

Kyle Evans