Time to enable partial relro

[David Chisnall]

On 26 Aug 2016, at 15:18, Warner Losh <imp at bsdimp.com> wrote:
> 
> So what's the summary of why we'd want to do that? What benefit does it bring?
> Sure, other folks do it, but why?

It reduce the attack surface for code reuse attacks: non-PLT GOT entries are read-only and so can’t be manipulated by a memory safety bug.  It doesn’t provide much mitigation, but it also doesn’t cost very much - some security for a negligible cost is probably a sensible thing to pick.

When combined with RTLD_NOW, it provides more hardening, but at a much more significant cost (bigger startup times - much bigger for things like OpenOffice or Firefox, some forms of interposition break, and so on).  That’s still probably worth it for some things (sshd, for example).

David

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