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Message-ID: <20221023170300.GS29905@brightrain.aerifal.cx>
Date: Sun, 23 Oct 2022 13:03:01 -0400
From: Rich Felker <dalias@...c.org>
To: Ismael Luceno <ismael@...ev.co.uk>, musl@...ts.openwall.com
Subject: Re: [PATCH] remove strdupa
On Sun, Oct 23, 2022 at 11:13:42AM -0400, Rich Felker wrote:
> On Sun, Oct 23, 2022 at 04:10:46PM +0200, Szabolcs Nagy wrote:
> > * Rich Felker <dalias@...c.org> [2022-10-23 01:46:22 -0400]:
> > > On Sat, Oct 22, 2022 at 03:57:23PM +0200, Ismael Luceno wrote:
> > > > There's no portable way to implement strdupa without double evaluation
> > > > of it's parameter, and it's use leads to vulnerabilities, since there's
> > > > no chance to check for stack overruns.
> > > >
> > > > Signed-off-by: Ismael Luceno <ismael@...ev.co.uk>
> > > > ---
> > > > include/string.h | 1 -
> > > > 1 file changed, 1 deletion(-)
> > > >
> > > > diff --git a/include/string.h b/include/string.h
> > > > index 43ad0942edd5..65fe0d503004 100644
> > > > --- a/include/string.h
> > > > +++ b/include/string.h
> > > > @@ -88,7 +88,6 @@ void explicit_bzero (void *, size_t);
> > > > #endif
> > > >
> > > > #ifdef _GNU_SOURCE
> > > > -#define strdupa(x) strcpy(alloca(strlen(x)+1),x)
> > > > int strverscmp (const char *, const char *);
> > > > char *strchrnul(const char *, int);
> > > > char *strcasestr(const char *, const char *);
> > > > --
> > > > 2.38.1
> > >
> > > Does anyone have strong opinions one way or the other on this --
> > > especially distro folks who'd need to deal with the fallout?
> >
> > debian code search finds strdupa in 126 packages,
> > so it is widely used and not trivial to manually fix up,
> > i'd expect distros to just readd that definition to avoid breakage.
>
> Distros can of course add it with an ugly -D'strdupa(x)=...' in CFLAGS
> too, or with a one-line patch to the affected packages to add the
> #define. I would kinda expect some of these (likely any using
> autotools or especially gnulib) already handle the case where it's not
> defined and define their own, so maybe it wouldn't actually be that
> much breakage (but of course this would also be a reduction in
> bug-catching).
>
> I think a reasonable (but unsatisfying) outcome of this thread might
> end up being "do nothing until there's action to greatly reduce the
> number of packages using strdupa" (or at least evaluate the situation
> and determine that most would not break). I would really like to avoid
> "improving" interfaces that are harmful and slated for removal, but I
> also don't want to make unnecessary new burden on
> distros/integrators/users.
Extra data points from discussion on #alpine-devel: at least MacOS and
FreeBSD lack a strdupa macro. This means pretty much anything using it
is either non-portable OS-specific software or already has checks and
fallback cases for when it doesn't exist. So the breakage from
removing it might be very low.
Rich
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