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Re: [PATCH] Implement strlcpy, strlcat [BZ #178]
- From: Paul Eggert <eggert at cs dot ucla dot edu>
- To: Florian Weimer <fweimer at redhat dot com>, GNU C Library <libc-alpha at sourceware dot org>
- Date: Fri, 20 May 2016 10:21:05 -0700
- Subject: Re: [PATCH] Implement strlcpy, strlcat [BZ #178]
- Authentication-results: sourceware.org; auth=none
- References: <9f360d0a-56cd-19b7-a170-4f41037fcc2d at redhat dot com>
First, the September 2014 thread motivated strlcpy/strlcat in part by
saying that Fedora has over 60 packages which define strlcpy/strlcat,
the implication being that moving strlcpy/strlcat into glibc would fix
more bugs than it would cause and would be worth the effort's cost.
Skeptics like me can reasonably counter that the effort would likely
just be security theater, in that it would not be of any real help but
would merely exhibit activity in the security area, and possibly would
even cause more problems than it fixes.
Data could help assuage skeptics' concerns. Although it's impossible to
count bugs that are not discovered yet, we *do* now have twenty months'
worth of data since September 2014. So: how many user-visible bugs
and/or vulnerabilities have been discovered or reported in these 60-odd
Fedora packages, bugs that would have been prevented by moving
strlcpy/strlcat into a better-maintained library? New bugs cropping up
would argue for change. Quietude would suggest that we leave things alone.
Second, the September 2014 thread said that another way to fortify
strlcpy/strlcat, assuming we still want to do it, would be to use
libbsd's strlcpy/strlcat implementation and add fortification to it.
However, it was argued that this would be a Fedora-only effort and that
libbsd contains functions like fgetln that are awkward. But isn't the
point of libbsd to provide BSD functions that are awkward or
questionable from the glibc point of view? And I don't see how work in
libbsd would be Fedora-only, as other distributions like Debian also use
libbsd, and whatever methods Fedora uses to merge strlcpy/strlcat into
string.h would be methods that other distributions could use as well.
The Fedora bug report that corresponds to strlcpy/strlcat
fortification says that this is "Priority low Severity low", and from
the above it appears that this is mainly a packaging problem instead of
being a necessary addition to the core libc API.