pkg audit false negatives (was: Perl upgrade - 5.20.x vulnerable)

[Roger Marquis]

On 16 Aug 2016, JosC wrote:
>> In the absence of running 'pkg audit -F', only
>> the"LOCALBASE/periodic/security/410.pkg-audit script updates the vuxml
>> file and audit results. Until that happens, or pkg audit -F is run, pkg
>> will still see an older version.
>
> Thinking with you I now ask myself:
> - Would it be a good idea to make this vuxml file update part of the 
> Makefile? Then these occurrences won't happen anymore

There's also an issue with older versions (perl 5.1*) no longer showing
up in the vuln.xml at all.  I've seen perl, php and other critical
network components still in use because the site depended on 'pkg audit'
but did not know that expired OR deprecated ports are not audited.
Apparently this is intentional and by policy.  IMO it is a serious flaw
in pkg audit's design.

A better policy would include expired AND deprecated ports in the output
of 'pkg audit' for at least a year after they are removed from the ports
and/or pkg trees.  If a port had no known vulnerability when removed it
should at least indicate 'no longer audited' in place of 'vulnerable'.

This is, IMO, one of 3 remaining weaknesses in the otherwise excellent
freebsd audit framework.  The other two issues have to do with base not
being packaged (so not really being 'audit'able) and the 'general rule'
announced on Aug 10 that 'the FreeBSD Security Officer does not announce
vulnerabilities for which there is no released patch'.  This is
particularly problematic as there are usually mitigations that do not
require patches.

Roger Marquis