[ Sorry for replying to the wrong message. I came across this thread
when making a decision on which netbsd lists to subscribe.  I can't
reply to original message because I don't have it. ]

This link might be of interest: http://www.openwall.com/pam/
especially pam_mktemp module. I was able to set it up on FreeBSD.
Though, I never tried it on NetBSD because I couldn't make ndis to
work on NetBSD.
I realise it's different from what you're discussing but given that
our time is limited, it makes sense to add existing code if it's
good enough.

-- 
Alexander Nasonov
http://nasonov.blogspot.com

The very idea of freedom presupposes some objective moral law which
overarches rulers and ruled alike. Subjectivism about values is
eternally incompatible with democracy. We and our rulers are of one
kind only so long as we are subject to one law. But if there is no
Law of Nature, the ethos of any society is the creation of its
rulers, educators and conditioners; and every creator stands above
and outside his own creation. -- C.S. Lewis --

This quote is generated by: 
	/usr/pkg/bin/curl -L http://tinyurl.com/veusy         \
	  | sed -e 's/^document\.write(.//' -e 's/.);$/ --/'  \
	        -e 's/<[^>]*>//g' -e 's/^More quotes from //' \
	  | fmt | tee ~/.signature-quote