[1701] in linux-security and linux-alert archive
[linux-security] Re: Re: Re: Towards a solution of tmp-file problems (fwd)
daemon@ATHENA.MIT.EDU (Nick Andrew)
Thu Mar 12 04:11:55 1998
From: Nick Andrew <nick@zeta.org.au>
To: linux-security@redhat.com
Date: Thu, 12 Mar 1998 08:55:19 +1100 (EST)
Resent-From: linux-security@redhat.com
Reply-To: linux-security@redhat.com
Forwarding a message from Steve \"Stevers!\" Coile:
> This is already possible. Create the file then unlink it. The file
> contents aren't deleted and i-node isn't released until the file is
> closed.
Without kernel support, unlinking the file at creation time requires
a code change in the process which creates the file. And this doesn't
protect scripts which use temp files for communication between their
subprocesses, e.g.
#!/bin/sh
cat > /tmp/a.$$
awk ' { print $1 } ' < /tmp.a.$$ | sort -o /tmp/field1.$$
awk ' { print $2 } ' < /tmp.a.$$ | sort -o /tmp/field2.$$
paste /tmp/field1.$$ /tmp/field2.$$
rm -f /tmp/a.$$ /tmp/field1.$$ /tmp/field2.$$
exit 0
A private namespace protects this script and its subprocesses by making the
files _totally_ inaccessible to unrelated processes. The private namespace
can be imposed from above or the script can define its own.
Nick.
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