[1705] in linux-security and linux-alert archive
[linux-security] Re: Re: Re: Re: Towards a solution of tmp-file problems
daemon@ATHENA.MIT.EDU (Grant Kaufmann)
Fri Mar 13 01:50:54 1998
Date: Thu, 12 Mar 1998 11:43:44 +0200
From: Grant Kaufmann <grant@intekom.com>
To: linux-security@redhat.com
Resent-From: linux-security@redhat.com
Reply-To: linux-security@redhat.com
Aleph One wrote:
>
> On Thu, 12 Mar 1998, Nick Andrew wrote:
>
> > This is not a solution intended to allow users to share files - sharing and
> > protecting are mutually exclusive requirements; let them share files
> > somewhere else.
>
> This touches on the core problem of why even though the /tmp problem is as
> old as UNIX is has never been fixed. There has just never been a standard
> definition of what /tmp is used for. Every solution everyone has proposed
> break one of the uses of /tmp. It used for temporary disk space, temporary
> files, interprocess communication between process of the same uid,
> IPC between processes of different uids, etc. Why one do you want to give
> up?
This is the fundamental issue. /tmp is a common temporary storage location.
The _problem_ is that programmers don't treat it as such. They treat it as
a secure storage location. Its a mindset that needs to be changed. By
honouring $TMPDIR, it would be a start.
> [REW: (Some of the...) Comments in the source, and, as far as I can
> see, the source itself, say that O_EXCL in 2.1.x means that no
> symlinks will be followed on the final stretch. This disagrees with
> the majority (but not all) of the unices out there, but is required to
> make things secure. "varlinks" are working over here ;-) ]
If we are suggesting a new FS, we're not really concerned with portability.
Would anything break if O_CREAT|O_EXCL was guaranteed by the kernel to be
atomic and to not follow links? Several OS's (at least one, anyway) do
support this and it does give the programmer one more secure programming
tool.
[mod: The example for "at least one" is "Linux-2.1.x". -- REW]
--
Grant
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