Date: Thu, 18 Apr 2002 21:37:42 +0100 From: Ceri Davies <setantae@submonkey.net> To: Thomas Cannon <tcannon@noops.org> Cc: freebsd-questions@FreeBSD.ORG, security-officer@freebsd.org Subject: Re: I think this could be better Message-ID: <20020418203742.GA10603@submonkey.net> In-Reply-To: <20020418121731.O4793-100000@stereophonic.noops.org> References: <20020418121731.O4793-100000@stereophonic.noops.org>
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On Thu, Apr 18, 2002 at 01:03:54PM -0700, Thomas Cannon wrote:
> I just did a "make world" and noticed this go zipping by:
>
> mkdir -p /tmp/install.33931
> for prog in [ awk cat chflags chmod chown date echo egrep find grep ln
> make makewhatis mtree mv perl rm sed sh sysctl test true uname wc zic; do
> cp `which $prog` /tmp/install.33931; done
>
> I killed it and took a look around and saw that yes, indeed, we're
> running (via make) a shell script (as root) that makes temporary files in
> a world-writable directory, without checking to see if it exists first, with
> a predictable name. Then it indiscriminately deletes all of it.
While you're probably right to be concerned at use of a PID as a temporary
filename, in this instance I'm not sure it's so terrible :
{setantae@rhadamanth}-{/tmp} $ ln -s /etc.old/passwd install.35223
{setantae@rhadamanth}-{/tmp} # ls -l
total 154
-r--r--r-- 1 root wheel 11 Apr 18 17:00 .X0-lock
drwxrwxrwt 2 root wheel 512 Apr 18 17:00 .X11-unix
-rw-r--r-- 1 setantae wheel 149989 Apr 18 21:03 foo
lrwxr-xr-x 1 setantae wheel 15 Apr 18 21:26 install.35223 -> /etc.old/passwd
-rw-r--r-- 1 rasputin wheel 37 Apr 18 17:24 wtf
{setantae@rhadamanth}-{/tmp} $ su
Password:
{root@rhadamanth}-{/tmp} # mkdir -p install.35223
mkdir: install.35223: Permission denied
{root@rhadamanth}-{/tmp} #
> I could very easily be missing something. It frequently happens. I feel
> like I must be, as I'd expect developers to be more prudent and use a
> non-public temporary space just out of reflex. Is there some safety check
> that I'm not seeing?
I don't know if the above does actually mean that this is safe or not, but
it would be nice if we could avoid using a process id as a temporary filename.
Easy idea would be something like :
{setantae@rhadamanth}-{~} $ echo $$ `date -ju +%s` |md5
cc6de3ce1ec7064221d8495c2d74e9f4
but that's only unique once per second.
Ceri
--
get the cool shoe shine
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