You noted: > Even if the $tmpdir exists, it may not be the one created by the script. This is true, but I guess that is one of the 'risks' one takes when trying to do atomic locking with shell scripting... :) :( Would it be possible to write a small compiled program that could do the "atomically create unique file/directory and return it's name" program? This is getting waaayyyy out of scope for 'fixing' the script in your example but it is one of the few ways I see to get around it. Or see if the shell you are running under has an atomic check and create subroutine...probably not. :( On the flip side, since "$tmpdir" is made up of the PID of the script, then there is a much smaller chance of using a pre-existing directory. If you append the current system time (i.e. epoc micro-seconds) this should help quite a lot. Of course, these tricks don't help if your script is running on an embedded machine or before the time has been properly set to the world time... Good luck! Dan -----Original Message----- From: Jeremy C. Reed [mailto:reed@xxxxxxxxxxxxx] Sent: Tue 10/28/2003 2:58 PM To: security-discuss@xxxxxxxxxxxxxxxxx Cc: Subject: RE: tmp issues: trap before making safe tmp and no change directory On Tue, 28 Oct 2003, Daniel Linder wrote: > Rather than using another value for the "needsCleanup" variable, why > not use the test of the existance of "$tmpdir" as the value for your > "needsCleanup" value? I.e. replace "$needsCleanup" with a subroutine > that returns "true" if the "$tmpdir" exists? Is there a bad race > condition here? (Just to note, this is not my code.) Even if the $tmpdir exists, it may not be the one created by the script. I guess it could check to see if it is not a symlink. (But I think the trap should just be done after it is safely created.) And the "rm -f $tmpdir/*" cleanup potentially can happen before the script safely attempts to create its own tmpdir. Jeremy C. Reed http://bsd.reedmedia.net/ ------------------------------------------------------------------------ To unsubscribe email security-discuss-request@xxxxxxxxxxxxxxxxx with "unsubscribe" in the subject of the message. ÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿN‹§²æìr¸›yé[ rêâ·/ÝÇ.²Ïëz«ž²ßåŠ{±±ç.®+rýÊ&Â+aþéì ®&Þþ)í…ë.n7œ¶‡í…éÆ
