> Bruce Momjian writes:
> > This brings up a question. If I have pid 333 and someone creates a file
> > world-writable called /tmp/333, and I go and do:
> > cat file >/tmp/$$
> > isn't another user now able to modify those temp file contents. Is that
> > the insecurity you mentioned Peter, and if so, how do you prevent this?
> That is one possibility. Another exploit is with a symlink from /tmp/333
> to a file you want to overwrite. This is more fun with root, but it's
> still not a good idea here.
> To securely create a temp file in shell you need to use mktemp(1), or do
> something like (umask 077 && mkdir $TMPDIR/$$) to create a subdirectory.
> Needless to say, it's tricky.
Wow, that symlink is a bad one. I don't see mktemp(1) on bsd/os, only
mktemp(3). I do see it on FreeBSD.
Good thing I don't have other shell users on my system. I do cat
>/tmp/$$ all the time in scripts.
Bruce Momjian | http://candle.pha.pa.us
pgman(at)candle(dot)pha(dot)pa(dot)us | (610) 853-3000
+ If your life is a hard drive, | 830 Blythe Avenue
+ Christ can be your backup. | Drexel Hill, Pennsylvania 19026
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