Thread: Re: [COMMITTERS] pgsql/src/bin/initdb initdb.sh

> 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@candle.pha.pa.us               |  (610)
853-3000+  If your life is a hard drive,     |  830 Blythe Avenue +  Christ can be your backup.        |  Drexel Hill,
Pennsylvania19026
 

Bruce Momjian writes:

> > 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.

I see we have temp file vulnerabilities in genbki.sh and Gen_fmgrtab.sh as
well.  I'll try to fix them.

-- 
Peter Eisentraut   peter_e@gmx.net   http://funkturm.homeip.net/~peter

> Bruce Momjian writes:
> 
> > > 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.
> 
> I see we have temp file vulnerabilities in genbki.sh and Gen_fmgrtab.sh as
> well.  I'll try to fix them.

What is the vulnerability?  I see:
- if [ "$TMPDIR" ]; then-     TEMPFILE="$TMPDIR/initdb.$$"- else-     TEMPFILE="/tmp/initdb.$$"- fi


--  Bruce Momjian                        |  http://candle.pha.pa.us pgman@candle.pha.pa.us               |  (610)
853-3000+  If your life is a hard drive,     |  830 Blythe Avenue +  Christ can be your backup.        |  Drexel Hill,
Pennsylvania19026