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#!/bin/sh
# Check the presence of "mpost" in LaTeX sources
#
# A POC of an arbitrary code execution vulnerability in the default
# configuration of TeX packages was disclosed at
# https://scumjr.github.io/2016/11/28/pwning-coworkers-thanks-to-latex/.
# TeX Live 2016 is updated on November 30, 2016 to plug the security hole
# by removing "mpost" from the "shell_escape_commands" variable of default
# texmf configuration.
# However, depending on the customization of a user, he/she can still be
# affected after the update.
#
# To prevent exploitation of the vulnerability, this script checks
# if "mpost" is present in source files of perfbook.
# If the vulnerability is fixed in your TeX environment, the check is
# skipped.
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, you can access it online at
# http://www.gnu.org/licenses/gpl-2.0.html.
#
# Copyright (C) Akira Yokosawa, 2016, 2019
#
# Authors: Akira Yokosawa <akiyks@gmail.com>
#
#-------------------------------------------------------------------
# Instruction to plug the security hole
# (based on https://zrbabbler.hatenablog.com/entry/20161206/1481039449
# (in Japanese), translated and supplemented by Akira Yokosawa)
#
# 1. Test the config of your TeX environment
#
# Enter the following in a command shell:
#
# $ kpsewhich -var-value=shell_escape_commands
#
# Example output:
#
# bibtex,bibtex8,extractbb,kpsewhich,makeindex,mpost,repstopdf
#
# If "mpost" appears in the output, your setting is vulnerable.
# Following variants of "mpost" are also vulnerable:
# pmpost
# jmpost
# upmpost
#
# Note:
# "rmpost", "rpmpost", "r-mpost", "r-pmpost", and "r-upmpost"
# in the list are known to be safe.
#
# 2. Solution
#
# 2-1. Update TeX distribution if possible
#
# However, depending on your customization, you may still be vulnerable.
# Do Step 1 again after the update.
# If you are still vulnerable, proceed to Step 2-2.
#
# 2-2. Modify texmf configuration
#
# 2-2-1. Using tlmgr
#
# If tlmgr is available, enter the following command in a command shell:
#
# $ tlmgr conf texmf shell_escape_commands [list]
#
# Here, [list] is a command list displayed in Step 1 with "mpost," removed,
# e.g.:
#
# $ tlmgr conf texmf shell_escape_commands \
# > bibtex,bibtex8,extractbb,kpsewhich,makeindex,repstopdf
#
# 2-2-2. Manual fix
#
# If tlmgr is not available, proceed as follows:
#
# o Search effective texmf.cnf
#
# Enter the following command:
#
# $ kpsewhich texmf.cnf
#
# The path displayed is the effective one.
#
# o Edit the texmf.cnf to remove "mpost" from shell_escape_commands
#
# If there is a line beginning with "shell_escape_commands=" in the
# texmf.cnf file, edit it to remove "mpost,".
#
# If there is not such a line, add a line of:
#
# shell_escape_commands=[list]
#
# where [list] is again a command list displayed in Step 1 with "mpost,"
# removed, e.g.:
#
# shell_escape_commands=bibtex,bibtex8,extractbb,kpsewhich,makeindex,repstopdf
#
# Note:
# If the effective texmf.cnf has a comment saying not to edit it directly,
# follow the instruction given there.
#-------------------------------------------------------------------
: ${WHICH:=command -v}
dogrep() {
texsrc=`find . -name "*.tex" -print`
bibsrc=`find . -name "*.bib" -print`
stysrc=`find . -name "*.sty" -print`
clssrc=`find . -name "*.cls" -print`
bstsrc=`find . -name "*.bst" -print`
perfbooksrc="$texsrc $bibsrc $stysrc $clssrc $bstsrc"
if grep -w -n "mpost" $perfbooksrc || \
grep -w -n "[jp]mpost" $perfbooksrc || \
grep -w -n "upmpost" $perfbooksrc
then
echo "#####################################################"
echo "## 'mpost' is found in LaTeX sources. Aborting... ##"
echo "## Refer to comment in utilities/mpostcheck.sh. ##"
echo "#####################################################"
exit 1
fi
}
if $WHICH kpsewhich >/dev/null
then
command_list_orig=`kpsewhich -var-value=shell_escape_commands`
command_list=`echo $command_list_orig | sed -E "s/r-u?p?mpost,//g"`
if echo $command_list | grep -w -q "mpost" || \
echo $command_list | grep -w -q "[jp]mpost" || \
echo $command_list | grep -w -q "upmpost"
then
echo "kpsewhich -var-value=shell_escape_commands"
echo $command_list_orig
echo "WARNING: Refer to utilities/mpostcheck.sh for texmf config fix."
dogrep
else
exit 0
fi
else
dogrep
exit 0
fi
|
