>From 35304561657c417ed2820664fa424feedc461fc2 Mon Sep 17 00:00:00 2001 From: Akira Yokosawa <akiyks@xxxxxxxxx> Date: Sat, 10 Dec 2016 15:38:34 +0900 Subject: [PATCH] Abort build if 'mpost' is present in sources A POC of an arbitrary command execution vulnerability in TeX config was disclosed on November 28, 2016. To avoid the exploitation, this commit adds checks just before latex invocations in runfirstlatex.sh, runlatex.sh, and the ".tex -> .eps" rule of Makefile. The added script "mpostcheck.sh" first checks if your config is secure. If it is not, then it aborts the build if a word "mpost" is found in the sources. (It is not present at the moment.) If "mpost" is not found, the build will continue. But mpostcheck.sh displays a warning message. To make sure the message can catch eyes, the script is also invoked at the end of runlatex.sh. Once you fix your TeX config, the behavior of the build scripts will be the same as before. Refer to the comment in mpostcheck.sh for the circumstances and instructions for fixing your TeX config. Signed-off-by: Akira Yokosawa <akiyks@xxxxxxxxx> --- Makefile | 1 + utilities/mpostcheck.sh | 149 +++++++++++++++++++++++++++++++++++++++++++++ utilities/runfirstlatex.sh | 5 ++ utilities/runlatex.sh | 5 ++ 4 files changed, 160 insertions(+) create mode 100644 utilities/mpostcheck.sh diff --git a/Makefile b/Makefile index efd4e1b..e125678 100644 --- a/Makefile +++ b/Makefile @@ -122,6 +122,7 @@ perfbook-1csf.tex: perfbook-1c.tex $(EPSSOURCES_FROM_TEX): %.eps: %.tex @echo "$< --> $@" + sh utilities/mpostcheck.sh @latex -output-directory=$(shell dirname $<) $< > /dev/null 2>&1 @dvips -Pdownload35 -E $(patsubst %.tex,%.dvi,$<) -o $@ > /dev/null 2>&1 @sh utilities/fixanepsfonts.sh $@ diff --git a/utilities/mpostcheck.sh b/utilities/mpostcheck.sh new file mode 100644 index 0000000..0e54923 --- /dev/null +++ b/utilities/mpostcheck.sh @@ -0,0 +1,149 @@ +#!/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 +# +# Authors: Akira Yokosawa <akiyks@xxxxxxxxx> +# +#------------------------------------------------------------------- +# Instruction to plug the security hole +# (based on http://d.hatena.ne.jp/zrbabbler/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" and "rpmpost" 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. +#------------------------------------------------------------------- + +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=`kpsewhich -var-value=shell_escape_commands` + 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 + echo "WARNING: Refer to utilities/mpostcheck.sh for texmf config fix." + dogrep + else + exit 0 + fi +else + dogrep + exit 0 +fi diff --git a/utilities/runfirstlatex.sh b/utilities/runfirstlatex.sh index ac2edb2..5060725 100644 --- a/utilities/runfirstlatex.sh +++ b/utilities/runfirstlatex.sh @@ -32,6 +32,11 @@ then exit 1 fi +if ! sh utilities/mpostcheck.sh +then + exit 1 +fi + basename=`echo $1 | sed -e 's/\.tex$//'` echo "pdflatex 1 for $basename.pdf" diff --git a/utilities/runlatex.sh b/utilities/runlatex.sh index dca728c..a577a0c 100644 --- a/utilities/runlatex.sh +++ b/utilities/runlatex.sh @@ -38,6 +38,10 @@ basename=`echo $1 | sed -e 's/\.tex$//'` if ! test -r $basename-first.log then + if ! sh utilities/mpostcheck.sh + then + exit 1 + fi echo "pdflatex 1 for $basename.pdf" pdflatex $basename > /dev/null 2>&1 < /dev/null || : if grep -q '! Emergency stop.' $basename.log @@ -129,4 +133,5 @@ then echo "## See item 1 in FAQ.txt and FAQ-BUILD.txt to fix the font issue. ##" echo "#######################################################################" fi +sh utilities/mpostcheck.sh exit 0 -- 2.7.4 -- To unsubscribe from this list: send the line "unsubscribe perfbook" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
