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101 lines
4 KiB
Bash
101 lines
4 KiB
Bash
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#!/bin/sh
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# Regarding xdg-open in /etc/mailcap:
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#
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# It turns out that xdg-open is not very smart about what it
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# passes off control to, leading to security problems where (for
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# example) a file could be provided on a web site as a PDF, but
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# rather than send it to a PDF viewer, xdg-open sends it to kfmclient
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# which uses a whole different set of criteria to determine what sort
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# of file it is. It's trivial to make something that's detected as
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# a PDF at first, but then is executed as a .desktop file later,
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# resulting in the execution of arbitrary code as the user.
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#
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# This is not acceptable, and we see no way to fix it as long as
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# xdg-open passes off the resolution of the file type (again) to
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# something else. In light of the potential security risks, we
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# will turn off the use of xdg-open if it appears to have been
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# added by a previous version of the xdg-utils package.
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#
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# Vulnerability code: CVE-2009-0068
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# First, we will detect an automatically modified mailcap by
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# looking for the comment "# Sample xdg-open entries:"
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if [ -r etc/mailcap ]; then
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if grep -q "^# Sample xdg-open entries:$" etc/mailcap ; then
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COOKIE=$(usr/bin/mcookie)
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if [ -z $COOKIE ]; then
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exit 1
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fi
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# First, add a space to the end of the comment used to detect this
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# junk so that we won't detect it again (in case the user decides
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# to enable this themselves later on -- their call). Add a warning
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# about this type of xdg-open use being insecure. Finally, comment
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# out any lines like this.
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echo "# Sample xdg-open entries: " > tmp/mailcap-$COOKIE
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cat << EOF >> tmp/mailcap-$COOKIE
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#
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# NOTE: Using xdg-open in /etc/mailcap in this way has been
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# shown to be insecure and is not recommended (CVE-2009-0068)!
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# A remote attacker can easily make a filetype such as a
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# .desktop script appear to xdg-open as a PDF file causing its
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# arbitrary contents to be executed. Consider these to be
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# examples of what NOT to do. The xdg-utils package no longer
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# adds any lines such as these to /etc/mailcap.
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#
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EOF
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cat etc/mailcap \
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| grep -v "# Sample xdg-open entries:" \
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| sed -e 's/^audio\/\*; \/usr\/bin\/xdg-open %s/#audio\/\*; \/usr\/bin\/xdg-open %s/g' \
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| sed -e 's/^image\/\*; \/usr\/bin\/xdg-open %s/#image\/\*; \/usr\/bin\/xdg-open %s/g' \
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| sed -e 's/^application\/msword; \/usr\/bin\/xdg-open %s/#application\/msword; \/usr\/bin\/xdg-open %s/g' \
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| sed -e 's/^application\/pdf; \/usr\/bin\/xdg-open %s/#application\/pdf; \/usr\/bin\/xdg-open %s/g' \
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| sed -e 's/^application\/postscript ; \/usr\/bin\/xdg-open %s/#application\/postscript ; \/usr\/bin\/xdg-open %s/g' \
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| sed -e 's/^text\/html; \/usr\/bin\/xdg-open %s ; copiousoutput/#text\/html; \/usr\/bin\/xdg-open %s ; copiousoutput/g' >> tmp/mailcap-$COOKIE
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cat tmp/mailcap-$COOKIE > etc/mailcap
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rm -f tmp/mailcap-$COOKIE
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fi
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fi
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## BEGIN (HERE IS WHAT CAUSED THIS MESS):
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## Add some reasonable default values for xdg-open to /etc/mailcap,
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## since this is where many programs look for this information:
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#
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#if ! grep -q '# Sample xdg-open entries:' etc/mailcap 1> /dev/null 2> /dev/null ; then
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# echo "# Sample xdg-open entries:" >> etc/mailcap
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# echo >> etc/mailcap
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#fi
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#if ! grep -q 'audio/' etc/mailcap ; then
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# echo 'audio/*; /usr/bin/xdg-open %s' >> etc/mailcap
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# echo >> etc/mailcap
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#fi
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#if ! grep -q 'image/' etc/mailcap ; then
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# echo 'image/*; /usr/bin/xdg-open %s' >> etc/mailcap
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# echo >> etc/mailcap
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#fi
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#if ! grep -q 'application/msword' etc/mailcap ; then
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# echo 'application/msword; /usr/bin/xdg-open %s' >> etc/mailcap
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# echo >> etc/mailcap
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#fi
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#if ! grep -q 'application/pdf' etc/mailcap ; then
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# echo 'application/pdf; /usr/bin/xdg-open %s' >> etc/mailcap
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# echo >> etc/mailcap
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#fi
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#if ! grep -q 'application/postscript' etc/mailcap ; then
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# echo 'application/postscript ; /usr/bin/xdg-open %s' >> etc/mailcap
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# echo >> etc/mailcap
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#fi
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#if ! grep -q '#text/html' etc/mailcap ; then
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# echo '#text/html; /usr/bin/xdg-open %s ; copiousoutput' >> etc/mailcap
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# echo >> etc/mailcap
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#fi
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## END
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