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# Initramfs unpacker - unpacks initramfs images into /tmp
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# Copyright © 2013-2019 Teddy Hogeborn
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# Copyright © 2013-2019 Björn Påhlsson
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# This file is part of Mandos.
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# Mandos is free software: you can redistribute it and/or modify it
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# under the terms of the GNU General Public License as published by
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# the Free Software Foundation, either version 3 of the License, or
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# (at your option) any later version.
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# Mandos is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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# You should have received a copy of the GNU General Public License
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# along with Mandos. If not, see
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# <http://www.gnu.org/licenses/>.
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# Contact the authors at <mandos@recompile.se>.
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cpio="cpio --extract --make-directories --unconditional --preserve-modification-time"
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set -- /boot/initrd.img-*
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for imgfile in "$@"; do
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if ! [ -f "$imgfile" ]; then
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echo "Error: Not an existing file: $imgfile" >&2
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imgdir="${TMPDIR:-/tmp}/${imgfile##*/}"
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if [ -d "$imgdir" ]; then
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rm --recursive -- "$imgdir"
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mkdir --parents "$imgdir"
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# Does this image contain microcode?
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if $cpio --quiet --list --file="$imgfile" >/dev/null 2>&1; then
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# Number of bytes to skip to get to the compressed archive
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skip=$(($(LANG=C $cpio --io-size=1 --list --file="$imgfile" 2>&1 \
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--expression='s/^\([0-9]\+\) blocks$/\1/p')+8))
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if [ -x /usr/lib/dracut/skipcpio ]; then
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catimg="/usr/lib/dracut/skipcpio $imgfile"
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catimg="dd if=$imgfile bs=$skip skip=1 status=noxfer"
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echo "No microcode detected"
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catimg="cat -- $imgfile"
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# Determine the compression method
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if { $catimg 2>/dev/null | zcat --test >/dev/null 2>&1;
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[ ${PIPESTATUS[-1]} -eq 0 ]; }; then
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elif { $catimg 2>/dev/null | bzip2 --test >/dev/null 2>&1;
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[ ${PIPESTATUS[-1]} -eq 0 ]; }; then
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decomp="bzip2 --stdout --decompress"
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elif { $catimg 2>/dev/null | lzop --test >/dev/null 2>&1;
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[ ${PIPESTATUS[-1]} -eq 0 ]; }; then
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decomp="lzop --stdout --decompress"
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elif { $catimg 2>/dev/null | zstd --test >/dev/null 2>&1;
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[ ${PIPESTATUS[-1]} -eq 0 ]; }; then
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decomp="zstdcat --stdout --decompress"
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echo "Could not determine compression of ${imgfile}; trying to skip ${skip} bytes" >&2
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catimg="dd if=$imgfile bs=$skip skip=1 status=noxfer"
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*skipcpio*) echo "Microcode detected, skipping";;
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*) echo "Microcode detected, skipping ${skip} bytes";;
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$catimg 2>/dev/null | $decomp | ( cd -- "$imgdir" && $cpio --quiet )
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if [ ${PIPESTATUS[-1]} -eq 0 ]; then
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echo "$imgfile unpacked into $imgdir"