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https://github.com/edgelesssys/constellation.git
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77 lines
2.0 KiB
Bash
Executable File
77 lines
2.0 KiB
Bash
Executable File
#!/usr/bin/env bash
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# Copyright (c) Edgeless Systems GmbH
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#
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# SPDX-License-Identifier: AGPL-3.0-only
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# This script is used to precalculate the PCR[12] value for a Constellation OS image.
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# PCR[12] contains the hash of the kernel command line and is measured by systemd-boot.
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# This value was previously measured into PCR[8].
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# This script may produce wrong results for systemd-boot versions < 251.
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# Usage: precalculate_pcr_12.sh <path to image> <path to output file> <csp>
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set -euo pipefail
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shopt -s inherit_errexit
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source "$(dirname "$0")/measure_util.sh"
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get_cmdline_from_uki() {
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local uki="$1"
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local output="$2"
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objcopy -O binary --only-section=.cmdline "${uki}" "${output}"
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}
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cmdline_measure() {
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local path="$1"
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local tmp
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tmp=$(mktemp)
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# convert to utf-16le and add a null terminator
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iconv -f utf-8 -t utf-16le "${path}" -o "${tmp}"
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truncate -s +2 "${tmp}"
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sha256sum "${tmp}" | cut -d " " -f 1
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rm "${tmp}"
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}
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write_output() {
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local out="$1"
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cat > "${out}" << EOF
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{
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"measurements": {
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"12": "${expected_pcr_12}"
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},
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"cmdline": "${cmdline}",
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"cmdline-sha256": "${cmdline_hash}"
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}
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EOF
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}
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IMAGE="$1"
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OUT="$2"
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CSP="$3"
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DIR=$(mktempdir)
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trap 'cleanup "${DIR}"' EXIT
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extract "${IMAGE}" "/efi/EFI/Linux" "${DIR}/uki"
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sudo chown -R "${USER}:${USER}" "${DIR}/uki"
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cp "${DIR}"/uki/*.efi "${DIR}/03-uki.efi"
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get_cmdline_from_uki "${DIR}/03-uki.efi" "${DIR}/cmdline"
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cmdline=$(cat "${DIR}/cmdline")
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cmdline_hash=$(cmdline_measure "${DIR}/cmdline")
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cleanup "${DIR}"
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expected_pcr_12=0000000000000000000000000000000000000000000000000000000000000000
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expected_pcr_12=$(pcr_extend "${expected_pcr_12}" "${cmdline_hash}" "sha256sum")
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if [[ ${CSP} == "azure" ]]; then
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# Azure displays the boot menu
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# triggering an extra measurement of the kernel command line.
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expected_pcr_12=$(pcr_extend "${expected_pcr_12}" "${cmdline_hash}" "sha256sum")
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fi
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echo "Kernel commandline: ${cmdline}"
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echo "Kernel Commandline measurement ${cmdline_hash}"
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echo ""
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echo "Expected PCR[12]: ${expected_pcr_12}"
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echo ""
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write_output "${OUT}"
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