Add POSIX shell compliant zlevis-decrypt.
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147
src/zlevis-decrypt
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147
src/zlevis-decrypt
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#!/bin/sh
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# Exit immediately if a command exits with a non-zero status
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set -e
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# Summary of the script's functionality
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summary="Decrypts a JWE using a TPM2.0 chip."
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# TPM2.0 owner hierarchy to be used by the Operating System
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auth="o"
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# Display summary if requested
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if [ "$1" = "--summary" ]; then
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echo "$summary"
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exit 0
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fi
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# Display usage information if input is from a terminal
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if [ -t 0 ]; then
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exec >&2
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echo
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echo "Usage: \"zlevis-decrypt < file.jwe\""
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echo "Usage ZFS: \"zfs list -Ho tpm:jwe <pool> | zlevis-decrypt\""
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echo
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echo "$summary"
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exit 2
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fi
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# Function to clean up temporary files on exit
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on_exit() {
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if [ ! -d "$tmp" ] || ! rm -rf "$tmp"; then
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echo "Delete temporary files failed" >&2
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echo "You need to clean up: $tmp" >&2
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exit 1
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fi
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}
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# Get the version of tpm2-tools
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tpm2tools_version=$(tpm2_createprimary -v | awk -F'version="' '{print $2}' | awk -F'.' '{print $1}')
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# Check if the tpm2-tools version is supported
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if [ -z "$tpm2tools_version" ] || [ "$tpm2tools_version" -lt 4 ] || [ "$tpm2tools_version" -gt 5 ]; then
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echo "The tpm2 pin requires a tpm2-tools version between 4 and 5"
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exit 1
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fi
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# Create a temporary directory for TPM files
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if ! tmp="$(mktemp -d)"; then
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echo "Creating a temporary dir for TPM files failed" >&2
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exit 1
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fi
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# Set up cleanup on exit
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trap 'on_exit' EXIT
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# Read the JWE protected header
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read -r -d . hdr
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# Decode the JWE protected header
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if ! jhd="$(jose b64 dec -i- < <(echo "$hdr"))"; then
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echo "Error decoding JWE protected header" >&2
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exit 1
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fi
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echo "$jhd" > "$tmp"/jhd
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# Validate the JWE pin type
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if [ "$(jose fmt -j- -Og clevis -g pin -u- < "$tmp"/jhd)" != "tpm2" ]; then
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echo "JWE pin mismatch" >&2
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exit 1
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fi
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# Extract required parameters from the JWE header
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if ! hash="$(jose fmt -j- -Og clevis -g tpm2 -g hash -Su- < "$tmp"/jhd)"; then
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echo "JWE missing required 'hash' header parameter!" >&2
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exit 1
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fi
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if ! key="$(jose fmt -j- -Og clevis -g tpm2 -g key -Su- < "$tmp"/jhd)"; then
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echo "JWE missing required 'key' header parameter!" >&2
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exit 1
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fi
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if ! jwk_pub="$(jose fmt -j- -Og clevis -g tpm2 -g jwk_pub -Su- < "$tmp"/jhd)"; then
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echo "JWE missing required 'jwk_pub' header parameter!" >&2
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exit 1
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fi
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echo "$jwk_pub" > "$tmp"/jwk_pub
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if ! jwk_priv="$(jose fmt -j- -Og clevis -g tpm2 -g jwk_priv -Su- < "$tmp"/jhd)"; then
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echo "JWE missing required 'jwk_priv' header parameter!" >&2
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exit 1
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fi
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echo "$jwk_priv" > "$tmp"/jwk_priv
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# Handle optional PCR parameters
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pcr_ids="$(jose fmt -j- -Og clevis -g tpm2 -g pcr_ids -Su- < "$tmp"/jhd)" || true
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pcr_spec=""
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if [ -n "$pcr_ids" ]; then
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pcr_bank="$(jose fmt -j- -Og clevis -g tpm2 -g pcr_bank -Su- < "$tmp"/jhd)"
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pcr_spec="$pcr_bank:$pcr_ids"
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fi
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# Decode the public and private keys from Base64
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if ! jose b64 dec -i- -O "$tmp"/jwk.pub < "$tmp"/jwk_pub; then
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echo "Decoding jwk.pub from Base64 failed" >&2
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exit 1
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fi
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if ! jose b64 dec -i- -O "$tmp"/jwk.priv < "$tmp"/jwk_priv; then
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echo "Decoding jwk.priv from Base64 failed" >&2
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exit 1
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fi
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# Create the primary key in the TPM
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case "$tpm2tools_version" in
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4|5) tpm2_createprimary -Q -C "$auth" -g "$hash" -G "$key" -c "$tmp"/primary.context || fail=$?;;
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*) fail=1;;
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esac
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if [ -n "$fail" ]; then
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echo "Creating TPM2 primary key failed" >&2
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exit 1
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fi
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tpm2_flushcontext -t
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# Load the JWK into the TPM
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case "$tpm2tools_version" in
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4|5) tpm2_load -Q -C "$tmp"/primary.context -u "$tmp"/jwk.pub -r "$tmp"/jwk.priv -c "$tmp"/load.context || fail=$?;;
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*) fail=1;;
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esac
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if [ -n "$fail" ]; then
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echo "Loading jwk to TPM2 failed" >&2
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exit 1
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fi
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tpm2_flushcontext -t
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# Unseal the JWK from the TPM
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case "$tpm2tools_version" in
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4|5) jwk="$(tpm2_unseal -c "$tmp/load.context" ${pcr_spec:+-p pcr:$pcr_spec})" || fail=$?;;
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*) fail=1;;
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esac
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if [ -n "$fail" ]; then
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echo "Unsealing jwk from TPM failed" >&2
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exit 1
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fi
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tpm2_flushcontext -t
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# Output the decrypted JWK along with the original header
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(echo "$jwk$hdr."; /bin/cat) | jose jwe dec -k- -i-
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# Exit with the status of the last command
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exit $?
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