#!/bin/bash -e
# vim: set tabstop=8 shiftwidth=4 softtabstop=4 expandtab smarttab colorcolumn=80:
#
# Copyright (c) 2017 Red Hat, Inc.
# Author: Javier Martinez Canillas <javierm@redhat.com>
#
# 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 3 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, see <http://www.gnu.org/licenses/>.
#

# The owner hierarchy is the one that should be used by the Operating System.
auth="o"

function on_exit() {
    if ! rm -r $TMP; then
        echo "Delete temporary files failed!" >&2
        exit 1
    fi
}

[ $# -eq 1 -a "$1" == "--summary" ] && exit 1

if [ -t 0 ]; then
    echo >&2
    echo "Usage: clevis decrypt tpm2 < JWE > PLAINTEXT" >&2
    echo >&2
    exit 1
fi

export TPM2TOOLS_TCTI_NAME=device
export TPM2TOOLS_DEVICE_FILE=`ls /dev/tpmrm? 2>/dev/null`

if [ -z "${TPM2TOOLS_DEVICE_FILE[0]}" ]; then
    echo "A TPM2 device with the in-kernel resource manager is needed!" >&2
    exit 1
fi

if ! [[ -r "${TPM2TOOLS_DEVICE_FILE[0]}" && -w "${TPM2TOOLS_DEVICE_FILE[0]}" ]]; then
    echo "The ${TPM2TOOLS_DEVICE_FILE[0]} device must be readable and writable!" >&2
    exit 1
fi

read -d . hdr

if ! jhd=`jose b64 dec -i- <<< "$hdr"`; then
    echo "Error decoding JWE protected header!" >&2
    exit 1
fi

if [ `jose fmt -j- -Og clevis -g pin -u- <<< "$jhd"` != "tpm2" ]; then
    echo "JWE pin mismatch!" >&2
    exit 1
fi

if ! hash=`jose fmt -j- -Og clevis -g tpm2 -g hash -Su- <<< "$jhd"`; then
    echo "JWE missing required 'hash' header parameter!" >&2
    exit 1
fi

if ! key=`jose fmt -j- -Og clevis -g tpm2 -g key -Su- <<< "$jhd"`; then
    echo "JWE missing required 'key' header parameter!" >&2
    exit 1
fi

if ! jwk_pub=`jose fmt -j- -Og clevis -g tpm2 -g jwk_pub -Su- <<< "$jhd"`; then
    echo "JWE missing required 'key' header parameter!" >&2
    exit 1
fi

if ! jwk_priv=`jose fmt -j- -Og clevis -g tpm2 -g jwk_priv -Su- <<< "$jhd"`; then
    echo "JWE missing required 'key' header parameter!" >&2
    exit 1
fi

if ! TMP=`mktemp -d`; then
    echo "Creating a temporary dir for TPM files failed!" >&2
    exit 1
fi

trap 'on_exit' EXIT

pcr_ids=`jose fmt -j- -Og clevis -g tpm2 -g pcr_ids -Su- <<< "$jhd"` || true

if [ -n "$pcr_ids" ]; then
    pcr_bank=`jose fmt -j- -Og clevis -g tpm2 -g pcr_bank -Su- <<< "$jhd"`
    policy_options="-L $pcr_bank:$pcr_ids"
fi

if ! `jose b64 dec -i- -O $TMP/jwk.pub <<< "$jwk_pub"`; then
    echo "Decoding jwk.pub from Base64 failed!" >&2
    exit 1
fi

if ! `jose b64 dec -i- -O $TMP/jwk.priv <<< "$jwk_priv"`; then
    echo "Decoding jwk.priv from Base64 failed!" >&2
    exit 1
fi

if ! tpm2_createprimary -Q -H "$auth" -g "$hash" -G "$key" \
     -C $TMP/primary.context 2>/dev/null; then
    echo "Creating TPM2 primary key failed!" >&2
    exit 1
fi

if ! tpm2_load -Q -c $TMP/primary.context -u $TMP/jwk.pub -r $TMP/jwk.priv \
     -C $TMP/load.context 2>/dev/null; then
    echo "Loading jwk to TPM2 failed!" >&2
    exit 1
fi

if ! jwk=`tpm2_unseal -c $TMP/load.context $policy_options 2>/dev/null`; then
    echo "Unsealing jwk from TPM failed!" >&2
    exit 1
fi

jose jwe dec -k- -i- < <(echo -n "$jwk$hdr."; cat)