clevis-encrypt-tpm2

#!/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/>.
#

SUMMARY="Encrypts using a TPM2.0 chip binding policy"
# The owner hierarchy is the one that should be used by the Operating System.
auth="o"
# Algorithm type must be keyedhash for object with user provided sensitive data.
alg_create_key="keyedhash"
# Attributes for the created TPM2 object with the JWK as sensitive data.
obj_attr="fixedtpm|fixedparent|noda|adminwithpolicy"

function on_exit() {
    if [ ! -d "$TMP" ] || ! rm -rf "$TMP"; then
        echo "Delete temporary files failed!" >&2
        echo "You need to clean up: $TMP" >&2
        exit 1
    fi
}

if [ "$1" == "--summary" ]; then
    echo "$SUMMARY"
    exit 0
fi

if [ -t 0 ]; then
    exec >&2
    echo
    echo "Usage: clevis encrypt tpm2 CONFIG < PLAINTEXT > JWE"
    echo
    echo "$SUMMARY"
    echo
    echo "This command uses the following configuration properties:"
    echo
    echo "  hash: <string>  Hash algorithm used in the computation of the object name (default: sha256)"
    echo
    echo "  key: <string>   Algorithm type for the generated key (default: ecc)"
    echo
    echo "  pcr_bank: <string>   PCR algorithm bank to use for policy (default: sha1)"
    echo
    echo "  pcr_ids: <string>   PCR list used for policy. If not present, no policy is used"
    echo
    echo "  pcr_digest: <string>   Binary PCR hashes encoded in base64. If not present, the hash values are looked up"
    echo
    exit 2
fi

validate_pcrs() {
    local _tpm2_tools_v="${1}"
    local _pcr_bank="${2}"
    local _pcrs="${3}"
    [ -z "${_pcr_bank}" ] && return 1
    [ -z "${_pcrs}" ] && return 0

    local _fail=
    local _pcrs_r=
    case "${_tpm2_tools_v}" in
    3) _pcrs_r="$(tpm2_pcrlist -L "${_pcr_bank}":"${_pcrs}" | grep -v "^${_pcr_bank}")" || _fail=$?;;
    4|5) _pcrs_r=$(tpm2_pcrread "${_pcr_bank}":"${_pcrs}" | grep -v "  ${_pcr_bank}")  || _fail=$?;;
    *) _fail=1
    esac

    if [ -n "${_fail}" ] || [ -z "${_pcrs_r}" ]; then
        return 1
    fi
    return 0
}

TPM2TOOLS_INFO="$(tpm2_createprimary -v)"

match='version="(.)\.'
[[ $TPM2TOOLS_INFO =~ $match ]] && TPM2TOOLS_VERSION="${BASH_REMATCH[1]}"
if [[ $TPM2TOOLS_VERSION -lt 3 ]] || [[ $TPM2TOOLS_VERSION -gt 5 ]]; then
    echo "The tpm2 pin requires a tpm2-tools version between 3 and 5" >&2
    exit 1
fi

if [ -z "$TPM2TOOLS_TCTI" ]; then
    # Old environment variables for tpm2-tools 3.0
    export TPM2TOOLS_TCTI_NAME=device
    export TPM2TOOLS_DEVICE_FILE=
    for dev in /dev/tpmrm?; do
        [ -e "$dev" ] || continue
        TPM2TOOLS_DEVICE_FILE="$dev"
        break
    done

    # New environment variable for tpm2-tools >= 3.1
    export TPM2TOOLS_TCTI="$TPM2TOOLS_TCTI_NAME:$TPM2TOOLS_DEVICE_FILE"

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

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

if ! cfg="$(jose fmt -j "$1" -Oo- 2>/dev/null)"; then
    echo "Configuration is malformed!" >&2
    exit 1
fi

hash="$(jose fmt -j- -Og hash -u- <<< "$cfg")" || hash="sha256"

key="$(jose fmt -j- -Og key -u- <<< "$cfg")" || key="ecc"

pcr_bank="$(jose fmt -j- -Og pcr_bank -u- <<< "$cfg")" || pcr_bank="sha1"

# Trim the spaces from the config, so that we will not have issues parsing
# the PCR IDs.
pcr_cfg=${cfg//[[:space:]]/}
# Issue #103: We support passing pcr_ids using both a single string, as in
# "1,3", as well as an actual JSON array, such as ["1","3"]. Let's handle both
# cases here.
if jose fmt -j- -Og pcr_ids 2>/dev/null <<< "${pcr_cfg}" \
    && ! pcr_ids="$(jose fmt -j- -Og pcr_ids -u- 2>/dev/null \
                    <<< "${pcr_cfg}")"; then

    # We failed to parse a string, so let's try to parse a JSON array instead.
    if jose fmt -j- -Og pcr_ids -A 2>/dev/null <<< "${pcr_cfg}"; then
        # OK, it is an array, so let's get the items and form a string.
        pcr_ids=
        for pcr in $(jose fmt -j- -Og pcr_ids -Af- <<< "${pcr_cfg}" \
                     | tr -d '"'); do
            pcr_ids=$(printf '%s,%s' "${pcr_ids}" "${pcr}")
        done
        # Now let's remove the leading comma.
        pcr_ids=${pcr_ids/#,/}
    else
        # Not to add a policy that was not intended, in this case, no policy
        # at all, let's report the issue and exit.
        echo "Parsing the requested policy failed!" >&2
        exit 1
    fi
fi

if ! validate_pcrs "${TPM2TOOLS_VERSION}" "${pcr_bank}" "${pcr_ids}"; then
    echo "Unable to validate combination of PCR bank '${pcr_bank}' and PCR IDs '${pcr_ids}'." >&2
    exit 1
fi

pcr_digest="$(jose fmt -j- -Og pcr_digest -u- <<< "$cfg")" || true

if ! jwk="$(jose jwk gen -i '{"alg":"A256GCM"}')"; then
    echo "Generating a jwk failed!" >&2
    exit 1
fi

mkdir -p "${TMPDIR:-/tmp}"
if ! TMP="$(mktemp -d)"; then
    echo "Creating a temporary dir for TPM files failed!" >&2
    exit 1
fi

trap 'on_exit' EXIT

case "$TPM2TOOLS_VERSION" in
    3) tpm2_createprimary -Q -H "$auth" -g "$hash" -G "$key" -C "$TMP"/primary.context || fail=$?;;
    4|5) tpm2_createprimary -Q -C "$auth" -g "$hash" -G "$key" -c "$TMP"/primary.context || fail=$?;;
    *) fail=1;;
esac
if [ -n "$fail" ]; then
    echo "Creating TPM2 primary key failed!" >&2
    exit 1
fi
tpm2_flushcontext -t

policy_options=()
if [ -n "$pcr_ids" ]; then
    if [ -z "$pcr_digest" ]; then
        case "$TPM2TOOLS_VERSION" in
            3) tpm2_pcrlist -Q -L "$pcr_bank":"$pcr_ids" -o "$TMP"/pcr.digest || fail=$?;;
            4|5) tpm2_pcrread -Q "$pcr_bank":"$pcr_ids" -o "$TMP"/pcr.digest || fail=$?;;
            *) fail=1;;
        esac
        if [ -n "$fail" ]; then
            echo "Creating PCR hashes file failed!" >&2
            exit 1
        fi
        tpm2_flushcontext -t
    else
        if ! jose b64 dec -i- -O "$TMP"/pcr.digest <<< "$pcr_digest"; then
            echo "Error decoding PCR digest!" >&2
            exit 1
        fi
    fi

    case "$TPM2TOOLS_VERSION" in
        3) tpm2_createpolicy -Q -g "$hash" -P -L "$pcr_bank":"$pcr_ids" \
                             -F "$TMP"/pcr.digest -f "$TMP"/pcr.policy || fail=$?;;
        4|5) tpm2_createpolicy -Q -g "$hash" --policy-pcr -l "$pcr_bank":"$pcr_ids" \
                               -f "$TMP"/pcr.digest -L "$TMP"/pcr.policy || fail=$?;;
        *) fail=1;;
    esac
    if [ -n "$fail" ]; then
        echo "create policy fail, please check the environment or parameters!"
        exit 1
    fi
    tpm2_flushcontext -t

    policy_options+=(-L "$TMP/pcr.policy")
else
    obj_attr="$obj_attr|userwithauth"
fi

case "$TPM2TOOLS_VERSION" in
    3) tpm2_create -Q -g "$hash" -G "$alg_create_key" -c "$TMP"/primary.context -u "$TMP"/jwk.pub \
                   -r "$TMP"/jwk.priv -A "$obj_attr" "${policy_options[@]}" -I- <<< "$jwk" || fail=$?;;
    4|5) tpm2_create -Q -g "$hash" -C "$TMP"/primary.context -u "$TMP"/jwk.pub \
                     -r "$TMP"/jwk.priv -a "$obj_attr" "${policy_options[@]}" -i- <<< "$jwk" || fail=$?;;
    *) fail=1;;
esac
if [ -n "$fail" ]; then
    echo "Creating TPM2 object for jwk failed!" >&2
    exit 1
fi
tpm2_flushcontext -t

if ! jwk_pub="$(jose b64 enc -I "$TMP"/jwk.pub)"; then
    echo "Encoding jwk.pub in Base64 failed!" >&2
    exit 1
fi

if ! jwk_priv="$(jose b64 enc -I "$TMP"/jwk.priv)"; then
    echo "Encoding jwk.priv in Base64 failed!" >&2
    exit 1
fi

jwe='{"protected":{"clevis":{"pin":"tpm2","tpm2":{}}}}'
jwe="$(jose fmt -j "$jwe" -g protected -g clevis -g tpm2 -q "$hash" -s hash -UUUUo-)"
jwe="$(jose fmt -j "$jwe" -g protected -g clevis -g tpm2 -q "$key" -s key -UUUUo-)"

if [ -n "$pcr_ids" ]; then
    jwe="$(jose fmt -j "$jwe" -g protected -g clevis -g tpm2 -q "$pcr_bank" -s pcr_bank -UUUUo-)"
    jwe="$(jose fmt -j "$jwe" -g protected -g clevis -g tpm2 -q "$pcr_ids" -s pcr_ids -UUUUo-)"
fi

jwe="$(jose fmt -j "$jwe" -g protected -g clevis -g tpm2 -q "$jwk_pub" -s jwk_pub -UUUUo-)"
jwe="$(jose fmt -j "$jwe" -g protected -g clevis -g tpm2 -q "$jwk_priv" -s jwk_priv -UUUUo-)"

# The on_exit() trap will not be fired after exec, so let's clean up the temp
# directory at this point.
[ -d "${TMP}" ] && rm -rf "${TMP}"

exec jose jwe enc -i- -k- -I- -c < <(echo -n "$jwe$jwk"; /bin/cat)