#!/bin/sh

# Exit immediately if a command exits with a non-zero status
set -e

# Summary of the script's functionality
summary="Encrypts using a TPM2.0 chip binding policy."

# TPM2.0 owner hierarchy to be used by the Operating System
auth="o"

# Attributes for the created TPM2 object with the JWK as sensitive data
obj_attr="fixedtpm|fixedparent|noda|adminwithpolicy"

# Display summary if requested
if [ "$1" = "--summary" ]; then
    echo "$summary"
    exit 0
fi

# Display usage information if input is from a terminal
if [ -t 0 ]; then
    exec >&2
    echo "$summary"
    echo
    echo "This command uses the following configuration properties:"
    echo "  hash: <string> -> Hash algorithm used in the computation of the object name (default: sha256)."
    echo "  key: <string> -> Algorithm type for the generated key (default: ecc)."
    echo "  pcr_bank: <string> -> PCR algorithm bank to use for policy (default: first supported by TPM)."
    echo "  pcr_ids: <string> -> PCR list used for policy. If not present, no policy is used."
    echo "  pcr_digest: <string> -> Binary PCR hashes encoded in base64. If not present, the hash values are looked up."
    echo
    echo "Usage: \"zlevis-encrypt '{\"property\":\"value\"}' < file.key > file.jwe\""
    echo "Usage ZFS: \"zfs set tpm:jwe=\$(zlevis-encrypt '{\"property\":\"value\"}' < tank.key) <pool>\""
    exit 2
fi

# Function to validate PCRs
validate_pcrs() {
    _tpm2_tools_v="${1}"
    _pcr_bank="${2}"
    _pcrs="${3}"

    # Return if PCR bank is not provided
    [ -z "${_pcr_bank}" ] && return 1
    [ -z "${_pcrs}" ] && return 0

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

    # Check for errors in PCR validation
    if [ -n "${_fail}" ] || [ -z "${_pcrs_r}" ]; then
        return 1
    fi
    return 0
}

# Function to clean up temporary files on exit
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
}

# Get the version of tpm2-tools
tpm2tools_version=$(tpm2_createprimary -v | awk -F'version="' '{print $2}' | awk -F'.' '{print $1}')

# Check if the tpm2-tools version is supported
if [ -z "$tpm2tools_version" ] || [ "$tpm2tools_version" -lt 4 ] || [ "$tpm2tools_version" -gt 5 ]; then
    echo "The tpm2 pin requires a tpm2-tools version between 4 and 5"
    exit 1
fi

# Create a temporary directory for TPM files
if ! tmp="$(mktemp -d)"; then
    echo "Creating a temporary dir for TPM files failed" >&2
    exit 1
fi

# Set up cleanup on exit
trap 'on_exit' EXIT

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

# Store the configuration in a temporary file
echo "$cfg" > "$tmp"/cfg

# Extract hash and key from the configuration, defaulting if not present
hash="$(jose fmt -j- -Og hash -u- < "$tmp"/cfg)" || hash="sha256"
key="$(jose fmt -j- -Og key -u- < "$tmp"/cfg)" || key="ecc"

# Determine the PCR bank to use for policy
pcr_bank="$(jose fmt -j- -Og pcr_bank -u- < "$tmp"/cfg)" || {
    # If not specified, find a non-empty PCR algorithm bank
    if ! pcr_bank=$(tpm2_getcap pcrs | awk '/^[[:space:]]*-[[:space:]]*([^:]+):[[:space:]]*\[[[:space:]]*[^][:space:]]/ {found=1; split($0, m, /[-:[:space:]]+/); print m[2]; exit} END {exit !found}'); then
        echo "Unable to find non-empty PCR algorithm bank, please check output of tpm2_getcap pcrs" >&2
        exit 1
    fi
}

# Trim spaces from the configuration for parsing PCR IDs
pcr_cfg=$(tr -d '[:space:]' < "$tmp"/cfg)
echo "$pcr_cfg" > "$tmp"/pcr_cfg

# Handle both string and JSON array formats for pcr_ids
if jose fmt -j- -Og pcr_ids 2>/dev/null < "$tmp"/pcr_cfg && ! pcr_ids="$(jose fmt -j- -Og pcr_ids -u- 2>/dev/null < "$tmp"/pcr_cfg)"; then
    # Attempt to parse as a JSON array if string parsing fails
    if jose fmt -j- -Og pcr_ids -A 2>/dev/null < "$tmp"/pcr_cfg; then
        # Construct a comma-separated string from the array
        for pcr in $(jose fmt -j- -Og pcr_ids -Af- < "$tmp"/pcr_cfg | tr -d '"'); do
            pcr_ids=$(printf '%s,%s' "${pcr_ids}" "${pcr}")
        done
        # Remove leading comma
         pcr_ids=${pcr_ids#,}
    else
        echo "Parsing the requested policy failed" >&2
        exit 1
    fi
fi

# Validate the combination of PCR bank and PCR IDs
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

# Get the PCR digest from the configuration or read it if not provided
pcr_digest="$(jose fmt -j- -Og pcr_digest -u- < "$tmp"/cfg)" || true
echo "$pcr_digest" > "$tmp"/pcr_digest

# Generate a JSON Web Key (JWK)
if ! jwk="$(jose jwk gen -i '{"alg":"A256GCM"}')"; then
    echo "Generating a jwk failed" >&2
    exit 1
fi
echo "$jwk" > "$tmp"/jwk

# Create the primary key in the TPM
case "$tpm2tools_version" in
    4|5) tpm2_createprimary -Q -C "$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

# Handle PCRs and policy creation if PCR IDs are provided
policy_options=""
if [ -n "$pcr_ids" ]; then
    if [ -z "$pcr_digest" ]; then
        case "$tpm2tools_version" in
            4|5) tpm2_pcrread -Q "$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 "$tmp"/pcr.digest < "$tmp"/pcr_digest; then
            echo "Error decoding PCR digest" >&2
            exit 1
        fi
    fi

    # Create the policy based on PCRs
    case "$tpm2tools_version" in
        4|5) tpm2_createpolicy -Q -g "$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
    tpm2_flushcontext -l

    # Set the policy options to the created policy file
    policy_options="$tmp/pcr.policy"
else
    # If no PCR IDs are provided, add user authentication to the object attributes
    obj_attr="$obj_attr|userwithauth"
fi

# Create the TPM2 object for the JWK
case "$tpm2tools_version" in
    4|5) tpm2_create -Q -g "$hash" -C "$tmp"/primary.context -u "$tmp"/jwk.pub -r "$tmp"/jwk.priv -a "$obj_attr" -L "$policy_options" -i- < "$tmp"/jwk || fail=$?;;
    *) fail=1;;
esac
if [ -n "$fail" ]; then
    echo "Creating TPM2 object for jwk failed" >&2
    exit 1
fi
tpm2_flushcontext -t

# Encode the JWK public and private keys in Base64
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

# Construct the JWE (JSON Web Encryption) structure
jwe='{"protected":{"zlevis":{"pin":"tpm2","tpm2":{}}}}'
jwe="$(jose fmt -j "$jwe" -g protected -g zlevis -g tpm2 -q "$hash" -s hash -UUUUo-)"
jwe="$(jose fmt -j "$jwe" -g protected -g zlevis -g tpm2 -q "$key" -s key -UUUUo-)"

# Include PCR bank and IDs in the JWE if they are provided
if [ -n "$pcr_ids" ]; then
    jwe="$(jose fmt -j "$jwe" -g protected -g zlevis -g tpm2 -q "$pcr_bank" -s pcr_bank -UUUUo-)"
    jwe="$(jose fmt -j "$jwe" -g protected -g zlevis -g tpm2 -q "$pcr_ids" -s pcr_ids -UUUUo-)"
fi

# Add the Base64 encoded JWK public and private keys to the JWE
jwe="$(jose fmt -j "$jwe" -g protected -g zlevis -g tpm2 -q "$jwk_pub" -s jwk_pub -UUUUo-)"
jwe="$(jose fmt -j "$jwe" -g protected -g zlevis -g tpm2 -q "$jwk_priv" -s jwk_priv -UUUUo-)"

# Output the final JWE
(echo "$jwe$jwk$(/bin/cat)") | jose jwe enc -i- -k- -I- -c

# Exit with the status of the last command
exit $?