mirror of
https://github.com/tpm2dev/tpm.dev.tutorials.git
synced 2024-12-22 09:42:11 +00:00
331 lines
9.4 KiB
Bash
Executable file
331 lines
9.4 KiB
Bash
Executable file
#!/bin/bash
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PROG=${0##*/}
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set -euo pipefail
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shopt -s extglob
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die() { echo "${PROG:+${PROG}: }$die_msg""$*" >&2 ; exit 1 ; }
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info() { ((${VERBOSE:-0})) && echo "$@" >&2 ; return 0 ; }
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function usage {
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((${1:-1} > 0)) && exec 1>&2
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pager=cat
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if [[ -t 0 && -t 1 && -t 2 ]]; then
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if [[ -z ${PAGER:-} ]] && type less >/dev/null 2>&1; then
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pager=less
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elif [[ -z ${PAGER:-} ]] && type more >/dev/null 2>&1; then
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pager=more
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elif [[ -n ${PAGER:-} ]]; then
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pager=$PAGER
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fi
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fi
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$pager <<EOF
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Usage: $PROG EK-PUB SECRET OUT # Null policy
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$PROG EK-PUB SECRET OUT POLICY-CMD [ARGS [\\; ...]]
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$PROG -P POLICY EK-PUB SECRET OUT
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{$PROG} encrypts a small (up to 32 bytes) {SECRET} file (should
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contain an AES key) to a target TPM -identified by {EK-PUB}- with the
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caller's optional choice of policy to be enforced by that TPM. The
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{EK-PUB} should be a file containing the target's EKpub in
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{TPM2B_PUBLIC} format.
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Options:
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-h This help message.
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-M EK|TK Method to use for encryption to TPM (default: EK).
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-P POLICY Use the named policy or policyDigest.
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-f Overwrite {OUT}.
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-x Trace this script.
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Policies given as positional arguments should be of the form:
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tpm2 policy... args... \\; tpm2 policy args... \\; ...
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without any {--session}|{-S} nor {--policy}|{-L} options.
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Also, no need to include {tpm2 policycommandcode}, as {$PROG} will add
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that automatically.
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E.g.:
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$ $PROG ./ekpub ./secret ./madecredential \\
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tpm2 policypcr -l "sha256:0,1,2,3" -f pcrs
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A POLICY can be a digest or an executable.
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A POLICY digest would be the SHA-256 policyDigest of a policy.
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A POLICY executable would be a program that, if called with no
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arguments, outputs a policyDigest.
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The two methods of encryption to a TPM are:
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- EK Uses {TPM2_MakeCredential()} to encrypt an AES key to
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the target's EKpub.
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The target uses {TPM2_ActivateCredential()} to decrypt
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the AES key.
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A well-known key is used as the activation object, and
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the given policy is associated with it.
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This method produces a single file named {OUT}.
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- TK Uses {TPM2_Duplicate()} to encrypt an RSA private key to
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the target's EKpub, then encrypts an AES key to that
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key's public key. That RSA key we refer to as a
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"transport key", or TK.
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The target uses {TPM2_Import()} to import the TK,
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{TPM2_Load()} to load it, and {TPM2_RSA_Decrypt()} to
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decrypt the AES key.
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A policy, if given, is set on the TK that the TPM will
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enforce when {TPM2_RSA_Decrypt()} is called.
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This method produces multiple files besides {OUT},
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named:
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{OUT}.tk.dpriv
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{OUT}.tk.seed
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EOF
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exit "${1:-1}"
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}
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force=false
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method=EK
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policy=
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policyDigest=
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while getopts +:hfxM:P: opt; do
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case "$opt" in
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M) method=$OPTARG;;
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P) policy=$OPTARG;;
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h) usage 0;;
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f) force=true;;
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x) set -vx;;
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*) usage;;
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esac
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done
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shift $((OPTIND - 1))
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function err {
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echo "ERROR: $*" 1>&2
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exit 1
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}
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case "$method" in
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EK) command_code=TPM2_CC_ActivateCredential;;
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TK) command_code=TPM2_CC_RSA_Decrypt;;
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*) err "METHOD must be \"EK\" or \"TK\"";;
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esac
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if [[ -n $policy ]] && (($# > 3)); then
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echo "Error: -P and policy commands are mutually exclusive" 1>&2
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exit 1
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fi
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if [[ -n $policy ]]; then
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(($# == 3)) || usage
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if ((${#policy} == 64)) &&
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[[ ! -f $policy && $policy = +([0-9a-fA-F]) ]]; then
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# $policy is a policyDigest
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policyDigest=$policy
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elif [[ -x $policy ]]; then
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# Run the script in $policy to get a policyDigest
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policyDigest=$("$policy")
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else
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err "Given policy is neither a SHA-256 policyDigest nor a policy script"
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fi
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fi
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(($# >= 3)) || usage
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ekpub_file=$1
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secret_file=$2
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out_file=$3
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shift 3
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[[ -f ${ekpub_file:-} ]] || usage
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[[ -f ${secret_file:-} ]] || usage
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[[ -f ${out_file:-} ]] && $force && rm -f "${out_file:-}"
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[[ -f ${out_file:-} ]] && err "output file ($out_file) exists"
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# Make a temp dir and remove it when we exit:
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d=
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trap 'rm -rf "$d"' EXIT
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d=$(mktemp -d)
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# Execute a policy given as arguments.
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#
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# The first argument may be a command code; if given, then {tpm2}
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# {policycommandcode} will be added to the given policy. The rest must be
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# {tpm2_policy*} or {tpm2} {policy*} commands w/o any {--session}|{-c} or
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# {--policy}|{-L} arguments, and multiple commands may be given separate by
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# {';'}.
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#
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# E.g.,
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#
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# exec_policy TPM2_CC_ActivateCredential "$@"
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# exec_policy tpm2 policypcr ... ';' tpm2 policysigned ...
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function exec_policy {
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local command_code=''
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local add_commandcode=true
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local has_policy=false
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local -a cmd
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if (($# > 0)) && [[ -z $1 || $1 = TPM2_CC_* ]]; then
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command_code=$1
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shift
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fi
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while (($# > 0)); do
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has_policy=true
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cmd=()
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while (($# > 0)) && [[ $1 != ';' ]]; do
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cmd+=("$1")
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if ((${#cmd[@]} == 1)) && [[ ${cmd[0]} = tpm2_* ]]; then
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cmd+=( --session "${d}/session.ctx"
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--policy "${d}/policy")
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elif ((${#cmd[@]} == 2)) && [[ ${cmd[0]} = tpm2 ]]; then
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cmd+=( --session "${d}/session.ctx"
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--policy "${d}/policy")
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fi
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shift
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done
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(($# > 0)) && shift
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# Run the policy command in the temp dir. It -or the last command- must
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# leave a file there named 'policy'.
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"${cmd[@]}" 1>&2 \
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|| die "unable to execute policy command: ${cmd[*]}"
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[[ ${cmd[0]} = tpm2 ]] && ((${#cmd[@]} == 1)) \
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&& die "Policy is incomplete"
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[[ ${cmd[0]} = tpm2 && ${cmd[1]} = policycommandcode ]] \
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&& add_commandcode=false
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[[ ${cmd[0]} = tpm2_policycommandcode ]] \
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&& add_commandcode=false
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done
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if $has_policy && $add_commandcode && [[ -n $command_code ]]; then
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tpm2 policycommandcode \
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--session "${d}/session.ctx" \
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--policy "${d}/policy" \
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"$command_code" 1>&2 \
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|| die "unable to execute policy command: tpm2 policycommandcode $command_code"
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fi
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xxd -p -c 100 "${d}/policy"
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}
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# Compute the policyDigest of a given policy by executing it in a trial
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# session.
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function make_policyDigest {
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tpm2 flushcontext --transient-object
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tpm2 flushcontext --loaded-session
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tpm2 startauthsession --session "${d}/session.ctx"
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exec_policy "$@"
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}
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# A well-known private key just for the TPM2_MakeCredential()-based encryption
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# of secrets to TPMs. It was generated with:
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# openssl genpkey -genparam \
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# -algorithm EC \
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# -out "${d}/ecp.pem" \
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# -pkeyopt ec_paramgen_curve:secp384r1 \
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# -pkeyopt ec_param_enc:named_curve
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# openssl genpkey -paramfile "${d}/ecp.pem"
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function wkpriv {
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cat <<"EOF"
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-----BEGIN PRIVATE KEY-----
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MIG2AgEAMBAGByqGSM49AgEGBSuBBAAiBIGeMIGbAgEBBDAlMnCWue7CfXjNLibH
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PTJrsOLUcoxqU3FLWYEWMI+HuPnzcwwl7SkKN6cpf4H3oQihZANiAAQ1pw6D5QVw
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vymljYVDyrUriOet8zPB/9tq9XJ7A54qsVkaVufAuEJ6GIvD4xUZ27manMosJADS
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aW2TLJkwxecRh2eTwPtSx2U32M2/yHeuWRV/0juiIozefPsTAlHAi3E=
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-----END PRIVATE KEY-----
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EOF
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}
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# Compute a well-known activation object's name for use in
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# TPM2_MakeCredential(), binding a given policy into it.
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#
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# This version uses a TPM via {tpm2 loadexternal}.
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function wkname_tpm {
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local attrs='sign'
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local has_policy=
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wkpriv > "${d}/wkpriv.pem"
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tpm2 flushcontext --transient-object
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tpm2 flushcontext --loaded-session
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tpm2 flushcontext --saved-session 1>&2
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# Load
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if [[ -n $policyDigest ]]; then
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tpm2 startauthsession --session "${d}/session.ctx"
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printf '%s' "$policyDigest" | xxd -p -r > "${d}/policy"
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echo "policyDigest: $(xxd -p -c 100 < "${d}/policy")" 1>&2
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attrs='adminwithpolicy|sign'
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has_policy=true
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elif (($# > 0)); then
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make_policyDigest "$command_code" "$@" 1>&2
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attrs='adminwithpolicy|sign'
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has_policy=true
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# Flush again, but this time not saved sessions
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tpm2 flushcontext --transient-object 1>&2
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tpm2 flushcontext --loaded-session 1>&2
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echo "policyDigest: $(xxd -p -c 100 < "${d}/policy")" 1>&2
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fi
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# Load the WK
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tpm2 loadexternal \
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--hierarchy n \
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--key-algorithm ecc \
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--private "${d}/wkpriv.pem" \
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${has_policy:+ --policy "${d}/policy"} \
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--attributes "$attrs" \
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--key-context "${d}/wk.ctx" \
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| grep ^name: | cut -d' ' -f2 \
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|| die "unable to load the WK into a TPM for computing its name"
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}
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case "$method" in
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EK) info "Computing WKname"
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wkname=$(wkname_tpm "$@") \
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|| die "unable to compute the MakeCredential activation object's cryptographic name"
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info "Encrypting to EKpub using TPM2_MakeCredential"
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tpm2 makecredential \
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--tcti "none" \
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--encryption-key "${ekpub_file}" \
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--name "$wkname" \
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--secret "${secret_file}" \
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--credential-blob "$out_file" \
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|| die "unable to MakeCredential";;
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TK) info "Generating TK"
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openssl genrsa -out "${d}/tk-priv.pem" \
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|| die "unable to create TK private key"
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openssl rsa \
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-pubout \
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-in "${d}/tk-priv.pem" \
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-out "${d}/tk.pem" \
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|| die "unable to create TK public key"
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args=()
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if (($# > 0)); then
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make_policyDigest "$command_code" "$@" 1>&2
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args=("--policy=${d}/policy")
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fi
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info "Exporting TK to EKpub"
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tpm2 duplicate \
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--tcti none \
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--parent-public="$ekpub_file" \
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--wrapper-algorithm=rsa \
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"${args[@]}" \
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--private-key="${d}/tk-priv.pem" \
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--public="${out_file}.tk.pub" \
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--private="${out_file}.tk.dpriv" \
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--encrypted-seed="${out_file}.tk.seed" \
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|| die "$0: unable to duplicate TK into TPM for EK"
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info "Encrypting to TK"
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openssl rsautl \
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-encrypt \
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-pubin \
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-inkey "${d}/tk.pem" \
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-in "$secret_file" \
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-out "${out_file}" \
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|| die "$0: unable to encrypt to TK" ;;
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esac
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