mirror of
https://github.com/tpm2dev/tpm.dev.tutorials.git
synced 2024-11-23 06:12:10 +00:00
284 lines
8.4 KiB
Bash
Executable file
284 lines
8.4 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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cat <<EOF
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Usage: $PROG CIPHERTEXT OUT [POLICY-CMD [ARGS] [;] ...]
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Decrypts the {CIPHERTEXT} file produced by {send-to-tpm}.
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If {CIPHERTEXT}.tk.pem, {CIPHERTEXT}.tk.dpriv, {CIPHERTEXT}.tk.pub,
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and {CIPHERTEXT}.tk.seed exist, then the "TK" method of encryption is
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assumed. Otherwise the "EK" method of encryption is assumed.
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See {send-to-tpm} for details of the two encryption-to-TPM methods
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supported.
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The plaintext is written to the {OUT} file.
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If the sender asserted a policy, that policy must be given to {$PROG}
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so it can execute and satisfy it.
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Policies should be specified as a sequence of {tpm2 policy...}
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commands, with all necessary arguments except for {--session}|{-S}
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and {--policy}|{-L} options. Also, no need to include {tpm2
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policycommandcode}, as that will get added. E.g.:
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$ $PROG ./ekpub ./secret ./madecredential \\
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tpm2 policypcr -l "sha256:0,1,2,3" -f pcrs
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Options:
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-h This help message.
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-f Overwrite OUT-FILE.
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-x Trace this script.
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EOF
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exit 1
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}
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force=false
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while getopts +:hfx opt; do
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case "$opt" in
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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 $((OPTIND - 1))
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(($# >= 2)) || usage
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ciphertext_file=$1
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out_file=$2
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shift 2
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[[ ! -f ${ciphertext_file:-} ]] && die "No ciphertext file given"
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[[ -f ${out_file:-} ]] && $force && rm -f "$out_file"
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[[ ! -f ${out_file:-} ]] || die "Plaintext file exists; use -f?"
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d=
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trap 'rm -rf "$d"' EXIT
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d=$(mktemp -d)
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use_tk=true
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command_code=TPM2_CC_RSA_Decrypt
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for i in dpriv pub seed; do
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($use_tk && [[ -s ${ciphertext_file}.tk.$i ]]) || use_tk=false
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done
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$use_tk || command_code=TPM2_CC_ActivateCredential
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# Execute a policy given as arguments.
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#
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# The first argument may be a command code; if given, then {tpm2}
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# {policycommandcode} will be added to the given policy. The rest must be
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# {tpm2_policy*} or {tpm2} {policy*} commands w/o any {--session}|{-c} or
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# {--policy}|{-L} arguments, and multiple commands may be given separate by
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# {';'}.
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#
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# E.g.,
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#
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# exec_policy TPM2_CC_ActivateCredential "$@"
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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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# Get the EK handle
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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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tpm2 createek \
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--key-algorithm rsa \
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--ek-context "${d}/ek.ctx" \
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--public "${d}/ek.pub" \
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|| die "tpm2: unable to create ek object"
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# Make policyDigest
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(($# > 0)) && make_policyDigest "$command_code" "$@"
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# Create empty auth session for EK
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tpm2 flushcontext --transient-object
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tpm2 flushcontext --loaded-session
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tpm2 startauthsession --session "${d}/sessionek.ctx" --policy-session
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tpm2 policysecret --session "${d}/sessionek.ctx" --object-context endorsement
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# Execute and satisfy the policy for the TK or WK
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function auth {
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tpm2 flushcontext --transient-object
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tpm2 flushcontext --loaded-session
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tpm2 startauthsession \
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--session "${d}/session.ctx" \
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--policy-session
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# exec_policy will {die} if we fail to satisfy the policy
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exec_policy "$command_code" "$@"
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tpm2 flushcontext --transient-object
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tpm2 flushcontext --loaded-session
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}
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if $use_tk; then
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# attempt to load the secret wrapping key into our TPM
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# as a transient object
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tpm2 flushcontext --transient-object
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tpm2 flushcontext --loaded-session
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info "tpm2: Importing duplicate transport key"
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tpm2 import \
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--parent-context "${d}/ek.ctx" \
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--parent-auth "session:${d}/sessionek.ctx" \
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--key-algorithm rsa \
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--input "${ciphertext_file}.tk.dpriv" \
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--seed "${ciphertext_file}.tk.seed" \
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--public "${ciphertext_file}.tk.pub" \
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--private "${d}/tk.priv" \
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|| die "tpm2: unable to import duplicate transport key object"
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warn "tpm2: Loading duplicate transport key"
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tpm2 flushcontext --transient-object
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tpm2 flushcontext --loaded-session
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tpm2 startauthsession --session "${d}/sessionek.ctx" --policy-session
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tpm2 policysecret --session "${d}/sessionek.ctx" --object-context endorsement
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tpm2 load \
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--parent-context "${d}/ek.ctx" \
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--auth "session:${d}/sessionek.ctx" \
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--key-context "${d}/tk.ctx" \
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--public "${ciphertext_file}.tk.pub" \
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--private "${d}/tk.priv" \
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|| die "tpm2: unable to load duplicate transport key object"
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warn "tpm2: Decrypting with TK"
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if (($# > 0)); then
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auth "$@"
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tpm2 rsadecrypt \
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--auth "session:${d}/session.ctx" \
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--key-context "${d}/tk.ctx" \
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--output "${out_file}" \
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"${ciphertext_file}" \
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|| die "tpm2: unable to decrypt with transport key"
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else
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tpm2 rsadecrypt \
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--key-context "${d}/tk.ctx" \
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--output "${out_file}" \
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"${ciphertext_file}" \
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|| die "tpm2: unable to decrypt with transport key"
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fi
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else
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# Load the WK for use as the activation object for
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# TPM2_ActivateCredential():
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tpm2 flushcontext --transient-object 1>&2
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tpm2 flushcontext --loaded-session 1>&2
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wkpriv > "${d}/wkpriv.pem"
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attrs='sign'
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adminwithpolicy=
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if (($# > 0)); then
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attrs='adminwithpolicy|sign'
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adminwithpolicy=true
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fi
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if tpm2 loadexternal \
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--hierarchy n \
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--key-algorithm ecc \
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--private "${d}/wkpriv.pem" \
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${adminwithpolicy:+--policy "${d}/policy"} \
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--attributes "$attrs" \
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--key-context "${d}/wk.ctx" 1>&2; then
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true
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else
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stat=$?
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echo "ERROR: Failed to load WK: $?" 1>&2
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exit $stat
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fi
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# If a policy was given to execute, create a policy session and execute
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# and satisfy the policy:
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activatecredential_args=()
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if (($# > 0)); then
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activatecredential_args+=(--credentialedkey-auth session:"${d}/session.ctx")
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auth "$@"
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fi
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# Finally, ActivateCredential
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tpm2 activatecredential \
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--credentialedkey-context "${d}/wk.ctx" \
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"${activatecredential_args[@]}" \
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--credentialkey-context "${d}/ek.ctx" \
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--credentialkey-auth session:"${d}/sessionek.ctx" \
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--credential-blob "$ciphertext_file" \
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--certinfo-data "$out_file" > /dev/null \
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|| die "could not decrypt using TPM2_ActivateCredential()"
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fi
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