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tpmr: Fix sealing/unsealing file with both PCRs and passwords
When sealing/unsealing with a password, use a policy including both the specified PCRs and the object password. Fixes sealing and unsealing disk unlock key. tpm2 seems to have a bug in parameter decryption when using a policy session and password in this way, disable encryption in the policy session as a workaround. Flags still need to be set on the sealed object correctly, as the password is normally allowed on its own as an alternative to policy auth. Add -Q to some tpm2 invocations to silence diagnostics on stdout. Pass filename for unsealed secret rather than capturing from stdout for robustness against tpm2 diagnostics on stdout. Fix unseal result check in kexec-unseal-key. Signed-off-by: Jonathon Hall <jonathon.hall@puri.sm>
This commit is contained in:
Jonathon Hall
parent
1e5544b934
commit
e6acaad215
@ -44,9 +44,8 @@ for tries in 1 2 3; do
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unseal_result=1
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if [ "$CONFIG_TPM2_TOOLS" = "y" ]; then
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DEBUG "tpmr unseal "0x8100000$TPM_INDEX" "sha256:0,1,2,3,4,5,6,7" "$tpm_password" > "$key_file""
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tpmr unseal "0x8100000$TPM_INDEX" "sha256:0,1,2,3,4,5,6,7" "$tpm_password" > "$key_file" \
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|| unseal_result="$?"
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tpmr unseal "0x8100000$TPM_INDEX" "sha256:0,1,2,3,4,5,6,7" "$key_file" "$tpm_password"
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unseal_result="$?"
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else
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tpm unsealfile \
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-if "$sealed_file" \
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@ -40,7 +40,7 @@ if [ "$CONFIG_TPM" = "y" ] && [ "$CONFIG_TPM2_TOOLS" != "y" ]; then
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-of "$HOTP_SECRET" \
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|| die "Unable to unseal HOTP secret"
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elif [ "$CONFIG_TPM2_TOOLS" = "y" ]; then
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tpmr unseal 0x81004d47 sha256:0,1,2,3,4,7 > "$HOTP_SECRET" \
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tpmr unseal 0x81004d47 sha256:0,1,2,3,4,7 "$HOTP_SECRET" \
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|| die "Unable to unseal HOTP secret"
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fi
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129
initrd/bin/tpmr
129
initrd/bin/tpmr
@ -115,26 +115,45 @@ tpm2_counter_cre() {
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tpm2_startsession() {
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TRACE "Under /bin/tpmr:tpm2_startsession"
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mkdir -p "$SECRET_DIR"
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tpm2 flushcontext \
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tpm2 flushcontext -Q \
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--transient-object \
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|| die "tpm2_flushcontext: unable to flush transient handles"
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tpm2 flushcontext \
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tpm2 flushcontext -Q \
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--loaded-session \
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|| die "tpm2_flushcontext: unable to flush sessions"
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tpm2 flushcontext \
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tpm2 flushcontext -Q \
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--saved-session \
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|| die "tpm2_flushcontext: unable to flush saved session"
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tpm2 readpublic -c "$PRIMARY_HANDLE" -t "/tmp/$PRIMARY_HANDLE_FILE"
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tpm2 startauthsession -c "/tmp/$PRIMARY_HANDLE_FILE" --hmac-session -S "/tmp/$ENC_SESSION_FILE"
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tpm2 startauthsession -c "/tmp/$PRIMARY_HANDLE_FILE" --hmac-session -S "/tmp/$DEC_SESSION_FILE"
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tpm2 sessionconfig --disable-encrypt "/tmp/$DEC_SESSION_FILE"
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tpm2 readpublic -Q -c "$PRIMARY_HANDLE" -t "/tmp/$PRIMARY_HANDLE_FILE"
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tpm2 startauthsession -Q -c "/tmp/$PRIMARY_HANDLE_FILE" --hmac-session -S "/tmp/$ENC_SESSION_FILE"
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tpm2 startauthsession -Q -c "/tmp/$PRIMARY_HANDLE_FILE" --hmac-session -S "/tmp/$DEC_SESSION_FILE"
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tpm2 sessionconfig -Q --disable-encrypt "/tmp/$DEC_SESSION_FILE"
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}
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# Trap EXIT with cleanup_session() to release a TPM2 session and delete the
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# session file. E.g.:
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# trap "cleanup_session '$SESSION_FILE'" EXIT
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cleanup_session() {
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session_file="$1"
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if [ -f "$session_file" ]; then
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DEBUG "Clean up session: $session_file"
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# Nothing else we can do if this fails, still remove the file
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tpm2 flushcontext -Q "$session_file" || DEBUG "Flush failed for session $session_file"
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rm -f "$session_file"
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else
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DEBUG "No need to clean up session: $session_file"
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fi
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}
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# tpm2_sealfile: Seal a file against PCR values and, optionally, a password.
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# If a password is given, both the PCRs and password are required to unseal the
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# file. PCRs are provided as a PCR list and data file. PCR data must be
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# provided - TPM2 allows the TPM to fall back to current PCR values, but it is
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# not required to support this.
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tpm2_sealfile() {
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TRACE "Under /bin/tpmr:tpm2_sealfile"
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#TODO remove this: tpmr seal "$KEY_FILE" "0x8100000$TPM_INDEX" sha256:0,1,2,3,4,5,6,7 "$pcrf" "$key_password"
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file="$1" #$KEY_FILE
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handle="$2" # 0x8100000$TPM_INDEX
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pcrl="$3" #sha256:0,1,2,3,4,5,6,7
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@ -142,32 +161,90 @@ tpm2_sealfile() {
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pass="$5"
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mkdir -p "$SECRET_DIR"
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bname="`basename $file`"
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DEBUG "tpm2 createpolicy --policy-pcr -l "$pcrl" -f "$pcrf" -L "$SECRET_DIR/pcr.policy""
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tpm2 createpolicy --policy-pcr -l "$pcrl" -f "$pcrf" -L "$SECRET_DIR/pcr.policy"
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if [ "$pass" ];then
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echo -n "$pass" | tpm2 create -C "/tmp/$PRIMARY_HANDLE_FILE" -i "$file" -u "$SECRET_DIR/$bname.priv" -r "$SECRET_DIR/$bname.pub" -L "$SECRET_DIR/pcr.policy" -S "/tmp/$DEC_SESSION_FILE" -p "file:-"
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else
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tpm2 create -C "/tmp/$PRIMARY_HANDLE_FILE" -i "$file" -u "$SECRET_DIR/$bname.priv" -r "$SECRET_DIR/$bname.pub" -L "$SECRET_DIR/pcr.policy" -S "/tmp/$DEC_SESSION_FILE"
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# Create a policy requiring both PCRs and the object's authentication
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# value using a trial session.
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TRIAL_SESSION=/tmp/sealfile_trial.session
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AUTH_POLICY=/tmp/sealfile_auth.policy
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rm -f "$TRIAL_SESSION" "$AUTH_POLICY"
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tpm2 startauthsession -g sha256 -S "$TRIAL_SESSION"
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# We have to clean up the session
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trap "cleanup_session '$TRIAL_SESSION'" EXIT
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# Save the policy hash in case the password policy is not used (we have
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# to get this from the last step, whichever it is).
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tpm2 policypcr -Q -l "$pcrl" -f "$pcrf" -S "$TRIAL_SESSION" -L "$AUTH_POLICY"
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CREATE_PASS_ARGS=()
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if [ "$pass" ]; then
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# Add an object authorization policy (the object authorization
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# will be the password). Save the digest, this is the resulting
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# policy.
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tpm2 policypassword -Q -S "$TRIAL_SESSION" -L "$AUTH_POLICY"
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# Pass the password to create later
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# TODO: Providing the raw password to the TPM limits it to the
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# size of the largest supported hash (at least 32 chars, sha256)
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CREATE_PASS_ARGS=(-p "hex:$(echo -n "$pass" | xxd -p | tr -d '\n ')")
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fi
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tpm2 load -C "/tmp/$PRIMARY_HANDLE_FILE" -u "$SECRET_DIR/$bname.priv" -r "$SECRET_DIR/$bname.pub" -c "$SECRET_DIR/$bname.seal.ctx"
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# Create the object with this policy and the auth value.
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# NOTE: We disable USERWITHAUTH and enable ADMINWITHPOLICY so the
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# password cannot be used on its own, the PCRs are also required.
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# (The default is to allow either policy auth _or_ password auth. In
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# this case the policy includes the password, and we don't want to allow
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# the password on its own.)
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# TODO: Check the other default attributes, do we want them?
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# TODO: Providing the password directly limits it to the size of the
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# largest hash supported by the TPM (at least 32 chars for sha256)
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# TODO: The attributes aren't working yet, rejected with 'inconsistent attributes'
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# -a 'sign|decrypt|fixedtpm|fixedparent|sensitivedataorigin|adminwithpolicy'
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tpm2 create -Q -C "/tmp/$PRIMARY_HANDLE_FILE" \
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-i "$file" \
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-u "$SECRET_DIR/$bname.priv" \
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-r "$SECRET_DIR/$bname.pub" \
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-L "$AUTH_POLICY" \
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-S "/tmp/$DEC_SESSION_FILE" \
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"${CREATE_PASS_ARGS[@]}"
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tpm2 load -Q -C "/tmp/$PRIMARY_HANDLE_FILE" -u "$SECRET_DIR/$bname.priv" -r "$SECRET_DIR/$bname.pub" -c "$SECRET_DIR/$bname.seal.ctx"
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read -s -p "TPM owner password: " key_password
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echo # new line after password prompt
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# remove possible data occupying this handle
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tpm2 evictcontrol -C o -P "$key_password" -c "$handle" 2>/dev/null || true
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tpm2 evictcontrol -C o -P "$key_password" -c "$SECRET_DIR/$bname.seal.ctx" "$handle"
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tpm2 evictcontrol -Q -C o -P "$key_password" -c "$handle" 2>/dev/null || true
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tpm2 evictcontrol -Q -C o -P "$key_password" -c "$SECRET_DIR/$bname.seal.ctx" "$handle"
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}
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tpm2_unseal() {
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# Unseal a file sealed by tpm2_sealfile. The PCR list must be provided, the
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# password must be provided if one was used to seal (and cannot be provided if
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# no password was used to seal).
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tpm2_unsealfile() {
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TRACE "Under /bin/tpmr:tpm2_unseal"
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#TODO: remove this: tpmr unseal "0x8100000$TPM_INDEX" "sha256:0,1,2,3,4,5,6,7" "file:-" > "$key_file"
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handle="$1"
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pcrl="$2"
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pass="$3"
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DEBUG "handle: $handle prcl: $pcrl pass: $pass"
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if [ "$pass" ];then
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echo -n "$pass" | tpm2 unseal -c "$handle" -S "/tmp/$ENC_SESSION_FILE" -p "pcr:$pcrl+file:-"
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else
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tpm2 unseal -c "$handle" -S "/tmp/$ENC_SESSION_FILE" -p "pcr:$pcrl"
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file="$3"
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pass="$4"
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POLICY_SESSION=/tmp/unsealfile_policy.session
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rm -f "$POLICY_SESSION"
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tpm2 startauthsession -Q -g sha256 -c "/tmp/$PRIMARY_HANDLE_FILE" -S "$POLICY_SESSION" --policy-session
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trap "cleanup_session '$POLICY_SESSION'" EXIT
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# Check the PCR policy
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tpm2 policypcr -Q -l "$pcrl" -S "$POLICY_SESSION"
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UNSEAL_PASS_SUFFIX=""
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if [ "$pass" ]; then
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# Add the object authorization policy (the actual password is
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# provided later, but we must include this so the policy we
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# attempt to use is correct).
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tpm2 policypassword -Q -S "$POLICY_SESSION"
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# When unsealing, include the password with the auth session
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UNSEAL_PASS_SUFFIX="+hex:$(echo -n "$pass" | xxd -p | tr -d '\n ')"
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# Disable encryption in the policy session - there seems to be a
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# bug in tpm2's decryption. If we leave encryption enabled, the
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# unseal succeeds but we receive garbage, probably because it
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# was decrypted incorrectly. However, this causes the unsealed
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# data to be sent in the clear from the TPM.
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tpm2 sessionconfig -Q --disable-encrypt "$POLICY_SESSION"
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fi
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tpm2 unseal -Q -c "$handle" -p "session:$POLICY_SESSION$UNSEAL_PASS_SUFFIX" > "$file"
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}
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tpm2_reset() {
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@ -203,7 +280,7 @@ case "$subcmd" in
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startsession)
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tpm2_startsession "$@";;
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unseal)
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tpm2_unseal "$@";;
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tpm2_unsealfile "$@";;
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reset)
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tpm2_reset "$@";;
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*)
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@ -39,7 +39,7 @@ fi
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#counter_value=$(printf "%d" 0x${counter_value})
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if [ "$CONFIG_TPM2_TOOLS" = "y" ]; then
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tpmr unseal 0x81004d47 sha256:0,1,2,3,4,7 >> "$HOTP_SECRET"
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tpmr unseal 0x81004d47 sha256:0,1,2,3,4,7 "$HOTP_SECRET"
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elif [ "$CONFIG_TPM" = "y" ]; then
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tpm nv_readvalue \
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-in 4d47 \
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@ -9,7 +9,7 @@ TOTP_SECRET="/tmp/secret/totp.key"
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TRACE "Under /bin/unseal-totp"
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if [ "$CONFIG_TPM2_TOOLS" = "y" ]; then
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tpmr unseal 0x81004d47 sha256:0,1,2,3,4,7 > "$TOTP_SECRET" \
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tpmr unseal 0x81004d47 sha256:0,1,2,3,4,7 "$TOTP_SECRET" \
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|| die "Unable to unseal totp secret"
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elif [ "$CONFIG_TPM" = "y" ]; then
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tpm nv_readvalue \
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