% tpm2_policyrestart(1) tpm2-tools | General Commands Manual

NAME

tpm2_policyrestart(1) - Restart an existing session with the TPM.

SYNOPSIS

tpm2_policyrestart [OPTIONS]

DESCRIPTION

tpm2_policyrestart(1) - Restarts a session with the TPM back to it's initial state. This is useful when the TPM gives one a TPM_RC_PCR_CHANGED (0x00000128) error code when using a PCR policy session.

This will be returned if a PCR state affecting policy is altered during the session. One could restart the session and try again, however, the PCR state would still need to satisfy the policy.

OPTIONS

  • -S, --session=FILE:

    Optional, A session file from tpm2_startauthsession(1)'s -S option. This session is used in lieu of starting a session and using the PCR policy options.

References

common options collection of common options that provide information many users may expect.

common tcti options collection of options used to configure the various known TCTI modules.

EXAMPLES

Start a policy session and restart it, unsealing some data.

# create a policy and bind it to an object
tpm2_startauthsession -S session.dat

tpm2_policypcr -S session.dat -l "sha1:0,1,2,3" -L policy.dat

tpm2_createprimary -c primary.ctx

tpm2_create -Cprimary.ctx -u key.pub -r key.priv -L policy.dat -i- <<< "secret"

tpm2_load -C primary.ctx -c key.ctx -u key.pub -r key.priv

tpm2_flushcontext session.dat

# satisfy the policy and use the object
tpm2_startauthsession --policy -S session.dat

tpm2_policypcr -S session.dat -l "sha1:0,1,2,3"

# PCR event occurs here causing unseal to fail
tpm2_pcrevent 0 <<< "event data"

tpm2_unseal -psession:session.dat -c key.ct
ERROR: Esys_Unseal(0x128) - tpm:error(2.0): PCR have changed since checked

# Clear the policy digest to initial state, note access to object no longer allowed by
# policy so policyor would be useful here.
tpm2_policyrestart -S session.dat

returns

limitations

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