tpm2_policycountertimer - Man Page

Enables policy authorization by evaluating the comparison operation on the TPM parameters time, clock, reset count, restart count and TPM clock safe flag.

Synopsis

tpm2_policycountertimer [Options] [ARGUMENT]

Description

tpm2_policycountertimer(1) - Enables policy authorization by evaluating the comparison operation on the TPM parameters time, clock, reset count, restart count and TPM clock safe flag. If time/clock, it is input as milliseconds value. The parameter and the value is given as a command line argument as below:

tpm2_policycountertimer -S session.ctx safe
tpm2_policycountertimer -S session.ctx clock=<N ms>
tpm2_policycountertimer -S session.ctx time=<N ms>
tpm2_policycountertimer -S session.ctx resets=<N>
tpm2_policycountertimer -S session.ctx restarts=<N>

By default comparison tests for equality and also by default it tests for time.

Options

if value of current time in the TPM != value of specified input time.

if signed value of current time in the TPM > signed value of specified input time.

if unsigned value of current time in the TPM > unsigned value of specified input time.

if signed value of current time in the TPM < signed value of specified input time.

if unsigned value of current time in the TPM < unsigned value of specified input time.

if signed value of current time in the TPM >= signed value of specified input time.

if unsigned value of current time in the TPM >= unsigned value of specified input time.

if signed value of current time in the TPM <= unsigned value of specified input time.

if unsigned value of current time in the TPM <= unsigned value of specified input time.

References

Common Options

This collection of options are common to many programs and provide information that many users may expect.

TCTI Configuration

The TCTI or "Transmission Interface" is the communication mechanism with the TPM. TCTIs can be changed for communication with TPMs across different mediums.

To control the TCTI, the tools respect:

  1. The command line option -T or --tcti
  2. The environment variable: TPM2TOOLS_TCTI.

Note: The command line option always overrides the environment variable.

The current known TCTIs are:

The arguments to either the command line option or the environment variable are in the form:

<tcti-name>:<tcti-option-config>

Specifying an empty string for either the <tcti-name> or <tcti-option-config> results in the default being used for that portion respectively.

TCTI Defaults

When a TCTI is not specified, the default TCTI is searched for using dlopen(3) semantics. The tools will search for tabrmd, device and mssim TCTIs IN THAT ORDER and USE THE FIRST ONE FOUND. You can query what TCTI will be chosen as the default by using the -v option to print the version information. The "default-tcti" key-value pair will indicate which of the aforementioned TCTIs is the default.

Custom TCTIs

Any TCTI that implements the dynamic TCTI interface can be loaded. The tools internally use dlopen(3), and the raw tcti-name value is used for the lookup. Thus, this could be a path to the shared library, or a library name as understood by dlopen(3) semantics.

Tcti Options

This collection of options are used to configure the various known TCTI modules available:

Examples

Create a sealing object with an authorization policy that evaluates only for first minute of TPM restart.

Create the policy and the sealing object

tpm2_startauthsession -S session.ctx

tpm2_policycountertimer -S session.ctx -L policy.countertimer --ult 60000

tpm2_flushcontext session.ctx

tpm2_createprimary -C o -c prim.ctx -Q

echo "SUPERSECRET" | \
tpm2_create -Q -u key.pub -r key.priv -i- -C prim.ctx \
-L policy.countertimer -a "fixedtpm|fixedparent" -c key.ctx

Unsealing should work in the first minute after TPM restart

tpm2_startauthsession -S session.ctx --policy-session

tpm2_policycountertimer -S session.ctx --ult 60000

tpm2_unseal -c key.ctx -p session:session.ctx

tpm2_flushcontext session.ctx

Returns

Tools can return any of the following codes:

Limitations

It expects a session to be already established via tpm2_startauthsession(1) and requires one of the following:

Without it, most resource managers will not save session state between command invocations.

Bugs

Github Issues (https://github.com/tpm2-software/tpm2-tools/issues)

Help

See the Mailing List (https://lists.01.org/mailman/listinfo/tpm2)

Info

tpm2-tools General Commands Manual