tpm2_pcrreset man page

tpm2_pcrreset(1) — Reset one or more PCR banks

Synopsis

tpm2_pcrreset [Options] PCR_INDEX ...

Description

tpm2_pcrreset(1) - Reset PCR value in all banks for specified index. More than one PCR index can be specified.

The reset value is manufacturer-dependent and is either sequence of 00 or FF on the length of the hash algorithm for each supported bank.

PCR_INDEX is a space separated list of PCR indexes to be reset when issuing the command.

Options

This tool accepts no tool specific options.

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

Reset a single PCR

tpm2_pcrreset 23

Reset multiple PCRs

tpm2_pcrreset 16 23

Notes

On operating system's locality (generally locality 0), only PCR 23 can be reset. PCR-16 can also be reset on this locality, depending on TPM manufacturers which could define this PCR as resettable.

PCR 0 to 15 are not resettable (being part of SRTM). PCR 16 to 22 are mostly reserved for DRTM or dedicated to specific localities and might not be resettable depending on current TPM locality.

Returns

Tools can return any of the following codes:

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