tpm2_policylocality - Man Page

tpm2_policylocality [Options] [ARGUMENT]

tpm2_policylocality(1) - Restricts TPM object authorization to specific TPM locality. Useful when you want to allow only specific locality with the TPM object. A locality indicates the source of the command, for example it could be from the application layer or the driver layer, each would have it’s own locality integer. Localities are hints to the TPM and are enforced by the software communicating to the TPM. Thus they are not trusted inputs on their own and are implemented in platform specific ways.

As an argument it takes the LOCALITY as an integer or friendly name.

Localities are fixed to a byte in size and have two representations, locality and extended locality.

Localities 0 through 4 are the normal locality representation and are represented as set bit indexes. Thus locality 0 is indicated by 1<<0 and locality 4 is indicated by 1<<4. Rather then using raw numbers, these localities can also be specified by the friendly names of: - zero: locality 0 or 1<<0 - one: locality 1 or 1<<1 - two: locality 2 or 1<<2 - three: locality 3 or 1<<3 - four: locality 4 or 1<<4

Anything from the range 32 - 255 are extended localities.

• -S, --session=FILE:

  A session file from tpm2_startauthsession(1)’s -S option.

• -L, --policy=FILE:

  File to save the policy digest.

• ARGUMENT the command line argument specifies the locality number.

• --cphash=FILE

  File path to record the hash of the command parameters. This is commonly termed as cpHash. NOTE: When this option is selected, The tool will not actually execute the command, it simply returns a cpHash.

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

• -h, --help=[man|no-man]: Display the tools manpage. By default, it attempts to invoke the manpager for the tool, however, on failure will output a short tool summary. This is the same behavior if the “man” option argument is specified, however if explicit “man” is requested, the tool will provide errors from man on stderr. If the “no-man” option if specified, or the manpager fails, the short options will be output to stdout.

  To successfully use the manpages feature requires the manpages to be installed or on MANPATH, See man(1) for more details.

• -v, --version: Display version information for this tool, supported tctis and exit.
• -V, --verbose: Increase the information that the tool prints to the console during its execution. When using this option the file and line number are printed.
• -Q, --quiet: Silence normal tool output to stdout.
• -Z, --enable-errata: Enable the application of errata fixups. Useful if an errata fixup needs to be applied to commands sent to the TPM. Defining the environment TPM2TOOLS_ENABLE_ERRATA is equivalent. information many users may expect.

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:

• tabrmd - The resource manager, called tabrmd (https://github.com/tpm2-software/tpm2-abrmd). Note that tabrmd and abrmd as a tcti name are synonymous.
• mssim - Typically used for communicating to the TPM software simulator.
• device - Used when talking directly to a TPM device file.
• none - Do not initalize a connection with the TPM. Some tools allow for off-tpm options and thus support not using a TCTI. Tools that do not support it will error when attempted to be used without a TCTI connection. Does not support ANY options and MUST BE presented as the exact text of “none”.

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.

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

• device: For the device TCTI, the TPM character device file for use by the device TCTI can be specified. The default is /dev/tpm0.

  Example: -T device:/dev/tpm0 or export TPM2TOOLS_TCTI=“device:/dev/tpm0”

• mssim: For the mssim TCTI, the domain name or IP address and port number used by the simulator can be specified. The default are 127.0.0.1 and 2321.

  Example: -T mssim:host=localhost,port=2321 or export TPM2TOOLS_TCTI=“mssim:host=localhost,port=2321”

• abrmd: For the abrmd TCTI, the configuration string format is a series of simple key value pairs separated by a `,' character. Each key and value string are separated by a `=' character.

  • TCTI abrmd supports two keys:

    1. `bus_name' : The name of the tabrmd service on the bus (a string).
    2. `bus_type' : The type of the dbus instance (a string) limited to `session' and `system'.

  Specify the tabrmd tcti name and a config string of bus_name=com.example.FooBar:

  \--tcti=tabrmd:bus_name=com.example.FooBar

  Specify the default (abrmd) tcti and a config string of bus_type=session:

  \--tcti:bus_type=session

  NOTE: abrmd and tabrmd are synonymous. the various known TCTI modules.

Start a policy session and extend it with a specific locality number (like 3). Attempts to perform other operations would fail.

tpm2_startauthsession -S session.dat

tpm2_policylocality -S session.dat -L policy.dat three

tpm2_flushcontext session.dat

tpm2_createprimary -C o -c prim.ctx

tpm2_create -C prim.ctx -u sealkey.pub -r sealkey.priv -L policy.dat \
-i- <<< "SEALED-SECRET"

tpm2_load -C prim.ctx -u sealkey.pub -r sealkey.priv -n sealkey.name \
-c sealkey.ctx

tpm2_startauthsession \--policy-session -S session.dat

tpm2_policylocality -S session.dat -L policy.dat three

# Change to locality 3, Note: this operation varies on different platforms

tpm2_unseal -p session:session.dat -c sealkey.ctx

tpm2_flushcontext session.dat

Tools can return any of the following codes:

• 0 - Success.
• 1 - General non-specific error.
• 2 - Options handling error.
• 3 - Authentication error.
• 4 - TCTI related error.
• 5 - Non supported scheme. Applicable to tpm2_testparams.

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

• direct device access
• extended session support with tpm2-abrmd.

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

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

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