tpm2_policynamehash(1)

NAME

tpm2_policynamehash(1) - Couples a policy with names of specific objects.

SYNOPSIS

tpm2_policynamehash [OPTIONS]

DESCRIPTION

tpm2_policynamehash(1) - Couples a policy with names of specific objects. This is a deferred assertion where the hash of the names of all object handles in a TPM command is checked against the one specified in the policy.

OPTIONS

•   -L, --policy=FILE:

    File to save the compounded policy digest.

•   -S, --session=FILE:

    The policy session file generated via the -S option to tpm2_startauthsession(1).

•   -n, --name=FILE:

    The file containing the name hash of the referenced objects.

  References

COMMON OPTIONS

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.

•   -R, --autoflush: Enable autoflush for transient objects created by the command. If a parent object is loaded from a context file also the transient parent object will be flushed. Autoflush can also be activated if the environment variable TPM2TOOLS_AUTOFLUSH is is set to yes or true. information 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:

•   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.

  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:

•   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.

EXAMPLES

Restrict key duplication to specific new parent and specific duplicable key.

Generate a duplicable object

    openssl genrsa -out signing_key_private.pem 2048
    openssl rsa -in signing_key_private.pem -out signing_key_public.pem -pubout
    tpm2_loadexternal -G rsa -C o -u signing_key_public.pem -c signing_key.ctx \
    -n signing_key.name
    tpm2_startauthsession -S session.ctx -g sha256
    tpm2_policyauthorize -S session.ctx -L authorized.policy -n signing_key.name
    tpm2_policycommandcode -S session.ctx -L policy.dat TPM2_CC_Duplicate
    tpm2_flushcontext session.ctx
    tpm2_createprimary -C o -g sha256 -G rsa -c primary.ctx -Q
    ## The duplicable key
    tpm2_create -Q -C primary.ctx -g sha256 -G rsa -r key.prv -u key.pub \
    -L policy.dat -a "sensitivedataorigin|sign|decrypt"
    tpm2_load -Q -C primary.ctx -r key.prv -u key.pub -c key.ctx

Create the new parent

    tpm2_create -Q -C primary.ctx -g sha256 -G rsa -r new_parent.prv \
    -u new_parent.pub \
    -a "decrypt|fixedparent|fixedtpm|restricted|sensitivedataorigin"
    tpm2_loadexternal -Q -C o -u new_parent.pub -c new_parent.ctx

Modify the duplicable key policy to namehash policy to restrict parent and key

    tpm2_readpublic -Q -c new_parent.ctx -n new_parent.name
    tpm2_readpublic -Q -c key.ctx -n key.name
    cat key.name new_parent.name | openssl dgst -sha256 -binary > name.hash
    tpm2_startauthsession -S session.ctx -g sha256
    tpm2_policynamehash -L policy.namehash -S session.ctx -n name.hash
    tpm2_flushcontext session.ctx
    openssl dgst -sha256 -sign signing_key_private.pem \
    -out policynamehash.signature policy.namehash
    tpm2_startauthsession -S session.ctx -g sha256
    tpm2_policyauthorize -S session.ctx -L authorized.policy -i policy.namehash \
    -n signing_key.name
    tpm2_policycommandcode -S session.ctx -L policy.dat TPM2_CC_Duplicate
    tpm2_flushcontext session.ctx

Satisfy the policy and attempt key duplication

    tpm2_verifysignature -c signing_key.ctx -g sha256 -m policy.namehash \
    -s policynamehash.signature -t verification.tkt -f rsassa
    tpm2_startauthsession -S session.ctx --policy-session -g sha256
    tpm2_policynamehash -S session.ctx -n name.hash
    tpm2_policyauthorize -S session.ctx -i policy.namehash -n signing_key.name \
    -t verification.tkt
    tpm2_policycommandcode -S session.ctx TPM2_CC_Duplicate
    tpm2_duplicate -C new_parent.ctx -c key.ctx -G null -p "session:session.ctx" \
    -r dupprv.bin -s dupseed.dat
    tpm2_flushcontext session.ctx

Returns

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.

Limitations

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.

BUGS

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

HELP

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