Ubuntu Manpage: tpm2_flushcontext(1) - Remove a specified handle, or all contexts associated with a

NAME

       tpm2_flushcontext(1)  -  Remove  a  specified  handle,  or  all contexts associated with a
       transient object, loaded session or saved session from the TPM.

SYNOPSIS

       tpm2_flushcontext [OPTIONS] [ARGUMENT]

DESCRIPTION

       tpm2_flushcontext(1) - Remove a specified  handle,  or  all  contexts  associated  with  a
       transient  object, loaded session or saved session from the TPM.  The object to be flushed
       is specified as the first argument to the tool and is in one of the following forms: - The
       handle  of the object to be flushed from the TPM.  Must be a valid handle number.  - Flush
       a session via a session file.  A session file is generated from tpm2_startauthsession(1)’s
       -S option.

OPTIONS

       • -t, --transient-object:

         Remove all transient objects.

       • -l, --loaded-session:

         Remove all loaded sessions.

       • -s, --saved-session:

         Remove all saved sessions.

       • ARGUMENT  the  command  line  argument  specifies  the OBJECT to be removed from the TPM
         resident memory.

       • --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.

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.

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.

EXAMPLES

   Flushing a Transient Object
       Typically, when using the TPM, the interactions occur through  a  resource  manager,  like
       tpm2-abrmd(8).   When  the  process  exits,  transient  object handles are flushed.  Thus,
       flushing transient objects through the  command  line  is  not  required.   However,  when
       interacting  with  the TPM directly, this scenario is possible.  The below example assumes
       direct TPM access not brokered by a  resource  manager.   Specifically  we  will  use  the
       simulator.

              tpm2_createprimary -Tmssim -c primary.ctx

              tpm2_getcap -T mssim handles-transient
              - 0x80000000

              tpm2_flushcontext -T mssim 0x80000000

   Flush All the Transient Objects
              tpm2_flushcontext \--transient-object

   Flush a Session
              tpm2_startauthsession -S session.dat

              tpm2_flushcontext session.dat

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.

BUGS

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

HELP

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