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tpm2_policynvwritten(1)	    General Commands Manual    tpm2_policynvwritten(1)

       tpm2_policynvwritten(1)	-  Restrict  TPM  object  authorization	to the
       written state of	an NV index.

       tpm2_policynvwritten [OPTIONS] [ARGUMENT]

       tpm2_policynvwritten(1) - Restricts TPM	object	authorization  to  the
       written	state  of an NV	index.	Useful when creating write once	NV in-

       As an [ARGUMENT]	it takes the expected written state of the  NV	index.
       It can be specified as s|c|0|1.

       o -S, --session=FILE:

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

       o -L, --policy=FILE:

	 File to save the policy digest.

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

       o -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 re-
	 quested, the tool will	provide	errors from man	 on  stderr.   If  the
	 "no-man"  option  if  specified, or the manpager fails, the short op-
	 tions 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.

       o -v,  --version:  Display version information for this tool, supported
	 tctis and exit.

       o -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.

       o -Q, --quiet: Silence normal tool output to stdout.

       o -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.   in-
	 formation 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 vari-

       The current known TCTIs are:

       o tabrmd	    -	  The	  resource     manager,	    called	tabrmd
	 (	  Note that tabrmd and
	 abrmd as a tcti name are synonymous.

       o mssim - Typically used	for communicating to the TPM software  simula-

       o device	- Used when talking directly to	a TPM device file.

       o 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:


       Specifying an empty string for  either  the  <tcti-name>	 or  <tcti-op-
       tion-config> results in the default being used for that portion respec-

   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	 indi-
       cate 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 li-
       brary name as understood	by dlopen(3) semantics.

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

       o 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="de-

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

	 Example:  -T  mssim:host=localhost,port=2321  or export TPM2TOOLS_TC-

       _o abrmd:	For the	abrmd TCTI, the	configuration string format is	a  se-
	 ries  of  simple  key value pairs separated by	a ',' character.  Each
	 key and value string are separated by a '=' character.

	 o TCTI	abrmd supports two keys:

	   1. 'bus_name' : The name of	the  tabrmd  service  on  the  bus  (a

	   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.ex-


	 Specify the default (abrmd) tcti and a	config string of bus_type=ses-


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

       Create  a write once NV index.  To do this the NV index is defined with
       a write policy that is valid  only  if  the  NV	index  attribute  "TP-
       MA_NV_WRITTEN" was never	set.

   Define the NV index write policy
	      tpm2_startauthsession -S session.dat
	      tpm2_policycommandcode -S	session.dat TPM2_CC_NV_Write
	      tpm2_policynvwritten -S session.dat -L nvwrite.policy c
	      tpm2_flushcontext	session.dat

   Define the NV index with the	policy
	       tpm2_nvdefine -s	1 -a "authread|policywrite" -p nvrdpass	-L nvwrite.policy

   Write the NV	index by satisfying the	policy
	      tpm2_startauthsession -S session.dat --policy-session
	      tpm2_policycommandcode -S	session.dat TPM2_CC_NV_Write
	      tpm2_policynvwritten -S session.dat c
	      echo 0xAA	| xxd -r -p | tpm2_nvwrite 0x01000000 -i- -P session:session.dat
	      tpm2_flushcontext	session.dat

       Tools can return	any of the following codes:

       o 0 - Success.

       o 1 - General non-specific error.

       o 2 - Options handling error.

       o 3 - Authentication error.

       o 4 - TCTI related error.

       o 5 - Non supported scheme.  Applicable to tpm2_testparams.

       It  expects  a session to be already established	via tpm2_startauthses-
       sion(1) and requires one	of the following:

       o direct	device access

       o extended session support with tpm2-abrmd.

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

       Github Issues (

       See the Mailing List (

tpm2-tools					       tpm2_policynvwritten(1)


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