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tpm2_readpublic(1)	    General Commands Manual	    tpm2_readpublic(1)

       tpm2_readpublic(1) - Read the public area of a loaded object.

       tpm2_readpublic [OPTIONS]

       tpm2_readpublic(1) - Reads the public area of a loaded object.

       o -c, --object-context=OBJECT:

	 Context object	for the	object to read.

       o -n, --name=FILE:

	 An optional file to save the name structure of	the object.

       o -f, --format=FORMAT:

	 Public	key format.

       o -o, --output=FILE:

	 The output file path, recording the public portion of the object.

       o -t, --serialized-handle=HANDLE:

	 If  the  object  to be	read is	a persistent object specified by a raw
	 handle, optionally save the serialized	handle for  use	 later.	  This
	 routine  does	NOT verify the name of the object being	read.  Callers
	 should	ensure that the	contents of name match	the  expected  objects

Context	Object Format
       The  type  of a context object, whether it is a handle or file name, is
       determined according to the following logic in-order:

       o If the	argument is a file path, then the file is loaded as a restored
	 TPM transient object.

       o If the	argument is a prefix match on one of:

	 o owner: the owner hierarchy

	 o platform: the platform hierarchy

	 o endorsement:	the endorsement	hierarchy

	 o lockout: the	lockout	control	persistent object

       o If  the  argument argument can	be loaded as a number it will be treat
	 as a handle, e.g.  0x81010013 and used	directly.OBJECT.

       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-
	 ules.	# EXAMPLES

   Create a primary object and read the	public structure in an openssl
       compliant format

	      tpm2_createprimary -c primary.ctx
	      tpm2_readpublic -c primary.ctx -o	output.dat -f pem

   Serialize an	existing persistent object handle to disk for later use
       This work-flow is primarily intended for	existing  persistent  TPM  ob-
       jects.	This work-flow does not	verify that the	name of	the serialized
       object matches the expected, and	thus the serialized  handle  could  be
       pointing	 to  an	attacker controlled object if no verification is done.
       If you are creating an object from scratch, save	the serialized	handle
       when making the object persistent.

       We assume that an object	has already been persisted, for	example	via:

	      #	We assume that an object has already been persisted, for example
	      tpm2_createprimary -c primary.ctx

	      #	context	files have all the information for the TPM to verify the object
	      tpm2_evictcontrol	-c primary.ctx
	      persistent-handle: 0x81000001
	      action: persisted

       Next use	the persistent handle to get a serialized handle:

	      #	The persistent handle output could be at an attacker controlled	object,
	      #	best practice is to use	the option "-o:	for tpm2_evictcontrol to get a
	      #	serialized handle instead.

	      tpm2_readpublic -c 0x81000001 -o output.dat -f pem -t primary.handle

	      #	use this verified handle in an encrypted session with the tpm
	      tpm2_startauthsession --policy-session -S	session.ctx -c primary.handle

       For new objects,	its best to use	all serialized handles.

       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.

       Github Issues (

       See the Mailing List (

tpm2-tools						    tpm2_readpublic(1)


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