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tpm2_startauthsession(1)    General Commands Manual   tpm2_startauthsession(1)

NAME
       tpm2_startauthsession(1)	- Start	a session with the TPM.

SYNOPSIS
       tpm2_startauthsession [OPTIONS]

DESCRIPTION
       tpm2_startauthsession(1)	 - Starts a session with the TPM.  The default
       is to start a trial session unless the -a option	is  specified.	 Saves
       the  policy session data	to a file.  This file can then be used in sub-
       sequent tools that can use a policy file	for  authorization  or	policy
       events.

       This  will  not work with resource managers (RMs) outside of tpm2-abrmd
       (https://%20github.com/tpm2-software/tpm2-abrmd),  as  most  RMs	  will
       flush session handles when a client disconnects from the	IPC channel.

       This  will  work	 with direct TPM access, but note that internally this
       calls a ContextSave and a ContextLoad on	the session handle,  thus  the
       session cannot be saved/loaded again.

OPTIONS
       o --policy-session:

	 Start	a  policy session of type TPM_SE_POLICY.  Default without this
	 option	is TPM_SE_TRIAL.  NOTE:	A trial	session	is used	when  building
	 a policy and a	policy session is used when authenticating with	a pol-
	 icy.

       o -g, --hash-algorithm=ALGORITHM:

	 The hash algorithm used in computation	of the policy digest.

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

	 Set the session encryption and	bind key.  When	using this,  sensitive
	 data  transmitted  to the TPM will be encrypted with AES128CFB.  This
	 prevents bus snooping attacks.

       o -S, --session=FILE:

	 The name of the policy	session	file, required.

   References
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.

Authorization Formatting
       Authorization  for  use	of an object in	TPM2.0 can come	in 3 different
       forms: 1.  Password 2.  HMAC 3.	Sessions

       NOTE: "Authorizations default to	the EMPTY  PASSWORD  when  not	speci-
       fied".

   Passwords
       Passwords  are  interpreted  in	the following forms below using	prefix
       identifiers.

       Note: By	default	passwords are assumed to be in the  string  form  when
       they do not have	a prefix.

   String
       A  string  password,  specified	by  prefix "str:" or it's absence (raw
       string without prefix) is not interpreted, and is directly used for au-
       thorization.

   Examples
	      foobar
	      str:foobar

   Hex-string
       A  hex-string  password,	specified by prefix "hex:" is converted	from a
       hexidecimal form	into a byte array form,	thus allowing  passwords  with
       non-printable and/or terminal un-friendly characters.

   Example
	      hex:0x1122334455667788

   File
       A  file	based password,	specified be prefix "file:" should be the path
       of a file containing the	password to be read by the tool	or  a  "-"  to
       use  stdin.   Storing  passwords	in files prevents information leakage,
       passwords passed	as options can be read from the	process	list or	common
       shell history features.

   Examples
	      #	to use stdin and be prompted
	      file:-

	      #	to use a file from a path
	      file:path/to/password/file

	      #	to echo	a password via stdin:
	      echo foobar | tpm2_tool -p file:-

	      #	to use a bash here-string via stdin:

	      tpm2_tool	-p file:- <<< foobar

   Sessions
       When  using  a policy session to	authorize the use of an	object,	prefix
       the option argument with	the session keyword.  Then indicate a path  to
       a session file that was created with tpm2_startauthsession(1).  Option-
       ally, if	the session requires an	auth value to be sent with the session
       handle  (eg policy password), then append a + and a string as described
       in the Passwords	section.

   Examples
       To use a	session	context	file called session.ctx.

	      session:session.ctx

       To use a	session	context	file called session.ctx	AND send the authvalue
       mypassword.

	      session:session.ctx+mypassword

       To use a	session	context	file called session.ctx	AND send the HEX auth-
       value 0x11223344.

	      session:session.ctx+hex:11223344

   PCR Authorizations
       You can satisfy a PCR policy using the "pcr:" prefix and	the PCR	 mini-
       language.       The     PCR     minilanguage	is     as     follows:
       <pcr-spec>=<raw-pcr-file>

       The PCR spec is documented in in	the section "PCR bank specifiers".

       The raw-pcr-file	is an optional the output of the raw PCR  contents  as
       returned	by tpm2_pcrread(1).

       PCR bank	specifiers (common/pcr.md)

   Examples
       To satisfy a PCR	policy of sha256 on banks 0, 1,	2 and 3	use a specifi-
       er of:

	      pcr:sha256:0,1,2,3

       specifying AUTH.

COMMON OPTIONS
       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-
       able.

       The current known TCTIs are:

       o tabrmd	     -	   The	   resource	manager,     called	tabrmd
	 (https://github.com/tpm2-software/tpm2-abrmd).	 Note that tabrmd  and
	 abrmd as a tcti name are synonymous.

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

       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:

       <tcti-name>:<tcti-option-config>

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

   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.

TCTI OPTIONS
       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-
	 vice:/dev/tpm0"

       _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
	 127.0.0.1 and 2321.

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

       _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
	      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.ex-
	 ample.FooBar:

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

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

	 \--tcti:bus_type=session

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

   Start a trial session and save the session data to a	file
	      tpm2_startauthsession -S mysession.ctx

   Start a policy session and save the session data to a file
	      tpm2_startauthsession --policy-session -S	mysession.ctx

   Start an encrypted and bound	policy session and save	the
       session data to a file

	      tpm2_createprimary -c primary.ctx
	      tpm2_startauthsession --policy-session -c	primary.ctx -S mysession.ctx

Returns
       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.

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

HELP
       See the Mailing List (https://lists.01.org/mailman/listinfo/tpm2)

tpm2-tools					      tpm2_startauthsession(1)