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tpm2_policyauthorize(1)      General Commands Manual	 tpm2_policyauthorize(1)

NAME
     tpm2_policyauthorize(1)  -  Allows  for  mutable policies by tethering to a
     signing authority.

SYNOPSIS
     tpm2_policyauthorize [OPTIONS]

DESCRIPTION
     tpm2_policyauthorize(1) - This command allows for policies to change by as-
     sociating the policy to a signing authority and allowing  the  policy  con-
     tents to change.

     1. If the input session is a trial session this tool generates a policy di-
	gest that associates a signing authority's public key name with the pol-
	icy being authorized.

     2. If  the  input	session  is  real policy session tpm2_policyauthorize(1)
	looks for a verification ticket from the TPM to attest that the TPM  has
	verified  the signature on the policy digest before authorizing the pol-
	icy in the policy digest.

OPTIONS
     * -L, --policy=FILE:

       File to save the policy digest.

     * -S, --session=FILE:

       The policy session file generated via the -S option to tpm2_startauthses-
       sion(1).

     * -i, --input=FILE:

       The policy digest that has to be authorized.

     * -q, --qualification=FILE_OR_HEX:

       The policy qualifier data signed in conjunction with the input policy di-
       gest.  This is unique data that the signer can choose to include  in  the
       signature and can either be a path or hex string.

     * -n, --name=FILE:

       File  containing the name of the verifying public key.  This ties the fi-
       nal policy digest with a signer.  This can be retrieved	with  tpm2_read-
       public(1)

     * -t, --ticket=FILE:

       The  ticket  file  to record the validation structure.  This is generated
       with tpm2_verifysignature(1).

     * --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.

   References
COMMON OPTIONS
     This collection of options are common to many programs and provide informa-
     tion that many users may expect.

     * -h,  --help=[man|no-man]:  Display the tools manpage.  By default, it at-
       tempts to invoke the manpager for the tool, however, on failure will out-
       put 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 speci-
       fied, or the manpager fails, the short options will be output to stdout.

       To successfully use the manpages feature requires the manpages to be  in-
       stalled 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 con-
       sole during its execution.  When using this option the file and line num-
       ber 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.  Defin-
       ing the environment TPM2TOOLS_ENABLE_ERRATA is  equivalent.   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  connec-
       tion.   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-con-
     fig> 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.exam-
       ple.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
     Starts  a	trial  session,  builds a PCR policy.  This PCR policy digest is
     then an input to the tpm2_policyauthorize(1) along  with  policy  qualifier
     data and a signer public.	The resultant policy digest is then used in cre-
     ation of objects.

     Subsequently when the PCR change and so does the PCR policy digest, the ac-
     tual policy digest from the tpm2_policyauthorize(1) used in creation of the
     object  will  not change.	At runtime the new PCR policy needs to be satis-
     fied along with verification of the signature on the PCR policy digest  us-
     ing tpm2_policyauthorize(1)

   Create a signing authority
	    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

   Create the authorize policy digest
	    tpm2_startauthsession -S session.ctx

	    tpm2_policyauthorize -S session.ctx -L authorized.policy -n signing_key.name

	    tpm2_flushcontext session.ctx

   Create a policy to be authorized like a PCR policy
	    tpm2_pcrread -opcr0.sha256 sha256:0

	    tpm2_startauthsession -S session.ctx

	    tpm2_policypcr -S session.ctx -l sha256:0 -f pcr0.sha256 -L pcr.policy_desired

	    tpm2_flushcontext session.ctx

   Sign the policy
	    openssl dgst -sha256 -sign signing_key_private.pem -out pcr.signature pcr.policy_desired

   Create  a  TPM  object like a sealing object with the authorized policy based
     authentication
	    tpm2_createprimary -C o -g sha256 -G rsa -c prim.ctx

	    tpm2_create -g sha256 -u sealing_pubkey.pub -r sealing_prikey.pub -i- -C prim.ctx -L authorized.policy <<< "secret to seal"

   Verify the desired policy digest comes from the signing authority,  read  the
     actual  value  of	PCR  and  check  that read policy and desired policy are
     equal.
	    tpm2_verifysignature -c signing_key.ctx -g sha256 -m  pcr.policy_desired -s pcr.signature -t verification.tkt -f rsassa

	    tpm2_startauthsession \--policy-session -S session.ctx

	    tpm2_policypcr -S session.ctx -l sha256:0 -L pcr.policy_read

	    tpm2_policyauthorize -S session.ctx -L authorized.policy -i pcr.policy_desired -n signing_key.name -t verification.tkt

	    tpm2_load -C prim.ctx -u sealing_pubkey.pub -r sealing_prikey.pub -c sealing_key.ctx

	    unsealed=$(tpm2_unseal -p"session:session.ctx" -c sealing_key.ctx)

	    echo $unsealed

	    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 com-
     mand invocations.

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

HELP
     See    the    Mailing     List	(https://lists.linuxfoundation.org/mail-
     man/listinfo/tpm2)

tpm2-tools						 tpm2_policyauthorize(1)

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