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 associating the
       policy to a signing authority and allowing the policy contents to change.

       1. If the input session is a trial session  this  tool  generates  a  policy  digest  that
          associates a signing authority’s public key name with the policy 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 policy 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_startauthsession(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 digest.  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 final policy digest
         with a signer.  This can be retrieved with tpm2_readpublic(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 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.  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 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.  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 creation of objects.

       Subsequently when the PCR change and so does the PCR  policy  digest,  the  actual  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  satisfied  along  with  verification  of  the
       signature on the PCR policy digest using 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  command
       invocations.

BUGS

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

HELP

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