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.TH "tpm2_policyauthorize" "1" "" "tpm2-tools" "General Commands Manual"
.SH NAME
\f[B]tpm2_policyauthorize\f[R](1) - Allows for mutable policies by
tethering to a signing authority.
.SH SYNOPSIS
\f[B]tpm2_policyauthorize\f[R] [\f[I]OPTIONS\f[R]]
.SH DESCRIPTION
\f[B]tpm2_policyauthorize\f[R](1) - This command allows for policies to
change by associating the policy to a signing authority and allowing the
policy contents to change.
.IP "1." 3
If the input session is a trial session this tool generates a policy
digest that associates a signing authority\[cq]s public key name with
the policy being authorized.
.IP "2." 3
If the input session is real policy session
\f[B]tpm2_policyauthorize\f[R](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.
.SH OPTIONS
.IP \[bu] 2
\f[B]-L\f[R], \f[B]--policy\f[R]=\f[I]FILE\f[R]:
.RS 2
.PP
File to save the policy digest.
.RE
.IP \[bu] 2
\f[B]-S\f[R], \f[B]--session\f[R]=\f[I]FILE\f[R]:
.RS 2
.PP
The policy session file generated via the \f[B]-S\f[R] option to
\f[B]tpm2_startauthsession\f[R](1).
.RE
.IP \[bu] 2
\f[B]-i\f[R], \f[B]--input\f[R]=\f[I]FILE\f[R]:
.RS 2
.PP
The policy digest that has to be authorized.
.RE
.IP \[bu] 2
\f[B]-q\f[R], \f[B]--qualification\f[R]=\f[I]FILE_OR_HEX\f[R]:
.RS 2
.PP
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.
.RE
.IP \[bu] 2
\f[B]-n\f[R], \f[B]--name\f[R]=\f[I]FILE\f[R]:
.RS 2
.PP
File containing the name of the verifying public key.
This ties the final policy digest with a signer.
This can be retrieved with \f[B]tpm2_readpublic\f[R](1)
.RE
.IP \[bu] 2
\f[B]-t\f[R], \f[B]--ticket\f[R]=\f[I]FILE\f[R]:
.RS 2
.PP
The ticket file to record the validation structure.
This is generated with \f[B]tpm2_verifysignature\f[R](1).
.RE
.IP \[bu] 2
\f[B]--cphash\f[R]=\f[I]FILE\f[R]
.RS 2
.PP
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.
.RE
.SS References
.SH COMMON OPTIONS
This collection of options are common to many programs and provide
information that many users may expect.
.IP \[bu] 2
\f[B]-h\f[R], \f[B]--help=[man|no-man]\f[R]: 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 \[lq]man\[rq] option argument is
specified, however if explicit \[lq]man\[rq] is requested, the tool will
provide errors from man on stderr.
If the \[lq]no-man\[rq] option if specified, or the manpager fails, the
short options will be output to stdout.
.RS 2
.PP
To successfully use the manpages feature requires the manpages to be
installed or on \f[I]MANPATH\f[R], See man(1) for more details.
.RE
.IP \[bu] 2
\f[B]-v\f[R], \f[B]--version\f[R]: Display version information for this
tool, supported tctis and exit.
.IP \[bu] 2
\f[B]-V\f[R], \f[B]--verbose\f[R]: Increase the information that the
tool prints to the console during its execution.
When using this option the file and line number are printed.
.IP \[bu] 2
\f[B]-Q\f[R], \f[B]--quiet\f[R]: Silence normal tool output to stdout.
.IP \[bu] 2
\f[B]-Z\f[R], \f[B]--enable-errata\f[R]: 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.
.IP \[bu] 2
\f[B]-R\f[R], \f[B]--autoflush\f[R]: Enable autoflush for transient
objects created by the command.
If a parent object is loaded from a context file also the transient
parent object will be flushed.
Autoflush can also be activated if the environment variable
TPM2TOOLS_AUTOFLUSH is is set to yes or true.
information many users may expect.
.SH TCTI Configuration
The TCTI or \[lq]Transmission Interface\[rq] is the communication
mechanism with the TPM.
TCTIs can be changed for communication with TPMs across different
mediums.
.PP
To control the TCTI, the tools respect:
.IP "1." 3
The command line option \f[B]-T\f[R] or \f[B]--tcti\f[R]
.IP "2." 3
The environment variable: \f[I]TPM2TOOLS_TCTI\f[R].
.PP
\f[B]Note:\f[R] The command line option always overrides the environment
variable.
.PP
The current known TCTIs are:
.IP \[bu] 2
tabrmd - The resource manager, called \c
.UR https://github.com/tpm2-software/tpm2-abrmd
tabrmd
.UE \c
\&.
Note that tabrmd and abrmd as a tcti name are synonymous.
.IP \[bu] 2
mssim - Typically used for communicating to the TPM software simulator.
.IP \[bu] 2
device - Used when talking directly to a TPM device file.
.IP \[bu] 2
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 \f[I]ANY\f[R] options and \f[I]MUST BE\f[R] presented
as the exact text of \[lq]none\[rq].
.PP
The arguments to either the command line option or the environment
variable are in the form:
.PP
\f[CR]<tcti-name>:<tcti-option-config>\f[R]
.PP
Specifying an empty string for either the \f[CR]<tcti-name>\f[R] or
\f[CR]<tcti-option-config>\f[R] results in the default being used for
that portion respectively.
.SS TCTI Defaults
When a TCTI is not specified, the default TCTI is searched for using
\f[I]dlopen(3)\f[R] semantics.
The tools will search for \f[I]tabrmd\f[R], \f[I]device\f[R] and
\f[I]mssim\f[R] TCTIs \f[B]IN THAT ORDER\f[R] and \f[B]USE THE FIRST ONE
FOUND\f[R].
You can query what TCTI will be chosen as the default by using the
\f[B]-v\f[R] option to print the version information.
The \[lq]default-tcti\[rq] key-value pair will indicate which of the
aforementioned TCTIs is the default.
.SS Custom TCTIs
Any TCTI that implements the dynamic TCTI interface can be loaded.
The tools internally use \f[I]dlopen(3)\f[R], and the raw
\f[I]tcti-name\f[R] value is used for the lookup.
Thus, this could be a path to the shared library, or a library name as
understood by \f[I]dlopen(3)\f[R] semantics.
.SH TCTI OPTIONS
This collection of options are used to configure the various known TCTI
modules available:
.IP \[bu] 2
\f[B]device\f[R]: For the device TCTI, the TPM character device file for
use by the device TCTI can be specified.
The default is \f[I]/dev/tpm0\f[R].
.RS 2
.PP
Example: \f[B]-T device:/dev/tpm0\f[R] or \f[B]export
\f[BI]TPM2TOOLS_TCTI\f[B]=\[lq]device:/dev/tpm0\[rq]\f[R]
.RE
.IP \[bu] 2
\f[B]mssim\f[R]: 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.
.RS 2
.PP
Example: \f[B]-T mssim:host=localhost,port=2321\f[R] or \f[B]export
\f[BI]TPM2TOOLS_TCTI\f[B]=\[lq]mssim:host=localhost,port=2321\[rq]\f[R]
.RE
.IP \[bu] 2
\f[B]abrmd\f[R]: 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.
.RS 2
.IP \[bu] 2
TCTI abrmd supports two keys:
.RS 2
.IP "1." 3
`bus_name' : The name of the tabrmd service on the bus (a string).
.IP "2." 3
`bus_type' : The type of the dbus instance (a string) limited to
`session' and `system'.
.RE
.PP
Specify the tabrmd tcti name and a config string of
\f[CR]bus_name=com.example.FooBar\f[R]:
.IP
.EX
\[rs]--tcti=tabrmd:bus_name=com.example.FooBar
.EE
.PP
Specify the default (abrmd) tcti and a config string of
\f[CR]bus_type=session\f[R]:
.IP
.EX
\[rs]--tcti:bus_type=session
.EE
.PP
\f[B]NOTE\f[R]: abrmd and tabrmd are synonymous.
the various known TCTI modules.
.RE
.SH EXAMPLES
Starts a \f[I]trial\f[R] session, builds a PCR policy.
This PCR policy digest is then an input to the
\f[B]tpm2_policyauthorize\f[R](1) along with policy qualifier data and a
signer public.
The resultant policy digest is then used in creation of objects.
.PP
Subsequently when the PCR change and so does the PCR policy digest, the
actual policy digest from the \f[B]tpm2_policyauthorize\f[R](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
\f[B]tpm2_policyauthorize\f[R](1)
.SS Create a signing authority
.IP
.EX
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
.EE
.SS Create the authorize policy digest
.IP
.EX
tpm2_startauthsession -S session.ctx

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

tpm2_flushcontext session.ctx
.EE
.SS Create a policy to be authorized like a PCR policy
.IP
.EX
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
.EE
.SS Sign the policy
.IP
.EX
openssl dgst -sha256 -sign signing_key_private.pem -out pcr.signature pcr.policy_desired
.EE
.SS Create a TPM object like a sealing object with the authorized policy based authentication
.IP
.EX
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 <<< \[dq]secret to seal\[dq]
.EE
.SS 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.
.IP
.EX
tpm2_verifysignature -c signing_key.ctx -g sha256 -m  pcr.policy_desired -s pcr.signature -t verification.tkt -f rsassa

tpm2_startauthsession \[rs]--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\[dq]session:session.ctx\[dq] -c sealing_key.ctx)

echo $unsealed

tpm2_flushcontext session.ctx
.EE
.SH Returns
Tools can return any of the following codes:
.IP \[bu] 2
0 - Success.
.IP \[bu] 2
1 - General non-specific error.
.IP \[bu] 2
2 - Options handling error.
.IP \[bu] 2
3 - Authentication error.
.IP \[bu] 2
4 - TCTI related error.
.IP \[bu] 2
5 - Non supported scheme.
Applicable to tpm2_testparams.
.SH Limitations
It expects a session to be already established via
\f[B]tpm2_startauthsession\f[R](1) and requires one of the following:
.IP \[bu] 2
direct device access
.IP \[bu] 2
extended session support with \f[B]tpm2-abrmd\f[R].
.PP
Without it, most resource managers \f[B]will not\f[R] save session state
between command invocations.
.SH BUGS
\c
.UR https://github.com/tpm2-software/tpm2-tools/issues
Github Issues
.UE \c
.SH HELP
See the \c
.UR https://lists.linuxfoundation.org/mailman/listinfo/tpm2
Mailing List
.UE \c