Provided by: tpm2-tools_5.6-1build4_amd64 
NAME
tpm2_policynv(1) - Evaluates policy authorization by comparing a specified value against the contents in
the specified NV Index.
SYNOPSIS
tpm2_policynv [OPTIONS] [ARGUMENT] [ARGUMENT]
DESCRIPTION
tpm2_policynv(1) - This command evaluates policy authorization by comparing the contents written to an NV
index against the one specified in the tool options. The tool takes two arguments - (1) The NV index
specified as raw handle or an offset value to the nv handle range “TPM2_HR_NV_INDEX” and (2) Comparison
operator for magnitude comparison and or bit test operations. In the specification the NV index holding
the data is called operandA and the data that the user specifies to compare is called operandB. The com‐
parison operator can be specified as follows: * “eq” if operandA = operandB * “neq” if operandA !=
operandB * “sgt” if signed operandA > signed operandB * “ugt” if unsigned operandA > unsigned operandB *
“slt” if signed operandA < signed operandB * “ult” if unsigned operandA < unsigned operandB * “sge” if
signed operandA >= signed operandB * “uge” if unsigned operandA >= unsigned operandB * “sle” if signed
operandA <= unsigned operandB * “ule” if unsigned operandA <= unsigned operandB * “bs” if all bits set in
operandA are set in operandB * “bc” if all bits set in operandA are clear in operandB
OPTIONS
• -C, --hierarchy=OBJECT:
Specifies the hierarchy used to authorize. Supported options are:
• o for TPM_RH_OWNER
• p for TPM_RH_PLATFORM
• <num> where a hierarchy handle or nv-index may be used.
When -C isn’t explicitly passed the index handle will be used to authorize against the index. The in‐
dex auth value is set via the -p option to tpm2_nvdefine(1).
• -P, --auth=AUTH:
Specifies the authorization value for the hierarchy.
• -L, --policy=FILE:
File to save the policy digest.
• -S, --session=FILE:
The policy session file generated via the -S option to tpm2_startauthsession or saved off of a previous
tool run.
• --offset=NATURAL_NUMBER:
The offset within the NV index to start comparing at. The size of the data starting at offset and end‐
ing at size of NV index shall not exceed the size of the operand specified in the options.
• --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.
• -i, --input=FILE:
Specifies the input file with data to compare to NV Index contents. In the standard specification,
this is termed as operand or operandB more specifically . It can be specified as a file input or stdin
if option value is a “-”.
References
COMMON OPTIONS
This collection of options are common to many programs and provide information that many users may ex‐
pect.
• -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 sup‐
port not using a TCTI. Tools that do not support it will error when attempted to be used without a TC‐
TI 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 be‐
ing 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 “de‐
fault-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 sepa‐
rated 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
Test if NV index content value is equal to an input number. To do this we first create an NV index of
size 1 byte and write a value. Eg. 0xAA. Next we attempt to create a policy that becomes valid if the
equality comparison operation of the NV index content against the one specified in the tool options.
Define the test NV Index and write the value 0xAA to it
nv_test_index=0x01500001
tpm2_nvdefine -C o -p nvpass $nv_test_index -a "authread|authwrite" -s 1
echo "aa" | xxd -r -p | tpm2_nvwrite -P nvpass -i- $nv_test_index
Attempt defining policynv with wrong comparison value specified in options.
tpm2_startauthsession -S session.ctx --policy-session
### This should fail
echo 0xBB | tpm2_policynv -S session.ctx -L policy.nv -i- 0x1500001 eq -P nvpass
tpm2_flushcontext session.ctx
Attempt defining policynv with right comparison value specified in options.
tpm2_startauthsession -S session.ctx --policy-session
### This should pass
echo 0xAA | tpm2_policynv -S session.ctx -L policy.nv -i- 0x1500001 eq -P nvpass
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 fol‐
lowing:
• 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)
tpm2-tools tpm2_policynv(1)