tpm2_policytemplate(1)

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version 5.8 · 10 versions
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✨ NAME ✨

Hiii bestie, welcome to tpm2_policytemplate(1) from the General Commands Manual — this is the page for coupling a policy with the public template data digest of an object. 💅

tpm2_policytemplate(1) — couples a policy with the public template data digest of an object.

🫶 SYNOPSIS 🫶

tpm2_policytemplate [OPTIONS]

💖 DESCRIPTION 💖

tpm2_policytemplate(1) couples a policy with the public template data digest of an object.

It's a deferred assertion, meaning the hash of the public template data of an object gets checked against the one specified in the policy. It's giving “trust but verify” but make it TPM. 🔥

🎀 OPTIONS 🎀

  • -L, --policy=FILE — the file to save the compounded policy digest into. 💾
  • -S, --session=FILE — the policy session file generated via the -S option to tpm2_startauthsession(1). 🗂️
  • --template-hash=FILE — the file containing the hash of the public template of the object. (The original option list renders this with a fancy en dash as –template-hash=FILE, but the examples use --template-hash.) 🧚

📚 References 📚

(The original page has this heading here with nothing under it — leaving the empty aesthetic intact, bestie.)

🌈 COMMON OPTIONS 🌈

These options are common to many programs and provide information that many users may expect. Group-chat essentials, basically. 🫶

  • -h, --help=[man|no-man] — Display the tool's manpage. By default, it attempts to invoke the manpager for the tool; on failure it 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 is 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. 🛠️
  • -z, --pwd-session — Use password session instead of a HMAC session for authentication. A clear text password is passed to the TPM to authorize the action. This option can be used to avoid problems when unsalted sessions are used in OpenSSL FIPS mode. If auth values are used a salted session should be used for authentication. 🔐
  • -R, --autoflush — 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.) 🚿

🌐 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. It's the pipeline, the vibe conduit, the whole connection confessional. 💫

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. Periodt. 💅

The current known TCTIs are:

  • tabrmd — The resource manager, called tabrmd. 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 🍓

Restrict the primary object type created under a hierarchy

tpm2_createprimary -C o -c prim.ctx --template-data template.data

cat template.data | openssl dgst -sha256 -binary -out template.hash

tpm2_startauthsession -S session.ctx -g sha256
tpm2_policytemplate -S session.ctx -L policy.template \
--template-hash template.hash
tpm2_flushcontext session.ctx

tpm2_setprimarypolicy -C o -g sha256 -L policy.template

tpm2_startauthsession -S session.ctx -g sha256 --policy-session
tpm2_policytemplate -S session.ctx --template-hash template.hash
tpm2_createprimary -C o -c prim2.ctx -P session:session.ctx
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. No cap, this is the “bring your own session” situation. 😭

🐛 BUGS 🐛

Github Issues

🆘 HELP 🆘

See the Mailing List

📜 License 📜

This work is licensed under the Creative Commons Attribution 4.0 International License (CC BY 4.0).

Cute sign-off: source/version tpm2-tools, manual tpm2_policytemplate(1), and the footer doesn't give a date — so that's the only footer tea we have, bestie. 💅✨

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