tpm2_readclock(1)

🕰️ NAME 🕰️

okay so this is the tpm2_readclock(1) manual, bestie — it retrieves the time information from the TPM. ✨

✨ SYNOPSIS ✨

tpm2_readclock [OPTIONS]

🌸 DESCRIPTION 🌸

tpm2_readclock(1) -Reads the current TPMS_TIME_INFO structure from the TPM. The structure contains the current setting of Time, Clock, resetCount, and restartCount. The structure is output as YAML to stdout. The YAML output is defined as:

time: 13673142     # 64 bit value of time TPM has been powered on in ms.
clock_info:
  clock: 13673142  # 64 bit value of time TPM has been powered on since last TPM2_Clear in ms.
  reset_count: 0   # 32 bit value of the number of TPM Resets since the last
                   # TPM2_Clear.
  restart_count: 0 # 32 bit value of the number of times that TPM2_Shutdown or
                   # _TPM_Hash_Start have occurred since the last TPM Reset or
                   # TPM2_Clear.
  safe: yes        # boolean yes|no value that no value of Clock greater than
                   # the current value of Clock has been previously reported by
                   # the TPM.

This tool takes no arguments and no tool specific options. periodt 💅

📚 References 📚

The original page has a References heading right here with literally nothing under it — empty, but still iconic 🫶.

💖 COMMON OPTIONS 💖

These options are common to many programs and give you info that many users may expect. no cap 🌈

• -h, --help=[man|no-man] — displays the tool’s manpage. By default it tries to invoke the manpager, but if that fails it outputs a short tool summary. Same behavior if you pass the man option argument, except if explicit man is requested the tool will provide errors from man on stderr. If no-man is specified, or the manpager fails, the short options will be output to stdout. To use the manpages feature successfully, the manpages need to be installed or on MANPATH — see man(1) for more details. 🎀
• -v, --version — displays version information for this tool, supported tctis, and exits. 💖
• -V, --verbose — increases the information the tool prints to the console during execution. When using this option, the file and line number are printed. 🔥
• -Q, --quiet — silences normal tool output to stdout. 🤫
• -Z, --enable-errata — enables the application of errata fixups. Useful if an errata fixup needs to be applied to commands sent to the TPM. Defining the environment variable TPM2TOOLS_ENABLE_ERRATA is equivalent. ⭐
• -z, --pwd-session — uses a 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 — enables 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 set to yes or true. (and yes, the original bullet literally trails off with “information many users may expect.” — preserving that exact chaotic energy 💀)

🔌 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. 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 🔧

These options 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 defaults 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. (yes, that trailing sentence is in the original too 🫠) 🎀

📖 EXAMPLES 📖

🕰️ Read the clock 🕰️

tpm2_readclock
time: 13673142
clock_info:
  clock: 13673142
  reset_count: 0
  restart_count: 0
  safe: yes

📊 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. 🙈

🐛 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). 🌈

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sign-off bestie: this page comes from tpm2-tools and is the tpm2_readclock(1) manual; the footer doesn’t show a separate date beyond that, so I’m not inventing one — periodt 🫶💅