tpm2_quote(1)

💖 NAME 💖

tpm2_quote(1) — Provide a quote and signature from the TPM. This is the tpm2_quote(1) page from the General Commands Manual, bestie, and it’s giving serious TPM main-character energy. 🔥

✨ SYNOPSIS ✨

tpm2_quote [OPTIONS]

🦋 DESCRIPTION 🦋

tpm2_quote(1) — Provide quote and signature for given list of PCRs in given algorithm/banks. That’s the whole vibe: you hand it PCRs, it hands you quote + signature realness. 💅

💅 OPTIONS 💅

• -c, --key-context=OBJECT — Context object for the quote signing key. This is the key doing the signing, bestie.
• -p, --auth=AUTH — Specifies the authorization value for AK specified by option -C. (Yes, the page says -C right there — I’m not editing it, iykyk. 🙈)
• -l, --pcr-list=PCR — The list of PCR banks and selected PCRs’ ids for each bank. Also see NOTES section below.
• -m, --message=FILE — Message output file, records the quote message that makes up the data that is signed by the TPM.
• -s, --signature=FILE — Signature output file, records the signature in the format specified via the -f option.
• -f, --format=FORMAT — Format selection for the signature output file.
• -o, --pcr=FILE — PCR output file, optional, records the list of PCR values as defined by -l.
• -F, --pcrs_format=FORMAT — Format selection for the binary blob in the PCR output file. values will output a binary blob of the PCR values. serialized will write or read a binary blob of the PCR values in the form of serialized data structure in little endian format. marshaled will will read or write a binary blob in the binary format used by the TSS2 marshaling and unmarshaling functions. If marshaled is used the data is serialized in the following order: TPML_PCR_SELECTION, UINT32 (the number of following TPML_DIGEST elements) TPML_DIGEST [number of TPML_DIGEST elements]. Optional. Default is serialized. (The “will will” is literally in the page, bestie. 💀)
• -q, --qualification=HEX_STRING_OR_PATH — Data given as a Hex string or binary file to qualify the quote, optional. This is typically used to add a nonce against replay attacks. Very “extra security garnish” of it. ✨
• -g, --hash-algorithm — Hash algorithm for signature. Defaults to sha256.
• --scheme=ALGORITHM — The signing scheme used to sign the message. Optional. Signing schemes should follow the “formatting standards”, see section “Algorithm Specifiers”. Also, see section “Supported Signing Schemes” for a list of supported signature schemes. If specified, the signature scheme must match the key type. If left unspecified, a default signature scheme for the key type will be used.
• --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. It’s giving “just the hash, no cap.” 🫶

📚 References 📚

🧸 Context Object Format 🧸

The type of a context object, whether it is a handle or file name, is determined according to the following logic in-order:

• If the argument is a file path, then the file is loaded as a restored TPM transient object.
• If the argument is a prefix match on one of:
  • owner: the owner hierarchy
  • platform: the platform hierarchy
  • endorsement: the endorsement hierarchy
  • lockout: the lockout control persistent object
• If the argument argument can be loaded as a number it will be treat as a handle, e.g. 0x81010013 and used directly. _OBJECT_.

🔐 Authorization Formatting 🔐

Authorization for use of an object in TPM2.0 can come in 3 different forms:

1. Password
2. HMAC
3. Sessions

NOTE: “Authorizations default to the EMPTY PASSWORD when not specified”.

For authentication with auth values, the tool commands implicitly generate an HMAC session. Thus passwords are not transmitted unencrypted. This does not apply to passwords defined for objects. In this case, an HMAC session should be used (see tpm2_startauthsession(1)).

Passwords

Passwords are interpreted in the following forms below using prefix identifiers.

Note: By default passwords are assumed to be in the string form when they do not have a prefix.

String

A string password, specified by prefix “str:” or it’s absence (raw string without prefix) is not interpreted, and is directly used for authorization.

Examples

foobar
str:foobar

Hex-string

A hex-string password, specified by prefix “hex:” is converted from a hexidecimal form into a byte array form, thus allowing passwords with non-printable and/or terminal un-friendly characters.

Example

hex:1122334455667788

File

A file based password, specified be prefix “file:” should be the path of a file containing the password to be read by the tool or a “-” to use stdin. Storing passwords in files prevents information leakage, passwords passed as options can be read from the process list or common shell history features.

Examples

# to use stdin and be prompted
file:-

# to use a file from a path
file:path/to/password/file

# to echo a password via stdin:
echo foobar | tpm2_tool -p file:-

# to use a bash here-string via stdin:

tpm2_tool -p file:- <<< foobar

Sessions

When using a policy session to authorize the use of an object, prefix the option argument with the session keyword. Then indicate a path to a session file that was created with tpm2_startauthsession(1). Optionally, if the session requires an auth value to be sent with the session handle (eg policy password), then append a + and a string as described in the Passwords section.

Examples

To use a session context file called session.ctx.

session:session.ctx

To use a session context file called session.ctx AND send the authvalue mypassword.

session:session.ctx+mypassword

To use a session context file called session.ctx AND send the HEX authvalue 0x11223344.

session:session.ctx+hex:11223344

PCR Authorizations

You can satisfy a PCR policy using the “pcr:” prefix and the PCR minilanguage. The PCR minilanguage is as follows:

<pcr-spec>=<raw-pcr-file>

The PCR spec is documented in in the section “PCR bank specifiers”.

The raw-pcr-file is an optional argument that contains the output of the raw PCR contents as returned by tpm2_pcrread(1).

PCR bank specifiers

Examples

To satisfy a PCR policy of sha256 on banks 0, 1, 2 and 3 use a specifier of:

pcr:sha256:0,1,2,3

specifying AUTH.

✍️ Signature Format Specifiers ✍️

Format selection for the signature output file. tss (the default) will output a binary blob according to the TPM 2.0 specification and any potential compiler padding. The option plain will output the plain signature data as defined by the used cryptographic algorithm. signature FORMAT.

🧬 PCR Bank Specifiers 🧬

PCR Bank Selection lists follow the below specification:

<BANK>:<PCR>[,<PCR>] or <BANK>:all

multiple banks may be separated by +.

For example:

sha1:3,4+sha256:all

will select PCRs 3 and 4 from the SHA1 bank and PCRs 0 to 23 from the SHA256 bank.

Certain commands support specifying forward sealing values as well:

sha1:0,1=da39a3ee5e6b4b0d3255bfef95601890afd80709,2

This will select the current values for PCRs 0 and 2, but use the specified value for PCR 1. Digest lengths must match the bank size. An optional 0x prefix will be stripped off.

Note: PCR Selections allow for up to 5 hash to pcr selection mappings. This is a limitation in design in the single call to the tpm to get the pcr values.

🌈 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.
• -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 💫

Okay so the TCTI — aka the “Transmission Interface” — is literally 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 initialize 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
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
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 🌸

tpm2_createprimary -C e -c primary.ctx

tpm2_create -C primary.ctx -u key.pub -r key.priv

tpm2_load -C primary.ctx -u key.pub -r key.priv -c key.ctx

tpm2_quote -Q -c key.ctx -l 0x0004:16,17,18+0x000b:16,17,18

📝 NOTES 💜

• The maximum number of PCR that can be quoted at once is associated with the maximum length of a bank. 🧬
• On most TPMs, it means that this tool can quote up to 24 PCRs at once.
• That this performs a detached signature. ✍️

🚦 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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🎀 That’s the whole tpm2_quote(1) page, bestie! Signed with love by tpm2-tools — the exact source/version and date are chillin’ in the footer, so peek there for the official stamp. Mwah! 💖