tpm2_certify(1)

💖 NAME 💖

tpm2_certify(1) — straight outta the General Commands Manual — is here to prove that an object is loaded in the TPM. periodt. 💅

✨ SYNOPSIS ✨

tpm2_certify [OPTIONS]

🌸 DESCRIPTION 🌸

Okay so bestie, tpm2_certify(1) proves that an object with a specific NAME is loaded in the TPM. That’s the whole main character energy of this command. By certifying that the object is loaded, the TPM warrants that a public area with a given NAME is self-consistent and associated with a valid sensitive area. ✨

If a relying party has a public area that has the same NAME as a NAME certified with this command, then the values in that public area are correct. Important vibe check: an object that only has its public area loaded cannot be certified. 😭

💅 OPTIONS 💅

These options control the certification — let’s go:

• -c, --certifiedkey-context=OBJECT — the object to be certified. 🎀
• -C, --signingkey-context=OBJECT — the key used to sign the attestation structure. 🔥
• -P, --certifiedkey-auth=AUTH — the authorization value provided for the object specified with -c. 🔐
• -g, --hash-algorithm=ALGORITHM — the hash algorithm to use in signature generation. ✨
• --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. 💅
• -p, --signingkey-auth=AUTH — the authorization value for the signing key specified with -C. 🫶
• -o, --attestation=FILE — output file name for the attestation data. 🦋
• -q, --qualifying-data=HEX_STRING_OR_PATH — data given as a Hex string or binary file to qualify the certification, optional. This is typically used to add a nonce against replay attacks. The default is: 0x00, 0xff, 0x55, 0xaa. 🌈
• -s, --signature=FILE — output file name for the signature data. ⭐
• -f, --format=FORMAT — format selection for the signature output file. 🎀
• --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, unless rphash is also required. 💀
• --rphash=FILE — file path to record the hash of the response parameters. This is commonly termed as rpHash. 🙈
• -S, --session=FILE — the session created using tpm2_startauthsession. This can be used to specify an auxiliary session for auditing and or encryption/decryption of the parameters. 🪄

📚 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, bestie:

• 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 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 the section PCR bank specifiers.

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).

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

Then the page literally says: specifying AUTH. 💀

🧠 Algorithm Specifiers 🧠

Options that take algorithms support “nice-names”.

There are two major algorithm specification string classes, simple and complex. Only certain algorithms will be accepted by the TPM, based on usage and conditions.

Simple specifiers

These are strings with no additional specification data. When creating objects, non-specified portions of an object are assumed to defaults. You can find the list of known “Simple Specifiers” below.

Asymmetric

• rsa
• ecc

Symmetric

• aes
• camellia
• sm4

Hashing Algorithms

• sha1
• sha256
• sha384
• sha512
• sm3_256
• sha3_256
• sha3_384
• sha3_512

Keyed Hash

• hmac
• xor

Signing Schemes

• rsassa
• rsapss
• ecdsa
• ecdaa
• ecschnorr
• sm2

Asymmetric Encryption Schemes

• oaep
• rsaes
• ecdh

Modes

• ctr
• ofb
• cbc
• cfb
• ecb

Misc

• null

Complex Specifiers

Objects, when specified for creation by the TPM, have numerous algorithms to populate in the public data. Things like type, scheme and asymmetric details, key size, etc. Below is the general format for specifying this data: <type>:<scheme>:<symmetric-details>

Type Specifiers

This portion of the complex algorithm specifier is required. The remaining scheme and symmetric details will default based on the type specified and the type of the object being created.

• aes - Default AES: aes128
• aes128<mode> - 128 bit AES with optional mode (ctr|ofb|cbc|cfb|ecb). If mode is not specified, defaults to null.
• aes192<mode> - Same as aes128<mode>, except for a 192 bit key size.
• aes256<mode> - Same as aes128<mode>, except for a 256 bit key size.
• sm4 - Default SM4: sm4128
• sm4128 or sm4_128 <mode> - 128 bit SM4 with optional mode (ctr|ofb|cbc|cfb|ecb). If mode is not specified, defaults to null.
• ecc - Elliptical Curve, defaults to ecc256.
• ecc192 or ecc_nist_p192 - 192 bit ECC NIST curve
• ecc224 or ecc_nist_p224 - 224 bit ECC NIST curve
• ecc256 or ecc_nist_p256 - 256 bit ECC NIST curve
• ecc384 or ecc_nist_p384 - 384 bit ECC NIST curve
• ecc521 or ecc_nist_p521 - 521 bit ECC NIST curve
• ecc_sm2 or ecc_sm2_p256 - 256 bit SM2 curve
• rsa - Default RSA: rsa2048
• rsa1024 - RSA with 1024 bit keysize.
• rsa2048 - RSA with 2048 bit keysize.
• rsa3072 - RSA with 3072 bit keysize.
• rsa4096 - RSA with 4096 bit keysize.

Scheme Specifiers

Next, is an optional field, it can be skipped.

Schemes are usually Signing Schemes or Asymmetric Encryption Schemes. Most signing schemes take a hash algorithm directly following the signing scheme. If the hash algorithm is missing, it defaults to sha256. Some take no arguments, and some take multiple arguments.

Hash Optional Scheme Specifiers

These scheme specifiers are followed by a dash and a valid hash algorithm, For example: oaep-sha256.

• oaep
• ecdh
• rsassa
• rsapss
• ecdsa
• ecschnorr
• sm2

Multiple Option Scheme Specifiers

This scheme specifier is followed by a count (max size UINT16) then followed by a dash(-) and a valid hash algorithm. The listed one is ecdaa. For example, ecdaa4-sha256. If no count is specified, it defaults to 4.

No Option Scheme Specifiers

This scheme specifier takes NO arguments. The listed one is rsaes.

Symmetric Details Specifiers

This field is optional, and defaults based on the type of object being created and it’s attributes. Generally, any valid Symmetric specifier from the Type Specifiers list should work. If not specified, an asymmetric objects symmetric details defaults to aes128cfb.

Examples

Create an rsa2048 key with an rsaes asymmetric encryption scheme

tpm2_create -C parent.ctx -G rsa2048:rsaes -u key.pub -r key.priv

Create an ecc256 key with an ecdaa signing scheme with a count of 4 and sha384 hash

/tpm2_create -C parent.ctx -G ecc256:ecdaa4-sha384 -u key.pub -r
key.priv cryptographic algorithms ALGORITHM.

💫 Signature Format Specifiers 💫

okay so this one is literally just about how the signature gets written out, bestie. It's the format selection for the signature output file, and you've got two vibes to pick from:

• tss — this is the default, and it outputs a binary blob according to the TPM 2.0 specification, plus any potential compiler padding. So, like, very official, very structured.
• plain — this one outputs the plain signature data as defined by the used cryptographic algorithm. Just the raw goods.

That's the whole signature FORMAT situation. Slay. 💅

---

🌸 COMMON OPTIONS 🌸

This collection of options are common to many programs and provide information that many users may expect. Basically it's the shared little goodie bag every tool dips into. 🎀

• -h, --help=[man|no-man] — Display the tool's manpage. By default it attempts to invoke the manpager for the tool, however on failure it will output a short tool summary. This is the same behavior if the man option argument is specified — but 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. iykyk 📖
• -v, --version — Display version information for this tool, supported tctis, and exit. quick little peek, then dip ✨
• -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. she's chatty and she's proud of it 💬
• -Q, --quiet — Silence normal tool output to stdout. the silent treatment, but make it a feature 🤫
• -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. little patch-up era 🩹
• -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. no cap, read that last sentence twice 🔐
• -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. (yes, the page says "is is" and then just. ends like that. iconic honestly 😭💀 we keep the lore intact)

---

🦋 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. think of it as picking which phone line you're calling the TPM on ☎️

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. command line stays the main character 👑

The current known TCTIs are:

• tabrmd — The resource manager, called tabrmd. Note that tabrmd and abrmd as a tcti name are synonymous. two names, one queen 💖
• mssim — Typically used for communicating to the TPM software simulator. simulator szn 🧚
• device — Used when talking directly to a TPM device file. no middleman, direct line 🔥
• 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". capital-letters MUST, we're so serious about this one 🚨

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. leave it blank and the default steps in 🫶

⭐ 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. yes, all caps, because the order genuinely matters bestie. 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. cute little detective moment 🔍

💜 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. bring your own TCTI to the party, we love an indie plugin 🎀

---

🌈 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. (yep, the page just trails off there at the end — we're preserving the exact chaos, don't come for me 🙈)

---

✨ EXAMPLES ✨

Create a primary key and certify it with a signing key. this is the whole pipeline, bestie, watch and learn 💖

tpm2_createprimary -Q -C e -g sha256 -G rsa -c primary.ctx

tpm2_create -Q -g sha256 -G rsa -u certify.pub -r certify.priv -C primary.ctx

tpm2_load -Q -C primary.ctx -u certify.pub -r certify.priv -n certify.name \
-c certify.ctx

tpm2_certify -Q -c primary.ctx -C certify.ctx -g sha256 -o attest.out -s sig.out

---

🫶 Returns 🫶

Tools can return any of the following codes:

• 0 — Success. we love to see it 🎉
• 1 — General non-specific error. the vague "something's off" energy 😬
• 2 — Options handling error. you typed something weird 💀
• 3 — Authentication error. wrong password behavior 🔐
• 4 — TCTI related error. the phone line is down ☎️
• 5 — Non supported scheme. Applicable to tpm2_testparams. not in this tool's job description 🚫

---

🐛 BUGS 🐛

Github Issues — that's where you take your problems. bring receipts. 📝

---

🧚 HELP 🧚

See the Mailing List — the collective knowledge is out there, go absorb it. 💌

---

👑 License 👑

This work is licensed under the Creative Commons Attribution 4.0 International License (CC BY 4.0). share responsibly, credit the source, be a good citizen 🫶

---

okay that's the whole page, bestie, you're officially certified 💅✨ this was tpm2-tools bringing you tpm2_certify(1) — go forth and certify something iconic 🌸🦋