tpm2_createek(1)

📦
version 5.8 · 10 versions
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✨ NAME ✨

tpm2_createek(1) — Generate TCG profile compliant endorsement key.

Okay bestie, this is the tpm2_createek(1) page from the General Commands Manual 💖 and it’s all about generating a TCG profile compliant endorsement key. Slay.

🌸 SYNOPSIS 🌸

tpm2_createek [OPTIONS]

🦋 DESCRIPTION 🦋

tpm2_createek(1) — Generate TCG profile compliant endorsement key (EK), which is the primary object of the endorsement hierarchy. That’s the main character right there 👑.

If a transient object is generated the tool outputs a context file specified with -c.

Refer to: http://www.trustedcomputinggroup.org/files/static_page_files/7CAA5687-1A4B-B294-D04080D058E86C5F

💅 OPTIONS 💅

  • -P, --eh-auth=AUTH — The authorization value for the endorsement hierarchy.
  • -w, --owner-auth=AUTH — The authorization value for the owner hierarchy.
  • -c, --ek-context=OBJECT or FILE — Either a file path or a persistent handle value to save the endorsement key. If a value of - is passed the tool will find a vacant persistent handle to use and print out the automatically selected handle. If one saves the context file via this option and the public key via the -u option, the EK can be restored via a call to tpm2_loadexternal(1).
  • -G, --key-algorithm=ALGORITHM — The endorsement key algorithm. Supports:
    • ecc — A NIST_P256 key by default. Alternative curves can be selected using algorithm specifiers (e.g. ecc384 or ecc_nist_p384) .
    • rsa — An RSA2048 key.
    • keyedhash — hmac key. By default, For NIST_P256 and RSA2048 the LOW range template defined in the EK Credential Profile will be used. The HIGH range template can be selected by adding the suffix _high to the algorithm name.
  • -u, --public=FILE — The optional input for a file to save the public portion of endorsement key.
  • -t, --template — The optional manufacturer defined endorsement key template and nonce from fixed NV Indices to populate the TPM2B_PUBLIC public area. See the TCG EK Credential Profile specification for more information: https://trustedcomputinggroup.org/wp-content/uploads/TCG_IWG_Credential_Profile_EK_V2.1_R13.pdf
  • -f, --format — Format selection for the public key output file. tss (the default) will output a binary blob according to the TPM 2.0 Specification. pem will output an OpenSSL compatible PEM encoded public key. der will output an OpenSSL compatible DER encoded public key. tpmt will output a binary blob of the TPMT_PUBLIC struct referenced by TPM 2.0 specs.

Public key format.

📚 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.

🧬 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. ecdaa For example, ecdaa4-sha256. If no count is specified, it defaults to 4.

No Option Scheme Specifiers

This scheme specifier takes NO arguments. 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.

🌸 COMMON OPTIONS 🌸

okay bestie so this little collection of options is shared across so many of the tools, and they're basically the stuff everyone expects to be able to do. here's the rundown 💅

  • -h, --help=[man|no-man] — shows you the tool's manpage. by default it tries to invoke the manpager, and if that flops it'll drop a short tool summary instead. same behavior if you pass the man option argument — but if you explicitly ask for man, the tool will actually surface errors from man on stderr. if you say no-man, or the manpager just refuses to cooperate, the short options get printed to stdout. > heads up: the manpages feature only works if the manpages are actually installed or sitting on MANPATH — peep man(1) for the deets 🫶
  • -v, --version — prints version info for this tool plus the supported tctis, then exits. slay.
  • -V, --verbose — cranks up how much the tool yaps to the console while it's running. when you use this one, the file and line number get printed too. iykyk 🔥
  • -Q, --quiet — silences the normal tool output to stdout. shhh 🤫
  • -Z, --enable-errata — turns on the application of errata fixups. useful when an errata fixup genuinely needs to be applied to commands being sent to the TPM. defining the environment variable TPM2TOOLS_ENABLE_ERRATA does the exact same thing ✨
  • -z, --pwd-session — uses a password session instead of a HMAC session for authentication. a clear text password gets passed to the TPM to authorize the action. this option exists so you can dodge problems when unsalted sessions are used in OpenSSL FIPS mode. > but fr: if auth values are in play, a salted session is what you should be using for authentication 🙈
  • -R, --autoflush — enables autoflush for transient objects created by the command. if a parent object is loaded from a context file, then the transient parent object gets flushed too. autoflush can also be switched on if the environment variable TPM2TOOLS_AUTOFLUSH is set to yes or true 👑

🦋 TCTI Configuration 🦋

the TCTI — aka the "Transmission Interface" — is the communication mechanism with the TPM. you can swap TCTIs around so you can talk to TPMs across all kinds of different mediums. very main character energy of them honestly ✨

to control the TCTI, the tools respect this hierarchy:

  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 initialize a connection with the TPM. some tools allow for off-tpm options and thus support not using a TCTI. tools that don't support it will error when you try to use them without a TCTI connection. > this one 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 the <tcti-option-config> results in the default being used for that portion respectively 🎀

🌈 TCTI Defaults

when a TCTI isn't 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. so 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 is 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 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.

the 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 👑

💖 EXAMPLES 💖

Create an RSA Endorsement Key and make it persistent

tpm2_createek -P abc123 -w abc123 -c 0x81010001 -G rsa -u ek.pub

Create an ECC NIST_P384 Endorsement Key and make it persistent

tpm2_createek -G ecc384 -c 0x81010002

Create a transient Endorsement Key, flush it, and reload it.

typically, when using the TPM, the interactions occur through a resource manager, like tpm2-abrmd(8). however, when interacting with the TPM directly, this scenario is possible. the below example assumes direct TPM access not brokered by a resource manager. specifically we will use /dev/tpm0 🫶

tpm2_createek -c ek.ctx -G rsa -u ek.pub -Tdevice:/dev/tpm0

# Check that it is loaded in transient memory
tpm2_getcap handles-transient -Tdevice:/dev/tpm0
- 0x80000000

# Flush the handle
tpm2_flushcontext 0x80000000 -Tdevice:/dev/tpm0

# Note that it is flushed
tpm2_getcap handles-transient -Tdevice:/dev/tpm0
<null output>

# Reload it via loadexternal
tpm2_loadexternal -C o -u ek.pub -c ek.ctx -Tdevice:/dev/tpm0

# Check that it is re-loaded in transient memory
tpm2_getcap handles-transient -Tdevice:/dev/tpm0
- 0x80000000

⭐ 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 — that's where they live, bestie 🐛

🌸 HELP

See the Mailing List 📬

🎀 License

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

and that's the whole page, bestie!! this came to you straight from tpm2-tools, section tpm2_createek(1) of the manual — go forth and make your endorsement keys, you absolute icon 💅✨🦋

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