tpm2_import(1)

📦
version 5.8 · 10 versions
, in arch rolling

💖 NAME 💖

okay bestie, this is the tpm2_import(1) page from the General Commands Manual, and it is literally about importing an external key into the TPM as a TPM-managed key object. 💅 No cap, that is the whole vibe.

✨ SYNOPSIS ✨

tpm2_import [OPTIONS]

🌸 DESCRIPTION 🌸

tpm2_import(1) imports an externally generated key as a TPM-managed key object. It requires that the parent key object be a RSA key. It can also import a TPM-managed key object created by the tpm2_duplicate tool. 🦋

💅 OPTIONS 💅

These options control the key importation process: ✨

  • -G, --key-algorithm=ALGORITHM — The algorithm used by the key to be imported. Supports:
    • aes — AES 128, 192 or 256 key.
    • rsa — RSA 1024, 2048, 3072, or 4096 key.
    • ecc — ECC NIST P192, P224, P256, P384 or P521 public and private key.
    • hmac — HMAC key.
  • -g, --hash-algorithm=ALGORITHM — The hash algorithm for generating the object's name. This is optional and defaults to sha256 when not specified. Algorithms should follow the “formatting standards”, see section “Algorithm Specifiers”. Also, see section “Supported Hash Algorithms” for a list of supported hash algorithms. 🫶
  • -i, --input=FILE — Specifies the filename of the key to be imported. For AES keys, this file is the raw key bytes. For asymmetric keys in PEM or DER format. A typical file is generated with openssl genrsa. 🔑
  • -C, --parent-context=OBJECT — The parent key object. 👑
  • -U, --parent-public=FILE — Optional. Specifies the parent key public data file input. This can be read with tpm2_readpublic(1) tool. If not specified, the tool invokes a tpm2_readpublic on the parent object. 🌈
  • -k, --encryption-key=FILE — Optional. Specifies the file containing the symmetric algorithm key that was used for the inner wrapper. If the file is specified the tool assumes the algorithm is AES 128 in CFB mode otherwise none. 🔐
  • -r, --private=FILE — Specifies the file path required to save the encrypted private portion of the object imported as key. 🫶

When importing a duplicated object this option specifies the file containing the private portion of the object to be imported.

Protection Details — Objects that can move outside of TPM need to be protected (confidentiality and integrity). For instance, transient objects require that TPM protected data (key or seal material) be stored outside of the TPM. This is seen in tools like tpm2_create(1), where the -r option outputs this protected data. This blob contains the sensitive portions of the object. The sensitive portions of the object are protected by the parent object, using the parent’s symmetric encryption details to encrypt the sensitive data and HMAC it. 💀

In-depth details can be found in sections 23 of:

Notably Figure 20, is relevant, even though it’s specifically referring to duplication blobs, the process is identical. 🧚

If the output is from tpm2_duplicate(1), the output will be slightly different, as described fully in section 23.

  • -u, --public=FILE — Specifies the file path required to save the public portion of the object imported as key. 🌟

When importing a duplicated object this option specifies the file containing the public portion of the object to be imported.

  • -a, --attributes=ATTRIBUTES — The object attributes, optional. 🎀
  • -P, --parent-auth=AUTH — The authorization value for using the parent key specified with -C. 🔑
  • -p, --key-auth=AUTH — The authorization value for the imported key, optional. 🔒
  • -L, --policy=POLICY or HEX_STRING — The policy file or policy hex string used for authorization to the object. 📜
  • -s, --seed=FILE — Specifies the file containing the encrypted seed of the duplicated object. 🌱

In order to perform an “unencrypted import” a seed file with the content 0x0000 needs to be provided (e.g. printf “0000” | xxd -r -p >seed.file).

  • --passin=OSSL_PEM_FILE_PASSWORD — An optional password for an Open SSL (OSSL) provided input file. It mirrors the -passin option of OSSL and is known to support the pass, file, env, fd and plain password formats of openssl. (see man(1) openssl) for more. 🪄
  • --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. ⚡

📚 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 can be loaded as a number it will be treated as a handle, e.g. 0x81010013 and used directly as _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 its 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 hexadecimal 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 by 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”.

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 🧬

Okay so this is where it gets spicy — options that take algorithms? They support “nice-names”. Yes bestie, actual nice names, no hex soup required 💅

There are two big algorithm-specification string classes: simple and complex. And like, only certain algorithms get accepted by the TPM, based on usage and conditions — so don't come for the TPM when it says no 🙈

🌸 Simple specifiers

These are strings with no extra specification data. When you're creating objects, any part of an object you didn't specify just gets assumed to defaults. The list of known “Simple Specifiers” is, like, right 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

So when objects get specified for creation by the TPM, they've got numerous algorithms to populate in the public data — think type, scheme, asymmetric details, key size, etc. The general format for specifying all that is literally:

<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 you specified and the type of object being created. Slay, defaults.

  • 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 up is an optional field — you can literally just skip it, no pressure 🫶

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. Chaotic, I know.

🌈 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 object's 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.

👑 Object Attributes 👑

Object Attributes are what control various properties of created objects. When specified as an option, you can use either the raw bitfield mask or the “nice-names”. The values live in Table 31 Part 2 of the TPM2.0 specification, which is right here:

https://trustedcomputinggroup.org/wp-content/uploads/TPM-Rev-2.0-Part-2-Structures-01.38.pdf

Nice names are calculated by taking the name field of table 31 and removing the prefix TPMA_OBJECT_ and lowercasing the result. So like, TPMA_OBJECT_FIXEDTPM becomes fixedtpm. Character development fr fr. Nice names can be joined using the bitwise or | symbol.

For instance, to set the fields TPMA_OBJECT_FIXEDTPM, TPMA_OBJECT_NODA, and TPMA_OBJECT_SIGN_ENCRYPT, the argument would be:

fixedtpm|noda|sign

...specifying the object attributes ATTRIBUTES.

🌟 COMMON OPTIONS 🌟

This collection of options are common to many programs and provide information that many users may expect. Basically the group-chat essentials 💖

  • -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. 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 set to yes or true.
Not me pointing out that the manpage really does say “is is” in that last one 😭 keeping it exactly as written bestie, information many users may expect.

🔥 TCTI Configuration 🔥

The TCTI, aka “Transmission Interface”, is the communication mechanism with the TPM. TCTIs can be changed for communication with TPMs across different mediums. So it's like the aux cord but for your TPM, iconic.

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. No cap.

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. Very main character of it.

💫 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 🌸

Okay bestie, real talk — before you can import anything, you need a parent key. That's just how this works, no cap.

tpm2_createprimary -Grsa2048:aes128cfb -C o -c parent.ctx

Then you make your key and import it. And hey — if you already have a key lying around, just use that one and skip the whole creating-it step. We love a shortcut. 💅

🍓 Import an AES 128 key

dd if=/dev/urandom of=sym.key bs=1 count=16

tpm2_import -C parent.ctx -G aes -i sym.key -u key.pub -r key.priv

Straight up random bytes, 16 of them, and boom — symmetric key imported. Iconic.

🦋 Import an RSA key

openssl genrsa -out private.pem 2048

tpm2_import -C parent.ctx -G rsa -i private.pem -u key.pub -r key.priv

2048 bits of RSA goodness, generated by openssl and handed off to the TPM. Slay.

✨ Import an ECC key

openssl ecparam -name prime256v1 -genkey -noout -out private.ecc.pem

tpm2_import -C parent.ctx -G ecc -i private.ecc.pem -u key.pub -r key.priv

prime256v1, no output noise, clean file. The way that ECC just works — obsessed.

🎀 Import a duplicated key

tpm2_import -C parent.ctx -i key.dup -u key.pub -r key.priv -L policy.dat

Notice there's no -G here — this one's already a duplicated key, and you're passing the policy with -L policy.dat. Main character energy, honestly. 👑

💀 LIMITATIONS 💀

  • The TPM requires that the name algorithm of the child be smaller than the parent.
That's it. That's the limitation, bestie. Not me having to shrink my child just to fit inside my parent 😭 — but fr fr, if the name algorithm isn't smaller, it's not gonna fly. Plan accordingly.

🫶 Returns 🫶

Tools can return any of the following codes, so like, same energy:

  • 0 — Success. 🎉
  • 1 — General non-specific error. 🙈
  • 2 — Options handling error.
  • 3 — Authentication error. (wrong vibes, wrong creds)
  • 4 — TCTI related error.
  • 5 — Non supported scheme. Applicable to tpm2_testparams.

🐛 BUGS 🐛

Github Issues

Like, actual bugs, not the fun kind. If something's busted, Github Issues is where it goes. 🐞

🌈 HELP 🌈

See the Mailing List

Need a human? The Mailing List is right there. Go say hi. 🫶

👑 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 — you made it to the end! 🌟 This little masterpiece is from tpm2-tools, and you're reading the tpm2_import(1) page, dated whenever that footer says. Go forth and import responsibly. Periodt. 💖✨🎀

📦 where this page comes from