tpm2_loadexternal(1)

📦
version 5.8 · 10 versions
, in arch rolling

💖 NAME 💖

bestie, this is the General Commands Manual page for tpm2_loadexternal(1) — and its whole main character energy is: Load an external object into the TPM. 🌸

⚡ SYNOPSIS ⚡

tpm2_loadexternal [OPTIONS]

✨ DESCRIPTION ✨

okay so tpm2_loadexternal(1) loads an external object into the TPM, literally forgoing TPM protections — i.e. the key material is not protected by the parent object’s seed. 🫶 It can also be used to load TSS2 Private Keys in pem format. The command allows loading of just the public portion of an object, or both the public and private portions of an object. For TSS2 Private Keys, only the public portion of the key is loaded.

The tool outputs the name of the loaded object in a YAML dictionary format with the key name, where the value for that key is the name of the object in hex format, for example:

name: 000bac25cb8743111c8e1f52f2ee7279d05d3902a18dd1af694db5d1afa7adf1c8b3

It also saves a context file for future interactions with the object. periodt. 💅

🎀 OPTIONS 🎀

  • -C, --hierarchy=OBJECT — the hierarchy to use for the ticket, optional. Defaults to n, null. Supported options are:
    • o for the owner hierarchy.
    • p for the platform hierarchy.
    • e for the endorsement hierarchy.
    • n for the null hierarchy.
  • -G, --key-algorithm=ALGORITHM — the algorithm used by the key to be imported. Supports:
    • aes — AES 128,192 or 256 key.
    • rsa — RSA 1024 or 2048 key.
    • ecc — ECC NIST P192, P224, P256, P384 or P521 public and private key.
  • -u, --public=FILE — the public portion of the object; this can be one of the following file formats:
    • TSS — the TSS/TPM format. For example from option -u of command tpm2_create(1).
    • RSA — OSSL PEM formats. For example public.pem from the command openssl rsa -in private.pem -out public.pem -pubout
    • ECC — OSSL PEM formats. For example public.pem from the command openssl ec -in private.ecc.pem -out public.ecc.pem -pubout
  • -r, --private=FILE — the sensitive portion of the object, optional. If one wishes to use the private portion of a key, this must be specified. Like option -u, this command takes files in the following format:
    • RSA — OSSL PEM formats. For example private.pem from the command openssl genrsa -out private.pem 2048 Since an RSA public key can be derived from the private PEM file, there’s no need to specify -u for the public portion.
    • TSS2 PrivateKey PEM formats.
Note: The private portion does not respect TSS formats as it’s impossible to get a TPM2B_SENSITIVE output from a previous command. They are always protected by the TPM as TPM2B_PRIVATE blobs.
  • -p, --auth=AUTH — the authorization value for the key, optional.
  • -L, --policy=FILE or HEX_STRING — the input policy file or hex string, optional. A file or hex string containing the hash of a policy derived from tpm2_createpolicy or another policy digest generating source.
  • -g, --hash-algorithm=ALGORITHM — the hash algorithm for generating the object’s name. This is optional and defaults to sha256 when not specified. However, load external supports having a null name algorithm. In this case, no cryptographic binding checks between the public and private portions are performed.
  • -a, --attributes=ATTRIBUTES — the object attributes, optional. The default for created objects is: TPMA_OBJECT_SIGN_ENCRYPT|TPMA_OBJECT_DECRYPT. Optionally, if -p is specified or no -p or -L is specified then TPMA_OBJECT_USERWITHAUTH is added to the default attribute set.
Note: If specifying attributes, the TPM will reject certain attributes like TPMA_OBJECT_FIXEDTPM, as those guarantees cannot be made.
  • -c, --key-context=FILE — the file name to save the object context, required.
  • -n, --name=FILE — an optional file to save the object name, which is in a binary hash format. The size of the hash is based on the name algorithm or the -g option.
  • --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.
  • -e, --rsa_exponent_zero — set the exponent of a public RSA key to zero, to enable compatibility in the computation of the key name if the TPM key is generated with exponent zero.

🌈 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 ✨

Okay bestie, options that take algorithms support “nice-names” 💅 — and 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. Periodt.

🧸 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, iykyk.

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, no stress 💖.

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 one here 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.

  • rsaes

Symmetric Details Specifiers

This field is optional, and defaults based on the type of object being created and its 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

And the page also has this stray little crumb right after that example: cryptographic algorithms ALGORITHM. — keeping it because every detail matters 🫡.

🏷️ Object Attributes

Object Attributes are used to control various properties of created objects. When specified as an option, either the raw bitfield mask or “nice-names” may be used. The values can be found in Table 31 Part 2 of the TPM2.0 specification, which can be found 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. Thus, TPMA_OBJECT_FIXEDTPM becomes fixedtpm. 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. Group-chat classics, honestly.

  • -h, --help=[man|no-man] — Display the tool’s 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 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. And yes, the bullet also trails with information many users may expect. — manpage confetti, preserved 🎀.

🔌 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. 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.

🛠️ 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. Very main character energy for a shared library, honestly.

🎛️ 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. And that’s the tea on the various known TCTI modules 🫶.

📝 NOTES

  • If the hierarchy is null or the name hashing algorithm is null, tickets produced using the object will be NULL.
  • If the private portion of an object is specified, the hierarchy must be null or the TPM will reject loading it.

✨ EXAMPLES ✨

These are the actual little recipes, bestie — copy them, run them, watch your context files appear like magic 🪄

🌸 Load a TPM generated public key into the owner hierarchy

tpm2_createprimary -c primary.ctx

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

tpm2_loadexternal -C o -u pub.dat -c pub.ctx

and it hands you back the name, no cap:

name: 000b9be4d7c6193a57e1bfc86a42a6b03856a91d2f9e77c6cbdb796a783d52d4b3b9

🦋 Load an RSA public key into the owner hierarchy

openssl genrsa -out private.pem 2048

openssl rsa -in private.pem -out public.pem -outform PEM -pubout

tpm2_loadexternal -C o -Grsa -u public.pem -c key.ctx

output era 💅

name: 000b7b91d304d16995d42792b57d0fb25df7abe5fdd8afe9950730e00dc5b934ddbc

🎀 Load an RSA key-pair into the null hierarchy

openssl genrsa -out private.pem 2048

tpm2_loadexternal -C n -Grsa -r private.pem -c key.ctx
name: 000b635ea220b6c62ec1d02343859dd203c8ac5dad82ebc5b124e407d2502f88691f

🍓 Load an AES key into the null hierarchy

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

tpm2_loadexternal -C n -Gaes -r sym.key -c key.ctx
name: 000bfc4d8dd7e4f921bcc9dca4b04f49564243cd9def129a3740002bfd4b9e966d34

🧚 Load TSS2 Private Key into the null hierarchy

tpm2_loadexternal -r tss_privkey.pem -c tss_privkey.ctx
name: 000bc5a216702aca9ba226af1214c50dc4dc33ce6269677aa581ea6d9eec7f27000d

💀 Returns

Tools can return any of the following codes, so like… vibe check your exit status, okay? 👑

  • 0 — Success. slay, it worked 🎉
  • 1 — General non-specific error. the vague one 😭
  • 2 — Options handling error. you typed a flag wrong bestie
  • 3 — Authentication error. wrong password energy 🔒
  • 4 — TCTI related error. the TPM talking thing got confused
  • 5 — Non supported scheme. Applicable to tpm2_testparams.

🐛 BUGS

Github Issues — that's literally where the bugs live, go yell there (nicely pls) 🫶

🌈 HELP

See the Mailing List — real ones ask questions in public, iykyk 💜

⭐ License

This work is licensed under the Creative Commons Attribution 4.0 International License (CC BY 4.0). iconic of them honestly 🎀

and that's the whole page bestie 💖 source is tpm2-tools, and this gorgeous thing is tpm2_loadexternal(1) — go externalize those keys, you absolute main character 👑✨

📦 where this page comes from