tpm2_loadexternal man page

tpm2_loadexternal(1) — Load an external object into the TPM.

Synopsis

tpm2_loadexternal [Options]

Description

tpm2_loadexternal(1) - This command loads an external object into the TPM, forgoing TPM protections. Ie, the key material is not protected by the parent object's seed. The command allows loading of just the public portion of an object or both the public and private portions of an object.

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.

Options

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:

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".

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:0x1122334455667788

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 the output of the raw PCR contents as returned by tpm2_pcrread(1).

PCR bank specifiers (common/pcr.md)

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

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

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.
  • ecc - Elliptical Curve, defaults to ecc256.
  • ecc192 - 192 bit ECC
  • ecc224 - 224 bit ECC
  • ecc256 - 256 bit ECC
  • ecc384 - 384 bit ECC
  • ecc521 - 521 bit ECC
  • rsa - Default RSA: rsa2048
  • rsa1024 - RSA with 1024 bit keysize.
  • rsa2048 - RSA with 2048 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

Multiple Option Scheme Specifiers

This scheme specifier is followed by a count (max size UINT16) then folloed 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.

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.

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.

The current known TCTIs are:

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:

Notes

Examples

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
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
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

Returns

Tools can return any of the following codes:

Bugs

Github Issues (https://github.com/tpm2-software/tpm2-tools/issues)

Help

See the Mailing List (https://lists.01.org/mailman/listinfo/tpm2)

Referenced By

tpm2_createek(1).

tpm2-tools General Commands Manual