Ubuntu Manpage: tpm2_create(1) - Create a child object.

NAME

       tpm2_create(1) - Create a child object.

SYNOPSIS

       tpm2_create [OPTIONS]

DESCRIPTION

       tpm2_create(1)  -  Create  a  child  object.   The object can either be a key or a sealing
       object.  A sealing object allows to seal user data to the TPM, with a maximum size of  128
       bytes.  Additionally it will load the created object if the -c is specified.

OPTIONS

These options for creating the TPM entity:

• -C, --parent-context=OBJECT:

The parent of the object to be created.

• -P, --parent-auth=AUTH:

The authorization value of the parent object specified with -C.

• -p, --key-auth=AUTH:

The authorization value for the created object.

• -g, --hash-algorithm=ALGORITHM:

The hash algorithm for generating the objects name. This is optional and defaults to
sha256 when not specified.

• -G, --key-algorithm=ALGORITHM:

The key algorithm associated with this object. It defaults to “rsa” if not specified.

• -a, --attributes=ATTRIBUTES:

The object attributes, optional. The default for created objects is:

When -i is specified for sealing, TPMA_OBJECT_SIGN_ENCRYPT and TPMA_OBJECT_DECRYPT are
removed from the default attribute set. The algorithm is set in a way where the the
object is only good for sealing and unsealing. I.e. one cannot use an object for
sealing and cryptography operations.

When -L is specified for adding policy based authorization information AND no string
password is specified, the attribute TPMA_OBJECT_USERWITHAUTH is cleared unless an
explicit choice is made by setting of the attribute with -a option. This prevents
creation of objects with inadvertent auth model where in user intended to enforce a
policy but inadvertently created an object with empty auth which can be used instead of
policy authorization.

• -i, --sealing-input=FILE or STDIN:

The data file to be sealed, optional. If file is -, read from stdin. When sealing data
only the TPM_ALG_KEYEDHASH algorithm with a NULL scheme is allowed. Thus, -G cannot be
specified.

• -L, --policy=FILE or HEX_STRING:

The input policy file or a hex string, optional.

• -u, --public=FILE:

The output file which contains the public portion of the created object, optional.

• -r, --private=FILE:

The output file which contains the sensitive portion of the object, optional. #
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:

• https://trustedcomputinggroup.org/wp-content/uploads/TPM-
Rev-2.0-Part-1-Architecture-01.38.pdf

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.

• -c, --key-context=FILE:

The output file which contains the key context, optional. The key context is analogous
to the context file produced by tpm2_load(1), however is generated via a
tpm2_createloaded(1) command. This option can be used to avoid the normal
tpm2_create(1) and tpm2_load(1) command sequences and do it all in one command,
atomically.

• --creation-data=FILE:

An optional file output that saves the creation data for certification.

• --template-data=FILE:

An optional file output that saves the key template data (TPM2B_PUBLIC) to be used in
tpm2_policytemplate.

• -t, --creation-ticket=FILE:

An optional file output that saves the creation ticket for certification.

• -d, --creation-hash=FILE:

An optional file output that saves the creation hash for certification.

• -q, --outside-info=HEX_STR_OR_FILE:

An optional hex string or path to add unique data to the creation data. Note that it
does not contribute in creating statistically unique object.

• -l, --pcr-list=PCR:

The list of PCR banks and selected PCRs’ ids for each bank to be included in the
creation data for certification.

• --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.

• --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. Multiple of these can be specified.
For example, you can have one session for auditing and another for
encryption/decryption of the parameters.

• -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.

• -o, --output=FILE:

The output file path, recording the public portion of the object.

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”.

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.

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.

       • -h,  --help=[man|no-man]:  Display the tools 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 if 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.  information 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:

• tabrmd - The resource manager, called tabrmd
(https://github.com/tpm2-software/tpm2-abrmd). 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.

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

   Setup
       In order to create an object, we must first create a primary key as it’s parent.

              tpm2_createprimary -c primary.ctx

   Create an Object
       This  will  create an object using all the default values and store the TPM sealed private
       and public portions to the paths specified via -u and -r respectively.  The tool  defaults
       to an RSA key.

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

   Seal Data to the TPM
       Outside  of  key  objects,  the  TPM allows for small amounts of user specified data to be
       sealed to the TPM.

              echo "my sealed data" > seal.dat
              tpm2_create -C primary.ctx -i seal.dat -u obj.pub -r obj.priv

   Create an EC Key Object and Load it to the TPM
       Normally, when creating an object, only the public and private portions of the object  are
       returned  and  the  caller  needs  to  use  tpm2_load(1)  to load those public and private
       portions to the  TPM  before  being  able  to  use  the  object.   However,  this  can  be
       accomplished  within this command as well, when supported by the TPM.  You can verify your
       TPM  supports  this   feature   by   checking   that   tpm2_getcap(1)   commands   returns
       TPM2_CC_CreateLoaded   in   the   command   set.    If   your   TPM   does   not   support
       TPM2_CC_CreateLoaded an unsuported command code error  will  be  returned.   If  it’s  not
       supported one must use tpm2_load(1).  See that manpage for details on its usage.

              tpm2_create -C primary.ctx -G ecc -u obj.pub -r obj.priv -c ecc.ctx

   Create an Object and get the public key as a PEM file
       This  will create an object using all the default values but also output the public key as
       a PEM file compatible with tools like OpenSSL and whatever supports PEM files.

              tpm2_create -C primary.ctx -u obj.pub -r obj.priv -f pem -o obj.pem

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

HELP

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