tpm2_create - Man Page

tpm2_create [Options]

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.

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:

  TPMA_OBJECT_SIGN_ENCRYPT|TPMA_OBJECT_DECRYPT|TPMA_OBJECT_FIXEDTPM|  TPMA_OBJECT_FIXEDPARENT|TPMA_OBJECT_SENSITIVEDATAORIGIN|  TPMA_OBJECT_USERWITHAUTH

  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.

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 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”.

foobar
str:foobar

hex:1122334455667788

# 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

session:session.ctx

session:session.ctx+mypassword

session:session.ctx+hex:11223344

pcr:sha256:0,1,2,3

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.

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.

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.
• -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 is set to yes or true. information many users may expect.

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.

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.

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.

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

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

tpm2_changeauth(1), tpm2_createak(1), tpm2_duplicate(1), tpm2_import(1), tpm2_loadexternal(1).