tpm2_nvread - Man Page

tpm2_nvread [Options] [ARGUMENT]

tpm2_nvread(1) - Read the data stored in a Non-Volatile (NV)s index. The index can be specified as raw handle or an offset value to the nv handle range “TPM2_HR_NV_INDEX”.

• -C, --hierarchy=OBJECT:

  Specifies the hierarchy used to authorize. Supported options are:

  • o for TPM_RH_OWNER
  • p for TPM_RH_PLATFORM
  • <num> where a hierarchy handle or nv-index may be used.

  When -C isn’t explicitly passed the index handle will be used to authorize against the index. The index auth value is set via the -p option to tpm2_nvdefine(1).

• -o, --output=File:

  File to write data

• -P, --auth=AUTH:

  Specifies the authorization value for the hierarchy.

• -s, --size=NATURAL_NUMBER:

  Specifies the size of data to be read in bytes, starting from 0 if offset is not specified. If not specified, the size of the data as reported by the public portion of the index will be used.

• --offset=NATURAL_NUMBER:

  The offset within the NV index to start reading from.

• --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, unless rphash is also required.

• --rphash=File

  File path to record the hash of the response parameters. This is commonly termed as rpHash.

• -n, --name=File:

  The name of the NV index that must be provided when only calculating the cpHash without actually dispatching the command to the TPM.

• -S, --session=File:

  The session created using tpm2_startauthsession. This can be used to specify an auxiliary session for auditing and or encryption/decryption of the parameters.

• --print-yaml:

  Output the content of the NV index in a human readable format, useful for displaying the content of counter, bits and extend and pin indices. When this argument is provided size and offset is ignored.

• ARGUMENT the command line argument specifies the NV index or offset number.

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

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.d)

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)