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tpm2_getrandom(1)	    General Commands Manual	     tpm2_getrandom(1)

NAME
       tpm2_getrandom(1) - Retrieves random bytes from the TPM.

SYNOPSIS
       tpm2_getrandom [OPTIONS]	[ARGUMENT]

DESCRIPTION
       tpm2_getrandom(1) - Returns the next SIZE octets	from the random	number
       generator.   The	SIZE parameter is expected as the only argument	to the
       tool.

       Note that the TPM specification recommends that TPM's fix the number of
       available entry to the maximum size  of	a  hash	 algorithm  output  in
       bytes.

       Most TPMs do this, and thus the tool verifies that input	size is	bound-
       ed  by  property	 TPM2_PT_MAX_DIGEST  and  issues an error if it	is too
       large.

       Output defaults to stdout and binary format unless otherwise  specified
       with -o and -hex	options	respectively.

OPTIONS
       • -o, --output=FILE

	 Specifies  the	filename to output the raw bytes to.  Defaults to std-
	 out as	a hex string.

       • --hex

	 Convert the output data to hex	format without a leading "0x".

       • -f, --force

	 Override checking that	the:

	 • Requested size is within the	hash size limit	of the TPM.

	 • Number of retrieved random bytes matches requested amount.

       • -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 of the parameters.

       • --cphash=FILE:

	 File path to record the hash of the command parameters.  This is com-
	 monly	termed	as cpHash.  NOTE: When this option is selected,	in ab-
	 sence of rphash option, The tool will not actually execute  the  com-
	 mand, it simply returns a cpHash.

       • --rphash=FILE:

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

       • ARGUMENT the command line argument specifies the size of the output.

   References
COMMON OPTIONS
       This collection of options are common to	many programs and provide  in-
       formation 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  re-
	 quested,  the	tool  will  provide errors from	man on stderr.	If the
	 "no-man" option if specified, or the manpager fails,  the  short  op-
	 tions 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.   in-
	 formation 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 vari-
       able.

       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  simula-
	 tor.

       • 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  respective-
       ly.

   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	 indi-
       cate 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 li-
       brary 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="de-
	 vice:/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_TC-
	 TI="mssim:host=localhost,port=2321"

       • abrmd:	 For  the abrmd	TCTI, the configuration	string format is a se-
	 ries 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.ex-
	 ample.FooBar:

		\--tcti=tabrmd:bus_name=com.example.FooBar

	 Specify the default (abrmd) tcti and a	config string of bus_type=ses-
	 sion:

		\--tcti:bus_type=session

	 NOTE:	abrmd  and tabrmd are synonymous.  the various known TCTI mod-
	 ules.

EXAMPLES
   Generate a random 20	bytes and output the binary data to a file
	      tpm2_getrandom -o	random.out 20

   Generate a random 8 bytes and output	the hex	formatted data to stdout
	      tpm2_getrandom 8

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/listin-
       fo/tpm2)

tpm2-tools						     tpm2_getrandom(1)

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