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 bounded 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 stdout 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.

       • 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 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

   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.01.org/mailman/listinfo/tpm2)