csu3_am335x/EVSE/GPL/tpm2-tools-5.1/man/man1/tpm2_getrandom.1

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.TH "tpm2_getrandom" "1" "" "tpm2\-tools" "General Commands Manual"
.hy
.SH NAME
.PP
\f[B]tpm2_getrandom\f[](1) \- Retrieves random bytes from the TPM.
.SH SYNOPSIS
.PP
\f[B]tpm2_getrandom\f[] [\f[I]OPTIONS\f[]] [\f[I]ARGUMENT\f[]]
.SH DESCRIPTION
.PP
\f[B]tpm2_getrandom\f[](1) \- Returns the next \f[I]SIZE\f[] octets from
the random number generator.
The \f[I]SIZE\f[] parameter is expected as the only argument to the
tool.
.PP
Note that the TPM specification recommends that TPM\[aq]s fix the number
of available entry to the maximum size of a hash algorithm output in
bytes.
.PP
Most TPMs do this, and thus the tool verifies that input size is bounded
by property \f[B]TPM2_PT_MAX_DIGEST\f[] and issues an error if it is too
large.
.PP
Output defaults to \f[I]stdout\f[] and binary format unless otherwise
specified with \f[B]\-o\f[] and \f[B]\-\-hex\f[] options respectively.
.SH OPTIONS
.IP \[bu] 2
\f[B]\-o\f[], \f[B]\-\-output\f[]=\f[I]FILE\f[]
.RS 2
.PP
Specifies the filename to output the raw bytes to.
Defaults to stdout as a hex string.
.RE
.IP \[bu] 2
\f[B]\-\-hex\f[]
.RS 2
.PP
Convert the output data to hex format without a leading "0x".
.RE
.IP \[bu] 2
\f[B]\-f\f[], \f[B]\-\-force\f[]
.RS 2
Override checking that the:
.IP \[bu] 2
Requested size is within the hash size limit of the TPM.
.IP \[bu] 2
Number of retrieved random bytes matches requested amount.
.RE
.IP \[bu] 2
\f[B]\-S\f[], \f[B]\-\-session\f[]=\f[I]FILE\f[]:
.RS 2
.PP
The session created using \f[B]tpm2_startauthsession\f[].
Multiple of these can be specified.
For example, you can have one session for auditing and another for
encryption of the parameters.
.RE
.IP \[bu] 2
\f[B]\-\-cphash\f[]=\f[I]FILE\f[]:
.RS 2
.PP
File path to record the hash of the command parameters.
This is commonly termed as cpHash.
NOTE: When this option is selected, in absence of rphash option, The
tool will not actually execute the command, it simply returns a cpHash.
.RE
.IP \[bu] 2
\f[B]\-\-rphash\f[]=\f[I]FILE\f[]:
.RS 2
.PP
File path to record the hash of the response parameters.
This is commonly termed as rpHash.
.RE
.IP \[bu] 2
\f[B]ARGUMENT\f[] the command line argument specifies the size of the
output.
.SS References
.SH COMMON OPTIONS
.PP
This collection of options are common to many programs and provide
information that many users may expect.
.IP \[bu] 2
\f[B]\-h\f[], \f[B]\-\-help=[man|no\-man]\f[]: 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.
.RS 2
.PP
To successfully use the manpages feature requires the manpages to be
installed or on \f[I]MANPATH\f[], See man(1) for more details.
.RE
.IP \[bu] 2
\f[B]\-v\f[], \f[B]\-\-version\f[]: Display version information for this
tool, supported tctis and exit.
.IP \[bu] 2
\f[B]\-V\f[], \f[B]\-\-verbose\f[]: Increase the information that the
tool prints to the console during its execution.
When using this option the file and line number are printed.
.IP \[bu] 2
\f[B]\-Q\f[], \f[B]\-\-quiet\f[]: Silence normal tool output to stdout.
.IP \[bu] 2
\f[B]\-Z\f[], \f[B]\-\-enable\-errata\f[]: 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.
.SH TCTI Configuration
.PP
The TCTI or "Transmission Interface" is the communication mechanism with
the TPM.
TCTIs can be changed for communication with TPMs across different
mediums.
.PP
To control the TCTI, the tools respect:
.IP "1." 3
The command line option \f[B]\-T\f[] or \f[B]\-\-tcti\f[]
.IP "2." 3
The environment variable: \f[I]TPM2TOOLS_TCTI\f[].
.PP
\f[B]Note:\f[] The command line option always overrides the environment
variable.
.PP
The current known TCTIs are:
.IP \[bu] 2
tabrmd \- The resource manager, called
tabrmd (https://github.com/tpm2-software/tpm2-abrmd).
Note that tabrmd and abrmd as a tcti name are synonymous.
.IP \[bu] 2
mssim \- Typically used for communicating to the TPM software simulator.
.IP \[bu] 2
device \- Used when talking directly to a TPM device file.
.IP \[bu] 2
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 \f[I]ANY\f[] options and \f[I]MUST BE\f[] presented as
the exact text of "none".
.PP
The arguments to either the command line option or the environment
variable are in the form:
.PP
\f[C]<tcti\-name>:<tcti\-option\-config>\f[]
.PP
Specifying an empty string for either the \f[C]<tcti\-name>\f[] or
\f[C]<tcti\-option\-config>\f[] results in the default being used for
that portion respectively.
.SS TCTI Defaults
.PP
When a TCTI is not specified, the default TCTI is searched for using
\f[I]dlopen(3)\f[] semantics.
The tools will search for \f[I]tabrmd\f[], \f[I]device\f[] and
\f[I]mssim\f[] TCTIs \f[B]IN THAT ORDER\f[] and \f[B]USE THE FIRST ONE
FOUND\f[].
You can query what TCTI will be chosen as the default by using the
\f[B]\-v\f[] option to print the version information.
The "default\-tcti" key\-value pair will indicate which of the
aforementioned TCTIs is the default.
.SS Custom TCTIs
.PP
Any TCTI that implements the dynamic TCTI interface can be loaded.
The tools internally use \f[I]dlopen(3)\f[], and the raw
\f[I]tcti\-name\f[] value is used for the lookup.
Thus, this could be a path to the shared library, or a library name as
understood by \f[I]dlopen(3)\f[] semantics.
.SH TCTI OPTIONS
.PP
This collection of options are used to configure the various known TCTI
modules available:
.IP \[bu] 2
\f[B]device\f[]: For the device TCTI, the TPM character device file for
use by the device TCTI can be specified.
The default is \f[I]/dev/tpm0\f[].
.RS 2
.PP
Example: \f[B]\-T device:/dev/tpm0\f[] or \f[B]export
\f[I]TPM2TOOLS_TCTI\f[]="device:/dev/tpm0"\f[]
.RE
.IP \[bu] 2
\f[B]mssim\f[]: 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.
.RS 2
.PP
Example: \f[B]\-T mssim:host=localhost,port=2321\f[] or \f[B]export
\f[I]TPM2TOOLS_TCTI\f[]="mssim:host=localhost,port=2321"\f[]
.RE
.IP \[bu] 2
\f[B]abrmd\f[]: For the abrmd TCTI, the configuration string format is a
series of simple key value pairs separated by a \[aq],\[aq] character.
Each key and value string are separated by a \[aq]=\[aq] character.
.RS 2
.IP \[bu] 2
TCTI abrmd supports two keys:
.RS 2
.IP "1." 3
\[aq]bus_name\[aq] : The name of the tabrmd service on the bus (a
string).
.IP "2." 3
\[aq]bus_type\[aq] : The type of the dbus instance (a string) limited to
\[aq]session\[aq] and \[aq]system\[aq].
.RE
.PP
Specify the tabrmd tcti name and a config string of
\f[C]bus_name=com.example.FooBar\f[]:
.PP
\f[C]\\\-\-tcti=tabrmd:bus_name=com.example.FooBar\f[]
.PP
Specify the default (abrmd) tcti and a config string of
\f[C]bus_type=session\f[]:
.PP
\f[C]\\\-\-tcti:bus_type=session\f[]
.PP
\f[B]NOTE\f[]: abrmd and tabrmd are synonymous.
the various known TCTI modules.
.RE
.SH EXAMPLES
.SS Generate a random 20 bytes and output the binary data to a file
.IP
.nf
\f[C]
tpm2_getrandom\ \-o\ random.out\ 20
\f[]
.fi
.SS Generate a random 8 bytes and output the hex formatted data to
stdout
.IP
.nf
\f[C]
tpm2_getrandom\ 8
\f[]
.fi
.SH Returns
.PP
Tools can return any of the following codes:
.IP \[bu] 2
0 \- Success.
.IP \[bu] 2
1 \- General non\-specific error.
.IP \[bu] 2
2 \- Options handling error.
.IP \[bu] 2
3 \- Authentication error.
.IP \[bu] 2
4 \- TCTI related error.
.IP \[bu] 2
5 \- Non supported scheme.
Applicable to tpm2_testparams.
.SH BUGS
.PP
Github Issues (https://github.com/tpm2-software/tpm2-tools/issues)
.SH HELP
.PP
See the Mailing List (https://lists.01.org/mailman/listinfo/tpm2)