1tpm2_getrandom(1) General Commands Manual tpm2_getrandom(1)
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6 tpm2_getrandom(1) - Retrieves random bytes from the TPM.
7
9 tpm2_getrandom [OPTIONS] [ARGUMENT]
10
12 tpm2_getrandom(1) - Returns the next SIZE octets from the random number
13 generator. The SIZE parameter is expected as the only argument to the
14 tool.
15 Note that the TPM specification recommends that TPM’s fix the number of
17 available entry to the maximum size of a hash algorithm output in
18 bytes.
19 Most TPMs do this, and thus the tool verifies that input size is bound‐
21 ed by property TPM2_PT_MAX_DIGEST and issues an error if it is too
22 large.
23 Output defaults to stdout and binary format unless otherwise specified
25 with -o and –hex options respectively.
26
28 • -o, --output=FILE
29 Specifies the filename to output the raw bytes to. Defaults to std‐
31 out as a hex string.
32 • --hex
34 Convert the output data to hex format without a leading “0x”.
36 • -f, --force
38 Override checking that the:
39 • Requested size is within the hash size limit of the TPM.
41 • Number of retrieved random bytes matches requested amount.
43 • -S, --session=FILE:
45 The session created using tpm2_startauthsession. Multiple of these
47 can be specified. For example, you can have one session for auditing
48 and another for encryption of the parameters.
49 • --cphash=FILE:
51 File path to record the hash of the command parameters. This is com‐
53 monly termed as cpHash. NOTE: When this option is selected, in ab‐
54 sence of rphash option, The tool will not actually execute the com‐
55 mand, it simply returns a cpHash.
56 • --rphash=FILE:
58 File path to record the hash of the response parameters. This is
60 commonly termed as rpHash.
61 • ARGUMENT the command line argument specifies the size of the output.
63 References
66 This collection of options are common to many programs and provide in‐
67 formation that many users may expect.
68 • -h, --help=[man|no-man]: Display the tools manpage. By default, it
70 attempts to invoke the manpager for the tool, however, on failure
71 will output a short tool summary. This is the same behavior if the
72 “man” option argument is specified, however if explicit “man” is re‐
73 quested, the tool will provide errors from man on stderr. If the
74 “no-man” option if specified, or the manpager fails, the short op‐
75 tions will be output to stdout.
76 To successfully use the manpages feature requires the manpages to be
78 installed or on MANPATH, See man(1) for more details.
79 • -v, --version: Display version information for this tool, supported
81 tctis and exit.
82 • -V, --verbose: Increase the information that the tool prints to the
84 console during its execution. When using this option the file and
85 line number are printed.
86 • -Q, --quiet: Silence normal tool output to stdout.
88 • -Z, --enable-errata: Enable the application of errata fixups. Useful
90 if an errata fixup needs to be applied to commands sent to the TPM.
91 Defining the environment TPM2TOOLS_ENABLE_ERRATA is equivalent. in‐
92 formation many users may expect.
93
95 The TCTI or “Transmission Interface” is the communication mechanism
96 with the TPM. TCTIs can be changed for communication with TPMs across
97 different mediums.
98 To control the TCTI, the tools respect:
100 1. The command line option -T or --tcti
102 2. The environment variable: TPM2TOOLS_TCTI.
104 Note: The command line option always overrides the environment vari‐
106 able.
107 The current known TCTIs are:
109 • tabrmd - The resource manager, called tabrmd
111 (https://github.com/tpm2-software/tpm2-abrmd). Note that tabrmd and
112 abrmd as a tcti name are synonymous.
113 • mssim - Typically used for communicating to the TPM software simula‐
115 tor.
116 • device - Used when talking directly to a TPM device file.
118 • none - Do not initalize a connection with the TPM. Some tools allow
120 for off-tpm options and thus support not using a TCTI. Tools that do
121 not support it will error when attempted to be used without a TCTI
122 connection. Does not support ANY options and MUST BE presented as
123 the exact text of “none”.
124 The arguments to either the command line option or the environment
126 variable are in the form:
127 <tcti-name>:<tcti-option-config>
129 Specifying an empty string for either the <tcti-name> or <tcti-op‐
131 tion-config> results in the default being used for that portion respec‐
132 tively.
133 TCTI Defaults
135 When a TCTI is not specified, the default TCTI is searched for using
136 dlopen(3) semantics. The tools will search for tabrmd, device and
137 mssim TCTIs IN THAT ORDER and USE THE FIRST ONE FOUND. You can query
138 what TCTI will be chosen as the default by using the -v option to print
139 the version information. The “default-tcti” key-value pair will indi‐
140 cate which of the aforementioned TCTIs is the default.
141 Custom TCTIs
143 Any TCTI that implements the dynamic TCTI interface can be loaded. The
144 tools internally use dlopen(3), and the raw tcti-name value is used for
145 the lookup. Thus, this could be a path to the shared library, or a li‐
146 brary name as understood by dlopen(3) semantics.
147
149 This collection of options are used to configure the various known TCTI
150 modules available:
151 • device: For the device TCTI, the TPM character device file for use by
153 the device TCTI can be specified. The default is /dev/tpm0.
154 Example: -T device:/dev/tpm0 or export TPM2TOOLS_TCTI=“de‐
156 vice:/dev/tpm0”
157 • mssim: For the mssim TCTI, the domain name or IP address and port
159 number used by the simulator can be specified. The default are
160 127.0.0.1 and 2321.
161 Example: -T mssim:host=localhost,port=2321 or export TPM2TOOLS_TC‐
163 TI=“mssim:host=localhost,port=2321”
164 • abrmd: For the abrmd TCTI, the configuration string format is a se‐
166 ries of simple key value pairs separated by a `,' character. Each
167 key and value string are separated by a `=' character.
168 • TCTI abrmd supports two keys:
170 1. `bus_name' : The name of the tabrmd service on the bus (a
172 string).
173 2. `bus_type' : The type of the dbus instance (a string) limited to
175 `session' and `system'.
176 Specify the tabrmd tcti name and a config string of bus_name=com.ex‐
178 ample.FooBar:
179 \--tcti=tabrmd:bus_name=com.example.FooBar
181 Specify the default (abrmd) tcti and a config string of bus_type=ses‐
183 sion:
184 \--tcti:bus_type=session
186 NOTE: abrmd and tabrmd are synonymous. the various known TCTI mod‐
188 ules.
189
191 Generate a random 20 bytes and output the binary data to a file
192 tpm2_getrandom -o random.out 20
193 Generate a random 8 bytes and output the hex formatted data to stdout
195 tpm2_getrandom 8
196
198 Tools can return any of the following codes:
199 • 0 - Success.
201 • 1 - General non-specific error.
203 • 2 - Options handling error.
205 • 3 - Authentication error.
207 • 4 - TCTI related error.
209 • 5 - Non supported scheme. Applicable to tpm2_testparams.
211
213 Github Issues (https://github.com/tpm2-software/tpm2-tools/issues)
214
216 See the Mailing List (https://lists.linuxfoundation.org/mailman/listin‐
217 fo/tpm2)
218tpm2-tools tpm2_getrandom(1)