1tpm2_nvread(1) General Commands Manual tpm2_nvread(1)
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6 tpm2_nvread(1) - Read the data stored in a Non-Volatile (NV)s index.
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9 tpm2_nvread [OPTIONS] [ARGUMENT]
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12 tpm2_nvread(1) - Read the data stored in a Non-Volatile (NV)s index.
13 The index can be specified as raw handle or an offset value to the nv
14 handle range “TPM2_HR_NV_INDEX”.
15
17 • -C, --hierarchy=OBJECT:
18 Specifies the hierarchy used to authorize. Supported options are:
19 • o for TPM_RH_OWNER
21 • p for TPM_RH_PLATFORM
23 • <num> where a hierarchy handle or nv-index may be used.
25 When -C isn’t explicitly passed the index handle will be used to au‐
27 thorize against the index. The index auth value is set via the -p
28 option to tpm2_nvdefine(1).
29 • -o, --output=FILE:
31 File to write data
33 • -P, --auth=AUTH:
35 Specifies the authorization value for the hierarchy.
37 • -s, --size=NATURAL_NUMBER:
39 Specifies the size of data to be read in bytes, starting from 0 if
41 offset is not specified. If not specified, the size of the data as
42 reported by the public portion of the index will be used.
43 • --offset=NATURAL_NUMBER:
45 The offset within the NV index to start reading from.
47 • --cphash=FILE
49 File path to record the hash of the command parameters. This is com‐
51 monly termed as cpHash. NOTE: When this option is selected, The tool
52 will not actually execute the command, it simply returns a cpHash,
53 unless rphash is also required.
54 • --rphash=FILE
56 File path to record the hash of the response parameters. This is
58 commonly termed as rpHash.
59 • -n, --name=FILE:
61 The name of the NV index that must be provided when only calculating
63 the cpHash without actually dispatching the command to the TPM.
64 • -S, --session=FILE:
66 The session created using tpm2_startauthsession. This can be used to
68 specify an auxiliary session for auditing and or encryption/decryp‐
69 tion of the parameters.
70 • --print-yaml:
72 Output the content of the NV index in a human readable format, useful
74 for displaying the content of counter, bits and extend and pin in‐
75 dices. When this argument is provided size and offset is ignored.
76 • ARGUMENT the command line argument specifies the NV index or offset
78 number.
79 References
82 The type of a context object, whether it is a handle or file name, is
83 determined according to the following logic in-order:
84 • If the argument is a file path, then the file is loaded as a restored
86 TPM transient object.
87 • If the argument is a prefix match on one of:
89 • owner: the owner hierarchy
91 • platform: the platform hierarchy
93 • endorsement: the endorsement hierarchy
95 • lockout: the lockout control persistent object
97 • If the argument argument can be loaded as a number it will be treat
99 as a handle, e.g. 0x81010013 and used directly._OBJECT_.
100
102 Authorization for use of an object in TPM2.0 can come in 3 different
103 forms: 1. Password 2. HMAC 3. Sessions
104 NOTE: “Authorizations default to the EMPTY PASSWORD when not speci‐
106 fied”.
107 Passwords
109 Passwords are interpreted in the following forms below using prefix
110 identifiers.
111 Note: By default passwords are assumed to be in the string form when
113 they do not have a prefix.
114 String
116 A string password, specified by prefix “str:” or it’s absence (raw
117 string without prefix) is not interpreted, and is directly used for au‐
118 thorization.
119 Examples
121 foobar
122 str:foobar
123 Hex-string
125 A hex-string password, specified by prefix “hex:” is converted from a
126 hexidecimal form into a byte array form, thus allowing passwords with
127 non-printable and/or terminal un-friendly characters.
128 Example
130 hex:1122334455667788
131 File
133 A file based password, specified be prefix “file:” should be the path
134 of a file containing the password to be read by the tool or a “-” to
135 use stdin. Storing passwords in files prevents information leakage,
136 passwords passed as options can be read from the process list or common
137 shell history features.
138 Examples
140 # to use stdin and be prompted
141 file:-
142 # to use a file from a path
144 file:path/to/password/file
145 # to echo a password via stdin:
147 echo foobar | tpm2_tool -p file:-
148 # to use a bash here-string via stdin:
150 tpm2_tool -p file:- <<< foobar
152 Sessions
154 When using a policy session to authorize the use of an object, prefix
155 the option argument with the session keyword. Then indicate a path to
156 a session file that was created with tpm2_startauthsession(1). Option‐
157 ally, if the session requires an auth value to be sent with the session
158 handle (eg policy password), then append a + and a string as described
159 in the Passwords section.
160 Examples
162 To use a session context file called session.ctx.
163 session:session.ctx
165 To use a session context file called session.ctx AND send the authvalue
167 mypassword.
168 session:session.ctx+mypassword
170 To use a session context file called session.ctx AND send the HEX auth‐
172 value 0x11223344.
173 session:session.ctx+hex:11223344
175 PCR Authorizations
177 You can satisfy a PCR policy using the “pcr:” prefix and the PCR mini‐
178 language. The PCR minilanguage is as follows:
179 <pcr-spec>=<raw-pcr-file>
180 The PCR spec is documented in in the section “PCR bank specifiers”.
182 The raw-pcr-file is an optional argument that contains the output of
184 the raw PCR contents as returned by tpm2_pcrread(1).
185 PCR bank specifiers (pcr.md)
187 Examples
189 To satisfy a PCR policy of sha256 on banks 0, 1, 2 and 3 use a specifi‐
190 er of:
191 pcr:sha256:0,1,2,3
193 specifying AUTH.
195
197 This collection of options are common to many programs and provide in‐
198 formation that many users may expect.
199 • -h, --help=[man|no-man]: Display the tools manpage. By default, it
201 attempts to invoke the manpager for the tool, however, on failure
202 will output a short tool summary. This is the same behavior if the
203 “man” option argument is specified, however if explicit “man” is re‐
204 quested, the tool will provide errors from man on stderr. If the
205 “no-man” option if specified, or the manpager fails, the short op‐
206 tions will be output to stdout.
207 To successfully use the manpages feature requires the manpages to be
209 installed or on MANPATH, See man(1) for more details.
210 • -v, --version: Display version information for this tool, supported
212 tctis and exit.
213 • -V, --verbose: Increase the information that the tool prints to the
215 console during its execution. When using this option the file and
216 line number are printed.
217 • -Q, --quiet: Silence normal tool output to stdout.
219 • -Z, --enable-errata: Enable the application of errata fixups. Useful
221 if an errata fixup needs to be applied to commands sent to the TPM.
222 Defining the environment TPM2TOOLS_ENABLE_ERRATA is equivalent. in‐
223 formation many users may expect.
224
226 The TCTI or “Transmission Interface” is the communication mechanism
227 with the TPM. TCTIs can be changed for communication with TPMs across
228 different mediums.
229 To control the TCTI, the tools respect:
231 1. The command line option -T or --tcti
233 2. The environment variable: TPM2TOOLS_TCTI.
235 Note: The command line option always overrides the environment vari‐
237 able.
238 The current known TCTIs are:
240 • tabrmd - The resource manager, called tabrmd
242 (https://github.com/tpm2-software/tpm2-abrmd). Note that tabrmd and
243 abrmd as a tcti name are synonymous.
244 • mssim - Typically used for communicating to the TPM software simula‐
246 tor.
247 • device - Used when talking directly to a TPM device file.
249 • none - Do not initalize a connection with the TPM. Some tools allow
251 for off-tpm options and thus support not using a TCTI. Tools that do
252 not support it will error when attempted to be used without a TCTI
253 connection. Does not support ANY options and MUST BE presented as
254 the exact text of “none”.
255 The arguments to either the command line option or the environment
257 variable are in the form:
258 <tcti-name>:<tcti-option-config>
260 Specifying an empty string for either the <tcti-name> or <tcti-op‐
262 tion-config> results in the default being used for that portion respec‐
263 tively.
264 TCTI Defaults
266 When a TCTI is not specified, the default TCTI is searched for using
267 dlopen(3) semantics. The tools will search for tabrmd, device and
268 mssim TCTIs IN THAT ORDER and USE THE FIRST ONE FOUND. You can query
269 what TCTI will be chosen as the default by using the -v option to print
270 the version information. The “default-tcti” key-value pair will indi‐
271 cate which of the aforementioned TCTIs is the default.
272 Custom TCTIs
274 Any TCTI that implements the dynamic TCTI interface can be loaded. The
275 tools internally use dlopen(3), and the raw tcti-name value is used for
276 the lookup. Thus, this could be a path to the shared library, or a li‐
277 brary name as understood by dlopen(3) semantics.
278
280 This collection of options are used to configure the various known TCTI
281 modules available:
282 • device: For the device TCTI, the TPM character device file for use by
284 the device TCTI can be specified. The default is /dev/tpm0.
285 Example: -T device:/dev/tpm0 or export TPM2TOOLS_TCTI=“de‐
287 vice:/dev/tpm0”
288 • mssim: For the mssim TCTI, the domain name or IP address and port
290 number used by the simulator can be specified. The default are
291 127.0.0.1 and 2321.
292 Example: -T mssim:host=localhost,port=2321 or export TPM2TOOLS_TC‐
294 TI=“mssim:host=localhost,port=2321”
295 • abrmd: For the abrmd TCTI, the configuration string format is a se‐
297 ries of simple key value pairs separated by a `,' character. Each
298 key and value string are separated by a `=' character.
299 • TCTI abrmd supports two keys:
301 1. `bus_name' : The name of the tabrmd service on the bus (a
303 string).
304 2. `bus_type' : The type of the dbus instance (a string) limited to
306 `session' and `system'.
307 Specify the tabrmd tcti name and a config string of bus_name=com.ex‐
309 ample.FooBar:
310 \--tcti=tabrmd:bus_name=com.example.FooBar
312 Specify the default (abrmd) tcti and a config string of bus_type=ses‐
314 sion:
315 \--tcti:bus_type=session
317 NOTE: abrmd and tabrmd are synonymous. the various known TCTI mod‐
319 ules.d)
320
322 Read 32 bytes from an index starting at offset 0
323 tpm2_nvdefine -C o -s 32 -a "ownerread|policywrite|ownerwrite" 1
324 echo "please123abc" > nv.dat
326 tpm2_nvwrite -C o -i nv.dat 1
328 tpm2_nvread -C o -s 32 1
330
332 Tools can return any of the following codes:
333 • 0 - Success.
335 • 1 - General non-specific error.
337 • 2 - Options handling error.
339 • 3 - Authentication error.
341 • 4 - TCTI related error.
343 • 5 - Non supported scheme. Applicable to tpm2_testparams.
345
347 Github Issues (https://github.com/tpm2-software/tpm2-tools/issues)
348
350 See the Mailing List (https://lists.linuxfoundation.org/mailman/listin‐
351 fo/tpm2)
352tpm2-tools tpm2_nvread(1)