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]
10
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 · ARGUMENT the command line argument specifies the NV index or offset
49 number.
50 References
53 The type of a context object, whether it is a handle or file name, is
54 determined according to the following logic in-order:
55 · If the argument is a file path, then the file is loaded as a restored
57 TPM transient object.
58 · If the argument is a prefix match on one of:
60 · owner: the owner hierarchy
62 · platform: the platform hierarchy
64 · endorsement: the endorsement hierarchy
66 · lockout: the lockout control persistent object
68 · If the argument argument can be loaded as a number it will be treat
70 as a handle, e.g. 0x81010013 and used directly.OBJECT.
71
73 Authorization for use of an object in TPM2.0 can come in 3 different
74 forms: 1. Password 2. HMAC 3. Sessions
75 NOTE: "Authorizations default to the EMPTY PASSWORD when not speci‐
77 fied".
78 Passwords
80 Passwords are interpreted in the following forms below using prefix
81 identifiers.
82 Note: By default passwords are assumed to be in the string form when
84 they do not have a prefix.
85 String
87 A string password, specified by prefix "str:" or it's absence (raw
88 string without prefix) is not interpreted, and is directly used for au‐
89 thorization.
90 Examples
92 foobar
93 str:foobar
94 Hex-string
96 A hex-string password, specified by prefix "hex:" is converted from a
97 hexidecimal form into a byte array form, thus allowing passwords with
98 non-printable and/or terminal un-friendly characters.
99 Example
101 hex:0x1122334455667788
102 File
104 A file based password, specified be prefix "file:" should be the path
105 of a file containing the password to be read by the tool or a "-" to
106 use stdin. Storing passwords in files prevents information leakage,
107 passwords passed as options can be read from the process list or common
108 shell history features.
109 Examples
111 # to use stdin and be prompted
112 file:-
113 # to use a file from a path
115 file:path/to/password/file
116 # to echo a password via stdin:
118 echo foobar | tpm2_tool -p file:-
119 # to use a bash here-string via stdin:
121 tpm2_tool -p file:- <<< foobar
123 Sessions
125 When using a policy session to authorize the use of an object, prefix
126 the option argument with the session keyword. Then indicate a path to
127 a session file that was created with tpm2_startauthsession(1). Option‐
128 ally, if the session requires an auth value to be sent with the session
129 handle (eg policy password), then append a + and a string as described
130 in the Passwords section.
131 Examples
133 To use a session context file called session.ctx.
134 session:session.ctx
136 To use a session context file called session.ctx AND send the authvalue
138 mypassword.
139 session:session.ctx+mypassword
141 To use a session context file called session.ctx AND send the HEX auth‐
143 value 0x11223344.
144 session:session.ctx+hex:11223344
146 PCR Authorizations
148 You can satisfy a PCR policy using the "pcr:" prefix and the PCR mini‐
149 language. The PCR minilanguage is as follows:
150 <pcr-spec>=<raw-pcr-file>
151 The PCR spec is documented in in the section "PCR bank specifiers".
153 The raw-pcr-file is an optional the output of the raw PCR contents as
155 returned by tpm2_pcrread(1).
156 PCR bank specifiers (common/pcr.md)
158 Examples
160 To satisfy a PCR policy of sha256 on banks 0, 1, 2 and 3 use a specifi‐
161 er of:
162 pcr:sha256:0,1,2,3
164 specifying AUTH.
166
168 This collection of options are common to many programs and provide in‐
169 formation that many users may expect.
170 · -h, --help=[man|no-man]: Display the tools manpage. By default, it
172 attempts to invoke the manpager for the tool, however, on failure
173 will output a short tool summary. This is the same behavior if the
174 "man" option argument is specified, however if explicit "man" is re‐
175 quested, the tool will provide errors from man on stderr. If the
176 "no-man" option if specified, or the manpager fails, the short op‐
177 tions will be output to stdout.
178 To successfully use the manpages feature requires the manpages to be
180 installed or on MANPATH, See man(1) for more details.
181 · -v, --version: Display version information for this tool, supported
183 tctis and exit.
184 · -V, --verbose: Increase the information that the tool prints to the
186 console during its execution. When using this option the file and
187 line number are printed.
188 · -Q, --quiet: Silence normal tool output to stdout.
190 · -Z, --enable-errata: Enable the application of errata fixups. Useful
192 if an errata fixup needs to be applied to commands sent to the TPM.
193 Defining the environment TPM2TOOLS_ENABLE_ERRATA is equivalent. in‐
194 formation many users may expect.
195
197 The TCTI or "Transmission Interface" is the communication mechanism
198 with the TPM. TCTIs can be changed for communication with TPMs across
199 different mediums.
200 To control the TCTI, the tools respect:
202 1. The command line option -T or --tcti
204 2. The environment variable: TPM2TOOLS_TCTI.
206 Note: The command line option always overrides the environment vari‐
208 able.
209 The current known TCTIs are:
211 · tabrmd - The resource manager, called tabrmd
213 (https://github.com/tpm2-software/tpm2-abrmd). Note that tabrmd and
214 abrmd as a tcti name are synonymous.
215 · mssim - Typically used for communicating to the TPM software simula‐
217 tor.
218 · device - Used when talking directly to a TPM device file.
220 · none - Do not initalize a connection with the TPM. Some tools allow
222 for off-tpm options and thus support not using a TCTI. Tools that do
223 not support it will error when attempted to be used without a TCTI
224 connection. Does not support ANY options and MUST BE presented as
225 the exact text of "none".
226 The arguments to either the command line option or the environment
228 variable are in the form:
229 <tcti-name>:<tcti-option-config>
231 Specifying an empty string for either the <tcti-name> or <tcti-op‐
233 tion-config> results in the default being used for that portion respec‐
234 tively.
235 TCTI Defaults
237 When a TCTI is not specified, the default TCTI is searched for using
238 dlopen(3) semantics. The tools will search for tabrmd, device and
239 mssim TCTIs IN THAT ORDER and USE THE FIRST ONE FOUND. You can query
240 what TCTI will be chosen as the default by using the -v option to print
241 the version information. The "default-tcti" key-value pair will indi‐
242 cate which of the aforementioned TCTIs is the default.
243 Custom TCTIs
245 Any TCTI that implements the dynamic TCTI interface can be loaded. The
246 tools internally use dlopen(3), and the raw tcti-name value is used for
247 the lookup. Thus, this could be a path to the shared library, or a li‐
248 brary name as understood by dlopen(3) semantics.
249
251 This collection of options are used to configure the various known TCTI
252 modules available:
253 · device: For the device TCTI, the TPM character device file for use by
255 the device TCTI can be specified. The default is /dev/tpm0.
256 Example: -T device:/dev/tpm0 or export TPM2TOOLS_TCTI="de‐
258 vice:/dev/tpm0"
259 · mssim: For the mssim TCTI, the domain name or IP address and port
261 number used by the simulator can be specified. The default are
262 127.0.0.1 and 2321.
263 Example: -T mssim:host=localhost,port=2321 or export TPM2TOOLS_TC‐
265 TI="mssim:host=localhost,port=2321"
266 · abrmd: For the abrmd TCTI, the configuration string format is a se‐
268 ries of simple key value pairs separated by a ',' character. Each
269 key and value string are separated by a '=' character.
270 · TCTI abrmd supports two keys:
272 1. 'bus_name' : The name of the tabrmd service on the bus (a
274 string).
275 2. 'bus_type' : The type of the dbus instance (a string) limited to
277 'session' and 'system'.
278 Specify the tabrmd tcti name and a config string of bus_name=com.ex‐
280 ample.FooBar:
281 \--tcti=tabrmd:bus_name=com.example.FooBar
283 Specify the default (abrmd) tcti and a config string of bus_type=ses‐
285 sion:
286 \--tcti:bus_type=session
288 NOTE: abrmd and tabrmd are synonymous. the various known TCTI mod‐
290 ules.d)
291
293 Read 32 bytes from an index starting at offset 0
294 tpm2_nvdefine -Q 1 -C o -s 32 -a "ownerread|policywrite|ownerwrite"
295 echo "please123abc" > nv.test_w
297 tpm2_nvwrite -Q $nv_test_index -C o -i nv.test_w
299 tpm2_nvread -Q 1 -C o -s 32 -o 0
301
303 Tools can return any of the following codes:
304 · 0 - Success.
306 · 1 - General non-specific error.
308 · 2 - Options handling error.
310 · 3 - Authentication error.
312 · 4 - TCTI related error.
314 · 5 - Non supported scheme. Applicable to tpm2_testparams.
316
318 Github Issues (https://github.com/tpm2-software/tpm2-tools/issues)
319
321 See the Mailing List (https://lists.01.org/mailman/listinfo/tpm2)
322tpm2-tools tpm2_nvread(1)