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 • ARGUMENT the command line argument specifies the NV index or offset
72 number.
73 References
76 The type of a context object, whether it is a handle or file name, is
77 determined according to the following logic in-order:
78 • If the argument is a file path, then the file is loaded as a restored
80 TPM transient object.
81 • If the argument is a prefix match on one of:
83 • owner: the owner hierarchy
85 • platform: the platform hierarchy
87 • endorsement: the endorsement hierarchy
89 • lockout: the lockout control persistent object
91 • If the argument argument can be loaded as a number it will be treat
93 as a handle, e.g. 0x81010013 and used directly._OBJECT_.
94
96 Authorization for use of an object in TPM2.0 can come in 3 different
97 forms: 1. Password 2. HMAC 3. Sessions
98 NOTE: “Authorizations default to the EMPTY PASSWORD when not speci‐
100 fied”.
101 Passwords
103 Passwords are interpreted in the following forms below using prefix
104 identifiers.
105 Note: By default passwords are assumed to be in the string form when
107 they do not have a prefix.
108 String
110 A string password, specified by prefix “str:” or it’s absence (raw
111 string without prefix) is not interpreted, and is directly used for au‐
112 thorization.
113 Examples
115 foobar
116 str:foobar
117 Hex-string
119 A hex-string password, specified by prefix “hex:” is converted from a
120 hexidecimal form into a byte array form, thus allowing passwords with
121 non-printable and/or terminal un-friendly characters.
122 Example
124 hex:0x1122334455667788
125 File
127 A file based password, specified be prefix “file:” should be the path
128 of a file containing the password to be read by the tool or a “-” to
129 use stdin. Storing passwords in files prevents information leakage,
130 passwords passed as options can be read from the process list or common
131 shell history features.
132 Examples
134 # to use stdin and be prompted
135 file:-
136 # to use a file from a path
138 file:path/to/password/file
139 # to echo a password via stdin:
141 echo foobar | tpm2_tool -p file:-
142 # to use a bash here-string via stdin:
144 tpm2_tool -p file:- <<< foobar
146 Sessions
148 When using a policy session to authorize the use of an object, prefix
149 the option argument with the session keyword. Then indicate a path to
150 a session file that was created with tpm2_startauthsession(1). Option‐
151 ally, if the session requires an auth value to be sent with the session
152 handle (eg policy password), then append a + and a string as described
153 in the Passwords section.
154 Examples
156 To use a session context file called session.ctx.
157 session:session.ctx
159 To use a session context file called session.ctx AND send the authvalue
161 mypassword.
162 session:session.ctx+mypassword
164 To use a session context file called session.ctx AND send the HEX auth‐
166 value 0x11223344.
167 session:session.ctx+hex:11223344
169 PCR Authorizations
171 You can satisfy a PCR policy using the “pcr:” prefix and the PCR mini‐
172 language. The PCR minilanguage is as follows:
173 <pcr-spec>=<raw-pcr-file>
174 The PCR spec is documented in in the section “PCR bank specifiers”.
176 The raw-pcr-file is an optional argument that contains the output of
178 the raw PCR contents as returned by tpm2_pcrread(1).
179 PCR bank specifiers (pcr.md)
181 Examples
183 To satisfy a PCR policy of sha256 on banks 0, 1, 2 and 3 use a specifi‐
184 er of:
185 pcr:sha256:0,1,2,3
187 specifying AUTH.
189
191 This collection of options are common to many programs and provide in‐
192 formation that many users may expect.
193 • -h, --help=[man|no-man]: Display the tools manpage. By default, it
195 attempts to invoke the manpager for the tool, however, on failure
196 will output a short tool summary. This is the same behavior if the
197 “man” option argument is specified, however if explicit “man” is re‐
198 quested, the tool will provide errors from man on stderr. If the
199 “no-man” option if specified, or the manpager fails, the short op‐
200 tions will be output to stdout.
201 To successfully use the manpages feature requires the manpages to be
203 installed or on MANPATH, See man(1) for more details.
204 • -v, --version: Display version information for this tool, supported
206 tctis and exit.
207 • -V, --verbose: Increase the information that the tool prints to the
209 console during its execution. When using this option the file and
210 line number are printed.
211 • -Q, --quiet: Silence normal tool output to stdout.
213 • -Z, --enable-errata: Enable the application of errata fixups. Useful
215 if an errata fixup needs to be applied to commands sent to the TPM.
216 Defining the environment TPM2TOOLS_ENABLE_ERRATA is equivalent. in‐
217 formation many users may expect.
218
220 The TCTI or “Transmission Interface” is the communication mechanism
221 with the TPM. TCTIs can be changed for communication with TPMs across
222 different mediums.
223 To control the TCTI, the tools respect:
225 1. The command line option -T or --tcti
227 2. The environment variable: TPM2TOOLS_TCTI.
229 Note: The command line option always overrides the environment vari‐
231 able.
232 The current known TCTIs are:
234 • tabrmd - The resource manager, called tabrmd
236 (https://github.com/tpm2-software/tpm2-abrmd). Note that tabrmd and
237 abrmd as a tcti name are synonymous.
238 • mssim - Typically used for communicating to the TPM software simula‐
240 tor.
241 • device - Used when talking directly to a TPM device file.
243 • none - Do not initalize a connection with the TPM. Some tools allow
245 for off-tpm options and thus support not using a TCTI. Tools that do
246 not support it will error when attempted to be used without a TCTI
247 connection. Does not support ANY options and MUST BE presented as
248 the exact text of “none”.
249 The arguments to either the command line option or the environment
251 variable are in the form:
252 <tcti-name>:<tcti-option-config>
254 Specifying an empty string for either the <tcti-name> or <tcti-op‐
256 tion-config> results in the default being used for that portion respec‐
257 tively.
258 TCTI Defaults
260 When a TCTI is not specified, the default TCTI is searched for using
261 dlopen(3) semantics. The tools will search for tabrmd, device and
262 mssim TCTIs IN THAT ORDER and USE THE FIRST ONE FOUND. You can query
263 what TCTI will be chosen as the default by using the -v option to print
264 the version information. The “default-tcti” key-value pair will indi‐
265 cate which of the aforementioned TCTIs is the default.
266 Custom TCTIs
268 Any TCTI that implements the dynamic TCTI interface can be loaded. The
269 tools internally use dlopen(3), and the raw tcti-name value is used for
270 the lookup. Thus, this could be a path to the shared library, or a li‐
271 brary name as understood by dlopen(3) semantics.
272
274 This collection of options are used to configure the various known TCTI
275 modules available:
276 • device: For the device TCTI, the TPM character device file for use by
278 the device TCTI can be specified. The default is /dev/tpm0.
279 Example: -T device:/dev/tpm0 or export TPM2TOOLS_TCTI=“de‐
281 vice:/dev/tpm0”
282 • mssim: For the mssim TCTI, the domain name or IP address and port
284 number used by the simulator can be specified. The default are
285 127.0.0.1 and 2321.
286 Example: -T mssim:host=localhost,port=2321 or export TPM2TOOLS_TC‐
288 TI=“mssim:host=localhost,port=2321”
289 • abrmd: For the abrmd TCTI, the configuration string format is a se‐
291 ries of simple key value pairs separated by a `,' character. Each
292 key and value string are separated by a `=' character.
293 • TCTI abrmd supports two keys:
295 1. `bus_name' : The name of the tabrmd service on the bus (a
297 string).
298 2. `bus_type' : The type of the dbus instance (a string) limited to
300 `session' and `system'.
301 Specify the tabrmd tcti name and a config string of bus_name=com.ex‐
303 ample.FooBar:
304 \--tcti=tabrmd:bus_name=com.example.FooBar
306 Specify the default (abrmd) tcti and a config string of bus_type=ses‐
308 sion:
309 \--tcti:bus_type=session
311 NOTE: abrmd and tabrmd are synonymous. the various known TCTI mod‐
313 ules.d)
314
316 Read 32 bytes from an index starting at offset 0
317 tpm2_nvdefine -C o -s 32 -a "ownerread|policywrite|ownerwrite" 1
318 echo "please123abc" > nv.dat
320 tpm2_nvwrite -C o -i nv.dat 1
322 tpm2_nvread -C o -s 32 1
324
326 Tools can return any of the following codes:
327 • 0 - Success.
329 • 1 - General non-specific error.
331 • 2 - Options handling error.
333 • 3 - Authentication error.
335 • 4 - TCTI related error.
337 • 5 - Non supported scheme. Applicable to tpm2_testparams.
339
341 Github Issues (https://github.com/tpm2-software/tpm2-tools/issues)
342
344 See the Mailing List (https://lists.01.org/mailman/listinfo/tpm2)
345tpm2-tools tpm2_nvread(1)