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 • ARGUMENT the command line argument specifies the NV index or offset
55 number.
56 References
59 The type of a context object, whether it is a handle or file name, is
60 determined according to the following logic in-order:
61 • If the argument is a file path, then the file is loaded as a restored
63 TPM transient object.
64 • If the argument is a prefix match on one of:
66 • owner: the owner hierarchy
68 • platform: the platform hierarchy
70 • endorsement: the endorsement hierarchy
72 • lockout: the lockout control persistent object
74 • If the argument argument can be loaded as a number it will be treat
76 as a handle, e.g. 0x81010013 and used directly.OBJECT.
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79 Authorization for use of an object in TPM2.0 can come in 3 different
80 forms: 1. Password 2. HMAC 3. Sessions
81 NOTE: "Authorizations default to the EMPTY PASSWORD when not speci‐
83 fied".
84 Passwords
86 Passwords are interpreted in the following forms below using prefix
87 identifiers.
88 Note: By default passwords are assumed to be in the string form when
90 they do not have a prefix.
91 String
93 A string password, specified by prefix "str:" or it's absence (raw
94 string without prefix) is not interpreted, and is directly used for au‐
95 thorization.
96 Examples
98 foobar
99 str:foobar
100 Hex-string
102 A hex-string password, specified by prefix "hex:" is converted from a
103 hexidecimal form into a byte array form, thus allowing passwords with
104 non-printable and/or terminal un-friendly characters.
105 Example
107 hex:0x1122334455667788
108 File
110 A file based password, specified be prefix "file:" should be the path
111 of a file containing the password to be read by the tool or a "-" to
112 use stdin. Storing passwords in files prevents information leakage,
113 passwords passed as options can be read from the process list or common
114 shell history features.
115 Examples
117 # to use stdin and be prompted
118 file:-
119 # to use a file from a path
121 file:path/to/password/file
122 # to echo a password via stdin:
124 echo foobar | tpm2_tool -p file:-
125 # to use a bash here-string via stdin:
127 tpm2_tool -p file:- <<< foobar
129 Sessions
131 When using a policy session to authorize the use of an object, prefix
132 the option argument with the session keyword. Then indicate a path to
133 a session file that was created with tpm2_startauthsession(1). Option‐
134 ally, if the session requires an auth value to be sent with the session
135 handle (eg policy password), then append a + and a string as described
136 in the Passwords section.
137 Examples
139 To use a session context file called session.ctx.
140 session:session.ctx
142 To use a session context file called session.ctx AND send the authvalue
144 mypassword.
145 session:session.ctx+mypassword
147 To use a session context file called session.ctx AND send the HEX auth‐
149 value 0x11223344.
150 session:session.ctx+hex:11223344
152 PCR Authorizations
154 You can satisfy a PCR policy using the "pcr:" prefix and the PCR mini‐
155 language. The PCR minilanguage is as follows:
156 <pcr-spec>=<raw-pcr-file>
157 The PCR spec is documented in in the section "PCR bank specifiers".
159 The raw-pcr-file is an optional the output of the raw PCR contents as
161 returned by tpm2_pcrread(1).
162 PCR bank specifiers (common/pcr.md)
164 Examples
166 To satisfy a PCR policy of sha256 on banks 0, 1, 2 and 3 use a specifi‐
167 er of:
168 pcr:sha256:0,1,2,3
170 specifying AUTH.
172
174 This collection of options are common to many programs and provide in‐
175 formation that many users may expect.
176 • -h, --help=[man|no-man]: Display the tools manpage. By default, it
178 attempts to invoke the manpager for the tool, however, on failure
179 will output a short tool summary. This is the same behavior if the
180 "man" option argument is specified, however if explicit "man" is re‐
181 quested, the tool will provide errors from man on stderr. If the
182 "no-man" option if specified, or the manpager fails, the short op‐
183 tions will be output to stdout.
184 To successfully use the manpages feature requires the manpages to be
186 installed or on MANPATH, See man(1) for more details.
187 • -v, --version: Display version information for this tool, supported
189 tctis and exit.
190 • -V, --verbose: Increase the information that the tool prints to the
192 console during its execution. When using this option the file and
193 line number are printed.
194 • -Q, --quiet: Silence normal tool output to stdout.
196 • -Z, --enable-errata: Enable the application of errata fixups. Useful
198 if an errata fixup needs to be applied to commands sent to the TPM.
199 Defining the environment TPM2TOOLS_ENABLE_ERRATA is equivalent. in‐
200 formation many users may expect.
201
203 The TCTI or "Transmission Interface" is the communication mechanism
204 with the TPM. TCTIs can be changed for communication with TPMs across
205 different mediums.
206 To control the TCTI, the tools respect:
208 1. The command line option -T or --tcti
210 2. The environment variable: TPM2TOOLS_TCTI.
212 Note: The command line option always overrides the environment vari‐
214 able.
215 The current known TCTIs are:
217 • tabrmd - The resource manager, called tabrmd
219 (https://github.com/tpm2-software/tpm2-abrmd). Note that tabrmd and
220 abrmd as a tcti name are synonymous.
221 • mssim - Typically used for communicating to the TPM software simula‐
223 tor.
224 • device - Used when talking directly to a TPM device file.
226 • none - Do not initalize a connection with the TPM. Some tools allow
228 for off-tpm options and thus support not using a TCTI. Tools that do
229 not support it will error when attempted to be used without a TCTI
230 connection. Does not support ANY options and MUST BE presented as
231 the exact text of "none".
232 The arguments to either the command line option or the environment
234 variable are in the form:
235 <tcti-name>:<tcti-option-config>
237 Specifying an empty string for either the <tcti-name> or <tcti-op‐
239 tion-config> results in the default being used for that portion respec‐
240 tively.
241 TCTI Defaults
243 When a TCTI is not specified, the default TCTI is searched for using
244 dlopen(3) semantics. The tools will search for tabrmd, device and
245 mssim TCTIs IN THAT ORDER and USE THE FIRST ONE FOUND. You can query
246 what TCTI will be chosen as the default by using the -v option to print
247 the version information. The "default-tcti" key-value pair will indi‐
248 cate which of the aforementioned TCTIs is the default.
249 Custom TCTIs
251 Any TCTI that implements the dynamic TCTI interface can be loaded. The
252 tools internally use dlopen(3), and the raw tcti-name value is used for
253 the lookup. Thus, this could be a path to the shared library, or a li‐
254 brary name as understood by dlopen(3) semantics.
255
257 This collection of options are used to configure the various known TCTI
258 modules available:
259 • device: For the device TCTI, the TPM character device file for use by
261 the device TCTI can be specified. The default is /dev/tpm0.
262 Example: -T device:/dev/tpm0 or export TPM2TOOLS_TCTI="de‐
264 vice:/dev/tpm0"
265 • mssim: For the mssim TCTI, the domain name or IP address and port
267 number used by the simulator can be specified. The default are
268 127.0.0.1 and 2321.
269 Example: -T mssim:host=localhost,port=2321 or export TPM2TOOLS_TC‐
271 TI="mssim:host=localhost,port=2321"
272 • abrmd: For the abrmd TCTI, the configuration string format is a se‐
274 ries of simple key value pairs separated by a ',' character. Each
275 key and value string are separated by a '=' character.
276 • TCTI abrmd supports two keys:
278 1. 'bus_name' : The name of the tabrmd service on the bus (a
280 string).
281 2. 'bus_type' : The type of the dbus instance (a string) limited to
283 'session' and 'system'.
284 Specify the tabrmd tcti name and a config string of bus_name=com.ex‐
286 ample.FooBar:
287 \--tcti=tabrmd:bus_name=com.example.FooBar
289 Specify the default (abrmd) tcti and a config string of bus_type=ses‐
291 sion:
292 \--tcti:bus_type=session
294 NOTE: abrmd and tabrmd are synonymous. the various known TCTI mod‐
296 ules.d)
297
299 Read 32 bytes from an index starting at offset 0
300 tpm2_nvdefine -C o -s 32 -a "ownerread|policywrite|ownerwrite" 1
301 echo "please123abc" > nv.dat
303 tpm2_nvwrite -C o -i nv.dat 1
305 tpm2_nvread -C o -s 32 1
307
309 Tools can return any of the following codes:
310 • 0 - Success.
312 • 1 - General non-specific error.
314 • 2 - Options handling error.
316 • 3 - Authentication error.
318 • 4 - TCTI related error.
320 • 5 - Non supported scheme. Applicable to tpm2_testparams.
322
324 Github Issues (https://github.com/tpm2-software/tpm2-tools/issues)
325
327 See the Mailing List (https://lists.01.org/mailman/listinfo/tpm2)
328tpm2-tools tpm2_nvread(1)