1tpm2_changeauth(1) General Commands Manual tpm2_changeauth(1)
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6 tpm2_changeauth - Changes authorization values for TPM objects.
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9 tpm2_changeauth [OPTIONS] [ARGUMENT]
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12 tpm2_changeauth - Configures authorization values for the various hier‐
13 archies, NV indices, transient and persistent objects.
14 Note: For non-permanent objects (Transient objects and Persistent ob‐
16 jects), copies of the private information (files or persistent handles)
17 created prior to changing auth are not invalidated.
18
20 Passwords should follow the “password authorization formatting stan‐
21 dards”, see section “Authorization Formatting”.
22 • -c, --object-context=OBJECT:
24 The key context object to be used for the operation.
26 • -p, --object-auth=AUTH:
28 The old authorization value for the TPM object specified with -c.
30 • -C, --parent-context=OBJECT:
32 The parent object. This is required if the object for the operation
34 is a transient or persistent object.
35 • -r, --private=FILE: The output file which contains the new sensitive
37 portion of the object whose auth was being changed. # Protection De‐
38 tails
39 Objects that can move outside of TPM need to be protected (confiden‐
41 tiality and integrity). For instance, transient objects require that
42 TPM protected data (key or seal material) be stored outside of the TPM.
43 This is seen in tools like tpm2_create(1), where the -r option outputs
44 this protected data. This blob contains the sensitive portions of the
45 object. The sensitive portions of the object are protected by the par‐
46 ent object, using the parent’s symmetric encryption details to encrypt
47 the sensitive data and HMAC it.
48 In-depth details can be found in sections 23 of:
50 • https://trustedcomputinggroup.org/wp-content/up‐
52 loads/TPM-Rev-2.0-Part-1-Architecture-01.38.pdf
53 Notably Figure 20, is relevant, even though it’s specifically referring
55 to duplication blobs, the process is identical.
56 If the output is from tpm2_duplicate(1), the output will be slightly
58 different, as described fully in section 23.
59 • --cphash=FILE
61 File path to record the hash of the command parameters. This is com‐
63 monly termed as cpHash. NOTE: When this option is selected, The tool
64 will not actually execute the command, it simply returns a cpHash,
65 unless rphash is also required.
66 • --rphash=FILE
68 File path to record the hash of the response parameters. This is
70 commonly termed as rpHash.
71 • -S, --session=FILE:
73 The session created using tpm2_startauthsession. This can be used to
75 specify an auxiliary session for auditing and or encryption/decryp‐
76 tion of the parameters.
77 • ARGUMENT the command line argument specifies the AUTH to be set for
79 the object specified with -c.
80 References
83 The type of a context object, whether it is a handle or file name, is
84 determined according to the following logic in-order:
85 • If the argument is a file path, then the file is loaded as a restored
87 TPM transient object.
88 • If the argument is a prefix match on one of:
90 • owner: the owner hierarchy
92 • platform: the platform hierarchy
94 • endorsement: the endorsement hierarchy
96 • lockout: the lockout control persistent object
98 • If the argument argument can be loaded as a number it will be treat
100 as a handle, e.g. 0x81010013 and used directly._OBJECT_.
101
103 Authorization for use of an object in TPM2.0 can come in 3 different
104 forms: 1. Password 2. HMAC 3. Sessions
105 NOTE: “Authorizations default to the EMPTY PASSWORD when not speci‐
107 fied”.
108 Passwords
110 Passwords are interpreted in the following forms below using prefix
111 identifiers.
112 Note: By default passwords are assumed to be in the string form when
114 they do not have a prefix.
115 String
117 A string password, specified by prefix “str:” or it’s absence (raw
118 string without prefix) is not interpreted, and is directly used for au‐
119 thorization.
120 Examples
122 foobar
123 str:foobar
124 Hex-string
126 A hex-string password, specified by prefix “hex:” is converted from a
127 hexidecimal form into a byte array form, thus allowing passwords with
128 non-printable and/or terminal un-friendly characters.
129 Example
131 hex:0x1122334455667788
132 File
134 A file based password, specified be prefix “file:” should be the path
135 of a file containing the password to be read by the tool or a “-” to
136 use stdin. Storing passwords in files prevents information leakage,
137 passwords passed as options can be read from the process list or common
138 shell history features.
139 Examples
141 # to use stdin and be prompted
142 file:-
143 # to use a file from a path
145 file:path/to/password/file
146 # to echo a password via stdin:
148 echo foobar | tpm2_tool -p file:-
149 # to use a bash here-string via stdin:
151 tpm2_tool -p file:- <<< foobar
153 Sessions
155 When using a policy session to authorize the use of an object, prefix
156 the option argument with the session keyword. Then indicate a path to
157 a session file that was created with tpm2_startauthsession(1). Option‐
158 ally, if the session requires an auth value to be sent with the session
159 handle (eg policy password), then append a + and a string as described
160 in the Passwords section.
161 Examples
163 To use a session context file called session.ctx.
164 session:session.ctx
166 To use a session context file called session.ctx AND send the authvalue
168 mypassword.
169 session:session.ctx+mypassword
171 To use a session context file called session.ctx AND send the HEX auth‐
173 value 0x11223344.
174 session:session.ctx+hex:11223344
176 PCR Authorizations
178 You can satisfy a PCR policy using the “pcr:” prefix and the PCR mini‐
179 language. The PCR minilanguage is as follows:
180 <pcr-spec>=<raw-pcr-file>
181 The PCR spec is documented in in the section “PCR bank specifiers”.
183 The raw-pcr-file is an optional argument that contains the output of
185 the raw PCR contents as returned by tpm2_pcrread(1).
186 PCR bank specifiers (pcr.md)
188 Examples
190 To satisfy a PCR policy of sha256 on banks 0, 1, 2 and 3 use a specifi‐
191 er of:
192 pcr:sha256:0,1,2,3
194 specifying AUTH.
196
198 This collection of options are common to many programs and provide in‐
199 formation that many users may expect.
200 • -h, --help=[man|no-man]: Display the tools manpage. By default, it
202 attempts to invoke the manpager for the tool, however, on failure
203 will output a short tool summary. This is the same behavior if the
204 “man” option argument is specified, however if explicit “man” is re‐
205 quested, the tool will provide errors from man on stderr. If the
206 “no-man” option if specified, or the manpager fails, the short op‐
207 tions will be output to stdout.
208 To successfully use the manpages feature requires the manpages to be
210 installed or on MANPATH, See man(1) for more details.
211 • -v, --version: Display version information for this tool, supported
213 tctis and exit.
214 • -V, --verbose: Increase the information that the tool prints to the
216 console during its execution. When using this option the file and
217 line number are printed.
218 • -Q, --quiet: Silence normal tool output to stdout.
220 • -Z, --enable-errata: Enable the application of errata fixups. Useful
222 if an errata fixup needs to be applied to commands sent to the TPM.
223 Defining the environment TPM2TOOLS_ENABLE_ERRATA is equivalent. in‐
224 formation many users may expect.
225
227 The TCTI or “Transmission Interface” is the communication mechanism
228 with the TPM. TCTIs can be changed for communication with TPMs across
229 different mediums.
230 To control the TCTI, the tools respect:
232 1. The command line option -T or --tcti
234 2. The environment variable: TPM2TOOLS_TCTI.
236 Note: The command line option always overrides the environment vari‐
238 able.
239 The current known TCTIs are:
241 • tabrmd - The resource manager, called tabrmd
243 (https://github.com/tpm2-software/tpm2-abrmd). Note that tabrmd and
244 abrmd as a tcti name are synonymous.
245 • mssim - Typically used for communicating to the TPM software simula‐
247 tor.
248 • device - Used when talking directly to a TPM device file.
250 • none - Do not initalize a connection with the TPM. Some tools allow
252 for off-tpm options and thus support not using a TCTI. Tools that do
253 not support it will error when attempted to be used without a TCTI
254 connection. Does not support ANY options and MUST BE presented as
255 the exact text of “none”.
256 The arguments to either the command line option or the environment
258 variable are in the form:
259 <tcti-name>:<tcti-option-config>
261 Specifying an empty string for either the <tcti-name> or <tcti-op‐
263 tion-config> results in the default being used for that portion respec‐
264 tively.
265 TCTI Defaults
267 When a TCTI is not specified, the default TCTI is searched for using
268 dlopen(3) semantics. The tools will search for tabrmd, device and
269 mssim TCTIs IN THAT ORDER and USE THE FIRST ONE FOUND. You can query
270 what TCTI will be chosen as the default by using the -v option to print
271 the version information. The “default-tcti” key-value pair will indi‐
272 cate which of the aforementioned TCTIs is the default.
273 Custom TCTIs
275 Any TCTI that implements the dynamic TCTI interface can be loaded. The
276 tools internally use dlopen(3), and the raw tcti-name value is used for
277 the lookup. Thus, this could be a path to the shared library, or a li‐
278 brary name as understood by dlopen(3) semantics.
279
281 This collection of options are used to configure the various known TCTI
282 modules available:
283 • device: For the device TCTI, the TPM character device file for use by
285 the device TCTI can be specified. The default is /dev/tpm0.
286 Example: -T device:/dev/tpm0 or export TPM2TOOLS_TCTI=“de‐
288 vice:/dev/tpm0”
289 • mssim: For the mssim TCTI, the domain name or IP address and port
291 number used by the simulator can be specified. The default are
292 127.0.0.1 and 2321.
293 Example: -T mssim:host=localhost,port=2321 or export TPM2TOOLS_TC‐
295 TI=“mssim:host=localhost,port=2321”
296 • abrmd: For the abrmd TCTI, the configuration string format is a se‐
298 ries of simple key value pairs separated by a `,' character. Each
299 key and value string are separated by a `=' character.
300 • TCTI abrmd supports two keys:
302 1. `bus_name' : The name of the tabrmd service on the bus (a
304 string).
305 2. `bus_type' : The type of the dbus instance (a string) limited to
307 `session' and `system'.
308 Specify the tabrmd tcti name and a config string of bus_name=com.ex‐
310 ample.FooBar:
311 \--tcti=tabrmd:bus_name=com.example.FooBar
313 Specify the default (abrmd) tcti and a config string of bus_type=ses‐
315 sion:
316 \--tcti:bus_type=session
318 NOTE: abrmd and tabrmd are synonymous. the various known TCTI mod‐
320 ules.
321
323 Set owner, endorsement and lockout authorizations to newpass
324 tpm2_changeauth -c owner newpass
325 tpm2_changeauth -c endorsement newpass
326 tpm2_changeauth -c lockout newpass
327 Change owner, endorsement and lockout authorizations
329 tpm2_changeauth -c o -p newpass newerpass
330 tpm2_changeauth -c e -p newpass newerpass
331 tpm2_changeauth -c l -p newpass newerpass
332 Set owner authorization to empty password
334 tpm2_changeauth -c o -p oldpass
335 Modify authorization for a loadable transient object
337 tpm2_createprimary -Q -C o -c prim.ctx
338 tpm2_create -Q -g sha256 -G aes -u key.pub -r key.priv -C prim.ctx
340 tpm2_load -C prim.ctx -u key.pub -r key.priv -n key.name -c key.ctx
342 tpm2_changeauth -c key.ctx -C prim.ctx -r key.priv newkeyauth
344 Modify authorization for a NV Index
346 Requires Extended Session Support.
347 tpm2_startauthsession -S session.ctx
349 tpm2_policycommandcode -S session.ctx -L policy.nvchange TPM2_CC_NV_ChangeAuth
351 tpm2_flushcontext session.ctx
352 NVIndex=0x1500015
354 tpm2_nvdefine $NVIndex -C o -s 32 -a "authread|authwrite" -L policy.nvchange
355 tpm2_startauthsession \--policy-session -S session.ctx
356 tpm2_policycommandcode -S session.ctx -L policy.nvchange TPM2_CC_NV_ChangeAuth
358 tpm2_changeauth -p session:session.ctx -c $NVIndex newindexauth
360
362 Tools can return any of the following codes:
363 • 0 - Success.
365 • 1 - General non-specific error.
367 • 2 - Options handling error.
369 • 3 - Authentication error.
371 • 4 - TCTI related error.
373 • 5 - Non supported scheme. Applicable to tpm2_testparams.
375
377 Github Issues (https://github.com/tpm2-software/tpm2-tools/issues)
378
380 See the Mailing List (https://lists.01.org/mailman/listinfo/tpm2)
381tpm2-tools tpm2_changeauth(1)