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.
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15 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.
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20 Passwords should follow the "password authorization formatting stan‐
21 dards", see section "Authorization Formatting".
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23 · -c, --object-context=OBJECT:
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25 The key context object to be used for the operation.
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27 · -p, --object-auth=AUTH:
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29 The old authorization value for the TPM object specified with -c.
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31 · -C, --parent-context=OBJECT:
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33 The parent object. This is required if the object for the operation
34 is a transient or persistent object.
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36 · -r, --private=FILE: The output file which contains the new sensitive
37 portion of the object whose auth was being changed.
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39 · ARGUMENT the command line argument specifies the AUTH to be set for
40 the object specified with -c.
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42 References
44 The type of a context object, whether it is a handle or file name, is
45 determined according to the following logic in-order:
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47 · If the argument is a file path, then the file is loaded as a restored
48 TPM transient object.
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50 · If the argument is a prefix match on one of:
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52 · owner: the owner hierarchy
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54 · platform: the platform hierarchy
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56 · endorsement: the endorsement hierarchy
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58 · lockout: the lockout control persistent object
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60 · If the argument argument can be loaded as a number it will be treat
61 as a handle, e.g. 0x81010013 and used directly.OBJECT.
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64 Authorization for use of an object in TPM2.0 can come in 3 different
65 forms: 1. Password 2. HMAC 3. Sessions
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67 NOTE: "Authorizations default to the EMPTY PASSWORD when not speci‐
68 fied".
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70 Passwords
71 Passwords are interpreted in the following forms below using prefix
72 identifiers.
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74 Note: By default passwords are assumed to be in the string form when
75 they do not have a prefix.
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77 String
78 A string password, specified by prefix "str:" or it's absence (raw
79 string without prefix) is not interpreted, and is directly used for au‐
80 thorization.
81
82 Examples
83 foobar
84 str:foobar
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86 Hex-string
87 A hex-string password, specified by prefix "hex:" is converted from a
88 hexidecimal form into a byte array form, thus allowing passwords with
89 non-printable and/or terminal un-friendly characters.
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91 Example
92 hex:0x1122334455667788
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94 File
95 A file based password, specified be prefix "file:" should be the path
96 of a file containing the password to be read by the tool or a "-" to
97 use stdin. Storing passwords in files prevents information leakage,
98 passwords passed as options can be read from the process list or common
99 shell history features.
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101 Examples
102 # to use stdin and be prompted
103 file:-
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105 # to use a file from a path
106 file:path/to/password/file
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108 # to echo a password via stdin:
109 echo foobar | tpm2_tool -p file:-
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111 # to use a bash here-string via stdin:
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113 tpm2_tool -p file:- <<< foobar
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115 Sessions
116 When using a policy session to authorize the use of an object, prefix
117 the option argument with the session keyword. Then indicate a path to
118 a session file that was created with tpm2_startauthsession(1). Option‐
119 ally, if the session requires an auth value to be sent with the session
120 handle (eg policy password), then append a + and a string as described
121 in the Passwords section.
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123 Examples
124 To use a session context file called session.ctx.
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126 session:session.ctx
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128 To use a session context file called session.ctx AND send the authvalue
129 mypassword.
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131 session:session.ctx+mypassword
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133 To use a session context file called session.ctx AND send the HEX auth‐
134 value 0x11223344.
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136 session:session.ctx+hex:11223344
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138 PCR Authorizations
139 You can satisfy a PCR policy using the "pcr:" prefix and the PCR mini‐
140 language. The PCR minilanguage is as follows:
141 <pcr-spec>=<raw-pcr-file>
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143 The PCR spec is documented in in the section "PCR bank specifiers".
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145 The raw-pcr-file is an optional the output of the raw PCR contents as
146 returned by tpm2_pcrread(1).
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148 PCR bank specifiers (common/pcr.md)
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150 Examples
151 To satisfy a PCR policy of sha256 on banks 0, 1, 2 and 3 use a specifi‐
152 er of:
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154 pcr:sha256:0,1,2,3
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156 specifying AUTH.
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159 This collection of options are common to many programs and provide in‐
160 formation that many users may expect.
161
162 · -h, --help=[man|no-man]: Display the tools manpage. By default, it
163 attempts to invoke the manpager for the tool, however, on failure
164 will output a short tool summary. This is the same behavior if the
165 "man" option argument is specified, however if explicit "man" is re‐
166 quested, the tool will provide errors from man on stderr. If the
167 "no-man" option if specified, or the manpager fails, the short op‐
168 tions will be output to stdout.
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170 To successfully use the manpages feature requires the manpages to be
171 installed or on MANPATH, See man(1) for more details.
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173 · -v, --version: Display version information for this tool, supported
174 tctis and exit.
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176 · -V, --verbose: Increase the information that the tool prints to the
177 console during its execution. When using this option the file and
178 line number are printed.
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180 · -Q, --quiet: Silence normal tool output to stdout.
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182 · -Z, --enable-errata: Enable the application of errata fixups. Useful
183 if an errata fixup needs to be applied to commands sent to the TPM.
184 Defining the environment TPM2TOOLS_ENABLE_ERRATA is equivalent. in‐
185 formation many users may expect.
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188 The TCTI or "Transmission Interface" is the communication mechanism
189 with the TPM. TCTIs can be changed for communication with TPMs across
190 different mediums.
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192 To control the TCTI, the tools respect:
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194 1. The command line option -T or --tcti
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196 2. The environment variable: TPM2TOOLS_TCTI.
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198 Note: The command line option always overrides the environment vari‐
199 able.
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201 The current known TCTIs are:
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203 · tabrmd - The resource manager, called tabrmd
204 (https://github.com/tpm2-software/tpm2-abrmd). Note that tabrmd and
205 abrmd as a tcti name are synonymous.
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207 · mssim - Typically used for communicating to the TPM software simula‐
208 tor.
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210 · device - Used when talking directly to a TPM device file.
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212 · none - Do not initalize a connection with the TPM. Some tools allow
213 for off-tpm options and thus support not using a TCTI. Tools that do
214 not support it will error when attempted to be used without a TCTI
215 connection. Does not support ANY options and MUST BE presented as
216 the exact text of "none".
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218 The arguments to either the command line option or the environment
219 variable are in the form:
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221 <tcti-name>:<tcti-option-config>
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223 Specifying an empty string for either the <tcti-name> or <tcti-op‐
224 tion-config> results in the default being used for that portion respec‐
225 tively.
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227 TCTI Defaults
228 When a TCTI is not specified, the default TCTI is searched for using
229 dlopen(3) semantics. The tools will search for tabrmd, device and
230 mssim TCTIs IN THAT ORDER and USE THE FIRST ONE FOUND. You can query
231 what TCTI will be chosen as the default by using the -v option to print
232 the version information. The "default-tcti" key-value pair will indi‐
233 cate which of the aforementioned TCTIs is the default.
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235 Custom TCTIs
236 Any TCTI that implements the dynamic TCTI interface can be loaded. The
237 tools internally use dlopen(3), and the raw tcti-name value is used for
238 the lookup. Thus, this could be a path to the shared library, or a li‐
239 brary name as understood by dlopen(3) semantics.
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242 This collection of options are used to configure the various known TCTI
243 modules available:
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245 · device: For the device TCTI, the TPM character device file for use by
246 the device TCTI can be specified. The default is /dev/tpm0.
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248 Example: -T device:/dev/tpm0 or export TPM2TOOLS_TCTI="de‐
249 vice:/dev/tpm0"
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251 · mssim: For the mssim TCTI, the domain name or IP address and port
252 number used by the simulator can be specified. The default are
253 127.0.0.1 and 2321.
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255 Example: -T mssim:host=localhost,port=2321 or export TPM2TOOLS_TC‐
256 TI="mssim:host=localhost,port=2321"
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258 · abrmd: For the abrmd TCTI, the configuration string format is a se‐
259 ries of simple key value pairs separated by a ',' character. Each
260 key and value string are separated by a '=' character.
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262 · TCTI abrmd supports two keys:
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264 1. 'bus_name' : The name of the tabrmd service on the bus (a
265 string).
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267 2. 'bus_type' : The type of the dbus instance (a string) limited to
268 'session' and 'system'.
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270 Specify the tabrmd tcti name and a config string of bus_name=com.ex‐
271 ample.FooBar:
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273 \--tcti=tabrmd:bus_name=com.example.FooBar
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275 Specify the default (abrmd) tcti and a config string of bus_type=ses‐
276 sion:
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278 \--tcti:bus_type=session
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280 NOTE: abrmd and tabrmd are synonymous. the various known TCTI mod‐
281 ules.
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284 Set owner, endorsement and lockout authorizations to newpass
285 tpm2_changeauth -c owner newpass
286 tpm2_changeauth -c endorsement newpass
287 tpm2_changeauth -c lockout newpass
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289 Change owner, endorsement and lockout authorizations
290 tpm2_changeauth -c o -p newpass newerpass
291 tpm2_changeauth -c e -p newpass newerpass
292 tpm2_changeauth -c l -p newpass newerpass
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294 Set owner authorization to empty password
295 tpm2_changeauth -c o -p oldpass
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297 Modify authorization for a loadable transient object
298 tpm2_createprimary -Q -C o -c prim.ctx
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300 tpm2_create -Q -g sha256 -G aes -u key.pub -r key.priv -C prim.ctx
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302 tpm2_load -C prim.ctx -u key.pub -r key.priv -n key.name -c key.ctx
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304 tpm2_changeauth -c key.ctx -C prim.ctx -r key.priv newkeyauth
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306 Modify authorization for a NV Index
307 Requires Extended Session Support.
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309 tpm2_startauthsession -S session.ctx
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311 tpm2_policycommandcode -S session.ctx -L policy.nvchange TPM2_CC_NV_ChangeAuth
312 tpm2_flushcontext session.ctx
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314 NVIndex=0x1500015
315 tpm2_nvdefine $NVIndex -C o -s 32 -a "authread|authwrite" -L policy.nvchange
316 tpm2_startauthsession \--policy-session -S session.ctx
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318 tpm2_policycommandcode -S session.ctx -L policy.nvchange TPM2_CC_NV_ChangeAuth
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320 tpm2_changeauth -p session:session.ctx -c $NVIndex newindexauth
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323 Tools can return any of the following codes:
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325 · 0 - Success.
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327 · 1 - General non-specific error.
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329 · 2 - Options handling error.
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331 · 3 - Authentication error.
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333 · 4 - TCTI related error.
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335 · 5 - Non supported scheme. Applicable to tpm2_testparams.
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338 Github Issues (https://github.com/tpm2-software/tpm2-tools/issues)
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341 See the Mailing List (https://lists.01.org/mailman/listinfo/tpm2)
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345tpm2-tools tpm2_changeauth(1)