1tpm2_policysecret(1) General Commands Manual tpm2_policysecret(1)
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6 tpm2_policysecret(1) - Couples the authorization of an object to that
7 of an existing object.
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10 tpm2_policysecret [OPTIONS] [ARGUMENT]
11
13 tpm2_policysecret(1) - Couples the authorization of an object to that
14 of an existing object without requiring exposing the existing secret
15 until time of object use.
16
18 • -c, --object-context=OBJECT:
19 A context object specifier of a transient/permanent/persistent ob‐
21 ject. Either a file path of a object context blob or a loaded/per‐
22 sistent/permanent handle id. See section “Context Object Format”.
23 As an argument, it takes the auth value of the associated TPM object,
24 a single dash - can be used to read the auth value from stdin. The
25 argument follows the “authorization formatting standards”, see sec‐
26 tion “Authorization Formatting”.
27 • -S, --session=FILE:
29 The policy session file generated via the -S option to tpm2_star‐
31 tauthsession(1).
32 • -L, --policy=FILE:
34 File to save the policy digest.
36 • -t, --expiration=NATURAL_NUMBER:
38 Set the expiration time of the policy in seconds. In absence of non‐
40 ceTPM the expiration time is the policy timeout value. If expiration
41 value is 0 then the policy does not have a time limit on the autho‐
42 rization.
43 • --ticket=FILE:
45 The ticket file to record the authorization ticket structure.
47 • --timeout=FILE:
49 The file path to record the timeout structure returned.
51 • -x, --nonce-tpm:
53 Enable the comparison of the current session’s nonceTPM to ensure the
55 validity of the policy authorization is limited to the current ses‐
56 sion.
57 • -q, --qualification=FILE_OR_HEX_STR:
59 Optional, the policy qualifier data that the signer can choose to in‐
61 clude in the signature. Can be either a hex string or path.
62 • --cphash=FILE
64 File path to record the hash of the command parameters. This is com‐
66 monly termed as cpHash. NOTE: When this option is selected, The tool
67 will not actually execute the command, it simply returns a cpHash to
68 be used in an audit or a policycphash.
69 • ARGUMENT the command line argument specifies the AUTH to be set for
71 the object specified with -c.
72 References
75 The type of a context object, whether it is a handle or file name, is
76 determined according to the following logic in-order:
77 • If the argument is a file path, then the file is loaded as a restored
79 TPM transient object.
80 • If the argument is a prefix match on one of:
82 • owner: the owner hierarchy
84 • platform: the platform hierarchy
86 • endorsement: the endorsement hierarchy
88 • lockout: the lockout control persistent object
90 • If the argument argument can be loaded as a number it will be treat
92 as a handle, e.g. 0x81010013 and used directly._OBJECT_.
93
95 Authorization for use of an object in TPM2.0 can come in 3 different
96 forms: 1. Password 2. HMAC 3. Sessions
97 NOTE: “Authorizations default to the EMPTY PASSWORD when not speci‐
99 fied”.
100 Passwords
102 Passwords are interpreted in the following forms below using prefix
103 identifiers.
104 Note: By default passwords are assumed to be in the string form when
106 they do not have a prefix.
107 String
109 A string password, specified by prefix “str:” or it’s absence (raw
110 string without prefix) is not interpreted, and is directly used for au‐
111 thorization.
112 Examples
114 foobar
115 str:foobar
116 Hex-string
118 A hex-string password, specified by prefix “hex:” is converted from a
119 hexidecimal form into a byte array form, thus allowing passwords with
120 non-printable and/or terminal un-friendly characters.
121 Example
123 hex:1122334455667788
124 File
126 A file based password, specified be prefix “file:” should be the path
127 of a file containing the password to be read by the tool or a “-” to
128 use stdin. Storing passwords in files prevents information leakage,
129 passwords passed as options can be read from the process list or common
130 shell history features.
131 Examples
133 # to use stdin and be prompted
134 file:-
135 # to use a file from a path
137 file:path/to/password/file
138 # to echo a password via stdin:
140 echo foobar | tpm2_tool -p file:-
141 # to use a bash here-string via stdin:
143 tpm2_tool -p file:- <<< foobar
145 Sessions
147 When using a policy session to authorize the use of an object, prefix
148 the option argument with the session keyword. Then indicate a path to
149 a session file that was created with tpm2_startauthsession(1). Option‐
150 ally, if the session requires an auth value to be sent with the session
151 handle (eg policy password), then append a + and a string as described
152 in the Passwords section.
153 Examples
155 To use a session context file called session.ctx.
156 session:session.ctx
158 To use a session context file called session.ctx AND send the authvalue
160 mypassword.
161 session:session.ctx+mypassword
163 To use a session context file called session.ctx AND send the HEX auth‐
165 value 0x11223344.
166 session:session.ctx+hex:11223344
168 PCR Authorizations
170 You can satisfy a PCR policy using the “pcr:” prefix and the PCR mini‐
171 language. The PCR minilanguage is as follows:
172 <pcr-spec>=<raw-pcr-file>
173 The PCR spec is documented in in the section “PCR bank specifiers”.
175 The raw-pcr-file is an optional argument that contains the output of
177 the raw PCR contents as returned by tpm2_pcrread(1).
178 PCR bank specifiers (pcr.md)
180 Examples
182 To satisfy a PCR policy of sha256 on banks 0, 1, 2 and 3 use a specifi‐
183 er of:
184 pcr:sha256:0,1,2,3
186 specifying AUTH.
188
190 This collection of options are common to many programs and provide in‐
191 formation that many users may expect.
192 • -h, --help=[man|no-man]: Display the tools manpage. By default, it
194 attempts to invoke the manpager for the tool, however, on failure
195 will output a short tool summary. This is the same behavior if the
196 “man” option argument is specified, however if explicit “man” is re‐
197 quested, the tool will provide errors from man on stderr. If the
198 “no-man” option if specified, or the manpager fails, the short op‐
199 tions will be output to stdout.
200 To successfully use the manpages feature requires the manpages to be
202 installed or on MANPATH, See man(1) for more details.
203 • -v, --version: Display version information for this tool, supported
205 tctis and exit.
206 • -V, --verbose: Increase the information that the tool prints to the
208 console during its execution. When using this option the file and
209 line number are printed.
210 • -Q, --quiet: Silence normal tool output to stdout.
212 • -Z, --enable-errata: Enable the application of errata fixups. Useful
214 if an errata fixup needs to be applied to commands sent to the TPM.
215 Defining the environment TPM2TOOLS_ENABLE_ERRATA is equivalent. in‐
216 formation many users may expect.
217
219 The TCTI or “Transmission Interface” is the communication mechanism
220 with the TPM. TCTIs can be changed for communication with TPMs across
221 different mediums.
222 To control the TCTI, the tools respect:
224 1. The command line option -T or --tcti
226 2. The environment variable: TPM2TOOLS_TCTI.
228 Note: The command line option always overrides the environment vari‐
230 able.
231 The current known TCTIs are:
233 • tabrmd - The resource manager, called tabrmd
235 (https://github.com/tpm2-software/tpm2-abrmd). Note that tabrmd and
236 abrmd as a tcti name are synonymous.
237 • mssim - Typically used for communicating to the TPM software simula‐
239 tor.
240 • device - Used when talking directly to a TPM device file.
242 • none - Do not initalize a connection with the TPM. Some tools allow
244 for off-tpm options and thus support not using a TCTI. Tools that do
245 not support it will error when attempted to be used without a TCTI
246 connection. Does not support ANY options and MUST BE presented as
247 the exact text of “none”.
248 The arguments to either the command line option or the environment
250 variable are in the form:
251 <tcti-name>:<tcti-option-config>
253 Specifying an empty string for either the <tcti-name> or <tcti-op‐
255 tion-config> results in the default being used for that portion respec‐
256 tively.
257 TCTI Defaults
259 When a TCTI is not specified, the default TCTI is searched for using
260 dlopen(3) semantics. The tools will search for tabrmd, device and
261 mssim TCTIs IN THAT ORDER and USE THE FIRST ONE FOUND. You can query
262 what TCTI will be chosen as the default by using the -v option to print
263 the version information. The “default-tcti” key-value pair will indi‐
264 cate which of the aforementioned TCTIs is the default.
265 Custom TCTIs
267 Any TCTI that implements the dynamic TCTI interface can be loaded. The
268 tools internally use dlopen(3), and the raw tcti-name value is used for
269 the lookup. Thus, this could be a path to the shared library, or a li‐
270 brary name as understood by dlopen(3) semantics.
271
273 This collection of options are used to configure the various known TCTI
274 modules available:
275 • device: For the device TCTI, the TPM character device file for use by
277 the device TCTI can be specified. The default is /dev/tpm0.
278 Example: -T device:/dev/tpm0 or export TPM2TOOLS_TCTI=“de‐
280 vice:/dev/tpm0”
281 • mssim: For the mssim TCTI, the domain name or IP address and port
283 number used by the simulator can be specified. The default are
284 127.0.0.1 and 2321.
285 Example: -T mssim:host=localhost,port=2321 or export TPM2TOOLS_TC‐
287 TI=“mssim:host=localhost,port=2321”
288 • abrmd: For the abrmd TCTI, the configuration string format is a se‐
290 ries of simple key value pairs separated by a `,' character. Each
291 key and value string are separated by a `=' character.
292 • TCTI abrmd supports two keys:
294 1. `bus_name' : The name of the tabrmd service on the bus (a
296 string).
297 2. `bus_type' : The type of the dbus instance (a string) limited to
299 `session' and `system'.
300 Specify the tabrmd tcti name and a config string of bus_name=com.ex‐
302 ample.FooBar:
303 \--tcti=tabrmd:bus_name=com.example.FooBar
305 Specify the default (abrmd) tcti and a config string of bus_type=ses‐
307 sion:
308 \--tcti:bus_type=session
310 NOTE: abrmd and tabrmd are synonymous. the various known TCTI mod‐
312 ules.
313
315 Associate auth value of a sealing object to the owner hierarchy pass‐
316 word. * Start a trial auth session and run tpm2_policysecret(1) to
317 create policy that can only be satisfied if owner hierarchy auth value
318 is supplied. * Start a real policy session and provide the owner hier‐
319 archy auth value. * Provide the session input where in the policyse‐
320 cret for owner hierarchy auth was satisfied to the unseal tool. * If
321 the policy was satisfied unsealing should succeed.
322 Generate a policy that binds to the secret of the owner hiearchy
324 tpm2_startauthsession -S session.ctx
325 tpm2_policysecret -S session.ctx -c o -L secret.policy
327 tpm2_flushcontext session.ctx
329 Create a TPM object using the policy
331 tpm2_createprimary -Q -C o -g sha256 -G rsa -c prim.ctx
332 tpm2_create -Q -g sha256 -u sealing_key.pub -r sealing_key.priv -i- \
334 -C prim.ctx -L secret.policy <<< "SEALED-SECRET"
335 tpm2_load -C prim.ctx -u sealing_key.pub -r sealing_key.priv \
337 -c sealing_key.ctx
338 Satisfy the policy and unseal the secret
340 tpm2_startauthsession --policy-session -S session.ctx
341 tpm2_policysecret -S session.ctx -c o -L secret.policy
343 tpm2_unseal -p "session:session.ctx" -c sealing_key.ctx
345 SEALED-SECRET
346 tpm2_flushcontext session.ctx
348
350 Tools can return any of the following codes:
351 • 0 - Success.
353 • 1 - General non-specific error.
355 • 2 - Options handling error.
357 • 3 - Authentication error.
359 • 4 - TCTI related error.
361 • 5 - Non supported scheme. Applicable to tpm2_testparams.
363
365 It expects a session to be already established via tpm2_startauthses‐
366 sion(1) and requires one of the following:
367 • direct device access
369 • extended session support with tpm2-abrmd.
371 Without it, most resource managers will not save session state between
373 command invocations.
374
376 Github Issues (https://github.com/tpm2-software/tpm2-tools/issues)
377
379 See the Mailing List (https://lists.linuxfoundation.org/mailman/listin‐
380 fo/tpm2)
381tpm2-tools tpm2_policysecret(1)