1tpm2_startauthsession(1) General Commands Manual tpm2_startauthsession(1)
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6 tpm2_startauthsession(1) - Start a session with the TPM.
7
9 tpm2_startauthsession [OPTIONS]
10
12 tpm2_startauthsession(1) - Starts a session with the TPM. The default
13 is to start a trial session unless the -a option is specified. Saves
14 the policy session data to a file. This file can then be used in sub‐
15 sequent tools that can use a policy file for authorization or policy
16 events.
17 This will not work with resource managers (RMs) outside of tpm2-abrmd
19 (https://%20github.com/tpm2-software/tpm2-abrmd), as most RMs will
20 flush session handles when a client disconnects from the IPC channel.
21 This will work with direct TPM access, but note that internally this
23 calls a ContextSave and a ContextLoad on the session handle, thus the
24 session cannot be saved/loaded again.
25
27 • --policy-session:
28 Start a policy session of type TPM_SE_POLICY. Default without this
30 option is TPM_SE_TRIAL.
31 NOTE: A trial session is used when building a policy and a policy
33 session is used when authenticating with a policy.
34 • --audit-session:
36 Start an HMAC session to be used as an audit session. Default with‐
38 out this option is TPM2_SE_TRIAL.
39 • --hmac-session:
41 Start an HMAC session of type TPM_SE_HMAC. Default without this op‐
43 tion is TPM2_SE_TRIAL.
44 • -g, --hash-algorithm=ALGORITHM:
46 The hash algorithm used in computation of the policy digest.
48 • -c, --key-context=OBJECT:
50 Set the tpmkey and bind objects to be the same. Session parameter
52 encryption is turned on. Session parameter decryption is turned on.
53 Parameter encryption/decryption symmetric-key set to AES-CFB.
54 • -S, --session=FILE:
56 The name of the policy session file, required.
58 • --bind-context=FILE:
60 Set the bind object. Session parameter encryption is off. Use
62 tpm2_sessionconfig to turn on. Session parameter decryption is off.
63 Use tpm2_sessionconfig to turn on. Parameter encryption/decryption
64 symmetric-key set to AES-CFB.
65 • --bind-auth=AUTH:
67 Set the authorization value for the bind object.
69 • --tpmkey-context=FILE:
71 Set the tpmkey object. Session parameter encryption is off. Use
73 tpm2_sessionconfig to turn on. Session parameter decryption is off.
74 Use tpm2_sessionconfig to turn on. Parameter encryption/decryption
75 symmetric-key set to AES-CFB.
76 References
79 The type of a context object, whether it is a handle or file name, is
80 determined according to the following logic in-order:
81 • If the argument is a file path, then the file is loaded as a restored
83 TPM transient object.
84 • If the argument is a prefix match on one of:
86 • owner: the owner hierarchy
88 • platform: the platform hierarchy
90 • endorsement: the endorsement hierarchy
92 • lockout: the lockout control persistent object
94 • If the argument argument can be loaded as a number it will be treat
96 as a handle, e.g. 0x81010013 and used directly.OBJECT.
97
99 Authorization for use of an object in TPM2.0 can come in 3 different
100 forms: 1. Password 2. HMAC 3. Sessions
101 NOTE: "Authorizations default to the EMPTY PASSWORD when not speci‐
103 fied".
104 Passwords
106 Passwords are interpreted in the following forms below using prefix
107 identifiers.
108 Note: By default passwords are assumed to be in the string form when
110 they do not have a prefix.
111 String
113 A string password, specified by prefix "str:" or it's absence (raw
114 string without prefix) is not interpreted, and is directly used for au‐
115 thorization.
116 Examples
118 foobar
119 str:foobar
120 Hex-string
122 A hex-string password, specified by prefix "hex:" is converted from a
123 hexidecimal form into a byte array form, thus allowing passwords with
124 non-printable and/or terminal un-friendly characters.
125 Example
127 hex:0x1122334455667788
128 File
130 A file based password, specified be prefix "file:" should be the path
131 of a file containing the password to be read by the tool or a "-" to
132 use stdin. Storing passwords in files prevents information leakage,
133 passwords passed as options can be read from the process list or common
134 shell history features.
135 Examples
137 # to use stdin and be prompted
138 file:-
139 # to use a file from a path
141 file:path/to/password/file
142 # to echo a password via stdin:
144 echo foobar | tpm2_tool -p file:-
145 # to use a bash here-string via stdin:
147 tpm2_tool -p file:- <<< foobar
149 Sessions
151 When using a policy session to authorize the use of an object, prefix
152 the option argument with the session keyword. Then indicate a path to
153 a session file that was created with tpm2_startauthsession(1). Option‐
154 ally, if the session requires an auth value to be sent with the session
155 handle (eg policy password), then append a + and a string as described
156 in the Passwords section.
157 Examples
159 To use a session context file called session.ctx.
160 session:session.ctx
162 To use a session context file called session.ctx AND send the authvalue
164 mypassword.
165 session:session.ctx+mypassword
167 To use a session context file called session.ctx AND send the HEX auth‐
169 value 0x11223344.
170 session:session.ctx+hex:11223344
172 PCR Authorizations
174 You can satisfy a PCR policy using the "pcr:" prefix and the PCR mini‐
175 language. The PCR minilanguage is as follows:
176 <pcr-spec>=<raw-pcr-file>
177 The PCR spec is documented in in the section "PCR bank specifiers".
179 The raw-pcr-file is an optional the output of the raw PCR contents as
181 returned by tpm2_pcrread(1).
182 PCR bank specifiers (common/pcr.md)
184 Examples
186 To satisfy a PCR policy of sha256 on banks 0, 1, 2 and 3 use a specifi‐
187 er of:
188 pcr:sha256:0,1,2,3
190 specifying AUTH.
192
194 This collection of options are common to many programs and provide in‐
195 formation that many users may expect.
196 • -h, --help=[man|no-man]: Display the tools manpage. By default, it
198 attempts to invoke the manpager for the tool, however, on failure
199 will output a short tool summary. This is the same behavior if the
200 "man" option argument is specified, however if explicit "man" is re‐
201 quested, the tool will provide errors from man on stderr. If the
202 "no-man" option if specified, or the manpager fails, the short op‐
203 tions will be output to stdout.
204 To successfully use the manpages feature requires the manpages to be
206 installed or on MANPATH, See man(1) for more details.
207 • -v, --version: Display version information for this tool, supported
209 tctis and exit.
210 • -V, --verbose: Increase the information that the tool prints to the
212 console during its execution. When using this option the file and
213 line number are printed.
214 • -Q, --quiet: Silence normal tool output to stdout.
216 • -Z, --enable-errata: Enable the application of errata fixups. Useful
218 if an errata fixup needs to be applied to commands sent to the TPM.
219 Defining the environment TPM2TOOLS_ENABLE_ERRATA is equivalent. in‐
220 formation many users may expect.
221
223 The TCTI or "Transmission Interface" is the communication mechanism
224 with the TPM. TCTIs can be changed for communication with TPMs across
225 different mediums.
226 To control the TCTI, the tools respect:
228 1. The command line option -T or --tcti
230 2. The environment variable: TPM2TOOLS_TCTI.
232 Note: The command line option always overrides the environment vari‐
234 able.
235 The current known TCTIs are:
237 • tabrmd - The resource manager, called tabrmd
239 (https://github.com/tpm2-software/tpm2-abrmd). Note that tabrmd and
240 abrmd as a tcti name are synonymous.
241 • mssim - Typically used for communicating to the TPM software simula‐
243 tor.
244 • device - Used when talking directly to a TPM device file.
246 • none - Do not initalize a connection with the TPM. Some tools allow
248 for off-tpm options and thus support not using a TCTI. Tools that do
249 not support it will error when attempted to be used without a TCTI
250 connection. Does not support ANY options and MUST BE presented as
251 the exact text of "none".
252 The arguments to either the command line option or the environment
254 variable are in the form:
255 <tcti-name>:<tcti-option-config>
257 Specifying an empty string for either the <tcti-name> or <tcti-op‐
259 tion-config> results in the default being used for that portion respec‐
260 tively.
261 TCTI Defaults
263 When a TCTI is not specified, the default TCTI is searched for using
264 dlopen(3) semantics. The tools will search for tabrmd, device and
265 mssim TCTIs IN THAT ORDER and USE THE FIRST ONE FOUND. You can query
266 what TCTI will be chosen as the default by using the -v option to print
267 the version information. The "default-tcti" key-value pair will indi‐
268 cate which of the aforementioned TCTIs is the default.
269 Custom TCTIs
271 Any TCTI that implements the dynamic TCTI interface can be loaded. The
272 tools internally use dlopen(3), and the raw tcti-name value is used for
273 the lookup. Thus, this could be a path to the shared library, or a li‐
274 brary name as understood by dlopen(3) semantics.
275
277 This collection of options are used to configure the various known TCTI
278 modules available:
279 • device: For the device TCTI, the TPM character device file for use by
281 the device TCTI can be specified. The default is /dev/tpm0.
282 Example: -T device:/dev/tpm0 or export TPM2TOOLS_TCTI="de‐
284 vice:/dev/tpm0"
285 • mssim: For the mssim TCTI, the domain name or IP address and port
287 number used by the simulator can be specified. The default are
288 127.0.0.1 and 2321.
289 Example: -T mssim:host=localhost,port=2321 or export TPM2TOOLS_TC‐
291 TI="mssim:host=localhost,port=2321"
292 • abrmd: For the abrmd TCTI, the configuration string format is a se‐
294 ries of simple key value pairs separated by a ',' character. Each
295 key and value string are separated by a '=' character.
296 • TCTI abrmd supports two keys:
298 1. 'bus_name' : The name of the tabrmd service on the bus (a
300 string).
301 2. 'bus_type' : The type of the dbus instance (a string) limited to
303 'session' and 'system'.
304 Specify the tabrmd tcti name and a config string of bus_name=com.ex‐
306 ample.FooBar:
307 \--tcti=tabrmd:bus_name=com.example.FooBar
309 Specify the default (abrmd) tcti and a config string of bus_type=ses‐
311 sion:
312 \--tcti:bus_type=session
314 NOTE: abrmd and tabrmd are synonymous. the various known TCTI mod‐
316 ules. # EXAMPLES
317 Start a trial session and save the session data to a file
319 tpm2_startauthsession -S mysession.ctx
320 Start a policy session and save the session data to a file
322 tpm2_startauthsession --policy-session -S mysession.ctx
323 Start an encrypted and bound policy session and save the
325 session data to a file
326 tpm2_createprimary -c primary.ctx
328 tpm2_startauthsession --policy-session -c primary.ctx -S mysession.ctx
329
331 Tools can return any of the following codes:
332 • 0 - Success.
334 • 1 - General non-specific error.
336 • 2 - Options handling error.
338 • 3 - Authentication error.
340 • 4 - TCTI related error.
342 • 5 - Non supported scheme. Applicable to tpm2_testparams.
344
346 Github Issues (https://github.com/tpm2-software/tpm2-tools/issues)
347
349 See the Mailing List (https://lists.01.org/mailman/listinfo/tpm2)
350tpm2-tools tpm2_startauthsession(1)