1tpm2_startauthsession(1) General Commands Manual tpm2_startauthsession(1)
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6 tpm2_startauthsession(1) - Start a session with the TPM.
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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. NOTE: A trial session is used when building
31 a policy and a policy session is used when authenticating with a pol‐
32 icy.
33 · -g, --hash-algorithm=ALGORITHM:
35 The hash algorithm used in computation of the policy digest.
37 · -c, --key-context=OBJECT:
39 Set the session encryption and bind key. When using this, sensitive
41 data transmitted to the TPM will be encrypted with AES128CFB. This
42 prevents bus snooping attacks.
43 · -S, --session=FILE:
45 The name of the policy session file, required.
47 References
50 The type of a context object, whether it is a handle or file name, is
51 determined according to the following logic in-order:
52 · If the argument is a file path, then the file is loaded as a restored
54 TPM transient object.
55 · If the argument is a prefix match on one of:
57 · owner: the owner hierarchy
59 · platform: the platform hierarchy
61 · endorsement: the endorsement hierarchy
63 · lockout: the lockout control persistent object
65 · If the argument argument can be loaded as a number it will be treat
67 as a handle, e.g. 0x81010013 and used directly.OBJECT.
68
70 Authorization for use of an object in TPM2.0 can come in 3 different
71 forms: 1. Password 2. HMAC 3. Sessions
72 NOTE: "Authorizations default to the EMPTY PASSWORD when not speci‐
74 fied".
75 Passwords
77 Passwords are interpreted in the following forms below using prefix
78 identifiers.
79 Note: By default passwords are assumed to be in the string form when
81 they do not have a prefix.
82 String
84 A string password, specified by prefix "str:" or it's absence (raw
85 string without prefix) is not interpreted, and is directly used for au‐
86 thorization.
87 Examples
89 foobar
90 str:foobar
91 Hex-string
93 A hex-string password, specified by prefix "hex:" is converted from a
94 hexidecimal form into a byte array form, thus allowing passwords with
95 non-printable and/or terminal un-friendly characters.
96 Example
98 hex:0x1122334455667788
99 File
101 A file based password, specified be prefix "file:" should be the path
102 of a file containing the password to be read by the tool or a "-" to
103 use stdin. Storing passwords in files prevents information leakage,
104 passwords passed as options can be read from the process list or common
105 shell history features.
106 Examples
108 # to use stdin and be prompted
109 file:-
110 # to use a file from a path
112 file:path/to/password/file
113 # to echo a password via stdin:
115 echo foobar | tpm2_tool -p file:-
116 # to use a bash here-string via stdin:
118 tpm2_tool -p file:- <<< foobar
120 Sessions
122 When using a policy session to authorize the use of an object, prefix
123 the option argument with the session keyword. Then indicate a path to
124 a session file that was created with tpm2_startauthsession(1). Option‐
125 ally, if the session requires an auth value to be sent with the session
126 handle (eg policy password), then append a + and a string as described
127 in the Passwords section.
128 Examples
130 To use a session context file called session.ctx.
131 session:session.ctx
133 To use a session context file called session.ctx AND send the authvalue
135 mypassword.
136 session:session.ctx+mypassword
138 To use a session context file called session.ctx AND send the HEX auth‐
140 value 0x11223344.
141 session:session.ctx+hex:11223344
143 PCR Authorizations
145 You can satisfy a PCR policy using the "pcr:" prefix and the PCR mini‐
146 language. The PCR minilanguage is as follows:
147 <pcr-spec>=<raw-pcr-file>
148 The PCR spec is documented in in the section "PCR bank specifiers".
150 The raw-pcr-file is an optional the output of the raw PCR contents as
152 returned by tpm2_pcrread(1).
153 PCR bank specifiers (common/pcr.md)
155 Examples
157 To satisfy a PCR policy of sha256 on banks 0, 1, 2 and 3 use a specifi‐
158 er of:
159 pcr:sha256:0,1,2,3
161 specifying AUTH.
163
165 This collection of options are common to many programs and provide in‐
166 formation that many users may expect.
167 · -h, --help=[man|no-man]: Display the tools manpage. By default, it
169 attempts to invoke the manpager for the tool, however, on failure
170 will output a short tool summary. This is the same behavior if the
171 "man" option argument is specified, however if explicit "man" is re‐
172 quested, the tool will provide errors from man on stderr. If the
173 "no-man" option if specified, or the manpager fails, the short op‐
174 tions will be output to stdout.
175 To successfully use the manpages feature requires the manpages to be
177 installed or on MANPATH, See man(1) for more details.
178 · -v, --version: Display version information for this tool, supported
180 tctis and exit.
181 · -V, --verbose: Increase the information that the tool prints to the
183 console during its execution. When using this option the file and
184 line number are printed.
185 · -Q, --quiet: Silence normal tool output to stdout.
187 · -Z, --enable-errata: Enable the application of errata fixups. Useful
189 if an errata fixup needs to be applied to commands sent to the TPM.
190 Defining the environment TPM2TOOLS_ENABLE_ERRATA is equivalent. in‐
191 formation many users may expect.
192
194 The TCTI or "Transmission Interface" is the communication mechanism
195 with the TPM. TCTIs can be changed for communication with TPMs across
196 different mediums.
197 To control the TCTI, the tools respect:
199 1. The command line option -T or --tcti
201 2. The environment variable: TPM2TOOLS_TCTI.
203 Note: The command line option always overrides the environment vari‐
205 able.
206 The current known TCTIs are:
208 · tabrmd - The resource manager, called tabrmd
210 (https://github.com/tpm2-software/tpm2-abrmd). Note that tabrmd and
211 abrmd as a tcti name are synonymous.
212 · mssim - Typically used for communicating to the TPM software simula‐
214 tor.
215 · device - Used when talking directly to a TPM device file.
217 · none - Do not initalize a connection with the TPM. Some tools allow
219 for off-tpm options and thus support not using a TCTI. Tools that do
220 not support it will error when attempted to be used without a TCTI
221 connection. Does not support ANY options and MUST BE presented as
222 the exact text of "none".
223 The arguments to either the command line option or the environment
225 variable are in the form:
226 <tcti-name>:<tcti-option-config>
228 Specifying an empty string for either the <tcti-name> or <tcti-op‐
230 tion-config> results in the default being used for that portion respec‐
231 tively.
232 TCTI Defaults
234 When a TCTI is not specified, the default TCTI is searched for using
235 dlopen(3) semantics. The tools will search for tabrmd, device and
236 mssim TCTIs IN THAT ORDER and USE THE FIRST ONE FOUND. You can query
237 what TCTI will be chosen as the default by using the -v option to print
238 the version information. The "default-tcti" key-value pair will indi‐
239 cate which of the aforementioned TCTIs is the default.
240 Custom TCTIs
242 Any TCTI that implements the dynamic TCTI interface can be loaded. The
243 tools internally use dlopen(3), and the raw tcti-name value is used for
244 the lookup. Thus, this could be a path to the shared library, or a li‐
245 brary name as understood by dlopen(3) semantics.
246
248 This collection of options are used to configure the various known TCTI
249 modules available:
250 · device: For the device TCTI, the TPM character device file for use by
252 the device TCTI can be specified. The default is /dev/tpm0.
253 Example: -T device:/dev/tpm0 or export TPM2TOOLS_TCTI="de‐
255 vice:/dev/tpm0"
256 · mssim: For the mssim TCTI, the domain name or IP address and port
258 number used by the simulator can be specified. The default are
259 127.0.0.1 and 2321.
260 Example: -T mssim:host=localhost,port=2321 or export TPM2TOOLS_TC‐
262 TI="mssim:host=localhost,port=2321"
263 · abrmd: For the abrmd TCTI, the configuration string format is a se‐
265 ries of simple key value pairs separated by a ',' character. Each
266 key and value string are separated by a '=' character.
267 · TCTI abrmd supports two keys:
269 1. 'bus_name' : The name of the tabrmd service on the bus (a
271 string).
272 2. 'bus_type' : The type of the dbus instance (a string) limited to
274 'session' and 'system'.
275 Specify the tabrmd tcti name and a config string of bus_name=com.ex‐
277 ample.FooBar:
278 \--tcti=tabrmd:bus_name=com.example.FooBar
280 Specify the default (abrmd) tcti and a config string of bus_type=ses‐
282 sion:
283 \--tcti:bus_type=session
285 NOTE: abrmd and tabrmd are synonymous. the various known TCTI mod‐
287 ules. # EXAMPLES
288 Start a trial session and save the session data to a file
290 tpm2_startauthsession -S mysession.ctx
291 Start a policy session and save the session data to a file
293 tpm2_startauthsession --policy-session -S mysession.ctx
294 Start an encrypted and bound policy session and save the
296 session data to a file
297 tpm2_createprimary -c primary.ctx
299 tpm2_startauthsession --policy-session -c primary.ctx -S mysession.ctx
300
302 Tools can return any of the following codes:
303 · 0 - Success.
305 · 1 - General non-specific error.
307 · 2 - Options handling error.
309 · 3 - Authentication error.
311 · 4 - TCTI related error.
313 · 5 - Non supported scheme. Applicable to tpm2_testparams.
315
317 Github Issues (https://github.com/tpm2-software/tpm2-tools/issues)
318
320 See the Mailing List (https://lists.01.org/mailman/listinfo/tpm2)
321tpm2-tools tpm2_startauthsession(1)