1tpm2_policyauthvalue(1)     General Commands Manual    tpm2_policyauthvalue(1)
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NAME

6       tpm2_policyauthvalue(1) - Enables binding a policy to the authorization
7       value of the authorized TPM object.
8

SYNOPSIS

10       tpm2_policyauthvalue [OPTIONS]
11

DESCRIPTION

13       tpm2_policyauthvalue(1) - Enables a policy that requires  the  object’s
14       authentication passphrase be provided.  This is equivalent to authenti‐
15       cating using the object passphrase in plaintext or HMAC.   It  enforces
16       it  as a policy.  It provides a mechanism to allow for password authen‐
17       tication when an object only allows policy based authorization, ie  ob‐
18       ject attribute “userwithauth” is 0.
19

OPTIONS

21-L, --policy=FILE:
22
23         File to save the compounded policy digest.
24
25-S, --session=FILE:
26
27         The  policy  session  file  generated via the -S option to tpm2_star‐
28         tauthsession(1).
29
30--cphash=FILE
31
32         File path to record the hash of the command parameters.  This is com‐
33         monly termed as cpHash.  NOTE: When this option is selected, The tool
34         will not actually execute the command, it simply returns a cpHash.
35
36   References

COMMON OPTIONS

38       This collection of options are common to many programs and provide  in‐
39       formation that many users may expect.
40
41-h,  --help=[man|no-man]:  Display the tools manpage.  By default, it
42         attempts to invoke the manpager for the  tool,  however,  on  failure
43         will  output  a short tool summary.  This is the same behavior if the
44         “man” option argument is specified, however if explicit “man” is  re‐
45         quested,  the  tool  will  provide errors from man on stderr.  If the
46         “no-man” option if specified, or the manpager fails,  the  short  op‐
47         tions will be output to stdout.
48
49         To  successfully use the manpages feature requires the manpages to be
50         installed or on MANPATH, See man(1) for more details.
51
52-v, --version: Display version information for this  tool,  supported
53         tctis and exit.
54
55-V,  --verbose:  Increase the information that the tool prints to the
56         console during its execution.  When using this option  the  file  and
57         line number are printed.
58
59-Q, --quiet: Silence normal tool output to stdout.
60
61-Z, --enable-errata: Enable the application of errata fixups.  Useful
62         if an errata fixup needs to be applied to commands sent to  the  TPM.
63         Defining  the environment TPM2TOOLS_ENABLE_ERRATA is equivalent.  in‐
64         formation many users may expect.
65

TCTI Configuration

67       The TCTI or “Transmission Interface”  is  the  communication  mechanism
68       with  the TPM.  TCTIs can be changed for communication with TPMs across
69       different mediums.
70
71       To control the TCTI, the tools respect:
72
73       1. The command line option -T or --tcti
74
75       2. The environment variable: TPM2TOOLS_TCTI.
76
77       Note: The command line option always overrides  the  environment  vari‐
78       able.
79
80       The current known TCTIs are:
81
82       • tabrmd      -     The     resource     manager,     called     tabrmd
83         (https://github.com/tpm2-software/tpm2-abrmd).  Note that tabrmd  and
84         abrmd as a tcti name are synonymous.
85
86       • mssim  - Typically used for communicating to the TPM software simula‐
87         tor.
88
89       • device - Used when talking directly to a TPM device file.
90
91       • none - Do not initalize a connection with the TPM.  Some tools  allow
92         for off-tpm options and thus support not using a TCTI.  Tools that do
93         not support it will error when attempted to be used  without  a  TCTI
94         connection.   Does  not  support ANY options and MUST BE presented as
95         the exact text of “none”.
96
97       The arguments to either the command  line  option  or  the  environment
98       variable are in the form:
99
100       <tcti-name>:<tcti-option-config>
101
102       Specifying  an  empty  string  for  either the <tcti-name> or <tcti-op‐
103       tion-config> results in the default being used for that portion respec‐
104       tively.
105
106   TCTI Defaults
107       When  a  TCTI  is not specified, the default TCTI is searched for using
108       dlopen(3) semantics.  The tools will  search  for  tabrmd,  device  and
109       mssim  TCTIs  IN THAT ORDER and USE THE FIRST ONE FOUND.  You can query
110       what TCTI will be chosen as the default by using the -v option to print
111       the  version information.  The “default-tcti” key-value pair will indi‐
112       cate which of the aforementioned TCTIs is the default.
113
114   Custom TCTIs
115       Any TCTI that implements the dynamic TCTI interface can be loaded.  The
116       tools internally use dlopen(3), and the raw tcti-name value is used for
117       the lookup.  Thus, this could be a path to the shared library, or a li‐
118       brary name as understood by dlopen(3) semantics.
119

TCTI OPTIONS

121       This collection of options are used to configure the various known TCTI
122       modules available:
123
124device: For the device TCTI, the TPM character device file for use by
125         the device TCTI can be specified.  The default is /dev/tpm0.
126
127         Example:    -T   device:/dev/tpm0   or   export   TPM2TOOLS_TCTI=“de‐
128         vice:/dev/tpm0”
129
130mssim: For the mssim TCTI, the domain name or  IP  address  and  port
131         number  used  by  the  simulator  can  be specified.  The default are
132         127.0.0.1 and 2321.
133
134         Example: -T mssim:host=localhost,port=2321  or  export  TPM2TOOLS_TC‐
135         TI=“mssim:host=localhost,port=2321”
136
137abrmd:  For  the abrmd TCTI, the configuration string format is a se‐
138         ries of simple key value pairs separated by a  `,'  character.   Each
139         key and value string are separated by a `=' character.
140
141         • TCTI abrmd supports two keys:
142
143           1. `bus_name'  :  The  name  of  the  tabrmd  service on the bus (a
144              string).
145
146           2. `bus_type' : The type of the dbus instance (a string) limited to
147              `session' and `system'.
148
149         Specify  the tabrmd tcti name and a config string of bus_name=com.ex‐
150         ample.FooBar:
151
152                \--tcti=tabrmd:bus_name=com.example.FooBar
153
154         Specify the default (abrmd) tcti and a config string of bus_type=ses‐
155         sion:
156
157                \--tcti:bus_type=session
158
159         NOTE:  abrmd  and tabrmd are synonymous.  the various known TCTI mod‐
160         ules.
161

EXAMPLES

163       We want to authenticate using the TPM objects plaintext  authentication
164       value.  While we could authenticate with an ephemeral password session,
165       in this example we will authenticate with the plaintext passphrase in a
166       policy session instead using the tpm2_policyauthvalue(1) tool.
167
168   Create the password policy
169              tpm2_startauthsession -S session.dat
170
171              tpm2_policyauthvalue -S session.dat -L policy.dat
172
173              tpm2_flushcontext session.dat
174
175   Create the object with a passphrase and the password policy
176              tpm2_createprimary -C o -c prim.ctx
177
178              tpm2_create -g sha256 -G aes -u key.pub -r key.priv -C prim.ctx -L policy.dat \
179                -p testpswd
180
181   Authenticate with plaintext passphrase input
182              tpm2_load -C prim.ctx -u key.pub -r key.priv -n key.name -c key.ctx
183
184              echo "plaintext" > plain.txt
185              tpm2_encryptdecrypt -c key.ctx -o encrypt.out plain.txt -p testpswd
186
187   Authenticate with password and the policy
188              tpm2_startauthsession --policy-session -S session.dat
189
190              tpm2_policyauthvalue -S session.dat
191
192              tpm2_encryptdecrypt -c key.ctx -o encrypt.out -p session:session.dat+testpswd \
193              plain.txt
194
195              tpm2_flushcontext session.dat
196

Returns

198       Tools can return any of the following codes:
199
200       • 0 - Success.
201
202       • 1 - General non-specific error.
203
204       • 2 - Options handling error.
205
206       • 3 - Authentication error.
207
208       • 4 - TCTI related error.
209
210       • 5 - Non supported scheme.  Applicable to tpm2_testparams.
211

Limitations

213       It  expects  a session to be already established via tpm2_startauthses‐
214       sion(1) and requires one of the following:
215
216       • direct device access
217
218       • extended session support with tpm2-abrmd.
219
220       Without it, most resource managers will not save session state  between
221       command invocations.
222

BUGS

224       Github Issues (https://github.com/tpm2-software/tpm2-tools/issues)
225

HELP

227       See the Mailing List (https://lists.linuxfoundation.org/mailman/listin
228       fo/tpm2)
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232tpm2-tools                                             tpm2_policyauthvalue(1)
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