1tpm2_readpublic(1) General Commands Manual tpm2_readpublic(1)
2
6 tpm2_readpublic(1) - Read the public area of a loaded object.
7
9 tpm2_readpublic [OPTIONS]
10
12 tpm2_readpublic(1) - Reads the public area of a loaded object.
13
15 • -c, --object-context=OBJECT:
16 Context object for the object to read.
18 • -n, --name=FILE:
20 An optional file to save the name structure of the object.
22 • -f, --format:
24 Format selection for the public key output file. `tss' (the default)
26 will output a binary blob according to the TPM 2.0 Specification.
27 `pem' will output an OpenSSL compatible PEM encoded public key.
28 `der' will output an OpenSSL compatible DER encoded public key.
29 `tpmt' will output a binary blob of the TPMT_PUBLIC struct referenced
30 by TPM 2.0 specs.
31 Public key format.
33 • -o, --output=FILE:
35 The output file path, recording the public portion of the object.
37 • -t, --serialized-handle=HANDLE:
39 If the object to be read is a persistent object specified by a raw
41 handle, optionally save the serialized handle for use later. This
42 routine does NOT verify the name of the object being read. Callers
43 should ensure that the contents of name match the expected objects
44 name.
45 • -q, --qualified-name=FILE:
47 Saves the qualified name of the object to FILE. The qualified name
49 of the object is the name algorithm hash of the parents qualified and
50 the objects name. Thus the qualified name of the object serves as
51 proof of the objects parents.
52 References
55 The type of a context object, whether it is a handle or file name, is
56 determined according to the following logic in-order:
57 • If the argument is a file path, then the file is loaded as a restored
59 TPM transient object.
60 • If the argument is a prefix match on one of:
62 • owner: the owner hierarchy
64 • platform: the platform hierarchy
66 • endorsement: the endorsement hierarchy
68 • lockout: the lockout control persistent object
70 • If the argument argument can be loaded as a number it will be treat
72 as a handle, e.g. 0x81010013 and used directly._OBJECT_.
73
75 This collection of options are common to many programs and provide in‐
76 formation that many users may expect.
77 • -h, --help=[man|no-man]: Display the tools manpage. By default, it
79 attempts to invoke the manpager for the tool, however, on failure
80 will output a short tool summary. This is the same behavior if the
81 “man” option argument is specified, however if explicit “man” is re‐
82 quested, the tool will provide errors from man on stderr. If the
83 “no-man” option if specified, or the manpager fails, the short op‐
84 tions will be output to stdout.
85 To successfully use the manpages feature requires the manpages to be
87 installed or on MANPATH, See man(1) for more details.
88 • -v, --version: Display version information for this tool, supported
90 tctis and exit.
91 • -V, --verbose: Increase the information that the tool prints to the
93 console during its execution. When using this option the file and
94 line number are printed.
95 • -Q, --quiet: Silence normal tool output to stdout.
97 • -Z, --enable-errata: Enable the application of errata fixups. Useful
99 if an errata fixup needs to be applied to commands sent to the TPM.
100 Defining the environment TPM2TOOLS_ENABLE_ERRATA is equivalent. in‐
101 formation many users may expect.
102
104 The TCTI or “Transmission Interface” is the communication mechanism
105 with the TPM. TCTIs can be changed for communication with TPMs across
106 different mediums.
107 To control the TCTI, the tools respect:
109 1. The command line option -T or --tcti
111 2. The environment variable: TPM2TOOLS_TCTI.
113 Note: The command line option always overrides the environment vari‐
115 able.
116 The current known TCTIs are:
118 • tabrmd - The resource manager, called tabrmd
120 (https://github.com/tpm2-software/tpm2-abrmd). Note that tabrmd and
121 abrmd as a tcti name are synonymous.
122 • mssim - Typically used for communicating to the TPM software simula‐
124 tor.
125 • device - Used when talking directly to a TPM device file.
127 • none - Do not initalize a connection with the TPM. Some tools allow
129 for off-tpm options and thus support not using a TCTI. Tools that do
130 not support it will error when attempted to be used without a TCTI
131 connection. Does not support ANY options and MUST BE presented as
132 the exact text of “none”.
133 The arguments to either the command line option or the environment
135 variable are in the form:
136 <tcti-name>:<tcti-option-config>
138 Specifying an empty string for either the <tcti-name> or <tcti-op‐
140 tion-config> results in the default being used for that portion respec‐
141 tively.
142 TCTI Defaults
144 When a TCTI is not specified, the default TCTI is searched for using
145 dlopen(3) semantics. The tools will search for tabrmd, device and
146 mssim TCTIs IN THAT ORDER and USE THE FIRST ONE FOUND. You can query
147 what TCTI will be chosen as the default by using the -v option to print
148 the version information. The “default-tcti” key-value pair will indi‐
149 cate which of the aforementioned TCTIs is the default.
150 Custom TCTIs
152 Any TCTI that implements the dynamic TCTI interface can be loaded. The
153 tools internally use dlopen(3), and the raw tcti-name value is used for
154 the lookup. Thus, this could be a path to the shared library, or a li‐
155 brary name as understood by dlopen(3) semantics.
156
158 This collection of options are used to configure the various known TCTI
159 modules available:
160 • device: For the device TCTI, the TPM character device file for use by
162 the device TCTI can be specified. The default is /dev/tpm0.
163 Example: -T device:/dev/tpm0 or export TPM2TOOLS_TCTI=“de‐
165 vice:/dev/tpm0”
166 • mssim: For the mssim TCTI, the domain name or IP address and port
168 number used by the simulator can be specified. The default are
169 127.0.0.1 and 2321.
170 Example: -T mssim:host=localhost,port=2321 or export TPM2TOOLS_TC‐
172 TI=“mssim:host=localhost,port=2321”
173 • abrmd: For the abrmd TCTI, the configuration string format is a se‐
175 ries of simple key value pairs separated by a `,' character. Each
176 key and value string are separated by a `=' character.
177 • TCTI abrmd supports two keys:
179 1. `bus_name' : The name of the tabrmd service on the bus (a
181 string).
182 2. `bus_type' : The type of the dbus instance (a string) limited to
184 `session' and `system'.
185 Specify the tabrmd tcti name and a config string of bus_name=com.ex‐
187 ample.FooBar:
188 \--tcti=tabrmd:bus_name=com.example.FooBar
190 Specify the default (abrmd) tcti and a config string of bus_type=ses‐
192 sion:
193 \--tcti:bus_type=session
195 NOTE: abrmd and tabrmd are synonymous. the various known TCTI mod‐
197 ules. # EXAMPLES
198 Create a primary object and read the public structure in an openssl compli‐
200 ant format
201 tpm2_createprimary -c primary.ctx
202 tpm2_readpublic -c primary.ctx -o output.dat -f pem
203 Serialize an existing persistent object handle to disk for later use
205 This work-flow is primarily intended for existing persistent TPM ob‐
206 jects. This work-flow does not verify that the name of the serialized
207 object matches the expected, and thus the serialized handle could be
208 pointing to an attacker controlled object if no verification is done.
209 If you are creating an object from scratch, save the serialized handle
210 when making the object persistent.
211 We assume that an object has already been persisted, for example via:
213 # We assume that an object has already been persisted, for example
215 tpm2_createprimary -c primary.ctx
216 # context files have all the information for the TPM to verify the object
218 tpm2_evictcontrol -c primary.ctx
219 persistent-handle: 0x81000001
220 action: persisted
221 Next use the persistent handle to get a serialized handle:
223 # The persistent handle output could be at an attacker controlled object,
225 # best practice is to use the option "-o: for tpm2_evictcontrol to get a
226 # serialized handle instead.
227 tpm2_readpublic -c 0x81000001 -o output.dat -f pem -t primary.handle
229 # use this verified handle in an encrypted session with the tpm
231 tpm2_startauthsession --policy-session -S session.ctx -c primary.handle
232 For new objects, its best to use all serialized handles.
234
236 Tools can return any of the following codes:
237 • 0 - Success.
239 • 1 - General non-specific error.
241 • 2 - Options handling error.
243 • 3 - Authentication error.
245 • 4 - TCTI related error.
247 • 5 - Non supported scheme. Applicable to tpm2_testparams.
249
251 Github Issues (https://github.com/tpm2-software/tpm2-tools/issues)
252
254 See the Mailing List (https://lists.linuxfoundation.org/mailman/listin‐
255 fo/tpm2)
256tpm2-tools tpm2_readpublic(1)