NAME

       tpm2_readpublic(1) - Read the public area of a loaded object.

SYNOPSIS

       tpm2_readpublic [OPTIONS]

DESCRIPTION

       tpm2_readpublic(1) - Reads the public area of a loaded object.

OPTIONS

       • -c, --object-context=OBJECT:

         Context object for the object to read.

       • -n, --name=FILE:

         An optional file to save the name structure of the object.

       • -f, --format:

         Format  selection  for  the  public  key output file.  `tss' (the default) will output a
         binary blob according to the TPM  2.0  Specification.   `pem'  will  output  an  OpenSSL
         compatible  PEM encoded public key.  `der' will output an OpenSSL compatible DER encoded
         public key.  `tpmt' will output a binary blob of the TPMT_PUBLIC  struct  referenced  by
         TPM 2.0 specs.

         Public key format.

       • -o, --output=FILE:

         The output file path, recording the public portion of the object.

       • -t, --serialized-handle=HANDLE:

         If  the  object  to be read is a persistent object specified by a raw handle, optionally
         save the serialized handle for use later.  This routine does NOT verify the name of  the
         object  being  read.  Callers should ensure that the contents of name match the expected
         objects name.

       • -q, --qualified-name=FILE:

         Saves the qualified name of the object to FILE.  The qualified name of the object is the
         name  algorithm  hash of the parents qualified and the objects name.  Thus the qualified
         name of the object serves as proof of the objects parents.

   References

Context Object Format

       The type of a context object, whether it is a handle or file name, is determined according
       to the following logic in-order:

       • If  the  argument  is  a  file path, then the file is loaded as a restored TPM transient
         object.

       • If the argument is a prefix match on one of:

         • owner: the owner hierarchy

         • platform: the platform hierarchy

         • endorsement: the endorsement hierarchy

         • lockout: the lockout control persistent object

       • If the argument argument can be loaded as a  number  it  will  be  treat  as  a  handle,
         e.g. 0x81010013 and used directly._OBJECT_.

COMMON OPTIONS

       This  collection  of options are common to many programs and provide information that many
       users may expect.

       • -h, --help=[man|no-man]: Display the tools manpage.  By default, it attempts  to  invoke
         the  manpager  for the tool, however, on failure will output a short tool summary.  This
         is the same behavior if the “man” option argument  is  specified,  however  if  explicit
         “man”  is  requested,  the tool will provide errors from man on stderr.  If the “no-man”
         option if specified, or the manpager fails, the short options will be output to stdout.

         To successfully use the manpages feature requires the manpages to  be  installed  or  on
         MANPATH, See man(1) for more details.

       • -v, --version: Display version information for this tool, supported tctis and exit.

       • -V,  --verbose:  Increase the information that the tool prints to the console during its
         execution.  When using this option the file and line number are printed.

       • -Q, --quiet: Silence normal tool output to stdout.

       • -Z, --enable-errata: Enable the application of errata fixups.  Useful if an errata fixup
         needs   to   be  applied  to  commands  sent  to  the  TPM.   Defining  the  environment
         TPM2TOOLS_ENABLE_ERRATA is equivalent.

       • -R, --autoflush: Enable autoflush for transient objects created by the  command.   If  a
         parent  object  is  loaded  from a context file also the transient parent object will be
         flushed.    Autoflush   can   also   be   activated   if   the   environment    variable
         TPM2TOOLS_AUTOFLUSH is is set to yes or true.  information many users may expect.

TCTI Configuration

       The  TCTI  or “Transmission Interface” is the communication mechanism with the TPM.  TCTIs
       can be changed for communication with TPMs across different mediums.

       To control the TCTI, the tools respect:

       1. The command line option -T or --tcti

       2. The environment variable: TPM2TOOLS_TCTI.

       Note: The command line option always overrides the environment variable.

       The current known TCTIs are:

       • tabrmd        -        The        resource        manager,         called         tabrmd
         (https://github.com/tpm2-software/tpm2-abrmd).   Note  that  tabrmd  and abrmd as a tcti
         name are synonymous.

       • mssim - Typically used for communicating to the TPM software simulator.

       • device - Used when talking directly to a TPM device file.

       • none - Do not initalize a connection with the TPM.  Some tools allow for off-tpm options
         and  thus  support  not  using  a  TCTI.   Tools  that do not support it will error when
         attempted to be used without a TCTI connection.  Does not support ANY options  and  MUST
         BE presented as the exact text of “none”.

       The  arguments  to  either  the command line option or the environment variable are in the
       form:

       <tcti-name>:<tcti-option-config>

       Specifying an empty string for either the <tcti-name> or <tcti-option-config>  results  in
       the default being used for that portion respectively.

   TCTI Defaults
       When  a TCTI is not specified, the default TCTI is searched for using dlopen(3) semantics.
       The tools will search for tabrmd, device and mssim TCTIs IN THAT ORDER and USE  THE  FIRST
       ONE  FOUND.   You can query what TCTI will be chosen as the default by using the -v option
       to print the version information.  The “default-tcti” key-value pair will  indicate  which
       of the aforementioned TCTIs is the default.

   Custom TCTIs
       Any  TCTI  that implements the dynamic TCTI interface can be loaded.  The tools internally
       use dlopen(3), and the raw tcti-name value is used for the lookup.  Thus, this could be  a
       path to the shared library, or a library name as understood by dlopen(3) semantics.

TCTI OPTIONS

       This collection of options are used to configure the various known TCTI modules available:

       • device:  For  the  device TCTI, the TPM character device file for use by the device TCTI
         can be specified.  The default is /dev/tpm0.

         Example: -T device:/dev/tpm0 or export TPM2TOOLS_TCTI=“device:/dev/tpm0”

       • mssim: For the mssim TCTI, the domain name or IP address and port  number  used  by  the
         simulator can be specified.  The default are 127.0.0.1 and 2321.

         Example:          -T          mssim:host=localhost,port=2321          or          export
         TPM2TOOLS_TCTI=“mssim:host=localhost,port=2321”

       • abrmd: For the abrmd TCTI, the configuration string format is a  series  of  simple  key
         value  pairs separated by a `,' character.  Each key and value string are separated by a
         `=' character.

         • TCTI abrmd supports two keys:

           1. `bus_name' : The name of the tabrmd service on the bus (a string).

           2. `bus_type' : The type of the dbus instance (a  string)  limited  to  `session'  and
              `system'.

         Specify the tabrmd tcti name and a config string of bus_name=com.example.FooBar:

                \--tcti=tabrmd:bus_name=com.example.FooBar

         Specify the default (abrmd) tcti and a config string of bus_type=session:

                \--tcti:bus_type=session

         NOTE: abrmd and tabrmd are synonymous.  the various known TCTI modules.  # EXAMPLES

   Create a primary object and read the public structure in an openssl compliant format
              tpm2_createprimary -c primary.ctx
              tpm2_readpublic -c primary.ctx -o output.dat -f pem

   Serialize an existing persistent object handle to disk for later use
       This  work-flow is primarily intended for existing persistent TPM objects.  This work-flow
       does not verify that the name of the serialized object matches the expected, and thus  the
       serialized handle could be pointing to an attacker controlled object if no verification is
       done.  If you are creating an object from scratch, save the serialized handle when  making
       the object persistent.

       We assume that an object has already been persisted, for example via:

              # We assume that an object has already been persisted, for example
              tpm2_createprimary -c primary.ctx

              # context files have all the information for the TPM to verify the object
              tpm2_evictcontrol -c primary.ctx
              persistent-handle: 0x81000001
              action: persisted

       Next use the persistent handle to get a serialized handle:

              # The persistent handle output could be at an attacker controlled object,
              # best practice is to use the option "-o: for tpm2_evictcontrol to get a
              # serialized handle instead.

              tpm2_readpublic -c 0x81000001 -o output.dat -f pem -t primary.handle

              # use this verified handle in an encrypted session with the tpm
              tpm2_startauthsession --policy-session -S session.ctx -c primary.handle

       For new objects, its best to use all serialized handles.

Returns

       Tools can return any of the following codes:

       • 0 - Success.

       • 1 - General non-specific error.

       • 2 - Options handling error.

       • 3 - Authentication error.

       • 4 - TCTI related error.

       • 5 - Non supported scheme.  Applicable to tpm2_testparams.

BUGS

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

HELP

       See the Mailing List (https://lists.linuxfoundation.org/mailman/listinfo/tpm2)