tpm2_startauthsession(1) - Start a session with the TPM.

       Authorization for use of an object in TPM2.0 can come in 3 different forms:  1.   Password  2.   HMAC  3.
       Sessions

       NOTE: “Authorizations default to the EMPTYPASSWORD when not specified”.

   Passwords
       Passwords are interpreted in the following forms below using prefix identifiers.

       Note: By default passwords are assumed to be in the string form when they do not have a prefix.

   String
       A  string  password, specified by prefix “str:” or it’s absence (raw string without prefix) is not inter‐
       preted, and is directly used for authorization.

   Examples
              foobar
              str:foobar

   Hex-string
       A hex-string password, specified by prefix “hex:” is converted from a hexidecimal form into a byte  array
       form, thus allowing passwords with non-printable and/or terminal un-friendly characters.

   Example
              hex:1122334455667788

   File
       A  file  based password, specified be prefix “file:” should be the path of a file containing the password
       to be read by the tool or a “-” to use stdin.  Storing passwords in files prevents  information  leakage,
       passwords passed as options can be read from the process list or common shell history features.

   Examples
              # to use stdin and be prompted
              file:-

              # to use a file from a path
              file:path/to/password/file

              # to echo a password via stdin:
              echo foobar | tpm2_tool -p file:-

              # to use a bash here-string via stdin:

              tpm2_tool -p file:- <<< foobar

   Sessions
       When  using  a policy session to authorize the use of an object, prefix the option argument with the ses‐sion keyword.  Then indicate a path to a session file that  was  created  with  tpm2_startauthsession(1).
       Optionally,  if  the  session  requires an auth value to be sent with the session handle (eg policy pass‐
       word), then append a + and a string as described in the Passwords section.

   Examples
       To use a session context file called session.ctx.

              session:session.ctx

       To use a session context file called session.ctxAND send the authvalue mypassword.

              session:session.ctx+mypassword

       To use a session context file called session.ctxAND send the HEX authvalue 0x11223344.

              session:session.ctx+hex:11223344

   PCRAuthorizations
       You can satisfy a PCR policy using the “pcr:” prefix and the PCR minilanguage.  The PCR  minilanguage  is
       as follows: <pcr-spec>=<raw-pcr-file>

       The PCR spec is documented in in the section “PCR bank specifiers”.

       The  raw-pcr-file is an optional argument that contains the output of the raw PCR contents as returned by
       tpm2_pcrread(1).

       PCR bank specifiers

   Examples
       To satisfy a PCR policy of sha256 on banks 0, 1, 2 and 3 use a specifier of:

              pcr:sha256:0,1,2,3

       specifying AUTH.

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

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

       • -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 ac‐
         tivated  if  the  environment  variable TPM2TOOLS_AUTOFLUSH is is set to yes or true.  information many
         users may expect.

       The type of a context object, whether it is a handle or file name, is determined according to the follow‐
       ing 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_.

tpm2_startauthsession(1) - Starts a session with the TPM.  The default is to start a trial session unless
       the -a option is specified.  Saves the policy session data to a file.  This file can then be used in sub‐
       sequent tools that can use a policy file for authorization or policy events.

       This  will  not  work  with  resource managers (RMs) outside of tpm2-abrmd (https://github.com/tpm2-soft‐
       ware/tpm2-abrmd), as most RMs will flush session handles when a client disconnects from the IPC  channel.
       However,  when  using  a RM without the session gapping feature, one can use the command TCTI to keep the
       connection open.

       The first step is to create a socket listener that uses tpm2_send:

              mknod "$HOME/backpipe" p
              while [ 1 ]; do tpm2_send 0<"$HOME/backpipe" | nc -lU "$HOME/sock" 1>"$HOME/backpipe"; done;

       The next step is to use the command TCTI and netcat (nc) to send data to the socket.

              tpm2_startauthsession --tcti="cmd:nc -q 0 -U $HOME/sock" <options>

       When finishing ensure to kill the listener.  For commands executed with the command tcti against the lis‐
       tener, one will need to manage transient handles.  The simplest way is to add a flush after each command:
       tpm2_flushcontext--tcti="cmd:nc-q0-U$HOME/sock"-t

       Note: This example uses UNIX sockets, since the socket is controlled with Linux access controls.  Using a
       port is not recommended as it’s either open to any user on the system (localhost) or bound to  a  network
       card and exposed to the network.

       This  will  work with direct TPM access, but note that internally this calls a ContextSave and a Context‐Load on the session handle, thus the session cannot be saved/loaded again.

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

tpm2-tools                                                                              tpm2_startauthsession(1)

tpm2_startauthsession(1) - Start a session with the TPM.

       • --policy-session:

         Start a policy session of type TPM_SE_POLICY.  Default without this option is TPM_SE_TRIAL.

         NOTE: A trial session is used when building a policy and a policy session is used  when  authenticating
         with a policy.

       • --audit-session:

         Start an HMAC session to be used as an audit session.  Default without this option is TPM2_SE_TRIAL.

       • --hmac-session:

         Start an HMAC session of type TPM_SE_HMAC.  Default without this option is TPM2_SE_TRIAL.

       • -g, --hash-algorithm=ALGORITHM:

         The hash algorithm used in computation of the policy digest.

       • -G, --key-algorithm=ALGORITHM:

         The symmetric algorithm used in parameter encryption/decryption.

       • -c, --key-context=OBJECT:

         Set  the  tpmkey  and bind objects to be the same.  Session parameter encryption is turned on.  Session
         parameter decryption is turned on.  Parameter encryption/decryption symmetric-key set to AES-CFB.

       • -S, --session=FILE:

         The name of the policy session file, required.

       • --bind-context=FILE:

         Set the bind object.  Session parameter encryption is off.  Use tpm2_sessionconfig to turn on.  Session
         parameter decryption is off.  Use tpm2_sessionconfig to turn on.  Parameter encryption/decryption  sym‐
         metric-key set to AES-CFB.

       • --bind-auth=AUTH:

         Set the authorization value for the bind object.

       • --tpmkey-context=FILE:

         Set  the tpmkey object.  Session parameter encryption is off.  Use tpm2_sessionconfig to turn on.  Ses‐
         sion parameter decryption is off.  Use tpm2_sessionconfig to turn on.  Parameter  encryption/decryption
         symmetric-key set to AES-CFB.

       • -n, --name=FILE

         A name file as output from a tool like tpm2_readpublic(1) -n option.  The name file can be used to ver‐ify  a  persistent  handle input for the --tpmkey-context, -c, and --key-context options.  Verification
         that the object referenced by a peristent handle, e.g 0x81000000, is the key expected prevents  attack‐
         ers from performing a man-in-the-middle attack on session traffic.

   References

       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.

tpm2_startauthsession [OPTIONS]

       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  sup‐
         port not using a TCTI.  Tools that do not support it will error when attempted to be used without a TC‐
         TI connection.  Does not support ANY options and MUSTBE 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 be‐
       ing used for that portion respectively.

   TCTIDefaults
       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 INTHATORDER and USETHEFIRSTONEFOUND.  You can query  what
       TCTI  will  be  chosen  as the default by using the -v option to print the version information.  The “de‐
       fault-tcti” key-value pair will indicate which of the aforementioned TCTIs is the default.

   CustomTCTIs
       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.

       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: -Tdevice:/dev/tpm0 or exportTPM2TOOLS_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: -Tmssim:host=localhost,port=2321 or exportTPM2TOOLS_TCTI=“mssim:host=localhost,port=2321”

       • abrmd: For the abrmd TCTI, the configuration string format is a series of simple key value pairs  sepa‐
         rated 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

   Startatrial session and save the session data to a file
              tpm2_startauthsession -S mysession.ctx

   Startapolicy session and save the session data to a file
              tpm2_startauthsession --policy-session -S mysession.ctx

   Startanencryptedandboundpolicy session and save the session data to a file
              tpm2_createprimary -c primary.ctx
              tpm2_startauthsession --policy-session -c primary.ctx -S mysession.ctx