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tpm2_changepps(1) General Commands Manual tpm2_changepps(1) NAME tpm2_changepps(1) - Replaces the active platform primary seed with a new one generated off the TPM2 RNG. SYNOPSIS tpm2_changepps [OPTIONS] DESCRIPTION tpm2_changepps(1) - Replaces the active platform primary seed with a new one generated off the TPM2 RNG. The Transient and Persistent ob- jects under the platform hierarchy are lost whilst retaining the NV ob- jects. OPTIONS • -p, --auth specifies the AUTH for the platform. hierarchy. • --cphash=FILE File path to record the hash of the command parameters. This is com- monly termed as cpHash. NOTE: When this option is selected, The tool will not actually execute the command, it simply returns a cpHash, unless rphash is also required. • --rphash=FILE File path to record the hash of the response parameters. This is commonly termed as rpHash. • -S, --session=FILE: The session created using tpm2_startauthsession. This can be used to specify an auxiliary session for auditing and or encryption/decryp- tion of the parameters. References Authorization Formatting 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 EMPTY PASSWORD when not speci- fied". 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 interpreted, and is directly used for au- thorization. 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 session keyword. Then indicate a path to a session file that was created with tpm2_startauthsession(1). Option- ally, if the session requires an auth value to be sent with the session handle (eg policy password), 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.ctx AND send the authvalue mypassword. session:session.ctx+mypassword To use a session context file called session.ctx AND send the HEX auth- value 0x11223344. session:session.ctx+hex:11223344 PCR Authorizations You can satisfy a PCR policy using the "pcr:" prefix and the PCR mini- language. 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 specifi- er of: pcr:sha256:0,1,2,3 specifying AUTH. 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 vari- able. 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 simula- tor. • 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 respective- ly. 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 indi- cate 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 li- brary 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="de- vice:/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_TC- TI="mssim:host=localhost,port=2321" • abrmd: For the abrmd TCTI, the configuration string format is a se- ries 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.ex- ample.FooBar: \--tcti=tabrmd:bus_name=com.example.FooBar Specify the default (abrmd) tcti and a config string of bus_type=ses- sion: \--tcti:bus_type=session NOTE: abrmd and tabrmd are synonymous. the various known TCTI mod- ules. EXAMPLES Change the platform primary seed where the platform auth is NULL. tpm2_changepps 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. Limitations It expects a session to be already established via tpm2_startauthses- sion(1) and requires one of the following: • direct device access • extended session support with tpm2-abrmd. Without it, most resource managers will not save session state between command invocations. BUGS Github Issues (https://github.com/tpm2-software/tpm2-tools/issues) HELP See the Mailing List (https://lists.linuxfoundation.org/mailman/listin- fo/tpm2) tpm2-tools tpm2_changepps(1)
NAME | SYNOPSIS | DESCRIPTION | OPTIONS | Authorization Formatting | TCTI Configuration | TCTI OPTIONS | EXAMPLES | Returns | Limitations | BUGS | HELP
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