NAME
tpm2_pcrread(1) - List PCR values.
SYNOPSIS
tpm2_pcrread [OPTIONS] PCR_LIST_OR_ALG
DESCRIPTION
tpm2_pcrread(1) - Displays PCR values. Without any arguments, tpm2_pcrread(1) outputs all PCRs and their hash banks. One can use specify the hash algorithm or a pcr list as an argument to filter the output.
To only output PCR banks with a given algorithm, specify the hashing algorithm as the argument. Algorithms should follow the “formatting standards”, see section “Algorithm Specifiers”. Also, see section “Supported Hash Algorithms” for a list of supported hash algorithms.
To output a list of PCR banks (sha1, sha256, etc) and ids (0, 1, 2 etc) specify a PCR selection list as the argument as specified via section “PCR Bank Specifiers”.
Also read NOTES section below.
Output is written in a YAML format to stdout, with each algorithm followed by a PCR index and its value. As a simple example assume just sha1 and sha256 support and only 1 PCR. The output would be:
$ tpm2_pcrread sha1:0+sha256:0 sha1 : 0 : 0000000000000000000000000000000000000003 sha256 : 0 : 0000000000000000000000000000000000000000000000000000000000000003
OPTIONS
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-o, --output=FILE: |
The output file to write the PCR values in binary format, optional.
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--cphash=FILE |
File path to record the hash of the command parameters. This is commonly termed as cpHash. NOTE: When this option is selected, The tool will not actually execute the command, it simply returns a cpHash.
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-F, --pcrs_format=FORMAT: |
Format selection for the binary blob in the PCR output file. ’values’ will output a binary blob of the PCR values. ’serialized’ will output a binary blob of the PCR values in the form of serialized data structure in little endian format. Optional. Default is ’values’.
COMMON OPTIONS
This collection of options are common to many programs and provide information that many users may expect.
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-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.
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-v, --version: Display version information for this tool, supported tctis and exit. | ||
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-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. | ||
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-Q, --quiet: Silence normal tool output to stdout. | ||
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-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. | ||
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-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. |
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:
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The command line option -T or --tcti |
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The environment variable: TPM2TOOLS_TCTI. |
Note: The command line option always overrides the environment variable.
The current known TCTIs are:
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tabrmd - The resource manager, called tabrmd (https://github.com/tpm2-software/tpm2-abrmd). Note that tabrmd and abrmd as a tcti name are synonymous. | ||
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mssim - Typically used for communicating to the TPM software simulator. | ||
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device - Used when talking directly to a TPM device file. | ||
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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:
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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”
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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”
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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. |
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TCTI abrmd supports two keys: |
1.
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’bus_name’ : The name of the tabrmd service on the bus (a string). | |||
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’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.
PCR bank specifiers
Supported Hash Algorithms
Supported hash algorithms are:
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0x4 or sha1 for TPM_ALG_SHA1 |
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0xB or sha256 for TPM_ALG_SHA256 (default) |
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0xC or sha384 for TPM_ALG_SHA384 |
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0xD or sha512 for TPM_ALG_SHA512 |
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0x12 or sm3_256 for TPM_ALG_SM3_256 |
NOTE: Your TPM may not support all algorithms.
Algorithm Specifiers
Options that take algorithms support “nice-names”.
There are two major algorithm specification string classes, simple and complex. Only certain algorithms will be accepted by the TPM, based on usage and conditions.
Simple
specifiers
These are strings with no additional specification data.
When creating objects, non-specified portions of an object
are assumed to defaults. You can find the list of known
“Simple Specifiers” below.
Asymmetric
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rsa |
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ecc |
Symmetric
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aes |
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camellia |
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sm4 |
Hashing Algorithms
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sha1 |
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sha256 |
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sha384 |
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sha512 |
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sm3_256 |
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sha3_256 |
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sha3_384 |
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sha3_512 |
Keyed Hash
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hmac |
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xor |
Signing Schemes
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rsassa |
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rsapss |
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ecdsa |
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ecdaa |
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ecschnorr |
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sm2 |
Asymmetric Encryption Schemes
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oaep |
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rsaes |
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ecdh |
Modes
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ctr |
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ofb |
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cbc |
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cfb |
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ecb |
Misc
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null |
Complex
Specifiers
Objects, when specified for creation by the TPM, have
numerous algorithms to populate in the public data. Things
like type, scheme and asymmetric details, key size, etc.
Below is the general format for specifying this data:
<type>:<scheme>:<symmetric-details>
Type
Specifiers
This portion of the complex algorithm specifier is required.
The remaining scheme and symmetric details will default
based on the type specified and the type of the object being
created.
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aes - Default AES: aes128 | ||
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aes128<mode> - 128 bit AES with optional mode (ctr|ofb|cbc|cfb|ecb). If mode is not specified, defaults to null. | ||
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aes192<mode> - Same as aes128<mode>, except for a 192 bit key size. | ||
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aes256<mode> - Same as aes128<mode>, except for a 256 bit key size. | ||
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sm4 - Default SM4: sm4128 | ||
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sm4128 or sm4_128 <mode> - 128 bit SM4 with optional mode (ctr|ofb|cbc|cfb|ecb). If mode is not specified, defaults to null. | ||
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ecc - Elliptical Curve, defaults to ecc256. | ||
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ecc192 or ecc_nist_p192 - 192 bit ECC NIST curve | ||
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ecc224 or ecc_nist_p224 - 224 bit ECC NIST curve | ||
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ecc256 or ecc_nist_p256 - 256 bit ECC NIST curve | ||
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ecc384 or ecc_nist_p384 - 384 bit ECC NIST curve | ||
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ecc521 or ecc_nist_p521 - 521 bit ECC NIST curve | ||
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ecc_sm2 or ecc_sm2_p256 - 256 bit SM2 curve | ||
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rsa - Default RSA: rsa2048 | ||
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rsa1024 - RSA with 1024 bit keysize. | ||
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rsa2048 - RSA with 2048 bit keysize. | ||
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rsa3072 - RSA with 3072 bit keysize. | ||
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rsa4096 - RSA with 4096 bit keysize. |
Scheme
Specifiers
Next, is an optional field, it can be skipped.
Schemes are usually Signing Schemes or Asymmetric Encryption Schemes. Most signing schemes take a hash algorithm directly following the signing scheme. If the hash algorithm is missing, it defaults to sha256. Some take no arguments, and some take multiple arguments.
Hash
Optional Scheme Specifiers
These scheme specifiers are followed by a dash and a valid
hash algorithm, For example: oaep-sha256.
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oaep |
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ecdh |
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rsassa |
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rsapss |
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ecdsa |
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ecschnorr |
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sm2 |
Multiple
Option Scheme Specifiers
This scheme specifier is followed by a count (max size
UINT16) then followed by a dash(-) and a valid hash
algorithm. * ecdaa For example, ecdaa4-sha256. If no count
is specified, it defaults to 4.
No Option
Scheme Specifiers
This scheme specifier takes NO arguments. * rsaes
Symmetric
Details Specifiers
This field is optional, and defaults based on the
type of object being created and it’s
attributes. Generally, any valid Symmetric specifier
from the Type Specifiers list should work. If not
specified, an asymmetric objects symmetric details defaults
to aes128cfb.
Examples
Create an rsa2048 key with an rsaes asymmetric encryption
scheme
tpm2_create -C parent.ctx -G rsa2048:rsaes -u key.pub -r
key.priv
Create an
ecc256 key with an ecdaa signing scheme with a count of 4
and sha384 hash
/tpm2_create -C parent.ctx -G ecc256:ecdaa4-sha384 -u
key.pub -r key.priv
EXAMPLES
Display all PCR values
tpm2_pcrread
Display the PCR values with a specified bank
tpm2_pcrread sha1
Display the PCR values with specified banks and store in a file
tpm2_pcrread -o pcrs sha1:16,17,18+sha256:16,17,18
Display the supported PCR bank algorithms and exit
tpm2_pcrread
NOTES
The maximum number of PCR that can be dumped at once is associated with the maximum length of a bank.
On most TPMs, it means that this tool can dump up to 24 PCRs at once.
Returns
Tools can return any of the following codes:
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0 - Success. | ||
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1 - General non-specific error. | ||
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2 - Options handling error. | ||
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3 - Authentication error. | ||
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4 - TCTI related error. | ||
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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)