References¶

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 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:0x1122334455667788
    

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). Optionally, 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 authvalue 0x11223344.

session:session.ctx+hex:11223344
    

PCR Authorizations¶

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 (pcr.md)

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.

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¶

•

rsa

•

ecc

Symmetric¶

•

aes

•

camellia

Hashing Algorithms¶

•

sha1

•

sha256

•

sha384

•

sha512

•

sm3_256

•

sha3_256

•

sha3_384

•

sha3_512

Keyed Hash¶

•

hmac

•

xor

Signing Schemes¶

•

rsassa

•

rsapss

•

ecdsa

•

ecdaa

•

ecschnorr

Asymmetric Encryption Schemes¶

•

oaep

•

rsaes

•

ecdh

Modes¶

•

ctr

•

ofb

•

cbc

•

cfb

•

ecb

Misc¶

•

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.

•

aes - Default AES: aes128

•

aes128<mode> - 128 bit AES with optional mode (ctr|ofb|cbc|cfb|ecb). If mode is not specified, defaults to null.

•

aes192<mode> - Same as aes128<mode>, except for a 192 bit key size.

•

aes256<mode> - Same as aes128<mode>, except for a 256 bit key size.

•

ecc - Elliptical Curve, defaults to ecc256.

•

ecc192 - 192 bit ECC

•

ecc224 - 224 bit ECC

•

ecc256 - 256 bit ECC

•

ecc384 - 384 bit ECC

•

ecc521 - 521 bit ECC

•

rsa - Default RSA: rsa2048

•

rsa1024 - RSA with 1024 bit keysize.

•

rsa2048 - RSA with 2048 bit keysize.

•

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.

•

oaep

•

ecdh

•

rsassa

•

rsapss

•

ecdsa

•

ecschnorr

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 cryptographic algorithms ALGORITHM.

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.

Sign and verify with the TPM using the endorsement hierarchy¶

tpm2_createprimary -C e -c primary.ctx
tpm2_create -G rsa -u rsa.pub -r rsa.priv -C primary.ctx
tpm2_load -C primary.ctx -u rsa.pub -r rsa.priv -c rsa.ctx
echo "my message" > message.dat
tpm2_sign -c rsa.ctx -g sha256 -o sig.rssa message.dat
tpm2_verifysignature -c rsa.ctx -g sha256 -s sig.rssa -m message.dat
    

Sign with the TPM and verify with OSSL¶

openssl ecparam -name prime256v1 -genkey -noout -out private.ecc.pem
openssl ec -in private.ecc.pem -out public.ecc.pem -pubout
# Generate a hash to sign
echo "data to sign" > data.in.raw
sha256sum data.in.raw | awk '{ print "000000 " $1 }' | \
xxd -r -c 32 > data.in.digest
# Load the private key for signing
tpm2_loadexternal -Q -G ecc -r private.ecc.pem -c key.ctx
# Sign in the TPM and verify with OSSL
tpm2_sign -Q -c key.ctx -g sha256 -d -f plain -o data.out.signed data.in.digest
openssl dgst -verify public.ecc.pem -keyform pem -sha256 \
-signature data.out.signed data.in.raw