tpm2_duplicate - Man Page

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.

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

foobar
str:foobar

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.

hex:1122334455667788

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.

# 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

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.

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

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

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.

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.

• rsa
• ecc

• aes
• camellia
• sm4

• sha1
• sha256
• sha384
• sha512
• sm3_256
• sha3_256
• sha3_384
• sha3_512

• hmac
• xor

• rsassa
• rsapss
• ecdsa
• ecdaa
• ecschnorr
• sm2

• oaep
• rsaes
• ecdh

• ctr
• ofb
• cbc
• cfb
• ecb

• null

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>

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.
• sm4 - Default SM4: sm4128
• sm4128 or sm4_128 <mode> - 128 bit SM4 with optional mode (ctr|ofb|cbc|cfb|ecb). If mode is not specified, defaults to null.
• ecc - Elliptical Curve, defaults to ecc256.
• ecc192 or ecc_nist_p192 - 192 bit ECC NIST curve
• ecc224 or ecc_nist_p224 - 224 bit ECC NIST curve
• ecc256 or ecc_nist_p256 - 256 bit ECC NIST curve
• ecc384 or ecc_nist_p384 - 384 bit ECC NIST curve
• ecc521 or ecc_nist_p521 - 521 bit ECC NIST curve
• ecc_sm2 or ecc_sm2_p256 - 256 bit SM2 curve
• rsa - Default RSA: rsa2048
• rsa1024 - RSA with 1024 bit keysize.
• rsa2048 - RSA with 2048 bit keysize.
• rsa3072 - RSA with 3072 bit keysize.
• rsa4096 - RSA with 4096 bit keysize.

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.

These scheme specifiers are followed by a dash and a valid hash algorithm, For example: oaep-sha256.

• oaep
• ecdh
• rsassa
• rsapss
• ecdsa
• ecschnorr
• sm2

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.

This scheme specifier takes NO arguments. * rsaes

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.

tpm2_create -C parent.ctx -G rsa2048:rsaes -u key.pub -r key.priv

/tpm2_create -C parent.ctx -G ecc256:ecdaa4-sha384 -u key.pub -r key.priv cryptographic algorithms ALGORITHM.

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.

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.

tpm2_startauthsession -S session.dat
tpm2_policycommandcode -S session.dat -L policy.dat TPM2_CC_Duplicate
tpm2_flushcontext session.dat

tpm2_createprimary -C o -g sha256 -G rsa -c primary.ctxt
tpm2_create -C primary.ctxt -g sha256 -G rsa -r key.prv -u key.pub  -c key.ctxt \
-L policy.dat -a "sensitivedataorigin|userwithauth|decrypt|sign"

tpm2_createprimary -C o -g sha256 -G ecc -c new_parent.ctxt

tpm2_startauthsession \--policy-session -S session.dat
tpm2_policycommandcode -S session.dat -L policy.dat TPM2_CC_Duplicate
tpm2_duplicate -C new_parent.ctxt -c key.ctxt -G null -p "session:session.dat" \
-r duprv.bin -s seed.dat
tpm2_flushcontext session.dat

Create a parent object that will be used to wrap/transfer the key.

tpm2_createprimary -C o -g sha256 -G rsa -c primary.ctx

tpm2_create  -C primary.ctx -g sha256 -G rsa \
-r new_parent.prv  -u new_parent.pub \
-a "restricted|sensitivedataorigin|decrypt|userwithauth"

Copy new_parent.pub to TPM-A.

Create root object and auth policy allows duplication only

tpm2_createprimary -C o -g sha256 -G rsa -c primary.ctx

tpm2_startauthsession -S session.dat

tpm2_policycommandcode -S session.dat -L dpolicy.dat TPM2_CC_Duplicate

tpm2_flushcontext session.dat

rm session.dat

Generate an RSA keypair on TPM-A that will be duplicated (note the passphrase is `foo')

tpm2_create -C primary.ctx -g sha256 -G rsa -p foo -r key.prv \
-u key.pub  -L dpolicy.dat -a "sensitivedataorigin|userwithauth|decrypt|sign"

tpm2_load -C primary.ctx -r key.prv -u key.pub -c key.ctx

tpm2_readpublic -c key.ctx -o dup.pub

Test sign and encryption locally (so we can compare later that the same key was transferred).

echo "meet me at.." >file.txt
tpm2_rsaencrypt -c key.ctx  -o data.encrypted file.txt
tpm2_sign -c key.ctx -g sha256 -f plain -p foo -o sign.raw file.txt

Compare the signature hash (we will use this later to confirm the key was transferred to TPM-B):

sha256sum sign.raw

a1b4e3fbaa29e6e46d95cff498150b6b8e7d9fd21182622e8f5a3ddde257879e

Start an auth session and policy command to allow duplication

tpm2_startauthsession --policy-session -S session.dat

tpm2_policycommandcode -S session.dat -L dpolicy.dat TPM2_CC_Duplicate

Load the new_parent.pub file transferred from TPM-B

tpm2_loadexternal -C o -u new_parent.pub -c new_parent.ctx

Start the duplication

tpm2_duplicate -C new_parent.ctx -c key.ctx -G null  \
-p "session:session.dat" -r dup.dpriv -s dup.seed

Copy the following files to TPM-B: * dup.pub * dup.dpriv * dup.seed * (optionally data.encrypted just to test decryption)

Start an auth,policy session

tpm2_startauthsession --policy-session -S session.dat

tpm2_policycommandcode -S session.dat -L dpolicy.dat TPM2_CC_Duplicate

Load the context we used to transfer

tpm2_flushcontext --transient-object

tpm2_load -C primary.ctx -u new_parent.pub -r new_parent.prv -c new_parent.ctx

Import the duplicated context against the parent we used

tpm2_import -C new_parent.ctx -u dup.pub -i dup.dpriv \
-r dup.prv -s dup.seed -L dpolicy.dat

Load the duplicated key context

tpm2_flushcontext --transient-object

tpm2_load -C new_parent.ctx -u dup.pub -r dup.prv -c dup.ctx

Test the imported key matches

• Sign

  echo "meet me at.." >file.txt
  
  tpm2_sign -c dup.ctx -g sha256 -o sig.rss -p foo file.txt
  
  dd if=sig.rss of=sign.raw bs=1 skip=6 count=256

Compare the signature file hash:

$ sha256sum sign.raw

a1b4e3fbaa29e6e46d95cff498150b6b8e7d9fd21182622e8f5a3ddde257879e

• Decryption

  tpm2_flushcontext --transient-object
  
  tpm2_rsadecrypt -p foo -c dup.ctx -o data.ptext data.encrypted
  
  # cat data.ptext 
  meet me at..

To securely send an OpenSSL generated RSA key to a remote TPM such that only that remote TPM will be able to load it, and without exposing the private key to the host operating system on the remote machine:

• On the destination TPM-B, create a primary context and read its public key, then send primary.pub to the source machine:

  tpm2_createprimary -c primary.ctx
  tpm2_readpublic -c primary.ctx -o primary.pub

• On the source machine create the RSA private key and wrap it for the destination TPM’s public key. Similar to tpm2_makecredential, this step should not require a TPM.

  openssl genrsa -out rsa.pem
  tpm2_duplicate -U primary.pub -G rsa -k rsa.pem -u rsa.pub -r rsa.dpriv -s rsa.seed

• Send the rsa.pub, rsa.dpriv and rsa.seed to the destination TPM-B and import the files, which will decrypt them using the primary.ctx to produce rsa.priv, which can then be loaded and used as a TPM key:

  tpm2_import -C primary.ctx -G rsa -i rsa.dpriv -s rsa.seed -u rsa.pub -r rsa.priv
  tpm2_load -C primary.ctx -c rsa.ctx -u rsa.pub -r rsa.priv