% tpm2_duplicate(1) tpm2-tools | General Commands Manual

NAME

tpm2_duplicate(1) - Duplicates a loaded object so that it may be used in a different hierarchy.

SYNOPSIS

tpm2_duplicate [OPTIONS]

DESCRIPTION

tpm2_duplicate(1) - This tool duplicates a loaded object so that it may be used in a different hierarchy. The new parent key for the duplicate may be on the same or different TPM or TPM_RH_NULL.

OPTIONS

These options control the key importation process:

-G, --wrapper-algorithm=ALGORITHM:

The symmetric algorithm to be used for the inner wrapper. Supports: * aes - AES 128 in CFB mode. * null - none
-i, --encryptionkey-in=FILE:

Specifies the filename of the symmetric key (128 bit data) to be used for the inner wrapper. Valid only when specified symmetric algorithm is not null
-o, --encryptionkey-out=FILE:

Specifies the filename to store the symmetric key (128 bit data) that was used for the inner wrapper. Valid only when specified symmetric algorithm is not null and --input-key-file is not specified. The TPM generates the key in this case.
-C, --parent-context=OBJECT:

The parent key object.
-U, --parent-public=FILE:

Specifies the file path to the public key of the parent object on the destination TPM. This should be a TPM2B_PUBLIC formatted file.
-k, --private-key=FILE:

Specifies the file path to the external private key be encrypted for the remote TPM. This should be a PEM format private key.
-r, --private=FILE:

Specifies the file path to save the private portion of the duplicated object. protection details
-u, --public=FILE:

Specifies the file path to save the public portion of the duplicated object, if an external key is being duplicated.
-s, --encrypted-seed=FILE:

The file to save the encrypted seed of the duplicated object.
-p, --auth=AUTH:

The authorization value for the key, optional.
-L, --policy=FILE:

The input policy file, optional.
-c, --key-context=OBJECT:

The object to be duplicated.
--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.

References

context object format details the methods for specifying OBJECT.

authorization formatting details the methods for specifying AUTH.

algorithm specifiers details the options for specifying cryptographic algorithms ALGORITHM.

common options collection of common options that provide information many users may expect.

common tcti options collection of options used to configure the various known TCTI modules.

EXAMPLES

Example-1: Duplicate a key created with a policy that allows for duplication:

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

Example-2: As an end-to-end example, the following will transfer an RSA key generated on `TPM-A` to `TPM-B`

On TPM-B

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.

On 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)

On TPM-B

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..

Example-3: Exporting an OpenSSL RSA key for a remote TPM

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

returns

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NAME

SYNOPSIS

DESCRIPTION

OPTIONS

References

EXAMPLES

Example-1: Duplicate a key created with a policy that allows for duplication:

Example-2: As an end-to-end example, the following will transfer an RSA key generated on TPM-A to TPM-B

On TPM-B

On TPM-A

On TPM-B

Example-3: Exporting an OpenSSL RSA key for a remote TPM

Example-2: As an end-to-end example, the following will transfer an RSA key generated on `TPM-A` to `TPM-B`