AES key injection

Nitrokeys HSM
1

I apologize is this has been discussed already but I would like to clarify how to inject AES key inside Nitrokey HSM2 with pkcs11-tool (if that is doable).

From previous discussions here I understand that a direct object creation (pkcs11-tool –write-object) is not supported.

I have tried an alternative approach using an RSA wrapping key and the RSA-OAEP mechanism, but that did not work either, resulting in CKR_GENERAL_ERROR.

First create an RSA key for wrapping :

pkcs11-tool --login --login-type user --pin 648219 --keypairgen --mechanism RSA-PKCS-KEY-PAIR-GEN --key-type RSA:2048 --id 57524150 --label ‘Wrapping key’ --usage-wrap --usage-decrypt

Then extract the public key and convert to PEM :

pkcs11-tool --login --login-type user --pin 648219 --read-object --id 57524150 --type pubkey --output-file wrapping_key.pub
openssl rsa -pubin -inform DER -in wrapping_key.pub -outform PEM -out wrapping_key.pem

Finally perform OAEP wrapping of the plaintext secret (16 bytes) :

openssl pkeyutl -encrypt -in AES.key -inkey wrapping_key.pem -pubin -pkeyopt rsa_padding_mode:oaep -pkeyopt rsa_oaep_md:sha1 -pkeyopt rsa_mgf1_md:sha1

pkcs11-tool --login --login-type user --pin 648219 --unwrap --mechanism RSA-PKCS-OAEP --hash-algorithm SHA-1 --mgf MGF1-SHA1 --id 57524150 -i wrapped_secret.bin --key-type AES:16 --application-id 414553 --application-label 'AES key'

which results in

error: PKCS11 function C_UnwrapKey failed: rv = CKR_GENERAL_ERROR (0x5)

I am suspicious that I might have to add a template around the wrapped key raw value, is that the case ? What would be the format then ?

This all assuming the unwrap is supported by the card. Maybe pkcs11-tool isn’t the right tool for this job.

2

You can not use pkcs11-tool to import an existing AES key into a SmartCard-HSM / Nitrokey-HSM. You have to use the Smart Card Shell to do that.

The reason is, that the HSM does not support the import of plain key material for security reasons. You must use a Key Domain for that and prepare the AES key by wrapping it with the DKEK.

The Key Manager in the Smart Card Shell has a convenience function to do the wrapping and import after presenting the DKEK share.