Including a null-byte to the OAEP label would allow ssh-rsa keys to be stored inside the TPM.

[Foxboron]

I started hacking a little bit on a TPM plugin for age, and one of the funny quirks is that the OAEP label for the RSA Encryption/Decryption inside the TPM includes a null-byte.

Currently the OAEP label age uses omits this null-byte, but if we consider adding it we could do more fun TPM shenanigans :) age-plugin-yubikey only actually works if the sender and the recipient has this package installed. While a theoretical age-plugin-tpm implementation won't have that restriction as it could work with both ssh keys and a own TPM-formatted key.

To work around this I have a local hack of age so I could that everything works :)

λ age-plugin-tpm » go run ./cmd/age-plugin-tpm --generate --test-tpm
ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQChfam8oCmynxl0vOunhhR1/tTQrXQGY7cn7DncjWCa8QvMGgVK9F+XISUdCN5HLVqMokBrbHw6x80KsX8/N0xw4+ZsQYAkrbGon9HQrObo0Z1sAjO2+/ieKQdGr5v231GhbBmQ7UTbI+6/WUGIqXHRLm9JofJqLUHTRhomJ48EOEzPPeqfzc82fa55BWn0n4h/ZMbdmSwwjL9pugM/5wd95Iq2NodGDGIZg1K2BGCUOpagSkbPiwfLSN6JZieWQR5m5avO9fKrn8WfKSGL0IdAvCn3tz2kOSInbsYqzQtI1cXqNs0/tVx5GVCaURL22zwnedZQolVRSNBqK7IPH72P

λ age-plugin-tpm » go run ./cmd/age-plugin-tpm --list --test-tpm > age-key.txt
λ age-plugin-tpm » echo "itworks" | ../age/age -R ./age-key.txt -o test-decrypt.txt
λ age-plugin-tpm » go run ./cmd/age-plugin-tpm --decrypt --test-tpm
itworks

[Foxboron]

Also, it would be cool that users could just import their existing ssh-keys they use with age into a TPM without actually having to distribute a new key.