Native Secure Enclave backed SSH keys on macOS

Summary

Native Secure Enclave backed ssh keys on MacOS It turns out that MacOS Tahoe can generate and use secure-enclave backed SSH keys! This replaces projects like https://github.com/maxgoedjen/secretive There is a shared library /usr/lib/ssh-keychain.dylib that traditionally has been used to add smartcard support to ssh by implementing PKCS11Provider interface. However since recently it also implements SecurityKeyProivder which supports loading keys directly from the secure enclave! SecurityKeyProvider is what is normally used to talk to FIDO2 devices (e.g. libfido2 can be used to talk to your Yubikey). However you can now use it to talk to your Secure Enclave instead! recording.mov See man sc_auth and man ssh-keychain for all the options To create a Secure Enclave backed key that requires biometrics, run the following command and press TouchID: % sc_auth create-ctk-identity -l ssh -k p-256-ne -t bio You can confirm that the key was create with the list-ctk-identities command: arian@Mac ssh-keychain % sc_auth list-ctk-identities Key Type Public Key Hash Prot Label Common Name Email Address Valid To Valid p-256-ne A71277F0BC5825A7B3576D014F31282A866EF3BC bio ssh ssh 23.11.26, 17:09 YES It also supports listing the ssh key fingerprints instead: % sc_auth list-ctk-identities -t ssh Key Type Public Key Hash Prot Label Common Name Email Address Valid To Valid p-256-ne SHA256:vs4ByYo+T9M3V8iiDYONMSvx2k5Fj2ujVBWt1j6yzis bio ssh ssh 23.11.26, 17:09 YES Keys can be deleted with % sc_auth delete-ctk-identity -h <Public Key Hash> You can "download" the public / private keypair from the secure enclave using the following command: % ssh-keygen -w /usr/lib/ssh-keychain.dylib -K -N "" Enter PIN for authenticator: You may need to touch your authenticator to authorize key download. Saved ECDSA-SK key to id_ecdsa_sk_rk % cat id_ecdsa_sk_rk.pub sk-ecdsa-sha2-nistp256@openssh.com AAAAInNrLWVjZHNhLXNoYTItbmlzdHAyNTZAb3BlbnNzaC5jb20AAAAIbmlzdHAyNTYAAABBBKiHAiAZhcsZ95n85dkNGs9GnbDt0aNOia2gnukn...