[Feature request] P256 key in Secure Enclave on iOS

[mattisz]

Nebula has supported P256 keys for a bit and I know mobile_nebula supports imported P256 keys as I have been using them in a self compiled version of the v0.7.0-1.

It would be awesome if there was support for generating P256 keys on the Secure Enclave to use with mobile_nebula (and possibly MacOS in the future if you ever decide to support it).

Not sure if this is on the road map but I would certainly appreciate it and I think it would set mobile_nebula apart from other overlay VPNs in highly regulated environments. Thus, it may provide a bit of a competitive edge on the business side but that's conjecture at this point. Just some food for thought.

[nbrownus]

Currently we store x25519 keys in the enclave but only as an encrypted blob. All crypto operations happen in-process which means the private key is loaded into memory. This is because the enclave does not support x25519 operations.

For P256, we have some more options. The question really comes down to P256 operations in-enclave or in-process?

We could do all operations in the enclave, and nebula has some support for this today, but it's pkcs#11 which Apple does not natively support. Basically it is a bit of a lift to get this working.

For in-process, it would likely be a couple of lines of code change.

I think the best approach is a full in-enclave solution but I am curious what others think.

[mattisz]

If in-process is a quick few lines of code it would be great to get that implemented for feature parity with x25519 keys in the short term. How are P256 keys stored currently?

In the long term, it would be great to see P256 implemented as a full-enclave solution. Most other mesh/overlay VPNs that have gained popularity over the last few years use wireguard under the hood. Nebula's support for P256 sets it apart from wireguard solutions which depend on Curve25519.

If all P256 operations, from key generation onward, happened in-enclave I could see Defined/nebula becoming a viable option for highly regulated private sector industries and government systems. Especially, if you could also support StrongBox on Android for key storage/operations.

As of now, these market segments don't have many options in the overlay VPN space.