Zeroize `SecretKey` on drop about curve25519-dalek HOT 5 CLOSED

Key data needs to be frequently decoded from inout sources that can’t easily provide mutable references like key file formats (e.g. PKCS#8, OpenSSH)

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We can’t add trait impls for [u8; 32]: it’s just a byte array.

If you want it zeroized, you’ll need to do it yourself. There’s literally nothing this library can do.

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What about using a dedicated type for SecretKey? As users can misuse an array forgetting to zeroize it.

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And where do you get the bytes to make that SecretKey, and how do you ensure those are zeroed? At some point some bytes come into the library externally to what it can manage.

The main way SecretKey is used is as a &SecretKey reference here: https://docs.rs/ed25519-dalek/latest/ed25519_dalek/struct.SigningKey.html#method.from_bytes

Adding a SecretKey newtype would force those bytes to be copied from somewhere else, just so it could manage zeroing them. So it would actually result in an additional copy of the secret being made, which is strictly worse.

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Makes sense, thanks for the explanation. I was looking at SecretKey::try_from_bytes in libp2p that takes mutable reference and zeroes the user provided data after conversion, and though it might be a good idea for library to take care of destroying sensitive data.

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