zeroize: Relax Zeroize trait bounds for Vec
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This changes the trait bounds for the `Zeroize` impl on `Vec<Z>` from:
Z: Clone + Default + Zeroize
to just:
Z: Zeroize
This is based on my experience trying to switch `curve25519-dalek` from
`clear_on_drop` to `zeroize` in this PR:
dalek-cryptography/curve25519-dalek#289
Notably there were several places I was unable to use `Zeroizing` in
conjunction with `Vec` because it requires `Clone` and `Default` in
order for the current safe impl of zeroizing the excess capacity in
`Vec`s. IMO this is an implementation detail leaking out which places
undue burden on the user and reduces overall utility.
This is another way of saying: this change effectively reverts #180.
I think we can eventually bring this functionality back using an unsafe
impl which writes zeroes to the excess capacity.
In general my opinion is if you're storing secrets in `Vec`, it's best
to avoid mutating that `Vec` and causing reallocations in the first
place. This is the goal of the `SecretVec` type in `secrecy`:
https://docs.rs/secrecy/latest/secrecy/type.SecretVec.html
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This changes the trait bounds for the
Zeroizeimpl onVec<Z>from:to just:
This is based on my experience trying to switch
curve25519-dalekfromclear_on_droptozeroizein this PR:dalek-cryptography/curve25519-dalek#289
Notably there were several places I was unable to use
Zeroizingin conjunction withVecbecause it requiresCloneandDefaultin order for the current safe impl of zeroizing the excess capacity inVecs. IMO this is an implementation detail leaking out which places undue burden on the user and reduces overall utility.This is another way of saying: this change effectively reverts #180. I think we can eventually bring this functionality back using an
unsafeimpl which writes zeroes to the excess capacity.In general my opinion is if you're storing secrets in
Vec, it's best to avoid mutating thatVecand causing reallocations in the first place. This is the goal of theSecretVectype insecrecy:https://docs.rs/secrecy/latest/secrecy/type.SecretVec.html