zeroize Vec's capacity() by extending #180
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Needs rustfmt, otherwise thanks, this looks good |
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Thanks! |
tarcieri
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Oct 13, 2019
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
tarcieri
pushed a commit
that referenced
this pull request
Oct 13, 2019
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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Fixes #178.
I added a test which uses
set_lento observe that data has been zero'd.I feel that this is useful, as it tests my code change, but it in no way tests the actual (post-optimisation) functionality of the library. I'm happy for it to be dropped, if someone else hates it. It is probably not guaranteed to pass, or even be safe (i.e. if
clear()is changed to deallocate the storage).