Make Ed25519 public key validation native return `false` if key has the wrong length

AIP-23 - Make Ed25519 public key validation native return false if key has the wrong length

Summary

Changes the function native_public_key_validate used by the native Move function native fun pubkey_validate_internal to return false if the public key provided is the wrong length. Previously, this function would abort if the key length provided was incorrect. This change is gated by a feature flag.

Motivation

This feature allows for more flexible error handling by users of the native_public_key_validate function.

Rationale

Gating behind a feature flag ensures backwards compatibility with previous calls of native_public_key_validate, by not changing the behavior of previous transactions before the flag is enabled.

Specification

The relevant code in the reference implementation below is as follows:

let key_bytes_slice = match <[u8; ED25519_PUBLIC_KEY_LENGTH]>::try_from(key_bytes) {
    Ok(slice) => slice,
    Err(_) => {
        return Err(SafeNativeError::Abort {
            abort_code: abort_codes::E_WRONG_PUBKEY_SIZE,
        });
        if context
            .get_feature_flags()
            .is_enabled(FeatureFlag::ED25519_PUBKEY_VALIDATE_RETURN_FALSE_WRONG_LENGTH)
        {
            return Ok(smallvec![Value::bool(false)]);
        } else {
            return Err(SafeNativeError::Abort {
                abort_code: abort_codes::E_WRONG_PUBKEY_SIZE,
            });
        }
    },
};

Reference Implementation

https://github.com/aptos-labs/aptos-core/pull/7043

Risks and Drawbacks

Callers relying on the previous behavior of native_public_key_validate may be affected by this change. Currently, end-to-end tests show there are no such callers. Furthermore, it is unlikely that past callers of this function, if any, would be affected if the function returns false instead of aborting. This is because such callers would typically need to check the return value of the function anyway & would most likely abort anyway if the return value is false.

Future Potential

Future callers of native_public_key_validate will benefit from more flexible error handling, as mentioned above.

Suggested implementation timeline

It has already been implemented: see above reference implementation.

Suggested deployment timeline

This AIP is planned to be deployed on devnet and then testnet in April, with deployment on mainnet in early May.