From 85652359e89b4ead08fd8cb1a5e398cc2347e90d Mon Sep 17 00:00:00 2001
From: "Tobin C. Harding" <me@tobin.cc>
Date: Wed, 12 Feb 2025 03:30:31 +1100
Subject: [PATCH] hashes: Derive Copy and Clone for Hkdf

Currently the `Hkdf` type does not derive any traits.

We would like to derive the common set of traits but there are a bunch
reasons we can't;

- Don't want to leak secrets in `Debug`.
- Don't want to enable timing attacks with Eq/Ord and friends.

For now just derive `Copy` and `Clone`. We will then implement `Debug`
manually.
---
 hashes/src/hkdf/mod.rs | 1 +
 1 file changed, 1 insertion(+)

diff --git a/hashes/src/hkdf/mod.rs b/hashes/src/hkdf/mod.rs
index f9f027857..b2cba0838 100644
--- a/hashes/src/hkdf/mod.rs
+++ b/hashes/src/hkdf/mod.rs
@@ -32,6 +32,7 @@ impl fmt::Display for MaxLengthError {
 impl std::error::Error for MaxLengthError {}
 
 /// HMAC-based Extract-and-Expand Key Derivation Function (HKDF).
+#[derive(Copy, Clone)]
 pub struct Hkdf<T: GeneralHash> {
     /// Pseudorandom key based on the extract step.
     prk: Hmac<T>,