From 5256108a2fd708c2180f82cc8a52a4c0d173ca2d Mon Sep 17 00:00:00 2001
From: Matt Johnston <matt@ucc.asn.au>
Date: Sun, 18 Jun 2023 10:49:36 +0800
Subject: [PATCH] ConstantTimeEq and PartialEq for SigningKey

---
 Cargo.lock     |  1 +
 Cargo.toml     |  1 +
 src/signing.rs | 15 +++++++++++++++
 3 files changed, 17 insertions(+)

diff --git a/Cargo.lock b/Cargo.lock
index fe13ccc..c025969 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -313,6 +313,7 @@ dependencies = [
  "sha2",
  "sha3",
  "signature",
+ "subtle",
  "toml",
  "zeroize",
 ]
diff --git a/Cargo.toml b/Cargo.toml
index ec28d59..71739e4 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -29,6 +29,7 @@ curve25519-dalek = { version = "=4.0.0-rc.2", default-features = false, features
 ed25519 = { version = ">=2.2, <2.3", default-features = false }
 signature = { version = ">=2.0, <2.1", optional = true, default-features = false }
 sha2 = { version = "0.10", default-features = false }
+subtle = { version = "2.3.0", default-features = false }
 
 # optional features
 merlin = { version = "3", default-features = false, optional = true }
diff --git a/src/signing.rs b/src/signing.rs
index b0f0b49..5af8675 100644
--- a/src/signing.rs
+++ b/src/signing.rs
@@ -19,6 +19,7 @@ use rand_core::CryptoRngCore;
 use serde::{Deserialize, Deserializer, Serialize, Serializer};
 
 use sha2::Sha512;
+use subtle::{ConstantTimeEq, Choice};
 
 use curve25519_dalek::{
     digest::{generic_array::typenum::U64, Digest},
@@ -583,6 +584,20 @@ impl TryFrom<&[u8]> for SigningKey {
     }
 }
 
+impl ConstantTimeEq for SigningKey {
+    fn ct_eq(&self, other: &Self) -> Choice {
+        self.secret_key.ct_eq(&other.secret_key)
+    }
+}
+
+impl PartialEq for SigningKey {
+    fn eq(&self, other: &Self) -> bool {
+        self.ct_eq(other).into()
+    }
+}
+
+impl Eq for SigningKey {}
+
 #[cfg(feature = "zeroize")]
 impl Drop for SigningKey {
     fn drop(&mut self) {