From 36034c2f72e595c14a6103dfcdb9d80c34451a9a Mon Sep 17 00:00:00 2001
From: Luke Parker <lukeparker5132@gmail.com>
Date: Sat, 11 Mar 2023 10:51:40 -0500
Subject: [PATCH] Move ecdh derivation up to prevent Scalar::one() * ecdh

---
 coins/monero/src/wallet/mod.rs      |  5 ++---
 coins/monero/src/wallet/scan.rs     |  4 ++--
 coins/monero/src/wallet/send/mod.rs | 20 ++++++--------------
 3 files changed, 10 insertions(+), 19 deletions(-)

diff --git a/coins/monero/src/wallet/mod.rs b/coins/monero/src/wallet/mod.rs
index 1f23406b..72f098ba 100644
--- a/coins/monero/src/wallet/mod.rs
+++ b/coins/monero/src/wallet/mod.rs
@@ -59,12 +59,11 @@ pub(crate) fn uniqueness(inputs: &[Input]) -> [u8; 32] {
 #[allow(non_snake_case)]
 pub(crate) fn shared_key(
   uniqueness: Option<[u8; 32]>,
-  s: &Zeroizing<Scalar>,
-  P: &EdwardsPoint,
+  ecdh: EdwardsPoint,
   o: usize,
 ) -> (u8, Scalar, [u8; 8]) {
   // 8Ra
-  let mut output_derivation = (s.deref() * P).mul_by_cofactor().compress().to_bytes().to_vec();
+  let mut output_derivation = ecdh.mul_by_cofactor().compress().to_bytes().to_vec();
 
   let mut payment_id_xor = [0; 8];
   payment_id_xor
diff --git a/coins/monero/src/wallet/scan.rs b/coins/monero/src/wallet/scan.rs
index f4a1f580..3deb080f 100644
--- a/coins/monero/src/wallet/scan.rs
+++ b/coins/monero/src/wallet/scan.rs
@@ -1,3 +1,4 @@
+use core::ops::Deref;
 use std::io::{self, Read, Write};
 
 use zeroize::{Zeroize, ZeroizeOnDrop};
@@ -316,8 +317,7 @@ impl Scanner {
         };
         let (view_tag, shared_key, payment_id_xor) = shared_key(
           if self.burning_bug.is_none() { Some(uniqueness(&tx.prefix.inputs)) } else { None },
-          &self.pair.view,
-          key,
+          self.pair.view.deref() * key,
           o,
         );
 
diff --git a/coins/monero/src/wallet/send/mod.rs b/coins/monero/src/wallet/send/mod.rs
index f8eec1e6..10704ec6 100644
--- a/coins/monero/src/wallet/send/mod.rs
+++ b/coins/monero/src/wallet/send/mod.rs
@@ -59,15 +59,14 @@ impl SendOutput {
   fn internal(
     unique: [u8; 32],
     output: (usize, (MoneroAddress, u64)),
-    ecdh_left: &Zeroizing<Scalar>,
-    ecdh_right: &EdwardsPoint,
+    ecdh: EdwardsPoint,
     R: EdwardsPoint,
   ) -> (SendOutput, Option<[u8; 8]>) {
     let o = output.0;
     let output = output.1;
 
     let (view_tag, shared_key, payment_id_xor) =
-      shared_key(Some(unique).filter(|_| output.0.is_guaranteed()), ecdh_left, ecdh_right, o);
+      shared_key(Some(unique).filter(|_| output.0.is_guaranteed()), ecdh, o);
 
     (
       SendOutput {
@@ -93,8 +92,7 @@ impl SendOutput {
     SendOutput::internal(
       unique,
       output,
-      r,
-      &address.view,
+      r.deref() * address.view,
       if !address.is_subaddress() {
         r.deref() * &ED25519_BASEPOINT_TABLE
       } else {
@@ -104,17 +102,11 @@ impl SendOutput {
   }
 
   fn change(
-    ecdh: &EdwardsPoint,
+    ecdh: EdwardsPoint,
     unique: [u8; 32],
     output: (usize, (MoneroAddress, u64)),
   ) -> (SendOutput, Option<[u8; 8]>) {
-    SendOutput::internal(
-      unique,
-      output,
-      &Zeroizing::new(Scalar::one()),
-      ecdh,
-      ED25519_BASEPOINT_POINT,
-    )
+    SendOutput::internal(unique, output, ecdh, ED25519_BASEPOINT_POINT)
   }
 }
 
@@ -440,7 +432,7 @@ impl SignableTransaction {
           // Instead of rA, use Ra, where R is r * subaddress_spend_key
           // change.view must be Some as if it's None, this payment would've been downcast
           let ecdh = tx_public_key * change.view.unwrap().deref();
-          SendOutput::change(&ecdh, uniqueness, (o, (change.address, amount)))
+          SendOutput::change(ecdh, uniqueness, (o, (change.address, amount)))
         }
       };