From 5bc414c45a5442fba82b150adaad96a1f44e05c5 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Pavel=20=C5=A0ev=C4=8D=C3=ADk?= <pajaseviwow@gmail.com>
Date: Sun, 5 Sep 2021 02:38:47 +0200
Subject: [PATCH] Derive postmix change decoy addresses more simply

---
 lib/bitcoin/hd-accounts-helper.js          | 46 ++++++----------------
 lib/bitcoin/parallel-address-derivation.js | 12 +++++-
 2 files changed, 21 insertions(+), 37 deletions(-)

diff --git a/lib/bitcoin/hd-accounts-helper.js b/lib/bitcoin/hd-accounts-helper.js
index c61b06a..dbfa6ce 100644
--- a/lib/bitcoin/hd-accounts-helper.js
+++ b/lib/bitcoin/hd-accounts-helper.js
@@ -299,7 +299,7 @@ class HDAccountsHelper {
    * @param {bitcoin.bip32.BIP32Interface} chainNode - Parent bip32 used for derivation
    * @param {number} index - index to be derived
    * @param {number} type - type of derivation
-   * @returns {Promise<object>} returns an object {address: '...', chain: <int>, index: <int>, publicKey: <Buffer>, address: string }
+   * @returns {Promise<object>} returns an object {address: '...', chain: <int>, index: <int>, address: string }
    */
   async deriveAddress(chain, chainNode, index, type) {
     // Derive M/chain/index
@@ -308,7 +308,6 @@ class HDAccountsHelper {
     const addr = {
       chain: chain,
       index: index,
-      publicKey: indexNode.publicKey
     }
 
     switch (type) {
@@ -363,17 +362,20 @@ class HDAccountsHelper {
       ) {
         // Few addresses to be derived or external derivation deactivated
         // Let's do it here
-        const addresses = await Promise.all(indices.map(index => {
+        const promises = indices.map(index => {
           return this.deriveAddress(chain, chainNode, index, info.type)
-        }))
+        })
 
         // Generate additional change address types for postmix account
         if (this.isPostmixAcct(node) && chain === 1) {
-          const additionalPostmixAddresses = this._generateAdditionalChangeAddresses(addresses)
-
-          addresses.push(...additionalPostmixAddresses)
+          indices.forEach((index) => {
+            promises.push(this.deriveAddress(chain, chainNode, index, this.BIP44))
+            promises.push(this.deriveAddress(chain, chainNode, index, this.BIP49))
+          })
         }
 
+        const addresses = await Promise.all(promises)
+
         return addresses;
 
       } else {
@@ -385,19 +387,13 @@ class HDAccountsHelper {
               xpub: this.xlatXPUB(xpub),
               chain: chain,
               indices: indices,
-              type: info.type
+              type: info.type,
+              isPostmixChange: this.isPostmixAcct(node) && chain === 1
             }
 
             const msg = await this.derivationPool.exec('deriveAddresses', [data])
 
             if (msg.status === 'ok') {
-              // Generate additional change address types for postmix account
-              if (this.isPostmixAcct(node) && chain === 1) {
-                const additionalPostmixAddresses = this._generateAdditionalChangeAddresses(msg.addresses)
-
-                msg.addresses.push(...additionalPostmixAddresses)
-              }
-
               resolve(msg.addresses)
             } else {
               Logger.error(null, 'HdAccountsHelper : A problem was met during parallel addresses derivation')
@@ -416,26 +412,6 @@ class HDAccountsHelper {
     }
   }
 
-  /**
-   * @description Derive additional change addresses (P2PKH & P2SH) for postmix account
-   * @param addresses {{ chain: number, index: number, publicKey: Buffer, address: string }[]} - list of derived addresses
-   * @returns {{ chain: number, index: number, publicKey: Buffer, address: string }[]} - array of additional address types
-   * @private
-   */
-  _generateAdditionalChangeAddresses(addresses) {
-    const additionalPostmixAddresses = addresses.map((address) => {
-      const newP2PKHAddress = {...address}
-      const newP2SHAddress = {...address}
-
-      newP2PKHAddress.address = addrHelper.p2pkhAddress(address.publicKey)
-      newP2SHAddress.address = addrHelper.p2wpkhP2shAddress(address.publicKey)
-
-      return [newP2PKHAddress, newP2SHAddress];
-    })
-
-    return additionalPostmixAddresses.flat()
-  }
-
   /**
    * @description Detect postmix account
    * @param {[bitcoin.bip32.BIP32Interface, bitcoin.bip32.BIP32Interface, bitcoin.bip32.BIP32Interface]} node - array of BIP32 node interfaces
diff --git a/lib/bitcoin/parallel-address-derivation.js b/lib/bitcoin/parallel-address-derivation.js
index 9c2bc08..4033406 100644
--- a/lib/bitcoin/parallel-address-derivation.js
+++ b/lib/bitcoin/parallel-address-derivation.js
@@ -25,7 +25,7 @@ const BIP84  = 2
  * @param {bip32} chainNode - Parent bip32 used for derivation
  * @param {number} index - index to be derived
  * @param {number} type - type of derivation
- * @returns {Promise<object>} returns an object {address: '...', chain: <int>, index: <int>, publicKey: <Buffer>}
+ * @returns {Promise<object>} returns an object {address: '...', chain: <int>, index: <int>}
  */
 async function deriveAddress(chain, chainNode, index, type) {
   // Derive M/chain/index
@@ -34,7 +34,6 @@ async function deriveAddress(chain, chainNode, index, type) {
   const addr = {
     chain: chain,
     index: index,
-    publicKey: indexNode.publicKey
   }
 
   switch (type) {
@@ -63,6 +62,7 @@ async function deriveAddresses(msg) {
     const chain = msg.chain
     const indices = msg.indices
     const type = msg.type
+    const isPostmixChange = msg.isPostmixChange
 
     // Parse input as an HD Node. Throws if invalid
     const node = bitcoin.bip32.fromBase58(xpub, activeNet)
@@ -77,6 +77,14 @@ async function deriveAddresses(msg) {
       return deriveAddress(chain, chainNode, index, type)
     })
 
+    // Generate additional change address types for postmix account
+    if (isPostmixChange) {
+      indices.forEach((index) => {
+        promises.push(deriveAddress(chain, chainNode, index, BIP44))
+        promises.push(deriveAddress(chain, chainNode, index, BIP49))
+      })
+    }
+
     const addresses = await Promise.all(promises)
 
     // Send response to parent process