From 501a3dd4ad4a545a05663a78cec61575966045c7 Mon Sep 17 00:00:00 2001
From: Sebastian Falbesoner <sebastian.falbesoner@gmail.com>
Date: Fri, 6 Mar 2026 16:58:49 +0100
Subject: [PATCH] walletdb: hash pubkey/privkey in one shot to avoid leaking
 secret data

Avoid storing the privkey in a vector, which could linger in memory
and potentially leak sensitive data. An alternative approach is to
use `secure_allocator` for the `std::vector` instances, but this
commit has the advantage of also deduplicating code at the same shot.

Thanks to @theuni for suggesting this.
---
 src/wallet/walletdb.cpp | 28 ++++++++--------------------
 1 file changed, 8 insertions(+), 20 deletions(-)

diff --git a/src/wallet/walletdb.cpp b/src/wallet/walletdb.cpp
index 4cb8c11ee95..6e6aab14742 100644
--- a/src/wallet/walletdb.cpp
+++ b/src/wallet/walletdb.cpp
@@ -117,12 +117,9 @@ bool WalletBatch::WriteKey(const CPubKey& vchPubKey, const CPrivKey& vchPrivKey,
     }
 
     // hash pubkey/privkey to accelerate wallet load
-    std::vector<unsigned char> vchKey;
-    vchKey.reserve(vchPubKey.size() + vchPrivKey.size());
-    vchKey.insert(vchKey.end(), vchPubKey.begin(), vchPubKey.end());
-    vchKey.insert(vchKey.end(), vchPrivKey.begin(), vchPrivKey.end());
+    const auto keypair_hash = Hash(vchPubKey, vchPrivKey);
 
-    return WriteIC(std::make_pair(DBKeys::KEY, vchPubKey), std::make_pair(vchPrivKey, Hash(vchKey)), false);
+    return WriteIC(std::make_pair(DBKeys::KEY, vchPubKey), std::make_pair(vchPrivKey, keypair_hash), false);
 }
 
 bool WalletBatch::WriteCryptedKey(const CPubKey& vchPubKey,
@@ -220,12 +217,9 @@ bool WalletBatch::EraseActiveScriptPubKeyMan(uint8_t type, bool internal)
 bool WalletBatch::WriteDescriptorKey(const uint256& desc_id, const CPubKey& pubkey, const CPrivKey& privkey)
 {
     // hash pubkey/privkey to accelerate wallet load
-    std::vector<unsigned char> key;
-    key.reserve(pubkey.size() + privkey.size());
-    key.insert(key.end(), pubkey.begin(), pubkey.end());
-    key.insert(key.end(), privkey.begin(), privkey.end());
+    const auto keypair_hash = Hash(pubkey, privkey);
 
-    return WriteIC(std::make_pair(DBKeys::WALLETDESCRIPTORKEY, std::make_pair(desc_id, pubkey)), std::make_pair(privkey, Hash(key)), false);
+    return WriteIC(std::make_pair(DBKeys::WALLETDESCRIPTORKEY, std::make_pair(desc_id, pubkey)), std::make_pair(privkey, keypair_hash), false);
 }
 
 bool WalletBatch::WriteCryptedDescriptorKey(const uint256& desc_id, const CPubKey& pubkey, const std::vector<unsigned char>& secret)
@@ -328,12 +322,9 @@ bool LoadKey(CWallet* pwallet, DataStream& ssKey, DataStream& ssValue, std::stri
         if (!hash.IsNull())
         {
             // hash pubkey/privkey to accelerate wallet load
-            std::vector<unsigned char> vchKey;
-            vchKey.reserve(vchPubKey.size() + pkey.size());
-            vchKey.insert(vchKey.end(), vchPubKey.begin(), vchPubKey.end());
-            vchKey.insert(vchKey.end(), pkey.begin(), pkey.end());
+            const auto keypair_hash = Hash(vchPubKey, pkey);
 
-            if (Hash(vchKey) != hash)
+            if (keypair_hash != hash)
             {
                 strErr = "Error reading wallet database: CPubKey/CPrivKey corrupt";
                 return false;
@@ -875,12 +866,9 @@ static DBErrors LoadDescriptorWalletRecords(CWallet* pwallet, DatabaseBatch& bat
             value >> hash;
 
             // hash pubkey/privkey to accelerate wallet load
-            std::vector<unsigned char> to_hash;
-            to_hash.reserve(pubkey.size() + pkey.size());
-            to_hash.insert(to_hash.end(), pubkey.begin(), pubkey.end());
-            to_hash.insert(to_hash.end(), pkey.begin(), pkey.end());
+            const auto keypair_hash = Hash(pubkey, pkey);
 
-            if (Hash(to_hash) != hash)
+            if (keypair_hash != hash)
             {
                 strErr = "Error reading wallet database: descriptor unencrypted key CPubKey/CPrivKey corrupt";
                 return DBErrors::CORRUPT;