Upgrade or rewrite encrypted key checksums

If fDecryptionThoroughlyChecked is false, after a key has been checked,
write (or rewrite) its checksum. This serves to upgrade wallets
and correct those which have the checksum corrupted but not the key.

src/wallet/scriptpubkeyman.cpp

@@ -210,6 +210,7 @@ bool LegacyScriptPubKeyMan::CheckDecryptionKey(const CKeyingMaterial& master_key
         bool keyPass = mapCryptedKeys.empty(); // Always pass when there are no encrypted keys
         bool keyFail = false;
         CryptedKeyMap::const_iterator mi = mapCryptedKeys.begin();
+        WalletBatch batch(m_storage.GetDatabase());
         for (; mi != mapCryptedKeys.end(); ++mi)
         {
             const CPubKey &vchPubKey = (*mi).second.first;
@@ -223,6 +224,10 @@ bool LegacyScriptPubKeyMan::CheckDecryptionKey(const CKeyingMaterial& master_key
             keyPass = true;
             if (fDecryptionThoroughlyChecked)
                 break;
+            else {
+                // Rewrite these encrypted keys with checksums
+                batch.WriteCryptedKey(vchPubKey, vchCryptedSecret, mapKeyMetadata[vchPubKey.GetID()]);
+            }
         }
         if (keyPass && keyFail)
         {

src/wallet/walletdb.cpp

@@ -114,7 +114,14 @@ bool WalletBatch::WriteCryptedKey(const CPubKey& vchPubKey,
 
     const auto key = std::make_pair(DBKeys::CRYPTED_KEY, vchPubKey);
     if (!WriteIC(key, std::make_pair(vchCryptedSecret, checksum), false)) {
-        return false;
+        // It may already exist, so try writing just the checksum
+        std::vector<unsigned char> val;
+        if (!m_batch.Read(key, val)) {
+            return false;
+        }
+        if (!WriteIC(key, std::make_pair(val, checksum), true)) {
+            return false;
+        }
     }
     EraseIC(std::make_pair(DBKeys::KEY, vchPubKey));
     return true;