wallet: Upgrade existing descriptor caches

Add functions to upgrade existing descriptor caches to support the use
of last hardened xpub caching.

src/wallet/scriptpubkeyman.cpp

@@ -2278,3 +2278,32 @@ bool DescriptorScriptPubKeyMan::GetDescriptorString(std::string& out, bool priv)
 
     return m_wallet_descriptor.descriptor->ToNormalizedString(provider, out, priv);
 }
+
+void DescriptorScriptPubKeyMan::UpgradeDescriptorCache()
+{
+    LOCK(cs_desc_man);
+    if (m_storage.IsLocked() || m_storage.IsWalletFlagSet(WALLET_FLAG_LAST_HARDENED_XPUB_CACHED)) {
+        return;
+    }
+
+    // Skip if we have the last hardened xpub cache
+    if (m_wallet_descriptor.cache.GetCachedLastHardenedExtPubKeys().size() > 0) {
+        return;
+    }
+
+    // Expand the descriptor
+    FlatSigningProvider provider;
+    provider.keys = GetKeys();
+    FlatSigningProvider out_keys;
+    std::vector<CScript> scripts_temp;
+    DescriptorCache temp_cache;
+    if (!m_wallet_descriptor.descriptor->Expand(0, provider, scripts_temp, out_keys, &temp_cache)){
+        throw std::runtime_error("Unable to expand descriptor");
+    }
+
+    // Cache the last hardened xpubs
+    DescriptorCache diff = m_wallet_descriptor.cache.MergeAndDiff(temp_cache);
+    if (!WalletBatch(m_storage.GetDatabase()).WriteDescriptorCacheItems(GetID(), diff)) {
+        throw std::runtime_error(std::string(__func__) + ": writing cache items failed");
+    }
+}

src/wallet/scriptpubkeyman.h

@@ -631,6 +631,8 @@ public:
     const std::vector<CScript> GetScriptPubKeys() const;
 
     bool GetDescriptorString(std::string& out, bool priv) const;
+
+    void UpgradeDescriptorCache();
 };
 
 #endif // BITCOIN_WALLET_SCRIPTPUBKEYMAN_H

src/wallet/wallet.cpp

@@ -374,6 +374,19 @@ void CWallet::UpgradeKeyMetadata()
     SetWalletFlag(WALLET_FLAG_KEY_ORIGIN_METADATA);
 }
 
+void CWallet::UpgradeDescriptorCache()
+{
+    if (!IsWalletFlagSet(WALLET_FLAG_DESCRIPTORS) || IsLocked() || IsWalletFlagSet(WALLET_FLAG_LAST_HARDENED_XPUB_CACHED)) {
+        return;
+    }
+
+    for (ScriptPubKeyMan* spkm : GetAllScriptPubKeyMans()) {
+        DescriptorScriptPubKeyMan* desc_spkm = dynamic_cast<DescriptorScriptPubKeyMan*>(spkm);
+        desc_spkm->UpgradeDescriptorCache();
+    }
+    SetWalletFlag(WALLET_FLAG_LAST_HARDENED_XPUB_CACHED);
+}
+
 bool CWallet::Unlock(const SecureString& strWalletPassphrase, bool accept_no_keys)
 {
     CCrypter crypter;
@@ -390,6 +403,8 @@ bool CWallet::Unlock(const SecureString& strWalletPassphrase, bool accept_no_key
             if (Unlock(_vMasterKey, accept_no_keys)) {
                 // Now that we've unlocked, upgrade the key metadata
                 UpgradeKeyMetadata();
+                // Now that we've unlocked, upgrade the descriptor cache
+                UpgradeDescriptorCache();
                 return true;
             }
         }

src/wallet/wallet.h

@@ -117,6 +117,7 @@ static constexpr uint64_t KNOWN_WALLET_FLAGS =
         WALLET_FLAG_AVOID_REUSE
     |   WALLET_FLAG_BLANK_WALLET
     |   WALLET_FLAG_KEY_ORIGIN_METADATA
+    |   WALLET_FLAG_LAST_HARDENED_XPUB_CACHED
     |   WALLET_FLAG_DISABLE_PRIVATE_KEYS
     |   WALLET_FLAG_DESCRIPTORS
     |   WALLET_FLAG_EXTERNAL_SIGNER;
@@ -128,6 +129,7 @@ static const std::map<std::string,WalletFlags> WALLET_FLAG_MAP{
     {"avoid_reuse", WALLET_FLAG_AVOID_REUSE},
     {"blank", WALLET_FLAG_BLANK_WALLET},
     {"key_origin_metadata", WALLET_FLAG_KEY_ORIGIN_METADATA},
+    {"last_hardened_xpub_cached", WALLET_FLAG_LAST_HARDENED_XPUB_CACHED},
     {"disable_private_keys", WALLET_FLAG_DISABLE_PRIVATE_KEYS},
     {"descriptor_wallet", WALLET_FLAG_DESCRIPTORS},
     {"external_signer", WALLET_FLAG_EXTERNAL_SIGNER}
@@ -476,6 +478,9 @@ public:
     //! Upgrade stored CKeyMetadata objects to store key origin info as KeyOriginInfo
     void UpgradeKeyMetadata() EXCLUSIVE_LOCKS_REQUIRED(cs_wallet);
 
+    //! Upgrade DescriptorCaches
+    void UpgradeDescriptorCache() EXCLUSIVE_LOCKS_REQUIRED(cs_wallet);
+
     bool LoadMinVersion(int nVersion) EXCLUSIVE_LOCKS_REQUIRED(cs_wallet) { AssertLockHeld(cs_wallet); nWalletVersion = nVersion; return true; }
 
     //! Adds a destination data tuple to the store, without saving it to disk

src/wallet/walletdb.cpp

@@ -884,6 +884,14 @@ DBErrors WalletBatch::LoadWallet(CWallet* pwallet)
         result = DBErrors::CORRUPT;
     }
 
+    // Upgrade all of the descriptor caches to cache the last hardened xpub
+    // This operation is not atomic, but if it fails, only new entries are added so it is backwards compatible
+    try {
+        pwallet->UpgradeDescriptorCache();
+    } catch (...) {
+        result = DBErrors::CORRUPT;
+    }
+
     // Set the inactive chain
     if (wss.m_hd_chains.size() > 0) {
         LegacyScriptPubKeyMan* legacy_spkm = pwallet->GetLegacyScriptPubKeyMan();

src/wallet/walletutil.h

@@ -43,6 +43,9 @@ enum WalletFlags : uint64_t {
     // Indicates that the metadata has already been upgraded to contain key origins
     WALLET_FLAG_KEY_ORIGIN_METADATA = (1ULL << 1),
 
+    // Indicates that the descriptor cache has been upgraded to cache last hardened xpubs
+    WALLET_FLAG_LAST_HARDENED_XPUB_CACHED = (1ULL << 2),
+
     // will enforce the rule that the wallet can't contain any private keys (only watch-only/pubkeys)
     WALLET_FLAG_DISABLE_PRIVATE_KEYS = (1ULL << 32),