[wallet] Support creating a blank wallet

A blank wallet is a wallet that has no keys, script or watch only things.
A new wallet flag indicating that it is blank will be set when the wallet
is blank. Once it is no longer blank (a seed has been generated, keys or
scripts imported, etc), the flag will be unset.

1 files changed, 58 insertions, 8 deletions

diff --git a/src/wallet/wallet.cpp b/src/wallet/wallet.cpp
index 3ce8371abb..8201b58e0e 100644
--- a/src/wallet/wallet.cpp
+++ b/src/wallet/wallet.cpp
@@ -168,6 +168,7 @@ const CWalletTx* CWallet::GetWalletTx(const uint256& hash) const
 CPubKey CWallet::GenerateNewKey(WalletBatch &batch, bool internal)
 {
     assert(!IsWalletFlagSet(WALLET_FLAG_DISABLE_PRIVATE_KEYS));
+    assert(!IsWalletFlagSet(WALLET_FLAG_BLANK_WALLET));
     AssertLockHeld(cs_wallet); // mapKeyMetadata
     bool fCompressed = CanSupportFeature(FEATURE_COMPRPUBKEY); // default to compressed public keys if we want 0.6.0 wallets
 
@@ -177,7 +178,7 @@ CPubKey CWallet::GenerateNewKey(WalletBatch &batch, bool internal)
     int64_t nCreationTime = GetTime();
     CKeyMetadata metadata(nCreationTime);
 
-    // use HD key derivation if HD was enabled during wallet creation
+    // use HD key derivation if HD was enabled during wallet creation and a seed is present
     if (IsHDEnabled()) {
         DeriveNewChildKey(batch, metadata, secret, (CanSupportFeature(FEATURE_HD_SPLIT) ? internal : false));
     } else {
@@ -283,6 +284,7 @@ bool CWallet::AddKeyPubKeyWithDB(WalletBatch &batch, const CKey& secret, const C
                                                  secret.GetPrivKey(),
                                                  mapKeyMetadata[pubkey.GetID()]);
     }
+    UnsetWalletFlag(WALLET_FLAG_BLANK_WALLET);
     return true;
 }
 
@@ -349,7 +351,11 @@ bool CWallet::AddCScript(const CScript& redeemScript)
 {
     if (!CCryptoKeyStore::AddCScript(redeemScript))
         return false;
-    return WalletBatch(*database).WriteCScript(Hash160(redeemScript), redeemScript);
+    if (WalletBatch(*database).WriteCScript(Hash160(redeemScript), redeemScript)) {
+        UnsetWalletFlag(WALLET_FLAG_BLANK_WALLET);
+        return true;
+    }
+    return false;
 }
 
 bool CWallet::LoadCScript(const CScript& redeemScript)
@@ -374,7 +380,11 @@ bool CWallet::AddWatchOnly(const CScript& dest)
     const CKeyMetadata& meta = m_script_metadata[CScriptID(dest)];
     UpdateTimeFirstKey(meta.nCreateTime);
     NotifyWatchonlyChanged(true);
-    return WalletBatch(*database).WriteWatchOnly(dest, meta);
+    if (WalletBatch(*database).WriteWatchOnly(dest, meta)) {
+        UnsetWalletFlag(WALLET_FLAG_BLANK_WALLET);
+        return true;
+    }
+    return false;
 }
 
 bool CWallet::AddWatchOnly(const CScript& dest, int64_t nCreateTime)
@@ -1402,6 +1412,7 @@ void CWallet::SetHDSeed(const CPubKey& seed)
     newHdChain.seed_id = seed.GetID();
     SetHDChain(newHdChain, false);
     NotifyCanGetAddressesChanged();
+    UnsetWalletFlag(WALLET_FLAG_BLANK_WALLET);
 }
 
 void CWallet::SetHDChain(const CHDChain& chain, bool memonly)
@@ -1418,6 +1429,30 @@ bool CWallet::IsHDEnabled() const
     return !hdChain.seed_id.IsNull();
 }
 
+bool CWallet::CanGenerateKeys()
+{
+    // A wallet can generate keys if it has an HD seed (IsHDEnabled) or it is a non-HD wallet (pre FEATURE_HD)
+    LOCK(cs_wallet);
+    return IsHDEnabled() || !CanSupportFeature(FEATURE_HD);
+}
+
+bool CWallet::CanGetAddresses(bool internal)
+{
+    LOCK(cs_wallet);
+    // Check if the keypool has keys
+    bool keypool_has_keys;
+    if (internal && CanSupportFeature(FEATURE_HD_SPLIT)) {
+        keypool_has_keys = setInternalKeyPool.size() > 0;
+    } else {
+        keypool_has_keys = KeypoolCountExternalKeys() > 0;
+    }
+    // If the keypool doesn't have keys, check if we can generate them
+    if (!keypool_has_keys) {
+        return CanGenerateKeys();
+    }
+    return keypool_has_keys;
+}
+
 void CWallet::SetWalletFlag(uint64_t flags)
 {
     LOCK(cs_wallet);
@@ -1426,6 +1461,14 @@ void CWallet::SetWalletFlag(uint64_t flags)
         throw std::runtime_error(std::string(__func__) + ": writing wallet flags failed");
 }
 
+void CWallet::UnsetWalletFlag(uint64_t flag)
+{
+    LOCK(cs_wallet);
+    m_wallet_flags &= ~flag;
+    if (!WalletBatch(*database).WriteWalletFlags(m_wallet_flags))
+        throw std::runtime_error(std::string(__func__) + ": writing wallet flags failed");
+}
+
 bool CWallet::IsWalletFlagSet(uint64_t flag)
 {
     return (m_wallet_flags & flag);
@@ -3101,7 +3144,8 @@ DBErrors CWallet::LoadWallet(bool& fFirstRunRet)
     {
         LOCK(cs_KeyStore);
         // This wallet is in its first run if all of these are empty
-        fFirstRunRet = mapKeys.empty() && mapCryptedKeys.empty() && mapWatchKeys.empty() && setWatchOnly.empty() && mapScripts.empty() && !IsWalletFlagSet(WALLET_FLAG_DISABLE_PRIVATE_KEYS);
+        fFirstRunRet = mapKeys.empty() && mapCryptedKeys.empty() && mapWatchKeys.empty() && setWatchOnly.empty() && mapScripts.empty()
+            && !IsWalletFlagSet(WALLET_FLAG_DISABLE_PRIVATE_KEYS) && !IsWalletFlagSet(WALLET_FLAG_BLANK_WALLET);
     }
 
     if (nLoadWalletRet != DBErrors::LOAD_OK)
@@ -3286,7 +3330,7 @@ void CWallet::LoadKeyPool(int64_t nIndex, const CKeyPool &keypool)
 
 bool CWallet::TopUpKeyPool(unsigned int kpSize)
 {
-    if (IsWalletFlagSet(WALLET_FLAG_DISABLE_PRIVATE_KEYS)) {
+    if (!CanGenerateKeys()) {
         return false;
     }
     {
@@ -3416,7 +3460,7 @@ void CWallet::ReturnKey(int64_t nIndex, bool fInternal, const CPubKey& pubkey)
 
 bool CWallet::GetKeyFromPool(CPubKey& result, bool internal)
 {
-    if (IsWalletFlagSet(WALLET_FLAG_DISABLE_PRIVATE_KEYS)) {
+    if (!CanGetAddresses(internal)) {
         return false;
     }
 
@@ -3617,6 +3661,10 @@ std::set<CTxDestination> CWallet::GetLabelAddresses(const std::string& label) co
 
 bool CReserveKey::GetReservedKey(CPubKey& pubkey, bool internal)
 {
+    if (!pwallet->CanGetAddresses(internal)) {
+        return false;
+    }
+
     if (nIndex == -1)
     {
         CKeyPool keypool;
@@ -4071,14 +4119,16 @@ std::shared_ptr<CWallet> CWallet::CreateWalletFromFile(interfaces::Chain& chain,
         if ((wallet_creation_flags & WALLET_FLAG_DISABLE_PRIVATE_KEYS)) {
             //selective allow to set flags
             walletInstance->SetWalletFlag(WALLET_FLAG_DISABLE_PRIVATE_KEYS);
+        } else if (wallet_creation_flags & WALLET_FLAG_BLANK_WALLET) {
+            walletInstance->SetWalletFlag(WALLET_FLAG_BLANK_WALLET);
         } else {
             // generate a new seed
             CPubKey seed = walletInstance->GenerateNewSeed();
             walletInstance->SetHDSeed(seed);
-        }
+        } // Otherwise, do not generate a new seed
 
         // Top up the keypool
-        if (!walletInstance->IsWalletFlagSet(WALLET_FLAG_DISABLE_PRIVATE_KEYS) && !walletInstance->TopUpKeyPool()) {
+        if (walletInstance->CanGenerateKeys() && !walletInstance->TopUpKeyPool()) {
             InitError(_("Unable to generate initial keys"));
             return nullptr;
         }