Ignore too-long redeemScripts while loading wallet

This avoids that long redeemScripts that were grandfathered in
prevent the wallet from loading.

Fixes #4313.

Rebased-From: 18116b0

src/wallet.cpp

@@ -130,6 +130,22 @@ bool CWallet::AddCScript(const CScript& redeemScript)
     return CWalletDB(strWalletFile).WriteCScript(Hash160(redeemScript), redeemScript);
 }
 
+bool CWallet::LoadCScript(const CScript& redeemScript)
+{
+    /* A sanity check was added in pull #3843 to avoid adding redeemScripts
+     * that never can be redeemed. However, old wallets may still contain
+     * these. Do not add them to the wallet and warn. */
+    if (redeemScript.size() > MAX_SCRIPT_ELEMENT_SIZE)
+    {
+        std::string strAddr = CBitcoinAddress(redeemScript.GetID()).ToString();
+        LogPrintf("%s: Warning: This wallet contains a redeemScript of size %i which exceeds maximum size %i thus can never be redeemed. Do not use address %s.\n",
+            __func__, redeemScript.size(), MAX_SCRIPT_ELEMENT_SIZE, strAddr);
+        return true;
+    }
+
+    return CCryptoKeyStore::AddCScript(redeemScript);
+}
+
 bool CWallet::Unlock(const SecureString& strWalletPassphrase)
 {
     CCrypter crypter;

src/wallet.h

@@ -398,7 +398,7 @@ class CWallet : public CCryptoKeyStore, public CWalletInterface
     // Adds an encrypted key to the store, without saving it to disk (used by LoadWallet)
     bool LoadCryptedKey(const CPubKey &vchPubKey, const std::vector<unsigned char> &vchCryptedSecret);
     bool AddCScript(const CScript& redeemScript);
-    bool LoadCScript(const CScript& redeemScript) { return CCryptoKeyStore::AddCScript(redeemScript); }
+    bool LoadCScript(const CScript& redeemScript);
 
     /// Adds a destination data tuple to the store, and saves it to disk
     bool AddDestData(const CTxDestination &dest, const std::string &key, const std::string &value);