[Mining] Use -miningaddress for in-wallet mining.

Replaces the hook to get a mining address from the wallet
with a retrieval of the address set as `-miningaddress`.

Disallows stealth addresses as per current behavior validating
`-miningaddress` at startup and in rpc mining.

Performs an additional safety check that the wallet actually owns the
given address, falling back to a random wallet address otherwise
(preserving current behavior).

Author: Zannick

src/wallet/wallet.cpp

@@ -4702,7 +4702,7 @@ void CWallet::MarkReserveKeysAsUsed(int64_t keypool_id)
     }
 }
 
-void CWallet::GetScriptForMining(std::shared_ptr<CReserveScript> &script)
+void CWallet::GetScriptForMiningReserveKey(std::shared_ptr<CReserveScript> &script)
 {
     std::shared_ptr<CReserveKey> rKey = std::make_shared<CReserveKey>(this);
     CPubKey pubkey;
@@ -4713,6 +4713,31 @@ void CWallet::GetScriptForMining(std::shared_ptr<CReserveScript> &script)
     script->reserveScript = CScript() << ToByteVector(pubkey) << OP_CHECKSIG;
 }
 
+void CWallet::GetScriptForMining(std::shared_ptr<CReserveScript> &script)
+{
+    std::string sAddress = gArgs.GetArg("-miningaddress", "");
+    if (!sAddress.empty()) {
+        CTxDestination dest = DecodeDestination(sAddress);
+
+        if (IsValidDestination(dest)) {
+            if (IsMine(dest) != ISMINE_SPENDABLE) {
+                WalletLogPrintf("-miningaddress %s not under my control, falling back to random address", sAddress);
+                return GetScriptForMiningReserveKey(script);
+            }
+            // Disallow Stealth Addresses for now
+            CBitcoinAddress address(sAddress);
+            if (address.IsValidStealthAddress()) {
+                WalletLogPrintf("-miningaddress must be a basecoin address");
+                return GetScriptForMiningReserveKey(script);
+            }
+            script = std::make_shared<CReserveScript>();
+            script->reserveScript = GetScriptForDestination(dest);
+            return;
+        }
+    }
+    return GetScriptForMiningReserveKey(script);
+}
+
 void CWallet::LockCoin(const COutPoint& output)
 {
     AssertLockHeld(cs_wallet); // setLockedCoins

src/wallet/wallet.h

@@ -1221,6 +1221,7 @@ class CWallet final : public CCryptoKeyStore, public CValidationInterface
 
     const std::string& GetLabelName(const CScript& scriptPubKey) const;
 
+    void GetScriptForMiningReserveKey(std::shared_ptr<CReserveScript> &script);
     void GetScriptForMining(std::shared_ptr<CReserveScript> &script);
 
     unsigned int GetKeyPoolSize() EXCLUSIVE_LOCKS_REQUIRED(cs_wallet)