Use 72 byte dummy signatures when watching only inputs may be used

With watching only inputs, we do not know how large the signatures
for those inputs will be as their signers may not have implemented
71 byte signatures. Thus we estimate their fees using the 72 byte
dummy signature to ensure that we pay enough fees.

This only effects fundrawtransaction when includeWatching is true.

1 files changed, 15 insertions, 12 deletions

diff --git a/src/wallet/wallet.h b/src/wallet/wallet.h
index 8054cfadf0..d1c0218d9e 100644
--- a/src/wallet/wallet.h
+++ b/src/wallet/wallet.h
@@ -276,7 +276,7 @@ public:
 };
 
 //Get the marginal bytes of spending the specified output
-int CalculateMaximumSignedInputSize(const CTxOut& txout, const CWallet* pwallet);
+int CalculateMaximumSignedInputSize(const CTxOut& txout, const CWallet* pwallet, bool use_max_sig = false);
 
 /**
  * A transaction with a bunch of additional info that only the owner cares about.
@@ -461,9 +461,9 @@ public:
     CAmount GetChange() const;
 
     // Get the marginal bytes if spending the specified output from this transaction
-    int GetSpendSize(unsigned int out) const
+    int GetSpendSize(unsigned int out, bool use_max_sig = false) const
     {
-        return CalculateMaximumSignedInputSize(tx->vout[out], pwallet);
+        return CalculateMaximumSignedInputSize(tx->vout[out], pwallet, use_max_sig);
     }
 
     void GetAmounts(std::list<COutputEntry>& listReceived,
@@ -507,6 +507,9 @@ public:
     /** Whether we know how to spend this output, ignoring the lack of keys */
     bool fSolvable;
 
+    /** Whether to use the maximum sized, 72 byte signature when calculating the size of the input spend. This should only be set when watch-only outputs are allowed */
+    bool use_max_sig;
+
     /**
      * Whether this output is considered safe to spend. Unconfirmed transactions
      * from outside keys and unconfirmed replacement transactions are considered
@@ -514,13 +517,13 @@ public:
      */
     bool fSafe;
 
-    COutput(const CWalletTx *txIn, int iIn, int nDepthIn, bool fSpendableIn, bool fSolvableIn, bool fSafeIn)
+    COutput(const CWalletTx *txIn, int iIn, int nDepthIn, bool fSpendableIn, bool fSolvableIn, bool fSafeIn, bool use_max_sig_in = false)
     {
-        tx = txIn; i = iIn; nDepth = nDepthIn; fSpendable = fSpendableIn; fSolvable = fSolvableIn; fSafe = fSafeIn; nInputBytes = -1;
+        tx = txIn; i = iIn; nDepth = nDepthIn; fSpendable = fSpendableIn; fSolvable = fSolvableIn; fSafe = fSafeIn; nInputBytes = -1; use_max_sig = use_max_sig_in;
         // If known and signable by the given wallet, compute nInputBytes
         // Failure will keep this value -1
         if (fSpendable && tx) {
-            nInputBytes = tx->GetSpendSize(i);
+            nInputBytes = tx->GetSpendSize(i, use_max_sig);
         }
     }
 
@@ -976,14 +979,14 @@ public:
     void ListAccountCreditDebit(const std::string& strAccount, std::list<CAccountingEntry>& entries);
     bool AddAccountingEntry(const CAccountingEntry&);
     bool AddAccountingEntry(const CAccountingEntry&, WalletBatch *batch);
-    bool DummySignTx(CMutableTransaction &txNew, const std::set<CTxOut> &txouts) const
+    bool DummySignTx(CMutableTransaction &txNew, const std::set<CTxOut> &txouts, bool use_max_sig = false) const
     {
         std::vector<CTxOut> v_txouts(txouts.size());
         std::copy(txouts.begin(), txouts.end(), v_txouts.begin());
-        return DummySignTx(txNew, v_txouts);
+        return DummySignTx(txNew, v_txouts, use_max_sig);
     }
-    bool DummySignTx(CMutableTransaction &txNew, const std::vector<CTxOut> &txouts) const;
-    bool DummySignInput(CTxIn &tx_in, const CTxOut &txout) const;
+    bool DummySignTx(CMutableTransaction &txNew, const std::vector<CTxOut> &txouts, bool use_max_sig = false) const;
+    bool DummySignInput(CTxIn &tx_in, const CTxOut &txout, bool use_max_sig = false) const;
 
     CFeeRate m_pay_tx_fee{DEFAULT_PAY_TX_FEE};
     unsigned int m_confirm_target{DEFAULT_TX_CONFIRM_TARGET};
@@ -1311,6 +1314,6 @@ public:
 // Use DummySignatureCreator, which inserts 71 byte signatures everywhere.
 // NOTE: this requires that all inputs must be in mapWallet (eg the tx should
 // be IsAllFromMe).
-int64_t CalculateMaximumSignedTxSize(const CTransaction &tx, const CWallet *wallet);
-int64_t CalculateMaximumSignedTxSize(const CTransaction &tx, const CWallet *wallet, const std::vector<CTxOut>& txouts);
+int64_t CalculateMaximumSignedTxSize(const CTransaction &tx, const CWallet *wallet, bool use_max_sig = false);
+int64_t CalculateMaximumSignedTxSize(const CTransaction &tx, const CWallet *wallet, const std::vector<CTxOut>& txouts, bool use_max_sig = false);
 #endif // BITCOIN_WALLET_WALLET_H