wallet: Pass FastRandomContext& to DiscourageFeeSniping

Author: MarcoFalke

src/wallet/spend.cpp

@@ -585,7 +585,8 @@ static bool IsCurrentForAntiFeeSniping(interfaces::Chain& chain, const uint256&
  * Set a height-based locktime for new transactions (uses the height of the
  * current chain tip unless we are not synced with the current chain
  */
-static void DiscourageFeeSniping(CMutableTransaction& tx, interfaces::Chain& chain, const uint256& block_hash, int block_height)
+static void DiscourageFeeSniping(CMutableTransaction& tx, FastRandomContext& rng_fast,
+                                 interfaces::Chain& chain, const uint256& block_hash, int block_height)
 {
     // All inputs must be added by now
     assert(!tx.vin.empty());
@@ -616,8 +617,8 @@ static void DiscourageFeeSniping(CMutableTransaction& tx, interfaces::Chain& cha
         // that transactions that are delayed after signing for whatever reason,
         // e.g. high-latency mix networks and some CoinJoin implementations, have
         // better privacy.
-        if (GetRandInt(10) == 0) {
-            tx.nLockTime = std::max(0, int(tx.nLockTime) - GetRandInt(100));
+        if (rng_fast.randrange(10) == 0) {
+            tx.nLockTime = std::max(0, int(tx.nLockTime) - int(rng_fast.randrange(100)));
         }
     } else {
         // If our chain is lagging behind, we can't discourage fee sniping nor help
@@ -653,6 +654,7 @@ static bool CreateTransactionInternal(
 {
     AssertLockHeld(wallet.cs_wallet);
 
+    FastRandomContext rng_fast;
     CMutableTransaction txNew; // The resulting transaction that we make
 
     CoinSelectionParams coin_selection_params; // Parameters for coin selection, init with dummy
@@ -782,10 +784,9 @@ static bool CreateTransactionInternal(
     assert(change_and_fee >= 0);
     CTxOut newTxOut(change_and_fee, scriptChange);
 
-    if (nChangePosInOut == -1)
-    {
+    if (nChangePosInOut == -1) {
         // Insert change txn at random position:
-        nChangePosInOut = GetRandInt(txNew.vout.size()+1);
+        nChangePosInOut = rng_fast.randrange(txNew.vout.size() + 1);
     }
     else if ((unsigned int)nChangePosInOut > txNew.vout.size())
     {
@@ -811,7 +812,7 @@ static bool CreateTransactionInternal(
     for (const auto& coin : selected_coins) {
         txNew.vin.push_back(CTxIn(coin.outpoint, CScript(), nSequence));
     }
-    DiscourageFeeSniping(txNew, wallet.chain(), wallet.GetLastBlockHash(), wallet.GetLastBlockHeight());
+    DiscourageFeeSniping(txNew, rng_fast, wallet.chain(), wallet.GetLastBlockHash(), wallet.GetLastBlockHeight());
 
     // Calculate the transaction fee
     TxSize tx_sizes = CalculateMaximumSignedTxSize(CTransaction(txNew), &wallet, &coin_control);