Merge #16798: Refactor rawtransaction_util's SignTransaction to separate prevtx parsing

39034f1ee628dae0bc9da5b1b30b8a424e66d968 Refactor rawtransaction_util's SignTransaction to have previous tx parsing be separate (Andrew Chow)

Pull request description:

  Currently the `SignTransaction` function has to handle both the actual signing and parsing of previous transaction data. This PR splits it so that `SignTransaction` only handles the signing itself and adds a `ParsePrevouts` function which handles parsing the prevtx information.

  This allows for `SignTransaction` to just take any `SigningProvider`.

  Split from #16341

ACKs for top commit:
  MarcoFalke:
    ACK 39034f1ee628dae0bc9da5b1b30b8a424e66d968
  instagibbs:
    utACK 39034f1ee6
  ryanofsky:
    utACK 39034f1ee628dae0bc9da5b1b30b8a424e66d968. No change since previously reviewed b49bbb939be92a67ff77c3f7bca5bb94dd141906, https://github.com/bitcoin/bitcoin/pull/16341#pullrequestreview-278610269 other than rebase with no conflicts.

Tree-SHA512: 09f7733e90691766bfb5cf0f20e913dbf270bd3b51abdcad966b24d110e562ed85fd3d0d1d7bbea61f903340060052ec73c4817b09aee0dc1f3916d781a9e40c

src/rpc/rawtransaction.cpp

@@ -779,7 +779,10 @@ static UniValue signrawtransactionwithkey(const JSONRPCRequest& request)
     NodeContext& node = EnsureNodeContext(request.context);
     FindCoins(node, coins);
 
-    return SignTransaction(mtx, request.params[2], &keystore, coins, true, request.params[3]);
+    // Parse the prevtxs array
+    ParsePrevouts(request.params[2], &keystore, coins);
+
+    return SignTransaction(mtx, &keystore, coins, request.params[3]);
 }
 
 UniValue sendrawtransaction(const JSONRPCRequest& request)

src/rpc/rawtransaction_util.cpp

@@ -129,9 +129,8 @@ static void TxInErrorToJSON(const CTxIn& txin, UniValue& vErrorsRet, const std::
     vErrorsRet.push_back(entry);
 }
 
-UniValue SignTransaction(CMutableTransaction& mtx, const UniValue& prevTxsUnival, FillableSigningProvider* keystore, std::map<COutPoint, Coin>& coins, bool is_temp_keystore, const UniValue& hashType)
+void ParsePrevouts(const UniValue& prevTxsUnival, FillableSigningProvider* keystore, std::map<COutPoint, Coin>& coins)
 {
-    // Add previous txouts given in the RPC call:
     if (!prevTxsUnival.isNull()) {
         UniValue prevTxs = prevTxsUnival.get_array();
         for (unsigned int idx = 0; idx < prevTxs.size(); ++idx) {
@@ -179,7 +178,7 @@ UniValue SignTransaction(CMutableTransaction& mtx, const UniValue& prevTxsUnival
             }
 
             // if redeemScript and private keys were given, add redeemScript to the keystore so it can be signed
-            if (is_temp_keystore && scriptPubKey.IsPayToScriptHash()) {
+            if (keystore && scriptPubKey.IsPayToScriptHash()) {
                 RPCTypeCheckObj(prevOut,
                 {
                     {"redeemScript", UniValueType(UniValue::VSTR)},
@@ -193,7 +192,10 @@ UniValue SignTransaction(CMutableTransaction& mtx, const UniValue& prevTxsUnival
             }
         }
     }
+}
 
+UniValue SignTransaction(CMutableTransaction& mtx, const SigningProvider* keystore, std::map<COutPoint, Coin>& coins, const UniValue& hashType)
+{
     int nHashType = ParseSighashString(hashType);
 
     bool fHashSingle = ((nHashType & ~SIGHASH_ANYONECANPAY) == SIGHASH_SINGLE);

src/rpc/rawtransaction_util.h

@@ -12,19 +12,27 @@ class UniValue;
 struct CMutableTransaction;
 class Coin;
 class COutPoint;
+class SigningProvider;
 
 /**
  * Sign a transaction with the given keystore and previous transactions
  *
  * @param  mtx           The transaction to-be-signed
- * @param  prevTxs       Array of previous txns outputs that tx depends on but may not yet be in the block chain
  * @param  keystore      Temporary keystore containing signing keys
  * @param  coins         Map of unspent outputs - coins in mempool and current chain UTXO set, may be extended by previous txns outputs after call
- * @param  tempKeystore  Whether to use temporary keystore
  * @param  hashType      The signature hash type
  * @returns JSON object with details of signed transaction
  */
-UniValue SignTransaction(CMutableTransaction& mtx, const UniValue& prevTxs, FillableSigningProvider* keystore, std::map<COutPoint, Coin>& coins, bool tempKeystore, const UniValue& hashType);
+UniValue SignTransaction(CMutableTransaction& mtx, const SigningProvider* keystore, std::map<COutPoint, Coin>& coins, const UniValue& hashType);
+
+/**
+  * Parse a prevtxs UniValue array and get the map of coins from it
+  *
+  * @param  prevTxs       Array of previous txns outputs that tx depends on but may not yet be in the block chain
+  * @param  keystore      A pointer to the temprorary keystore if there is one
+  * @param  coins         Map of unspent outputs - coins in mempool and current chain UTXO set, may be extended by previous txns outputs after call
+  */
+void ParsePrevouts(const UniValue& prevTxsUnival, FillableSigningProvider* keystore, std::map<COutPoint, Coin>& coins);
 
 /** Create a transaction from univalue parameters */
 CMutableTransaction ConstructTransaction(const UniValue& inputs_in, const UniValue& outputs_in, const UniValue& locktime);

src/wallet/rpcwallet.cpp

@@ -3372,7 +3372,10 @@ UniValue signrawtransactionwithwallet(const JSONRPCRequest& request)
     }
     pwallet->chain().findCoins(coins);
 
-    return SignTransaction(mtx, request.params[1], &*pwallet->GetLegacyScriptPubKeyMan(), coins, false, request.params[2]);
+    // Parse the prevtxs array
+    ParsePrevouts(request.params[1], nullptr, coins);
+
+    return SignTransaction(mtx, &*pwallet->GetLegacyScriptPubKeyMan(), coins, request.params[2]);
 }
 
 static UniValue rescanblockchain(const JSONRPCRequest& request)