From 43dbc696b9e9bb5472b01708d33e022042b5ce3b Mon Sep 17 00:00:00 2001
From: Pol Espinasa <pol.espinasa@uab.cat>
Date: Thu, 7 Nov 2024 19:42:09 +0100
Subject: [PATCH] Decode P2WSH and P2SH if data from prev tx is available on
 decodingawtransaction functions

---
 src/core_write.cpp         | 12 ++++++++--
 src/rpc/rawtransaction.cpp |  6 +++++
 src/script/script.cpp      | 45 ++++++++++++++++++++++++++++++++++++++
 src/script/script.h        |  3 +++
 4 files changed, 64 insertions(+), 2 deletions(-)

diff --git a/src/core_write.cpp b/src/core_write.cpp
index 253dfde1006..4a3b61699de 100644
--- a/src/core_write.cpp
+++ b/src/core_write.cpp
@@ -201,23 +201,31 @@ void TxToUniv(const CTransaction& tx, const uint256& block_hash, UniValue& entry
             o.pushKV("hex", HexStr(txin.scriptSig));
             in.pushKV("scriptSig", std::move(o));
         }
-        if (!tx.vin[i].scriptWitness.IsNull()) {
+
+        if (!txin.scriptWitness.IsNull()) {
             UniValue txinwitness(UniValue::VARR);
             for (const auto& item : tx.vin[i].scriptWitness.stack) {
                 txinwitness.push_back(HexStr(item));
             }
             in.pushKV("txinwitness", std::move(txinwitness));
         }
+
         if (have_undo) {
             const Coin& prev_coin = txundo->vprevout[i];
             const CTxOut& prev_txout = prev_coin.out;
 
             amt_total_in += prev_txout.nValue;
 
+            std::pair<CScript, int> script = GetScriptForTransactionInput(prev_txout.scriptPubKey, txin);
+            UniValue redeemScript(UniValue::VOBJ);
+            ScriptToUniv(script.first, redeemScript, false, true);
+            if (script.second != -2) {
+                in.pushKV("redeemScript", std::move(redeemScript));
+            }
+
             if (verbosity == TxVerbosity::SHOW_DETAILS_AND_PREVOUT) {
                 UniValue o_script_pub_key(UniValue::VOBJ);
                 ScriptToUniv(prev_txout.scriptPubKey, /*out=*/o_script_pub_key, /*include_hex=*/true, /*include_address=*/true);
-
                 UniValue p(UniValue::VOBJ);
                 p.pushKV("generated", bool(prev_coin.fCoinBase));
                 p.pushKV("height", uint64_t(prev_coin.nHeight));
diff --git a/src/rpc/rawtransaction.cpp b/src/rpc/rawtransaction.cpp
index db35421688e..be93794c8c2 100644
--- a/src/rpc/rawtransaction.cpp
+++ b/src/rpc/rawtransaction.cpp
@@ -119,6 +119,12 @@ static std::vector<RPCResult> DecodeTxDoc(const std::string& txid_field_doc)
                 {
                     {RPCResult::Type::STR_HEX, "hex", "hex-encoded witness data (if any)"},
                 }},
+                {RPCResult::Type::OBJ, "redeemScript", /*optional=*/true, "The decoded redeem script",
+                {
+                    {RPCResult::Type::STR, "asm", "Human readable disassembly of the redeem script"},
+                    {RPCResult::Type::STR, "desc", "Descriptor of the redeem script"},
+                    {RPCResult::Type::STR, "type", "Type of the redeem script"},
+                }},
                 {RPCResult::Type::NUM, "sequence", "The script sequence number"},
             }},
         }},
diff --git a/src/script/script.cpp b/src/script/script.cpp
index d650db9a0d6..22a1bf5c604 100644
--- a/src/script/script.cpp
+++ b/src/script/script.cpp
@@ -10,9 +10,13 @@
 #include <hash.h>
 #include <uint256.h>
 #include <util/hash_type.h>
+#include<script/interpreter.h>
 
 #include <string>
 
+
+
+
 CScriptID::CScriptID(const CScript& in) : BaseHash(Hash160(in)) {}
 
 std::string GetOpName(opcodetype opcode)
@@ -387,3 +391,44 @@ bool CheckMinimalPush(const std::vector<unsigned char>& data, opcodetype opcode)
     }
     return true;
 }
+
+std::pair<CScript, int> GetScriptForTransactionInput(CScript prevScript, const CTxIn& txin)
+{
+    bool p2sh = false;
+    if (prevScript.IsPayToScriptHash()) {
+        std::vector <std::vector<unsigned char> > stack;
+        if (!EvalScript(stack, txin.scriptSig, SCRIPT_VERIFY_NONE, BaseSignatureChecker(), SigVersion::BASE)) {
+            return std::make_pair(CScript(), -2);
+        }
+        if (stack.empty()) {
+            return std::make_pair(CScript(), -2);
+        }
+        prevScript = CScript(stack.back().begin(), stack.back().end());
+        p2sh = true;
+    }
+    int witnessversion = 0;
+    std::vector<unsigned char> witnessprogram;
+    if (!prevScript.IsWitnessProgram(witnessversion, witnessprogram)) {
+        // For P2SH, scriptSig is always push-only, so the actual script is only the last stack item
+        // For non-P2SH, prevScript is likely the real script, but not part of this transaction, and scriptSig could very well be executable, so return the latter instead
+        return std::make_pair(p2sh ? prevScript : txin.scriptSig, -1);
+    }
+    Span stack{txin.scriptWitness.stack};
+    if (witnessversion == 0 && witnessprogram.size() == WITNESS_V0_SCRIPTHASH_SIZE) {
+        if (stack.empty()) return std::make_pair(CScript(), -2);  // invalid
+        auto& script_data = stack.back();
+        prevScript = CScript(script_data.begin(), script_data.end());
+        return std::make_pair(prevScript, witnessversion);
+    }
+    if (witnessversion == 1 && witnessprogram.size() == WITNESS_V1_TAPROOT_SIZE && !p2sh) {
+        if (stack.size() >= 2 && !stack.back().empty() && stack.back()[0] == ANNEX_TAG) {
+            SpanPopBack(stack);
+        }
+        if (stack.size() >= 2) {
+            SpanPopBack(stack);  // Ignore control block
+            prevScript = CScript(stack.back().begin(), stack.back().end());
+            return std::make_pair(prevScript, witnessversion);
+        }
+    }
+    return std::make_pair(CScript(), -2);
+}
\ No newline at end of file
diff --git a/src/script/script.h b/src/script/script.h
index f4579849803..1c0310d4d69 100644
--- a/src/script/script.h
+++ b/src/script/script.h
@@ -581,6 +581,9 @@ public:
     }
 };
 
+class CTxIn;
+std::pair<CScript, int> GetScriptForTransactionInput(CScript prevScript, const CTxIn& txin);
+
 struct CScriptWitness
 {
     // Note that this encodes the data elements being pushed, rather than