rpc: decode Miniscript descriptor when possible in decodescript

The descriptor inference logic would previously always use a dummy
signing provider and would never analyze the witness script of a P2WSH
scriptPubKey.

Note even a valid Miniscript might not always be decodable from Script
without more contextual information (for instance the key preimage for a
pk_h).

3 files changed, 7 insertions, 4 deletions

diff --git a/src/core_io.h b/src/core_io.h
index 33e1ad82fc..997f3bfd5b 100644
--- a/src/core_io.h
+++ b/src/core_io.h
@@ -15,6 +15,7 @@ class CBlockHeader;
 class CScript;
 class CTransaction;
 struct CMutableTransaction;
+class SigningProvider;
 class uint256;
 class UniValue;
 class CTxUndo;
@@ -52,7 +53,7 @@ UniValue ValueFromAmount(const CAmount amount);
 std::string FormatScript(const CScript& script);
 std::string EncodeHexTx(const CTransaction& tx, const int serializeFlags = 0);
 std::string SighashToStr(unsigned char sighash_type);
-void ScriptToUniv(const CScript& script, UniValue& out, bool include_hex = true, bool include_address = false);
+void ScriptToUniv(const CScript& script, UniValue& out, bool include_hex = true, bool include_address = false, const SigningProvider* provider = nullptr);
 void TxToUniv(const CTransaction& tx, const uint256& block_hash, UniValue& entry, bool include_hex = true, int serialize_flags = 0, const CTxUndo* txundo = nullptr, TxVerbosity verbosity = TxVerbosity::SHOW_DETAILS);
 
 #endif // BITCOIN_CORE_IO_H
diff --git a/src/core_write.cpp b/src/core_write.cpp
index 300bd30e43..b0e3b0b3c4 100644
--- a/src/core_write.cpp
+++ b/src/core_write.cpp
@@ -147,13 +147,13 @@ std::string EncodeHexTx(const CTransaction& tx, const int serializeFlags)
     return HexStr(ssTx);
 }
 
-void ScriptToUniv(const CScript& script, UniValue& out, bool include_hex, bool include_address)
+void ScriptToUniv(const CScript& script, UniValue& out, bool include_hex, bool include_address, const SigningProvider* provider)
 {
     CTxDestination address;
 
     out.pushKV("asm", ScriptToAsmStr(script));
     if (include_address) {
-        out.pushKV("desc", InferDescriptor(script, DUMMY_SIGNING_PROVIDER)->ToString());
+        out.pushKV("desc", InferDescriptor(script, provider ? *provider : DUMMY_SIGNING_PROVIDER)->ToString());
     }
     if (include_hex) {
         out.pushKV("hex", HexStr(script));
diff --git a/src/rpc/rawtransaction.cpp b/src/rpc/rawtransaction.cpp
index 7704496c10..503099d8a9 100644
--- a/src/rpc/rawtransaction.cpp
+++ b/src/rpc/rawtransaction.cpp
@@ -522,15 +522,17 @@ static RPCHelpMan decodescript()
         if (can_wrap_P2WSH) {
             UniValue sr(UniValue::VOBJ);
             CScript segwitScr;
+            FillableSigningProvider provider;
             if (which_type == TxoutType::PUBKEY) {
                 segwitScr = GetScriptForDestination(WitnessV0KeyHash(Hash160(solutions_data[0])));
             } else if (which_type == TxoutType::PUBKEYHASH) {
                 segwitScr = GetScriptForDestination(WitnessV0KeyHash(uint160{solutions_data[0]}));
             } else {
                 // Scripts that are not fit for P2WPKH are encoded as P2WSH.
+                provider.AddCScript(script);
                 segwitScr = GetScriptForDestination(WitnessV0ScriptHash(script));
             }
-            ScriptToUniv(segwitScr, /*out=*/sr, /*include_hex=*/true, /*include_address=*/true);
+            ScriptToUniv(segwitScr, /*out=*/sr, /*include_hex=*/true, /*include_address=*/true, /*provider=*/&provider);
             sr.pushKV("p2sh-segwit", EncodeDestination(ScriptHash(segwitScr)));
             r.pushKV("segwit", sr);
         }