From f4e86d6421f20f0f147fb0708665869b6ebb8b60 Mon Sep 17 00:00:00 2001
From: billymcbip <245003547+billymcbip@users.noreply.github.com>
Date: Mon, 29 Dec 2025 17:59:10 +0100
Subject: [PATCH] consensus: Verify OP_CHECKCONSOLIDATION (draft)

---
 src/script/interpreter.cpp       |  36 +++++-
 src/script/interpreter.h         |  18 +++
 src/script/script.cpp            |   5 +-
 src/script/script.h              |   5 +-
 src/script/sign.cpp              |   1 +
 src/test/CMakeLists.txt          |   1 +
 src/test/consolidation_tests.cpp | 186 +++++++++++++++++++++++++++++++
 7 files changed, 249 insertions(+), 3 deletions(-)
 create mode 100644 src/test/consolidation_tests.cpp

diff --git a/src/script/interpreter.cpp b/src/script/interpreter.cpp
index ca405c25da20..a00de5daf948 100644
--- a/src/script/interpreter.cpp
+++ b/src/script/interpreter.cpp
@@ -3,6 +3,7 @@
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
+#include <util/hasher.h>
 #include <script/interpreter.h>
 
 #include <crypto/ripemd160.h>
@@ -13,6 +14,8 @@
 #include <tinyformat.h>
 #include <uint256.h>
 
+#include <unordered_set>
+
 typedef std::vector<unsigned char> valtype;
 
 namespace {
@@ -1214,6 +1217,13 @@ bool EvalScript(std::vector<std::vector<unsigned char> >& stack, const CScript&
                 }
                 break;
 
+                case OP_CHECKCONSOLIDATION:
+                {
+                    if (sigversion != SigVersion::TAPSCRIPT) return set_error(serror, SCRIPT_ERR_BAD_OPCODE);
+                    stack.push_back(checker.CheckConsolidation() ? vchTrue : vchFalse);
+                }
+                break;
+
                 default:
                     return set_error(serror, SCRIPT_ERR_BAD_OPCODE);
             }
@@ -1410,6 +1420,23 @@ void PrecomputedTransactionData::Init(const T& txTo, std::vector<CTxOut>&& spent
         m_spent_outputs_ready = true;
     }
 
+    // Precompute consolidation flags
+    if (m_spent_outputs_ready) {
+        m_consolidation_markers.resize(m_spent_outputs.size());
+        std::unordered_set<uint256, SaltedUint256Hasher> seen;
+        for (size_t i = 0; i < m_spent_outputs.size(); ++i) {
+            uint256 scriptHash = Hash(m_spent_outputs[i].scriptPubKey);
+            if (seen.contains(scriptHash)) {
+                m_consolidation_markers[i] = true;
+            } else {
+                m_consolidation_markers[i] = false;
+                seen.insert(scriptHash);
+            }
+        }
+    } else {
+        m_consolidation_markers.clear();
+    }
+
     // Determine which precomputation-impacting features this transaction uses.
     bool uses_bip143_segwit = force;
     bool uses_bip341_taproot = force;
@@ -1825,6 +1852,13 @@ bool GenericTransactionSignatureChecker<T>::CheckSequence(const CScriptNum& nSeq
     return true;
 }
 
+template <class T>
+bool GenericTransactionSignatureChecker<T>::CheckConsolidation() const
+{
+    assert(txdata && nIn < txdata->m_consolidation_markers.size());
+    return txdata->m_consolidation_markers[nIn];
+}
+
 // explicit instantiation
 template class GenericTransactionSignatureChecker<CTransaction>;
 template class GenericTransactionSignatureChecker<CMutableTransaction>;
@@ -1843,7 +1877,7 @@ static bool ExecuteWitnessScript(const std::span<const valtype>& stack_span, con
                 return set_error(serror, SCRIPT_ERR_BAD_OPCODE);
             }
             // New opcodes will be listed here. May use a different sigversion to modify existing opcodes.
-            if (IsOpSuccess(opcode)) {
+            if (IsOpSuccess(opcode) || (opcode == OP_CHECKCONSOLIDATION && (flags & SCRIPT_VERIFY_CC) == 0)) {
                 if (flags & SCRIPT_VERIFY_DISCOURAGE_OP_SUCCESS) {
                     return set_error(serror, SCRIPT_ERR_DISCOURAGE_OP_SUCCESS);
                 }
diff --git a/src/script/interpreter.h b/src/script/interpreter.h
index cbb137e09efb..e61a6875ab9d 100644
--- a/src/script/interpreter.h
+++ b/src/script/interpreter.h
@@ -135,6 +135,10 @@ enum class script_verify_flag_name : uint8_t {
     //
     SCRIPT_VERIFY_TAPROOT,
 
+    // Verify OP_CHECKCONSOLIDATION
+    //
+    SCRIPT_VERIFY_CC,
+
     // Making unknown Taproot leaf versions non-standard
     //
     SCRIPT_VERIFY_DISCOURAGE_UPGRADABLE_TAPROOT_VERSION,
@@ -181,6 +185,9 @@ struct PrecomputedTransactionData
     //! Whether m_spent_outputs is initialized.
     bool m_spent_outputs_ready = false;
 
+    // BIP-CC precomputed consolidation markers.
+    std::vector<bool> m_consolidation_markers;
+
     PrecomputedTransactionData() = default;
 
     /** Initialize this PrecomputedTransactionData with transaction data.
@@ -294,6 +301,11 @@ class BaseSignatureChecker
          return false;
     }
 
+    virtual bool CheckConsolidation() const
+    {
+        return false;
+    }
+
     virtual ~BaseSignatureChecker() = default;
 };
 
@@ -331,6 +343,7 @@ class GenericTransactionSignatureChecker : public BaseSignatureChecker
     bool CheckSchnorrSignature(std::span<const unsigned char> sig, std::span<const unsigned char> pubkey, SigVersion sigversion, ScriptExecutionData& execdata, ScriptError* serror = nullptr) const override;
     bool CheckLockTime(const CScriptNum& nLockTime) const override;
     bool CheckSequence(const CScriptNum& nSequence) const override;
+    bool CheckConsolidation() const override;
 };
 
 using TransactionSignatureChecker = GenericTransactionSignatureChecker<CTransaction>;
@@ -362,6 +375,11 @@ class DeferringSignatureChecker : public BaseSignatureChecker
     {
         return m_checker.CheckSequence(nSequence);
     }
+
+    bool CheckConsolidation() const override
+    {
+        return m_checker.CheckConsolidation();
+    }
 };
 
 /** Compute the BIP341 tapleaf hash from leaf version & script. */
diff --git a/src/script/script.cpp b/src/script/script.cpp
index 829e351be697..81bc7cd258b0 100644
--- a/src/script/script.cpp
+++ b/src/script/script.cpp
@@ -149,6 +149,9 @@ std::string GetOpName(opcodetype opcode)
     // Opcode added by BIP 342 (Tapscript)
     case OP_CHECKSIGADD            : return "OP_CHECKSIGADD";
 
+    // Opcode added by BIP-CC (Tapscript)
+    case OP_CHECKCONSOLIDATION     : return "OP_CHECKCONSOLIDATION";
+
     case OP_INVALIDOPCODE          : return "OP_INVALIDOPCODE";
 
     default:
@@ -367,7 +370,7 @@ bool IsOpSuccess(const opcodetype& opcode)
     return opcode == 80 || opcode == 98 || (opcode >= 126 && opcode <= 129) ||
            (opcode >= 131 && opcode <= 134) || (opcode >= 137 && opcode <= 138) ||
            (opcode >= 141 && opcode <= 142) || (opcode >= 149 && opcode <= 153) ||
-           (opcode >= 187 && opcode <= 254);
+           (opcode >= 188 && opcode <= 254);
 }
 
 bool CheckMinimalPush(const std::vector<unsigned char>& data, opcodetype opcode) {
diff --git a/src/script/script.h b/src/script/script.h
index b06be9c975d3..9d3da9d52ee2 100644
--- a/src/script/script.h
+++ b/src/script/script.h
@@ -209,6 +209,9 @@ enum opcodetype
     // Opcode added by BIP 342 (Tapscript)
     OP_CHECKSIGADD = 0xba,
 
+    // Opcode added by BIP-CC (Tapscript)
+    OP_CHECKCONSOLIDATION = 0xbb,
+
     OP_INVALIDOPCODE = 0xff,
 };
 
@@ -598,7 +601,7 @@ class CScriptID : public BaseHash<uint160>
     explicit CScriptID(const uint160& in) : BaseHash(in) {}
 };
 
-/** Test for OP_SUCCESSx opcodes as defined by BIP342. */
+/** Test for current OP_SUCCESSx opcodes. */
 bool IsOpSuccess(const opcodetype& opcode);
 
 bool CheckMinimalPush(const std::vector<unsigned char>& data, opcodetype opcode);
diff --git a/src/script/sign.cpp b/src/script/sign.cpp
index 9ea2157f349a..12fb016d563d 100644
--- a/src/script/sign.cpp
+++ b/src/script/sign.cpp
@@ -931,6 +931,7 @@ class DummySignatureChecker final : public BaseSignatureChecker
     bool CheckSchnorrSignature(std::span<const unsigned char> sig, std::span<const unsigned char> pubkey, SigVersion sigversion, ScriptExecutionData& execdata, ScriptError* serror) const override { return sig.size() != 0; }
     bool CheckLockTime(const CScriptNum& nLockTime) const override { return true; }
     bool CheckSequence(const CScriptNum& nSequence) const override { return true; }
+    bool CheckConsolidation() const override { return true; }
 };
 }
 
diff --git a/src/test/CMakeLists.txt b/src/test/CMakeLists.txt
index 83cb989aa9b1..6f23344e613a 100644
--- a/src/test/CMakeLists.txt
+++ b/src/test/CMakeLists.txt
@@ -35,6 +35,7 @@ add_executable(test_bitcoin
   coinstatsindex_tests.cpp
   common_url_tests.cpp
   compress_tests.cpp
+  consolidation_tests.cpp
   crypto_tests.cpp
   cuckoocache_tests.cpp
   dbwrapper_tests.cpp
diff --git a/src/test/consolidation_tests.cpp b/src/test/consolidation_tests.cpp
new file mode 100644
index 000000000000..9503b825d3d5
--- /dev/null
+++ b/src/test/consolidation_tests.cpp
@@ -0,0 +1,186 @@
+// Copyright (c) 2025-present The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or https://opensource.org/license/mit.
+
+#include <consensus/amount.h>
+#include <policy/policy.h>
+#include <primitives/transaction.h>
+#include <script/interpreter.h>
+#include <script/script.h>
+#include <script/sign.h>
+#include <script/signingprovider.h>
+#include <uint256.h>
+#include <util/strencodings.h>
+
+#include <test/util/setup_common.h>
+
+#include <boost/test/tools/old/interface.hpp>
+#include <boost/test/unit_test.hpp>
+
+#include <vector>
+
+BOOST_FIXTURE_TEST_SUITE(consolidation_tests, BasicTestingSetup)
+
+namespace {
+
+struct ConsolidationTaproot
+{
+    CKey key;
+    XOnlyPubKey internal_key;
+    CScript script_pubkey;
+    CScript tapscript;
+    std::vector<unsigned char> control;
+    uint256 merkle_root;
+};
+
+/** Build a taproot output with a key path and a single tapscript leaf of OP_CHECKCONSOLIDATION. */
+ConsolidationTaproot MakeConsolidationTaproot()
+{
+    ConsolidationTaproot out;
+    out.key.MakeNewKey(true);
+    out.internal_key = XOnlyPubKey(out.key.GetPubKey());
+    out.tapscript = CScript() << OP_CHECKCONSOLIDATION;
+
+    TaprootBuilder builder;
+    builder.Add(0, std::span<const unsigned char>{out.tapscript}, TAPROOT_LEAF_TAPSCRIPT);
+    builder.Finalize(out.internal_key);
+    const TaprootSpendData spenddata = builder.GetSpendData();
+
+    out.merkle_root = spenddata.merkle_root;
+    out.script_pubkey = GetScriptForDestination(builder.GetOutput());
+
+    auto it = spenddata.scripts.find({std::vector<unsigned char>(out.tapscript.begin(), out.tapscript.end()), TAPROOT_LEAF_TAPSCRIPT});
+    assert(it != spenddata.scripts.end());
+    out.control = *it->second.begin();
+    return out;
+}
+
+CMutableTransaction BuildBaseTx()
+{
+    CMutableTransaction mtx;
+    // Key-path input
+    mtx.vin.emplace_back(COutPoint{Txid::FromUint256(uint256(0)), 0});
+    // Script-path input
+    mtx.vin.emplace_back(COutPoint{Txid::FromUint256(uint256(1)), 0});
+    // Output
+    mtx.vout.emplace_back(COIN*2, CScript() << OP_1 << std::vector<unsigned char>(32, 0x01));
+    return mtx;
+}
+
+void SetScriptPathSpend(CTxIn& in, const ConsolidationTaproot& tree)
+{
+    in.scriptWitness.stack.clear();
+    in.scriptWitness.stack.emplace_back(tree.tapscript.begin(), tree.tapscript.end());
+    in.scriptWitness.stack.push_back(tree.control);
+}
+
+void SignKeyPathInput(CTxIn& in, const ConsolidationTaproot& tree, const CMutableTransaction& mtx, unsigned int vin,
+                      const CTxOut& prevout, const PrecomputedTransactionData& txdata)
+{
+    FlatSigningProvider provider;
+    provider.keys.emplace(tree.key.GetPubKey().GetID(), tree.key);
+    std::vector<unsigned char> sig;
+    MutableTransactionSignatureCreator creator(mtx, vin, prevout.nValue, &txdata, SIGHASH_DEFAULT);
+    BOOST_REQUIRE(creator.CreateSchnorrSig(provider, sig, tree.internal_key, nullptr, &tree.merkle_root, SigVersion::TAPROOT));
+    in.scriptWitness.stack.clear();
+    in.scriptWitness.stack.push_back(sig);
+}
+
+bool VerifyInput(const CTransaction& tx, unsigned int vin, const CTxOut& prevout,
+                 const PrecomputedTransactionData& txdata, script_verify_flags flags)
+{
+    ScriptError err = SCRIPT_ERR_OK;
+    return VerifyScript(tx.vin[vin].scriptSig, prevout.scriptPubKey, &tx.vin[vin].scriptWitness, flags,
+                        TransactionSignatureChecker(&tx, vin, prevout.nValue, txdata, MissingDataBehavior::ASSERT_FAIL), &err);
+}
+
+void RunConsolidationCase(const ConsolidationTaproot& key_path_input, const ConsolidationTaproot& script_path_input, script_verify_flags flags)
+{
+    // Build transaction
+    CMutableTransaction mtx = BuildBaseTx();
+    SetScriptPathSpend(mtx.vin[1], script_path_input);
+    const CTxOut prevout0{COIN, key_path_input.script_pubkey};
+    const CTxOut prevout1{COIN, script_path_input.script_pubkey};
+    PrecomputedTransactionData txdata;
+    txdata.Init(CTransaction{mtx}, {prevout0, prevout1}, true);
+    SignKeyPathInput(mtx.vin[0], key_path_input, mtx, 0, prevout0, txdata);
+
+    // Check consolidation markers
+    BOOST_REQUIRE_EQUAL(txdata.m_consolidation_markers.size(), 2U);
+    BOOST_CHECK(!txdata.m_consolidation_markers[0]);
+    const bool same_spk = (key_path_input.script_pubkey == script_path_input.script_pubkey);
+    BOOST_CHECK_EQUAL(txdata.m_consolidation_markers[1], same_spk);
+
+    // Verify inputs
+    const CTransaction tx{mtx};
+    // Key-path input should always verify
+    BOOST_CHECK(VerifyInput(tx, 0, prevout0, txdata, flags));
+    // Script-path input should verify when input SPKs are equal or when SCRIPT_VERIFY_CC is disabled
+    BOOST_CHECK_EQUAL(VerifyInput(tx, 1, prevout1, txdata, flags), same_spk || (flags & SCRIPT_VERIFY_CC) == 0);
+}
+
+}
+
+BOOST_AUTO_TEST_CASE(same_spk)
+{
+    // Same scriptPubKeys, post-activation
+    const ConsolidationTaproot input = MakeConsolidationTaproot();
+    RunConsolidationCase(input, input, MANDATORY_SCRIPT_VERIFY_FLAGS | SCRIPT_VERIFY_CC);
+}
+
+BOOST_AUTO_TEST_CASE(different_spks_post_activation)
+{
+    // Different scriptPubKeys, post-activation
+    const ConsolidationTaproot key_path_input = MakeConsolidationTaproot();
+    const ConsolidationTaproot script_path_input = MakeConsolidationTaproot();
+    BOOST_REQUIRE(key_path_input.script_pubkey != script_path_input.script_pubkey);
+    RunConsolidationCase(key_path_input, script_path_input, MANDATORY_SCRIPT_VERIFY_FLAGS | SCRIPT_VERIFY_CC);
+}
+
+BOOST_AUTO_TEST_CASE(different_spks_pre_activation)
+{
+    // Different scriptPubKeys, pre-activation
+    const ConsolidationTaproot key_path_input = MakeConsolidationTaproot();
+    const ConsolidationTaproot script_path_input = MakeConsolidationTaproot();
+    BOOST_REQUIRE(key_path_input.script_pubkey != script_path_input.script_pubkey);
+    RunConsolidationCase(key_path_input, script_path_input, MANDATORY_SCRIPT_VERIFY_FLAGS);
+}
+
+BOOST_AUTO_TEST_CASE(many_prevouts)
+{
+    // 3 spks, not sorted
+    const ConsolidationTaproot spk1 = MakeConsolidationTaproot();
+    const ConsolidationTaproot spk2 = MakeConsolidationTaproot();
+    const ConsolidationTaproot spk3 = MakeConsolidationTaproot();
+    BOOST_REQUIRE(spk1.script_pubkey != spk2.script_pubkey);
+    BOOST_REQUIRE(spk2.script_pubkey != spk3.script_pubkey);
+    BOOST_REQUIRE(spk1.script_pubkey != spk3.script_pubkey);
+    const CTxOut prevout0{COIN, spk1.script_pubkey}; // 1st spk1, OP_CHECKCONSOLIDATION false
+    const CTxOut prevout1{COIN, spk2.script_pubkey}; // 1st spk2, OP_CHECKCONSOLIDATION false
+    const CTxOut prevout2{COIN, spk2.script_pubkey}; // 2nd spk2, OP_CHECKCONSOLIDATION true
+    const CTxOut prevout3{COIN, spk2.script_pubkey}; // 3rd spk2, OP_CHECKCONSOLIDATION true
+    const CTxOut prevout4{COIN, spk1.script_pubkey}; // 2nd spk1, OP_CHECKCONSOLIDATION true
+    const CTxOut prevout5{COIN, spk3.script_pubkey}; // 1st spk3, OP_CHECKCONSOLIDATION false
+
+    CMutableTransaction mtx;
+    mtx.vin.emplace_back(COutPoint{Txid::FromUint256(uint256(0)), 0});
+    mtx.vin.emplace_back(COutPoint{Txid::FromUint256(uint256(1)), 0});
+    mtx.vin.emplace_back(COutPoint{Txid::FromUint256(uint256(2)), 0});
+    mtx.vin.emplace_back(COutPoint{Txid::FromUint256(uint256(3)), 0});
+    mtx.vin.emplace_back(COutPoint{Txid::FromUint256(uint256(4)), 0});
+    mtx.vin.emplace_back(COutPoint{Txid::FromUint256(uint256(5)), 0});
+    mtx.vout.emplace_back(COIN*6, CScript() << OP_1 << std::vector<unsigned char>(32, 0x01));
+
+    PrecomputedTransactionData txdata;
+    txdata.Init(CTransaction{mtx}, {prevout0, prevout1, prevout2, prevout3, prevout4, prevout5}, true);
+
+    BOOST_REQUIRE_EQUAL(txdata.m_consolidation_markers.size(), 6U);
+    BOOST_CHECK(!txdata.m_consolidation_markers[0]);
+    BOOST_CHECK(!txdata.m_consolidation_markers[1]);
+    BOOST_CHECK(txdata.m_consolidation_markers[2]);
+    BOOST_CHECK(txdata.m_consolidation_markers[3]);
+    BOOST_CHECK(txdata.m_consolidation_markers[4]);
+    BOOST_CHECK(!txdata.m_consolidation_markers[5]);
+}
+
+BOOST_AUTO_TEST_SUITE_END()