Add CheckInputs() unit tests

Check that cached script execution results are only valid for the same
script flags; that script execution checks are returned for non-cached
transactions; and that cached results are only valid for transactions
with the same witness hash.

2 files changed, 288 insertions, 2 deletions

diff --git a/src/test/txvalidationcache_tests.cpp b/src/test/txvalidationcache_tests.cpp
index c5367208ba..a74f40251a 100644
--- a/src/test/txvalidationcache_tests.cpp
+++ b/src/test/txvalidationcache_tests.cpp
@@ -10,11 +10,17 @@
 #include "txmempool.h"
 #include "random.h"
 #include "script/standard.h"
+#include "script/sign.h"
 #include "test/test_bitcoin.h"
 #include "utiltime.h"
+#include "core_io.h"
+#include "keystore.h"
+#include "policy/policy.h"
 
 #include <boost/test/unit_test.hpp>
 
+bool CheckInputs(const CTransaction& tx, CValidationState &state, const CCoinsViewCache &inputs, bool fScriptChecks, unsigned int flags, bool cacheSigStore, bool cacheFullScriptStore, PrecomputedTransactionData& txdata, std::vector<CScriptCheck> *pvChecks);
+
 BOOST_AUTO_TEST_SUITE(tx_validationcache_tests)
 
 static bool
@@ -84,4 +90,282 @@ BOOST_FIXTURE_TEST_CASE(tx_mempool_block_doublespend, TestChain100Setup)
     BOOST_CHECK_EQUAL(mempool.size(), 0);
 }
 
+// Run CheckInputs (using pcoinsTip) on the given transaction, for all script
+// flags.  Test that CheckInputs passes for all flags that don't overlap with
+// the failing_flags argument, but otherwise fails.
+// CHECKLOCKTIMEVERIFY and CHECKSEQUENCEVERIFY (and future NOP codes that may
+// get reassigned) have an interaction with DISCOURAGE_UPGRADABLE_NOPS: if
+// the script flags used contain DISCOURAGE_UPGRADABLE_NOPS but don't contain
+// CHECKLOCKTIMEVERIFY (or CHECKSEQUENCEVERIFY), but the script does contain
+// OP_CHECKLOCKTIMEVERIFY (or OP_CHECKSEQUENCEVERIFY), then script execution
+// should fail.
+// Capture this interaction with the upgraded_nop argument: set it when evaluating
+// any script flag that is implemented as an upgraded NOP code.
+void ValidateCheckInputsForAllFlags(CMutableTransaction &tx, uint32_t failing_flags, bool add_to_cache, bool upgraded_nop)
+{
+    PrecomputedTransactionData txdata(tx);
+    // If we add many more flags, this loop can get too expensive, but we can
+    // rewrite in the future to randomly pick a set of flags to evaluate.
+    for (uint32_t test_flags=0; test_flags < (1U << 16); test_flags += 1) {
+        CValidationState state;
+        // Filter out incompatible flag choices
+        if ((test_flags & SCRIPT_VERIFY_CLEANSTACK)) {
+            // CLEANSTACK requires P2SH and WITNESS, see VerifyScript() in
+            // script/interpreter.cpp
+            test_flags |= SCRIPT_VERIFY_P2SH | SCRIPT_VERIFY_WITNESS;
+        }
+        if ((test_flags & SCRIPT_VERIFY_WITNESS)) {
+            // WITNESS requires P2SH
+            test_flags |= SCRIPT_VERIFY_P2SH;
+        }
+        bool ret = CheckInputs(tx, state, pcoinsTip, true, test_flags, true, add_to_cache, txdata, nullptr);
+        // CheckInputs should succeed iff test_flags doesn't intersect with
+        // failing_flags
+        bool expected_return_value = !(test_flags & failing_flags);
+        if (expected_return_value && upgraded_nop) {
+            // If the script flag being tested corresponds to an upgraded NOP,
+            // then script execution should fail if DISCOURAGE_UPGRADABLE_NOPS
+            // is set.
+            expected_return_value = !(test_flags & SCRIPT_VERIFY_DISCOURAGE_UPGRADABLE_NOPS);
+        }
+        BOOST_CHECK_EQUAL(ret, expected_return_value);
+
+        // Test the caching
+        if (ret && add_to_cache) {
+            // Check that we get a cache hit if the tx was valid
+            std::vector<CScriptCheck> scriptchecks;
+            BOOST_CHECK(CheckInputs(tx, state, pcoinsTip, true, test_flags, true, add_to_cache, txdata, &scriptchecks));
+            BOOST_CHECK(scriptchecks.empty());
+        } else {
+            // Check that we get script executions to check, if the transaction
+            // was invalid, or we didn't add to cache.
+            std::vector<CScriptCheck> scriptchecks;
+            BOOST_CHECK(CheckInputs(tx, state, pcoinsTip, true, test_flags, true, add_to_cache, txdata, &scriptchecks));
+            BOOST_CHECK_EQUAL(scriptchecks.size(), tx.vin.size());
+        }
+    }
+}
+
+BOOST_FIXTURE_TEST_CASE(checkinputs_test, TestChain100Setup)
+{
+    // Test that passing CheckInputs with one set of script flags doesn't imply
+    // that we would pass again with a different set of flags.
+    InitScriptExecutionCache();
+
+    CScript p2pk_scriptPubKey = CScript() << ToByteVector(coinbaseKey.GetPubKey()) << OP_CHECKSIG;
+    CScript p2sh_scriptPubKey = GetScriptForDestination(CScriptID(p2pk_scriptPubKey));
+    CScript p2pkh_scriptPubKey = GetScriptForDestination(coinbaseKey.GetPubKey().GetID());
+    CScript p2wpkh_scriptPubKey = GetScriptForWitness(p2pkh_scriptPubKey);
+
+    CBasicKeyStore keystore;
+    keystore.AddKey(coinbaseKey);
+    keystore.AddCScript(p2pk_scriptPubKey);
+
+    // flags to test: SCRIPT_VERIFY_CHECKLOCKTIMEVERIFY, SCRIPT_VERIFY_CHECKSEQUENCE_VERIFY, SCRIPT_VERIFY_NULLDUMMY, uncompressed pubkey thing
+
+    // Create 2 outputs that match the three scripts above, spending the first
+    // coinbase tx.
+    CMutableTransaction spend_tx;
+
+    spend_tx.nVersion = 1;
+    spend_tx.vin.resize(1);
+    spend_tx.vin[0].prevout.hash = coinbaseTxns[0].GetHash();
+    spend_tx.vin[0].prevout.n = 0;
+    spend_tx.vout.resize(4);
+    spend_tx.vout[0].nValue = 11*CENT;
+    spend_tx.vout[0].scriptPubKey = p2sh_scriptPubKey;
+    spend_tx.vout[1].nValue = 11*CENT;
+    spend_tx.vout[1].scriptPubKey = p2wpkh_scriptPubKey;
+    spend_tx.vout[2].nValue = 11*CENT;
+    spend_tx.vout[2].scriptPubKey = CScript() << OP_CHECKLOCKTIMEVERIFY << OP_DROP << ToByteVector(coinbaseKey.GetPubKey()) << OP_CHECKSIG;
+    spend_tx.vout[3].nValue = 11*CENT;
+    spend_tx.vout[3].scriptPubKey = CScript() << OP_CHECKSEQUENCEVERIFY << OP_DROP << ToByteVector(coinbaseKey.GetPubKey()) << OP_CHECKSIG;
+
+    // Sign, with a non-DER signature
+    {
+        std::vector<unsigned char> vchSig;
+        uint256 hash = SignatureHash(p2pk_scriptPubKey, spend_tx, 0, SIGHASH_ALL, 0, SIGVERSION_BASE);
+        BOOST_CHECK(coinbaseKey.Sign(hash, vchSig));
+        vchSig.push_back((unsigned char) 0); // padding byte makes this non-DER
+        vchSig.push_back((unsigned char)SIGHASH_ALL);
+        spend_tx.vin[0].scriptSig << vchSig;
+    }
+
+    LOCK(cs_main);
+
+    // Test that invalidity under a set of flags doesn't preclude validity
+    // under other (eg consensus) flags.
+    // spend_tx is invalid according to DERSIG
+    CValidationState state;
+    {
+        PrecomputedTransactionData ptd_spend_tx(spend_tx);
+
+        BOOST_CHECK(!CheckInputs(spend_tx, state, pcoinsTip, true, SCRIPT_VERIFY_P2SH | SCRIPT_VERIFY_DERSIG, true, true, ptd_spend_tx, nullptr));
+
+        // If we call again asking for scriptchecks (as happens in
+        // ConnectBlock), we should add a script check object for this -- we're
+        // not caching invalidity (if that changes, delete this test case).
+        std::vector<CScriptCheck> scriptchecks;
+        BOOST_CHECK(CheckInputs(spend_tx, state, pcoinsTip, true, SCRIPT_VERIFY_P2SH | SCRIPT_VERIFY_DERSIG, true, true, ptd_spend_tx, &scriptchecks));
+        BOOST_CHECK_EQUAL(scriptchecks.size(), 1);
+
+        // Test that CheckInputs returns true iff DERSIG-enforcing flags are
+        // not present.  Don't add these checks to the cache, so that we can
+        // test later that block validation works fine in the absence of cached
+        // successes.
+        ValidateCheckInputsForAllFlags(spend_tx, SCRIPT_VERIFY_DERSIG | SCRIPT_VERIFY_LOW_S | SCRIPT_VERIFY_STRICTENC, false, false);
+
+        // And if we produce a block with this tx, it should be valid (DERSIG not
+        // enabled yet), even though there's no cache entry.
+        CBlock block;
+
+        block = CreateAndProcessBlock({spend_tx}, p2pk_scriptPubKey);
+        BOOST_CHECK(chainActive.Tip()->GetBlockHash() == block.GetHash());
+        BOOST_CHECK(pcoinsTip->GetBestBlock() == block.GetHash());
+    }
+
+    // Test P2SH: construct a transaction that is valid without P2SH, and
+    // then test validity with P2SH.
+    {
+        CMutableTransaction invalid_under_p2sh_tx;
+        invalid_under_p2sh_tx.nVersion = 1;
+        invalid_under_p2sh_tx.vin.resize(1);
+        invalid_under_p2sh_tx.vin[0].prevout.hash = spend_tx.GetHash();
+        invalid_under_p2sh_tx.vin[0].prevout.n = 0;
+        invalid_under_p2sh_tx.vout.resize(1);
+        invalid_under_p2sh_tx.vout[0].nValue = 11*CENT;
+        invalid_under_p2sh_tx.vout[0].scriptPubKey = p2pk_scriptPubKey;
+        std::vector<unsigned char> vchSig2(p2pk_scriptPubKey.begin(), p2pk_scriptPubKey.end());
+        invalid_under_p2sh_tx.vin[0].scriptSig << vchSig2;
+
+        ValidateCheckInputsForAllFlags(invalid_under_p2sh_tx, SCRIPT_VERIFY_P2SH, true, false);
+    }
+
+    // Test CHECKLOCKTIMEVERIFY
+    {
+        CMutableTransaction invalid_with_cltv_tx;
+        invalid_with_cltv_tx.nVersion = 1;
+        invalid_with_cltv_tx.nLockTime = 100;
+        invalid_with_cltv_tx.vin.resize(1);
+        invalid_with_cltv_tx.vin[0].prevout.hash = spend_tx.GetHash();
+        invalid_with_cltv_tx.vin[0].prevout.n = 2;
+        invalid_with_cltv_tx.vin[0].nSequence = 0;
+        invalid_with_cltv_tx.vout.resize(1);
+        invalid_with_cltv_tx.vout[0].nValue = 11*CENT;
+        invalid_with_cltv_tx.vout[0].scriptPubKey = p2pk_scriptPubKey;
+
+        // Sign
+        std::vector<unsigned char> vchSig;
+        uint256 hash = SignatureHash(spend_tx.vout[2].scriptPubKey, invalid_with_cltv_tx, 0, SIGHASH_ALL, 0, SIGVERSION_BASE);
+        BOOST_CHECK(coinbaseKey.Sign(hash, vchSig));
+        vchSig.push_back((unsigned char)SIGHASH_ALL);
+        invalid_with_cltv_tx.vin[0].scriptSig = CScript() << vchSig << 101;
+
+        ValidateCheckInputsForAllFlags(invalid_with_cltv_tx, SCRIPT_VERIFY_CHECKLOCKTIMEVERIFY, true, true);
+
+        // Make it valid, and check again
+        invalid_with_cltv_tx.vin[0].scriptSig = CScript() << vchSig << 100;
+        CValidationState state;
+        PrecomputedTransactionData txdata(invalid_with_cltv_tx);
+        BOOST_CHECK(CheckInputs(invalid_with_cltv_tx, state, pcoinsTip, true, SCRIPT_VERIFY_CHECKLOCKTIMEVERIFY, true, true, txdata, nullptr));
+    }
+
+    // TEST CHECKSEQUENCEVERIFY
+    {
+        CMutableTransaction invalid_with_csv_tx;
+        invalid_with_csv_tx.nVersion = 2;
+        invalid_with_csv_tx.vin.resize(1);
+        invalid_with_csv_tx.vin[0].prevout.hash = spend_tx.GetHash();
+        invalid_with_csv_tx.vin[0].prevout.n = 3;
+        invalid_with_csv_tx.vin[0].nSequence = 100;
+        invalid_with_csv_tx.vout.resize(1);
+        invalid_with_csv_tx.vout[0].nValue = 11*CENT;
+        invalid_with_csv_tx.vout[0].scriptPubKey = p2pk_scriptPubKey;
+
+        // Sign
+        std::vector<unsigned char> vchSig;
+        uint256 hash = SignatureHash(spend_tx.vout[3].scriptPubKey, invalid_with_csv_tx, 0, SIGHASH_ALL, 0, SIGVERSION_BASE);
+        BOOST_CHECK(coinbaseKey.Sign(hash, vchSig));
+        vchSig.push_back((unsigned char)SIGHASH_ALL);
+        invalid_with_csv_tx.vin[0].scriptSig = CScript() << vchSig << 101;
+
+        ValidateCheckInputsForAllFlags(invalid_with_csv_tx, SCRIPT_VERIFY_CHECKSEQUENCEVERIFY, true, true);
+
+        // Make it valid, and check again
+        invalid_with_csv_tx.vin[0].scriptSig = CScript() << vchSig << 100;
+        CValidationState state;
+        PrecomputedTransactionData txdata(invalid_with_csv_tx);
+        BOOST_CHECK(CheckInputs(invalid_with_csv_tx, state, pcoinsTip, true, SCRIPT_VERIFY_CHECKSEQUENCEVERIFY, true, true, txdata, nullptr));
+    }
+
+    // TODO: add tests for remaining script flags
+
+    // Test that passing CheckInputs with a valid witness doesn't imply success
+    // for the same tx with a different witness.
+    {
+        CMutableTransaction valid_with_witness_tx;
+        valid_with_witness_tx.nVersion = 1;
+        valid_with_witness_tx.vin.resize(1);
+        valid_with_witness_tx.vin[0].prevout.hash = spend_tx.GetHash();
+        valid_with_witness_tx.vin[0].prevout.n = 1;
+        valid_with_witness_tx.vout.resize(1);
+        valid_with_witness_tx.vout[0].nValue = 11*CENT;
+        valid_with_witness_tx.vout[0].scriptPubKey = p2pk_scriptPubKey;
+
+        // Sign
+        SignatureData sigdata;
+        ProduceSignature(MutableTransactionSignatureCreator(&keystore, &valid_with_witness_tx, 0, 11*CENT, SIGHASH_ALL), spend_tx.vout[1].scriptPubKey, sigdata);
+        UpdateTransaction(valid_with_witness_tx, 0, sigdata);
+
+        // This should be valid under all script flags.
+        ValidateCheckInputsForAllFlags(valid_with_witness_tx, 0, true, false);
+
+        // Remove the witness, and check that it is now invalid.
+        valid_with_witness_tx.vin[0].scriptWitness.SetNull();
+        ValidateCheckInputsForAllFlags(valid_with_witness_tx, SCRIPT_VERIFY_WITNESS, true, false);
+    }
+
+    {
+        // Test a transaction with multiple inputs.
+        CMutableTransaction tx;
+
+        tx.nVersion = 1;
+        tx.vin.resize(2);
+        tx.vin[0].prevout.hash = spend_tx.GetHash();
+        tx.vin[0].prevout.n = 0;
+        tx.vin[1].prevout.hash = spend_tx.GetHash();
+        tx.vin[1].prevout.n = 1;
+        tx.vout.resize(1);
+        tx.vout[0].nValue = 22*CENT;
+        tx.vout[0].scriptPubKey = p2pk_scriptPubKey;
+
+        // Sign
+        for (int i=0; i<2; ++i) {
+            SignatureData sigdata;
+            ProduceSignature(MutableTransactionSignatureCreator(&keystore, &tx, i, 11*CENT, SIGHASH_ALL), spend_tx.vout[i].scriptPubKey, sigdata);
+            UpdateTransaction(tx, i, sigdata);
+        }
+
+        // This should be valid under all script flags
+        ValidateCheckInputsForAllFlags(tx, 0, true, false);
+
+        // Check that if the second input is invalid, but the first input is
+        // valid, the transaction is not cached.
+        // Invalidate vin[1]
+        tx.vin[1].scriptWitness.SetNull();
+
+        CValidationState state;
+        PrecomputedTransactionData txdata(tx);
+        // This transaction is now invalid under segwit, because of the second input.
+        BOOST_CHECK(!CheckInputs(tx, state, pcoinsTip, true, SCRIPT_VERIFY_P2SH | SCRIPT_VERIFY_WITNESS, true, true, txdata, nullptr));
+
+        std::vector<CScriptCheck> scriptchecks;
+        // Make sure this transaction was not cached (ie because the first
+        // input was valid)
+        BOOST_CHECK(CheckInputs(tx, state, pcoinsTip, true, SCRIPT_VERIFY_P2SH | SCRIPT_VERIFY_WITNESS, true, true, txdata, &scriptchecks));
+        // Should get 2 script checks back -- caching is on a whole-transaction basis.
+        BOOST_CHECK_EQUAL(scriptchecks.size(), 2);
+    }
+}
+
 BOOST_AUTO_TEST_SUITE_END()
diff --git a/src/validation.cpp b/src/validation.cpp
index 945d39876c..d32ba69336 100644
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -190,7 +190,7 @@ enum FlushStateMode {
 static bool FlushStateToDisk(const CChainParams& chainParams, CValidationState &state, FlushStateMode mode, int nManualPruneHeight=0);
 static void FindFilesToPruneManual(std::set<int>& setFilesToPrune, int nManualPruneHeight);
 static void FindFilesToPrune(std::set<int>& setFilesToPrune, uint64_t nPruneAfterHeight);
-static bool CheckInputs(const CTransaction& tx, CValidationState &state, const CCoinsViewCache &inputs, bool fScriptChecks, unsigned int flags, bool cacheSigStore, bool cacheFullScriptStore, PrecomputedTransactionData& txdata, std::vector<CScriptCheck> *pvChecks = nullptr);
+bool CheckInputs(const CTransaction& tx, CValidationState &state, const CCoinsViewCache &inputs, bool fScriptChecks, unsigned int flags, bool cacheSigStore, bool cacheFullScriptStore, PrecomputedTransactionData& txdata, std::vector<CScriptCheck> *pvChecks = nullptr);
 static FILE* OpenUndoFile(const CDiskBlockPos &pos, bool fReadOnly = false);
 
 bool CheckFinalTx(const CTransaction &tx, int flags)
@@ -1232,8 +1232,10 @@ void InitScriptExecutionCache() {
  * Setting cacheSigStore/cacheFullScriptStore to false will remove elements from the corresponding cache
  * which are matched. This is useful for checking blocks where we will likely never need the cache
  * entry again.
+ *
+ * Non-static (and re-declared) in src/test/txvalidationcache_tests.cpp
  */
-static bool CheckInputs(const CTransaction& tx, CValidationState &state, const CCoinsViewCache &inputs, bool fScriptChecks, unsigned int flags, bool cacheSigStore, bool cacheFullScriptStore, PrecomputedTransactionData& txdata, std::vector<CScriptCheck> *pvChecks)
+bool CheckInputs(const CTransaction& tx, CValidationState &state, const CCoinsViewCache &inputs, bool fScriptChecks, unsigned int flags, bool cacheSigStore, bool cacheFullScriptStore, PrecomputedTransactionData& txdata, std::vector<CScriptCheck> *pvChecks)
 {
     if (!tx.IsCoinBase())
     {