From fab15ff70e8db26942db83a9aab7ebf974e8b6b2 Mon Sep 17 00:00:00 2001
From: MarcoFalke <falke.marco@gmail.com>
Date: Wed, 13 Feb 2019 14:25:49 -0500
Subject: fuzz: Script validation flags

---
 src/Makefile.test.include      | 18 +++++++++++
 src/test/fuzz/script_flags.cpp | 72 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 90 insertions(+)
 create mode 100644 src/test/fuzz/script_flags.cpp

diff --git a/src/Makefile.test.include b/src/Makefile.test.include
index f7007050f2..be6633e3d3 100644
--- a/src/Makefile.test.include
+++ b/src/Makefile.test.include
@@ -21,6 +21,7 @@ FUZZ_TARGETS = \
   test/fuzz/inv_deserialize \
   test/fuzz/messageheader_deserialize \
   test/fuzz/netaddr_deserialize \
+  test/fuzz/script_flags \
   test/fuzz/service_deserialize \
   test/fuzz/transaction_deserialize \
   test/fuzz/txoutcompressor_deserialize \
@@ -358,6 +359,23 @@ test_fuzz_netaddr_deserialize_LDADD = \
  $(LIBSECP256K1)
 test_fuzz_netaddr_deserialize_LDADD += $(BOOST_LIBS) $(CRYPTO_LIBS)
 
+test_fuzz_script_flags_SOURCES = $(FUZZ_SUITE) test/fuzz/script_flags.cpp
+test_fuzz_script_flags_CPPFLAGS = $(AM_CPPFLAGS) $(BITCOIN_INCLUDES)
+test_fuzz_script_flags_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
+test_fuzz_script_flags_LDFLAGS = $(RELDFLAGS) $(AM_LDFLAGS) $(LIBTOOL_APP_LDFLAGS)
+test_fuzz_script_flags_LDADD = \
+ $(LIBUNIVALUE) \
+ $(LIBBITCOIN_SERVER) \
+ $(LIBBITCOIN_COMMON) \
+ $(LIBBITCOIN_UTIL) \
+ $(LIBBITCOIN_CONSENSUS) \
+ $(LIBBITCOIN_CRYPTO) \
+ $(LIBBITCOIN_CRYPTO_SSE41) \
+ $(LIBBITCOIN_CRYPTO_AVX2) \
+ $(LIBBITCOIN_CRYPTO_SHANI) \
+ $(LIBSECP256K1)
+test_fuzz_script_flags_LDADD += $(BOOST_LIBS) $(CRYPTO_LIBS)
+
 test_fuzz_service_deserialize_SOURCES = $(FUZZ_SUITE) test/fuzz/deserialize.cpp
 test_fuzz_service_deserialize_CPPFLAGS = $(AM_CPPFLAGS) $(BITCOIN_INCLUDES) -DSERVICE_DESERIALIZE=1
 test_fuzz_service_deserialize_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
diff --git a/src/test/fuzz/script_flags.cpp b/src/test/fuzz/script_flags.cpp
new file mode 100644
index 0000000000..2c0bfa360c
--- /dev/null
+++ b/src/test/fuzz/script_flags.cpp
@@ -0,0 +1,72 @@
+// Copyright (c) 2009-2019 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include <script/interpreter.h>
+#include <script/script.h>
+#include <streams.h>
+#include <version.h>
+
+#include <test/fuzz/fuzz.h>
+
+/** Flags that are not forbidden by an assert */
+static bool IsValidFlagCombination(unsigned flags);
+
+void test_one_input(std::vector<uint8_t> buffer)
+{
+    CDataStream ds(buffer, SER_NETWORK, INIT_PROTO_VERSION);
+    try {
+        int nVersion;
+        ds >> nVersion;
+        ds.SetVersion(nVersion);
+    } catch (const std::ios_base::failure&) {
+        return;
+    }
+
+    try {
+        const CTransaction tx(deserialize, ds);
+        const PrecomputedTransactionData txdata(tx);
+
+        unsigned int verify_flags;
+        ds >> verify_flags;
+
+        if (!IsValidFlagCombination(verify_flags)) return;
+
+        unsigned int fuzzed_flags;
+        ds >> fuzzed_flags;
+
+        for (unsigned i = 0; i < tx.vin.size(); ++i) {
+            CTxOut prevout;
+            ds >> prevout;
+
+            const TransactionSignatureChecker checker{&tx, i, prevout.nValue, txdata};
+
+            ScriptError serror;
+            const bool ret = VerifyScript(tx.vin.at(i).scriptSig, prevout.scriptPubKey, &tx.vin.at(i).scriptWitness, verify_flags, checker, &serror);
+            assert(ret == (serror == SCRIPT_ERR_OK));
+
+            // Verify that removing flags from a passing test or adding flags to a failing test does not change the result
+            if (ret) {
+                verify_flags &= ~fuzzed_flags;
+            } else {
+                verify_flags |= fuzzed_flags;
+            }
+            if (!IsValidFlagCombination(verify_flags)) return;
+
+            ScriptError serror_fuzzed;
+            const bool ret_fuzzed = VerifyScript(tx.vin.at(i).scriptSig, prevout.scriptPubKey, &tx.vin.at(i).scriptWitness, verify_flags, checker, &serror_fuzzed);
+            assert(ret_fuzzed == (serror_fuzzed == SCRIPT_ERR_OK));
+
+            assert(ret_fuzzed == ret);
+        }
+    } catch (const std::ios_base::failure&) {
+        return;
+    }
+}
+
+static bool IsValidFlagCombination(unsigned flags)
+{
+    if (flags & SCRIPT_VERIFY_CLEANSTACK && ~flags & (SCRIPT_VERIFY_P2SH | SCRIPT_VERIFY_WITNESS)) return false;
+    if (flags & SCRIPT_VERIFY_WITNESS && ~flags & SCRIPT_VERIFY_P2SH) return false;
+    return true;
+}
-- 
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