Merge #10481: Decodehextx scripts sanity check

ac4e438 Sanity check transaction scripts in DecodeHexTx (Andrew Chow)
5b75c47 Add a valid opcode sanity check to CScript (Andrew Chow)

Tree-SHA512: a516e95c274c9d131123150c798cae8bed75925e8a4d59469967dd7f1d49f7f8161e26afb61024b821bd8dcdffdfd0d19b8dcad20b39b1106820326d8d56904d

src/core_read.cpp

@@ -88,10 +88,32 @@ CScript ParseScript(const std::string& s)
     return result;
 }
 
+// Check that all of the input and output scripts of a transaction contains valid opcodes
+bool CheckTxScriptsSanity(const CMutableTransaction& tx)
+{
+    // Check input scripts for non-coinbase txs
+    if (!CTransaction(tx).IsCoinBase()) {
+        for (unsigned int i = 0; i < tx.vin.size(); i++) {
+            if (!tx.vin[i].scriptSig.HasValidOps() || tx.vin[i].scriptSig.size() > MAX_SCRIPT_SIZE) {
+                return false;
+            }
+        }
+    }
+    // Check output scripts
+    for (unsigned int i = 0; i < tx.vout.size(); i++) {
+        if (!tx.vout[i].scriptPubKey.HasValidOps() || tx.vout[i].scriptPubKey.size() > MAX_SCRIPT_SIZE) {
+            return false;
+        }
+    }
+    
+    return true;
+}
+
 bool DecodeHexTx(CMutableTransaction& tx, const std::string& strHexTx, bool fTryNoWitness)
 {
-    if (!IsHex(strHexTx))
+    if (!IsHex(strHexTx)) {
         return false;
+    }
 
     std::vector<unsigned char> txData(ParseHex(strHexTx));
 
@@ -99,7 +121,7 @@ bool DecodeHexTx(CMutableTransaction& tx, const std::string& strHexTx, bool fTry
         CDataStream ssData(txData, SER_NETWORK, PROTOCOL_VERSION | SERIALIZE_TRANSACTION_NO_WITNESS);
         try {
             ssData >> tx;
-            if (ssData.eof()) {
+            if (ssData.eof() && CheckTxScriptsSanity(tx)) {
                 return true;
             }
         }
@@ -111,9 +133,10 @@ bool DecodeHexTx(CMutableTransaction& tx, const std::string& strHexTx, bool fTry
     CDataStream ssData(txData, SER_NETWORK, PROTOCOL_VERSION);
     try {
         ssData >> tx;
-        if (!ssData.empty())
+        if (!ssData.empty()) {
             return false;
         }
+    }
     catch (const std::exception&) {
         return false;
     }

src/script/script.cpp

@@ -267,3 +267,16 @@ std::string CScriptWitness::ToString() const
     }
     return ret + ")";
 }
+
+bool CScript::HasValidOps() const
+{
+    CScript::const_iterator it = begin();
+    while (it < end()) {
+        opcodetype opcode;
+        std::vector<unsigned char> item;
+        if (!GetOp(it, opcode, item) || opcode > MAX_OPCODE || item.size() > MAX_SCRIPT_ELEMENT_SIZE) {
+            return false;
+        }
+    }
+    return true;
+}

src/script/script.h

@@ -190,6 +190,9 @@ enum opcodetype
     OP_INVALIDOPCODE = 0xff,
 };
 
+// Maximum value that an opcode can be
+static const unsigned int MAX_OPCODE = OP_NOP10;
+
 const char* GetOpName(opcodetype opcode);
 
 class scriptnum_error : public std::runtime_error
@@ -630,6 +633,9 @@ public:
     bool IsPushOnly(const_iterator pc) const;
     bool IsPushOnly() const;
 
+    /** Check if the script contains valid OP_CODES */
+    bool HasValidOps() const;
+
     /**
      * Returns whether the script is guaranteed to fail at execution,
      * regardless of the initial stack. This allows outputs to be pruned

src/test/script_tests.cpp

@@ -1438,4 +1438,18 @@ BOOST_AUTO_TEST_CASE(script_FindAndDelete)
     BOOST_CHECK(s == expect);
 }
 
+BOOST_AUTO_TEST_CASE(script_HasValidOps)
+{
+    // Exercise the HasValidOps functionality
+    CScript script;
+    script = ScriptFromHex("76a9141234567890abcdefa1a2a3a4a5a6a7a8a9a0aaab88ac"); // Normal script
+    BOOST_CHECK(script.HasValidOps());
+    script = ScriptFromHex("76a914ff34567890abcdefa1a2a3a4a5a6a7a8a9a0aaab88ac");
+    BOOST_CHECK(script.HasValidOps());
+    script = ScriptFromHex("ff88ac"); // Script with OP_INVALIDOPCODE explicit
+    BOOST_CHECK(!script.HasValidOps());
+    script = ScriptFromHex("88acc0"); // Script with undefined opcode
+    BOOST_CHECK(!script.HasValidOps());
+}
+
 BOOST_AUTO_TEST_SUITE_END()