From 5b75c477841fa463aad9c6e6d95a98b50ce14dd3 Mon Sep 17 00:00:00 2001
From: Andrew Chow <achow101-github@achow101.com>
Date: Tue, 30 May 2017 15:42:10 -0700
Subject: [PATCH 1/2] Add a valid opcode sanity check to CScript

Added a function in CScript that checks if the script contains valid opcodes.

Add a test for that function
---
 src/script/script.cpp     | 12 ++++++++++++
 src/script/script.h       |  3 +++
 src/test/script_tests.cpp | 14 ++++++++++++++
 3 files changed, 29 insertions(+)

diff --git a/src/script/script.cpp b/src/script/script.cpp
index 70eb8a139..a71fee19c 100644
--- a/src/script/script.cpp
+++ b/src/script/script.cpp
@@ -267,3 +267,15 @@ std::string CScriptWitness::ToString() const
     }
     return ret + ")";
 }
+
+bool CScript::HasValidOps() const
+{
+    CScript::const_iterator it = begin();
+    while (it < end()) {
+        opcodetype opcode;
+        if (!GetOp(it, opcode) || opcode > 0xb9) {
+            return false;
+        }
+    }
+    return true;
+}
diff --git a/src/script/script.h b/src/script/script.h
index 95a5999a1..25b80ef62 100644
--- a/src/script/script.h
+++ b/src/script/script.h
@@ -630,6 +630,9 @@ 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
diff --git a/src/test/script_tests.cpp b/src/test/script_tests.cpp
index 343c645cb..70544cacd 100644
--- a/src/test/script_tests.cpp
+++ b/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()

From ac4e438229134595e949bfedb1f487c71fd45d24 Mon Sep 17 00:00:00 2001
From: Andrew Chow <achow101-github@achow101.com>
Date: Tue, 30 May 2017 15:43:07 -0700
Subject: [PATCH 2/2] Sanity check transaction scripts in DecodeHexTx

Make sure that the scripts of decoded transactions are valid scripts.
---
 src/core_read.cpp     | 29 ++++++++++++++++++++++++++---
 src/script/script.cpp |  3 ++-
 src/script/script.h   |  3 +++
 3 files changed, 31 insertions(+), 4 deletions(-)

diff --git a/src/core_read.cpp b/src/core_read.cpp
index a8d667e3b..463871d17 100644
--- a/src/core_read.cpp
+++ b/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;
             }
         }
@@ -111,8 +133,9 @@ 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;
diff --git a/src/script/script.cpp b/src/script/script.cpp
index a71fee19c..a10b619f7 100644
--- a/src/script/script.cpp
+++ b/src/script/script.cpp
@@ -273,7 +273,8 @@ bool CScript::HasValidOps() const
     CScript::const_iterator it = begin();
     while (it < end()) {
         opcodetype opcode;
-        if (!GetOp(it, opcode) || opcode > 0xb9) {
+        std::vector<unsigned char> item;
+        if (!GetOp(it, opcode, item) || opcode > MAX_OPCODE || item.size() > MAX_SCRIPT_ELEMENT_SIZE) {
             return false;
         }
     }
diff --git a/src/script/script.h b/src/script/script.h
index 25b80ef62..23706b982 100644
--- a/src/script/script.h
+++ b/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