Merge pull request #3843

787ee0c Check redeemScript size does not exceed 520 byte limit (Peter Todd)
4d79098 Increase IsStandard() scriptSig length (Peter Todd)
f80cffa Do not trigger a DoS ban if SCRIPT_VERIFY_NULLDUMMY fails (Peter Todd)
6380180 Add rejection of non-null CHECKMULTISIG dummy values (Peter Todd)
29c1749 Let tx (in)valid tests use any SCRIPT_VERIFY flag (Peter Todd)
68f7d1d Create (MANDATORY|STANDARD)_SCRIPT_VERIFY_FLAGS constants (Peter Todd)

src/script.h

@@ -190,8 +190,28 @@ enum
     SCRIPT_VERIFY_STRICTENC = (1U << 1), // enforce strict conformance to DER and SEC2 for signatures and pubkeys
     SCRIPT_VERIFY_EVEN_S    = (1U << 2), // enforce even S values in signatures (depends on STRICTENC)
     SCRIPT_VERIFY_NOCACHE   = (1U << 3), // do not store results in signature cache (but do query it)
+    SCRIPT_VERIFY_NULLDUMMY = (1U << 4), // verify dummy stack item consumed by CHECKMULTISIG is of zero-length
 };
 
+// Mandatory script verification flags that all new blocks must comply with for
+// them to be valid. (but old blocks may not comply with) Currently just P2SH,
+// but in the future other flags may be added, such as a soft-fork to enforce
+// strict DER encoding.
+//
+// Failing one of these tests may trigger a DoS ban - see CheckInputs() for
+// details.
+static const unsigned int MANDATORY_SCRIPT_VERIFY_FLAGS = SCRIPT_VERIFY_P2SH;
+
+// Standard script verification flags that standard transactions will comply
+// with. However scripts violating these flags may still be present in valid
+// blocks and we must accept those blocks.
+static const unsigned int STANDARD_SCRIPT_VERIFY_FLAGS = MANDATORY_SCRIPT_VERIFY_FLAGS |
+                                                         SCRIPT_VERIFY_STRICTENC |
+                                                         SCRIPT_VERIFY_NULLDUMMY;
+
+// For convenience, standard but not mandatory verify flags.
+static const unsigned int STANDARD_NOT_MANDATORY_VERIFY_FLAGS = STANDARD_SCRIPT_VERIFY_FLAGS & ~MANDATORY_SCRIPT_VERIFY_FLAGS;
+
 enum txnouttype
 {
     TX_NONSTANDARD,