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)

1 files changed, 27 insertions, 11 deletions

diff --git a/src/main.cpp b/src/main.cpp
index 83a640d7f3..a0f4f40cb1 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -515,10 +515,14 @@ bool IsStandardTx(const CTransaction& tx, string& reason)
 
     BOOST_FOREACH(const CTxIn& txin, tx.vin)
     {
-        // Biggest 'standard' txin is a 3-signature 3-of-3 CHECKMULTISIG
-        // pay-to-script-hash, which is 3 ~80-byte signatures, 3
-        // ~65-byte public keys, plus a few script ops.
-        if (txin.scriptSig.size() > 500) {
+        // Biggest 'standard' txin is a 15-of-15 P2SH multisig with compressed
+        // keys. (remember the 520 byte limit on redeemScript size) That works
+        // out to a (15*(33+1))+3=513 byte redeemScript, 513+1+15*(73+1)=1624
+        // bytes of scriptSig, which we round off to 1650 bytes for some minor
+        // future-proofing. That's also enough to spend a 20-of-20
+        // CHECKMULTISIG scriptPubKey, though such a scriptPubKey is not
+        // considered standard)
+        if (txin.scriptSig.size() > 1650) {
             reason = "scriptsig-size";
             return false;
         }
@@ -945,7 +949,7 @@ bool AcceptToMemoryPool(CTxMemPool& pool, CValidationState &state, const CTransa
 
         // Check against previous transactions
         // This is done last to help prevent CPU exhaustion denial-of-service attacks.
-        if (!CheckInputs(tx, state, view, true, SCRIPT_VERIFY_P2SH | SCRIPT_VERIFY_STRICTENC))
+        if (!CheckInputs(tx, state, view, true, STANDARD_SCRIPT_VERIFY_FLAGS))
         {
             return error("AcceptToMemoryPool: : ConnectInputs failed %s", hash.ToString());
         }
@@ -1588,14 +1592,26 @@ bool CheckInputs(const CTransaction& tx, CValidationState &state, CCoinsViewCach
                     pvChecks->push_back(CScriptCheck());
                     check.swap(pvChecks->back());
                 } else if (!check()) {
-                    if (flags & SCRIPT_VERIFY_STRICTENC) {
-                        // For now, check whether the failure was caused by non-canonical
-                        // encodings or not; if so, don't trigger DoS protection.
-                        CScriptCheck check(coins, tx, i, flags & (~SCRIPT_VERIFY_STRICTENC), 0);
+                    if (flags & STANDARD_NOT_MANDATORY_VERIFY_FLAGS) {
+                        // Check whether the failure was caused by a
+                        // non-mandatory script verification check, such as
+                        // non-standard DER encodings or non-null dummy
+                        // arguments; if so, don't trigger DoS protection to
+                        // avoid splitting the network between upgraded and
+                        // non-upgraded nodes.
+                        CScriptCheck check(coins, tx, i,
+                                flags & ~STANDARD_NOT_MANDATORY_VERIFY_FLAGS, 0);
                         if (check())
-                            return state.Invalid(false, REJECT_NONSTANDARD, "non-canonical");
+                            return state.Invalid(false, REJECT_NONSTANDARD, "non-mandatory-script-verify-flag");
                     }
-                    return state.DoS(100,false, REJECT_NONSTANDARD, "non-canonical");
+                    // Failures of other flags indicate a transaction that is
+                    // invalid in new blocks, e.g. a invalid P2SH. We DoS ban
+                    // such nodes as they are not following the protocol. That
+                    // said during an upgrade careful thought should be taken
+                    // as to the correct behavior - we may want to continue
+                    // peering with non-upgraded nodes even after a soft-fork
+                    // super-majority vote has passed.
+                    return state.DoS(100,false, REJECT_INVALID, "mandatory-script-verify-flag-failed");
                 }
             }
         }