remove block (multi)signature malleability vectors

src/pow.cpp

@@ -61,7 +61,27 @@ bool CheckProof(const CBlockHeader& block, const Consensus::Params& params)
 {
     if (block.GetHash() == params.hashGenesisBlock)
        return true;
-    return GenericVerifyScript(block.proof.solution, block.proof.challenge, SCRIPT_VERIFY_P2SH, block);
+
+    // Some important anti-DoS flags.
+    // Note: Blockhashes do not commit to the proof.
+    // Therefore we may have a signature be mealleated
+    // to stay valid, but cause the block to fail
+    // validation, in this case, block weight.
+    // In that case, the block will be marked as permanently
+    // invalid and not processed.
+    // NOTE: These have only been deemed sufficient for OP_CMS
+    // ANY OTHER SCRIPT TYPE MAY REQUIRE DIFFERENT FLAGS/CONSIDERATIONS
+    // TODO: Better design to not have to worry about script specifics
+    // i.e. exempt block header solution from weight limit
+    unsigned int proof_flags = SCRIPT_VERIFY_P2SH // Just allows P2SH evaluation
+        | SCRIPT_VERIFY_STRICTENC // Minimally-sized DER sigs
+        | SCRIPT_VERIFY_NULLDUMMY // No extra data stuffed into OP_CMS witness
+        | SCRIPT_VERIFY_CLEANSTACK // No extra pushes leftover in witness
+        | SCRIPT_VERIFY_MINIMALDATA // Pushes are minimally-sized
+        | SCRIPT_VERIFY_SIGPUSHONLY // Witness is push-only
+        | SCRIPT_VERIFY_LOW_S // Stop easiest signature fiddling
+        | SCRIPT_VERIFY_WITNESS; // Required for cleanstack eval in VerifyScript
+    return GenericVerifyScript(block.proof.solution, block.proof.challenge, proof_flags, block);
 }
 
 bool MaybeGenerateProof(CBlockHeader *pblock, CWallet *pwallet)