Add logic to limit expensive operations in script

Author: junbeomlee

vm/src/executor.rs

@@ -18,7 +18,7 @@ use ccrypto::{blake256, keccak256, ripemd160, sha256};
 use ckey::{verify, Public, Signature, SIGNATURE_LENGTH};
 use primitives::H256;
 
-use instruction::{is_valid_unlock_script, Instruction};
+use instruction::{has_expensive_opcodes, is_valid_unlock_script, Instruction};
 
 const DEFAULT_MAX_MEMORY: usize = 1024;
 
@@ -152,6 +152,10 @@ pub fn execute(
         return Ok(ScriptResult::Fail)
     }
 
+    if has_expensive_opcodes(unlock) {
+        return Ok(ScriptResult::Fail)
+    }
+
     let param_scripts: Vec<_> = params.iter().map(|p| Instruction::PushB(p.clone())).rev().collect();
     let script = [unlock, &param_scripts, lock].concat();
 

vm/src/instruction.rs

@@ -46,3 +46,28 @@ pub fn is_valid_unlock_script(instrs: &[Instruction]) -> bool {
         _ => false,
     })
 }
+
+pub fn has_expensive_opcodes(instrs: &[Instruction]) -> bool {
+    let count = instrs.iter().filter(|instr| instr == &&Instruction::ChkSig).count();
+    count >= 6
+}
+
+#[test]
+fn should_true_when_script_has_more_than_six_chksig_opcodes() {
+    let expensive_script = vec![
+        Instruction::ChkSig,
+        Instruction::ChkSig,
+        Instruction::ChkSig,
+        Instruction::ChkSig,
+        Instruction::ChkSig,
+        Instruction::ChkSig,
+    ];
+    assert_eq!(has_expensive_opcodes(&expensive_script), true);
+}
+
+#[test]
+fn should_false_when_script_has_lower_than_five_chksig_opcodes() {
+    let unexpensive_script =
+        vec![Instruction::ChkSig, Instruction::ChkSig, Instruction::ChkSig, Instruction::ChkSig, Instruction::ChkSig];
+    assert_eq!(has_expensive_opcodes(&unexpensive_script), false);
+}