fix(evm): SHL/SHR shift > 255 check must come before operation

Jon-Becker · Dec 9, 2023 · b440e81 · b440e81
1 parent 92fee5a
commit b440e81
Showing 1 changed file with 4 additions and 13 deletions.
diff --git a/common/src/ether/evm/core/vm.rs b/common/src/ether/evm/core/vm.rs
@@ -637,12 +637,9 @@ impl VM {
                 let a = self.stack.pop();
                 let b = self.stack.pop();
 
-                let mut result = b.value.shl(a.value);
-
                 // if shift is greater than 255, result is 0
-                if a.value > U256::from(255u8) {
-                    result = U256::zero();
-                }
+                let result =
+                    if a.value > U256::from(255u8) { U256::zero() } else { b.value.shl(a.value) };
 
                 // if both inputs are PUSH instructions, simplify the operation
                 let mut simplified_operation = operation;
@@ -660,15 +657,9 @@ impl VM {
                 let a = self.stack.pop();
                 let b = self.stack.pop();
 
-                let mut result = U256::zero();
-                if !b.value.is_zero() {
-                    result = b.value.shr(a.value);
-                }
-
                 // if shift is greater than 255, result is 0
-                if a.value > U256::from(255u8) {
-                    result = U256::zero();
-                }
+                let result =
+                    if a.value > U256::from(255u8) { U256::zero() } else { b.value.shr(a.value) };
 
                 // if both inputs are PUSH instructions, simplify the operation
                 let mut simplified_operation = operation;