fix(levm): addmod non-compliance (#1309)

Resolves #1292 Resolves #1294
lambdaclass · Nov 27, 2024 · 3b93170 · 3b93170
1 parent 304cafc
commit 3b93170
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Showing 2 changed files with 47 additions and 13 deletions.
diff --git a/crates/vm/levm/src/opcode_handlers/arithmetic.rs b/crates/vm/levm/src/opcode_handlers/arithmetic.rs
@@ -169,20 +169,16 @@ impl VM {
 
         let augend = current_call_frame.stack.pop()?;
         let addend = current_call_frame.stack.pop()?;
-        let divisor = current_call_frame.stack.pop()?;
-        if divisor.is_zero() {
-            current_call_frame.stack.push(U256::zero())?;
-            return Ok(OpcodeSuccess::Continue);
-        }
-        let (sum, overflow) = augend.overflowing_add(addend);
-        let mut remainder = sum.checked_rem(divisor).ok_or(VMError::Internal(
-            InternalError::ArithmeticOperationDividedByZero,
-        ))?; // Cannot be zero bc if above;
-        if overflow || remainder > divisor {
-            remainder = remainder.overflowing_sub(divisor).0;
-        }
+        let modulus = current_call_frame.stack.pop()?;
 
-        current_call_frame.stack.push(remainder)?;
+        let new_augend = augend.checked_rem(modulus).unwrap_or_default();
+        let new_addend = addend.checked_rem(modulus).unwrap_or_default();
+
+        let (sum, _overflowed) = new_augend.overflowing_add(new_addend);
+
+        let sum_mod = sum.checked_rem(modulus).unwrap_or_default();
+
+        current_call_frame.stack.push(sum_mod)?;
 
         Ok(OpcodeSuccess::Continue)
     }

diff --git a/crates/vm/levm/tests/edge_case_tests.rs b/crates/vm/levm/tests/edge_case_tests.rs
@@ -173,3 +173,41 @@ fn test_non_compliance_calldatacopy_memory_resize() {
         U256::from(64)
     );
 }
+
+#[test]
+fn test_non_compliance_addmod() {
+    let mut vm = new_vm_with_bytecode(Bytes::copy_from_slice(&[
+        0x60, 0x01, 0x60, 5, 0x7f, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+        0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+        0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 8,
+    ]))
+    .unwrap();
+    let mut current_call_frame = vm.call_frames.pop().unwrap();
+    vm.execute(&mut current_call_frame);
+    assert_eq!(
+        current_call_frame.stack.stack.first().unwrap(),
+        &U256::zero()
+    );
+}
+
+#[test]
+fn test_non_compliance_addmod2() {
+    let mut vm = new_vm_with_bytecode(Bytes::copy_from_slice(&[
+        // PUSH20 divisor
+        0x73, 0x12, 0x34, 0x56, 0x78, 0x90, 0x12, 0x34, 0x56, 0x78, 0x90, 0x12, 0x34, 0x56, 0x78,
+        0x90, 0x12, 0x34, 0x56, 0x78, 0x90, // PUSH1 addend
+        0x60, 0x08, // PUSH32 augend
+        0x7F, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+        0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+        0xff, 0xff, 0xfd, // ADDMOD opcode
+        0x08, // STOP opcode
+        0x00,
+    ]))
+    .unwrap();
+    let mut current_call_frame = vm.call_frames.pop().unwrap();
+    vm.execute(&mut current_call_frame);
+    assert_eq!(
+        current_call_frame.stack.stack.first().unwrap(),
+        &U256::from("0xfc7490ee00fc74a0ee00fc7490ee00fc7490ee5")
+    );
+}