Fix MD2 rounds validation

Reject negative and fractional MD2 round counts before passing the option into the hash implementation. This prevents negative rounds from producing an all-zero digest while preserving zero and positive integer round counts.

Co-authored-by: OpenAI Codex <codex@openai.com>

src/core/operations/MD2.mjs

@@ -6,6 +6,7 @@
 
 import Operation from "../Operation.mjs";
 import {runHash} from "../lib/Hash.mjs";
+import OperationError from "../errors/OperationError.mjs";
 
 /**
  * MD2 operation
@@ -40,7 +41,12 @@ class MD2 extends Operation {
      * @returns {string}
      */
     run(input, args) {
-        return runHash("md2", input, {rounds: args[0]});
+        const rounds = args[0] ?? 18;
+
+        if (!Number.isInteger(rounds) || rounds < 0)
+            throw new OperationError("Rounds must be a non-negative integer");
+
+        return runHash("md2", input, {rounds});
     }
 
 }

tests/operations/tests/Hash.mjs

@@ -19,6 +19,28 @@ TestRegister.addTests([
             }
         ]
     },
+    {
+        name: "MD2 rejects negative rounds",
+        input: "Hello, World!",
+        expectedOutput: "Rounds must be a non-negative integer",
+        recipeConfig: [
+            {
+                "op": "MD2",
+                "args": [-1]
+            }
+        ]
+    },
+    {
+        name: "MD2 rejects fractional rounds",
+        input: "Hello, World!",
+        expectedOutput: "Rounds must be a non-negative integer",
+        recipeConfig: [
+            {
+                "op": "MD2",
+                "args": [1.2]
+            }
+        ]
+    },
     {
         name: "MD4",
         input: "Hello, World!",