Instrument fs/promises readFile

Author: timokoessler

library/agent/hooks/instrumentation/builtinShim.ts

@@ -23,6 +23,7 @@ export function generateBuildinShim(
     (m) => !methods.some((method) => method.name === m.name)
   );
 
+  // Todos: Copy over properties of patched methods?
   return `
         const orig = process.getBuiltinModule(${JSON.stringify(builtinName)});
         const { __instrumentInspectArgs } = require('@aikidosec/firewall/instrument/internals');

library/agent/hooks/instrumentation/injectedFunctions.ts

@@ -1,5 +1,5 @@
 import { getInstance } from "../../AgentSingleton";
-import { getPackageCallbacks } from "./instructions";
+import { getBuiltinCallbacks, getPackageCallbacks } from "./instructions";
 
 export function __instrumentInspectArgs(
   id: string,
@@ -12,7 +12,13 @@ export function __instrumentInspectArgs(
   }
 
   if (isBuiltin) {
-    // Todo
+    const callbacks = getBuiltinCallbacks(id);
+
+    if (typeof callbacks.inspectArgs === "function") {
+      // Todo support subject?
+      callbacks.inspectArgs(args, agent, undefined);
+    }
+
     return;
   }
 

library/agent/hooks/instrumentation/instructions.ts

@@ -138,3 +138,9 @@ export function getPackageCallbacks(
 ): IntereptorFunctionsObj {
   return packageFileCallbacks.get(identifier) || {};
 }
+
+export function getBuiltinCallbacks(
+  identifier: string
+): IntereptorFunctionsObj {
+  return builtinCallbacks.get(identifier) || {};
+}

library/sinks/FileSystem.ts

@@ -153,8 +153,19 @@ export class FileSystem implements Wrapper {
       this.wrapPromises(exports.promises, pkgInfo);
     });
 
-    hooks
-      .addBuiltinModule("fs/promises")
-      .onRequire((exports, pkgInfo) => this.wrapPromises(exports, pkgInfo));
+    const fsPromises = hooks.addBuiltinModule("fs/promises");
+    fsPromises.onRequire((exports, pkgInfo) =>
+      this.wrapPromises(exports, pkgInfo)
+    );
+    fsPromises.setInstrumentationInstruction({
+      functions: [
+        {
+          name: "readFile",
+          inspectArgs: (args) => {
+            console.log("readFile", args);
+          },
+        },
+      ],
+    });
   }
 }