[v7.0.11] `Error: expected a pointer` when JVMTI is unavailable

[lorenzodifuccia]

Scripts compiled with frida-java-bridge v7.0.11 crashes with Error: expected a pointer when JVMTI is unavailable.

Issue description:
In lib/class-model.js:1346, the code writes jvmti as a pointer, but jvmti may be null when JVMTI is unavailable.

The function tryGetEnvJvmti (lib/android.js:547-581) tries to find the EnsurePluginLoaded symbol, but libart.so may not have it (like mine, maybe stripped by Samsung? 🤷🏻‍♂️).

As a result, api.jvmti becomes null and writePointer(null) crashes because null is not a Frida pointer object.

Environment:

• Android 9 (SDK 28)
• Device: Samsung Galaxy A8 2018 (SM-A530F)

Test performed:
test.js:

import Java from "frida-java-bridge";

Java.perform(() => { console.log(Java.use('java.lang.String')) })

1. frida-compile test.js -o _test.js
2. frida -UF -l _test.js

Logs:

Error: expected a pointer
    at <anonymous> (node_modules/frida-java-bridge/lib/class-model.js:1352)
    at forEach (native)
    at compileModule (node_modules/frida-java-bridge/lib/class-model.js:1352)
    at ensureInitialized (node_modules/frida-java-bridge/lib/class-model.js:1317)
    at build (node_modules/frida-java-bridge/lib/class-model.js:1227)
    at _make (node_modules/frida-java-bridge/lib/class-factory.js:287)
    at use (node_modules/frida-java-bridge/lib/class-factory.js:158)
    at <anonymous> (node_modules/frida-java-bridge/index.js:404)
    at <anonymous> (node_modules/frida-java-bridge/lib/vm.js:35)
    at _performPendingVmOpsWhenReady (node_modules/frida-java-bridge/index.js:452)
    at perform (node_modules/frida-java-bridge/index.js:377)
    at <anonymous> (test.js:3)

Patch:

--- a/lib/class-model.js
+++ b/lib/class-model.js
@@ -1343,7 +1343,7 @@ function compileModule (env) {
   const field = env.javaLangReflectField();
   let j = javaApi;
   [
-    jvmti,
+    jvmti !== null ? jvmti : ptr(0),
     getDeclaredMethods, getDeclaredFields,
     method.getName, method.getModifiers,
     field.getName, field.getModifiers