Frida: Can't Find Module Loaded Via System.loadLibrary?

by SLV Team 56 views

Hey guys! Ever run into a situation where Frida just refuses to see a module that's clearly loaded in your Android app? It's a head-scratcher, right? Let's dive into a specific scenario where this happens and try to figure out what's going on.

The Problem: Frida Can't See the Module

So, here's the deal. You've got an Android application, and you're loading a native library using System.loadLibrary("a0x9"). You're all set to use Frida to hook into this library, but when you try to find it using Process.getModuleByName('liba0x9.so'), Frida throws an error saying it can't find the module. Bummer! To make matters even more confusing, you've checked the /proc/<pid>/maps file for the process, and the library is definitely there. Talk about frustrating!

[LGE AN10::com.ad2001.a0x9 ]-> var fr09 = Process.getModuleByName('liba0x9.so');
console.log(fr09.base);
Error: unable to find module 'liba0x9.so'
    at value (/frida/runtime/core.js:315)
    at <eval> (<input>:1)
[LGE AN10::com.ad2001.a0x9 ]->

Evidence: The Library Is Loaded

Just to be absolutely sure, you've double-checked /proc/<pid>/maps, and there it is, plain as day:

|:/ # cat /proc/9570/maps |grep 'liba0x9\.so'
1|:/ # cat /proc/9887/maps |grep 'liba0x9\.so'
71f0fd158000-71f0fd159000 r-xp 00000000 08:23 2883799                    /data/app/~~hUUSBr8r9jj6H61oJ58Q3g==/com.ad2001.a0x9-lEXjMqmljssnJwl8opW1JA==/lib/x86_64/liba0x9.so
71f0fd159000-71f0fd15a000 r--p 00000000 08:23 2883799                    /data/app/~~hUUSBr8r9jj6H61oJ58Q3g==/com.ad2001.a0x9-lEXjMqmljssnJwl8opW1JA==/lib/x86_64/liba0x9.so

So, what gives? Why can't Frida see what's right in front of it?

Environment Details

Before we go further, here's the setup:

  • Frida Version: 17.4.0

Possible Causes and Solutions

Okay, let's brainstorm some reasons why this might be happening and what we can do about it.

1. Timing Issues

The most common culprit is timing. Frida might be trying to find the module before it's fully loaded by the application. System.loadLibrary doesn't necessarily load the library instantaneously. There can be a delay, especially during app startup. To fix this, try adding a small delay before calling Process.getModuleByName. You can use setTimeout in your Frida script. For example:

setTimeout(function() {
  try {
    var fr09 = Process.getModuleByName('liba0x9.so');
    console.log("Module base address: " + fr09.base);
  } catch (error) {
    console.error("Error finding module: " + error);
  }
}, 2000); // Wait for 2 seconds

Experiment with the delay time (2000 milliseconds in this case) to find a value that works reliably.

2. Incorrect Module Name

It sounds obvious, but double-check the module name. Make sure you're using the exact filename of the library, including the .so extension. Typos happen! Also, case sensitivity might be a factor on some systems, though Android is generally case-insensitive for filenames. If the filename includes any unusual characters, ensure they're correctly represented in your Frida script. Verify the name against what's listed in /proc/<pid>/maps to be 100% certain.

3. Frida's Context

Frida operates within the context of the target process. Sometimes, especially with complex applications, Frida might be running in a different context or thread where the module isn't yet visible. This is less common, but still worth considering. One potential workaround is to try enumerating all modules and see if your target module appears in the list:

Process.enumerateModules({
    onMatch: function(module) {
        console.log("Module: " + module.name + " at " + module.base);
        if (module.name === 'liba0x9.so') {
            console.log("Found it!");
        }
    },
    onComplete: function() {
        console.log("Module enumeration complete.");
    }
});

This will give you a comprehensive list of all modules Frida can see. If liba0x9.so isn't in that list, it strongly suggests a context or visibility issue.

4. SELinux Restrictions

Security-Enhanced Linux (SELinux) can sometimes interfere with Frida's ability to access certain parts of the process memory. If SELinux is enforcing strict policies, it might be preventing Frida from seeing the loaded library. While disabling SELinux is generally not recommended for security reasons, you can temporarily try setting it to permissive mode to see if it resolves the issue. This is purely for diagnostic purposes!

To check SELinux status:

getenforce

To temporarily set it to permissive (requires root):

setenforce 0

Remember to re-enable SELinux after testing:

setenforce 1

If SELinux is the problem, you'll need to investigate and potentially modify SELinux policies to allow Frida access.

5. Multiple Libraries with the Same Name

In rare cases, there might be multiple libraries with the same name loaded into different memory locations. This could confuse Frida. The enumerateModules method mentioned earlier can help identify if this is the case. If you find multiple entries for liba0x9.so, you'll need to figure out which one you're actually interested in and adjust your Frida script accordingly, possibly by specifying the base address manually.

6. Frida Bug (Less Likely)

While less likely, it's always possible that there's a bug in Frida itself. Given that you're using version 17.4.0, it's a relatively recent version, but bugs can still happen. Check the Frida issue tracker on GitHub to see if anyone else has reported a similar problem. If not, consider creating a new issue with detailed information about your setup and the steps you've taken to reproduce the problem.

Debugging Steps

Here's a step-by-step approach to debugging this issue:

  1. Verify Library Loading: Double-check that the library is actually loaded by the application before you attach Frida. Use adb shell and cat /proc/<pid>/maps | grep liba0x9.so to confirm.
  2. Add a Delay: Implement a setTimeout in your Frida script to give the library time to load.
  3. Enumerate Modules: Use Process.enumerateModules to see all the modules Frida can see.
  4. Check SELinux: Investigate SELinux status and temporarily disable it for testing (with caution!).
  5. Simplify: Try to reproduce the problem with a minimal example application to rule out complexities in your target app.
  6. Update Frida: Although you're on a recent version, check if there's an even newer version available with bug fixes.

Conclusion

Finding that Frida can't see a loaded module is a frustrating experience, but by systematically investigating the possible causes – timing issues, incorrect names, context problems, SELinux restrictions, and potential Frida bugs – you can usually track down the root of the problem and get your Frida scripts working. Good luck, and happy hooking! Remember to always be ethical and responsible when using Frida.