Frida

Warnings

• breaking The `frida` Python package version MUST precisely match the version of `frida-server` running on the target device/host. A version mismatch (even minor versions like 17.0.x vs 17.2.x) is the most frequent cause of 'Unable to connect', 'Failed to inject', or 'Lost connection' errors.
  Fix: Ensure `pip install frida` and `frida-server` (on the target) are of the exact same version. Use `frida --version` and `frida-server --version` to verify. If using `frida-tools`, it should also match.
• gotcha Frida operations often require elevated privileges. Attaching to system processes, processes owned by other users, or performing certain injections typically requires root/administrator permissions. Running without sufficient privileges will result in 'access denied' or 'permission denied' errors.
  Fix: Run your Python script or `frida-server` with `sudo` (Linux/macOS) or as Administrator (Windows). Be aware of security implications.
• breaking Major `frida` versions (e.g., from 16.x to 17.x) frequently introduce breaking changes to both the Python API and the underlying JavaScript (GumJS) API. This can lead to scripts failing or behaving unexpectedly after an upgrade.
  Fix: Always consult the official Frida release notes (`github.com/frida/frida/releases`) and Python API documentation (`frida.re/docs/py/`) when upgrading to a new major version to identify and adapt to breaking changes.
• gotcha When injecting a JavaScript script, the Python host script must keep the `session` alive for the JavaScript to continue executing. If the Python script exits or `session.detach()` is called prematurely, the injected script will stop. For long-running monitoring, use `sys.stdin.read()` or block indefinitely waiting for messages.
  Fix: After `script.load()`, ensure your Python script has a blocking call (e.g., `sys.stdin.read()` for user input, or an event loop that processes messages) to prevent premature termination of the Frida session. Implement proper `finally` blocks for `session.detach()`.

Install

• pip install frida Install Frida Python library
• pip install frida-tools Install Frida CLI tools (recommended alongside)

Imports

• frida

  import frida

• Device

  frida.get_local_device()

  Device objects are typically obtained through discovery methods like `frida.get_local_device()`, `frida.get_usb_device()`, or `frida.get_remote_device()`, not directly imported.
• Session

  device.attach(pid)

  Session objects are returned by `device.attach()` or `device.spawn()` methods, not directly imported.
• Script

  session.create_script(source)

  Script objects are created via `session.create_script()` and loaded to execute JavaScript. Older versions might have used `frida.core.Script` for direct instantiation, which is less common for typical use cases now.

Quickstart

This quickstart demonstrates how to attach to an existing process or spawn a new one, inject a basic JavaScript payload to intercept file opening calls, and receive messages from the injected script. It includes platform-specific adjustments for Windows vs. Unix-like systems and error handling for common Frida issues. Ensure `frida-server` is running on a remote target if not working locally.

import frida
import sys
import os
import time

def on_message(message, data):
    print(f"[+] Message from script: {message}, data: {data}")

try:
    # Define a target process. On Windows, try 'notepad.exe'. On Unix-like, try 'bash' or 'sleep 60'.
    # You can set this via an environment variable or change it directly.
    # Example: FRIDA_TARGET_PROCESS=bash python your_script.py
    process_name = os.environ.get('FRIDA_TARGET_PROCESS', 'notepad.exe' if sys.platform == 'win32' else 'bash')

    print(f"[*] Attempting to attach to process: {process_name}")
    session = None
    try:
        session = frida.attach(process_name)
        print(f"[*] Attached to {session.pid}")
    except frida.ProcessNotFoundError:
        print(f"[-] Process '{process_name}' not found. Trying to spawn it.")
        # Spawning might require specific paths or arguments for the process.
        if sys.platform == 'win32':
            spawn_cmd = [process_name] # For notepad.exe
        else:
            # For bash, spawn it with a command that keeps it alive for a bit
            spawn_cmd = [process_name, '-c', 'sleep 60 & exec bash'] # or ['sleep', '60']

        pid = frida.spawn(spawn_cmd)
        session = frida.attach(pid)
        print(f"[*] Spawned PID: {pid}. Attached.")
        # Resume the spawned process if it was suspended (default for frida.spawn)
        frida.resume(pid)
        time.sleep(1) # Give it a moment to stabilize after resume

    script_source = """
    // Example JavaScript payload: Intercept a file opening function.
    // Note: 'open' is common on Unix-like. On Windows, 'CreateFileW' is often used.
    
    var targetFunction = null;
    if (Process.platform === 'windows') {
        targetFunction = Module.findExportByName('kernel32.dll', 'CreateFileW');
        if (targetFunction) {
            Interceptor.attach(targetFunction, {
                onEnter: function(args) {
                    this.filename = Memory.readUtf16String(args[0]);
                    console.log('[JS] CreateFileW() called with filename: ' + this.filename);
                },
                onLeave: function(retval) {
                    // console.log('[JS] CreateFileW() returned: ' + retval);
                }
            });
            console.log('[JS] Frida script for CreateFileW loaded!');
        } else {
            console.log('[JS] CreateFileW not found in kernel32.dll');
        }
    } else {
        targetFunction = Module.findExportByName(null, 'open');
        if (targetFunction) {
            Interceptor.attach(targetFunction, {
                onEnter: function(args) {
                    this.path = Memory.readUtf8String(args[0]);
                    console.log('[JS] open() called with path: ' + this.path);
                },
                onLeave: function(retval) {
                    // console.log('[JS] open() returned: ' + retval);
                }
            });
            console.log('[JS] Frida script for open() loaded!');
        } else {
            console.log('[JS] open not found.');
        }
    }
    console.log('[JS] Frida script initialization complete!');
    """

    script = session.create_script(script_source)
    script.on('message', on_message) # Attach a Python callback for messages from the JS script
    script.load() # Inject and execute the JavaScript

    print("[+] Script loaded. Intercepting calls. Press Enter to detach and exit...")
    sys.stdin.read() # Keep the Python script alive to allow interaction

except frida.core.RPCException as e:
    print(f"[-] Frida RPC Error: {e}")
    if "Unable to connect" in str(e) or "Failed to attach" in str(e):
        print("    Hint: Ensure 'frida-server' is running on the target device/host, or that you have sufficient permissions.")
    elif "Process not found" in str(e):
        print("    Hint: The target process might not be running or the name is incorrect.")
except Exception as e:
    print(f"[-] An unexpected error occurred: {e}")
finally:
    if session:
        print("[*] Detaching from process...")
        session.detach()
    print("[*] Exited.")