Hook

General

Category
Free
Tag
Instrumentation
License
Apache License, Version 2.0
Registered
Jul 21, 2016
Favorites
0
Link
https://github.com/renaudcerrato/Hook
See also
ddi
javassist-android
JavaPoetic
KPoet
adbi

Additional

Language
Java
Version
1.0.0 (Jul 14, 2016)
Created
Jun 23, 2016
Updated
Nov 22, 2016 (Retired)
Owner
Renaud Cerrato (renaudcerrato)
Contributor
Renaud Cerrato (renaudcerrato)
1
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Announcement

Hook

Minimalist, annotation based, hook framework for Android built on top of AspectJ.

Basic Usage

public class Math {

    @Hooked("my_hook")
    public int add(int a,int b) {
        return a+b;
    }
}

public class IncrementHook {

    @Hook("my_hook")
    int hook(HookedMethod<Integer> method) throws Throwable {
        return method.proceed() + 1; // add one 
    }
}
    
final Math math = new Math();
final IncrementHook hook = new IncrementHook();

Hooker.instance().register(hook);
assertThat(math.add(5, 3), is(9)); // 5 + 3 = 9
Hooker.instance().unregister(hook);
assertThat(math.add(5, 3), is(8)); // 5 + 3 = 8

Annotations

Hook let you easily hook into methods using simple annotations:

@Hooked

In order to be able to hook a method, you must annotate it as @Hooked.

By annotating arguments using @Param annotations, you'll be later able to easily capture them by name (instead of relying on their declaration order) :

 @Hooked("my_hook")
    public int add(@Param("a") int a, @Param("b") int b) {
        return a+b;
    }

@Hook

By using @Hook annotations, you're given a chance to alter arguments and/or the return value of the original @Hooked method. @Hook annotated methods have a mandatory first arguments of type HookedMethod.

You can easily capture arguments by using @Param annotations and you can also capture the enclosing object of the @Hooked method using the @Target annotation:

 @Hook("my_hook")
    int hook(HookedMethod<Integer> method, @Param("a") int a, @Param("b") int b, @Target Math math) throws Throwable {
        return method.proceed(2*a, 2*b); // double operands
    }

Multiple @Hook method can be defined, and you can specify the execution order using the priority parameter:

 @Hook(value="my_hook", priority=1000)
    int highPriorityHook(HookedMethod<Integer> method) throws Throwable {
        return method.proceed();(
    }
    
 @Hook(value="my_hook", priority=1)
    int lowPriorityHook(HookedMethod<Integer> method) throws Throwable {
        return method.proceed();
    }

@Call

If you don't mind altering arguments nor the return value, you can use @Call annotations instead. Since @Call methods will be invoked first (i.e before any @Hook annotated methods), you can be sure that arguments have not been altered.

  @Call("my_hook")
    void call(int a, int b) {
        ...
    }

Both @Param and @Target capture annotations are supported.

@Before

@Before annotated methods are called right before the original method is called - that mean that both @Call and @Hook method(s) were called already (possibly altering arguments). Of course, @Before methods won't be called if a single @Hook method didn't called HookedMethod::proceed().

 @Before("my_hook")
    void before(int a, int b) {
        ...
    }

Both @Param and @Target capture annotations are supported.

@After

@After annotated methods are called right after the original method is called - but before @Hook annotated methods returns. Of course, @After methods won't be called if a single @Hook method didn't called HookedMethod::proceed().

You can capture the return value using the @Result annotation:

  @After("my_hook")
    void after(@Param("a") int a, @Param("b") int b, @Target Object object, @Result int result) {
        ...
    }

Both @Param and @Target capture annotations are also supported.

@Returning

@Returning annotated methods are called right before returning to the original caller. You can capture the return value using the @Result annotation:

 @Returning("my_hook")
    void returning(@Param("a") int a, @Param("b") int b, @Result int result) {
        ...
    }

Both @Param and @Target capture annotations are also supported.

@Register / @Unregister

@Register annotated methods will automatically register the enclosing instance right before execution, exactly in the same way as if Hooker.instance().register(this) were called on the instance.

@Unregister annotated methods will automatically unregister the enclosing instance right after execution, exactly in the same way as if Hooker.instance().unregister(this) were called on the instance.

public class MainActivity extends Activity {

    @Register
 @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }

    @Unregister
    @Override
    protected void onDestroy() {
        super.onDestroy();
    }
    ...
}

Advanced Usage

public class Math {

    @Hooked("my_hook")
    public int add(@Param("a") int a, @Param("b") int b) {
        System.out.println("    calling add("+a+", "+b+")");
        return a+b;
    }
}

public class Hooks {

 @Before("my_hook")
    void before(int a, int b) {
        System.out.println("  @Before(a="+a+", b="+b+")");
    }

    @Call("my_hook")
    void call(int a, int b) {
        System.out.println("@Call(a="+a+", b="+b+")");
    }

    @After("my_hook")
    void after(@Param("a") int a, @Param("b") int b, @Target Math math, @Result int result) {
        System.out.println("  @After(a="+a+", b="+b+", result="+result+")");
    }

    @Returning("my_hook")
    void returning(@Param("a") int a, @Param("b") int b, @Result int result) {
        System.out.println("@Returning(a="+a+", b="+b+", result="+result+")");
    }

    @Hook("my_hook")
    int hook(HookedMethod<Integer> method, @Param("a") int a, @Param("b") int b, @Target Math math) throws Throwable {
        System.out.println("entering @Hook(a="+a+", b="+b+")");
        int ret = method.proceed(2*a, 2*b) + 1; // double operands and increment result
        System.out.println("exiting @Hook (return "+ret+")");
        return ret;
    }
}

final Math math = new Math();
final Hooks hooks = new Hooks();

Hooker.instance().register(hooks);
assertThat(math.add(5, 3), is(17));
Hooker.instance().unregister(hooks);

For clarity, here's the output of the snippet above :

@Call(a=5, b=3)
entering @Hook(a=5, b=3)
  @Before(a=10, b=6)
    calling add(10, 6)
  @After(a=10, b=6, result=16)
exiting @Hook (return 17)
@Returning(a=10, b=6, result=17)

Installation

Android Studio

The project binaries are hosted on JitPack: the Android integration is made easy thanks to the use of a custom gradle plugin.

Step 1 Import the plugin in your root build.gradle at the buildscript closure:

buildscript {
    repositories {
        ...
        maven { url "https://jitpack.io" }
    }
    dependencies {
        ...
        classpath 'com.github.renaudcerrato.Hook:plugin:1.0.0'
    }
}

Step 2 Add Jitpack in your root build.gradle at the end of repositories:

allprojects {
 repositories {
  ...
  maven { url "https://jitpack.io" }
 }
}

Step 3 Apply the plugin in your app build.gradle:

apply plugin: 'com.android.application'
apply plugin: 'hook'
...

Proguard

Make sure your proguard rule set includes following lines:

-keep class com.mypopsy.hook.** { *; }

-keepclasseswithmembernames class * {
    @com.mypopsy.hook.** <methods>;
}

License

Copyright 2016 Cerrato Renaud

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

   http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.