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.