调试抖音App(教程)

一、使用MonkeyDev建立空的工程，拖入IPA到目标文件夹中

1）启动Xcode进行编译执行

一起动就crash，说明签名校验已经通过。

1
LLVM Profile Error: Failed to write file “default.profraw”: Operation not permitted
　　遇到上面的错误，经过查询说是，抖音App内部通过ptrace判断是否有调试器挂载，判断反调试的功能。

通过打开下面的代码进行修改，可以避免crash

2）启动起来之后，可以调试，如下图

3）通过class dump dump出来可执行文件，得到头文件列表

4）Hook测试

追加代码：

通过提示框证明代码已经成功注入，下一步就是进行实质分析

二、路径Shader提取

通过dump出的代码，发现文件

@interface HTSGLProgram : NSObject
{
    NSMutableArray *attributes;
    NSMutableArray *uniforms;
    unsigned int program;
    unsigned int vertShader;
    unsigned int fragShader;
    _Bool _initialized;
    NSString *_vertexShaderLog;
    NSString *_fragmentShaderLog;
    NSString *_programLog;
}
 
@property(copy, nonatomic) NSString *programLog; // @synthesize programLog=_programLog;
@property(copy, nonatomic) NSString *fragmentShaderLog; // @synthesize fragmentShaderLog=_fragmentShaderLog;
@property(copy, nonatomic) NSString *vertexShaderLog; // @synthesize vertexShaderLog=_vertexShaderLog;
@property(nonatomic) _Bool initialized; // @synthesize initialized=_initialized;
- (void).cxx_destruct;
- (void)dealloc;
- (void)validate;
- (void)use;
- (_Bool)link;
- (unsigned int)uniformIndex:(id)arg1;
- (unsigned int)attributeIndex:(id)arg1;
- (void)addAttribute:(id)arg1;
- (_Bool)compileShader:(unsigned int *)arg1 type:(unsigned int)arg2 string:(id)arg3;
- (id)initWithVertexShaderString:(id)arg1 fragmentShaderString:(id)arg2;
 

可以看到初始化方法中传入顶点着色器

编写hook方法：

CHDeclareClass(HTSGLProgram)
CHOptimizedMethod2(self,
                   id,
                   HTSGLProgram,
                   initWithVertexShaderString,
                   NSString *,
                   VertexShaderString,
                   fragmentShaderString,
                   NSString *, fragmentShaderString)
{
     
    NSLog(@"filter initWithVertexShaderString arg1 = %@ fragmentShaderString arg2 = %@",
          VertexShaderString, fragmentShaderString);
 
    return CHSuper2(HTSGLProgram, initWithVertexShaderString, VertexShaderString, fragmentShaderString, fragmentShaderString);
}
 
CHOptimizedMethod3(self, BOOL, HTSGLProgram, compileShader, unsigned int *, arg1, type, unsigned int, arg2, string, NSString *, arg3)
{
    NSLog(@"HTSGLProgram compileShader arg3 = %@",arg3);
    return CHSuper3(HTSGLProgram, compileShader, arg1, type, arg2, string, arg3);
}
 
CHConstructor{
    CHLoadLateClass(HTSGLProgram);
    CHHook2(HTSGLProgram, initWithVertexShaderString, fragmentShaderString);
    CHHook3(HTSGLProgram, compileShader, type, string);
}

得到log

2018-09-18 16:24:00.025744+0800 Aweme[446:72758] HTSGLProgram compileShader arg3 = attribute vec4 position; attribute vec4 inputTextureCoordinate; varying vec2 textureCoordinate; void main() { gl_Position = position; textureCoordinate = inputTextureCoordinate.xy; }

2018-09-18 16:24:00.025772+0800 Aweme[446:72758] HTSGLProgram compileShader arg3 = varying highp vec2 textureCoordinate; uniform sampler2D luminanceTexture; uniform sampler2D chrominanceTexture; uniform mediump mat3 colorConversionMatrix; void main() { mediump vec3 yuv; mediump vec3 rgb; yuv.x = texture2D(luminanceTexture, textureCoordinate).r; yuv.yz = texture2D(chrominanceTexture, textureCoordinate).ra - vec2(0.5, 0.5); rgb = colorConversionMatrix * yuv; gl_FragColor = vec4(rgb, 1); }

这里貌似处理的算法不在shader中，而是一个通用的脚本，具体参数在.m文件中

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