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[原创]Dobby框架源码学习
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发表于: 2024-2-25 23:05
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Dobby框架推出的时间也不短了，从Github提交记录上看最早在17年就有提交了。这期间陆陆续续在使用Dobby框架，虽然对原理有大概的了解，但是还是没有从源码上入手分析，这次想完整的梳理下Dobby的实现流程，也就有了这次的文章。
对于Dobby这类inline hook框架的认识，大多数人都知道它的实现是在hook函数时，修改了函数对应汇编代码的前几行指令实现跳转到自定义函数上的，那么就沿着这个角度先从汇编调试上看看Dobby从我们原始程序的修改
使用一个最基本的Demo来作为调试对象
注意：这里直接将Dobby源码作用三方库引入，目前Dobby最新Commit无法编译，需要切换到Commit：0932d69c320e786672361ab53825ba8f4245e9d3
对Java_com_example_dobbytest1_MainActivity_stringFromJNI方法的hook，hook后主动回调原始方法
可能是由于Android Studio版本太新，没找到在Android Studio上使用lldb调试的方式，我就直接使用命令行来操作了
设备端开启lldb-server并启动App
本地使用lldb连接
此时设备端会显示Connection established.，接下里就可以attach对应的pid进行调试了
首先确定断点位置，因为代码中是对Java_com_example_dobbytest1_MainActivity_stringFromJNI进行hook，那么可以断点在该方法的首个指令地址
地址计算可以参考下面的方法
0xb110位置断点
得到结果如下
可以看到Java_com_example_dobbytest1_MainActivity_stringFromJNI函数的头三个指令发生了变化，原本的栈拉伸、寄存器入栈保护等固定指令被替换了，替换成了针对x17地址的跳转指令，看下x17对应的值是什么
x17对应的值是0x00000070ece54290，偏移是0xb290，也就对应着new_Java_com_example_dobbytest1_MainActivity_stringFromJNI方法
那么从这里可以看出，Dobby对函数的hook是通过修改原始函数的前三个指令来完成跳转的，那么指令替换的逻辑是什么我们后续在源码分析中继续跟踪，现在接着往下看
在替换函数中最后我们主动回调了原始函数，在0xb2cc的位置可以再下个断点
在0xb2cc的位置是跳回到原始函数，从调试信息中可以看到，首先是栈拉伸、寄存器入栈保护
可以看到，x17被重新赋予了地址，而这个地址是原始函数的第四行指令，但是这个地址又是怎么被保存下来的呢？同样放在后续源码分析中
在原始函数中继续执行代码会最终走到
完成寄存器恢复以及栈平衡，接着返回到新函数流程内
下面以完整的流程图来展示Dobby inline hook的流程
源码上从dobby.h的DobbyHook入手，源码实现在
关键在于第三步FunctionInlineHookRouting对象的处理，FunctionInlineHookRouting，从命名上看是关于inline hook跳转规则的配置。FunctionInlineHookRouting的Prepare函数为空，且父类InterceptRouting的Prepare函数也为空，可以先忽略
主要看下面这个函数DispatchRouting
从BuildRouting函数流程中来看下它做的事，to对应的是replace_func，from对应的是patched_addr，也就是origin_func对应的地址，得到这两个地址之后就调用GenerateNormalTrampolineBuffer生成trampoline_buffer_
可以看到生成了三行指令adrp, add, br，对应了上文调试中origin_func的前三行代码替换后的代码，借助assembler-arm64.h生成buffer，对应到调试指令中
第一行x17表示当前内存页的地址，0表示origin_func与replace_func地址之间的内存页差值
第二行表示replace_func在当前内存页的偏移量
第三行就是跳转指令
最后会生成这三行跳转指令对应的字节码
BuildRouting生成完Trampoline指令后调用GenerateRelocatedCode
到这里为止，对于指令的重定向都设置完了，接下来调用了Commit函数
DobbyCodePatch是直接对于指令产生修改的函数，原理也很简单，因为内存页通常的权限都是可读权限，无法修改代码。因此需要在修改时通过mprotect修改内存页权限变成可读可写可执行，修改后再将原始权限写回完成对于代码的修改
#include <jni.h>#include <string>#include "Dobby/include/dobby.h"#include "logging.h"extern "C" JNIEXPORT jstring JNICALL
Java_com_example_dobbytest1_MainActivity_stringFromJNI( JNIEnv* env,
jobject /* this */) {
std::string hello = "no be hooked";
return env->NewStringUTF(hello.c_str());
}static jstring (*orgin_Java_com_example_dobbytest1_MainActivity_stringFromJNI)(JNIEnv* env,jobject /* this */);
extern "C" JNIEXPORT jstring JNICALL
new_Java_com_example_dobbytest1_MainActivity_stringFromJNI( JNIEnv* env,
jobject jobject1/* this */) {
LOGI("be hooked");
return orgin_Java_com_example_dobbytest1_MainActivity_stringFromJNI(env,jobject1);
}__attribute__((constructor)) static void ctor() {
// 构造函数 静态插入hook调用
// 原函数名
// 新函数地址
// 旧函数地址
DobbyHook((void *) DobbySymbolResolver(NULL, "Java_com_example_dobbytest1_MainActivity_stringFromJNI"),
(void *) new_Java_com_example_dobbytest1_MainActivity_stringFromJNI,
(void **) &orgin_Java_com_example_dobbytest1_MainActivity_stringFromJNI
);
}#include <jni.h>#include <string>#include "Dobby/include/dobby.h"#include "logging.h"extern "C" JNIEXPORT jstring JNICALL
Java_com_example_dobbytest1_MainActivity_stringFromJNI( JNIEnv* env,
jobject /* this */) {
std::string hello = "no be hooked";
return env->NewStringUTF(hello.c_str());
}static jstring (*orgin_Java_com_example_dobbytest1_MainActivity_stringFromJNI)(JNIEnv* env,jobject /* this */);
extern "C" JNIEXPORT jstring JNICALL
new_Java_com_example_dobbytest1_MainActivity_stringFromJNI( JNIEnv* env,
jobject jobject1/* this */) {
LOGI("be hooked");
return orgin_Java_com_example_dobbytest1_MainActivity_stringFromJNI(env,jobject1);
}__attribute__((constructor)) static void ctor() {
// 构造函数 静态插入hook调用
// 原函数名
// 新函数地址
// 旧函数地址
DobbyHook((void *) DobbySymbolResolver(NULL, "Java_com_example_dobbytest1_MainActivity_stringFromJNI"),
(void *) new_Java_com_example_dobbytest1_MainActivity_stringFromJNI,
(void **) &orgin_Java_com_example_dobbytest1_MainActivity_stringFromJNI
);
}./lldb-server platform --listen '*:1234' --server
./lldb-server platform --listen '*:1234' --server
选择调试平台(lldb) platform select remote-android
Platform: remote-android
Connected: no
连接lldb-server创建的端口(lldb) platform connect connect://:1234
Platform: remote-android
Triple: aarch64-unknown-linux-android
OS Version: 30 (4.14.186-perf-g42f990859d35) Hostname: localhost
Connected: yes
WorkingDir: /data/local/tmp
Kernel: #1 SMP PREEMPT Tue Mar 1 19:09:49 CST 2022
(lldb)选择调试平台(lldb) platform select remote-android
Platform: remote-android
Connected: no
连接lldb-server创建的端口(lldb) platform connect connect://:1234
Platform: remote-android
Triple: aarch64-unknown-linux-android
OS Version: 30 (4.14.186-perf-g42f990859d35) Hostname: localhost
Connected: yes
WorkingDir: /data/local/tmp
Kernel: #1 SMP PREEMPT Tue Mar 1 19:09:49 CST 2022
(lldb)(lldb) br set -a 0x70ece54110
Breakpoint 1: address = 0x00000070ece54110(lldb) br set -a 0x70ece54110
Breakpoint 1: address = 0x00000070ece54110断点信息Process 20161 stopped* thread #1, name = 'mple.dobbytest1', stop reason = breakpoint 1.1
frame #0: 0x00000070ece54110
-> 0x70ece54110: adrp x17, 0 0x70ece54114: add x17, x17, #0x290
0x70ece54118: br x17
0x70ece5411c: mrs x8, TPIDR_EL0
Target 0: (app_process64) stopped.对比原始汇编代码.text:000000000000B110 SUB SP, SP, #0x70
.text:000000000000B114 STP X29, X30, [SP,#0x60+var_s0]
.text:000000000000B118 ADD X29, SP, #0x60
.text:000000000000B11C MRS X8, #3, c13, c0, #2
断点信息Process 20161 stopped* thread #1, name = 'mple.dobbytest1', stop reason = breakpoint 1.1
frame #0: 0x00000070ece54110
-> 0x70ece54110: adrp x17, 0 0x70ece54114: add x17, x17, #0x290
0x70ece54118: br x17
0x70ece5411c: mrs x8, TPIDR_EL0
Target 0: (app_process64) stopped.对比原始汇编代码.text:000000000000B110 SUB SP, SP, #0x70
.text:000000000000B114 STP X29, X30, [SP,#0x60+var_s0]
.text:000000000000B118 ADD X29, SP, #0x60
.text:000000000000B11C MRS X8, #3, c13, c0, #2
Process 20161 stopped* thread #1, name = 'mple.dobbytest1', stop reason = instruction step over
frame #0: 0x00000070ece54114
-> 0x70ece54114: add x17, x17, #0x290
0x70ece54118: br x17
0x70ece5411c: mrs x8, TPIDR_EL0
0x70ece54120: ldr x8, [x8, #0x28]
Target 0: (app_process64) stopped.(lldb) register read x17
x17 = 0x00000070ece54000
(lldb) nProcess 20161 stopped* thread #1, name = 'mple.dobbytest1', stop reason = instruction step over
frame #0: 0x00000070ece54118
-> 0x70ece54118: br x17 0x70ece5411c: mrs x8, TPIDR_EL0
0x70ece54120: ldr x8, [x8, #0x28]
0x70ece54124: stur x8, [x29, #-0x8]
Target 0: (app_process64) stopped.(lldb) register read x17
x17 = 0x00000070ece54290
(lldb)Process 20161 stopped* thread #1, name = 'mple.dobbytest1', stop reason = instruction step over
frame #0: 0x00000070ece54114
-> 0x70ece54114: add x17, x17, #0x290
0x70ece54118: br x17
0x70ece5411c: mrs x8, TPIDR_EL0
0x70ece54120: ldr x8, [x8, #0x28]
Target 0: (app_process64) stopped.(lldb) register read x17
x17 = 0x00000070ece54000
(lldb) nProcess 20161 stopped* thread #1, name = 'mple.dobbytest1', stop reason = instruction step over
frame #0: 0x00000070ece54118
-> 0x70ece54118: br x17 0x70ece5411c: mrs x8, TPIDR_EL0
0x70ece54120: ldr x8, [x8, #0x28]
0x70ece54124: stur x8, [x29, #-0x8]
Target 0: (app_process64) stopped.(lldb) register read x17
x17 = 0x00000070ece54290
(lldb)(lldb) br set -a 0x70ece542cc
Breakpoint 3: address = 0x00000070ece542cc(lldb) cProcess 20161 resumingProcess 20161 stopped* thread #1, name = 'mple.dobbytest1', stop reason = breakpoint 3.1
frame #0: 0x00000070ece542cc
-> 0x70ece542cc: blr x8 0x70ece542d0: ldp x29, x30, [sp, #0x10]
0x70ece542d4: add sp, sp, #0x20
0x70ece542d8: ret
Target 0: (app_process64) stopped.(lldb) sProcess 20161 stopped* thread #1, name = 'mple.dobbytest1', stop reason = instruction step into
frame #0: 0x0000007183933000
-> 0x7183933000: sub sp, sp, #0x70
0x7183933004: stp x29, x30, [sp, #0x60]
0x7183933008: add x29, sp, #0x60
0x718393300c: ldr x17, #0x8
Target 0: (app_process64) stopped.(lldb) sProcess 20161 stopped* thread #1, name = 'mple.dobbytest1', stop reason = instruction step into
frame #0: 0x0000007183933004
-> 0x7183933004: stp x29, x30, [sp, #0x60]
0x7183933008: add x29, sp, #0x60
0x718393300c: ldr x17, #0x8
0x7183933010: br x17
Target 0: (app_process64) stopped.(lldb) br set -a 0x70ece542cc
Breakpoint 3: address = 0x00000070ece542cc(lldb) cProcess 20161 resumingProcess 20161 stopped* thread #1, name = 'mple.dobbytest1', stop reason = breakpoint 3.1
frame #0: 0x00000070ece542cc
-> 0x70ece542cc: blr x8 0x70ece542d0: ldp x29, x30, [sp, #0x10]
0x70ece542d4: add sp, sp, #0x20
0x70ece542d8: ret
Target 0: (app_process64) stopped.(lldb) sProcess 20161 stopped* thread #1, name = 'mple.dobbytest1', stop reason = instruction step into
frame #0: 0x0000007183933000
-> 0x7183933000: sub sp, sp, #0x70
0x7183933004: stp x29, x30, [sp, #0x60]
0x7183933008: add x29, sp, #0x60
0x718393300c: ldr x17, #0x8
Target 0: (app_process64) stopped.(lldb) sProcess 20161 stopped* thread #1, name = 'mple.dobbytest1', stop reason = instruction step into
frame #0: 0x0000007183933004
-> 0x7183933004: stp x29, x30, [sp, #0x60]
0x7183933008: add x29, sp, #0x60
0x718393300c: ldr x17, #0x8
0x7183933010: br x17
Target 0: (app_process64) stopped.(lldb) sProcess 20161 stopped* thread #1, name = 'mple.dobbytest1', stop reason = instruction step into
frame #0: 0x000000718393300c
-> 0x718393300c: ldr x17, #0x8
0x7183933010: br x17
0x7183933014: .long 0xece5411c ; unknown opcode
0x7183933018: udf #0x70
Target 0: (app_process64) stopped.(lldb) register read x17
x17 = 0x0000007185f8e970 libc.so`pthread_mutex_unlock
(lldb) sProcess 20161 stopped* thread #1, name = 'mple.dobbytest1', stop reason = instruction step into
frame #0: 0x0000007183933010
-> 0x7183933010: br x17 0x7183933014: .long 0xece5411c ; unknown opcode
0x7183933018: udf #0x70
0x718393301c: udf #0x0
Target 0: (app_process64) stopped.(lldb) register read x17
x17 = 0x00000070ece5411c
(lldb) sProcess 20161 stopped* thread #1, name = 'mple.dobbytest1', stop reason = instruction step into
frame #0: 0x00000070ece5411c
-> 0x70ece5411c: mrs x8, TPIDR_EL0 0x70ece54120: ldr x8, [x8, #0x28]
0x70ece54124: stur x8, [x29, #-0x8]
0x70ece54128: stur x0, [x29, #-0x28]
Target 0: (app_process64) stopped.(lldb) sProcess 20161 stopped* thread #1, name = 'mple.dobbytest1', stop reason = instruction step into
frame #0: 0x000000718393300c
-> 0x718393300c: ldr x17, #0x8
0x7183933010: br x17
0x7183933014: .long 0xece5411c ; unknown opcode
0x7183933018: udf #0x70
Target 0: (app_process64) stopped.(lldb) register read x17
x17 = 0x0000007185f8e970 libc.so`pthread_mutex_unlock
(lldb) sProcess 20161 stopped* thread #1, name = 'mple.dobbytest1', stop reason = instruction step into
frame #0: 0x0000007183933010
-> 0x7183933010: br x17 0x7183933014: .long 0xece5411c ; unknown opcode
0x7183933018: udf #0x70
0x718393301c: udf #0x0
Target 0: (app_process64) stopped.(lldb) register read x17
x17 = 0x00000070ece5411c
(lldb) sProcess 20161 stopped* thread #1, name = 'mple.dobbytest1', stop reason = instruction step into
frame #0: 0x00000070ece5411c
-> 0x70ece5411c: mrs x8, TPIDR_EL0 0x70ece54120: ldr x8, [x8, #0x28]
0x70ece54124: stur x8, [x29, #-0x8]
0x70ece54128: stur x0, [x29, #-0x28]
Target 0: (app_process64) stopped.Process 20161 stopped* thread #1, name = 'mple.dobbytest1', stop reason = breakpoint 4.1
frame #0: 0x00000070ece54188
-> 0x70ece54188: ldr x0, [sp, #0x18]
0x70ece5418c: ldp x29, x30, [sp, #0x60]
0x70ece54190: add sp, sp, #0x70
0x70ece54194: ret
Target 0: (app_process64) stopped.Process 20161 stopped* thread #1, name = 'mple.dobbytest1', stop reason = breakpoint 4.1
frame #0: 0x00000070ece54188
-> 0x70ece54188: ldr x0, [sp, #0x18]
0x70ece5418c: ldp x29, x30, [sp, #0x60]
0x70ece54190: add sp, sp, #0x70
0x70ece54194: ret
Target 0: (app_process64) stopped.Process 20161 stopped* thread #1, name = 'mple.dobbytest1', stop reason = instruction step into
frame #0: 0x00000070ece54194
-> 0x70ece54194: ret 0x70ece54198: str x0, [sp, #0x28]
0x70ece5419c: mov w8, w1
0x70ece541a0: str w8, [sp, #0x24]
Target 0: (app_process64) stopped.(lldb) sProcess 20161 stopped* thread #1, name = 'mple.dobbytest1', stop reason = instruction step into
frame #0: 0x00000070ece542d0
-> 0x70ece542d0: ldp x29, x30, [sp, #0x10]
0x70ece542d4: add sp, sp, #0x20
0x70ece542d8: ret
0x70ece542dc: stp x29, x30, [sp, #-0x10]!
Target 0: (app_process64) stopped.Process 20161 stopped* thread #1, name = 'mple.dobbytest1', stop reason = instruction step into
frame #0: 0x00000070ece54194
-> 0x70ece54194: ret 0x70ece54198: str x0, [sp, #0x28]
0x70ece5419c: mov w8, w1
0x70ece541a0: str w8, [sp, #0x24]
Target 0: (app_process64) stopped.(lldb) sProcess 20161 stopped* thread #1, name = 'mple.dobbytest1', stop reason = instruction step into
frame #0: 0x00000070ece542d0
-> 0x70ece542d0: ldp x29, x30, [sp, #0x10]
0x70ece542d4: add sp, sp, #0x20
0x70ece542d8: ret
0x70ece542dc: stp x29, x30, [sp, #-0x10]!
Target 0: (app_process64) stopped.// source/InterceptRouting/Routing/FunctionInlineHook/FunctionInlineHook.ccPUBLIC int DobbyHook(void *address, dobby_dummy_func_t replace_func, dobby_dummy_func_t *origin_func) {
......#if defined(ANDROID) void *page_align_address = (void *)ALIGN_FLOOR(address, OSMemory::PageSize());
if (!OSMemory::SetPermission(page_align_address, OSMemory::PageSize(), kReadExecute)) {
return -1;
}
#endif DEBUG_LOG("----- [DobbyHook:%p] -----", address);
// check if already register
auto entry = Interceptor::SharedInstance()->find((addr_t)address);
if (entry) {
ERROR_LOG("%p already been hooked.", address);
return -1;
}
entry = new InterceptEntry(kFunctionInlineHook, (addr_t)address);
auto *routing = new FunctionInlineHookRouting(entry, replace_func);
routing->Prepare();
routing->DispatchRouting();
// set origin func entry with as relocated instructions
if (origin_func) {
*origin_func = (dobby_dummy_func_t)entry->relocated_addr;
#if defined(__APPLE__) && defined(__arm64__) *origin_func = pac_sign(*origin_func);
#endif }
routing->Commit();
Interceptor::SharedInstance()->add(entry);
return 0;
}// source/InterceptRouting/Routing/FunctionInlineHook/FunctionInlineHook.ccPUBLIC int DobbyHook(void *address, dobby_dummy_func_t replace_func, dobby_dummy_func_t *origin_func) {
......#if defined(ANDROID) void *page_align_address = (void *)ALIGN_FLOOR(address, OSMemory::PageSize());
if (!OSMemory::SetPermission(page_align_address, OSMemory::PageSize(), kReadExecute)) {
return -1;
}
#endif DEBUG_LOG("----- [DobbyHook:%p] -----", address);
// check if already register
auto entry = Interceptor::SharedInstance()->find((addr_t)address);
if (entry) {
ERROR_LOG("%p already been hooked.", address);
return -1;
}
entry = new InterceptEntry(kFunctionInlineHook, (addr_t)address);
auto *routing = new FunctionInlineHookRouting(entry, replace_func);
routing->Prepare();
routing->DispatchRouting();
// set origin func entry with as relocated instructions
if (origin_func) {
*origin_func = (dobby_dummy_func_t)entry->relocated_addr;
#if defined(__APPLE__) && defined(__arm64__) *origin_func = pac_sign(*origin_func);
#endif }
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最后于 2024-2-25 23:06
被tcc0lin编辑
，原因：
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