Android中的so注入(inject)和挂钩(hook)

本文主要是介绍Android中的so注入(inject)和挂钩(hook) - For both x86 and arm，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

对于Android for arm上的so注入（inject）和挂钩（hook），网上已有牛人给出了代码-libinject（http://bbs.pediy.com/showthread.php?t=141355）。由于实现中的ptrace函数是依赖于平台的，所以不经改动只能用于arm平台。本文将之扩展了一下，使它能够通用于Android的x86和arm平台。Arm平台部分基本重用了libinject中的代码，其中因为汇编不好移植且容易出错，所以把shellcode.s用ptrace_call替换掉了，另外保留了mmap，用来传字符串参数，当然也可以通过栈来传，但栈里和其它东西混一起，一弄不好就会隔儿了，所以还是保险点好。最后注意设备要root。

首先创建目录及文件：

jni
inject.c
Android.mk
Application.mk

inject.c:

#include <stdio.h>  
#include <stdlib.h>  
#include <asm/user.h>  
#include <asm/ptrace.h>  
#include <sys/ptrace.h>  
#include <sys/wait.h>  
#include <sys/mman.h>  
#include <dlfcn.h>  
#include <dirent.h>  
#include <unistd.h>  
#include <string.h>  
#include <elf.h>  
#include <android/log.h>  #if defined(__i386__)  
#define pt_regs         user_regs_struct  
#endif  #define ENABLE_DEBUG 1  #if ENABLE_DEBUG  
#define  LOG_TAG "INJECT"  
#define  LOGD(fmt, args...)  __android_log_print(ANDROID_LOG_DEBUG,LOG_TAG, fmt, ##args)  
#define DEBUG_PRINT(format,args...) \  LOGD(format, ##args)  
#else  
#define DEBUG_PRINT(format,args...)  
#endif  #define CPSR_T_MASK     ( 1u << 5 )  const char *libc_path = "/system/lib/libc.so";  
const char *linker_path = "/system/bin/linker";  int ptrace_readdata(pid_t pid,  uint8_t *src, uint8_t *buf, size_t size)  
{  uint32_t i, j, remain;  uint8_t *laddr;  union u {  long val;  char chars[sizeof(long)];  } d;  j = size / 4;  remain = size % 4;  laddr = buf;  for (i = 0; i < j; i ++) {  d.val = ptrace(PTRACE_PEEKTEXT, pid, src, 0);  memcpy(laddr, d.chars, 4);  src += 4;  laddr += 4;  }  if (remain > 0) {  d.val = ptrace(PTRACE_PEEKTEXT, pid, src, 0);  memcpy(laddr, d.chars, remain);  }  return 0;  
}  int ptrace_writedata(pid_t pid, uint8_t *dest, uint8_t *data, size_t size)  
{  uint32_t i, j, remain;  uint8_t *laddr;  union u {  long val;  char chars[sizeof(long)];  } d;  j = size / 4;  remain = size % 4;  laddr = data;  for (i = 0; i < j; i ++) {  memcpy(d.chars, laddr, 4);  ptrace(PTRACE_POKETEXT, pid, dest, d.val);  dest  += 4;  laddr += 4;  }  if (remain > 0) {  d.val = ptrace(PTRACE_PEEKTEXT, pid, dest, 0);  for (i = 0; i < remain; i ++) {  d.chars[i] = *laddr ++;  }  ptrace(PTRACE_POKETEXT, pid, dest, d.val);  }  return 0;  
}  #if defined(__arm__)  
int ptrace_call(pid_t pid, uint32_t addr, long *params, uint32_t num_params, struct pt_regs* regs)  
{  uint32_t i;  for (i = 0; i < num_params && i < 4; i ++) {  regs->uregs[i] = params[i];  }  //  // push remained params onto stack  //  if (i < num_params) {  regs->ARM_sp -= (num_params - i) * sizeof(long) ;  ptrace_writedata(pid, (void *)regs->ARM_sp, (uint8_t *)&params[i], (num_params - i) * sizeof(long));  }  regs->ARM_pc = addr;  if (regs->ARM_pc & 1) {  /* thumb */  regs->ARM_pc &= (~1u);  regs->ARM_cpsr |= CPSR_T_MASK;  } else {  /* arm */  regs->ARM_cpsr &= ~CPSR_T_MASK;  }  regs->ARM_lr = 0;      if (ptrace_setregs(pid, regs) == -1   || ptrace_continue(pid) == -1) {  printf("error\n");  return -1;  }  int stat = 0;waitpid(pid, &stat, WUNTRACED);while (stat != 0xb7f) {if (ptrace_continue(pid) == -1) {printf("error\n");return -1;}waitpid(pid, &stat, WUNTRACED);}return 0;  
}  #elif defined(__i386__)  
long ptrace_call(pid_t pid, uint32_t addr, long *params, uint32_t num_params, struct user_regs_struct * regs)  
{  regs->esp -= (num_params) * sizeof(long) ;  ptrace_writedata(pid, (void *)regs->esp, (uint8_t *)params, (num_params) * sizeof(long));  long tmp_addr = 0x00;  regs->esp -= sizeof(long);  ptrace_writedata(pid, regs->esp, (char *)&tmp_addr, sizeof(tmp_addr));   regs->eip = addr;  if (ptrace_setregs(pid, regs) == -1   || ptrace_continue( pid) == -1) {  printf("error\n");  return -1;  }  int stat = 0;waitpid(pid, &stat, WUNTRACED);while (stat != 0xb7f) {if (ptrace_continue(pid) == -1) {printf("error\n");return -1;}waitpid(pid, &stat, WUNTRACED);}return 0;  
}  
#else   
#error "Not supported"  
#endif  int ptrace_getregs(pid_t pid, struct pt_regs * regs)  
{  if (ptrace(PTRACE_GETREGS, pid, NULL, regs) < 0) {  perror("ptrace_getregs: Can not get register values");  return -1;  }  return 0;  
}  int ptrace_setregs(pid_t pid, struct pt_regs * regs)  
{  if (ptrace(PTRACE_SETREGS, pid, NULL, regs) < 0) {  perror("ptrace_setregs: Can not set register values");  return -1;  }  return 0;  
}  int ptrace_continue(pid_t pid)  
{  if (ptrace(PTRACE_CONT, pid, NULL, 0) < 0) {  perror("ptrace_cont");  return -1;  }  return 0;  
}  int ptrace_attach(pid_t pid)  
{  if (ptrace(PTRACE_ATTACH, pid, NULL, 0) < 0) {  perror("ptrace_attach");  return -1;  }  int status = 0;  waitpid(pid, &status , WUNTRACED);  return 0;  
}  int ptrace_detach(pid_t pid)  
{  if (ptrace(PTRACE_DETACH, pid, NULL, 0) < 0) {  perror("ptrace_detach");  return -1;  }  return 0;  
}  void* get_module_base(pid_t pid, const char* module_name)  
{  FILE *fp;  long addr = 0;  char *pch;  char filename[32];  char line[1024];  if (pid < 0) {  /* self process */  snprintf(filename, sizeof(filename), "/proc/self/maps", pid);  } else {  snprintf(filename, sizeof(filename), "/proc/%d/maps", pid);  }  fp = fopen(filename, "r");  if (fp != NULL) {  while (fgets(line, sizeof(line), fp)) {  if (strstr(line, module_name)) {  pch = strtok( line, "-" );  addr = strtoul( pch, NULL, 16 );  if (addr == 0x8000)  addr = 0;  break;  }  }  fclose(fp) ;  }  return (void *)addr;  
}  void* get_remote_addr(pid_t target_pid, const char* module_name, void* local_addr)  
{  void* local_handle, *remote_handle;  local_handle = get_module_base(-1, module_name);  remote_handle = get_module_base(target_pid, module_name);  DEBUG_PRINT("[+] get_remote_addr: local[%x], remote[%x]\n", local_handle, remote_handle);  void * ret_addr = (void *)((uint32_t)local_addr + (uint32_t)remote_handle - (uint32_t)local_handle);  #if defined(__i386__)  if (!strcmp(module_name, libc_path)) {  ret_addr += 2;  }  
#endif  return ret_addr;  
}  int find_pid_of(const char *process_name)  
{  int id;  pid_t pid = -1;  DIR* dir;  FILE *fp;  char filename[32];  char cmdline[256];  struct dirent * entry;  if (process_name == NULL)  return -1;  dir = opendir("/proc");  if (dir == NULL)  return -1;  while((entry = readdir(dir)) != NULL) {  id = atoi(entry->d_name);  if (id != 0) {  sprintf(filename, "/proc/%d/cmdline", id);  fp = fopen(filename, "r");  if (fp) {  fgets(cmdline, sizeof(cmdline), fp);  fclose(fp);  if (strcmp(process_name, cmdline) == 0) {  /* process found */  pid = id;  break;  }  }  }  }  closedir(dir);  return pid;  
}  long ptrace_retval(struct pt_regs * regs)  
{  
#if defined(__arm__)  return regs->ARM_r0;  
#elif defined(__i386__)  return regs->eax;  
#else  
#error "Not supported"  
#endif  
}  long ptrace_ip(struct pt_regs * regs)  
{  
#if defined(__arm__)  return regs->ARM_pc;  
#elif defined(__i386__)  return regs->eip;  
#else  
#error "Not supported"  
#endif  
}  int ptrace_call_wrapper(pid_t target_pid, const char * func_name, void * func_addr, long * parameters, int param_num, struct pt_regs * regs)   
{  DEBUG_PRINT("[+] Calling %s in target process.\n", func_name);  if (ptrace_call(target_pid, (uint32_t)func_addr, parameters, param_num, regs) == -1)  return -1;  if (ptrace_getregs(target_pid, regs) == -1)  return -1;  DEBUG_PRINT("[+] Target process returned from %s, return value=%x, pc=%x \n",   func_name, ptrace_retval(regs), ptrace_ip(regs));  return 0;  
}  int inject_remote_process(pid_t target_pid, const char *library_path, const char *function_name, const char *param, size_t param_size)  
{  int ret = -1;  void *mmap_addr, *dlopen_addr, *dlsym_addr, *dlclose_addr, *dlerror_addr;  void *local_handle, *remote_handle, *dlhandle;  uint8_t *map_base = 0;  uint8_t *dlopen_param1_ptr, *dlsym_param2_ptr, *saved_r0_pc_ptr, *inject_param_ptr, *remote_code_ptr, *local_code_ptr;  struct pt_regs regs, original_regs;  extern uint32_t _dlopen_addr_s, _dlopen_param1_s, _dlopen_param2_s, _dlsym_addr_s, \  _dlsym_param2_s, _dlclose_addr_s, _inject_start_s, _inject_end_s, _inject_function_param_s, \  _saved_cpsr_s, _saved_r0_pc_s;  uint32_t code_length;  long parameters[10];  DEBUG_PRINT("[+] Injecting process: %d\n", target_pid);  if (ptrace_attach(target_pid) == -1)  goto exit;  if (ptrace_getregs(target_pid, &regs) == -1)  goto exit;  /* save original registers */  memcpy(&original_regs, &regs, sizeof(regs));  mmap_addr = get_remote_addr(target_pid, libc_path, (void *)mmap);  DEBUG_PRINT("[+] Remote mmap address: %x\n", mmap_addr);  /* call mmap */  parameters[0] = 0;  // addr  parameters[1] = 0x4000; // size  parameters[2] = PROT_READ | PROT_WRITE | PROT_EXEC;  // prot  parameters[3] =  MAP_ANONYMOUS | MAP_PRIVATE; // flags  parameters[4] = 0; //fd  parameters[5] = 0; //offset  if (ptrace_call_wrapper(target_pid, "mmap", mmap_addr, parameters, 6, &regs) == -1)  goto exit;  map_base = ptrace_retval(&regs);  dlopen_addr = get_remote_addr( target_pid, linker_path, (void *)dlopen );  dlsym_addr = get_remote_addr( target_pid, linker_path, (void *)dlsym );  dlclose_addr = get_remote_addr( target_pid, linker_path, (void *)dlclose );  dlerror_addr = get_remote_addr( target_pid, linker_path, (void *)dlerror );  DEBUG_PRINT("[+] Get imports: dlopen: %x, dlsym: %x, dlclose: %x, dlerror: %x\n",  dlopen_addr, dlsym_addr, dlclose_addr, dlerror_addr);  printf("library path = %s\n", library_path);  ptrace_writedata(target_pid, map_base, library_path, strlen(library_path) + 1);  parameters[0] = map_base;     parameters[1] = RTLD_NOW| RTLD_GLOBAL;   if (ptrace_call_wrapper(target_pid, "dlopen", dlopen_addr, parameters, 2, &regs) == -1)  goto exit;  void * sohandle = ptrace_retval(&regs);  #define FUNCTION_NAME_ADDR_OFFSET       0x100  ptrace_writedata(target_pid, map_base + FUNCTION_NAME_ADDR_OFFSET, function_name, strlen(function_name) + 1);  parameters[0] = sohandle;     parameters[1] = map_base + FUNCTION_NAME_ADDR_OFFSET;   if (ptrace_call_wrapper(target_pid, "dlsym", dlsym_addr, parameters, 2, &regs) == -1)  goto exit;  void * hook_entry_addr = ptrace_retval(&regs);  DEBUG_PRINT("hook_entry_addr = %p\n", hook_entry_addr);  #define FUNCTION_PARAM_ADDR_OFFSET      0x200  ptrace_writedata(target_pid, map_base + FUNCTION_PARAM_ADDR_OFFSET, param, strlen(param) + 1);  parameters[0] = map_base + FUNCTION_PARAM_ADDR_OFFSET;    if (ptrace_call_wrapper(target_pid, "hook_entry", hook_entry_addr, parameters, 1, &regs) == -1)  goto exit;  	printf("Press enter to dlclose and detach\n");  getchar();  parameters[0] = sohandle;     if (ptrace_call_wrapper(target_pid, "dlclose", dlclose, parameters, 1, &regs) == -1)  goto exit;  /* restore */  ptrace_setregs(target_pid, &original_regs);  ptrace_detach(target_pid);  ret = 0;  exit:  return ret;  
}  int main(int argc, char** argv) {  pid_t target_pid;  target_pid = find_pid_of("/system/bin/surfaceflinger");  if (-1 == target_pid) {printf("Can't find the process\n");return -1;}//target_pid = find_pid_of("/data/test");  inject_remote_process(target_pid, "/data/libhello.so", "hook_entry",  "I'm parameter!", strlen("I'm parameter!"));  return 0;
}

注意上面的/system/bin/surfaceflinger进程我随手写的，你的设备上不一定有。没有的话挑其它的也行，前提是ps命令里能找到。

Android.mk:

    LOCAL_PATH := $(call my-dir)include $(CLEAR_VARS)LOCAL_MODULE := inject LOCAL_SRC_FILES := inject.c #shellcode.sLOCAL_LDLIBS += -L$(SYSROOT)/usr/lib -llog#LOCAL_FORCE_STATIC_EXECUTABLE := trueinclude $(BUILD_EXECUTABLE)

Application.mk:

    APP_ABI := x86 armeabi-v7a

运行nkd-build编译成生x86和arm平台下的可执行文件：

    jzj@jzj-laptop:~/workspace/inject_hook/inject_jni$ ndk-buildInstall        : inject => libs/x86/injectInstall        : inject => libs/armeabi-v7a/inject

再来生成要注入的so，创建目录及文件：

jni  hello.c  Android.mk  Application.mk

hello.c:

#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <android/log.h>
#include <elf.h>
#include <fcntl.h>#define LOG_TAG "DEBUG"
#define LOGD(fmt, args...) __android_log_print(ANDROID_LOG_DEBUG, LOG_TAG, fmt, ##args)  int hook_entry(char * a){LOGD("Hook success, pid = %d\n", getpid());LOGD("Hello %s\n", a);return 0;
}

Android.mk:

LOCAL_PATH := $(call my-dir)include $(CLEAR_VARS)LOCAL_LDLIBS += -L$(SYSROOT)/usr/lib -llog 
#LOCAL_ARM_MODE := arm
LOCAL_MODULE    := hello
LOCAL_SRC_FILES := hello.c
include $(BUILD_SHARED_LIBRARY)

Application.mk:

    APP_ABI := x86 armeabi-v7a

运行nkd-build编译成生x86和arm平台下的so：

jzj@jzj-laptop:~/workspace/inject_hook/hook_so_simple$ ndk-build 
Install        : libhello.so => libs/x86/libhello.so
Install        : libhello.so => libs/armeabi-v7a/libhello.so

然后就可以跑起来试试了，连接root过的Android设备或者打开模拟器。将inject和libhello.so拷入设备，设执行权限，执行：

先看看被注入进程（surfaceflinger）的mmap，可以看到我们的so已经被加载了，紧接着的那一块就是我们mmap出来的：

从logcat中也可以看到so注入成功，并且以被注入进程的身份执行了so中的代码：

简单的注入成功，现在我们再来做一个实验，就是应用这套机制来截获surfaceflinger中的eglSwapBuffers调用，然后用我们自己的函数来替换掉原来的eglSwapBuffers调用。关于截系统中的函数调用网上有例子http://bbs.pediy.com/showthread.php?t=157419，这里依葫芦画瓢。首先将hello.c改下：

#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <android/log.h>
#include <EGL/egl.h>
#include <GLES/gl.h>
#include <elf.h>
#include <fcntl.h>
#include <sys/mman.h>#define LOG_TAG "DEBUG"
#define LOGD(fmt, args...) __android_log_print(ANDROID_LOG_DEBUG, LOG_TAG, fmt, ##args)  EGLBoolean (*old_eglSwapBuffers)(EGLDisplay dpy, EGLSurface surf) = -1;EGLBoolean new_eglSwapBuffers(EGLDisplay dpy, EGLSurface surface)
{LOGD("New eglSwapBuffers\n");if (old_eglSwapBuffers == -1)LOGD("error\n");return old_eglSwapBuffers(dpy, surface);
}void* get_module_base(pid_t pid, const char* module_name)
{FILE *fp;long addr = 0;char *pch;char filename[32];char line[1024];if (pid < 0) {/* self process */snprintf(filename, sizeof(filename), "/proc/self/maps", pid);} else {snprintf(filename, sizeof(filename), "/proc/%d/maps", pid);}fp = fopen(filename, "r");if (fp != NULL) {while (fgets(line, sizeof(line), fp)) {if (strstr(line, module_name)) {pch = strtok( line, "-" );addr = strtoul( pch, NULL, 16 );if (addr == 0x8000)addr = 0;break;}}fclose(fp) ;}return (void *)addr;
}#define LIBSF_PATH  "/system/lib/libsurfaceflinger.so"  
int hook_eglSwapBuffers()  
{  old_eglSwapBuffers = eglSwapBuffers;  LOGD("Orig eglSwapBuffers = %p\n", old_eglSwapBuffers);  void * base_addr = get_module_base(getpid(), LIBSF_PATH);  LOGD("libsurfaceflinger.so address = %p\n", base_addr);  int fd;  fd = open(LIBSF_PATH, O_RDONLY);  if (-1 == fd) {  LOGD("error\n");  return -1;  }  Elf32_Ehdr ehdr;  read(fd, &ehdr, sizeof(Elf32_Ehdr));  unsigned long shdr_addr = ehdr.e_shoff;    int shnum = ehdr.e_shnum;    int shent_size = ehdr.e_shentsize;    unsigned long stridx = ehdr.e_shstrndx;    Elf32_Shdr shdr;  lseek(fd, shdr_addr + stridx * shent_size, SEEK_SET);    read(fd, &shdr, shent_size);    char * string_table = (char *)malloc(shdr.sh_size);    lseek(fd, shdr.sh_offset, SEEK_SET);    read(fd, string_table, shdr.sh_size);  lseek(fd, shdr_addr, SEEK_SET);    int i;    uint32_t out_addr = 0;  uint32_t out_size = 0;  uint32_t got_item = 0;int32_t got_found = 0;  for (i = 0; i < shnum; i++) {    read(fd, &shdr, shent_size);    if (shdr.sh_type == SHT_PROGBITS) {  int name_idx = shdr.sh_name;    if (strcmp(&(string_table[name_idx]), ".got.plt") == 0 || strcmp(&(string_table[name_idx]), ".got") == 0) {    out_addr = base_addr + shdr.sh_addr;    out_size = shdr.sh_size;    LOGD("out_addr = %lx, out_size = %lx\n", out_addr, out_size);  for (i = 0; i < out_size; i += 4) {    got_item = *(uint32_t *)(out_addr + i);  if (got_item  == old_eglSwapBuffers) {    LOGD("Found eglSwapBuffers in got\n");  got_found = 1;uint32_t page_size = getpagesize();uint32_t entry_page_start = (out_addr + i) & (~(page_size - 1));mprotect((uint32_t *)entry_page_start, page_size, PROT_READ | PROT_WRITE);*(uint32_t *)(out_addr + i) = new_eglSwapBuffers;  break;    } else if (got_item == new_eglSwapBuffers) {    LOGD("Already hooked\n");  break;    }    }   if (got_found) break;}   }    }    free(string_table);    close(fd);  
}  int hook_entry(char * a){LOGD("Hook success\n");LOGD("Start hooking\n");hook_eglSwapBuffers();  return 0;
}

其实这种查找方法有点简单粗暴，要是正式应用的话可以在动态符号表中查找这个符号的got地址。

接着Android.mk改为：

    LOCAL_PATH := $(call my-dir)include $(CLEAR_VARS)LOCAL_LDLIBS += -L$(SYSROOT)/usr/lib -llog -lEGL#LOCAL_ARM_MODE := armLOCAL_MODULE    := helloLOCAL_SRC_FILES := hello.cinclude $(BUILD_SHARED_LIBRARY)

Application.mk :

    APP_ABI := x86 armeabi-v7a  APP_PLATFORM := android-14

运行ndk-build编译：

    jzj@jzj-laptop:~/workspace/inject_hook/hook_so$ ndk-build Install        : libhello.so => libs/x86/libhello.soInstall        : libhello.so => libs/armeabi-v7a/libhello.so

和上面一样运行，查看logcat，我们可以看到surfaceflinger中调用eglSwapBuffers的地址已被替换成我们的版本：

    D/INJECT  ( 2231): [+] Injecting process: 1728D/INJECT  ( 2231): [+] get_remote_addr: local[b7e4f000], remote[b7e73000]D/INJECT  ( 2231): [+] Remote mmap address: b7e9fe32D/INJECT  ( 2231): [+] Calling mmap in target process.D/INJECT  ( 2231): [+] Target process returned from mmap, return value=b4f1c000, pc=0 D/INJECT  ( 2231): [+] get_remote_addr: local[b7f00000], remote[b7f7e000]D/INJECT  ( 2231): [+] get_remote_addr: local[b7f00000], remote[b7f7e000]D/INJECT  ( 2231): [+] get_remote_addr: local[b7f00000], remote[b7f7e000]D/INJECT  ( 2231): [+] get_remote_addr: local[b7f00000], remote[b7f7e000]D/INJECT  ( 2231): [+] Get imports: dlopen: b7f84f50, dlsym: b7f84fd0, dlclose: b7f84de0, dlerror: b7f84dc0D/INJECT  ( 2231): [+] Calling dlopen in target process.D/INJECT  ( 2231): [+] Target process returned from dlopen, return value=b7f995ec, pc=0 D/INJECT  ( 2231): [+] Calling dlsym in target process.D/INJECT  ( 2231): [+] Target process returned from dlsym, return value=b4f17e10, pc=0 D/INJECT  ( 2231): hook_entry_addr = 0xb4f17e10D/DEBUG   ( 1728): Hook successD/DEBUG   ( 1728): Start hookingD/DEBUG   ( 1728): Orig eglSwapBuffers = 0xb7d4a9c0D/DEBUG   ( 1728): libsurfaceflinger.so address = 0xb7f22000D/DEBUG   ( 1728): out_addr = b7f7aff4, out_size = 624D/DEBUG   ( 1728): Found eglSwapBuffers in got...D/DEBUG   ( 1728): New eglSwapBuffersD/DEBUG   ( 1728): New eglSwapBuffersD/DEBUG   ( 1728): New eglSwapBuffers...