安卓编译: 2.native层定制修改(下)

2.4 添加open有关函数进行参数打印

目的

打印文件open相关函数 ，用于方便定位调试

修改步骤

路径 <aosp>\bionic\libc\bionic\open.cpp 增加以下代码

#include <fcntl.h>
#include <stdarg.h>
#include <stdlib.h>
#include <unistd.h> // 新增
 
#include "private/bionic_fdtrack.h"
#include "private/bionic_fortify.h"
#include <android/log.h> // 新增
#include <string.h> // 新增
 
 
int open(const char* pathname, int flags, ...) {
  mode_t mode = 0;
 
  if (needs_mode(flags)) {
    va_list args;
    va_start(args, flags);
    mode = static_cast<mode_t>(va_arg(args, int));
    va_end(args);
  }
 
   // 新增
  int uid = getuid();
  int pid = getpid();
  if (uid > 10000)
  {
    char buffer[256];
    snprintf(buffer, sizeof(buffer), "file=%s uid=%d pid=%d", pathname, uid, pid);
 
    clogi("open",buffer);
  }
  if (uid > 10000 && contains_keyword(pathname)) {
    clogi("open-replace", pathname);
    return FDTRACK_CREATE(__openat(AT_FDCWD, "/bin/non_exist", force_O_LARGEFILE(flags), mode));
  }
 
  return FDTRACK_CREATE(__openat(AT_FDCWD, pathname, force_O_LARGEFILE(flags), mode));
}
 
 
int openat(int fd, const char *pathname, int flags, ...) {
  mode_t mode = 0;
 
  if (needs_mode(flags)) {
    va_list args;
    va_start(args, flags);
    mode = static_cast<mode_t>(va_arg(args, int));
    va_end(args);
  }
  // 新增
  int uid = getuid();
  int pid = getpid();
  if (uid > 10000)
  {
    char buffer[256];
    snprintf(buffer, sizeof(buffer), "file=%s uid=%d pid=%d", pathname, uid, pid);
    clogi("openat",buffer);
  }
  if (uid > 10000 && contains_keyword(pathname)) {
    clogi("openat-replace", pathname);
    return FDTRACK_CREATE_NAME("openat", __openat(fd, "/bin/non_exist", force_O_LARGEFILE(flags), mode));
  }
 
  return FDTRACK_CREATE_NAME("openat", __openat(fd, pathname, force_O_LARGEFILE(flags), mode));
}

实现效果

2.5 定制su名字隐藏root

目的

需要修改的文件有如下几个

<aosp>\system\extras\su
<aosp>\system\extras\su\Android.mk
<aosp>\system\core\libcutils\fs_cofnig.cpp
<aosp>\system\sepolicy\private\file_contexts
<aosp>\system\sepolicy\prebuilts\api\30.0\private\file_contexts
<aosp>\system\sepolicy\prebuilts\api\29.0\private\file_contexts
<aosp>\system\sepolicy\prebuilts\api\28.0\private\file_contexts
<aosp>\system\sepolicy\prebuilts\api\27.0\private\file_contexts
<aosp>\system\sepolicy\prebuilts\api\26.0\private\file_contexts
<aosp>\build\make\target\product\base_system.mk
su文件夹

自定义su文件名字，规避root检查。

环境：Pixel 3
目标：修改su为xu，命名可以是其他。

修改方式

mv \system\extras\su -> \system\extras\xu
替换字符串 \system\extras\xu[Android.mk](android.mk/) `LOCAL_MO… := su->LOCAL_MODULE := xu 替换字符串 <aosp>\system\core\libcutils\fs_cofnig.cppsystem/xbin/su->system/xbin/xu`

file_contexts

<aosp>\system\sepolicy\private\file_contexts
<aosp>\system\sepolicy\prebuilts\api\30.0\private\file_contexts
<aosp>\system\sepolicy\prebuilts\api\29.0\private\file_contexts
<aosp>\system\sepolicy\prebuilts\api\28.0\private\file_contexts
<aosp>\system\sepolicy\prebuilts\api\27.0\private\file_contexts
<aosp>\system\sepolicy\prebuilts\api\26.0\private\file_contexts

统一将 system/xbin/su -> system/xbin/xu

替换字符串 \build\make\target\product[base_system.mk](http://base_system.mk/) su -> xu