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Android中如何自己制作su

本文原博客:http://hubingforever.blog.163.com/blog/static/171040579201372915716149/

在Android源码的system\extras(比如Android4.0\system\extras)下新建一个目录,比如su_robin目录

在su_robin目录下包含以三个文件:
su.h文件

#ifndef SU_h 
#define SU_h 1
#ifdef LOG_TAG
#undef LOG_TAG
#endif
#define LOG_TAG "robin"
#define REQUESTOR "com.noshufou.android.su"
#define REQUESTOR_DATA_PATH "/data/data/" REQUESTOR
#define REQUESTOR_CACHE_PATH "/dev/" REQUESTOR
#define REQUESTOR_DATABASES_PATH REQUESTOR_DATA_PATH "/databases"
#define REQUESTOR_DATABASE_PATH REQUESTOR_DATABASES_PATH "/permissions.sqlite"
/* intent actions */
#define ACTION_REQUEST REQUESTOR ".REQUEST"
#define ACTION_RESULT  REQUESTOR ".RESULT"
#define DEFAULT_SHELL "/system/bin/sh"
#ifdef SU_LEGACY_BUILD
#define VERSION_EXTRA "l"
#else
#define VERSION_EXTRA ""
#endif
#define VERSION "3.1.1" VERSION_EXTRA
#define VERSION_CODE 17
#define DATABASE_VERSION 6
#define PROTO_VERSION 0
struct su_initiator {
    pid_t pid;
    unsigned uid;
    char bin[PATH_MAX];
    char args[4096];
};
struct su_request {
    unsigned uid;
    int login;
    int keepenv;
    char *shell;
    char *command;
    char **argv;
    int argc;
    int optind;
};
struct su_context {
    struct su_initiator from;
    struct su_request to;
    mode_t umask;
};
enum {
    DB_INTERACTIVE,
    DB_DENY,
    DB_ALLOW
};
#endif

注意,这里的很多东西是多余。
su.c文件

#include <sys/types.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <sys/wait.h>
#include <sys/select.h>
#include <sys/time.h>
#include <unistd.h>
#include <limits.h>
#include <fcntl.h>
#include <errno.h>
#include <endian.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <getopt.h>
#include <stdint.h>
#include <pwd.h>
#include <private/android_filesystem_config.h>
#include <cutils/properties.h>
#include <cutils/log.h>
#include "su.h"
int main(int argc, char *argv[])
{
LOGI("hello !robin-su begin %d !",getuid());
printf("hello !robin-su begin");
int uid=0;
int gid=0;
if(setgid(gid) || setuid(uid)) {
LOGI("robin su: permission denied\n");
fprintf(stderr,"su: permission denied\n");
return 1;
}
  char command[1024];
LOGI("hello !robin-su end %d !",getuid());
printf("hello !robin-su end");
/* Default exec shell. */
   execlp("/system/bin/sh", "sh", NULL);
   fprintf(stderr, "su: exec failed\n");
return 1;
}

Android.mk文件

LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE := sur
LOCAL_SRC_FILES := su.c
LOCAL_STATIC_LIBRARIES := \
    liblog \
    libc \
LOCAL_MODULE_PATH := $(TARGET_OUT_OPTIONAL_EXECUTABLES)
LOCAL_MODULE_TAGS := eng debug
LOCAL_FORCE_STATIC_EXECUTABLE := true
include $(BUILD_EXECUTABLE)

编译Android源码,生成rom
如果你还不知道如何编译Android源码,请参照
http://source.android.com/source/building-running.html
在out\target\product\generic\system\xbin目录下找到生成的可执行文件sur,就是我们自己制作的su文件
通过adb push命令将其推送到手机上的system\xbin目录,
通过执行系统原来自己带的su切换到root用户,对手机上sur文件执行chmod 6777 sur命令。 
使文件属性变为rwsrwsrwx,如下所示
rwsrwsrwx root     root        58960 2013-08-29 11:31 sur
然后你可以通过执行系统原来自己带的sur切换到root用户
关于chmod 6777 sur命令请参考《chmod命令基本篇》和请参考《chmod命令高级篇( SetUID与SetGID标识位)
关于setuid请参考《setuid()与setgid()的使用 
结束!