通过glibc提供的库函数

[23:02:14] gcc chmodtest.c [23:02:17] ls -l kali   //记得先创建这个文件-rwxrwxrwx. 1 root root 0 May 10 22:56 kali[23:02:25] ./a.outchmod succeed[23:02:29] ls -l kali-rw-rw-rw-. 1 root root 0 May 10 22:56 kali[23:02:34] cat chmodtest.c #include
     
      int main(){        int rc=chmod("./kali",0666);  //这个必须是4个数字，我用三个数，发现修改的权限对不上        if(rc==-1)        {                perror("chmod fail\n");  //这个是用来打印错误的        }        else                printf("chmod succeed\n");        return 0;}[23:02:46]
     

通过syscall直接调用

[23:10:58] gcc chmodtest1.c[23:11:01] ls -l kali-rw-rw-rw-. 1 root root 0 May 10 22:56 kali[23:11:06] ./a.outchmod succeed[23:11:09] ls -l kali-rwxrwxrwx. 1 root root 0 May 10 22:56 kali[23:11:13] cat chmodtest1.c #include
     
      #include
      
       #include
       
        int main(){        int rc=syscall(SYS_chmod,"./kali",0777);//syscall在头文件unistd.h中，SYS_chmod在头文件syscall.h中        if(rc==-1)        {                perror("chmod fail\n");        }        else                printf("chmod succeed\n");        return 0;}[23:11:18]
       
      
     

通过 int 指令陷入（还没有理解是什么意思）

#include 
     
      #include 
      
       #include 
       
        #include 
        
         int main(){        long rc;        char *file_name = "/etc/passwd";        unsigned short mode = 0444;        asm(                "int $0x80"                : "=a" (rc)                : "0" (SYS_chmod), "b" ((long)file_name), "c" ((long)mode)        );        if ((unsigned long)rc >= (unsigned long)-132) {                errno = -rc;                rc = -1;        }        if (rc == -1)                fprintf(stderr, "chmode failed, errno = %d\n", errno);        else                printf("success!\n");        return 0;}