8.11setuid.c

时间：2007-12-22 来源：xi2008wang

看完这个程序,绝对会进一步了解与进程相关的实际用户ID,有效用户ID,保存的设置ID 与文件相关的setid位. 与用户相关的uid. [xiaodao@mylinux ~]$ vi 8.11setuid.c #include    <unistd.h>
#include    <stdio.h>
#include    <sys/types.h>
#include    <errno.h> int
main(void)
{
    uid_t euid = geteuid();     printf("uid = %d, euid = %d\n", getuid(), euid); //打印进程的实际用户ID,有效用户ID
    if (setuid(getuid()) == -1) {        //因为getuid()为实际用户ID,因此可以设置进程有效用户ID         printf("setuid %d error\n", getuid());
        exit(1);
    }
    else
        printf("uid = %d, euid = %d\n", getuid(), geteuid()); //验证
    if (setuid(euid) == -1) { //因为euid为保存的设置用户ID,因此可以设置进程的有效用户ID
        printf("setuid %d error, %s\n", euid, strerror(errno)); //        exit(1);
    }
    else
        printf("uid = %d, euid = %d\n", getuid(), geteuid());//验证     exit(0);
}
[xiaodao@mylinux ~]$ gcc 8.11setuid.c
[xiaodao@mylinux ~]$ su
Password:
[root@mylinux xiaodao]# chown test:test a.out
[root@mylinux xiaodao]# chmod u+s a.out         //对文件a.out设置setuid位
[root@mylinux xiaodao]# exit
exit
[xiaodao@mylinux ~]$ ./a.out
uid = 500, euid = 502         //实际用户ID为502,因为文件有setuid位,因此有效用户ID为502
uid = 500, euid = 500          //设置成功,有效用户ID改为500
uid = 500, euid = 502            //设置成功,有效用户ID改为502
[xiaodao@mylinux ~]$