靶机来源： 知攻善防实验室公众号 https://mp.weixin.qq.com/s/gCWGnBiwbqSnafXU1apJCA
我是在另一台主机上通过ssh连接到靶机进行解题的，以下为解题记录，有不对的地方希望各位大佬指正。
背景
前景需要：小王急匆匆地找到小张，小王说”李哥，我dev服务器被黑了”,快救救我！！
挑战内容：
（1）黑客的IP地址
（2）遗留下的三个flag
解题
首先查看当前主机最近的用户登录情况，如何黑客成功登录，那么可以查到成功登录的记录。
[root@localhost defend]# grep "Accepted " /var/log/secure* | awk '{print $1,$2,$3,$9,$11}'
Mar 18 20:23:07 root 192.168.75.129
Mar 20 14:28:21 defend 192.168.1.104
此处可以看到3月18日，root用户进行了登录，IP地址为192.168.75.129，该IP可能就是黑客的IP地址。
IP正确，接着看看有没有黑客新增的用户。
[root@localhost defend]# cat /etc/passwd
root:x:0:0:root:/root:/bin/bash
bin:x:1:1:bin:/bin:/sbin/nologin
daemon:x:2:2:daemon:/sbin:/sbin/nologin
adm:x:3:4:adm:/var/adm:/sbin/nologin
lp:x:4:7:lp:/var/spool/lpd:/sbin/nologin
sync:x:5:0:sync:/sbin:/bin/sync
shutdown:x:6:0:shutdown:/sbin:/sbin/shutdown
halt:x:7:0:halt:/sbin:/sbin/halt
mail:x:8:12:mail:/var/spool/mail:/sbin/nologin
operator:x:11:0:operator:/root:/sbin/nologin
games:x:12:100:games:/usr/games:/sbin/nologin
ftp:x:14:50:FTP User:/var/ftp:/sbin/nologin
nobody:x:99:99:Nobody:/:/sbin/nologin
systemd-network:x:192:192:systemd Network Management:/:/sbin/nologin
dbus:x:81:81:System message bus:/:/sbin/nologin
polkitd:x:999:998:User for polkitd:/:/sbin/nologin
libstoragemgmt:x:998:996:daemon account for libstoragemgmt:/var/run/lsm:/sbin/nologin
colord:x:997:995:User for colord:/var/lib/colord:/sbin/nologin
rpc:x:32:32:Rpcbind Daemon:/var/lib/rpcbind:/sbin/nologin
saned:x服务器托管网:996:993:SANE scanner daemon user:/usr/share/sane:/sbin/nologin
saslauth:x:995:76:Saslauthd user:/run/saslauthd:/sbin/nologin
abrt:x:173:173::/etc/abrt:/sbin/nologin
setroubleshoot:x:994:991::/var/lib/setroubleshoot:/sbin/nologin
rtkit:x:172:172:RealtimeKit:/proc:/sbin/nologin
pulse:x:171:171:PulseAudio System Daemon:/var/run/pulse:/sbin/nologin
chrony:x:993:988::/var/lib/chrony:/sbin/nologin
unbound:x:992:987:Unbound DNS resolver:/etc/unbound:/sbin/nologin
radvd:x:75:75:radvd user:/:/sbin/nologin
tss:x:59:59:Account used by the trousers package to sandbox the tcsd daemon:/dev/null:/sbin/nologin
usbmuxd:x:113:113:usbmuxd user:/:/sbin/nologin
geoclue:x:991:985:User for geoclue:/var/lib/geoclue:/sbin/nologin
qemu:x:107:107:qemu user:/:/sbin/nologin
gluster:x:990:984:GlusterFS daemons:/run/gluster:/sbin/nologin
gdm:x:42:42::/var/lib/gdm:/sbin/nologin
rpcuser:x:29:29:RPC Service User:/var/lib/nfs:/sbin/nologin
nfsnobody:x:65534:65534:Anonymous NFS User:/var/lib/nfs:/sbin/nologin
gnome-initial-setup:x:989:983::/run/gnome-initial-setup/:/sbin/nologin
sshd:x:74:74:Privilege-separated SSH:/var/empty/sshd:/sbin/nologin
avahi:x:70:70:Avahi mDNS/DNS-SD Stack:/var/run/avahi-daemon:/sbin/nologin
postfix:x:89:89::/var/spool/postfix:/sbin/nologin
ntp:x:38:38::/etc/ntp:/sbin/nologin
tcpdump:x:72:72::/:/sbin/nologin
defend:x:1000:1000:defend:/home/defend:/bin/bash
redis:x:988:982:Redis Database Server:/var/lib/redis:/sbin/nologin
这里好像没有看到可疑用户，接着看看有没有可疑的进程
[root@localhost defend]# ps -aux
USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND
root 1 0.3 0.1 193824 7000 ? Ss 14:25 0:03 /usr/lib/systemd/systemd --switched-root --system --deserialize 22
root 2 0.0 0.0 0 0 ? S 14:25 0:00 [kthreadd]
root 4 0.0 0.0 0 0 ? S也没有看到可疑的进程，那就看看黑客登录成功之后都执行过什么命令
[root@localhost defend]# history
1 ls
2 chmod +x /etc/rc.d/rc.local
3 cat /etc/rc.d/rc.local
4 vim /etc/rc.d/rc.local
5 echo flag{thisismybaby}
6 exit
7 grep "Accepted " /var/log/secure* | awk '{print $1,$2,$3,$9,$11}'
8 cat /etc/passwd
9 netstat -anltup
10 ps -aux
11 history
这里直接发现了第一个flag：flag{thisismybaby}
除此之外，还发现黑客编辑了开机启动文件rc.local，查看一下这个文件
[root@localhost defend]# cat /etc/rc.d/rc.local
#!/bin/bash
# THIS FILE IS ADDED FOR COMPATIBILITY PURPOSES
#
# It is highly advisable to create own systemd services or udev rules
# to run scripts during boot instead of using this file.
#
# In contrast to previous versions due to parallel execution during boot
# this script will NOT be run after all other services.
#
# Please note that you must run 'chmod +x /etc/rc.d/rc.local' to ensure
# that this script will be executed during boot.
# flag{kfcvme50}
touch /var/lock/subsys/local
在该文件中发现了第二个flag：flag{kfcvme50}
按照黑客的攻击思路，此时黑客已经拿到了root用户权限并且可以实现权限维持。那么第三个flag应该不会在计划任务中，而是在黑客打进来的地方。
那么黑客是怎么打进来的？
此时，想到了刚才查看passwd文件时，最后一个用户是redis用户，说明该机器上存在redis服务，于是查看网络连接，看看6379端口是否开放。
[root@localhost defend]# netstat -anltup
Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name
tcp 0 0 127.0.0.1:25 0.0.0.0:* LISTEN 1291/master
tcp 0 0 0.0.0.0:111 0.0.0.0:* LISTEN 761/rpcbind
tcp 0 0 192.168.122.1:53 0.0.0.0:* LISTEN 1703/dnsmasq
tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN 1089/sshd
tcp 0 0 127.0.0.1:631 0.0.0.0:* LISTEN 1092/cupsd
tcp 0 0 192.168.1.105:22 192.168.1.104:59096 ESTABLISHED 3160/sshd: defend [
tcp6 0 0 ::1:25 :::* LISTEN 1291/master
tcp6 0 0 :::111 :::* LISTEN 761/rpcbind
tcp6 0 0 :::22 :::* LISTEN 1089/sshd
tcp6 0 0 ::1:631 :::* LISTEN 1092/cupsd
udp 0 0 192.168.122.1:53 0.0.0.0:* 1703/dnsmasq
udp 0 0 0.0.0.0:67 0.0.0.0:* 1703/dnsmasq
udp 0 0 0.0.0.0:68 0.0.0.0:* 3052/dhclient
udp 0 0 0.0.0.0:服务器托管网111 0.0.0.0:* 761/rpcbind
udp 0 0 127.0.0.1:323 0.0.0.0:* 821/chronyd
udp 0 0 0.0.0.0:914 0.0.0.0:* 761/rpcbind
udp 0 0 0.0.0.0:56315 0.0.0.0:* 802/avahi-daemon: r
udp 0 0 0.0.0.0:5353 0.0.0.0:* 802/avahi-daemon: r
udp6 0 0 :::111 :::* 761/rpcbind
udp6 0 0 ::1:323 :::* 821/chronyd
udp6 0 0 :::914 :::* 761/rpcbind
没有发现6379端口，那么先运行该服务。
[root@localhost defend]# redis-server
4368:C 20 Mar 14:55:04.305 # Warning: no config file specified, using the default config. In order to specify a config file use redis-server /path/to/redis.conf
4368:M 20 Mar 14:55:04.306 * Increased maximum number of open files to 10032 (it was originally set to 1024).
_._
_.-``__ ''-._
_.-`` `. `_. ''-._ Redis 3.2.12 (00000000/0) 64 bit
.-`` .-```. ```/ _.,_ ''-._
( ' , .-` | `, ) Running in standalone mode
|`-._`-...-` __...-.``-._|'` _.-'| Port: 6379
| `-._ `._ / _.-' | PID: 4368
`-._ `-._ `-./ _.-' _.-'
|`-._`-._ `-.__.-' _.-'_.-'|
| `-._`-._ _.-'_.-' | http://redis.io
`-._ `-._`-.__.-'_.-' _.-'
|`-._`-._ `-.__.-' _.-'_.-'|
| `-._`-._ _.-'_.-' |
`-._ `-._`-.__.-'_.-' _.-'
`-._ `-.__.-' _.-'
`-._ _.-'
`-.__.-'
4368:M 20 Mar 14:55:04.309 # WARNING: The TCP backlog setting of 511 cannot be enforced because /proc/sys/net/core/somaxconn is set to the lower value of 128.
4368:M 20 Mar 14:55:04.309 # Server started, Redis version 3.2.12
4368:M 20 Mar 14:55:04.309 # WARNING overcommit_memory is set to 0! Background save may fail under low memory condition. To fix this issue add 'vm.overcommit_memory = 1' to /etc/sysctl.conf and then reboot or run the command 'sysctl vm.overcommit_memory=1' for this to take effect.
4368:M 20 Mar 14:55:04.309 # WARNING you have Transparent Huge Pages (THP) support enabled in your kernel. This will create latency and memory usage issues with Redis. To fix this issue run the command 'echo never > /sys/kernel/mm/transparent_hugepage/enabled' as root, and add it to your /etc/rc.local in order to retain the setting after a reboot. Redis must be restarted after THP is disabled.
4368:M 20 Mar 14:55:04.310 * DB loaded from disk: 0.001 seconds
4368:M 20 Mar 14:55:04.310 * The server is now ready to accept connections on port 6379
redis运行起来之后，需要进行登录，但是不知道密码，那就先尝试一下redis未授权。
[root@localhost defend]# redis-cli -h 127.0.0.1
127.0.0.1:6379>
直接登录成功，那么黑客应该是通过redis未授权打进来的，看看/root/.ssh下有没有被写入ssh密钥
[root@localhost .ssh]# pwd
/root/.ssh
[root@localhost .ssh]# ls -liah
total 4.0K
51847075 drwxr-xr-x. 2 root root 29 Mar 18 20:22 .
33582977 dr-xr-x---. 7 root root 265 Mar 18 20:25 ..
51847076 -rw-r--r--. 1 root root 661 Mar 18 20:22 authorized_keys
[root@localhost .ssh]# cat authorized_keys
REDIS0007� redis-ver3.2.12�
redis-bits�@�ctime�2�eused-mem��h
��TJB=
ssh-rsa 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 chinaran@kali
�nh����[root@localhost .ssh]#
到此，推测黑客是通过redis未授权写入ssh密钥进行登录，然后通过写入开机启动文件进行权限维持。
接着来寻找第三个flag。到此，由于我比较菜就没啥思路了，于是就看看有哪些文件被修改过。
[root@localhost .ssh]# rpm -Vf /usr/bin/*
file /usr/bin/alt-java is not owned by any package
SM5....T. c /etc/rc.d/rc.local
SM5....T. c /etc/rc.d/rc.local
file /usr/bin/ControlPanel is not owned by any package
SM5....T. c /etc/rc.d/rc.local
SM5....T. c /etc/rc.d/rc.local
file /usr/bin/itweb-settings is not owned by any package
file /usr/bin/java is not owned by any package
file /usr/bin/javaws is not owned by any package
SM5....T. c /etc/rc.d/rc.local
SM5....T. c /etc/rc.d/rc.local
file /usr/bin/keytool is not owned by any package
SM5....T. c /etc/rc.d/rc.local
SM5....T. c /etc/rc.d/rc.local
SM5....T. c /etc/rc.d/rc.local
file /usr/bin/orbd is not owned by any package
file /usr/bin/pack200 is not owned by any package
file /usr/bin/policyeditor is not owned by any package
file /usr/bin/policytool is not owned by any package
missing /var/run/pulse
file /usr/bin/readcd is not owned by any package
S.5....T. c /etc/redis.conf
S.5....T. c /etc/redis.conf
S.5....T. c /etc/redis.conf
S.5....T. c /etc/redis.conf
S.5....T. c /etc/redis.conf
S.5....T. c /etc/redis.conf
file /usr/bin/rmid is not owned by any package
file /usr/bin/rmiregistry is not owned by any package
file /usr/bin/servertool is not owned by any package
SM5....T. c /etc/rc.d/rc.local
从上面看到redis的配置文件/etc/redis.conf被修改过，打开看看
[root@localhost defend]# cat /etc/redis.conf
# flag{P@ssW0rd_redis}
# Redis configuration file example.
#
# Note that in order to read the configuration file, Redis must be
# started with the file path as first argument:
#
# ./redis-server /path/to/redis.conf
# Note on units: when memory size is needed, it is possible to specify
# it in the usual form of 1k 5GB 4M and so forth:
#
# 1k => 1000 bytes
# 1kb => 1024 bytes
# 1m => 1000000 bytes
# 1mb => 1024*1024 bytes
# 1g => 1000000000 bytes
# 1gb => 1024*1024*1024 bytes
#
# units are case insensitive so 1GB 1Gb 1gB are all the same.
直接在第一行看到了第三个flag：flag{P@ssW0rd_redis}
至此，就拿到了三个flag。
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