Leviathan Node

This is an Erlang node that contains:

1. erl_sshd
2. dobby_core_lib
3. dobby_rest_lib
4. dobby_ui_lib
5. lucet_core_lib
6. leviathan_lib
7. erl_cowboy

Table of Contents

• Leviathan Node
  • Requirements
  • Building
  • Running
  • Connecting via ssh
  • websocket log viewer
  • Configuring TLS
  • Example
  • Multi-host version

Requirements

• Erlang R17+
• npm

Building

To build the application call: make. This will:

• download the dependencies,
• compile the code,
• copy the dobby_ui_lib nodeJS artefact to the dobby_rest/priv/static/www
• generate an Erlang release,
• generate ssh keys
  • private and public user keys: ida_rsa and id_rsa.pub respectively in the project root directory
  • public and private system keys in the priv/erl_sshd that will be used by the ssh deamon running in the Erlang node
  • authorized_keys file that will already have the previously generated user public key

You may add your own public keys to the authorized_keys file in priv/erl_sshd (remember to make rel afterwards).

If you want to connect to the dobby Erlang shell using ssh with a username and password, add or modify the usernames and passwords to the erl_sshd section of config/sys.config.

Running

_rel/leviathan/bin/leviathan

To access the Dobby Visualizer go to http://localhost:8080/static/www/index.html

Connecting via ssh

If you genereated keys in erl_sshd before generating the dobby release, you can connect to the dobby server's Erlang shell using ssh.

ssh 127.0.0.1 -p 11155 -i id_rsa

To exit the Erlang shell obtained via ssh call exit().

websocket log viewer

Logs are published to websocket clients connecting to ws://.../lager/websocket. A simple viewer is provided at http://.../lager/static/www/index.html.

Configuring TLS

To enable TLS support for the HTTP interface you have to configure it in the erl_cowboy application and provide the following options:

• certificate file name (expected in the priv/erl_cowboy)
• key file name (expected in the priv/erl_cowboy)
• password to the key if it is password protected

The configuration has to be placed in the sys.config file. Below is an example:

[
...
 {erl_cowboy, [
               {port, 8080},
               {listeners, 10},
               {app, leviathan},
               {tls_enabled, true},
               {tls_opts, [{certfile, "dummy.crt"},
                           {keyfile, "dummy.key"},
                           {password, ""}]}
               ]},
...
]

There is a sample certificate and key generator that you can run with: make tls. The above example config works with the generated files. To test the TLS, put the config snippet into the config/sys.config. Remember to re-generated the release after the change.

With TLS enabled, the Visualizer can be accessed via https://localhost:8080/static/www/index.html.

Example

An example usage of Leviathan is described in the example file.

Multi-host version

There is a multi-host version of Leviathan on the multi-host branch.