Local Proxy for Cumulocity Cloud Remote Access

This is a proxy implementation for the Cloud Remote Access feature of Cumulocity which allows to connect to devices using native TCP-based clients like ssh, vnc, rdp etc.

Main purpose of this proxy is to bridge all TCP packets via WebSocket. The local proxy is designed to run on clients where the native client software is installed.

The proxy is written in Python3.

Installation

Migration Notes

If your are upgrade from 1.x please see the MIGRATION to V2 NOTES as there are some breaking changes. Please forgive us, but you can be sure it is worth it! Version 2.x brings a lot of great features like interactive ssh sessions and plugins to make c8ylp even more useful!

The Local Proxy can be installed via pip, or manually installed from the repository by cloning it.

Additionally a Debian package (.deb) can be created by building the project yourself and hosting the package in your own Debian repository. See the DEVELOPER notes for details.

Installation via pip (hosted in pypi)

pip install c8ylp

Note: Depending on your python setup, you may need to use pip3 instead of pip.

Installing a specific version

You can install specific version by specifying the version number when using pip.

pip install c8ylp==1.5.0

Or if you want to install the latest v1.x version and do not want to upgrade to v2.x until you are ready, then use:

pip install "c8ylp<2.0.0"

Installation from Source Code

Clone the project, then navigate to the root folder of the project and run:

pip install .

Usage

Prerequisites & Limitations

• PASSTHROUGH endpoint: To use the local proxy you need a remote access PASSTHROUGH endpoint configured on each of your devices you want to connect to. See this guide for further details: https://tech.forums.softwareag.com/t/how-to-get-started-with-cloud-remote-access-for-cumulocity-iot/258446#step-by-step-guide-to-setup-a-passthrough-connection-16

• Tenant Authentication Method: The desired tenant must be configured to use the OAI Secure Authentication. Read more: https://cumulocity.com/guides/users-guide/administration/#authentication

• Single Device Tunnel only: The Local Proxy needs to be executed for each device tunnel you want to establish. Multiple device tunnels per single Local Proxy Instance is currently not supported due to the limitation of the SSH Protocol.

Run c8ylp

c8ylp supports different commands depending on your use case. The commands are organized in a multi-level command structure. The list of available commands and subcommands can be shown by using the --help/-h option.

The command can be launched by either using the c8ylp binary or by calling the c8ylp module via python.

c8ylp

# or calling via python (or use python3)
python -m c8ylp

The available commands can be shown using:

% c8ylp --help
Usage: c8ylp [OPTIONS] COMMAND [ARGS]...

Options:
  --help  Show this message and exit.

Commands:
  connect  Connect to a device via different protocols
  login    Login and save token to an environment file
  plugin   Run a custom plugin (installed under ~/.c8ylp/plugins/)
  server   Start local proxy in server mode
  version  Show the c8ylp version number

Common usages

The following scenarios show the common use cases of c8ylp.

Launching as local proxy server

c8ylp server <device> --env-file .env

The port information will be shown in the terminal so that you can connect to it via a client corresponding to the protocol currently being used on the device (i.e. ssh, vnc etc.)

Launching as local proxy server then launching an interactive ssh session

If you just want to connect via ssh using a once-off proxy instance using a random port number (to prevent conflicts with other applications), then use:

c8ylp connect ssh <device> --ssh-user <device_username> --env-file .env

Usage with a socket path

This is a unix only option

c8ylp server <device> --env-file .env --socket-path /tmp/device.socket

then connect with ssh like:

ssh -o 'ProxyCommand=socat - UNIX-CLIENT:/tmp/device.socket' <device_username>@localhost

Usage with stdin-/out forwarding

Using stdin/out forwarding to Cumulocity enables the use of c8ylp as a proxy command without the need of a local TCP server. As proxy commands cannot interact with the user you have to ensure there is an active Cumulocity session.

The session can be ensured by using the c8ylp login --env-file .env command that will update the environment file. As long as the session is active the Cumulocity server can be used as proxy command with ssh as following:

ssh -o 'ProxyCommand=c8ylp server <device> --stdio --env-file .env' <device_username>@<device>

By adding the proxy command to the .ssh/config file, the usage of the Cumulocity server can be simplified even more. The file allows to define user and environment file so the connection can be done by simply typing ssh <device>. For this use the following example configuration (%n will be replaced by ssh with the given device name):

Host <device>
    User <device_username>
    PreferredAuthentications publickey
    IdentityFile <identify_file>
    ServerAliveInterval 120
    StrictHostKeyChecking no
    UserKnownHostsFile /dev/null
    ProxyCommand c8ylp server %n --stdio --env-file .env

# Or you can create a generic ssh config for all devices with a similar prefix:
# Usage;
#   => ssh linux-device01
#   => ssh linux-device02
Host linux-*
    User admin
    PreferredAuthentications publickey
    IdentityFile ~/.ssh/myprivatekey
    ServerAliveInterval 120
    StrictHostKeyChecking no
    UserKnownHostsFile /dev/null
    ProxyCommand c8ylp server %n --stdio --env-file .env

Command documentation

The command usage and all options can be viewed online on the following pages:

• c8ylp
• c8ylp login
• c8ylp server
• c8ylp connect
• c8ylp connect ssh
• c8ylp plugin
• c8ylp plugin command
• c8ylp version

Configuration

c8ylp can be configured via command line options or environment variables. The environment variables can either be set via the shell, or by using a dotenv file (i.e. .env). When using a dotenv (environment) file then it needs to be provide to the --env-file <file> option.

Example Usage: dotenv file

Create a file called .env and add the following contents:

# Cumulocity settings
C8Y_HOST=<cumulocity_host>
C8Y_USER=<your_cumulocity_username>

# c8ylp settings
C8YLP_VERBOSE=true

Then reference the file from the command line:

c8ylp server test-device --env-file .env

You can also set the path the dotenv file via an environment variable to save you adding it to all your commands manually. i.e.:

# bash/zsh
export C8YLP_ENV_FILE=tenant1.config

# Now call c8ylp, and it will read the dotenv file "tenant1.config" automatically
c8ylp connect ssh my-device-name

The environment variables corresponding to each option can be viewed by using the in-built help for each command.

c8ylp server --help

c8ylp connect ssh --help

Please note that the Local Proxy will block the current terminal session. If you want to use it in background just use "&" and/or "nohup". As the relevant information will be stored in a log file as well you can forward the output to dev/null or to syslog if you want to do so.

c8ylp server [options] > /dev/null 2>&1

If no TCP Client is connected but Web Socket Connection is open it might get be terminated by a server timeout. The Local Proxy will automatically reestablish the connection in this case.

If a TCP Client has been connected and the Web Socket Connection gets terminated, the TCP Client Connection will be terminated which results in that the Local Proxy terminates and needs to be restarted manually.

Tab completion

c8ylp (version >= 2.0.0) supports tab completion for bash, zsh and fish shells.

To add/activate the completions you will need to add the corresponding line to your shell profile, and reload your shell afterwards.

Note

Unfortunately tab completion is not supported in PowerShell or Cygwin.

# bash (profile: ~/.bashrc)
eval "$(_C8YLP_COMPLETE=bash_source c8ylp)"

# zsh (profile: ~/.zshrc)
eval "$(_C8YLP_COMPLETE=zsh_source c8ylp)"

# fish (profile: ~/.config/fish/config.fish)
_C8YLP_COMPLETE=fish_source c8ylp | source

Plugins

c8ylp can be extended in the form of plugins. Both python based plugins and bash scripts are supported. Checkout the plugins documentation for more information about how to create your own plugin, but it is intended for advanced users only. For simple one liners have a look at using the in-built generic plugin c8ylp plugin command instead.

Plugins are loaded at runtime and can be listed by running the following command:

c8ylp plugin

Log

The log file can be found in the following directory.

~/.c8ylp/*.log

Where ~ is your user folder.

To increase the detail of log use the option --verbose or -v. If set, the log will be written on debug level.

Log information will not be printed out to the console by default unless the --verbose or -v option is used. The log file however is always active to help provide a record of activities and to help diagnose any problems should they arise.

You can suppress all console message (i.e. stdout) by redirecting the output to /dev/null.

# bash/zsh
c8ylp [OPTIONS] > /dev/null 2>&1

Dependencies

The Local Proxy depends on the following components packages. The dependencies will be automatically installed when installing via pip or if you are installing c8ylp via a manually built Debian package (.deb).

• certifi
• click
• requests
• setuptools
• websocket_client

Contributing

Checkout the DEVELOPER Notes to see how to contribute to the project.

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These tools are provided as-is and without warranty or support. They do not constitute part of the Software AG product suite. Users are free to use, fork and modify them, subject to the license agreement. While Software AG welcomes contributions, we cannot guarantee to include every contribution in the master project.

For more information you can Ask a Question in the Tech Community Forums.