r n s h  Shell over Reticulum

     

rnsh is a utility written in Python that facilitates shell sessions over Reticulum networks. It is based on the rnx utility that ships with Reticulum and aims to provide a similar experience to SSH.

Contents

• Alpha Disclaimer
• Recent Changes
• Quickstart
• Options
• How it works
• Roadmap
• Active TODO

Reminder: Alpha Software

These early versions will be buggy. There will sometimes be major breaking changes to the command line parameters between releases. There will sometimes be breaking changes in the protocol between releases. Use at your own peril!

Recent Changes

v0.0.10

• Rate limit window change events to prevent saturation of transport
• Tweaked some loop timers to improve CPU utilization

v0.0.9

• Switch to a new packet-based protocol
• Bug fixes and dependency updates

v0.0.8

• Improved test suite exposed several issues with the handling of command line arguments which are now fixed
• Fixed a race condition that would cause remote characters to be lost intermittently when running remote commands that finish immediately.
• Added automated testing that actually spins up a random listener and initiator in a private Reticulum network and passes data between them, uncovering more issues which are now fixed.
• Fixed (hopefully) an issue where rnsh doesn't know what version it is.

v0.0.7

Added -A command line option. This listener option causes the remote command line to be appended to the arguments list of the launched program. This allows the listener to jail connections to a particular executable while still allowing parameters.

v0.0.6

Minor improvements in transport efficiency

v0.0.5

Remote command line and pipe compatibility

Command line options have changed somewhat to allow the initiator to supply a command line. This allows rnsh to function similarly to SSH. You can pipe into or out of rnsh to send input through remote commands or remote command output through other commands.

This behavior can be blocked on the listener with the -C option.

When the initiator does not supply a command, the listener uses a default command specified on its command line. If a default command is not specified, the listener falls back to the shell of the user it is running under.

Quickstart

Tested (thus far) on Python 3.11 macOS 13.1 ARM64. Should run on Python 3.6+ on Linux or Unix. WSL probably works. Cygwin might work, too.

• Activate a virtualenv
• pip3 install rnsh
  • Or from a whl release, pip3 install /path/to/rnsh-0.0.1-py3-none-any.whl
• Configure Reticulum interfaces, check with rnstatus
• Ready to run rnsh. The options are shown below.

Example: Shell server

Setup

Before running the listener or initiator, you'll need to get the listener destination hash and the initiator identity hash.

# On listener
rnsh -l -p

# On initiator
rnsh -p

Note: if you are using a non-default identity or service name, be sure to supply these options with -p as the identity and destination hashes will change depending on these settings.

Listener

• Listening for default service name ("default").
• Using user's default Reticulum config dir (~/.reticulum).
• Using default identity ($RNSCONFIGDIR/storage/identities/rnsh).
• Allowing remote identity 6d47805065fa470852cf1b1ef417a1ac to connect.
• Launching /bin/zsh on authorized connect.

rnsh -l -a 6d47805065fa470852cf1b1ef417a1ac -- /bin/zsh

Initiator

• Connecting to default service name ("default").
• Using user's default Reticulum config dir (~/.reticulum).
• Using default identity ($RNSCONFIGDIR/storage/identities/rnsh).
• Connecting to destination a5f72aefc2cb3cdba648f73f77c4e887

rnsh a5f72aefc2cb3cdba648f73f77c4e887

Options

Usage:
    rnsh [--config <configdir>] [-i <identityfile>] [-s <service_name>] [-l] -p
    rnsh -l [--config <configfile>] [-i <identityfile>] [-s <service_name>] 
         [-v... | -q...] [-b <period>] (-n | -a <identity_hash> [-a <identity_hash>] ...) 
         [-A | -C] [[--] <program> [<arg> ...]]
    rnsh [--config <configfile>] [-i <identityfile>] [-s <service_name>] 
         [-v... | -q...] [-N] [-m] [-w <timeout>] <destination_hash> 
         [[--] <program> [<arg> ...]]
    rnsh -h
    rnsh --version

Options:
    --config DIR                 Alternate Reticulum config directory to use
    -i FILE --identity FILE      Specific identity file to use
    -s NAME --service NAME       Listen on/connect to specific service name if not default
    -p --print-identity          Print identity information and exit
    -l --listen                  Listen (server) mode. If supplied, <program> <arg>...will 
                                   be used as the command line when the initiator does not
                                   provide one or when remote command is disabled. If
                                   <program> is not supplied, the default shell of the 
                                   user rnsh is running under will be used.
    -b --announce PERIOD         Announce on startup and every PERIOD seconds
                                 Specify 0 for PERIOD to announce on startup only.
    -a HASH --allowed HASH       Specify identities allowed to connect
    -n --no-auth                 Disable authentication
    -N --no-id                   Disable identify on connect
    -A --remote-command-as-args  Concatenate remote command to argument list of <program>/shell
    -C --no-remote-command       Disable executing command line from remote
    -m --mirror                  Client returns with code of remote process
    -w TIME --timeout TIME       Specify client connect and request timeout in seconds
    -q --quiet                   Increase quietness (move level up), multiple increases effect
                                          DEFAULT LOGGING LEVEL
                                                  CRITICAL (silent)
                                    Initiator ->  ERROR
                                                  WARNING
                                     Listener ->  INFO
                                                  DEBUG    (insane)
    -v --verbose                 Increase verbosity (move level down), multiple increases effect
    --version                    Show version
    -h --help                    Show this help

How it works

Listeners

Listener instances are the servers. Each listener is configured with an RNS identity, and a service name. Together, RNS makes these into a destination hash that can be used to connect to your listener.

Multiple listeners can use the same identity. As long as they are given different service names. They will have different destination hashes and not conflict.

Listeners must be configured with a command line to run (at least at this time). The identity hash string is set in the environment variable RNS_REMOTE_IDENTITY for use in child programs.

Listeners are set up using the -l flag.

Initiators

Initiators are the clients. Each initiator has an identity hash which is used as an authentication mechanism on Reticulum. You'll need this value to configure the listener to allow your connection. It is possible to run the server without authentication, but hopefully it's obvious that this is an advanced use case.

To get the identity hash, use the -p flag.

With the initiator identity set up in the listener command line, and with the listener identity copied (you'll need to do -p on the listener side, too), you can run the initiator.

I recommend staying pretty vanilla to start with and trying /bin/zsh or whatever your favorite shell is these days. The shell should start in login mode. Ideally it works just like an ssh shell session.

Protocol

The protocol is build on top of the Reticulum Request and Packet APIs.

• After the initiator identifies on the connection, it enters a request loop.
• When idle, the initiator will periodically poll the listener.
• When the initiator has data available (i.e the user typed some characters), the initiator will send that data to the listener in a request, and the listener will respond with any data available from the listener.
• When the listener has new data available, it notifies the initiator using a notification packet. The initiator then makes a request to the listener to fetch the data.

Roadmap

1. Plan a better roadmap
2. ?
3. Keep my day job

TODO

• Initial version
• Pip package with command-line utility support
• Publish to PyPI
• Improve signal handling
• Make it scriptable (currently requires a tty)
• Protocol improvements (throughput!)
• Documentation improvements
• Test on several platforms
• Fix issues that come up with testing
• Fix issues with running rnsh in a binary pipeline, i.e. piping the output of tar over rsh.
• Beta release
• Test and fix more issues
• V1.0
• Enhancement Ideas
  • authorized_keys mode similar to SSH
  • Git over rnsh (git remote helper)
  • Sliding window acknowledgements for improved throughput

Miscellaneous

By piping into/out of rnsh, it should be possible to transfer files using the same method discussed in this article. I tested it just now and it doesn't work right. There's probably some subtle garbling of the data at one end of the stream or the other.