ruby_olm

A Ruby wrapper for the olm double ratchet implementation from matrix.

This wrapper provides classes and methods that line up with the olm interface, as well as a set of helpers and short aliases.

Very much a work in progress.

Installation

The gem name is 'ruby_olm'. The target needs to be able to build native extensions.

Once installed, require as:

require 'ruby_olm'

If using locally (i.e. you check out this repository) you may need to manually compile and clean the extensions like this:

bundle exec rake compile
bundle exec rake clean

Characteristics

• Interfaces are not thread safe
• Olm always encodes binary as base64
• Account is unlikely to scale for a large number of one-time-keys

Example

Alice wants to send a message to Bob:

require 'ruby_olm'

include RubyOlm

alice = Account.new
bob = Account.new

# Alice wants to send a message to Bob
alice_msg = "hi bob"

# Bob generates a one-time-key
bob.gen_otk

# Alice must have Bob's identity and one-time-key to make a session
alice_session = alice.outbound_session(bob.ik['curve25519'], bob.otk['curve25519'].values.first)

# Bob marks all one-time-keys as published
bob.mark_otk

# Alice can encrypt
encrypted = alice_session.encrypt(alice_msg)
assert_instance_of PreKeyMessage, encrypted

# Bob can create a session from this first message
bob_session = bob.inbound_session(encrypted)

# Bob can now update his list of marked otk (since he knows one has been used)
bob.update_otk(bob_session)

# Bob can decrypt Alice's message
bob_msg = bob_session.decrypt(encrypted)

assert_equal alice_msg, bob_msg

# At this point Bob has received but Alice hasn't
assert bob_session.has_received?
refute alice_session.has_received?

# Bob can send messages back to Alice    
bob_msg = "hi alice"

encrypted = bob_session.encrypt(bob_msg)
assert_instance_of Message, encrypted

alice_msg = alice_session.decrypt(encrypted)

assert_equal alice_msg, bob_msg 

Account and Session instances can be serialised and deserialised using the #to_pickle and ::from_pickle methods. This is handy for saving and restoring state:

# save
alice_saved_account = Alice.to_pickle
alice_saved_session = alice_session.to_pickle

# restore
Account.from_pickle(alice_saved_account)
Session.from_pickle(alice_saved_session)

Running Tests

bundle exec rake test

Todo

• documentation
• more testing
• add support for megolm
• replace built-in olm crypto with Ruby openssl

What is an Olm?

https://en.wikipedia.org/wiki/Olm.

License

Apache 2.0