A minimal ActivityPub server.

Based on the specification: https://www.w3.org/TR/activitypub

Also: https://raw.githubusercontent.com/w3c/activitypub/gh-pages/activitypub-tutorial.txt

https://blog.dereferenced.org/what-is-ocap-and-why-should-i-care

https://alexcastano.com/what-is-activity-pub

This project is currently pre alpha and not recommended for any real world uses.

Goals

• A minimal ActivityPub server, comparable to an email MTA.
• AGPLv3+
• Server-to-server and client-to-server protocols supported.
• Implemented in a common language (Python 3)
• Keyword filtering.
• Being able to build crowdsouced organizations with roles and skills
• Sharings collection, similar to the gnusocial sharings plugin
• Quotas for received posts per day, per domain and per account
• Hellthread detection and removal
• Support content warnings, reporting and blocking.
• http signatures and basic auth.
• Compatible with http (onion addresses), https and dat.
• Minimal dependencies.
• Capabilities based security
• Support image blurhashes
• Data minimization principle. Configurable post expiry time.
• Likes and repeats only visible to authorized viewers
• ReplyGuy mitigation - maxmimum replies per post or posts per day
• Ability to delete or hide specific conversation threads
• Commandline interface. If there's a GUI it should be a separate project.
• Designed for intermittent connectivity. Assume network disruptions.
• Limited visibility of follows/followers
• Suitable for single board computers.

Install

On Arch/Parabola:

sudo pacman -S tor python-pip python-pysocks python-pycryptodome python-beautifulsoup4 imagemagick python-pillow python-numpy
sudo pip install commentjson

Or on Debian:

sudo apt-get -y install tor python3-pip python3-socks imagemagick python3-numpy python3-setuptools python3-crypto python3-pil.imagetk
sudo pip3 install commentjson beautifulsoup4 pycryptodome

Running Tests

To run the unit tests:

python3 epicyon.py --tests

To run the network tests. These simulate instances exchanging messages.

python3 epicyon.py --testsnetwork

Account Management

The first thing you will need to do is to create an account. You can do this with the command:

python3 epicyon.py --addaccount nickname@domain --password [yourpassword]

To remove an account (be careful!):

python3 epicyon.py --rmaccount nickname@domain

To change the password for an account:

python3 epicyon.py --changepassword nickname@domain newpassword

To set an avatar for an account:

python3 epicyon.py --nickname [nick] --domain [name] --avatar [image filename]

To set the background image for an account:

python3 epicyon.py --nickname [nick] --domain [name] --background [image filename]

Running the Server

To run with defaults:

python3 epicyon.py

In a browser of choice (but not Tor browser) you can then navigate to:

http://localhost:8085/users/admin

If it's working then you should see the json actor for the default admin account.

For a more realistic installation you can run on a defined domain and port:

python3 epicyon.py --domain [name] --port 8000 --https

You will need to proxy port 8000 through your web server and set up CA certificates as needed.

By default data will be stored in the directory in which you run the server, but you can also specify a directory:

python3 epicyon.py --domain [name] --port 8000 --https --path [data directory]

Defining a perimeter

By default the server will federate with any others, but there may be cases where you want to limit this down to a defined set of servers within an organization.

You can specify the domains which can federate with your server with the --federate option.

python3 epicyon.py --domain [name] --port 8000 --https --federate domain1.net domain2.org domain3.co.uk

Following other accounts

With your server running you can then follow other accounts with:

python3 epicyon.py --nickname [yournick] --domain [name] --follow othernick@domain --password [c2s password]

The password is for the client to obtain access to the server.

You may or may not need to use the --port, --https and --tor options, depending upon how your server was set up.

Unfollowing is silimar:

python3 epicyon.py --nickname [yournick] --domain [name] --unfollow othernick@domain --password [c2s password]

Culling follower numbers

In this system the number of followers which an account has will only be visible to the account holder. Other viewers will see a made up number. Which accounts are followed or followed by a person will also only have limited visibility.

The intention is to prevent the construction of detailed social graphs by adversaries, and to frustrate attempts to build celebrity status based on number of followers, which on sites like Twitter creates a dubious economy of fake accounts and the trading thereof.

If you are the account holder though you will be able to see exactly who you're following or being followed by.

Sending posts

To make a public post:

python3 epicyon.py --nickname [yournick] --domain [name] \
                   --sendto public --message "hello" \
		   --warning "This is a content warning" \
		   --password [c2s password]

To post to followers only:

python3 epicyon.py --nickname [yournick] --domain [name] \
                   --sendto followers --message "hello" \
		   --warning "This is a content warning" \
		   --password [c2s password]

To send a post to a particular address (direct message):

python3 epicyon.py --nickname [yournick] --domain [name] \
                   --sendto othernick@domain --message "hello" \
		   --warning "This is a content warning" \
		   --password [c2s password]

The password is the c2s password for your account.

You can also attach an image. It must be in png, jpg or gif format.

python3 epicyon.py --nickname [yournick] --domain [name] \
                   --sendto othernick@domain --message "bees!" \
		   --warning "bee-related content" --attach bees.png \
		   --imagedescription "bees on flowers" \
		   --blurhash \
		   --password [c2s password]

Viewing Public Posts

To view the public posts for a person:

python3 epicyon.py --posts nickname@domain

If you want to view the raw json:

python3 epicyon.py --postsraw nickname@domain

Delete posts

To delete a post which you wrote you must first know its url. It is usually something like:

https://yourDomain/users/yourNickname/statuses/number

Once you know that they you can use the command:

python3 epicyon.py --nickname [yournick] --domain [name] \
                   --delete [url] --password [c2s password]

Deletion of posts in a federated system is not always reliable. Some instances may not implement deletion, and this may be because of the possibility of spurious deletes being sent by an adversary to cause trouble.

By default federated deletions are not permitted because of the potential for misuse. If you wish to enable it then set the option --allowdeletion.

Another complication of federated deletion is that the followers collection may change between the time when a post was created and the time it was deleted, leaving some stranded copies.

Announcements/repeats/boosts

To announce or repeat a post you will first need to know it's url. It is usually something like:

https://domain/users/name/statuses/number

Once you know that they you can use the command:

python3 epicyon.py --nickname [yournick] --domain [name] \
                   --repeat [url] --password [c2s password]

Like posts

To like a post you will first need to know it's url. It is usually something like:

https://domain/users/name/statuses/number

Once you know that they you can use the command:

python3 epicyon.py --nickname [yournick] --domain [name] \
                   --like [url] --password [c2s password]

To subsequently undo the like:

python3 epicyon.py --nickname [yournick] --domain [name] \
                   --undolike [url] --password [c2s password]

Archiving posts

You can archive old posts with:

python3 epicyon.py --archive [directory]

Which will move old posts to the given directory. You can also specify the number of weeks after which images will be archived, and the maximum number of posts within in/outboxes.

python3 epicyon.py --archive [directory] --archiveweeks 4 --maxposts 256

If you want old posts to be deleted for data minimization purposes then the archive location can be set to /dev/null.

python3 epicyon.py --archive /dev/null --archiveweeks 4 --maxposts 256

Blocking and unblocking

Whether you are using the --federate option to define a set of allowed instances or not, you may want to block particular accounts even inside of the perimeter. To block an account:

python3 epicyon.py --nickname yournick --domain yourdomain --block somenick@somedomain --password [c2s password]

This blocks at the earliest possble stage of receiving messages, such that nothing from the specified account will be written to your inbox.

Or to unblock:

python3 epicyon.py --nickname yournick --domain yourdomain --unblock somenick@somedomain --password [c2s password]

Filtering on words or phrases

Blocking based upon the content of a message containing certain words or phrases is relatively crude and not always effective, but can help to reduce unwanted communications.

To add a word or phrase to be filtered out:

python3 epicyon.py --nickname yournick --domain yourdomain --filter "this is a filtered phrase"

It can also be removed with:

python3 epicyon.py --nickname yournick --domain yourdomain --unfilter "this is a filtered phrase"

Like blocking, filters are per account and so different accounts on a server can have differing filter policies.

You can also combine words or phrases with "+", such that they can be present in different parts of the message:

python3 epicyon.py --nickname yournick --domain yourdomain --filter "blockedword+some other phrase"

Applying quotas

A common adversarial situation is that a hostile server tries to flood your shared inbox with posts in order to try to overload your system. To mitigate this it's possible to add quotas for the maximum number of received messages per domain per day and per account per day.

If you're running the server it would look like this:

python3 epicyon.py --domainmax 1000 --accountmax 200

With these settings you're going to be receiving no more than 200 messages for any given account within a day.

Delegated roles

Within an organization you may want to define different roles and for some projects to be delegated. By default the first account added to the system will be the admin, and be assigned moderator and delegator roles under a project called instance. The admin can then delegate a person to other projects with:

python3 epicyon.py --nickname [admin nickname] --domain [mydomain] \
                   --delegate [person nickname] \
		   --project [project name] --role [title] \
		   --password [c2s password]

The other person could also be made a delegator, but they will only be able to delegate further within projects which they're assigned to. By design, this creates a restricted organizational hierarchy. For example:

python3 epicyon.py --nickname [admin nickname] --domain [mydomain] \
                   --delegate [person nickname] \
		   --project [project name] --role delegator \
		   --password [c2s password]

A delegated role can also be removed.

python3 epicyon.py --nickname [admin nickname] --domain [mydomain] \
                   --undelegate [person nickname] \
		   --project [project name] \
		   --password [c2s password]

This extends the ActivityPub client-to-server protocol to include activities called Delegate and Role. The json looks like:

{ 'type': 'Delegate',
  'actor': https://somedomain/users/admin,
  'object': {
      'type': 'Role',
      'actor': https://'+somedomain+'/users/'+other,
      'object': 'otherproject;otherrole',
      'to': [],
      'cc': []            
  },
  'to': [],
  'cc': []}

Projects and roles are only scoped within a single instance. There presently are not enough security mechanisms to support multi-instance distributed organizations.

Assigning skills

To help create organizations you can assign some skills to your account. Note that you can only assign skills to yourself and not to other people. The command is:

python3 epicyon.py --nickname [nick] --domain [mydomain] \
                   --skill [tag] --level [0-100] \
		   --password [c2s password]

The level value is a percentage which indicates how proficient you are with that skill.

This extends the ActivityPub client-to-server protocol to include an activity called Skill. The json looks like:

{ 'type': 'Skill',
  'actor': https://somedomain/users/somenickname,
  'object': gardening;80,
  'to': [],
  'cc': []}

Setting availability status

For the purpose of things like knowing current task status or task completion a status value can be set.

python3 epicyon.py --nickname [nick] --domain [mydomain] \
                   --availability [status] \
		   --password [c2s password]

The status value can be any string, and can become part of organization building by combining it with roles and skills.

This extends the ActivityPub client-to-server protocol to include an activity called Availability. "Status" was avoided because of te possibility of confusion with other things. The json looks like:

{ 'type': 'Availability',
  'actor': https://somedomain/users/somenickname,
  'object': ready,
  'to': [],
  'cc': []}

Object Capabilities Security

A description of the proposed object capabilities model is here.