path: root/activitypub.rb

# TODO
# server
# fix failed follows
# federation
# boost
# thread expansion
# include own posts in threads
# implement remaining activities
# test with pleroma etc

# client
# post form
# parse hashtags in post
# client post media
require 'uri'
require 'base64'
require 'digest/sha2'
require 'sinatra'

USER = "pdp8"
WWW_DOMAIN = "pdp8.info"
WWW_URL = "https://#{WWW_DOMAIN}"
SOCIAL_DOMAIN = "social.#{WWW_DOMAIN}"

ACCOUNT = "#{USER}@#{SOCIAL_DOMAIN}"
SOCIAL_URL = "https://#{SOCIAL_DOMAIN}"
ACTOR = File.join(SOCIAL_URL, USER)

enable :sessions
set :session_secret, File.read(".secret").chomp
set :default_content_type, 'application/ld+json; profile="https://www.w3.org/ns/activitystreams"'
set :port, 9292

# server-server
post "/inbox" do 
  verify!
  request.body.rewind # in case someone already read it
  body = request.body.read
  action = JSON.parse body

  case action["type"]

  when "Create"
    create action["object"]

  when "Delete"
    delete action["object"]

  when "Update"
    delete action["object"]
    create action["object"]

  when "Follow"
    File.open(File.join("public", "followers", mention(action["actor"]) + ".json"), "w+") { |f| f.puts body }
    accept = { "@context" => "https://www.w3.org/ns/activitystreams",
               "id" => File.join(SOCIAL_URL + "#accepts", SecureRandom.uuid),
               "type" => "Accept",
               "actor" => ACTOR,
               "object" => action }
    send_signed accept, action["actor"]

  when "Undo"
    o = action["object"]
    case o["type"]
    when "Follow"
      Dir["public/followers/*.json"].each do |follower|
        FileUtils.rm follower if JSON.parse(File.read(follower))["actor"] == o["actor"]
      end
    end

  when "Accept"
    o = action["object"]
    case o["type"]
    when "Follow"
      File.open(File.join("public","following",mention(o['object'])+".json"),"w+"){|f| f.puts o.to_json}
    end

  #when "Announce"
  #when "Move"
  #when "Add"
  #when "Remove"
  #when "Like"
  #when "Block"

  else
    p "Unknown action: #{action['type']}"
    p body
  end
end

# client-server
post "/outbox" do 
  protected!
  request.body.rewind # in case someone already read it
  body = request.body.read
  date = Time.now.strftime("%Y-%m-%dT%H:%M:%S")
  # TODO hashtags, replys
  outbox_path = File.join("public/outbox", date + ".json")
  object_path = File.join("public/objects", date + ".json")
  create = {
    "@context" => "https://www.w3.org/ns/activitystreams",
    "id" => File.join(SOCIAL_URL, outbox_path),
    "type" => "Create",
    "actor" => ACTOR,
    "object" => {
      "id" => File.join(SOCIAL_URL, object_path),
      "type" => "Note",
      "attributedTo" => ACTOR,
      "published" => date,
      "content" => "",
      "to" => ["https://www.w3.org/ns/activitystreams#Public"]
    },
    "published" => date,
    "to" => ["https://www.w3.org/ns/activitystreams#Public"]
  }
  recipients = []
  if /^@/.match body
    mentions, body = body.split("\n", 2)
    mentions.split(/, */).each do |m|
      recipients << actor(m.chomp)
    end
  end
  create["object"]["content"] = body.lines.select { |l| !l.empty? }.join("<br>")
  recipients += Dir[File.join("public/followers", "*.json")].collect { |f| JSON.parse(File.read(f))["actor"] }
  recipients.delete ACTOR
  recipients.uniq!
  create["object"]["to"] += recipients
  create["to"] += recipients

  File.open(outbox_path, "w+") { |f| f.puts create.to_json }
  File.open(object_path, "w+") { |f| f.puts create["object"].to_json }

  recipients.each { |r| send_signed create, r }
end

post "/archive" do
  protected!
  FileUtils.mv params['file'], "archive/"
  redirect to(params['redirect'])
end

post "/delete" do
  protected!
  FileUtils.rm params['file']
  redirect to(params['redirect'])
end

post "/delete_all" do
  protected!
  FileUtils.rm Dir["inbox/*.json"]
  redirect to("/")
end

post "/follow/*/*" do
  protected!
  mention = params['splat'][0]
  actor = actor(mention)
  follow = { "@context" => "https://www.w3.org/ns/activitystreams",
             "id" => File.join(SOCIAL_URL, "following", mention + ".json"),
             "type" => "Follow",
             "actor" => ACTOR,
             "object" => actor }
  send_signed follow, actor
  redirect to("/")
end

post "/unfollow/*" do
  protected!
  mention = params['splat'][0]
  actor = actor(mention)
  following_path = File.join("public", "following", mention + ".json")
  if File.exists?(following_path)
    undo = { "@context" => "https://www.w3.org/ns/activitystreams",
             "id" => File.join(SOCIAL_URL + "#undo", SecureRandom.uuid),
             "type" => "Undo",
             "actor" => ACTOR,
             "object" => JSON.parse(File.read(following_path)) }
    send_signed undo, actor
    FileUtils.rm following_path
    redirect to("/")
  end
end

post "/login" do
  session["client"] = true if params["secret"] == File.read(".pwd").chomp
  redirect to("/")
end

# public
get "/.well-known/webfinger" do
  if request["resource"] == "acct:#{ACCOUNT}"
    send_file "./public/webfinger", :type => "application/jrd+json"
  else
    halt 404
  end
end

get "/pdp8", :provides => 'html' do
 redirect 'https://pdp8.info'
end

get "/pdp8" do
  send_file "pdp8.json", :type => 'application/ld+json; profile="https://www.w3.org/ns/activitystreams"'
end

["/outbox","/following","/followers"].each do |path|
  get path do 
    ordered_collection(path).to_json
  end
end

# private
["/", "/archive"].each do |path|
  get path, :provides => 'html' do
    protected!
    if path == '/' 
      @dir = 'inbox' 
      @alt_dir = '/archive' 
      @alt_name = 'archive'
    else
      @dir = path.sub('/','')
      @alt_dir = '/'
      @alt_name = 'inbox'
    end
    threads
    erb :index
  end
end

helpers do

  def protected!
    redirect("/login.html") unless session['client']
  end

  def verify!
    # https://github.com/mastodon/mastodon/blob/main/app/controllers/concerns/signature_verification.rb
    # TODO verify digest
    begin
      signature_params = {}
      request.env["HTTP_SIGNATURE"].split(',').each do |pair|
        k, v = pair.split('=')
        signature_params[k] = v.gsub('"', '')
      end

      key_id = signature_params['keyId']
      headers = signature_params['headers']
      signature = Base64.decode64(signature_params['signature'])

      actor = fetch key_id
      key = OpenSSL::PKey::RSA.new(actor['publicKey']['publicKeyPem'])

      comparison = headers.split(' ').map do |signed_params_name|
        if signed_params_name == '(request-target)'
          '(request-target): post /inbox'
        elsif signed_params_name == 'content-type'
          "#{signed_params_name}: #{request.env["CONTENT_TYPE"]}"
        else
          "#{signed_params_name}: #{request.env["HTTP_" + signed_params_name.upcase]}"
        end
      end.join("\n")

      halt 400 unless key.verify(OpenSSL::Digest.new('SHA256'), signature, comparison)
    rescue => e
      p request.env["HTTP_SIGNATURE"], e
      halt 400
    end
  end

  def threads
    nr = 0
    items = Dir[File.join(@dir, '*.json')].sort.collect do |file|
      item = JSON.parse(File.read(file))
      mention = mention(item['attributedTo'])
      following_path = File.join('public', 'following', mention + '.json')
      File.exists?(following_path) ? follow = 'unfollow' : follow = 'follow'
      nr += 1
      { :id => item['id'],
        :nr => nr,
        :parent => item['inReplyTo'],
        :file => file,
        :actor_url => item['attributedTo'],
        :mention => mention,
        :follow => follow,
        :content => item['content'],
        :attachment => item['attachment'],
        :indent => 2,
        :replies => []
      }
    end.compact
    items.last[:nr] = items.last[:nr] - 2
    @threads = []
    items.each do |i|
      if i[:parent].nil? or items.select{|it| it[:id] == i[:parent] }.empty?
        @threads << i
      else
        items.select{|it| it[:id] == i[:parent] }.each do |it|
          i[:indent] = it[:indent] + 2
          it[:replies] << i
        end
      end
    end
  end

  def html item
    @item = item
    erb :item
  end

  def delete object
    Dir["inbox/*.json"].each do |doc|
      FileUtils.rm doc if JSON.parse(File.read(doc))["id"] == object["id"]
    end
  end

  def create object
    unless object['type'] == 'Person'
      doc = File.join("inbox", "#{Time.now.strftime('%Y-%m-%dT%H:%M:%S.%N')}.json")
      File.open(doc, "w+") { |f| f.puts object.to_json }
    end
  end

  def people
    File.read('inbox/people.tsv').split("\n").collect {|l| l.chomp.split("\t")}
  end

  def mention actor
    person = people.select{|p| p[1] == actor} 
    if person.empty?
      mention = "#{fetch(actor)["preferredUsername"]}@#{URI(actor).host}"
      File.open('inbox/people.tsv','a'){|f| f.puts "#{mention}\t#{actor}"}
      mention
    else
      person[0][0]
    end
  end

  def actor mention
    mention = mention.sub(/^@/, '').chomp
    actors = people.select{|p| p[0] == mention} 
    if actors.empty?
      user, server = mention.split("@")
      actor = fetch("https://#{server}/.well-known/webfinger?resource=acct:#{mention}",
          "application/jrd+json")["links"].select { |l|
        l["rel"] == "self"
      }[0]["href"]
      File.open('inbox/people.tsv','a'){|f| f.puts "#{mention}\t#{actor}"}
      actor
    else
      actors[0][0]
    end
  end

  def fetch url, accept = 'application/ld+json; profile="https://www.w3.org/ns/activitystreams"'
    p url
    response = `/run/current-system/sw/bin/curl --fail-with-body -sSL -H 'Accept: #{accept}' #{url}`
    halt 400 unless $?.success?
    JSON.parse(response)
  end

  def ordered_collection dir
    posts = Dir[File.join("public",dir, "*.json")].collect { |f| JSON.parse(File.read f) }.sort_by { |o| o["published"] }
    {
      "@context" => "https://www.w3.org/ns/activitystreams",
      "summary" => "#{USER} #{dir}",
      "type" => "OrderedCollection",
      "totalItems" => posts.size,
      "orderedItems" => posts,
    }
  end

  def send_signed object, url
    # https://github.com/mastodon/mastodon/blob/main/app/lib/request.rb
    keypair = OpenSSL::PKey::RSA.new(File.read('private.pem'))
    date = Time.now.utc.httpdate
    uri = URI.parse(url)

    sha256 = OpenSSL::Digest::SHA256.new
    body = object.to_json
    digest = "SHA-256=" + sha256.base64digest(body)

    signed_string = "(request-target): post #{fetch(uri)["inbox"]}\nhost: #{uri.host}\ndate: #{date}\ndigest: #{digest}\ncontent-type: application/activity+json"
    signature = Base64.strict_encode64(keypair.sign(OpenSSL::Digest.new('SHA256'), signed_string))
    signed_header = 'keyId="' + ACTOR + '#main-key",algorithm="rsa-sha256",headers="(request-target) host date digest content-type",signature="' + signature + '"'

    puts `/run/current-system/sw/bin/curl -i -X POST -H 'Content-Type: application/activity+json' -H 'Host: #{uri.host}' -H 'Date: #{date}' -H 'Digest: #{digest}' -H 'Signature: #{signed_header}' -d '#{body}' #{fetch(url)['inbox']}`
  end

end