1 files changed, 105 insertions, 0 deletions
diff --git a/lib/mattermost/session.rb b/lib/mattermost/session.rb
new file mode 100644
index 00000000000..d14121c91a0
--- /dev/null
+++ b/lib/mattermost/session.rb
@@ -0,0 +1,105 @@
+module Mattermost
+  class NoSessionError < StandardError; end
+  # This class' prime objective is to obtain a session token on a Mattermost
+  # instance with SSO configured where this GitLab instance is the provider.
+  #
+  # The process depends on OAuth, but skips a step in the authentication cycle.
+  # For example, usually a user would click the 'login in GitLab' button on
+  # Mattermost, which would yield a 302 status code and redirects you to GitLab
+  # to approve the use of your account on Mattermost. Which would trigger a
+  # callback so Mattermost knows this request is approved and gets the required
+  # data to create the user account etc.
+  #
+  # This class however skips the button click, and also the approval phase to
+  # speed up the process and keep it without manual action and get a session
+  # going.
+  class Session
+    include Doorkeeper::Helpers::Controller
+    include HTTParty
+
+    attr_accessor :current_resource_owner
+
+    def initialize(uri, current_user)
+      # Sets the base uri for HTTParty, so we can use paths
+      self.class.base_uri(uri)
+
+      @current_resource_owner = current_user
+    end
+
+    def with_session
+      raise NoSessionError unless create
+      result = yield
+      destroy
+
+      result
+    end
+
+    # Next methods are needed for Doorkeeper
+    def pre_auth
+      @pre_auth ||= Doorkeeper::OAuth::PreAuthorization.new(
+        Doorkeeper.configuration, server.client_via_uid, params)
+    end
+
+    def authorization
+      @authorization ||= strategy.request
+    end
+
+    def strategy
+      @strategy ||= server.authorization_request(pre_auth.response_type)
+    end
+
+    def request
+      @request ||= OpenStruct.new(parameters: params)
+    end
+
+    def params
+      Rack::Utils.parse_query(@oauth_uri.query).symbolize_keys
+    end
+
+    private
+
+    def create
+      return unless oauth_uri
+      return unless token_uri
+
+      self.class.headers("Cookie" => "MMAUTHTOKEN=#{request_token}")
+
+      request_token
+    end
+
+    def destroy
+      post('/api/v3/users/logout')
+    end
+
+    def oauth_uri
+      response = get("/api/v3/oauth/gitlab/login", follow_redirects: false)
+      return unless 300 <= response.code && response.code < 400
+
+      redirect_uri = response.headers['location']
+      return unless redirect_uri
+
+      @oauth_uri ||= URI.parse(redirect_uri)
+    end
+
+    def token_uri
+      @token_uri ||= if @oauth_uri
+                       authorization.authorize.redirect_uri if pre_auth.authorizable?
+                     end
+    end
+
+    def request_token
+      @request_token ||= begin
+                           response = get(@token_uri, follow_redirects: false)
+                           response.headers['token'] if 200 <= response.code && response.code < 400
+                         end
+    end
+
+    def get(path, options = {})
+      self.class.get(path, options)
+    end
+
+    def post(path, options = {})
+      self.class.post(path, options)
+    end
+  end
+end