instructure/canvas-lms · error · GoogleDrive::MasqueradingException

cannot show collaboration when masquerading

Error message

cannot show collaboration when masquerading

What it means

Guard in CollaborationsController#show: a user viewing a collaboration while masquerading (acting as another user, where @real_current_user differs) is blocked. Google integrations bind to the real user's identity/credentials, so opening the collaboration under a spoofed session would access or create documents as the wrong account.

Solutions

1. Stop masquerading (become yourself) before opening the collaboration
2. Access the collaboration directly from the Google/Office account of the masqueraded user if legitimately needed

When it happens

Trigger: Thrown at app/controllers/collaborations_controller.rb:223 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of instructure/canvas-lms@1c9f0bb801 (2026-09-15). Data as JSON: /api/errors/c74b05aa10268931. Report an issue: GitHub.

Appendix: source

Thrown at app/controllers/collaborations_controller.rb:223

                             .where(where_collaborators)
    end

    collaborations = Api.paginate(
      collaborations_query,
      self,
      url
    )

    render json: collaborations.map { |c| collaboration_json(c, @current_user, session) }
  end

  def show
    @collaboration = @context.collaborations.find(params[:id])
    if authorized_action(@collaboration, @current_user, :read)
      @collaboration.touch
      begin
        # error out when user tries to open a collaboration while masquerading
        raise GoogleDrive::MasqueradingException, "cannot show collaboration when masquerading" if logged_in_user != @current_user

        if @collaboration.valid_user?(@current_user)
          @collaboration.authorize_user(@current_user)
          log_asset_access(@collaboration, "collaborations", "other", "participate")
          url = if @collaboration.is_a? ExternalToolCollaboration
                  tool = Lti::ToolFinder.from_url(@collaboration.url, @context)
                  @collaboration.migrate_to_1_3_if_needed!(tool)
                  resource_link_lookup_uuid = @collaboration.resource_link_lookup_uuid if tool.use_1_3?

                  external_tool_launch_url(
                    @collaboration.url,
                    resource_link_lookup_uuid
                  )
                else
                  @collaboration.url
                end

          redirect_to url

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