A lightly modified copy of Mastodon, the canonical repository for Chinwag Social's live code. https://social.chinwag.org/
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# frozen_string_literal: true
class Webfinger
class Error < StandardError; end
class GoneError < Error; end
class RedirectError < StandardError; end
class Response
def initialize(body)
@json = Oj.load(body, mode: :strict)
end
def subject
@json['subject']
end
def link(rel, attribute)
links.dig(rel, attribute)
end
private
def links
@links ||= @json['links'].map { |link| [link['rel'], link] }.to_h
end
end
def initialize(uri)
_, @domain = uri.split('@')
raise ArgumentError, 'Webfinger requested for local account' if @domain.nil?
@uri = uri
end
def perform
Response.new(body_from_webfinger)
rescue Oj::ParseError
raise Webfinger::Error, "Invalid JSON in response for #{@uri}"
rescue Addressable::URI::InvalidURIError
raise Webfinger::Error, "Invalid URI for #{@uri}"
end
private
def body_from_webfinger(url = standard_url, use_fallback = true)
webfinger_request(url).perform do |res|
if res.code == 200
res.body_with_limit
elsif res.code == 404 && use_fallback
body_from_host_meta
elsif res.code == 410
raise Webfinger::GoneError, "#{@uri} is gone from the server"
else
raise Webfinger::Error, "Request for #{@uri} returned HTTP #{res.code}"
end
end
end
def body_from_host_meta
host_meta_request.perform do |res|
if res.code == 200
body_from_webfinger(url_from_template(res.body_with_limit), false)
else
raise Webfinger::Error, "Request for #{@uri} returned HTTP #{res.code}"
end
end
end
def url_from_template(str)
link = Nokogiri::XML(str).at_xpath('//xmlns:Link[@rel="lrdd"]')
if link.present?
link['template'].gsub('{uri}', @uri)
else
raise Webfinger::Error, "Request for #{@uri} returned host-meta without link to Webfinger"
end
rescue Nokogiri::XML::XPath::SyntaxError
raise Webfinger::Error, "Invalid XML encountered in host-meta for #{@uri}"
end
def host_meta_request
Request.new(:get, host_meta_url).add_headers('Accept' => 'application/xrd+xml, application/xml, text/xml')
end
def webfinger_request(url)
Request.new(:get, url).add_headers('Accept' => 'application/jrd+json, application/json')
end
def standard_url
"https://#{@domain}/.well-known/webfinger?resource=#{@uri}"
end
def host_meta_url
"https://#{@domain}/.well-known/host-meta"
end
end