mastodon/app/lib/webfinger.rb
Claire 3517867b76
Fix confusing error when webfinger request returns empty document ()
For some reason, some misconfigured servers return an empty document when
queried over webfinger. Since an empty document does not lead to a parse
error, the error is not caught properly and triggers uncaught exceptions
later on.

This PR fixes that by immediately erroring out with `Webfinger::Error` on
getting an empty response.
2021-11-14 21:55:40 +01:00

107 lines
2.7 KiB
Ruby

# 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'].index_by { |link| link['rel'] }
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
body = res.body_with_limit
raise Webfinger::Error, "Request for #{@uri} returned empty response" if body.empty?
body
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
if @domain.end_with? ".onion"
"http://#{@domain}/.well-known/webfinger?resource=#{@uri}"
else
"https://#{@domain}/.well-known/webfinger?resource=#{@uri}"
end
end
def host_meta_url
if @domain.end_with? ".onion"
"http://#{@domain}/.well-known/host-meta"
else
"https://#{@domain}/.well-known/host-meta"
end
end
end