discourse/lib/final_destination.rb

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require 'socket'
require 'ipaddr'
require 'excon'
require 'rate_limiter'
require 'url_helper'
# Determine the final endpoint for a Web URI, following redirects
class FinalDestination
def self.clear_https_cache!(domain)
key = redis_https_key(domain)
$redis.without_namespace.del(key)
end
def self.cache_https_domain(domain)
key = redis_https_key(domain)
$redis.without_namespace.setex(key, "1", 1.day.to_i).present?
end
def self.is_https_domain?(domain)
key = redis_https_key(domain)
$redis.without_namespace.get(key).present?
end
def self.redis_https_key(domain)
"HTTPS_DOMAIN_#{domain}"
end
attr_reader :status, :cookie, :status_code, :ignored
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def initialize(url, opts = nil)
@url = url
@uri = uri(escape_url) if @url
@opts = opts || {}
@force_get_hosts = @opts[:force_get_hosts] || []
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@preserve_fragment_url_hosts = @opts[:preserve_fragment_url_hosts] || []
@opts[:max_redirects] ||= 5
@opts[:lookup_ip] ||= lambda { |host| FinalDestination.lookup_ip(host) }
@ignored = @opts[:ignore_hostnames] || []
ignore_redirects = [Discourse.base_url_no_prefix]
if @opts[:ignore_redirects]
ignore_redirects.concat(@opts[:ignore_redirects])
end
ignore_redirects.each do |ignore_redirect|
ignore_redirect = uri(ignore_redirect)
if ignore_redirect.present? && ignore_redirect.hostname
@ignored << ignore_redirect.hostname
end
end
@limit = @opts[:max_redirects]
@status = :ready
@http_verb = @force_get_hosts.any? { |host| hostname_matches?(host) } ? :get : :head
@cookie = nil
@limited_ips = []
@verbose = @opts[:verbose] || false
@timeout = @opts[:timeout] || nil
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@preserve_fragment_url = @preserve_fragment_url_hosts.any? { |host| hostname_matches?(host) }
end
def self.connection_timeout
20
end
def timeout
@timeout || FinalDestination.connection_timeout
end
def redirected?
@limit < @opts[:max_redirects]
end
def request_headers
result = {
"User-Agent" => "Mozilla/5.0 (Windows NT 6.2; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/58.0.3029.110 Safari/537.36",
"Accept" => "*/*",
"Host" => @uri.hostname
}
result['Cookie'] = @cookie if @cookie
result
end
def small_get(headers)
Net::HTTP.start(@uri.host, @uri.port, use_ssl: @uri.is_a?(URI::HTTPS)) do |http|
http.open_timeout = timeout
http.read_timeout = timeout
http.request_get(@uri.request_uri, headers)
end
end
# this is a new interface for simply getting
# N bytes accounting for all internal logic
def get(uri = @uri, redirects = @limit, extra_headers: {}, &blk)
raise "Must specify block" unless block_given?
if uri && uri.port == 80 && FinalDestination.is_https_domain?(uri.hostname)
uri.scheme = "https"
uri = URI(uri.to_s)
end
return nil unless validate_uri
result, (location, cookie) = safe_get(uri, &blk)
if result == :redirect && (redirects == 0 || !location)
return nil
end
if result == :redirect
old_port = uri.port
location = "#{uri.scheme}://#{uri.host}#{location}" if location[0] == "/"
uri = uri(location)
# https redirect, so just cache that whole new domain is https
if old_port == 80 && uri&.port == 443 && (URI::HTTPS === uri)
FinalDestination.cache_https_domain(uri.hostname)
end
return nil if !uri
extra = nil
extra = { 'Cookie' => cookie } if cookie
get(uri, redirects - 1, extra_headers: extra, &blk)
elsif result == :ok
uri.to_s
else
nil
end
end
def resolve
if @uri && @uri.port == 80 && FinalDestination.is_https_domain?(@uri.hostname)
@uri.scheme = "https"
@uri = URI(@uri.to_s)
end
if @limit < 0
@status = :too_many_redirects
log(:warn, "FinalDestination could not resolve URL (too many redirects): #{@uri}") if @verbose
return nil
end
unless validate_uri
log(:warn, "FinalDestination could not resolve URL (invalid URI): #{@uri}") if @verbose
return nil
end
@ignored.each do |host|
if @uri&.hostname&.match?(host)
@status = :resolved
return @uri
end
end
headers = request_headers
response = Excon.public_send(@http_verb,
@uri.to_s,
read_timeout: timeout,
headers: headers
)
location = nil
response_headers = nil
response_status = response.status.to_i
case response.status
when 200
@status = :resolved
return @uri
when 400, 405, 406, 409, 501
get_response = small_get(request_headers)
response_status = get_response.code.to_i
if response_status == 200
@status = :resolved
return @uri
end
response_headers = {}
if cookie_val = get_response.get_fields('set-cookie')
response_headers[:cookies] = cookie_val
end
if location_val = get_response.get_fields('location')
response_headers[:location] = location_val.join
end
end
unless response_headers
response_headers = {
cookies: response.data[:cookies] || response.headers[:"set-cookie"],
location: response.headers[:location]
}
end
if (300..399).include?(response_status)
location = response_headers[:location]
end
if cookies = response_headers[:cookies]
@cookie = Array.wrap(cookies).map { |c| c.split(';').first.strip }.join('; ')
end
if location
old_port = @uri.port
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location = "#{location}##{@uri.fragment}" if @preserve_fragment_url && @uri.fragment.present?
location = "#{@uri.scheme}://#{@uri.host}#{location}" if location[0] == "/"
@uri = uri(location)
@limit -= 1
# https redirect, so just cache that whole new domain is https
if old_port == 80 && @uri.port == 443 && (URI::HTTPS === @uri)
FinalDestination.cache_https_domain(@uri.hostname)
end
return resolve
end
# this is weird an exception seems better
@status = :failure
@status_code = response.status
log(:warn, "FinalDestination could not resolve URL (status #{response.status}): #{@uri}") if @verbose
nil
rescue Excon::Errors::Timeout
log(:warn, "FinalDestination could not resolve URL (timeout): #{@uri}") if @verbose
nil
end
def validate_uri
validate_uri_format && is_dest_valid?
end
def validate_uri_format
return false unless @uri
return false unless ['https', 'http'].include?(@uri.scheme)
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return false if @uri.scheme == 'http' && @uri.port != 80
return false if @uri.scheme == 'https' && @uri.port != 443
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# Disallow IP based crawling
(IPAddr.new(@uri.hostname) rescue nil).nil?
end
def hostname_matches?(url)
url = uri(url)
@uri && url.present? && @uri.hostname == url&.hostname
end
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def is_dest_valid?
return false unless @uri && @uri.host
# Whitelisted hosts
return true if hostname_matches?(SiteSetting.Upload.s3_cdn_url) ||
hostname_matches?(GlobalSetting.try(:cdn_url)) ||
hostname_matches?(Discourse.base_url_no_prefix)
if SiteSetting.whitelist_internal_hosts.present?
return true if SiteSetting.whitelist_internal_hosts.split("|").any? { |h| h.downcase == @uri.hostname.downcase }
end
address_s = @opts[:lookup_ip].call(@uri.hostname)
return false unless address_s
address = IPAddr.new(address_s)
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if private_ranges.any? { |r| r === address }
@status = :invalid_address
return false
end
# Rate limit how often this IP can be crawled
if !@opts[:skip_rate_limit] && !@limited_ips.include?(address)
@limited_ips << address
RateLimiter.new(nil, "crawl-destination-ip:#{address_s}", 1000, 1.hour).performed!
end
true
rescue RateLimiter::LimitExceeded
false
end
def escape_url
UrlHelper.escape_uri(
CGI.unescapeHTML(@url),
Regexp.new("[^#{URI::PATTERN::UNRESERVED}#{URI::PATTERN::RESERVED}#]")
)
end
def private_ranges
FinalDestination.standard_private_ranges +
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SiteSetting.blacklist_ip_blocks.split('|').map { |r| IPAddr.new(r) rescue nil }.compact
end
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def log(log_level, message)
return if @status_code == 404
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Rails.logger.public_send(
log_level,
"#{RailsMultisite::ConnectionManagement.current_db}: #{message}"
)
end
def self.standard_private_ranges
@private_ranges ||= [
IPAddr.new('0.0.0.0/8'),
IPAddr.new('127.0.0.1'),
IPAddr.new('172.16.0.0/12'),
IPAddr.new('192.168.0.0/16'),
IPAddr.new('10.0.0.0/8'),
IPAddr.new('fc00::/7')
]
end
def self.lookup_ip(host)
if Rails.env.test?
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"1.1.1.1"
else
IPSocket::getaddress(host)
end
rescue SocketError
nil
end
protected
def safe_get(uri)
result = nil
unsafe_close = false
safe_session(uri) do |http|
headers = request_headers.merge(
'Accept-Encoding' => 'gzip',
'Host' => uri.host
)
req = Net::HTTP::Get.new(uri.request_uri, headers)
http.request(req) do |resp|
if Net::HTTPRedirection === resp
result = :redirect, [resp['location'], resp['Set-Cookie']]
end
if Net::HTTPSuccess === resp
resp.decode_content = true
resp.read_body do |chunk|
read_next = true
catch(:done) do
if read_next
read_next = false
yield resp, chunk, uri
read_next = true
end
end
# no clean way of finishing abruptly cause
# response likes reading till the end
if !read_next
unsafe_close = true
http.finish
raise StandardError
end
end
result = :ok
else
catch(:done) do
yield resp, nil, nil
end
end
end
end
result
rescue StandardError
unsafe_close ? :ok : raise
end
def safe_session(uri)
Net::HTTP.start(uri.host, uri.port, use_ssl: (uri.scheme == "https")) do |http|
http.read_timeout = timeout
http.open_timeout = timeout
yield http
end
end
private
def uri(location)
begin
URI.parse(location)
rescue URI::Error
end
end
end