discourse/lib/final_destination/ssrf_detector.rb

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# frozen_string_literal: true
class FinalDestination
module SSRFDetector
class DisallowedIpError < SSRFError
end
class LookupFailedError < SSRFError
end
# This is a list of private IPv4 IP ranges that are not allowed to be globally reachable as given by
# https://www.iana.org/assignments/iana-ipv4-special-registry/iana-ipv4-special-registry.xhtml.
PRIVATE_IPV4_RANGES = [
IPAddr.new("0.0.0.0/8"),
IPAddr.new("10.0.0.0/8"),
IPAddr.new("100.64.0.0/10"),
IPAddr.new("127.0.0.0/8"),
IPAddr.new("169.254.0.0/16"),
IPAddr.new("172.16.0.0/12"),
IPAddr.new("192.0.0.0/24"),
IPAddr.new("192.0.0.0/29"),
IPAddr.new("192.0.0.8/32"),
IPAddr.new("192.0.0.170/32"),
IPAddr.new("192.0.0.171/32"),
IPAddr.new("192.0.2.0/24"),
IPAddr.new("192.168.0.0/16"),
IPAddr.new("192.175.48.0/24"),
IPAddr.new("198.18.0.0/15"),
IPAddr.new("198.51.100.0/24"),
IPAddr.new("203.0.113.0/24"),
IPAddr.new("240.0.0.0/4"),
IPAddr.new("255.255.255.255/32"),
]
# This is a list of private IPv6 IP ranges that are not allowed to be globally reachable as given by
# https://www.iana.org/assignments/iana-ipv6-special-registry/iana-ipv6-special-registry.xhtml.
#
# ::ffff:0:0/96 is excluded from the list because it is used for IPv4-mapped IPv6 addresses which is something we want to allow.
PRIVATE_IPV6_RANGES = [
IPAddr.new("::1/128"),
IPAddr.new("::/128"),
IPAddr.new("64:ff9b:1::/48"),
IPAddr.new("100::/64"),
IPAddr.new("2001::/23"),
IPAddr.new("2001:2::/48"),
IPAddr.new("2001:db8::/32"),
IPAddr.new("fc00::/7"),
IPAddr.new("fe80::/10"),
]
PRIVATE_IP_RANGES = PRIVATE_IPV4_RANGES + PRIVATE_IPV6_RANGES
def self.blocked_ip_blocks
SiteSetting
.blocked_ip_blocks
.split(/[|\n]/)
.filter_map do |r|
IPAddr.new(r.strip)
rescue IPAddr::InvalidAddressError
nil
end
end
def self.allowed_internal_hosts
hosts =
[
SiteSetting.Upload.s3_cdn_url,
GlobalSetting.try(:cdn_url),
Discourse.base_url_no_prefix,
].filter_map do |url|
URI.parse(url).hostname if url
rescue URI::Error
nil
end
hosts += SiteSetting.allowed_internal_hosts.split(/[|\n]/).filter_map { |h| h.strip.presence }
hosts
end
def self.host_bypasses_checks?(hostname)
allowed_internal_hosts.any? { |h| h.downcase == hostname.downcase }
end
def self.ip_allowed?(ip)
ip = ip.is_a?(IPAddr) ? ip : IPAddr.new(ip)
ip = ip.native
return false if ip_in_ranges?(ip, blocked_ip_blocks) || ip_in_ranges?(ip, PRIVATE_IP_RANGES)
true
end
def self.lookup_and_filter_ips(name, timeout: nil)
begin
ips = lookup_ips(name, timeout: timeout)
rescue SocketError
raise LookupFailedError, "FinalDestination: lookup failed"
end
return ips if host_bypasses_checks?(name)
ips.filter! { |ip| FinalDestination::SSRFDetector.ip_allowed?(ip) }
raise DisallowedIpError, "FinalDestination: all resolved IPs were disallowed" if ips.empty?
ips
end
def self.allow_ip_lookups_in_test!
@allow_ip_lookups_in_test = true
end
def self.disallow_ip_lookups_in_test!
@allow_ip_lookups_in_test = false
end
private
def self.ip_in_ranges?(ip, ranges)
ranges.any? { |r| r === ip }
end
def self.lookup_ips(name, timeout: nil)
if Rails.env.test? && !@allow_ip_lookups_in_test
["1.2.3.4"]
else
FinalDestination::Resolver.lookup(name, timeout: timeout)
end
end
end
end