util.xml: Do not allow doctypes, comments or processing instructions
Yes. This is as bad as it sounds. CVE pending.
In Prosody itself, this only affects mod_websocket, which uses util.xml
to parse the <open/> frame, thus allowing unauthenticated remote DoS
using Billion Laughs. However, third-party modules using util.xml may
also be affected by this.
This commit installs handlers which disallow the use of doctype
declarations and processing instructions without any escape hatch. It,
by default, also introduces such a handler for comments, however, there
is a way to enable comments nontheless.
This is because util.xml is used to parse human-facing data, where
comments are generally a desirable feature, and also because comments
are generally harmless.
-- Prosody IM
-- Copyright (C) 2008-2011 Florian Zeitz
--
-- This project is MIT/X11 licensed. Please see the
-- COPYING file in the source package for more information.
--
local net = require "util.net";
local hex = require "util.hex";
local ip_methods = {};
local ip_mt = {
__index = function (ip, key)
local method = ip_methods[key];
if not method then return nil; end
local ret = method(ip);
ip[key] = ret;
return ret;
end,
__tostring = function (ip) return ip.addr; end,
__eq = function (ipA, ipB) return ipA.packed == ipB.packed; end
};
local hex2bits = {
["0"] = "0000", ["1"] = "0001", ["2"] = "0010", ["3"] = "0011",
["4"] = "0100", ["5"] = "0101", ["6"] = "0110", ["7"] = "0111",
["8"] = "1000", ["9"] = "1001", ["A"] = "1010", ["B"] = "1011",
["C"] = "1100", ["D"] = "1101", ["E"] = "1110", ["F"] = "1111",
};
local function new_ip(ipStr, proto)
local zone;
if (not proto or proto == "IPv6") and ipStr:find('%', 1, true) then
ipStr, zone = ipStr:match("^(.-)%%(.*)");
end
local packed, err = net.pton(ipStr);
if not packed then return packed, err end
if proto == "IPv6" and #packed ~= 16 then
return nil, "invalid-ipv6";
elseif proto == "IPv4" and #packed ~= 4 then
return nil, "invalid-ipv4";
elseif not proto then
if #packed == 16 then
proto = "IPv6";
elseif #packed == 4 then
proto = "IPv4";
else
return nil, "unknown protocol";
end
elseif proto ~= "IPv6" and proto ~= "IPv4" then
return nil, "invalid protocol";
end
return setmetatable({ addr = ipStr, packed = packed, proto = proto, zone = zone }, ip_mt);
end
function ip_methods:normal()
return net.ntop(self.packed);
end
function ip_methods.bits(ip)
return hex.to(ip.packed):upper():gsub(".", hex2bits);
end
function ip_methods.bits_full(ip)
if ip.proto == "IPv4" then
ip = ip.toV4mapped;
end
return ip.bits;
end
local match;
local function commonPrefixLength(ipA, ipB)
ipA, ipB = ipA.bits_full, ipB.bits_full;
for i = 1, 128 do
if ipA:sub(i,i) ~= ipB:sub(i,i) then
return i-1;
end
end
return 128;
end
-- Instantiate once
local loopback = new_ip("::1");
local loopback4 = new_ip("127.0.0.0");
local sixtofour = new_ip("2002::");
local teredo = new_ip("2001::");
local linklocal = new_ip("fe80::");
local linklocal4 = new_ip("169.254.0.0");
local uniquelocal = new_ip("fc00::");
local sitelocal = new_ip("fec0::");
local sixbone = new_ip("3ffe::");
local defaultunicast = new_ip("::");
local multicast = new_ip("ff00::");
local ipv6mapped = new_ip("::ffff:0:0");
local function v4scope(ip)
if match(ip, loopback4, 8) then
return 0x2;
elseif match(ip, linklocal4, 16) then
return 0x2;
else -- Global unicast
return 0xE;
end
end
local function v6scope(ip)
if ip == loopback then
return 0x2;
elseif match(ip, linklocal, 10) then
return 0x2;
elseif match(ip, sitelocal, 10) then
return 0x5;
elseif match(ip, multicast, 10) then
return ip.packed:byte(2) % 0x10;
else -- Global unicast
return 0xE;
end
end
local function label(ip)
if ip == loopback then
return 0;
elseif match(ip, sixtofour, 16) then
return 2;
elseif match(ip, teredo, 32) then
return 5;
elseif match(ip, uniquelocal, 7) then
return 13;
elseif match(ip, sitelocal, 10) then
return 11;
elseif match(ip, sixbone, 16) then
return 12;
elseif match(ip, defaultunicast, 96) then
return 3;
elseif match(ip, ipv6mapped, 96) then
return 4;
else
return 1;
end
end
local function precedence(ip)
if ip == loopback then
return 50;
elseif match(ip, sixtofour, 16) then
return 30;
elseif match(ip, teredo, 32) then
return 5;
elseif match(ip, uniquelocal, 7) then
return 3;
elseif match(ip, sitelocal, 10) then
return 1;
elseif match(ip, sixbone, 16) then
return 1;
elseif match(ip, defaultunicast, 96) then
return 1;
elseif match(ip, ipv6mapped, 96) then
return 35;
else
return 40;
end
end
function ip_methods:toV4mapped()
if self.proto ~= "IPv4" then return nil, "No IPv4 address" end
local value = new_ip("::ffff:" .. self.normal);
return value;
end
function ip_methods:label()
if self.proto == "IPv4" then
return label(self.toV4mapped);
else
return label(self);
end
end
function ip_methods:precedence()
if self.proto == "IPv4" then
return precedence(self.toV4mapped);
else
return precedence(self);
end
end
function ip_methods:scope()
if self.proto == "IPv4" then
return v4scope(self);
else
return v6scope(self);
end
end
local rfc1918_8 = new_ip("10.0.0.0");
local rfc1918_12 = new_ip("172.16.0.0");
local rfc1918_16 = new_ip("192.168.0.0");
local rfc6598 = new_ip("100.64.0.0");
function ip_methods:private()
local private = self.scope ~= 0xE;
if not private and self.proto == "IPv4" then
return match(self, rfc1918_8, 8) or match(self, rfc1918_12, 12) or match(self, rfc1918_16, 16) or match(self, rfc6598, 10);
end
return private;
end
local function parse_cidr(cidr)
local bits;
local ip_len = cidr:find("/", 1, true);
if ip_len then
bits = tonumber(cidr:sub(ip_len+1, -1));
cidr = cidr:sub(1, ip_len-1);
end
return new_ip(cidr), bits;
end
function match(ipA, ipB, bits)
if not bits or bits >= 128 or ipB.proto == "IPv4" and bits >= 32 then
return ipA == ipB;
elseif bits < 1 then
return true;
end
if ipA.proto ~= ipB.proto then
if ipA.proto == "IPv4" then
ipA = ipA.toV4mapped;
elseif ipB.proto == "IPv4" then
ipB = ipB.toV4mapped;
bits = bits + (128 - 32);
end
end
return ipA.bits:sub(1, bits) == ipB.bits:sub(1, bits);
end
return {
new_ip = new_ip,
commonPrefixLength = commonPrefixLength,
parse_cidr = parse_cidr,
match = match,
};