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) 2008-2010 Matthew Wild
-- Copyright (C) 2008-2010 Waqas Hussain
--
-- This project is MIT/X11 licensed. Please see the
-- COPYING file in the source package for more information.
--
--
-- luacheck: ignore 213/i
local t_concat, t_insert = table.concat, table.insert;
local char, format = string.char, string.format;
local tonumber = tonumber;
local ipairs = ipairs;
local io_write = io.write;
local m_floor = math.floor;
local type = type;
local setmetatable = setmetatable;
local pairs = pairs;
local windows;
if os.getenv("WINDIR") then
windows = require "util.windows";
end
local orig_color = windows and windows.get_consolecolor and windows.get_consolecolor();
local _ENV = nil;
-- luacheck: std none
local stylemap = {
reset = 0; bright = 1, dim = 2, underscore = 4, blink = 5, reverse = 7, hidden = 8;
black = 30; red = 31; green = 32; yellow = 33; blue = 34; magenta = 35; cyan = 36; white = 37;
["black background"] = 40; ["red background"] = 41; ["green background"] = 42; ["yellow background"] = 43;
["blue background"] = 44; ["magenta background"] = 45; ["cyan background"] = 46; ["white background"] = 47;
bold = 1, dark = 2, underline = 4, underlined = 4, normal = 0;
}
local winstylemap = {
["0"] = orig_color, -- reset
["1"] = 7+8, -- bold
["1;33"] = 2+4+8, -- bold yellow
["1;31"] = 4+8 -- bold red
}
local cssmap = {
[1] = "font-weight: bold", [2] = "opacity: 0.5", [4] = "text-decoration: underline", [8] = "visibility: hidden",
[30] = "color:black", [31] = "color:red", [32]="color:green", [33]="color:#FFD700",
[34] = "color:blue", [35] = "color: magenta", [36] = "color:cyan", [37] = "color: white",
[40] = "background-color:black", [41] = "background-color:red", [42]="background-color:green",
[43]="background-color:yellow", [44] = "background-color:blue", [45] = "background-color: magenta",
[46] = "background-color:cyan", [47] = "background-color: white";
};
local fmt_string = char(0x1B).."[%sm%s"..char(0x1B).."[0m";
local function getstring(style, text)
if style then
return format(fmt_string, style, text);
else
return text;
end
end
local function gray(n)
return m_floor(n*3/32)+0xe8;
end
local function color(r,g,b)
if r == g and g == b then
return gray(r);
end
r = m_floor(r*3/128);
g = m_floor(g*3/128);
b = m_floor(b*3/128);
return 0x10 + ( r * 36 ) + ( g * 6 ) + ( b );
end
local function hex2rgb(hex)
local r = tonumber(hex:sub(1,2),16);
local g = tonumber(hex:sub(3,4),16);
local b = tonumber(hex:sub(5,6),16);
return r,g,b;
end
setmetatable(stylemap, { __index = function(_, style)
if type(style) == "string" and style:find("%x%x%x%x%x%x") == 1 then
local g = style:sub(7) == " background" and "48;5;" or "38;5;";
return g .. color(hex2rgb(style));
end
end } );
local csscolors = {
red = "ff0000"; fuchsia = "ff00ff"; green = "008000"; white = "ffffff";
lime = "00ff00"; yellow = "ffff00"; purple = "800080"; blue = "0000ff";
aqua = "00ffff"; olive = "808000"; black = "000000"; navy = "000080";
teal = "008080"; silver = "c0c0c0"; maroon = "800000"; gray = "808080";
}
for colorname, rgb in pairs(csscolors) do
stylemap[colorname] = stylemap[colorname] or stylemap[rgb];
colorname, rgb = colorname .. " background", rgb .. " background"
stylemap[colorname] = stylemap[colorname] or stylemap[rgb];
end
local function getstyle(...)
local styles, result = { ... }, {};
for i, style in ipairs(styles) do
style = stylemap[style];
if style then
t_insert(result, style);
end
end
return t_concat(result, ";");
end
local last = "0";
local function setstyle(style)
style = style or "0";
if style ~= last then
io_write("\27["..style.."m");
last = style;
end
end
if windows then
function setstyle(style)
style = style or "0";
if style ~= last then
windows.set_consolecolor(winstylemap[style] or orig_color);
last = style;
end
end
if not orig_color then
function setstyle() end
end
end
local function ansi2css(ansi_codes)
if ansi_codes == "0" then return "</span>"; end
local css = {};
for code in ansi_codes:gmatch("[^;]+") do
t_insert(css, cssmap[tonumber(code)]);
end
return "</span><span style='"..t_concat(css, ";").."'>";
end
local function tohtml(input)
return input:gsub("\027%[(.-)m", ansi2css);
end
return {
getstring = getstring;
getstyle = getstyle;
setstyle = setstyle;
tohtml = tohtml;
};