File

plugins/mod_http_errors.lua @ 12180:53e0ae770917

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.
author Jonas Schäfer <jonas@wielicki.name>
date Mon, 10 Jan 2022 18:23:54 +0100
parent 11820:0375ef78ed64
child 12977:74b9e05af71e
line wrap: on
line source

module:set_global();

local server = require "net.http.server";
local codes = require "net.http.codes";
local xml_escape = require "util.stanza".xml_escape;
local render = require "util.interpolation".new("%b{}", xml_escape);

local show_private = module:get_option_boolean("http_errors_detailed", false);
local always_serve = module:get_option_boolean("http_errors_always_show", true);
local default_message = { module:get_option_string("http_errors_default_message", "That's all I know.") };
local default_messages = {
	[400] = { "What kind of request do you call that??" };
	[403] = { "You're not allowed to do that." };
	[404] = { "Whatever you were looking for is not here. %";
		"Where did you put it?", "It's behind you.", "Keep looking." };
	[500] = { "% Check your error log for more info.";
		"Gremlins.", "It broke.", "Don't look at me." };
	["/"] = {
		"A study in simplicity.";
		"Better catch it!";
		"Don't just stand there, go after it!";
		"Well, say something, before it runs too far!";
		"Welcome to the world of XMPP!";
		"You can do anything in XMPP!"; -- "The only limit is XML.";
		"You can do anything with Prosody!"; -- the only limit is memory?
	};
};

local messages = setmetatable(module:get_option("http_errors_messages", {}), { __index = default_messages });

local html = [[
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>{title}</title>
<style>
body{margin-top:14%;text-align:center;background-color:#f8f8f8;font-family:sans-serif}
h1{font-size:xx-large}
p{font-size:x-large}
p.warning>span{font-size:large;background-color:yellow}
p.extra{font-size:large;font-family:courier}
@media(prefers-color-scheme:dark){
body{background-color:#161616;color:#eee}
p.warning>span{background-color:inherit;color:yellow}
}
</style>
</head>
<body>
<h1>{icon?{icon_raw!?}} {title}</h1>
<p>{message}</p>
{warning&<p class="warning"><span>&#9888; {warning?} &#9888;</span></p>}
{extra&<p class="extra">{extra?}</p>}
</body>
</html>
]];

local function get_page(code, extra)
	local message = messages[code];
	if always_serve or message then
		message = message or default_message;
		return render(html, {
			title = rawget(codes, code) or ("Code "..tostring(code));
			message = message[1]:gsub("%%", function ()
				return message[math.random(2, math.max(#message,2))];
			end);
			extra = extra;
		});
	end
end

-- Main error page handler
module:hook_object_event(server, "http-error", function (event)
	if event.response then
		event.response.headers.content_type = "text/html; charset=utf-8";
	end
	return get_page(event.code, (show_private and event.private_message) or event.message or (event.error and event.error.text));
end);

-- Way to use the template for other things so to give a consistent appearance
module:hook("http-message", function (event)
	if event.response then
		event.response.headers.content_type = "text/html; charset=utf-8";
	end
	return render(html, event);
end, -1);

local icon = [[
<svg xmlns="http://www.w3.org/2000/svg" height="0.7em" viewBox="0 0 480 480" width="0.7em">
<rect fill="#6197df" height="220" rx="60" ry="60" width="220" x="10" y="10"></rect>
<rect fill="#f29b00" height="220" rx="60" ry="60" width="220" x="10" y="240"></rect>
<rect fill="#f29b00" height="220" rx="60" ry="60" width="220" x="240" y="10"></rect>
<rect fill="#6197df" height="220" rx="60" ry="60" width="220" x="240" y="240"></rect>
</svg>
]];

-- Something nicer shown instead of 404 at the root path, if nothing else handles this path
module:hook_object_event(server, "http-error", function (event)
	local request, response = event.request, event.response;
	if request and response and request.path == "/" and response.status_code == 404 then
		response.status_code = 200;
		response.headers.content_type = "text/html; charset=utf-8";
		local message = messages["/"];
		return render(html, {
				icon_raw = icon,
				title = "Prosody is running!";
				message = message[math.random(#message)];
			});
	end
end, 1);