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
-- Copyright (C) 2010 Jeff Mitchell
--
-- This project is MIT/X11 licensed. Please see the
-- COPYING file in the source package for more information.
--
local max = math.max;
local getAuthenticationDatabaseSHA1 = require "util.sasl.scram".getAuthenticationDatabaseSHA1;
local usermanager = require "core.usermanager";
local generate_uuid = require "util.uuid".generate;
local new_sasl = require "util.sasl".new;
local hex = require"util.hex";
local to_hex, from_hex = hex.to, hex.from;
local saslprep = require "util.encodings".stringprep.saslprep;
local secure_equals = require "util.hashes".equals;
local log = module._log;
local host = module.host;
local accounts = module:open_store("accounts");
-- Default; can be set per-user
local default_iteration_count = 4096;
-- define auth provider
local provider = {};
function provider.test_password(username, password)
log("debug", "test password for user '%s'", username);
local credentials = accounts:get(username) or {};
password = saslprep(password);
if not password then
return nil, "Password fails SASLprep.";
end
if credentials.password ~= nil and string.len(credentials.password) ~= 0 then
if not secure_equals(saslprep(credentials.password), password) then
return nil, "Auth failed. Provided password is incorrect.";
end
if provider.set_password(username, credentials.password) == nil then
return nil, "Auth failed. Could not set hashed password from plaintext.";
else
return true;
end
end
if credentials.iteration_count == nil or credentials.salt == nil or string.len(credentials.salt) == 0 then
return nil, "Auth failed. Stored salt and iteration count information is not complete.";
end
local valid, stored_key, server_key = getAuthenticationDatabaseSHA1(password, credentials.salt, credentials.iteration_count);
local stored_key_hex = to_hex(stored_key);
local server_key_hex = to_hex(server_key);
if valid and secure_equals(stored_key_hex, credentials.stored_key) and secure_equals(server_key_hex, credentials.server_key) then
return true;
else
return nil, "Auth failed. Invalid username, password, or password hash information.";
end
end
function provider.set_password(username, password)
log("debug", "set_password for username '%s'", username);
local account = accounts:get(username);
if account then
account.salt = generate_uuid();
account.iteration_count = max(account.iteration_count or 0, default_iteration_count);
local valid, stored_key, server_key = getAuthenticationDatabaseSHA1(password, account.salt, account.iteration_count);
if not valid then
return valid, stored_key;
end
local stored_key_hex = to_hex(stored_key);
local server_key_hex = to_hex(server_key);
account.stored_key = stored_key_hex
account.server_key = server_key_hex
account.password = nil;
return accounts:set(username, account);
end
return nil, "Account not available.";
end
function provider.user_exists(username)
local account = accounts:get(username);
if not account then
log("debug", "account not found for username '%s'", username);
return nil, "Auth failed. Invalid username";
end
return true;
end
function provider.users()
return accounts:users();
end
function provider.create_user(username, password)
if password == nil then
return accounts:set(username, {});
end
local salt = generate_uuid();
local valid, stored_key, server_key = getAuthenticationDatabaseSHA1(password, salt, default_iteration_count);
if not valid then
return valid, stored_key;
end
local stored_key_hex = to_hex(stored_key);
local server_key_hex = to_hex(server_key);
return accounts:set(username, {
stored_key = stored_key_hex, server_key = server_key_hex,
salt = salt, iteration_count = default_iteration_count
});
end
function provider.delete_user(username)
return accounts:set(username, nil);
end
function provider.get_sasl_handler()
local testpass_authentication_profile = {
plain_test = function(_, username, password, realm)
return usermanager.test_password(username, realm, password), true;
end,
scram_sha_1 = function(_, username)
local credentials = accounts:get(username);
if not credentials then return; end
if credentials.password then
if provider.set_password(username, credentials.password) == nil then
return nil, "Auth failed. Could not set hashed password from plaintext.";
end
credentials = accounts:get(username);
if not credentials then return; end
end
local stored_key, server_key = credentials.stored_key, credentials.server_key;
local iteration_count, salt = credentials.iteration_count, credentials.salt;
stored_key = stored_key and from_hex(stored_key);
server_key = server_key and from_hex(server_key);
return stored_key, server_key, iteration_count, salt, true;
end
};
return new_sasl(host, testpass_authentication_profile);
end
module:provides("auth", provider);