view mod_auth_imap/auth_imap/sasl_imap.lib.lua @ 5468:14b5446e22e1

mod_http_oauth2: Fix returning errors from response handlers This would either redirect the user back to the client along with the error code, or show the error HTML template. Previously this would just show some JSON to the user.
author Kim Alvefur <zash@zash.se>
date Thu, 18 May 2023 12:57:23 +0200
parents a106477f1a65
children
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-- Dovecot authentication backend for Prosody
--
-- Copyright (C) 2011 Kim Alvefur
--

local log = require "util.logger".init("sasl_imap");

local setmetatable = setmetatable;

local s_match = string.match;
local t_concat = table.concat;
local tostring, tonumber = tostring, tonumber;

local socket = require "socket"
local ssl = require "ssl"
local x509 = require "util.x509";
local base64 = require "util.encodings".base64;
local b64, unb64 = base64.encode, base64.decode;

local _M = {};

local method = {};
method.__index = method;

-- For extracting the username.
local mitm = {
	PLAIN = function(message)
		return s_match(message, "^[^%z]*%z([^%z]+)%z[^%z]+");
	end,
	["SCRAM-SHA-1"] = function(message)
		return s_match(message, "^[^,]+,[^,]*,n=([^,]*)");
	end,
	["DIGEST-MD5"] = function(message)
		return s_match(message, "username=\"([^\"]*)\"");
	end,
}

local function connect(host, port, ssl_params)
	port = tonumber(port) or (ssl_params and 993 or 143);
	log("debug", "connect() to %s:%s:%d", ssl_params and "ssl" or "tcp", host, tonumber(port));
	local conn = socket.tcp();

	-- Create a connection to imap socket
	log("debug", "connecting to imap at '%s:%d'", host, port);
	local ok, err = conn:connect(host, port);
	conn:settimeout(10);
	if not ok then
		log("error", "error connecting to imap at '%s:%d': %s", host, port, err);
		return false;
	end

	if ssl_params then
		-- Perform SSL handshake
		local ok, err = ssl.wrap(conn, ssl_params);
		if ok then
			conn = ok;
			ok, err = conn:dohandshake();
		end
		if not ok then
			log("error", "error initializing ssl connection to imap at '%s:%d': %s", host, port, err);
			conn:close();
			return false;
		end

		-- Verify certificate
		if ssl_params.verify then
			if not conn.getpeercertificate then
				log("error", "unable to verify certificate, newer LuaSec required: https://prosody.im/doc/depends#luasec");
				conn:close();
				return false;
			end
			if not x509.verify_identity(host, nil, conn:getpeercertificate()) then
				log("warn", "invalid certificate for imap service %s:%d, denying connection", host, port);
				return false;
			end
		end
	end

	-- Parse IMAP handshake
	local supported_mechs = {};
	local line = conn:receive("*l");
	if not line then
		return false;
	end
	log("debug", "imap greeting: '%s'", line);
	local caps = line:match("^%*%s+OK%s+(%b[])");
	if not caps or not caps:match("^%[CAPABILITY ") then
		conn:send("A CAPABILITY\r\n");
		line = conn:receive("*l");
		log("debug", "imap capabilities response: '%s'", line);
		caps = line:match("^%*%s+CAPABILITY%s+(.*)$");
		if not conn:receive("*l"):match("^A OK") then
			log("debug", "imap capabilities command failed")
			conn:close();
			return false;
		end
	elseif caps then
		caps = caps:sub(2,-2); -- Strip surrounding []
	end
	if caps then
		for cap in caps:gmatch("%S+") do
			log("debug", "Capability: %s", cap);
			local mech = cap:match("AUTH=(.*)");
			if mech then
				log("debug", "Supported SASL mechanism: %s", mech);
				supported_mechs[mech] = mitm[mech] and true or nil;
			end
		end
	end

	return conn, supported_mechs;
end

-- create a new SASL object which can be used to authenticate clients
function _M.new(realm, service_name, host, port, ssl_params, append_host)
	log("debug", "new(%q, %q, %q, %d)", realm or "", service_name or "", host or "", port or 0);
	local sasl_i = {
		realm = realm;
		service_name = service_name;
		_host = host;
		_port = port;
		_ssl_params = ssl_params;
		_append_host = append_host;
	};

	local conn, mechs = connect(host, port, ssl_params);
	if not conn then
		return nil, "Socket connection failure";
	end
	if append_host then
		mechs = { PLAIN = mechs.PLAIN };
	end
	sasl_i.conn, sasl_i.mechs = conn, mechs;
	return setmetatable(sasl_i, method);
end

-- get a fresh clone with the same realm and service name
function method:clean_clone()
	if self.conn then
		self.conn:close();
		self.conn = nil;
	end
	log("debug", "method:clean_clone()");
	return _M.new(self.realm, self.service_name, self._host, self._port, self._ssl_params, self._append_host)
end

-- get a list of possible SASL mechanisms to use
function method:mechanisms()
	log("debug", "method:mechanisms()");
	return self.mechs;
end

-- select a mechanism to use
function method:select(mechanism)
	log("debug", "method:select(%q)", mechanism);
	if not self.selected and self.mechs[mechanism] then
		self.tag = tostring({}):match("0x(%x*)$");
		self.selected = mechanism;
		local selectmsg = t_concat({ self.tag, "AUTHENTICATE", mechanism }, " ");
		log("debug", "Sending %d bytes: %q", #selectmsg, selectmsg);
		local ok, err = self.conn:send(selectmsg.."\r\n");
		if not ok then
			log("error", "Could not write to socket: %s", err);
			return "failure", "internal-server-error", err
		end
		local line, err = self.conn:receive("*l");
		if not line then
			log("error", "Could not read from socket: %s", err);
			return "failure", "internal-server-error", err
		end
		log("debug", "Received %d bytes: %q", #line, line);
		return line:match("^+")
	end
end

-- feed new messages to process into the library
function method:process(message)
	local username = mitm[self.selected](message);
	if username then self.username = username; end
	if self._append_host and self.selected == "PLAIN" then
		message = message:gsub("^([^%z]*%z[^%z]+)(%z[^%z]+)$", "%1@"..self.realm.."%2");
	end
	log("debug", "method:process(%d bytes): %q", #message, message:gsub("%z", "."));
	local ok, err = self.conn:send(b64(message).."\r\n");
	if not ok then
		log("error", "Could not write to socket: %s", err);
		return "failure", "internal-server-error", err
	end
	log("debug", "Sent %d bytes to socket", ok);
	local line, err = self.conn:receive("*l");
	if not line then
		log("error", "Could not read from socket: %s", err);
		return "failure", "internal-server-error", err
	end
	log("debug", "Received %d bytes from socket: %s", #line, line);

	while line and line:match("^%* ") do
		line = self.conn:receive("*l");
	end

	if line:match("^%+") and #line > 2 then
		local data = line:sub(3);
		data = data and unb64(data);
		return "challenge", unb64(data);
	elseif line:sub(1, #self.tag) == self.tag then
		local ok, rest = line:sub(#self.tag+1):match("(%w+)%s+(.*)");
		ok = ok:lower();
		log("debug", "%s: %s", ok, rest);
		if ok == "ok" then
			return "success"
		elseif ok == "no" then
			return "failure", "not-authorized", rest;
		end
	elseif line:match("^%* BYE") then
		local err = line:match("BYE%s*(.*)");
		return "failure", "not-authorized", err;
	end
end

return _M;