view mod_cloud_notify_encrypted/mod_cloud_notify_encrypted.lua @ 5271:3a1df3adad0c

mod_http_oauth2: Allow user to decide which requested scopes to grant These should at the very least be shown to the user, so they can decide whether to grant them. Considered whether to filter the requested scopes down to actually understood scopes that would be granted, but decided that this was a bit complex for a first step, since role role selection and other kinds of scopes are mixed into the same field here.
author Kim Alvefur <zash@zash.se>
date Thu, 23 Mar 2023 16:28:08 +0100
parents 3b609eaf0db5
children 2b80188448d1
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local array = require "util.array";
local base64 = require "util.encodings".base64;
local valid_utf8 = require "util.encodings".utf8.valid;
local ciphers = require "openssl.cipher";
local jid = require "util.jid";
local json = require "util.json";
local random = require "util.random";
local set = require "util.set";
local st = require "util.stanza";

local xmlns_jmi = "urn:xmpp:jingle-message:0";
local xmlns_jingle_apps_rtp = "urn:xmpp:jingle:apps:rtp:1";
local xmlns_push = "urn:xmpp:push:0";
local xmlns_push_encrypt = "tigase:push:encrypt:0";
local xmlns_push_encrypt_aes_128_gcm = "tigase:push:encrypt:aes-128-gcm";
local xmlns_push_jingle = "tigase:push:jingle:0";

local function detect_stanza_encryption(stanza)
	local eme = stanza:get_child("encryption", "urn:xmpp:eme:0");
	if eme then return eme.attr.namespace or ""; end
	-- Fallback for legacy OMEMO clients without EME
	local omemo = stanza:get_child("encrypted", "eu.siacs.conversations.axolotl");
	if omemo then return "eu.siacs.conversations.axolotl"; end
end

-- https://xeps.tigase.net//docs/push-notifications/encrypt/#41-discovering-support
local function account_disco_info(event)
	event.reply:tag("feature", {var=xmlns_push_encrypt}):up();
	event.reply:tag("feature", {var=xmlns_push_encrypt_aes_128_gcm}):up();
	event.reply:tag("feature", {var=xmlns_push_jingle}):up();
end
module:hook("account-disco-info", account_disco_info);

function handle_register(event)
	local encrypt = event.stanza:get_child("enable", xmlns_push):get_child("encrypt", xmlns_push_encrypt);
	if not encrypt then return; end

	local algorithm = encrypt.attr.alg;
	if algorithm ~= "aes-128-gcm" then
		event.origin.send(st.error_reply(
			event.stanza, "modify", "feature-not-implemented", "Unknown encryption algorithm"
		));
		return false;
	end

	local key_base64 = encrypt:get_text();
	local key_binary = base64.decode(key_base64);
	if not key_binary or #key_binary ~= 16 then
		event.origin.send(st.error_reply(
			event.stanza, "modify", "bad-request", "Invalid encryption key"
		));
		return false;
	end

	module:log("debug", "Encrypted push notifications enabled");

	event.push_info.encryption = {
		algorithm = algorithm;
		key_base64 = key_base64;
	};
end

function handle_push(event)
	local encryption = event.push_info.encryption;
	if not encryption then
		module:log("debug", "Encryption not enabled for this notification");
		return;
	end

	if encryption.algorithm ~= "aes-128-gcm" then
		event.reason = "Unsupported encryption algorithm: "..tostring(encryption.algorithm);
		return true;
	end

	local push_summary = event.push_summary;

	local original_stanza = event.original_stanza;
	local is_encrypted_msg = detect_stanza_encryption(original_stanza);
	local body;
	if is_encrypted_msg then
		-- TODO: localization
		body = "You have received an encrypted message";
	else
		body = original_stanza:get_child_text("body");
		if body and #body > 255 then
			body = body:sub(1, 255);
			if not valid_utf8(body) then
				body = body:gsub("[\194-\244][\128-\191]*$", "");
			end
		end
	end

	local push_payload = {
		unread = tonumber(push_summary["message-count"]) or 1;
		sender = jid.bare(original_stanza.attr.from);
		message = body;
	};

	if original_stanza.name == "message" then
		if original_stanza.attr.type == "groupchat" then
			push_payload.type = "groupchat";
			push_payload.nickname = jid.resource(original_stanza.attr.from);
		elseif original_stanza.attr.type ~= "error" then
			local jmi_propose = original_stanza:get_child("propose", xmlns_jmi);
			if jmi_propose then
				push_payload.type = "call";
				push_payload.sid = jmi_propose.attr.id;
				local media_types = set.new();
				for description in jmi_propose:childtags("description", xmlns_jingle_apps_rtp) do
					local media_type = description.attr.media;
					if media_type then
						media_types:add(media_type);
					end
				end
				push_payload.media = array.collect(media_types:items());
				push_payload.sender = original_stanza.attr.from;
			else
				push_payload.type = "chat";
			end
		end
	elseif original_stanza.name == "presence"
	and original_stanza.attr.type == "subscribe" then
		push_payload.type = "subscribe";
	end

	local iv = random.bytes(12);
	local key_binary = base64.decode(encryption.key_base64);
	local push_json = json.encode(push_payload);

	-- FIXME: luaossl does not expose the EVP_CTRL_GCM_GET_TAG API, so we append 16 NUL bytes
	-- Siskin does not validate the tag anyway.
	local encrypted_payload = base64.encode(ciphers.new("AES-128-GCM"):encrypt(key_binary, iv):final(push_json)..string.rep("\0", 16));
	local encrypted_element = st.stanza("encrypted", { xmlns = xmlns_push_encrypt, iv = base64.encode(iv) })
		:text(encrypted_payload);
	if push_payload.type == "call" then
		encrypted_element.attr.type = "voip";
		event.important = true;
	end
	-- Replace the unencrypted notification data with the encrypted one
	event.notification_payload
		:remove_children("x", "jabber:x:data")
		:add_child(encrypted_element);

	module:log("debug", "Encrypted '%s' push notification using %s", push_payload.type, encryption.algorithm);
end

module:hook("cloud_notify/registration", handle_register);
module:hook("cloud_notify/push", handle_push, 1);