--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mod_client_management/README.md	Thu Mar 30 11:32:50 2023 +0100
@@ -0,0 +1,32 @@
+---
+labels:
+- Stage-Beta
+summary: "Manage clients with access to your account"
+rockspec:
+  dependencies:
+  - mod_sasl2_fast
+---
+
+This module allows a user to identify what currently has access to their
+account.
+
+This module depends on [mod_sasl2_fast] and mod_tokenauth (bundled with
+Prosody). Both will be automatically loaded if this module is loaded.
+
+## Configuration
+
+| Name                      | Description                                            | Default         |
+|---------------------------|--------------------------------------------------------|-----------------|
+| enforce_client_ids        | Only allow SASL2-compatible clients                    | `false`         |
+
+When `enforce_client_ids` is not enabled, the client listing may be less accurate due to legacy clients,
+which can only be tracked by their resource, which is public information, not necessarily unique to a
+client instance, and is also exposed to other XMPP entities the user communicates with.
+
+When `enforce_client_ids` is enabled, clients that don't support SASL2 and provide a client id will be
+denied access.
+
+## Compatibility
+
+Requires Prosody trunk (as of 2023-03-29). Not compatible with Prosody 0.12
+and earlier.

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mod_client_management/mod_client_management.lua	Thu Mar 30 11:32:50 2023 +0100
@@ -0,0 +1,270 @@
+local modulemanager = require "core.modulemanager";
+local usermanager = require "core.usermanager";
+
+local id = require "util.id";
+local jid = require "util.jid";
+local st = require "util.stanza";
+
+local strict = module:get_option_boolean("enforce_client_ids", false);
+
+local tokenauth = module:depends("tokenauth");
+local mod_fast = module:depends("sasl2_fast");
+
+local client_store = assert(module:open_store("clients", "keyval+"));
+--[[{
+	id = id;
+	first_seen =
+	last_seen =
+	user_agent = {
+		name =
+		os =
+	}
+--}]]
+
+local xmlns_sasl2 = "urn:xmpp:sasl:2";
+
+local function get_user_agent(sasl_handler, token_info)
+	local sasl_agent = sasl_handler and sasl_handler.user_agent;
+	local token_agent = token_info and token_info.data and token_info.data.oauth2_client;
+	if not (sasl_agent or token_agent) then return; end
+	return {
+		software = sasl_agent and sasl_agent.software or token_agent and token_agent.name or nil;
+		uri = token_agent and token_agent.uri or nil;
+		device = sasl_agent and sasl_agent.device or nil;
+	};
+end
+
+module:hook("sasl2/c2s/success", function (event)
+	local session = event.session;
+	local username, client_id = session.username, session.client_id;
+	local mechanism = session.sasl_handler.selected;
+	local token_info = session.sasl_handler.token_info;
+	local token_id = token_info and token_info.id or nil;
+
+	local now = os.time();
+	if client_id then -- SASL2, have client identifier
+		local is_new_client;
+
+		local client_state = client_store:get_key(username, client_id);
+		if not client_state then
+			is_new_client = true;
+			client_state = {
+				id = client_id;
+				first_seen = now;
+				user_agent = get_user_agent(session.sasl_handler, token_info);
+				full_jid = nil;
+				last_seen = nil;
+				mechanisms = {};
+			};
+		end
+		-- Update state
+		client_state.full_jid = session.full_jid;
+		client_state.last_seen = now;
+		client_state.mechanisms[mechanism] = now;
+		if session.sasl_handler.fast_auth then
+			client_state.fast_auth = now;
+		end
+		if token_id then
+			client_state.auth_token_id = token_id;
+		end
+		-- Store updated state
+		client_store:set_key(username, client_id, client_state);
+
+		if is_new_client then
+			module:fire_event("client_management/new-client", { client = client_state });
+		end
+	end
+end);
+
+local function find_client_by_resource(username, resource)
+	local full_jid = jid.join(username, module.host, resource);
+	local clients = client_store:get(username);
+	if not clients then return; end
+
+	for _, client_state in pairs(clients) do
+		if client_state.full_jid == full_jid then
+			return client_state;
+		end
+	end
+end
+
+module:hook("resource-bind", function (event)
+	local session = event.session;
+	if session.client_id then return; end
+	local is_new_client;
+	local client_state = find_client_by_resource(event.session.username, event.session.resource);
+	local now = os.time();
+	if not client_state then
+		is_new_client = true;
+		client_state = {
+			id = id.short();
+			first_seen = now;
+			user_agent = nil;
+			full_jid = nil;
+			last_seen = nil;
+			mechanisms = {};
+			legacy = true;
+		};
+	end
+
+	-- Update state
+	local legacy_info = session.client_management_info;
+	client_state.full_jid = session.full_jid;
+	client_state.last_seen = now;
+	client_state.mechanisms[legacy_info.mechanism] = now;
+	if legacy_info.fast_auth then
+		client_state.fast_auth = now;
+	end
+
+	local token_id = legacy_info.token_info and legacy_info.token_info.id;
+	if token_id then
+		client_state.auth_token_id = token_id;
+	end
+
+	-- Store updated state
+	client_store:set_key(session.username, client_state.id, client_state);
+
+	if is_new_client then
+		module:fire_event("client_management/new-client", { client = client_state });
+	end
+end);
+
+if strict then
+	module:hook_tag(xmlns_sasl2, "authenticate", function (session, auth)
+		local user_agent = auth:get_child("user-agent");
+		if not user_agent or not user_agent.attr.id then
+			local failure = st.stanza("failure", { xmlns = xmlns_sasl2 })
+				:tag("malformed-request", { xmlns = "urn:ietf:params:xml:ns:xmpp-sasl" }):up()
+				:text_tag("text", "Client identifier required but not supplied");
+			session.send(failure);
+			return true;
+		end
+	end, 500);
+
+	if modulemanager.get_modules_for_host(module.host):contains("saslauth") then
+		module:log("error", "mod_saslauth is enabled, but enforce_client_ids is enabled and will prevent it from working");
+	end
+
+	module:hook("stanza/urn:ietf:params:xml:ns:xmpp-sasl:auth", function (event)
+		-- Block legacy SASL, if for some reason it is being used (either mod_saslauth is loaded,
+		-- or clients try it without advertisement)
+		module:log("warn", "Blocking legacy SASL authentication because enforce_client_ids is enabled");
+		local failure = st.stanza("failure", { xmlns = xmlns_sasl2 })
+			:tag("malformed-request", { xmlns = "urn:ietf:params:xml:ns:xmpp-sasl" }):up()
+			:text_tag("text", "Legacy SASL authentication is not available on this server");
+		event.session.send(failure);
+		return true;
+	end);
+else
+	-- Legacy client compat code
+	module:hook("authentication-success", function (event)
+		local session = event.session;
+		if session.client_id then return; end -- SASL2 client
+
+		local sasl_handler = session.sasl_handler;
+		session.client_management_info = {
+			mechanism = sasl_handler.selected;
+			token_info = sasl_handler.token_info;
+			fast_auth = sasl_handler.fast_auth;
+		};
+	end);
+end
+
+local function is_password_mechanism(mech_name)
+	if mech_name == "OAUTHBEARER" then return false; end
+	if mech_name:match("^HT%-") then return false; end
+	return true;
+end
+
+local function is_client_active(client)
+	local username, host = jid.split(client.full_jid);
+	local account_info = usermanager.get_account_info(username, host);
+	local last_password_change = account_info and account_info.password_updated;
+
+	local status = {};
+
+	-- Check for an active token grant that has been previously used by this client
+	if client.auth_token_id then
+		local grant = tokenauth.get_grant_info(client.auth_token_id);
+		if grant then
+			status.active_grant = grant;
+		end
+	end
+
+	-- Check for active FAST tokens
+	if client.fast_auth then
+		if mod_fast.is_client_fast(username, client.id, last_password_change) then
+			status.active_fast = client.fast_auth;
+		end
+	end
+
+	-- Client has access if any password-based SASL mechanisms have been used since last password change
+	for mech, mech_last_used in pairs(client.mechanisms) do
+		if is_password_mechanism(mech) and mech_last_used >= last_password_change then
+			status.active_password = mech_last_used;
+		end
+	end
+
+	if prosody.full_sessions[client.full_jid] then
+		status.active_connected = true;
+	end
+
+	if next(status) == nil then
+		return nil;
+	end
+	return status;
+end
+
+-- Public API
+--luacheck: ignore 131
+function get_active_clients(username)
+	local clients = client_store:get(username);
+	local active_clients = {};
+	local used_grants = {};
+
+	-- Go through known clients, check whether they could possibly log in
+	for client_id, client in pairs(clients or {}) do --luacheck: ignore 213/client_id
+		local active = is_client_active(client);
+		if active then
+			client.type = "session";
+			client.active = active;
+			table.insert(active_clients, client);
+			if active.active_grant then
+				used_grants[active.active_grant.id] = true;
+			end
+		end
+	end
+
+	-- Next, account for any grants that have been issued, but never actually logged in
+	for grant_id, grant in pairs(tokenauth.get_user_grants(username) or {}) do
+		if not used_grants[grant_id] then -- exclude grants already accounted for
+			table.insert(active_clients, {
+				id = grant_id;
+				type = "access";
+				first_seen = grant.created;
+				last_seen = grant.accessed;
+				active = {
+					active_grant = grant;
+				};
+				user_agent = get_user_agent(nil, grant);
+			});
+		end
+	end
+
+	table.sort(active_clients, function (a, b)
+		if a.last_seen and b.last_seen then
+			return a.last_seen < b.last_seen;
+		elseif not (a.last_seen or b.last_seen) then
+			if a.first_seen and b.first_seen then
+				return a.first_seen < b.first_seen;
+			end
+		elseif b.last_seen then
+			return true;
+		elseif a.last_seen then
+			return false;
+		end
+		return a.id < b.id;
+	end);
+
+	return active_clients;
+end