prosodyctl+util.prosodyctl.*: Start breaking up the ever-growing prosodyctl

3 files changed, 824 insertions, 1 deletions

diff --git a/util/prosodyctl/cert.lua b/util/prosodyctl/cert.lua
new file mode 100644
index 00000000..29e26ed8
--- /dev/null
+++ b/util/prosodyctl/cert.lua
@@ -0,0 +1,293 @@
+local lfs = require "lfs";
+
+local pctl = require "util.prosodyctl";
+local configmanager = require "core.configmanager";
+
+local openssl;
+
+local cert_commands = {};
+
+-- If a file already exists, ask if the user wants to use it or replace it
+-- Backups the old file if replaced
+local function use_existing(filename)
+	local attrs = lfs.attributes(filename);
+	if attrs then
+		if pctl.show_yesno(filename .. " exists, do you want to replace it? [y/n]") then
+			local backup = filename..".bkp~"..os.date("%FT%T", attrs.change);
+			os.rename(filename, backup);
+			pctl.show_message("%s backed up to %s", filename, backup);
+		else
+			-- Use the existing file
+			return true;
+		end
+	end
+end
+
+local have_pposix, pposix = pcall(require, "util.pposix");
+local cert_basedir = prosody.paths.data == "." and "./certs" or prosody.paths.data;
+if have_pposix and pposix.getuid() == 0 then
+	-- FIXME should be enough to check if this directory is writable
+	local cert_dir = configmanager.get("*", "certificates") or "certs";
+	cert_basedir = configmanager.resolve_relative_path(prosody.paths.config, cert_dir);
+end
+
+function cert_commands.config(arg)
+	if #arg >= 1 and arg[1] ~= "--help" then
+		local conf_filename = cert_basedir .. "/" .. arg[1] .. ".cnf";
+		if use_existing(conf_filename) then
+			return nil, conf_filename;
+		end
+		local distinguished_name;
+		if arg[#arg]:find("^/") then
+			distinguished_name = table.remove(arg);
+		end
+		local conf = openssl.config.new();
+		conf:from_prosody(prosody.hosts, configmanager, arg);
+		if distinguished_name then
+			local dn = {};
+			for k, v in distinguished_name:gmatch("/([^=/]+)=([^/]+)") do
+				table.insert(dn, k);
+				dn[k] = v;
+			end
+			conf.distinguished_name = dn;
+		else
+			pctl.show_message("Please provide details to include in the certificate config file.");
+			pctl.show_message("Leave the field empty to use the default value or '.' to exclude the field.")
+			for _, k in ipairs(openssl._DN_order) do
+				local v = conf.distinguished_name[k];
+				if v then
+					local nv = nil;
+					if k == "commonName" then
+						v = arg[1]
+					elseif k == "emailAddress" then
+						v = "xmpp@" .. arg[1];
+					elseif k == "countryName" then
+						local tld = arg[1]:match"%.([a-z]+)$";
+						if tld and #tld == 2 and tld ~= "uk" then
+							v = tld:upper();
+						end
+					end
+					nv = pctl.show_prompt(("%s (%s):"):format(k, nv or v));
+					nv = (not nv or nv == "") and v or nv;
+					if nv:find"[\192-\252][\128-\191]+" then
+						conf.req.string_mask = "utf8only"
+					end
+					conf.distinguished_name[k] = nv ~= "." and nv or nil;
+				end
+			end
+		end
+		local conf_file, err = io.open(conf_filename, "w");
+		if not conf_file then
+			pctl.show_warning("Could not open OpenSSL config file for writing");
+			pctl.show_warning(err);
+			os.exit(1);
+		end
+		conf_file:write(conf:serialize());
+		conf_file:close();
+		print("");
+		pctl.show_message("Config written to %s", conf_filename);
+		return nil, conf_filename;
+	else
+		pctl.show_usage("cert config HOSTNAME [HOSTNAME+]", "Builds a certificate config file covering the supplied hostname(s)")
+	end
+end
+
+function cert_commands.key(arg)
+	if #arg >= 1 and arg[1] ~= "--help" then
+		local key_filename = cert_basedir .. "/" .. arg[1] .. ".key";
+		if use_existing(key_filename) then
+			return nil, key_filename;
+		end
+		os.remove(key_filename); -- This file, if it exists is unlikely to have write permissions
+		local key_size = tonumber(arg[2] or pctl.show_prompt("Choose key size (2048):") or 2048);
+		local old_umask = pposix.umask("0377");
+		if openssl.genrsa{out=key_filename, key_size} then
+			os.execute(("chmod 400 '%s'"):format(key_filename));
+			pctl.show_message("Key written to %s", key_filename);
+			pposix.umask(old_umask);
+			return nil, key_filename;
+		end
+		pctl.show_message("There was a problem, see OpenSSL output");
+	else
+		pctl.show_usage("cert key HOSTNAME <bits>", "Generates a RSA key named HOSTNAME.key\n "
+		.."Prompts for a key size if none given")
+	end
+end
+
+function cert_commands.request(arg)
+	if #arg >= 1 and arg[1] ~= "--help" then
+		local req_filename = cert_basedir .. "/" .. arg[1] .. ".req";
+		if use_existing(req_filename) then
+			return nil, req_filename;
+		end
+		local _, key_filename = cert_commands.key({arg[1]});
+		local _, conf_filename = cert_commands.config(arg);
+		if openssl.req{new=true, key=key_filename, utf8=true, sha256=true, config=conf_filename, out=req_filename} then
+			pctl.show_message("Certificate request written to %s", req_filename);
+		else
+			pctl.show_message("There was a problem, see OpenSSL output");
+		end
+	else
+		pctl.show_usage("cert request HOSTNAME [HOSTNAME+]", "Generates a certificate request for the supplied hostname(s)")
+	end
+end
+
+function cert_commands.generate(arg)
+	if #arg >= 1 and arg[1] ~= "--help" then
+		local cert_filename = cert_basedir .. "/" .. arg[1] .. ".crt";
+		if use_existing(cert_filename) then
+			return nil, cert_filename;
+		end
+		local _, key_filename = cert_commands.key({arg[1]});
+		local _, conf_filename = cert_commands.config(arg);
+		if key_filename and conf_filename and cert_filename
+			and openssl.req{new=true, x509=true, nodes=true, key=key_filename,
+				days=365, sha256=true, utf8=true, config=conf_filename, out=cert_filename} then
+			pctl.show_message("Certificate written to %s", cert_filename);
+			print();
+		else
+			pctl.show_message("There was a problem, see OpenSSL output");
+		end
+	else
+		pctl.show_usage("cert generate HOSTNAME [HOSTNAME+]", "Generates a self-signed certificate for the current hostname(s)")
+	end
+end
+
+local function sh_esc(s)
+	return "'" .. s:gsub("'", "'\\''") .. "'";
+end
+
+local function copy(from, to, umask, owner, group)
+	local old_umask = umask and pposix.umask(umask);
+	local attrs = lfs.attributes(to);
+	if attrs then -- Move old file out of the way
+		local backup = to..".bkp~"..os.date("%FT%T", attrs.change);
+		os.rename(to, backup);
+	end
+	-- FIXME friendlier error handling, maybe move above backup back?
+	local input = assert(io.open(from));
+	local output = assert(io.open(to, "w"));
+	local data = input:read(2^11);
+	while data and output:write(data) do
+		data = input:read(2^11);
+	end
+	assert(input:close());
+	assert(output:close());
+	if not prosody.installed then
+		-- FIXME this is possibly specific to GNU chown
+		os.execute(("chown -c --reference=%s %s"):format(sh_esc(cert_basedir), sh_esc(to)));
+	elseif owner and group then
+		local ok = os.execute(("chown %s:%s %s"):format(sh_esc(owner), sh_esc(group), sh_esc(to)));
+		assert(ok == true or ok == 0, "Failed to change ownership of "..to);
+	end
+	if old_umask then pposix.umask(old_umask); end
+	return true;
+end
+
+function cert_commands.import(arg)
+	local hostnames = {};
+	-- Move hostname arguments out of arg, the rest should be a list of paths
+	while arg[1] and prosody.hosts[ arg[1] ] do
+		table.insert(hostnames, table.remove(arg, 1));
+	end
+	if hostnames[1] == nil then
+		local domains = os.getenv"RENEWED_DOMAINS"; -- Set if invoked via certbot
+		if domains then
+			for host in domains:gmatch("%S+") do
+				table.insert(hostnames, host);
+			end
+		else
+			for host in pairs(prosody.hosts) do
+				if host ~= "*" and configmanager.get(host, "enabled") ~= false then
+					table.insert(hostnames, host);
+				end
+			end
+		end
+	end
+	if not arg[1] or arg[1] == "--help" then -- Probably forgot the path
+		pctl.show_usage("cert import [HOSTNAME+] /path/to/certs [/other/paths/]+",
+			"Copies certificates to "..cert_basedir);
+		return 1;
+	end
+	local owner, group;
+	if pposix.getuid() == 0 then -- We need root to change ownership
+		owner = configmanager.get("*", "prosody_user") or "prosody";
+		group = configmanager.get("*", "prosody_group") or owner;
+	end
+	local cm = require "core.certmanager";
+	local imported = {};
+	for _, host in ipairs(hostnames) do
+		for _, dir in ipairs(arg) do
+			local paths = cm.find_cert(dir, host);
+			if paths then
+				copy(paths.certificate, cert_basedir .. "/" .. host .. ".crt", nil, owner, group);
+				copy(paths.key, cert_basedir .. "/" .. host .. ".key", "0377", owner, group);
+				table.insert(imported, host);
+			else
+				-- TODO Say where we looked
+				pctl.show_warning("No certificate for host "..host.." found :(");
+			end
+			-- TODO Additional checks
+			-- Certificate names matches the hostname
+			-- Private key matches public key in certificate
+		end
+	end
+	if imported[1] then
+		pctl.show_message("Imported certificate and key for hosts %s", table.concat(imported, ", "));
+		local ok, err = pctl.reload();
+		if not ok and err ~= "not-running" then
+			pctl.show_message(pctl.error_messages[err]);
+		end
+	else
+		pctl.show_warning("No certificates imported :(");
+		return 1;
+	end
+end
+
+local function cert(arg)
+	if #arg >= 1 and arg[1] ~= "--help" then
+		openssl = require "util.openssl";
+		lfs = require "lfs";
+		local cert_dir_attrs = lfs.attributes(cert_basedir);
+		if not cert_dir_attrs then
+			pctl.show_warning("The directory "..cert_basedir.." does not exist");
+			return 1; -- TODO Should we create it?
+		end
+		local uid = pposix.getuid();
+		if uid ~= 0 and uid ~= cert_dir_attrs.uid then
+			pctl.show_warning("The directory "..cert_basedir.." is not owned by the current user, won't be able to write files to it");
+			return 1;
+		elseif not cert_dir_attrs.permissions then -- COMPAT with LuaFilesystem < 1.6.2 (hey CentOS!)
+			pctl.show_message("Unable to check permissions on %s (LuaFilesystem 1.6.2+ required)", cert_basedir);
+			pctl.show_message("Please confirm that Prosody (and only Prosody) can write to this directory)");
+		elseif cert_dir_attrs.permissions:match("^%.w..%-..%-.$") then
+			pctl.show_warning("The directory "..cert_basedir.." not only writable by its owner");
+			return 1;
+		end
+		local subcmd = table.remove(arg, 1);
+		if type(cert_commands[subcmd]) == "function" then
+			if subcmd ~= "import" then -- hostnames are optional for import
+				if not arg[1] then
+					pctl.show_message"You need to supply at least one hostname"
+					arg = { "--help" };
+				end
+				if arg[1] ~= "--help" and not prosody.hosts[arg[1]] then
+					pctl.show_message(pctl.error_messages["no-such-host"]);
+					return 1;
+				end
+			end
+			return cert_commands[subcmd](arg);
+		elseif subcmd == "check" then
+			return require "util.prosodyctl.check".check({"certs"});
+		end
+	end
+	pctl.show_usage("cert config|request|generate|key|import", "Helpers for generating X.509 certificates and keys.")
+	for _, cmd in pairs(cert_commands) do
+		print()
+		cmd{ "--help" }
+	end
+end
+
+return {
+	cert = cert;
+};
diff --git a/util/prosodyctl/check.lua b/util/prosodyctl/check.lua
new file mode 100644
index 00000000..d22d5f45
--- /dev/null
+++ b/util/prosodyctl/check.lua
@@ -0,0 +1,530 @@
+local configmanager = require "core.configmanager";
+local show_usage = require "util.prosodyctl".show_usage;
+local show_warning = require "util.prosodyctl".show_warning;
+local dependencies = require "util.dependencies";
+local socket = require "socket";
+local jid_split = require "util.jid".prepped_split;
+local modulemanager = require "core.modulemanager";
+
+local function check(arg)
+	if arg[1] == "--help" then
+		show_usage([[check]], [[Perform basic checks on your Prosody installation]]);
+		return 1;
+	end
+	local what = table.remove(arg, 1);
+	local set = require "util.set";
+	local it = require "util.iterators";
+	local ok = true;
+	local function disabled_hosts(host, conf) return host ~= "*" and conf.enabled ~= false; end
+	local function enabled_hosts() return it.filter(disabled_hosts, pairs(configmanager.getconfig())); end
+	if not (what == nil or what == "disabled" or what == "config" or what == "dns" or what == "certs") then
+		show_warning("Don't know how to check '%s'. Try one of 'config', 'dns', 'certs' or 'disabled'.", what);
+		return 1;
+	end
+	if not what or what == "disabled" then
+		local disabled_hosts_set = set.new();
+		for host, host_options in it.filter("*", pairs(configmanager.getconfig())) do
+			if host_options.enabled == false then
+				disabled_hosts_set:add(host);
+			end
+		end
+		if not disabled_hosts_set:empty() then
+			local msg = "Checks will be skipped for these disabled hosts: %s";
+			if what then msg = "These hosts are disabled: %s"; end
+			show_warning(msg, tostring(disabled_hosts_set));
+			if what then return 0; end
+			print""
+		end
+	end
+	if not what or what == "config" then
+		print("Checking config...");
+		local deprecated = set.new({
+			"bosh_ports", "disallow_s2s", "no_daemonize", "anonymous_login", "require_encryption",
+			"vcard_compatibility", "cross_domain_bosh", "cross_domain_websocket", "daemonize",
+		});
+		local known_global_options = set.new({
+			"pidfile", "log", "plugin_paths", "prosody_user", "prosody_group", "daemonize",
+			"umask", "prosodyctl_timeout", "use_ipv6", "use_libevent", "network_settings",
+			"network_backend", "http_default_host",
+			"statistics_interval", "statistics", "statistics_config",
+		});
+		local config = configmanager.getconfig();
+		-- Check that we have any global options (caused by putting a host at the top)
+		if it.count(it.filter("log", pairs(config["*"]))) == 0 then
+			ok = false;
+			print("");
+			print("    No global options defined. Perhaps you have put a host definition at the top")
+			print("    of the config file? They should be at the bottom, see https://prosody.im/doc/configure#overview");
+		end
+		if it.count(enabled_hosts()) == 0 then
+			ok = false;
+			print("");
+			if it.count(it.filter("*", pairs(config))) == 0 then
+				print("    No hosts are defined, please add at least one VirtualHost section")
+			elseif config["*"]["enabled"] == false then
+				print("    No hosts are enabled. Remove enabled = false from the global section or put enabled = true under at least one VirtualHost section")
+			else
+				print("    All hosts are disabled. Remove enabled = false from at least one VirtualHost section")
+			end
+		end
+		if not config["*"].modules_enabled then
+			print("    No global modules_enabled is set?");
+			local suggested_global_modules;
+			for host, options in enabled_hosts() do --luacheck: ignore 213/host
+				if not options.component_module and options.modules_enabled then
+					suggested_global_modules = set.intersection(suggested_global_modules or set.new(options.modules_enabled), set.new(options.modules_enabled));
+				end
+			end
+			if suggested_global_modules and not suggested_global_modules:empty() then
+				print("    Consider moving these modules into modules_enabled in the global section:")
+				print("    "..tostring(suggested_global_modules / function (x) return ("%q"):format(x) end));
+			end
+			print();
+		end
+
+		do -- Check for modules enabled both normally and as components
+			local modules = set.new(config["*"]["modules_enabled"]);
+			for host, options in enabled_hosts() do
+				local component_module = options.component_module;
+				if component_module and modules:contains(component_module) then
+					print(("    mod_%s is enabled both in modules_enabled and as Component %q %q"):format(component_module, host, component_module));
+					print("    This means the service is enabled on all VirtualHosts as well as the Component.");
+					print("    Are you sure this what you want? It may cause unexpected behaviour.");
+				end
+			end
+		end
+
+		-- Check for global options under hosts
+		local global_options = set.new(it.to_array(it.keys(config["*"])));
+		local deprecated_global_options = set.intersection(global_options, deprecated);
+		if not deprecated_global_options:empty() then
+			print("");
+			print("    You have some deprecated options in the global section:");
+			print("    "..tostring(deprecated_global_options))
+			ok = false;
+		end
+		for host, options in it.filter(function (h) return h ~= "*" end, pairs(configmanager.getconfig())) do
+			local host_options = set.new(it.to_array(it.keys(options)));
+			local misplaced_options = set.intersection(host_options, known_global_options);
+			for name in pairs(options) do
+				if name:match("^interfaces?")
+				or name:match("_ports?$") or name:match("_interfaces?$")
+				or (name:match("_ssl$") and not name:match("^[cs]2s_ssl$")) then
+					misplaced_options:add(name);
+				end
+			end
+			if not misplaced_options:empty() then
+				ok = false;
+				print("");
+				local n = it.count(misplaced_options);
+				print("    You have "..n.." option"..(n>1 and "s " or " ").."set under "..host.." that should be");
+				print("    in the global section of the config file, above any VirtualHost or Component definitions,")
+				print("    see https://prosody.im/doc/configure#overview for more information.")
+				print("");
+				print("    You need to move the following option"..(n>1 and "s" or "")..": "..table.concat(it.to_array(misplaced_options), ", "));
+			end
+		end
+		for host, options in enabled_hosts() do
+			local host_options = set.new(it.to_array(it.keys(options)));
+			local subdomain = host:match("^[^.]+");
+			if not(host_options:contains("component_module")) and (subdomain == "jabber" or subdomain == "xmpp"
+			   or subdomain == "chat" or subdomain == "im") then
+				print("");
+				print("    Suggestion: If "..host.. " is a new host with no real users yet, consider renaming it now to");
+				print("     "..host:gsub("^[^.]+%.", "")..". You can use SRV records to redirect XMPP clients and servers to "..host..".");
+				print("     For more information see: https://prosody.im/doc/dns");
+			end
+		end
+		local all_modules = set.new(config["*"].modules_enabled);
+		local all_options = set.new(it.to_array(it.keys(config["*"])));
+		for host in enabled_hosts() do
+			all_options:include(set.new(it.to_array(it.keys(config[host]))));
+			all_modules:include(set.new(config[host].modules_enabled));
+		end
+		for mod in all_modules do
+			if mod:match("^mod_") then
+				print("");
+				print("    Modules in modules_enabled should not have the 'mod_' prefix included.");
+				print("    Change '"..mod.."' to '"..mod:match("^mod_(.*)").."'.");
+			elseif mod:match("^auth_") then
+				print("");
+				print("    Authentication modules should not be added to modules_enabled,");
+				print("    but be specified in the 'authentication' option.");
+				print("    Remove '"..mod.."' from modules_enabled and instead add");
+				print("        authentication = '"..mod:match("^auth_(.*)").."'");
+				print("    For more information see https://prosody.im/doc/authentication");
+			elseif mod:match("^storage_") then
+				print("");
+				print("    storage modules should not be added to modules_enabled,");
+				print("    but be specified in the 'storage' option.");
+				print("    Remove '"..mod.."' from modules_enabled and instead add");
+				print("        storage = '"..mod:match("^storage_(.*)").."'");
+				print("    For more information see https://prosody.im/doc/storage");
+			end
+		end
+		if all_modules:contains("vcard") and all_modules:contains("vcard_legacy") then
+			print("");
+			print("    Both mod_vcard_legacy and mod_vcard are enabled but they conflict");
+			print("    with each other. Remove one.");
+		end
+		if all_modules:contains("pep") and all_modules:contains("pep_simple") then
+			print("");
+			print("    Both mod_pep_simple and mod_pep are enabled but they conflict");
+			print("    with each other. Remove one.");
+		end
+		for host, host_config in pairs(config) do --luacheck: ignore 213/host
+			if type(rawget(host_config, "storage")) == "string" and rawget(host_config, "default_storage") then
+				print("");
+				print("    The 'default_storage' option is not needed if 'storage' is set to a string.");
+				break;
+			end
+		end
+		local require_encryption = set.intersection(all_options, set.new({
+			"require_encryption", "c2s_require_encryption", "s2s_require_encryption"
+		})):empty();
+		local ssl = dependencies.softreq"ssl";
+		if not ssl then
+			if not require_encryption then
+				print("");
+				print("    You require encryption but LuaSec is not available.");
+				print("    Connections will fail.");
+				ok = false;
+			end
+		elseif not ssl.loadcertificate then
+			if all_options:contains("s2s_secure_auth") then
+				print("");
+				print("    You have set s2s_secure_auth but your version of LuaSec does ");
+				print("    not support certificate validation, so all s2s connections will");
+				print("    fail.");
+				ok = false;
+			elseif all_options:contains("s2s_secure_domains") then
+				local secure_domains = set.new();
+				for host in enabled_hosts() do
+					if config[host].s2s_secure_auth == true then
+						secure_domains:add("*");
+					else
+						secure_domains:include(set.new(config[host].s2s_secure_domains));
+					end
+				end
+				if not secure_domains:empty() then
+					print("");
+					print("    You have set s2s_secure_domains but your version of LuaSec does ");
+					print("    not support certificate validation, so s2s connections to/from ");
+					print("    these domains will fail.");
+					ok = false;
+				end
+			end
+		elseif require_encryption and not all_modules:contains("tls") then
+			print("");
+			print("    You require encryption but mod_tls is not enabled.");
+			print("    Connections will fail.");
+			ok = false;
+		end
+
+		print("Done.\n");
+	end
+	if not what or what == "dns" then
+		local dns = require "net.dns";
+		local idna = require "util.encodings".idna;
+		local ip = require "util.ip";
+		local c2s_ports = set.new(configmanager.get("*", "c2s_ports") or {5222});
+		local s2s_ports = set.new(configmanager.get("*", "s2s_ports") or {5269});
+
+		local c2s_srv_required, s2s_srv_required;
+		if not c2s_ports:contains(5222) then
+			c2s_srv_required = true;
+		end
+		if not s2s_ports:contains(5269) then
+			s2s_srv_required = true;
+		end
+
+		local problem_hosts = set.new();
+
+		local external_addresses, internal_addresses = set.new(), set.new();
+
+		local fqdn = socket.dns.tohostname(socket.dns.gethostname());
+		if fqdn then
+			do
+				local res = dns.lookup(idna.to_ascii(fqdn), "A");
+				if res then
+					for _, record in ipairs(res) do
+						external_addresses:add(record.a);
+					end
+				end
+			end
+			do
+				local res = dns.lookup(idna.to_ascii(fqdn), "AAAA");
+				if res then
+					for _, record in ipairs(res) do
+						external_addresses:add(record.aaaa);
+					end
+				end
+			end
+		end
+
+		local local_addresses = require"util.net".local_addresses() or {};
+
+		for addr in it.values(local_addresses) do
+			if not ip.new_ip(addr).private then
+				external_addresses:add(addr);
+			else
+				internal_addresses:add(addr);
+			end
+		end
+
+		if external_addresses:empty() then
+			print("");
+			print("   Failed to determine the external addresses of this server. Checks may be inaccurate.");
+			c2s_srv_required, s2s_srv_required = true, true;
+		end
+
+		local v6_supported = not not socket.tcp6;
+
+		for jid, host_options in enabled_hosts() do
+			local all_targets_ok, some_targets_ok = true, false;
+			local node, host = jid_split(jid);
+
+			local modules, component_module = modulemanager.get_modules_for_host(host);
+			if component_module then
+				modules:add(component_module);
+			end
+
+			local is_component = not not host_options.component_module;
+			print("Checking DNS for "..(is_component and "component" or "host").." "..jid.."...");
+			if node then
+				print("Only the domain part ("..host..") is used in DNS.")
+			end
+			local target_hosts = set.new();
+			if modules:contains("c2s") then
+				local res = dns.lookup("_xmpp-client._tcp."..idna.to_ascii(host)..".", "SRV");
+				if res then
+					for _, record in ipairs(res) do
+						target_hosts:add(record.srv.target);
+						if not c2s_ports:contains(record.srv.port) then
+							print("    SRV target "..record.srv.target.." contains unknown client port: "..record.srv.port);
+						end
+					end
+				else
+					if c2s_srv_required then
+						print("    No _xmpp-client SRV record found for "..host..", but it looks like you need one.");
+						all_targets_ok = false;
+					else
+						target_hosts:add(host);
+					end
+				end
+			end
+			if modules:contains("s2s") then
+				local res = dns.lookup("_xmpp-server._tcp."..idna.to_ascii(host)..".", "SRV");
+				if res then
+					for _, record in ipairs(res) do
+						target_hosts:add(record.srv.target);
+						if not s2s_ports:contains(record.srv.port) then
+							print("    SRV target "..record.srv.target.." contains unknown server port: "..record.srv.port);
+						end
+					end
+				else
+					if s2s_srv_required then
+						print("    No _xmpp-server SRV record found for "..host..", but it looks like you need one.");
+						all_targets_ok = false;
+					else
+						target_hosts:add(host);
+					end
+				end
+			end
+			if target_hosts:empty() then
+				target_hosts:add(host);
+			end
+
+			if target_hosts:contains("localhost") then
+				print("    Target 'localhost' cannot be accessed from other servers");
+				target_hosts:remove("localhost");
+			end
+
+			if modules:contains("proxy65") then
+				local proxy65_target = configmanager.get(host, "proxy65_address") or host;
+				if type(proxy65_target) == "string" then
+					local A, AAAA = dns.lookup(idna.to_ascii(proxy65_target), "A"), dns.lookup(idna.to_ascii(proxy65_target), "AAAA");
+					local prob = {};
+					if not A then
+						table.insert(prob, "A");
+					end
+					if v6_supported and not AAAA then
+						table.insert(prob, "AAAA");
+					end
+					if #prob > 0 then
+						print("    File transfer proxy "..proxy65_target.." has no "..table.concat(prob, "/")
+						.." record. Create one or set 'proxy65_address' to the correct host/IP.");
+					end
+				else
+					print("    proxy65_address for "..host.." should be set to a string, unable to perform DNS check");
+				end
+			end
+
+			for target_host in target_hosts do
+				local host_ok_v4, host_ok_v6;
+				do
+					local res = dns.lookup(idna.to_ascii(target_host), "A");
+					if res then
+						for _, record in ipairs(res) do
+							if external_addresses:contains(record.a) then
+								some_targets_ok = true;
+								host_ok_v4 = true;
+							elseif internal_addresses:contains(record.a) then
+								host_ok_v4 = true;
+								some_targets_ok = true;
+								print("    "..target_host.." A record points to internal address, external connections might fail");
+							else
+								print("    "..target_host.." A record points to unknown address "..record.a);
+								all_targets_ok = false;
+							end
+						end
+					end
+				end
+				do
+					local res = dns.lookup(idna.to_ascii(target_host), "AAAA");
+					if res then
+						for _, record in ipairs(res) do
+							if external_addresses:contains(record.aaaa) then
+								some_targets_ok = true;
+								host_ok_v6 = true;
+							elseif internal_addresses:contains(record.aaaa) then
+								host_ok_v6 = true;
+								some_targets_ok = true;
+								print("    "..target_host.." AAAA record points to internal address, external connections might fail");
+							else
+								print("    "..target_host.." AAAA record points to unknown address "..record.aaaa);
+								all_targets_ok = false;
+							end
+						end
+					end
+				end
+
+				local bad_protos = {}
+				if not host_ok_v4 then
+					table.insert(bad_protos, "IPv4");
+				end
+				if not host_ok_v6 then
+					table.insert(bad_protos, "IPv6");
+				end
+				if #bad_protos > 0 then
+					print("    Host "..target_host.." does not seem to resolve to this server ("..table.concat(bad_protos, "/")..")");
+				end
+				if host_ok_v6 and not v6_supported then
+					print("    Host "..target_host.." has AAAA records, but your version of LuaSocket does not support IPv6.");
+					print("      Please see https://prosody.im/doc/ipv6 for more information.");
+				end
+			end
+			if not all_targets_ok then
+				print("    "..(some_targets_ok and "Only some" or "No").." targets for "..host.." appear to resolve to this server.");
+				if is_component then
+					print("    DNS records are necessary if you want users on other servers to access this component.");
+				end
+				problem_hosts:add(host);
+			end
+			print("");
+		end
+		if not problem_hosts:empty() then
+			print("");
+			print("For more information about DNS configuration please see https://prosody.im/doc/dns");
+			print("");
+			ok = false;
+		end
+	end
+	if not what or what == "certs" then
+		local cert_ok;
+		print"Checking certificates..."
+		local x509_verify_identity = require"util.x509".verify_identity;
+		local create_context = require "core.certmanager".create_context;
+		local ssl = dependencies.softreq"ssl";
+		-- local datetime_parse = require"util.datetime".parse_x509;
+		local load_cert = ssl and ssl.loadcertificate;
+		-- or ssl.cert_from_pem
+		if not ssl then
+			print("LuaSec not available, can't perform certificate checks")
+			if what == "certs" then cert_ok = false end
+		elseif not load_cert then
+			print("This version of LuaSec (" .. ssl._VERSION .. ") does not support certificate checking");
+			cert_ok = false
+		else
+			local function skip_bare_jid_hosts(host)
+				if jid_split(host) then
+					-- See issue #779
+					return false;
+				end
+				return true;
+			end
+			for host in it.filter(skip_bare_jid_hosts, enabled_hosts()) do
+				print("Checking certificate for "..host);
+				-- First, let's find out what certificate this host uses.
+				local host_ssl_config = configmanager.rawget(host, "ssl")
+					or configmanager.rawget(host:match("%.(.*)"), "ssl");
+				local global_ssl_config = configmanager.rawget("*", "ssl");
+				local ok, err, ssl_config = create_context(host, "server", host_ssl_config, global_ssl_config);
+				if not ok then
+					print("  Error: "..err);
+					cert_ok = false
+				elseif not ssl_config.certificate then
+					print("  No 'certificate' found for "..host)
+					cert_ok = false
+				elseif not ssl_config.key then
+					print("  No 'key' found for "..host)
+					cert_ok = false
+				else
+					local key, err = io.open(ssl_config.key); -- Permissions check only
+					if not key then
+						print("    Could not open "..ssl_config.key..": "..err);
+						cert_ok = false
+					else
+						key:close();
+					end
+					local cert_fh, err = io.open(ssl_config.certificate); -- Load the file.
+					if not cert_fh then
+						print("    Could not open "..ssl_config.certificate..": "..err);
+						cert_ok = false
+					else
+						print("  Certificate: "..ssl_config.certificate)
+						local cert = load_cert(cert_fh:read"*a"); cert_fh:close();
+						if not cert:validat(os.time()) then
+							print("    Certificate has expired.")
+							cert_ok = false
+						elseif not cert:validat(os.time() + 86400) then
+							print("    Certificate expires within one day.")
+							cert_ok = false
+						elseif not cert:validat(os.time() + 86400*7) then
+							print("    Certificate expires within one week.")
+						elseif not cert:validat(os.time() + 86400*31) then
+							print("    Certificate expires within one month.")
+						end
+						if configmanager.get(host, "component_module") == nil
+							and not x509_verify_identity(host, "_xmpp-client", cert) then
+							print("    Not valid for client connections to "..host..".")
+							cert_ok = false
+						end
+						if (not (configmanager.get(host, "anonymous_login")
+							or configmanager.get(host, "authentication") == "anonymous"))
+							and not x509_verify_identity(host, "_xmpp-server", cert) then
+							print("    Not valid for server-to-server connections to "..host..".")
+							cert_ok = false
+						end
+					end
+				end
+			end
+		end
+		if cert_ok == false then
+			print("")
+			print("For more information about certificates please see https://prosody.im/doc/certificates");
+			ok = false
+		end
+		print("")
+	end
+	if not ok then
+		print("Problems found, see above.");
+	else
+		print("All checks passed, congratulations!");
+	end
+	return ok and 0 or 2;
+end
+
+return {
+	check = check;
+};
diff --git a/util/prosodyctl/shell.lua b/util/prosodyctl/shell.lua
index cbcea927..1d07e6ec 100644
--- a/util/prosodyctl/shell.lua
+++ b/util/prosodyctl/shell.lua
@@ -126,5 +126,5 @@ local function start(arg) --luacheck: ignore 212/arg
 end
 
 return {
-	start = start;
+	shell = start;
 };