--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mod_easy_invite/README.markdown	Fri Dec 27 10:41:01 2019 +0000
@@ -0,0 +1,31 @@
+
+This module allows admins and users to create invitations suitable for sharing
+to potential new users/contacts.
+
+User invitations can be created through the "New Invite" ad-hoc command. An overview
+of the semantics and protocol can be found at [modernxmpp.org/client/invites](https://docs.modernxmpp.org/client/invites/).
+
+This module depends on mod_invites to actually create and store the invitation tokens.
+
+# Configuration
+
+To allow users to join your server through invitations, you must
+enable mod_register_ibr and set allow_registration = true, and then
+also set `registration_invite_only = true` to restrict registration.
+
+``` {.lua}
+-- To allow invitation through a token, mod_register
+registration_invite_only = true
+```
+
+To allow existing users of your server to send invitation links that
+allow new people to join your server, you can set `allow_user_invites = true`.
+
+If you do not wish users to invite other users to create accounts on your
+server, set `allow_user_invites = false`. They will still be able to send
+contact invites, but new contacts will be required to register an account
+on a different server.
+
+# Compatibility
+
+0.11 and later.

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mod_easy_invite/mod_easy_invite.lua	Fri Dec 27 10:41:01 2019 +0000
@@ -0,0 +1,182 @@
+-- XEP-0401: Easy User Onboarding
+local dataforms = require "util.dataforms";
+local datetime = require "util.datetime";
+local jid_bare = require "util.jid".bare;
+local jid_split = require "util.jid".split;
+local split_jid = require "util.jid".split;
+local rostermanager = require "core.rostermanager";
+local st = require "util.stanza";
+
+local invite_only = module:get_option_boolean("registration_invite_only", true);
+local require_encryption = module:get_option_boolean("c2s_require_encryption",
+	module:get_option_boolean("require_encryption", false));
+
+local new_adhoc = module:require("adhoc").new;
+
+-- Whether local users can invite other users to create an account on this server
+local allow_user_invites = module:get_option_boolean("allow_user_invites", true);
+
+local invites = module:depends("invites");
+
+local invite_result_form = dataforms.new({
+		title = "Your Invite",
+		-- TODO instructions = something helpful
+		{
+			name = "uri";
+			label = "Invite URI";
+			-- TODO desc = something helpful
+		},
+		{
+			name = "url" ;
+			var = "landing-url";
+			label = "Invite landing URL";
+		},
+		{
+			name = "expire";
+			label = "Token valid until";
+		},
+	});
+
+module:depends("adhoc");
+module:provides("adhoc", new_adhoc("New Invite", "urn:xmpp:invite#invite",
+		function (_, data)
+			local username = split_jid(data.from);
+			local invite = invites.create_contact(username, allow_user_invites);
+			--TODO: check errors
+			return {
+				status = "completed";
+				form = {
+					layout = invite_result_form;
+					values = {
+						uri = invite.uri;
+						url = invite.landing_page;
+						expire = datetime.datetime(invite.expires);
+					};
+				};
+			};
+		end, "local_user"));
+
+
+-- TODO
+-- module:provides("adhoc", new_adhoc("Create account", "urn:xmpp:invite#create-account", function () end, "admin"));
+
+-- XEP-0379: Pre-Authenticated Roster Subscription
+module:hook("presence/bare", function (event)
+	local stanza = event.stanza;
+	if stanza.attr.type ~= "subscribe" then return end
+
+	local preauth = stanza:get_child("preauth", "urn:xmpp:pars:0");
+	if not preauth then return end
+	local token = preauth.attr.token;
+	if not token then return end
+
+	local username, host = jid_split(stanza.attr.to);
+
+	local invite, err = invites.get(token, username);
+
+	if not invite then
+		module:log("debug", "Got invalid token, error: %s", err);
+		return;
+	end
+
+	local contact = jid_bare(stanza.attr.from);
+
+	module:log("debug", "Approving inbound subscription to %s from %s", username, contact);
+	if rostermanager.set_contact_pending_in(username, host, contact, stanza) then
+		if rostermanager.subscribed(username, host, contact) then
+			invite:use();
+			rostermanager.roster_push(username, host, contact);
+
+			-- Send back a subscription request (goal is mutual subscription)
+			if not rostermanager.is_user_subscribed(username, host, contact)
+			and not rostermanager.is_contact_pending_out(username, host, contact) then
+				module:log("debug", "Sending automatic subscription request to %s from %s", contact, username);
+				if rostermanager.set_contact_pending_out(username, host, contact) then
+					rostermanager.roster_push(username, host, contact);
+					module:send(st.presence({type = "subscribe", to = contact }));
+				else
+					module:log("warn", "Failed to set contact pending out for %s", username);
+				end
+			end
+		end
+	end
+end, 1);
+
+-- TODO sender side, magic automatic mutual subscription
+
+local invite_stream_feature = st.stanza("register", { xmlns = "urn:xmpp:invite" }):up();
+module:hook("stream-features", function(event)
+	local session, features = event.origin, event.features;
+
+	-- Advertise to unauthorized clients only.
+	if session.type ~= "c2s_unauthed" or (require_encryption and not session.secure) then
+		return
+	end
+
+	features:add_child(invite_stream_feature);
+end);
+
+-- Client is submitting a preauth token to allow registration
+module:hook("stanza/iq/urn:xmpp:pars:0:preauth", function(event)
+	local preauth = event.stanza.tags[1];
+	local token = preauth.attr.token;
+	local validated_invite = invites.get(token);
+	if not validated_invite then
+		local reply = st.error_reply(event.stanza, "cancel", "forbidden", "The invite token is invalid or expired");
+		event.origin.send(reply);
+		return true;
+	end
+	event.origin.validated_invite = validated_invite;
+	local reply = st.reply(event.stanza);
+	event.origin.send(reply);
+	return true;
+end);
+
+-- Registration attempt - ensure a valid preauth token has been supplied
+module:hook("user-registering", function (event)
+	local validated_invite = event.session.validated_invite;
+	if invite_only and not validated_invite then
+		event.allowed = false;
+		event.reason = "Registration on this server is through invitation only";
+		return;
+	end
+end);
+
+-- Make a *one-way* subscription. User will see when contact is online,
+-- contact will not see when user is online.
+function subscribe(host, user_username, contact_username)
+	local user_jid = user_username.."@"..host;
+	local contact_jid = contact_username.."@"..host;
+	-- Update user's roster to say subscription request is pending...
+	rostermanager.set_contact_pending_out(user_username, host, contact_jid);
+	-- Update contact's roster to say subscription request is pending...
+	rostermanager.set_contact_pending_in(contact_username, host, user_jid);
+	-- Update contact's roster to say subscription request approved...
+	rostermanager.subscribed(contact_username, host, user_jid);
+	-- Update user's roster to say subscription request approved...
+	rostermanager.process_inbound_subscription_approval(user_username, host, contact_jid);
+end
+
+-- Make a mutual subscription between jid1 and jid2. Each JID will see
+-- when the other one is online.
+function subscribe_both(host, user1, user2)
+	subscribe(host, user1, user2);
+	subscribe(host, user2, user1);
+end
+
+-- Registration successful, if there was a preauth token, mark it as used
+module:hook("user-registered", function (event)
+	local validated_invite = event.session.validated_invite;
+	if not validated_invite then
+		return;
+	end
+	local inviter_username = validated_invite.inviter;
+	validated_invite:use();
+
+	if not inviter_username then return; end
+
+	local contact_username = event.username;
+
+	module:log("debug", "Creating mutual subscription between %s and %s", inviter_username, contact_username);
+	subscribe_both(module.host, inviter_username, contact_username);
+end);