implement /login/get_token (MSC3882)

conduwuit-example.toml

@@ -645,6 +645,22 @@
 #
 #openid_token_ttl = 3600
 
+# Allow an existing session to mint a login token for another client.
+# This requires interactive authentication, but has security ramifications
+# as a malicious client could use the mechanism to spawn more than one
+# session.
+# Enabled by default.
+#
+#login_via_existing_session = true
+
+# Login token expiration/TTL in milliseconds.
+#
+# These are short-lived tokens for the m.login.token endpoint.
+# This is used to allow existing sessions to create new sessions.
+# see login_via_existing_session.
+#
+#login_token_ttl = 120000
+
 # Static TURN username to provide the client if not using a shared secret
 # ("turn_secret"), It is recommended to use a shared secret over static
 # credentials.

src/api/client/capabilities.rs

@@ -32,8 +32,9 @@ pub(crate) async fn get_capabilities_route(
 	// we do not implement 3PID stuff
 	capabilities.thirdparty_id_changes = ThirdPartyIdChangesCapability { enabled: false };
 
-	// we dont support generating tokens yet
-	capabilities.get_login_token = GetLoginTokenCapability { enabled: false };
+	capabilities.get_login_token = GetLoginTokenCapability {
+		enabled: services.server.config.login_via_existing_session,
+	};
 
 	// MSC4133 capability
 	capabilities

src/api/client/session.rs

@@ -1,3 +1,5 @@
+use std::time::Duration;
+
 use axum::extract::State;
 use axum_client_ip::InsecureClientIp;
 use conduwuit::{debug, err, info, utils::ReadyExt, warn, Err};
@@ -6,20 +8,22 @@ use ruma::{
 	api::client::{
 		error::ErrorKind,
 		session::{
+			get_login_token,
 			get_login_types::{
 				self,
-				v3::{ApplicationServiceLoginType, PasswordLoginType},
+				v3::{ApplicationServiceLoginType, PasswordLoginType, TokenLoginType},
 			},
 			login::{
 				self,
 				v3::{DiscoveryInfo, HomeserverInfo},
 			},
 			logout, logout_all,
 		},
-		uiaa::UserIdentifier,
+		uiaa,
 	},
 	OwnedUserId, UserId,
 };
+use service::uiaa::SESSION_ID_LENGTH;
 
 use super::{DEVICE_ID_LENGTH, TOKEN_LENGTH};
 use crate::{utils, utils::hash, Error, Result, Ruma};
@@ -30,12 +34,16 @@ use crate::{utils, utils::hash, Error, Result, Ruma};
 /// the `type` field when logging in.
 #[tracing::instrument(skip_all, fields(%client), name = "login")]
 pub(crate) async fn get_login_types_route(
+	State(services): State<crate::State>,
 	InsecureClientIp(client): InsecureClientIp,
 	_body: Ruma<get_login_types::v3::Request>,
 ) -> Result<get_login_types::v3::Response> {
 	Ok(get_login_types::v3::Response::new(vec![
 		get_login_types::v3::LoginType::Password(PasswordLoginType::default()),
 		get_login_types::v3::LoginType::ApplicationService(ApplicationServiceLoginType::default()),
+		get_login_types::v3::LoginType::Token(TokenLoginType {
+			get_login_token: services.server.config.login_via_existing_session,
+		}),
 	]))
 }
 
@@ -70,7 +78,9 @@ pub(crate) async fn login_route(
 			..
 		}) => {
 			debug!("Got password login type");
-			let user_id = if let Some(UserIdentifier::UserIdOrLocalpart(user_id)) = identifier {
+			let user_id = if let Some(uiaa::UserIdentifier::UserIdOrLocalpart(user_id)) =
+				identifier
+			{
 				UserId::parse_with_server_name(
 					user_id.to_lowercase(),
 					services.globals.server_name(),
@@ -99,33 +109,35 @@ pub(crate) async fn login_route(
 
 			user_id
 		},
-		| login::v3::LoginInfo::Token(login::v3::Token { token: _ }) => {
+		| login::v3::LoginInfo::Token(login::v3::Token { token }) => {
 			debug!("Got token login type");
-			return Err!(Request(Unknown(
-				"Token login is not supported."
-			)));
+			if !services.server.config.login_via_existing_session {
+				return Err!(Request(Unknown("Token login is not enabled.")));
+			}
+			services.users.find_from_login_token(token).await?
 		},
 		#[allow(deprecated)]
 		| login::v3::LoginInfo::ApplicationService(login::v3::ApplicationService {
 			identifier,
 			user,
 		}) => {
 			debug!("Got appservice login type");
-			let user_id = if let Some(UserIdentifier::UserIdOrLocalpart(user_id)) = identifier {
-				UserId::parse_with_server_name(
-					user_id.to_lowercase(),
-					services.globals.server_name(),
-				)
-			} else if let Some(user) = user {
-				OwnedUserId::parse(user)
-			} else {
-				warn!("Bad login type: {:?}", &body.login_info);
-				return Err(Error::BadRequest(ErrorKind::forbidden(), "Bad login type."));
-			}
-			.map_err(|e| {
-				warn!("Failed to parse username from appservice logging in: {e}");
-				Error::BadRequest(ErrorKind::InvalidUsername, "Username is invalid.")
-			})?;
+			let user_id =
+				if let Some(uiaa::UserIdentifier::UserIdOrLocalpart(user_id)) = identifier {
+					UserId::parse_with_server_name(
+						user_id.to_lowercase(),
+						services.globals.server_name(),
+					)
+				} else if let Some(user) = user {
+					OwnedUserId::parse(user)
+				} else {
+					warn!("Bad login type: {:?}", &body.login_info);
+					return Err(Error::BadRequest(ErrorKind::forbidden(), "Bad login type."));
+				}
+				.map_err(|e| {
+					warn!("Failed to parse username from appservice logging in: {e}");
+					Error::BadRequest(ErrorKind::InvalidUsername, "Username is invalid.")
+				})?;
 
 			if let Some(ref info) = body.appservice_info {
 				if !info.is_user_match(&user_id) {
@@ -217,6 +229,74 @@ pub(crate) async fn login_route(
 	})
 }
 
+/// # `POST /_matrix/client/v1/login/get_token`
+///
+/// Allows a logged-in user to get a short-lived token which can be used
+/// to log in with the m.login.token flow.
+///
+/// <https://spec.matrix.org/v1.13/client-server-api/#post_matrixclientv1loginget_token>
+#[tracing::instrument(skip_all, fields(%client), name = "login_token")]
+pub(crate) async fn login_token_route(
+	State(services): State<crate::State>,
+	InsecureClientIp(client): InsecureClientIp,
+	body: Ruma<get_login_token::v1::Request>,
+) -> Result<get_login_token::v1::Response> {
+	if !services.server.config.login_via_existing_session {
+		return Err!(Request(Unknown("Login via an existing session is not enabled")));
+	}
+	// Authentication for this endpoint was made optional, but we need
+	// authentication.
+	let sender_user = body
+		.sender_user
+		.as_ref()
+		.ok_or_else(|| Error::BadRequest(ErrorKind::MissingToken, "Missing access token."))?;
+	let sender_device = body.sender_device.as_ref().expect("user is authenticated");
+
+	// This route SHOULD have UIA
+	// TODO: How do we make only UIA sessions that have not been used before valid?
+
+	let mut uiaainfo = uiaa::UiaaInfo {
+		flows: vec![uiaa::AuthFlow { stages: vec![uiaa::AuthType::Password] }],
+		completed: Vec::new(),
+		params: Box::default(),
+		session: None,
+		auth_error: None,
+	};
+
+	if let Some(auth) = &body.auth {
+		let (worked, uiaainfo) = services
+			.uiaa
+			.try_auth(sender_user, sender_device, auth, &uiaainfo)
+			.await?;
+
+		if !worked {
+			return Err(Error::Uiaa(uiaainfo));
+		}
+
+		// Success!
+	} else if let Some(json) = body.json_body {
+		uiaainfo.session = Some(utils::random_string(SESSION_ID_LENGTH));
+		services
+			.uiaa
+			.create(sender_user, sender_device, &uiaainfo, &json);
+
+		return Err(Error::Uiaa(uiaainfo));
+	} else {
+		return Err(Error::BadRequest(ErrorKind::NotJson, "Not json."));
+	}
+
+	let login_token = utils::random_string(TOKEN_LENGTH);
+
+	let expires_in = services
+		.users
+		.create_login_token(sender_user, &login_token)?;
+
+	Ok(get_login_token::v1::Response {
+		expires_in: Duration::from_millis(expires_in),
+		login_token,
+	})
+}
+
 /// # `POST /_matrix/client/v3/logout`
 ///
 /// Log out the current device.

src/api/router.rs

@@ -34,6 +34,7 @@ pub fn build(router: Router<State>, server: &Server) -> Router<State> {
 		.ruma_route(&client::register_route)
 		.ruma_route(&client::get_login_types_route)
 		.ruma_route(&client::login_route)
+		.ruma_route(&client::login_token_route)
 		.ruma_route(&client::whoami_route)
 		.ruma_route(&client::logout_route)
 		.ruma_route(&client::logout_all_route)

src/core/config/mod.rs

@@ -767,6 +767,24 @@ pub struct Config {
 	#[serde(default = "default_openid_token_ttl")]
 	pub openid_token_ttl: u64,
 
+	/// Allow an existing session to mint a login token for another client.
+	/// This requires interactive authentication, but has security ramifications
+	/// as a malicious client could use the mechanism to spawn more than one
+	/// session.
+	/// Enabled by default.
+	#[serde(default = "true_fn")]
+	pub login_via_existing_session: bool,
+
+	/// Login token expiration/TTL in milliseconds.
+	///
+	/// These are short-lived tokens for the m.login.token endpoint.
+	/// This is used to allow existing sessions to create new sessions.
+	/// see login_via_existing_session.
+	///
+	/// default: 120000
+	#[serde(default = "default_login_token_ttl")]
+	pub login_token_ttl: u64,
+
 	/// Static TURN username to provide the client if not using a shared secret
 	/// ("turn_secret"), It is recommended to use a shared secret over static
 	/// credentials.
@@ -2373,6 +2391,8 @@ fn default_notification_push_path() -> String { "/_matrix/push/v1/notify".to_own
 
 fn default_openid_token_ttl() -> u64 { 60 * 60 }
 
+fn default_login_token_ttl() -> u64 { 2 * 60 * 1000 }
+
 fn default_turn_ttl() -> u64 { 60 * 60 * 24 }
 
 fn default_presence_idle_timeout_s() -> u64 { 5 * 60 }

src/database/maps.rs

@@ -365,6 +365,10 @@ pub(super) static MAPS: &[Descriptor] = &[
 		name: "openidtoken_expiresatuserid",
 		..descriptor::RANDOM_SMALL
 	},
+	Descriptor {
+		name: "logintoken_expiresatuserid",
+		..descriptor::RANDOM_SMALL
+	},
 	Descriptor {
 		name: "userroomid_highlightcount",
 		..descriptor::RANDOM

src/service/users/mod.rs

@@ -41,6 +41,7 @@ struct Data {
 	keyid_key: Arc<Map>,
 	onetimekeyid_onetimekeys: Arc<Map>,
 	openidtoken_expiresatuserid: Arc<Map>,
+	logintoken_expiresatuserid: Arc<Map>,
 	todeviceid_events: Arc<Map>,
 	token_userdeviceid: Arc<Map>,
 	userdeviceid_metadata: Arc<Map>,
@@ -76,6 +77,7 @@ impl crate::Service for Service {
 				keyid_key: args.db["keyid_key"].clone(),
 				onetimekeyid_onetimekeys: args.db["onetimekeyid_onetimekeys"].clone(),
 				openidtoken_expiresatuserid: args.db["openidtoken_expiresatuserid"].clone(),
+				logintoken_expiresatuserid: args.db["logintoken_expiresatuserid"].clone(),
 				todeviceid_events: args.db["todeviceid_events"].clone(),
 				token_userdeviceid: args.db["token_userdeviceid"].clone(),
 				userdeviceid_metadata: args.db["userdeviceid_metadata"].clone(),
@@ -941,6 +943,54 @@ impl Service {
 			.map_err(|e| err!(Database("User ID in openid_userid is invalid. {e}")))
 	}
 
+	/// Creates a short-lived login token, which can be used to log in using the
+	/// `m.login.token` mechanism.
+	pub fn create_login_token(&self, user_id: &UserId, token: &str) -> Result<u64> {
+		use std::num::Saturating as Sat;
+
+		let expires_in = self.services.server.config.login_token_ttl;
+		let expires_at = Sat(utils::millis_since_unix_epoch()) + Sat(expires_in);
+
+		let mut value = expires_at.0.to_be_bytes().to_vec();
+		value.extend_from_slice(user_id.as_bytes());
+
+		self.db
+			.logintoken_expiresatuserid
+			.insert(token.as_bytes(), value.as_slice());
+
+		Ok(expires_in)
+	}
+
+	/// Find out which user a login token belongs to.
+	/// Removes the token to prevent double-use attacks.
+	pub async fn find_from_login_token(&self, token: &str) -> Result<OwnedUserId> {
+		let Ok(value) = self.db.logintoken_expiresatuserid.get(token).await else {
+			return Err!(Request(Unauthorized("Login token is unrecognised")));
+		};
+
+		let (expires_at_bytes, user_bytes) = value.split_at(0_u64.to_be_bytes().len());
+		let expires_at = u64::from_be_bytes(
+			expires_at_bytes
+				.try_into()
+				.map_err(|e| err!(Database("expires_at in login_userid is invalid u64. {e}")))?,
+		);
+
+		if expires_at < utils::millis_since_unix_epoch() {
+			debug_warn!("Login token is expired, removing");
+			self.db.openidtoken_expiresatuserid.remove(token.as_bytes());
+
+			return Err!(Request(Unauthorized("Login token is expired")));
+		}
+
+		self.db.openidtoken_expiresatuserid.remove(token.as_bytes());
+
+		let user_string = utils::string_from_bytes(user_bytes)
+			.map_err(|e| err!(Database("User ID in login_userid is invalid unicode. {e}")))?;
+
+		OwnedUserId::try_from(user_string)
+			.map_err(|e| err!(Database("User ID in login_userid is invalid. {e}")))
+	}
+
 	/// Gets a specific user profile key
 	pub async fn profile_key(
 		&self,