Add logout functionality

src/store.rs

@@ -356,6 +356,21 @@ impl<'a, 'txn> IdCoopStoreTxn<'a, 'txn> {
         }))
     }
 
+    /// Given the login session's ID, destroy the session.
+    pub async fn destroy_login_session(&mut self, login_session_id: i64) -> eyre::Result<()> {
+        sqlx::query!(
+            "
+            DELETE FROM login_sessions
+            WHERE login_session_id = $1
+            ",
+            login_session_id
+        )
+        .execute(&mut **self.txn)
+        .await
+        .context("failed to destroy login session")?;
+        Ok(())
+    }
+
     /// Given an access token's hash, looks up the corresponding application session.
     pub async fn lookup_application_session(
         &mut self,

src/web.rs

@@ -51,9 +51,12 @@ use crate::{
     },
 };
 
-pub mod ambient;
+use self::logout::{get_logout, post_logout};
+
+pub(crate) mod ambient;
 pub mod errors;
 pub mod login;
+pub mod logout;
 pub mod oauth_openid;
 pub mod sessionless_xsrf;
 
@@ -150,6 +153,17 @@ pub(crate) async fn make_router(
                     HeaderValue::from_static("DENY"),
                 )),
         )
+        .route(
+            // CORS NOT to be made available on this endpoint!
+            // Block loading this in a frame!
+            "/logout",
+            get(get_logout)
+                .post(post_logout)
+                .layer(SetResponseHeaderLayer::overriding(
+                    HeaderName::from_static("x-frame-options"),
+                    HeaderValue::from_static("DENY"),
+                )),
+        )
         .route(
             "/oidc/token",
             post(oidc_token).layer(CorsLayer::permissive().max_age(Duration::from_secs(600))),

src/web/login.rs

@@ -135,6 +135,8 @@ pub const LOGIN_SESSION_TOKEN_HASH_BYTES: usize = 32;
 ///      e.g. perhaps the persona should be a hash of the user's UUID?
 pub const LOGIN_SESSION_XSRF_SECRET_BYTES: usize = 32;
 
+pub const LOGIN_SESSION_COOKIE_NAME: &str = "__Host-LoginSession";
+
 /// Represents a login session, which is effectively just a 'web UI' session for a user.
 pub struct LoginSession {
     /// The system name of the user who is logged in to the idCoop web UI
@@ -231,7 +233,7 @@ where
         else {
             return Err((StatusCode::UNAUTHORIZED, "No login session."));
         };
-        let Some(cookie_val) = cookies.get("__Host-LoginSession").map(str::to_owned) else {
+        let Some(cookie_val) = cookies.get(LOGIN_SESSION_COOKIE_NAME).map(str::to_owned) else {
             return Err((StatusCode::UNAUTHORIZED, "No login session."));
         };
         let Ok(login_session_token) = BASE64_URL_SAFE_NO_PAD.decode(&cookie_val) else {
@@ -496,7 +498,7 @@ pub async fn post_login(
         .context("failed to store session in database")?;
 
     cookies.add(
-        Cookie::build(("__Host-LoginSession", login_session_token_b64.clone()))
+        Cookie::build((LOGIN_SESSION_COOKIE_NAME, login_session_token_b64.clone()))
             .path("/")
             .http_only(true)
             .secure(true)

src/web/logout.rs

@@ -0,0 +1,88 @@
+//! logout: let users log out
+
+use std::sync::Arc;
+
+use axum::{
+    http::StatusCode,
+    response::{IntoResponse, Response},
+    Extension,
+};
+use hornbeam::render_template_string;
+use tower_cookies::{Cookie, Cookies};
+
+use crate::store::IdCoopStore;
+
+use super::{
+    ambient::Ambient,
+    login::{LoginSession, LOGIN_SESSION_COOKIE_NAME},
+    sessionless_xsrf, DesiredLocale, Rendered, WebResult, TEMPLATING,
+};
+
+/// `GET /logout`
+///
+/// If logged in, show a button to send a POST request to log out.
+///
+/// If not logged in, shows a success message.
+pub async fn get_logout(ambient: Ambient, DesiredLocale(locale): DesiredLocale) -> Response {
+    if ambient.user.is_some() {
+        // display logout button
+        Rendered(render_template_string!(TEMPLATING, logout_ask, locale, {
+            ambient
+        }))
+        .into_response()
+    } else {
+        // display success message
+        Rendered(render_template_string!(
+            TEMPLATING,
+            logout_success,
+            locale,
+            { ambient }
+        ))
+        .into_response()
+    }
+}
+
+/// `POST /logout`
+///
+/// If logged in, destroy session and show success message.
+///
+/// If not logged in, show success message.
+///
+/// We don't care about any specific form data.
+///
+/// We don't require an XSRF secret, because SameSite=Lax will protect us
+/// in modern browsers.
+/// In other browsers, being logged out is not a huge deal; it doesn't seem to be
+/// a particularly interesting risk or attack vector, therefore.
+pub async fn post_logout(
+    current_session: Result<LoginSession, (StatusCode, &'static str)>,
+    mut ambient: Ambient,
+    cookies: Cookies,
+    Extension(store): Extension<Arc<IdCoopStore>>,
+    DesiredLocale(locale): DesiredLocale,
+) -> WebResult<Response> {
+    if let Ok(session) = current_session {
+        store
+            .txn(|mut txn| {
+                Box::pin(async move { txn.destroy_login_session(session.login_session_id).await })
+            })
+            .await?;
+
+        // Clear out cookies
+        for cookie_name in &[LOGIN_SESSION_COOKIE_NAME, sessionless_xsrf::COOKIE_NAME] {
+            if let Some(cookie) = cookies.get(cookie_name).map(Cookie::into_owned) {
+                cookies.remove(cookie);
+            }
+        }
+
+        ambient.user = None;
+    }
+
+    Ok(Rendered(render_template_string!(
+        TEMPLATING,
+        logout_success,
+        locale,
+        { ambient }
+    ))
+    .into_response())
+}

templates/pages/logout_ask.hnb

@@ -0,0 +1,15 @@
+CentredPage {$ambient}
+    :title
+        @logout_ask_title
+
+    :main
+        h1
+            @logout_ask_title
+
+        form {method = "POST"}
+            article
+                @logout_ask_main
+
+            fieldset.grid
+                button {type = "submit"}
+                    @logout_ask_logout

templates/pages/logout_success.hnb

@@ -0,0 +1,10 @@
+CentredPage {$ambient}
+    :title
+        @logout_success_title
+
+    :main
+        h1
+            @logout_success_title
+
+        article
+            @logout_success_main

translations/en/login.ftl

@@ -29,3 +29,11 @@ consent_deny = Deny
 
 #consent_warn_info = Your username, user ID, display name and avatar will be sent to the service.
 consent_warn_info = Your username and user ID will be sent to the service.
+
+
+logout_ask_title = Log out?
+logout_ask_logout = Confirm log out
+logout_ask_main = Would you like to log out?
+
+logout_success_title = Logged out!
+logout_success_main = Successfully logged out. See you again soon!