Shut down the `/api/events` stream when the user logs out or their token expires.

When tokens are revoked (logout or expiry), the server now publishes an internal event via the new `logins` event broadcaster. These events are used to guard the `/api/events` stream. When a token revocation event arrives for the token used to subscribe to the stream, the stream is cut short, disconnecting the client.

In service of this, tokens now have IDs, which are non-confidential values that can be used to discuss tokens without their secrets being passed around unnecessarily. These IDs are not (at this time) exposed to clients, but they could be.

1 files changed, 50 insertions, 8 deletions

diff --git a/src/login/app.rs b/src/login/app.rs
index f7fec88..b8916a8 100644
--- a/src/login/app.rs
+++ b/src/login/app.rs
@@ -1,24 +1,30 @@
 use chrono::TimeDelta;
+use futures::{
+    future,
+    stream::{self, StreamExt as _},
+    Stream,
+};
 use sqlx::sqlite::SqlitePool;
 
-use super::{extract::IdentitySecret, repo::auth::Provider as _};
+use super::{broadcaster::Broadcaster, extract::IdentitySecret, repo::auth::Provider as _, types};
 use crate::{
     clock::DateTime,
     password::Password,
     repo::{
         error::NotFound as _,
         login::{Login, Provider as _},
-        token::Provider as _,
+        token::{self, Provider as _},
     },
 };
 
 pub struct Logins<'a> {
     db: &'a SqlitePool,
+    logins: &'a Broadcaster,
 }
 
 impl<'a> Logins<'a> {
-    pub const fn new(db: &'a SqlitePool) -> Self {
-        Self { db }
+    pub const fn new(db: &'a SqlitePool, logins: &'a Broadcaster) -> Self {
+        Self { db, logins }
     }
 
     pub async fn login(
@@ -63,7 +69,7 @@ impl<'a> Logins<'a> {
         &self,
         secret: &IdentitySecret,
         used_at: &DateTime,
-    ) -> Result<Login, ValidateError> {
+    ) -> Result<(token::Id, Login), ValidateError> {
         let mut tx = self.db.begin().await?;
         let login = tx
             .tokens()
@@ -75,26 +81,56 @@ impl<'a> Logins<'a> {
         Ok(login)
     }
 
+    pub fn limit_stream<E>(
+        &self,
+        token: token::Id,
+        events: impl Stream<Item = E> + std::fmt::Debug,
+    ) -> impl Stream<Item = E> + std::fmt::Debug
+    where
+        E: std::fmt::Debug,
+    {
+        let token_events = self
+            .logins
+            .subscribe()
+            .filter(move |event| future::ready(event.token == token))
+            .map(|_| GuardedEvent::TokenRevoked);
+
+        let events = events.map(|event| GuardedEvent::Event(event));
+
+        stream::select(token_events, events).scan((), |(), event| {
+            future::ready(match event {
+                GuardedEvent::Event(event) => Some(event),
+                GuardedEvent::TokenRevoked => None,
+            })
+        })
+    }
+
     pub async fn expire(&self, relative_to: &DateTime) -> Result<(), sqlx::Error> {
         // Somewhat arbitrarily, expire after 7 days.
         let expire_at = relative_to.to_owned() - TimeDelta::days(7);
 
         let mut tx = self.db.begin().await?;
-        tx.tokens().expire(&expire_at).await?;
+        let tokens = tx.tokens().expire(&expire_at).await?;
         tx.commit().await?;
 
+        for event in tokens.into_iter().map(types::TokenRevoked::from) {
+            self.logins.broadcast(&event);
+        }
+
         Ok(())
     }
 
     pub async fn logout(&self, secret: &IdentitySecret) -> Result<(), ValidateError> {
         let mut tx = self.db.begin().await?;
-        tx.tokens()
+        let token = tx
+            .tokens()
             .revoke(secret)
             .await
             .not_found(|| ValidateError::InvalidToken)?;
-
         tx.commit().await?;
 
+        self.logins.broadcast(&types::TokenRevoked::from(token));
+
         Ok(())
     }
 }
@@ -124,3 +160,9 @@ pub enum ValidateError {
     #[error(transparent)]
     DatabaseError(#[from] sqlx::Error),
 }
+
+#[derive(Debug)]
+enum GuardedEvent<E> {
+    TokenRevoked,
+    Event(E),
+}