Use cookies for flash messages

Cargo.toml

@@ -18,19 +18,16 @@ argon2 = { version = "0.5.3", features = ["std"] }
 askama = { version = "0.12.1", features = ["with-axum"], default-features = false }
 askama_axum = { version = "0.4.0", default-features = false }
 axum = "0.7.4"
+axum-extra = { version = "0.9.3", features = ["cookie-signed"] }
 base64 = "0.22.0"
 config = "0.14.0"
-hex = "0.4.3"
-hmac = { version = "0.12.1", features = ["std"] }
-htmlescape = "0.3.1"
 once_cell = "1.19.0"
 rand = "0.8.5"
 regex = "1.10.3"
-reqwest = { version = "0.11.24", features = ["json"], default-features = false }
+reqwest = { version = "0.11.24", features = ["cookies", "json"], default-features = false }
 secrecy = { version = "0.8.0", features = ["serde"] }
 serde = { version = "1.0.196", features = ["derive"] }
 serde-aux = { version = "4.4.0", default-features = false }
-sha2 = "0.10.8"
 sqlx = { version = "0.7.3", features = ["macros", "migrate", "postgres", "time", "runtime-tokio", "tls-native-tls", "uuid"], default-features = false }
 thiserror = "1.0.58"
 time = { version = "0.3.34", features = ["macros", "serde"] }
@@ -42,7 +39,6 @@ tracing-bunyan-formatter = "0.3.9"
 tracing-log = "0.2.0"
 tracing-subscriber = { version = "0.3.18", features = ["env-filter"] }
 unicode-segmentation = "1.11.0"
-urlencoding = "2.1.3"
 uuid = { version = "1.7.0", features = ["v4"] }
 validator = "0.16.1"
 

src/app_state.rs

@@ -1,12 +1,18 @@
 use crate::email_client::EmailClient;
-use axum::http::Uri;
-use secrecy::Secret;
+use axum::{extract::FromRef, http::Uri};
+use axum_extra::extract::cookie::Key;
 use sqlx::PgPool;
 
 #[derive(Clone)]
 pub struct AppState {
     pub db_pool: PgPool,
     pub email_client: EmailClient,
     pub base_url: Uri,
-    pub hmac_secret: Secret<String>,
+    pub cookie_key: Key,
+}
+
+impl FromRef<AppState> for Key {
+    fn from_ref(state: &AppState) -> Self {
+        state.cookie_key.clone()
+    }
 }

src/routes/login/action.rs

@@ -8,17 +8,20 @@ use axum::{
     response::{IntoResponse, Redirect, Response},
     Form,
 };
-use hmac::{Hmac, Mac};
-use secrecy::{ExposeSecret, Secret};
+use axum_extra::extract::{
+    cookie::{Cookie, SameSite},
+    SignedCookieJar,
+};
+use secrecy::Secret;
 use serde::Deserialize;
-use urlencoding::Encoded;
 
 #[tracing::instrument(
-    skip(app_state, form),
+    skip(app_state, form, jar),
     fields(username = tracing::field::Empty, user_id = tracing::field::Empty)
 )]
 pub(super) async fn login(
     State(app_state): State<AppState>,
+    jar: SignedCookieJar,
     Form(form): Form<FormData>,
 ) -> Result<Redirect, LoginError> {
     tracing::Span::current().record("username", &tracing::field::display(&form.username));
@@ -32,17 +35,7 @@ pub(super) async fn login(
     )
     .await
     .map_err(|e| match e {
-        AuthError::InvalidCredentials(_) => {
-            let error = format!("error={}", Encoded::new(e.to_string()));
-            let tag = format!("tag={:x}", {
-                let secret: &[u8] = app_state.hmac_secret.expose_secret().as_bytes();
-                let mut mac = Hmac::<sha2::Sha256>::new_from_slice(secret).unwrap();
-                mac.update(error.as_bytes());
-                mac.finalize().into_bytes()
-            });
-
-            LoginError::AuthError(e.into(), Redirect::to(&format!("/login?{error}&{tag}")))
-        }
+        AuthError::InvalidCredentials(_) => LoginError::AuthErrorWithResponse(e.into(), jar),
         AuthError::UnexpectedError(_) => LoginError::UnexpectedError(e.into()),
     })?;
 
@@ -60,18 +53,37 @@ pub(super) struct FormData {
 #[derive(Debug, thiserror::Error)]
 pub(super) enum LoginError {
     #[error("Authentication failed")]
-    AuthError(#[source] anyhow::Error, Redirect),
+    AuthErrorWithResponse(#[source] anyhow::Error, SignedCookieJar),
+    #[error("Authentication failed")]
+    AuthError(#[source] anyhow::Error),
     #[error("Something went wrong")]
     UnexpectedError(#[from] anyhow::Error),
 }
 
 impl IntoResponse for LoginError {
     fn into_response(self) -> Response {
-        tracing::error!("{:#?}", self);
-
         match self {
-            Self::AuthError(_, redirect) => redirect.into_response(),
-            Self::UnexpectedError(_) => StatusCode::INTERNAL_SERVER_ERROR.into_response(),
+            Self::AuthErrorWithResponse(e, jar) => {
+                let error = Self::AuthError(e);
+                tracing::error!("{:#?}", error);
+
+                let jar = jar.add(
+                    Cookie::build(("_flash", error.to_string()))
+                        .http_only(true)
+                        .same_site(SameSite::Strict),
+                );
+                let redirect = Redirect::to("/login");
+
+                (jar, redirect).into_response()
+            }
+            Self::AuthError(_) => {
+                tracing::error!("{:#?}", self);
+                StatusCode::UNAUTHORIZED.into_response()
+            }
+            Self::UnexpectedError(_) => {
+                tracing::error!("{:#?}", self);
+                StatusCode::INTERNAL_SERVER_ERROR.into_response()
+            }
         }
     }
 }