bugfix: equalise login response time across user-existence branches (0.34.1)

A login attempt against a non-existent username returned 401 in <1ms,
while the wrong-password branch ran argon2 verify (~50-100ms). Timing
the difference let an attacker enumerate valid usernames without ever
seeing a successful response. Run verify_password against a fixed
dummy argon2id hash on the no-user branch so both paths spend the
same compute.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.gitea/README.md

@@ -0,0 +1,71 @@
+# Gitea Actions
+
+The [`deploy`](workflows/deploy.yml) workflow runs on every push to `main`
+(and via manual `workflow_dispatch`). It tests, builds, pushes the images
+to a private registry, and rolls the stack over by SSH on the target host.
+
+## Required secrets
+
+Set under *Repo Settings → Actions → Secrets*:
+
+| Name                 | Example                  | Purpose                                                          |
+| -------------------- | ------------------------ | ---------------------------------------------------------------- |
+| `REGISTRY_URL`       | `registry.example.com`   | Registry host. No scheme, no trailing slash.                     |
+| `REGISTRY_USERNAME`  | `mangalord-ci`           | `docker login` user.                                             |
+| `REGISTRY_PASSWORD`  | `<token>`                | `docker login` token/password.                                   |
+| `SSH_HOST`           | `mangalord.example.com`  | Deploy target hostname/IP.                                       |
+| `SSH_USER`           | `deploy`                 | SSH user on the target (must be in the `docker` group).          |
+| `SSH_PRIVATE_KEY`    | `-----BEGIN OPENSSH...`  | Private key authorised in the target user's `authorized_keys`.   |
+| `SSH_PORT`           | `22`                     | Optional. Defaults to `22` if unset.                             |
+
+## Required variables
+
+Set under *Repo Settings → Actions → Variables* (not secrets — they appear
+in logs):
+
+| Name          | Example                  | Purpose                                                                |
+| ------------- | ------------------------ | ---------------------------------------------------------------------- |
+| `DEPLOY_PATH` | `/srv/mangalord`         | Directory on target holding `docker-compose.yml`, `.env`, and the prod overlay. |
+
+## One-time host setup
+
+The workflow assumes the deploy target already has:
+
+1. Docker + Docker Compose v2 installed and the `SSH_USER` in the `docker` group.
+2. `$DEPLOY_PATH/docker-compose.yml` (copy of the repo's [docker-compose.yml](../docker-compose.yml)).
+3. `$DEPLOY_PATH/docker-compose.prod.yml` (copy of the repo's [docker-compose.prod.yml](../docker-compose.prod.yml)).
+4. `$DEPLOY_PATH/.env` populated from [.env.example](../.env.example) with production values (real `POSTGRES_PASSWORD`, `COOKIE_SECURE=true`, etc.).
+
+Bootstrap once:
+
+```bash
+ssh deploy@mangalord.example.com
+sudo mkdir -p /srv/mangalord && sudo chown deploy:deploy /srv/mangalord
+cd /srv/mangalord
+# place docker-compose.yml, docker-compose.prod.yml, and .env here
+```
+
+The first workflow run will pull the images, bring the stack up, and run
+the embedded migrations on startup.
+
+## Image tags
+
+Every push produces three tags per image:
+
+- `mangalord-{backend,frontend}:latest`
+- `mangalord-{backend,frontend}:<git-sha>` — used by the deploy job; lets
+  you pin a deploy to a specific commit
+- `mangalord-{backend,frontend}:<version>` — the version from
+  [backend/Cargo.toml](../backend/Cargo.toml) (verified in lockstep with
+  [frontend/package.json](../frontend/package.json))
+
+## Rollback
+
+SSH to the target, set `IMAGE_TAG` to a previous commit SHA, and re-up:
+
+```bash
+cd /srv/mangalord
+export REGISTRY_URL=registry.example.com
+export IMAGE_TAG=<previous-sha>
+docker compose -f docker-compose.yml -f docker-compose.prod.yml up -d
+```

.gitea/workflows/deploy.yml

@@ -0,0 +1,144 @@
+name: deploy
+
+on:
+  push:
+    branches: [main]
+  workflow_dispatch:
+
+jobs:
+  test-backend:
+    runs-on: ubuntu-latest
+    container:
+      image: rust:1-slim
+    services:
+      postgres:
+        image: postgres:16-alpine
+        env:
+          POSTGRES_USER: mangalord
+          POSTGRES_PASSWORD: mangalord
+          POSTGRES_DB: mangalord
+        options: >-
+          --health-cmd "pg_isready -U mangalord"
+          --health-interval 5s
+          --health-timeout 5s
+          --health-retries 10
+    env:
+      DATABASE_URL: postgres://mangalord:mangalord@postgres:5432/mangalord
+    steps:
+      - uses: actions/checkout@v4
+      - name: Install build deps
+        run: |
+          apt-get update
+          apt-get install -y --no-install-recommends pkg-config libssl-dev ca-certificates
+      - name: Cache cargo registry and target
+        uses: actions/cache@v4
+        with:
+          path: |
+            ~/.cargo/registry
+            ~/.cargo/git
+            backend/target
+          key: cargo-${{ runner.os }}-${{ hashFiles('backend/Cargo.lock') }}
+          restore-keys: |
+            cargo-${{ runner.os }}-
+      - name: cargo test
+        working-directory: backend
+        run: cargo test --locked
+
+  test-frontend:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-node@v4
+        with:
+          node-version: '22'
+          cache: npm
+          cache-dependency-path: frontend/package-lock.json
+      - name: npm ci
+        working-directory: frontend
+        run: npm ci
+      - name: vitest
+        working-directory: frontend
+        run: npm test
+
+  build-and-push:
+    runs-on: ubuntu-latest
+    needs: [test-backend, test-frontend]
+    outputs:
+      image_tag: ${{ steps.meta.outputs.image_tag }}
+      version: ${{ steps.meta.outputs.version }}
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Resolve image tags
+        id: meta
+        run: |
+          version="$(grep -m1 '^version' backend/Cargo.toml | cut -d'"' -f2)"
+          frontend_version="$(grep -m1 '"version"' frontend/package.json | cut -d'"' -f4)"
+          if [ "$version" != "$frontend_version" ]; then
+            echo "Version mismatch: backend=$version frontend=$frontend_version" >&2
+            exit 1
+          fi
+          echo "image_tag=${GITHUB_SHA}" >> "$GITHUB_OUTPUT"
+          echo "version=${version}" >> "$GITHUB_OUTPUT"
+
+      - uses: docker/setup-buildx-action@v3
+
+      - name: docker login
+        uses: docker/login-action@v3
+        with:
+          registry: ${{ secrets.REGISTRY_URL }}
+          username: ${{ secrets.REGISTRY_USERNAME }}
+          password: ${{ secrets.REGISTRY_PASSWORD }}
+
+      - name: Build & push backend
+        uses: docker/build-push-action@v5
+        with:
+          context: ./backend
+          push: true
+          tags: |
+            ${{ secrets.REGISTRY_URL }}/mangalord-backend:latest
+            ${{ secrets.REGISTRY_URL }}/mangalord-backend:${{ steps.meta.outputs.image_tag }}
+            ${{ secrets.REGISTRY_URL }}/mangalord-backend:${{ steps.meta.outputs.version }}
+          cache-from: type=gha,scope=backend
+          cache-to: type=gha,mode=max,scope=backend
+
+      - name: Build & push frontend
+        uses: docker/build-push-action@v5
+        with:
+          context: ./frontend
+          push: true
+          tags: |
+            ${{ secrets.REGISTRY_URL }}/mangalord-frontend:latest
+            ${{ secrets.REGISTRY_URL }}/mangalord-frontend:${{ steps.meta.outputs.image_tag }}
+            ${{ secrets.REGISTRY_URL }}/mangalord-frontend:${{ steps.meta.outputs.version }}
+          cache-from: type=gha,scope=frontend
+          cache-to: type=gha,mode=max,scope=frontend
+
+  deploy:
+    runs-on: ubuntu-latest
+    needs: build-and-push
+    steps:
+      - name: SSH deploy
+        uses: appleboy/ssh-action@v1.0.3
+        with:
+          host: ${{ secrets.SSH_HOST }}
+          username: ${{ secrets.SSH_USER }}
+          key: ${{ secrets.SSH_PRIVATE_KEY }}
+          port: ${{ secrets.SSH_PORT || 22 }}
+          envs: REGISTRY_URL,REGISTRY_USERNAME,REGISTRY_PASSWORD,IMAGE_TAG,DEPLOY_PATH
+          script_stop: true
+          script: |
+            set -euo pipefail
+            cd "$DEPLOY_PATH"
+            echo "$REGISTRY_PASSWORD" | docker login "$REGISTRY_URL" -u "$REGISTRY_USERNAME" --password-stdin
+            export REGISTRY_URL IMAGE_TAG
+            docker compose -f docker-compose.yml -f docker-compose.prod.yml pull
+            docker compose -f docker-compose.yml -f docker-compose.prod.yml up -d
+            docker image prune -f
+            docker logout "$REGISTRY_URL"
+        env:
+          REGISTRY_URL: ${{ secrets.REGISTRY_URL }}
+          REGISTRY_USERNAME: ${{ secrets.REGISTRY_USERNAME }}
+          REGISTRY_PASSWORD: ${{ secrets.REGISTRY_PASSWORD }}
+          IMAGE_TAG: ${{ needs.build-and-push.outputs.image_tag }}
+          DEPLOY_PATH: ${{ vars.DEPLOY_PATH }}

backend/Cargo.lock

@@ -1470,7 +1470,7 @@ checksum = "c41e0c4fef86961ac6d6f8a82609f55f31b05e4fce149ac5710e439df7619ba4"
 
 [[package]]
 name = "mangalord"
-version = "0.33.0"
+version = "0.34.0"
 dependencies = [
  "anyhow",
  "argon2",

backend/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "mangalord"
-version = "0.33.0"
+version = "0.34.1"
 edition = "2021"
 default-run = "mangalord"
 

backend/src/api/auth.rs

@@ -4,6 +4,8 @@
 //! expire naturally rather than being explicitly invalidated, so other
 //! devices keep their existing logins).
 
+use std::sync::OnceLock;
+
 use axum::extract::{Path, State};
 use axum::http::StatusCode;
 use axum::response::IntoResponse;
@@ -102,9 +104,15 @@ async fn login(
         ));
     }
 
-    let user = repo::user::find_by_username(&state.db, username)
+    let user = repo::user::find_by_username(&state.db, username).await?;
-        .await?
+    let Some(user) = user else {
-        .ok_or(AppError::Unauthenticated)?;
+        // No such user. Run argon2 against a stable dummy hash so the
+        // response time matches the wrong-password branch — otherwise
+        // an attacker can enumerate usernames by timing the no-user
+        // 401 against the wrong-password 401.
+        let _ = verify_password(&input.password, dummy_password_hash());
+        return Err(AppError::Unauthenticated);
+    };
     if !verify_password(&input.password, &user.password_hash) {
         return Err(AppError::Unauthenticated);
     }
@@ -113,6 +121,21 @@ async fn login(
     Ok((StatusCode::OK, jar, Json(AuthResponse { user })))
 }
 
+/// Lazily-computed argon2 hash used to equalise login response time
+/// across the "no such user" and "wrong password" branches. Computing
+/// it once (on the first login of the process) is enough — the hash is
+/// never compared against a real password, only used to force argon2
+/// to do the same amount of work it would for a real verify.
+fn dummy_password_hash() -> &'static str {
+    static DUMMY: OnceLock<String> = OnceLock::new();
+    DUMMY
+        .get_or_init(|| {
+            crate::auth::password::hash_password("login-timing-equaliser")
+                .expect("hash_password on a fixed input cannot fail")
+        })
+        .as_str()
+}
+
 async fn logout(
     State(state): State<AppState>,
     jar: CookieJar,

backend/tests/api_auth.rs

@@ -567,6 +567,91 @@ async fn user_a_cannot_delete_user_b_token(pool: PgPool) {
     assert_eq!(resp.status(), StatusCode::NO_CONTENT);
 }
 
+/// Username enumeration via login response time: an attacker probes
+/// for valid usernames by measuring how long /auth/login takes. Before
+/// the equalisation fix, the no-user branch returned 401 in <1 ms
+/// while the wrong-password branch took ~50-100 ms (the argon2 verify
+/// cost). This test asserts the no-user branch now spends at least
+/// some meaningful fraction of the wrong-password branch's time.
+///
+/// Tolerance is intentionally loose so CI variance doesn't flap the
+/// test. The unequalised gap is large enough (~50x) that even a noisy
+/// CI run with a 5x slack still catches it.
+#[sqlx::test(migrations = "./migrations")]
+async fn login_no_user_branch_runs_argon2_for_timing_equalisation(pool: PgPool) {
+    use std::time::Instant;
+
+    let h = common::harness(pool);
+
+    // Register the victim user so the wrong-password branch has a real
+    // argon2 hash to verify against.
+    let _ = h
+        .app
+        .clone()
+        .oneshot(common::post_json(
+            "/api/v1/auth/register",
+            json!({ "username": "victim", "password": "hunter2hunter2" }),
+        ))
+        .await
+        .unwrap();
+
+    // Warm-up: first login of the process initialises the dummy hash
+    // lazily. Skip that cost when measuring.
+    let _ = h
+        .app
+        .clone()
+        .oneshot(common::post_json(
+            "/api/v1/auth/login",
+            json!({ "username": "victim", "password": "wrong" }),
+        ))
+        .await
+        .unwrap();
+    let _ = h
+        .app
+        .clone()
+        .oneshot(common::post_json(
+            "/api/v1/auth/login",
+            json!({ "username": "ghost", "password": "wrong" }),
+        ))
+        .await
+        .unwrap();
+
+    // Median-of-N is more stable than a single sample.
+    async fn sample_min(
+        app: &axum::Router,
+        username: &str,
+        n: u32,
+    ) -> std::time::Duration {
+        let mut samples = Vec::with_capacity(n as usize);
+        for _ in 0..n {
+            let req = common::post_json(
+                "/api/v1/auth/login",
+                json!({ "username": username, "password": "wrong-guess" }),
+            );
+            let t = Instant::now();
+            let resp = app.clone().oneshot(req).await.unwrap();
+            let d = t.elapsed();
+            assert_eq!(resp.status(), StatusCode::UNAUTHORIZED);
+            samples.push(d);
+        }
+        // Use the minimum: it's the floor that argon2 takes, robust
+        // against unrelated stalls (DB connection acquisition, etc.).
+        *samples.iter().min().unwrap()
+    }
+
+    let wrong_pwd = sample_min(&h.app, "victim", 3).await;
+    let no_user = sample_min(&h.app, "ghost", 3).await;
+
+    // 5x slack: argon2 dominates both branches, so they should be
+    // within an order of magnitude. Unequalised, no_user would be
+    // ~50-100x faster. Asserting "no_user >= wrong_pwd / 5" catches
+    // the bug without being flaky in CI.
+    assert!(
+        no_user * 5 >= wrong_pwd,
+        "login timing leaks user existence: no_user={no_user:?}, wrong_pwd={wrong_pwd:?}"
+    );
+}
+
 #[sqlx::test(migrations = "./migrations")]
 async fn delete_unknown_token_is_404(pool: PgPool) {
     let h = common::harness(pool);

docker-compose.prod.yml

@@ -0,0 +1,22 @@
+# Production overlay: layer on top of docker-compose.yml on the deploy
+# host so the backend and frontend run from pre-built registry images
+# instead of building locally.
+#
+#   docker compose -f docker-compose.yml -f docker-compose.prod.yml up -d
+#
+# REGISTRY_URL and IMAGE_TAG are injected by .gitea/workflows/deploy.yml
+# at deploy time. IMAGE_TAG defaults to `latest` so a manual
+# `docker compose ... up -d` on the host still works.
+
+services:
+  backend:
+    build: !reset null
+    image: ${REGISTRY_URL}/mangalord-backend:${IMAGE_TAG:-latest}
+    pull_policy: always
+    restart: unless-stopped
+
+  frontend:
+    build: !reset null
+    image: ${REGISTRY_URL}/mangalord-frontend:${IMAGE_TAG:-latest}
+    pull_policy: always
+    restart: unless-stopped

frontend/package.json

@@ -1,6 +1,6 @@
 {
   "name": "mangalord-frontend",
-  "version": "0.33.0",
+  "version": "0.34.1",
   "private": true,
   "type": "module",
   "scripts": {