fix(security): cross-event authz, SSE ticket flow, account hardening, audit logs

Follow-up to the comprehensive code review. Five batches:

1. Cross-event authorization: host_delete_upload, unban_user, and
   host_delete_comment now scope by auth.event_id. Adds
   Upload::find_by_id_and_event / soft_delete_in_event and a
   Comment::soft_delete_in_event variant that joins through upload.

2. Token exposure: SSE auth no longer puts the JWT in the URL.
   New /api/v1/stream/ticket endpoint mints a short-lived single-use
   ticket bound to the session; the EventSource passes ?ticket=...
   instead. Refuse to start in APP_ENV=production with the dev JWT
   sentinel; warn loudly otherwise.

3. Account hardening: per-IP+name rate limit on /recover (mitigates
   targeted lockout DoS), per-IP rate limit on /admin/login, random
   32-char admin recovery PIN (replaces "0000"), structured tracing
   events for wrong PIN, lockout, failed admin login, ban/unban/role
   change/pin-reset/host-delete.

4. DoS / correctness: comment listing paginated (LIMIT 50 + ?before=
   cursor), hashtag extraction whitelisted to ASCII alnum+underscore
   (≤40 chars) with unit tests, display_name / caption / comment body
   length validated in chars rather than bytes.

5. Cleanup: session-touch failures now logged, DATABASE_MAX_CONNECTIONS
   env var (default 10).

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

backend/src/handlers/host.rs

@@ -120,18 +120,38 @@ pub async fn ban_user(
     .execute(&state.pool)
     .await?;
 
+    tracing::info!(
+        actor_user_id = %auth.user_id,
+        target_user_id = %user_id,
+        event_id = %auth.event_id,
+        hide_uploads = body.hide_uploads,
+        "host: ban_user"
+    );
+
     Ok(StatusCode::NO_CONTENT)
 }
 
 pub async fn unban_user(
     State(state): State<AppState>,
-    RequireHost(_auth): RequireHost,
+    RequireHost(auth): RequireHost,
     Path(user_id): Path<Uuid>,
 ) -> Result<StatusCode, AppError> {
-    sqlx::query("UPDATE \"user\" SET is_banned = FALSE WHERE id = $1")
-        .bind(user_id)
-        .execute(&state.pool)
-        .await?;
+    let result = sqlx::query(
+        "UPDATE \"user\" SET is_banned = FALSE WHERE id = $1 AND event_id = $2",
+    )
+    .bind(user_id)
+    .bind(auth.event_id)
+    .execute(&state.pool)
+    .await?;
+    if result.rows_affected() == 0 {
+        return Err(AppError::NotFound("Benutzer nicht gefunden.".into()));
+    }
+    tracing::info!(
+        actor_user_id = %auth.user_id,
+        target_user_id = %user_id,
+        event_id = %auth.event_id,
+        "host: unban_user"
+    );
     Ok(StatusCode::NO_CONTENT)
 }
 
@@ -181,6 +201,14 @@ pub async fn set_role(
         .bind(auth.event_id)
         .execute(&state.pool)
         .await?;
+    tracing::info!(
+        actor_user_id = %auth.user_id,
+        target_user_id = %user_id,
+        event_id = %auth.event_id,
+        old_role = %target.0,
+        new_role,
+        "host: set_role"
+    );
     Ok(StatusCode::NO_CONTENT)
 }
 
@@ -251,38 +279,61 @@ pub async fn reset_user_pin(
         serde_json::json!({ "user_id": user_id }).to_string(),
     ));
 
+    tracing::info!(
+        actor_user_id = %auth.user_id,
+        target_user_id = %user_id,
+        event_id = %auth.event_id,
+        "host: reset_user_pin"
+    );
+
     Ok(Json(PinResetResponse { pin }))
 }
 
 pub async fn host_delete_upload(
     State(state): State<AppState>,
-    RequireHost(_auth): RequireHost,
+    RequireHost(auth): RequireHost,
     Path(upload_id): Path<Uuid>,
 ) -> Result<StatusCode, AppError> {
-    let upload = Upload::find_by_id(&state.pool, upload_id)
+    let upload = Upload::find_by_id_and_event(&state.pool, upload_id, auth.event_id)
         .await?
         .ok_or_else(|| AppError::NotFound("Upload nicht gefunden.".into()))?;
 
-    Upload::soft_delete(&state.pool, upload_id).await?;
+    let deleted = Upload::soft_delete_in_event(&state.pool, upload_id, auth.event_id).await?;
+    if !deleted {
+        return Err(AppError::NotFound("Upload nicht gefunden.".into()));
+    }
 
     let _ = state.sse_tx.send(SseEvent::new(
         "upload-deleted",
         serde_json::json!({ "upload_id": upload.id }).to_string(),
     ));
 
+    tracing::info!(
+        actor_user_id = %auth.user_id,
+        event_id = %auth.event_id,
+        upload_id = %upload.id,
+        "host: host_delete_upload"
+    );
+
     Ok(StatusCode::NO_CONTENT)
 }
 
 pub async fn host_delete_comment(
     State(state): State<AppState>,
-    RequireHost(_auth): RequireHost,
+    RequireHost(auth): RequireHost,
     Path(comment_id): Path<Uuid>,
 ) -> Result<StatusCode, AppError> {
-    Comment::find_by_id(&state.pool, comment_id)
-        .await?
-        .ok_or_else(|| AppError::NotFound("Kommentar nicht gefunden.".into()))?;
-
-    Comment::soft_delete(&state.pool, comment_id).await?;
+    let deleted =
+        Comment::soft_delete_in_event(&state.pool, comment_id, auth.event_id).await?;
+    if !deleted {
+        return Err(AppError::NotFound("Kommentar nicht gefunden.".into()));
+    }
+    tracing::info!(
+        actor_user_id = %auth.user_id,
+        event_id = %auth.event_id,
+        comment_id = %comment_id,
+        "host: host_delete_comment"
+    );
     Ok(StatusCode::NO_CONTENT)
 }
 

backend/src/handlers/social.rs

@@ -1,6 +1,7 @@
-use axum::extract::{Path, State};
+use axum::extract::{Path, Query, State};
 use axum::http::StatusCode;
 use axum::Json;
+use chrono::{DateTime, Utc};
 use serde::Deserialize;
 use uuid::Uuid;
 
@@ -51,12 +52,24 @@ pub async fn toggle_like(
     Ok(StatusCode::NO_CONTENT)
 }
 
+#[derive(Deserialize, Default)]
+pub struct ListCommentsQuery {
+    /// RFC3339 timestamp — return only comments older than this. Pass the
+    /// `created_at` of the oldest currently-loaded comment to fetch the next
+    /// older page.
+    pub before: Option<DateTime<Utc>>,
+}
+
+const COMMENT_PAGE_SIZE: i64 = 50;
+
 pub async fn list_comments(
     State(state): State<AppState>,
     _auth: AuthUser,
     Path(upload_id): Path<Uuid>,
+    Query(q): Query<ListCommentsQuery>,
 ) -> Result<Json<Vec<CommentDto>>, AppError> {
-    let comments = Comment::list_for_upload(&state.pool, upload_id).await?;
+    let comments =
+        Comment::list_for_upload(&state.pool, upload_id, q.before, COMMENT_PAGE_SIZE).await?;
     Ok(Json(comments))
 }
 
@@ -79,7 +92,8 @@ pub async fn add_comment(
     }
 
     let text = body.body.trim();
-    if text.is_empty() || text.len() > 500 {
+    let text_chars = text.chars().count();
+    if text_chars == 0 || text_chars > 500 {
         return Err(AppError::BadRequest(
             "Kommentar muss zwischen 1 und 500 Zeichen lang sein.".into(),
         ));

backend/src/handlers/sse.rs

@@ -3,32 +3,51 @@ use std::time::Duration;
 
 use axum::extract::{Query, State};
 use axum::response::sse::{Event, KeepAlive, Sse};
+use axum::Json;
 use futures::stream::Stream;
-use serde::Deserialize;
+use serde::{Deserialize, Serialize};
 use tokio_stream::wrappers::BroadcastStream;
 use tokio_stream::StreamExt;
 
-use crate::auth::jwt;
+use crate::auth::middleware::AuthUser;
 use crate::error::AppError;
 use crate::models::session::Session;
 use crate::state::AppState;
 
 #[derive(Deserialize)]
 pub struct SseQuery {
-    pub token: String,
+    pub ticket: String,
 }
 
-/// SSE stream endpoint. Accepts JWT via query param since EventSource
-/// doesn't support custom headers.
+#[derive(Serialize)]
+pub struct StreamTicketResponse {
+    pub ticket: String,
+}
+
+/// Mint a short-lived single-use SSE ticket. The browser's `EventSource` cannot
+/// send an `Authorization` header, so the alternative used to be passing the JWT
+/// as `?token=...` — which leaks the bearer token into access logs, referer
+/// headers, and browser history. The client now exchanges its Bearer token for
+/// an opaque ticket via this endpoint and passes that on the stream open.
+pub async fn issue_ticket(
+    State(state): State<AppState>,
+    auth: AuthUser,
+) -> Json<StreamTicketResponse> {
+    let ticket = state.sse_tickets.issue(auth.token_hash);
+    Json(StreamTicketResponse { ticket })
+}
+
+/// SSE stream endpoint. Authenticates via a single-use ticket (see
+/// [`issue_ticket`]) — never the raw JWT.
 pub async fn stream(
     State(state): State<AppState>,
     Query(q): Query<SseQuery>,
 ) -> Result<Sse<impl Stream<Item = Result<Event, Infallible>>>, AppError> {
-    // Verify token
-    let _claims = jwt::verify_token(&q.token, &state.config.jwt_secret)
-        .map_err(|_| AppError::Unauthorized("Token ungültig.".into()))?;
+    let token_hash = state
+        .sse_tickets
+        .consume(&q.ticket)
+        .ok_or_else(|| AppError::Unauthorized("Ticket ungültig oder abgelaufen.".into()))?;
 
-    let token_hash = jwt::hash_token(&q.token);
     Session::find_by_token_hash(&state.pool, &token_hash)
         .await
         .map_err(|e| AppError::Internal(e.into()))?

backend/src/handlers/upload.rs

@@ -99,9 +99,11 @@ pub async fn upload(
     let mime = content_type.unwrap_or_else(|| "application/octet-stream".to_string());
     let size = data.len() as i64;
 
-    // Validate caption length
+    // Validate caption length. Counted in chars (code points) to match the
+    // "Zeichen" wording in the error message — `.len()` would be bytes and
+    // reject perfectly valid German/emoji captions early.
     if let Some(ref cap) = caption {
-        if cap.len() > MAX_CAPTION_LENGTH {
+        if cap.chars().count() > MAX_CAPTION_LENGTH {
             return Err(AppError::BadRequest(format!(
                 "Beschreibung ist zu lang. Maximum: {} Zeichen.",
                 MAX_CAPTION_LENGTH