fix: session boot on POST path, consolidate rate limiter via checkKey()

TODO.md

@@ -5,3 +5,5 @@
 - [x] Fix regex delimiter clash (`/` inside `[...]` broke the pattern) → switched to `#` delimiter
 - [x] Add PHP dev server router for /partage/<slug> URL rewriting
 - [x] Add nginx location block for /partage/ pretty URLs
+- [x] Fix POST path missing App::boot() (session not started before submission handler)
+- [x] Fix rate limiter: was instantiating RateLimit then ignoring it, reimplementing inline; added checkKey() to RateLimit and use it

public/partage/index.php

@@ -29,6 +29,9 @@ if (!preg_match('#^\d{8}-[A-Z0-9+/]{8}$#', $slug)) {
     exit;
 }
 
+// Boot for all requests: starts session, initialises DB, ensures CSRF token.
+App::boot();
+
 // ── POST: form submission ─────────────────────────────────────────────────────
 if ($_SERVER['REQUEST_METHOD'] === 'POST' && $action === 'submit') {
     handleShareLinkSubmission($slug);
@@ -36,7 +39,6 @@ if ($_SERVER['REQUEST_METHOD'] === 'POST' && $action === 'submit') {
 }
 
 // ── GET: render form ─────────────────────────────────────────────────────────
-App::boot(); // boot database + CSRF
 
 require_once APP_ROOT . '/src/ShareLink.php';
 $shareLinkModel = new ShareLink(Database::getInstance());
@@ -480,7 +482,11 @@ function renderShareLinkForm(string $slug, array $link): void
  */
 function handleShareLinkSubmission(string $slug): void
 {
+    // Session already started by App::boot() on the GET path; start here
+    // only if somehow not yet active (e.g. direct POST without prior GET).
+    if (session_status() === PHP_SESSION_NONE) {
         session_start();
+    }
 
     require_once APP_ROOT . '/src/ShareLink.php';
     require_once APP_ROOT . '/src/RateLimit.php';
@@ -496,33 +502,16 @@ function handleShareLinkSubmission(string $slug): void
     }
 
     // ── Rate limiting ────────────────────────────────────────────────────────
-    // Allow max 5 submissions per IP per 10 minutes (per share link)
+    // 5 submissions per IP per 10 minutes, keyed per share link.
     $rateLimitCacheDir = STORAGE_ROOT . '/cache/rate_limit';
-    if (!is_dir($rateLimitCacheDir)) {
-        @mkdir($rateLimitCacheDir, 0755, true);
-    }
     $shareRateLimitId  = 'share_' . $slug . '_' . ($_SERVER['REMOTE_ADDR'] ?? 'unknown');
     $rateLimit         = new RateLimit(5, 600, $rateLimitCacheDir);
 
-    // Use a custom identifier based on slug + IP so each share link is rate-limited independently
-    $rateLimitFile = $rateLimitCacheDir . '/' . md5($shareRateLimitId) . '.json';
-    $data = [];
-    if (file_exists($rateLimitFile)) {
-        $content = file_get_contents($rateLimitFile);
-        $data = json_decode($content, true) ?? [];
-    }
-    $now = time();
-    $data = array_filter($data, fn($ts) => ($now - $ts) < 600);
-
-    if (count($data) >= 5) {
+    if (!$rateLimit->checkKey($shareRateLimitId)) {
         $_SESSION['_flash_error'] = 'Trop de tentatives. Veuillez réessayer plus tard.';
         header('Location: /partage/' . urlencode($slug));
         exit;
     }
-    $data[] = $now;
-    if (is_writable($rateLimitCacheDir)) {
-        file_put_contents($rateLimitFile, json_encode($data));
-    }
     // ── End rate limiting ────────────────────────────────────────────────────
 
     // Check password verification if link has a password

src/RateLimit.php

@@ -50,6 +50,35 @@ class RateLimit {
         return $this->cacheDir . '/' . md5($identifier) . '.json';
     }
 
+    /**
+     * Check and record a hit for an arbitrary string key.
+     * Useful when the caller wants a compound key (e.g. slug + IP).
+     *
+     * @return bool True if allowed, false if rate limit exceeded
+     */
+    public function checkKey(string $key): bool {
+        $file = $this->getCacheFile($key);
+
+        $data = [];
+        if (file_exists($file)) {
+            $data = json_decode(file_get_contents($file), true) ?? [];
+        }
+
+        $now  = time();
+        $data = array_values(array_filter($data, fn($ts) => ($now - $ts) < $this->timeWindow));
+
+        if (count($data) >= $this->maxRequests) {
+            return false;
+        }
+
+        $data[] = $now;
+        if (is_dir($this->cacheDir) && is_writable($this->cacheDir)) {
+            file_put_contents($file, json_encode($data));
+        }
+
+        return true;
+    }
+
     /**
      * Check if client has exceeded rate limit
      * @return bool True if allowed, false if rate limit exceeded