Fix ladl.link transfer QR redirect loop causing 500 errors.

Proxy transfer paths directly to transfer.ladill.com and stop following ladl.link redirects server-side so recipient links resolve.

Co-authored-by: Cursor <cursoragent@cursor.com>

app/Services/Link/LinkPlatformProxy.php

@@ -8,45 +8,40 @@ use Illuminate\Support\Facades\Http;
 use Symfony\Component\HttpFoundation\Response;
 
 /**
- * Proxies ladl.link ecosystem paths to the platform QR resolver (/q/* on ladill.com).
+ * Proxies ladl.link ecosystem paths to the platform QR resolver (/q/* on ladill.com)
- * The browser stays on ladl.link; resolution happens server-side.
+ * or directly to satellite apps (e.g. transfer.ladill.com). The browser stays on
+ * ladl.link; resolution happens server-side without redirect loops.
  */
 class LinkPlatformProxy
 {
+    public const INTERNAL_HEADER = 'X-Ladill-Internal';
+
     public function forward(Request $request, string $slug, ?string $path = null): Response
     {
+        $normalizedPath = $path !== null ? ltrim($path, '/') : '';
+
+        if ($normalizedPath === 'transfer' || str_starts_with($normalizedPath, 'transfer/')) {
+            return $this->fetch(
+                $request,
+                rtrim($this->transferBaseUrl(), '/').'/q/'.$slug.'/'.$normalizedPath,
+            );
+        }
+
         $platform = rtrim((string) config('app.platform_url', 'https://ladill.com'), '/');
         $target = $platform.'/q/'.$slug;
-        if ($path !== null && $path !== '') {
+        if ($normalizedPath !== '') {
-            $target .= '/'.ltrim($path, '/');
+            $target .= '/'.$normalizedPath;
-        }
-        if ($qs = $request->getQueryString()) {
-            $target .= '?'.$qs;
         }
 
-        $method = strtoupper($request->method());
+        $response = $this->fetch($request, $target);
-        $followRedirects = $method === 'GET' || $method === 'HEAD';
-        $client = Http::withOptions([
-            'allow_redirects' => $followRedirects ? ['max' => 5] : false,
-        ])->timeout(15);
-
-        $pending = match ($method) {
-            'POST' => $client->withHeaders($this->forwardHeaders($request))->asForm()->post($target, $request->post()),
-            'PATCH' => $client->withHeaders($this->forwardHeaders($request))->patch($target, $request->all()),
-            'DELETE' => $client->withHeaders($this->forwardHeaders($request))->delete($target),
-            default => $client->withHeaders($this->forwardHeaders($request))->get($target),
-        };
-
-        $upstream = $pending->toPsrResponse();
-        $response = new Response(
-            (string) $upstream->getBody(),
-            $upstream->getStatusCode(),
-            $this->sanitizeHeaders($upstream->getHeaders())
-        );
 
         if ($response->isRedirection()) {
             $location = $response->headers->get('Location');
             if (is_string($location)) {
+                if ($followUp = $this->followLadillLinkRedirect($request, $slug, $location)) {
+                    return $followUp;
+                }
+
                 $response->headers->set('Location', $this->rewriteLocation($location, $slug));
             }
         }
@@ -54,6 +49,62 @@ class LinkPlatformProxy
         return $response;
     }
 
+    private function fetch(Request $request, string $target): Response
+    {
+        if ($qs = $request->getQueryString()) {
+            $target .= (str_contains($target, '?') ? '&' : '?').$qs;
+        }
+
+        $method = strtoupper($request->method());
+        $client = Http::withOptions(['allow_redirects' => false])
+            ->timeout(15)
+            ->withHeaders($this->forwardHeaders($request));
+
+        $pending = match ($method) {
+            'POST' => $client->asForm()->post($target, $request->post()),
+            'PATCH' => $client->patch($target, $request->all()),
+            'DELETE' => $client->delete($target),
+            default => $client->get($target),
+        };
+
+        $upstream = $pending->toPsrResponse();
+
+        return new Response(
+            (string) $upstream->getBody(),
+            $upstream->getStatusCode(),
+            $this->sanitizeHeaders($upstream->getHeaders()),
+        );
+    }
+
+    private function followLadillLinkRedirect(Request $request, string $slug, string $location): ?Response
+    {
+        $parsed = parse_url($location);
+        if (! is_array($parsed)) {
+            return null;
+        }
+
+        $host = strtolower((string) ($parsed['host'] ?? ''));
+        $linkHost = strtolower((string) parse_url(LadillLink::baseUrl(), PHP_URL_HOST));
+        if ($host !== $linkHost) {
+            return null;
+        }
+
+        $path = ltrim((string) ($parsed['path'] ?? ''), '/');
+        $slugPrefix = $slug.'/';
+        if (! str_starts_with($path, $slugPrefix)) {
+            return null;
+        }
+
+        return $this->forward($request, $slug, substr($path, strlen($slugPrefix)));
+    }
+
+    private function transferBaseUrl(): string
+    {
+        $domain = (string) config('app.transfer_domain', 'transfer.ladill.com');
+
+        return 'https://'.$domain;
+    }
+
     /** @return array<string, string> */
     private function forwardHeaders(Request $request): array
     {
@@ -62,7 +113,7 @@ class LinkPlatformProxy
             'Accept-Language' => $request->header('Accept-Language'),
             'User-Agent' => $request->header('User-Agent'),
             'Referer' => $request->header('Referer'),
-            'X-Ladill-Internal' => '1',
+            self::INTERNAL_HEADER => '1',
         ]);
     }
 
@@ -87,9 +138,15 @@ class LinkPlatformProxy
 
         if (str_starts_with($location, $prefix)) {
             $suffix = substr($location, strlen($prefix));
-            $rewritten = LadillLink::url($slug).$suffix;
 
-            return $rewritten;
+            return LadillLink::url($slug).$suffix;
+        }
+
+        $transfer = rtrim($this->transferBaseUrl(), '/').'/q/'.$slug;
+        if (str_starts_with($location, $transfer)) {
+            $suffix = substr($location, strlen($transfer));
+
+            return LadillLink::url($slug).$suffix;
         }
 
         return $location;

config/app.php

@@ -129,6 +129,7 @@ return [
     'auth_domain' => env('AUTH_DOMAIN', 'auth.'.(parse_url((string) env('PLATFORM_URL', 'https://ladill.com'), PHP_URL_HOST) ?: 'ladill.com')),
     'account_domain' => env('ACCOUNT_DOMAIN', 'account.'.(parse_url((string) env('PLATFORM_URL', 'https://ladill.com'), PHP_URL_HOST) ?: 'ladill.com')),
     'link_domain' => env('LINK_DOMAIN', parse_url((string) env('APP_URL', 'https://link.ladill.com'), PHP_URL_HOST) ?: 'link.ladill.com'),
+    'transfer_domain' => env('TRANSFER_DOMAIN', 'transfer.ladill.com'),
     'servers_domain' => env('SERVERS_DOMAIN', 'servers.'.(parse_url((string) env('PLATFORM_URL', 'https://ladill.com'), PHP_URL_HOST) ?: 'ladill.com')),
     'domains_domain' => env('DOMAINS_DOMAIN', 'domains.'.(parse_url((string) env('PLATFORM_URL', 'https://ladill.com'), PHP_URL_HOST) ?: 'ladill.com')),
 

tests/Feature/LinkRedirectTest.php

@@ -65,4 +65,34 @@ class LinkRedirectTest extends TestCase
                 && $request->hasHeader('X-Ladill-Internal', '1');
         });
     }
+
+    public function test_transfer_qr_proxies_to_transfer_app_without_redirect_loop(): void
+    {
+        $user = $this->user();
+        ShortLink::create([
+            'user_id' => $user->id,
+            'slug' => 'mo4o0v1t',
+            'source_app' => 'transfer',
+            'source_kind' => 'qr',
+            'is_managed_here' => false,
+            'destination_url' => 'https://ladl.link/mo4o0v1t',
+            'is_active' => true,
+        ]);
+
+        Http::fake([
+            'https://ladill.com/q/mo4o0v1t' => Http::response('', 302, [
+                'Location' => 'https://ladl.link/mo4o0v1t/transfer',
+            ]),
+            'https://transfer.ladill.com/q/mo4o0v1t/transfer' => Http::response('<html>Transfer files</html>', 200),
+        ]);
+
+        $this->get('https://ladl.link/mo4o0v1t')
+            ->assertOk()
+            ->assertSee('Transfer files');
+
+        Http::assertSent(function ($request) {
+            return $request->url() === 'https://transfer.ladill.com/q/mo4o0v1t/transfer'
+                && $request->hasHeader('X-Ladill-Internal', '1');
+        });
+    }
 }