From e37fdef709fffcfb7d7ec975466df294bfa68537 Mon Sep 17 00:00:00 2001
From: Clark Winkelmann <clark.winkelmann@gmail.com>
Date: Tue, 2 Mar 2021 15:57:06 +0100
Subject: [PATCH] Hide boot error (#2633)

Completely redact boot error unless debug mode or display_errors is enabled. Attempt to use Flarum log file when possible. Fixes #2290
---
 src/Http/Server.php | 62 +++++++++++++++++++++++++++++++++++++++------
 1 file changed, 54 insertions(+), 8 deletions(-)

diff --git a/src/Http/Server.php b/src/Http/Server.php
index 88697f01d..e7faf3b17 100644
--- a/src/Http/Server.php
+++ b/src/Http/Server.php
@@ -9,6 +9,7 @@
 
 namespace Flarum\Http;
 
+use Flarum\Foundation\ErrorHandling\LogReporter;
 use Flarum\Foundation\SiteInterface;
 use Laminas\Diactoros\Response;
 use Laminas\Diactoros\ServerRequest;
@@ -16,6 +17,7 @@ use Laminas\Diactoros\ServerRequestFactory;
 use Laminas\HttpHandlerRunner\Emitter\SapiEmitter;
 use Laminas\HttpHandlerRunner\RequestHandlerRunner;
 use Laminas\Stratigility\Middleware\ErrorResponseGenerator;
+use Psr\Log\LoggerInterface;
 use Throwable;
 
 class Server
@@ -55,26 +57,70 @@ class Server
         try {
             return $this->site->bootApp()->getRequestHandler();
         } catch (Throwable $e) {
-            exit($this->formatBootException($e));
+            // Apply response code first so whatever happens, it's set before anything is printed
+            http_response_code(500);
+
+            try {
+                $this->cleanBootExceptionLog($e);
+            } catch (Throwable $e) {
+                // Ignore errors in logger. The important goal is to log the original error
+            }
+
+            $this->fallbackBootExceptionLog($e);
         }
     }
 
     /**
-     * Display the most relevant information about an early exception.
+     * Attempt to log the boot exception in a clean way and stop the script execution.
+     * This means looking for debug mode and/or our normal error logger.
+     * There is always a risk for this to fail,
+     * for example if the container bindings aren't present
+     * or if there is a filesystem error.
+     * @param Throwable $error
      */
-    private function formatBootException(Throwable $error): string
+    private function cleanBootExceptionLog(Throwable $error)
     {
-        $message = $error->getMessage();
-        $file = $error->getFile();
-        $line = $error->getLine();
-        $type = get_class($error);
+        if (app()->has('flarum.config') && app('flarum.config')->inDebugMode()) {
+            // If the application booted far enough for the config to be available, we will check for debug mode
+            // Since the config is loaded very early, it is very likely to be available from the container
+            $message = $error->getMessage();
+            $file = $error->getFile();
+            $line = $error->getLine();
+            $type = get_class($error);
 
-        return <<<ERROR
+            echo <<<ERROR
             Flarum encountered a boot error ($type)<br />
             <b>$message</b><br />
             thrown in <b>$file</b> on line <b>$line</b>
 
 <pre>$error</pre>
 ERROR;
+            exit(1);
+        } elseif (app()->has(LoggerInterface::class)) {
+            // If the application booted far enough for the logger to be available, we will log the error there
+            // Considering most boot errors are related to database or extensions, the logger should already be loaded
+            // We check for LoggerInterface binding because it's a constructor dependency of LogReporter,
+            // then instantiate LogReporter through the container for automatic dependency injection
+            app(LogReporter::class)->report($error);
+
+            echo 'Flarum encountered a boot error. Details have been logged to the Flarum log file.';
+            exit(1);
+        }
+    }
+
+    /**
+     * If the clean logging doesn't work, then we have a last opportunity.
+     * Here we need to be extra careful not to include anything that might be sensitive on the page.
+     * @param Throwable $error
+     * @throws Throwable
+     */
+    private function fallbackBootExceptionLog(Throwable $error)
+    {
+        echo 'Flarum encountered a boot error. Details have been logged to the system PHP log file.<br />';
+
+        // Throwing the exception ensures it will be visible with PHP display_errors=On
+        // but invisible if that feature is turned off
+        // PHP will also automatically choose a valid place to log it based on the system settings
+        throw $error;
     }
 }