fix(offline-sync): validate the screenshot archive before extracting it

.env.example

@@ -64,6 +64,13 @@ REVERB_APP_SECRET=secret
 ## Optional for every user, use optional
 SCREENSHOTS_STATE=any
 
+# Offline screenshot archives are processed within the upload request (Octane max_execution_time: 90 s) and
+# rejected before extraction above these limits: number of screenshots and total uncompressed size in bytes.
+# The default of 150 leaves about half of the time limit as headroom on S3 (up to ~310 ms per screenshot);
+# on the local disk (~75 ms) it can be raised.
+# OFFLINE_SCREENSHOTS_MAX_FILES=150
+# OFFLINE_SCREENSHOTS_MAX_SIZE_BYTES=1073741824
+
 # Octane (Swoole) worker counts; unset = Swoole default (one per host CPU)
 # OCTANE_WORKERS=
 # OCTANE_TASK_WORKERS=

app/Http/Controllers/Api/IntervalController.php

@@ -32,13 +32,16 @@
 use Illuminate\Http\Request;
 use Illuminate\Http\UploadedFile;
 use Illuminate\Support\Arr;
+use Illuminate\Support\Number;
+use Illuminate\Validation\ValidationException;
 use MessagePack\MessagePack;
 use phpseclib4\Crypt\RSA;
 use Settings;
 use Spatie\TemporaryDirectory\TemporaryDirectory;
 use Storage;
 use Str;
 use Symfony\Component\HttpFoundation\StreamedResponse;
+use RuntimeException;
 use Throwable;
 use Validator;
 use ZipArchive;
@@ -47,6 +50,8 @@
 {
     protected const MODEL = TimeInterval::class;
 
+    private const OFFLINE_SCREENSHOTS_EXTRACTION_CHUNK_SIZE = 64 * 1024;
+
     public function __construct(protected ScreenshotService $screenshotService)
     {
     }
@@ -807,14 +812,17 @@
             __('Cannot open file.' . is_int($zipOpenResult) ? " ZipArchive error code: $zipOpenResult" : ""),
         );
 
+        // Before the temporary directory is created: a rejected archive leaves nothing behind.
+        $this->validateOfflineScreenshotsArchive($zip);
+
         // The archive is extracted to the local disk of this web container and processed within the request,
         // so the queue worker does not need access to these files. The directory is removed when the request
         // ends, also on failure; leftovers of interrupted requests are removed by cattr:tmp:clean.
         $temporaryDirectory = (new TemporaryDirectory())
             ->location(Storage::disk('local')->path('tmp'))->force()->create();
 
         try {
-            $zip->extractTo($temporaryDirectory->path());
+            $this->extractOfflineScreenshotsArchive($zip, $temporaryDirectory->path());
             $zip->close();
 
             $creationResult = $this->attachOfflineScreenshots(
@@ -828,6 +836,117 @@
         return responder()->success($creationResult)->respond();
     }
 
+    /**
+     * Rejects the archive before anything is extracted or attached if it cannot be processed within the request
+     * (too many entries or too large when unpacked) or if an entry is not a plain file name.
+     *
+     * The desktop application exports a flat list of `<user_id>_<screenshot_id>` entries without directories.
+     *
+     * @throws ValidationException
+     */
+    private function validateOfflineScreenshotsArchive(ZipArchive $zip): void
+    {
+        $maxFiles = (int)config('app.offline_screenshots.max_files');
+        $maxSize = (int)config('app.offline_screenshots.max_size');
+
+        $fileCount = $zip->count();
+        if ($fileCount > $maxFiles) {
+            throw ValidationException::withMessages([
+                'file' => __('validation.offline-sync.too_many_files', ['count' => $fileCount, 'max' => $maxFiles]),
+            ]);
+        }
+
+        $totalSize = 0;
+        for ($index = 0; $index < $fileCount; $index++) {
+            $name = $zip->getNameIndex($index);
+            $stat = $zip->statIndex($index);
+
+            if (!is_string($name) || $stat === false || !self::isPlainArchiveEntryName($name)) {
+                throw ValidationException::withMessages([
+                    'file' => __('validation.offline-sync.wrong_file_name'),
+                ]);
+            }
+
+            $totalSize += $stat['size'];
+            if ($totalSize > $maxSize) {
+                throw self::offlineScreenshotsArchiveTooLarge($maxSize);
+            }
+        }
+    }
+
+    /**
+     * Extracts the validated archive into the directory, counting the bytes that are actually written.
+     *
+     * The sizes checked by validateOfflineScreenshotsArchive() come from the zip headers and can be forged, while
+     * ZipArchive::extractTo() writes whatever the entries decompress to. Here no more than the configured total
+     * size is ever written: each entry is copied in chunks of at most the remaining budget plus one byte, and the
+     * archive is rejected as soon as that extra byte is read.
+     *
+     * @throws ValidationException
+     */
+    private function extractOfflineScreenshotsArchive(ZipArchive $zip, string $directory): void
+    {
+        $maxSize = (int)config('app.offline_screenshots.max_size');
+        $remaining = $maxSize;
+
+        $fileCount = $zip->count();
+        for ($index = 0; $index < $fileCount; $index++) {
+            // The names were checked to be plain file names by validateOfflineScreenshotsArchive()
+            $name = $zip->getNameIndex($index);
+            $source = $name === false ? false : $zip->getStreamIndex($index);
+            abort_if($source === false, 400, __('Cannot open file.'));
+
+            try {
+                $target = fopen($directory . DIRECTORY_SEPARATOR . $name, 'wb');
+                if ($target === false) {
+                    throw new RuntimeException("Unable to create the extracted file for archive entry $index");
+                }
+                try {
+                    while (!feof($source)) {
+                        // Undecodable compressed data is reported as a warning and a failed read
+                        $chunk = @fread($source, min(self::OFFLINE_SCREENSHOTS_EXTRACTION_CHUNK_SIZE, $remaining + 1));
+                        abort_if($chunk === false, 400, __('Cannot open file.'));
+
+                        if (strlen($chunk) > $remaining) {
+                            throw self::offlineScreenshotsArchiveTooLarge($maxSize);
+                        }
+
+                        // A short write (e.g. a full disk) must not leave a truncated screenshot behind
+                        if (fwrite($target, $chunk) !== strlen($chunk)) {
+                            throw new RuntimeException("Unable to write the extracted file for archive entry $index");
+                        }
+                        $remaining -= strlen($chunk);
+                    }
+                } finally {
+                    fclose($target);
+                }
+            } finally {
+                fclose($source);
+            }
+        }
+    }
+
+    private static function offlineScreenshotsArchiveTooLarge(int $maxSize): ValidationException
+    {
+        return ValidationException::withMessages([
+            'file' => __('validation.offline-sync.too_large', [
+                'max' => Number::fileSize($maxSize, maxPrecision: 2),
+            ]),
+        ]);
+    }
+
+    /**
+     * A plain file name: not `.`, no directories, no parent references, no absolute or drive paths and no NUL bytes.
+     */
+    private static function isPlainArchiveEntryName(string $name): bool
+    {
+        return $name !== ''
+            && $name !== '.'
+            && strpbrk($name, "/\\\0") === false
+            && !str_contains($name, '..')
+            && preg_match('/^[A-Za-z]:/', $name) !== 1;
+    }
+
     /**
      * Saves the extracted offline screenshots synchronously, so that failures are reported in the result.
      *
@@ -963,7 +1082,7 @@
 
         CatEvent::dispatch(Filter::getAfterActionEventName(), [$timeIntervals, $filters]);
 
         $totalTime = $timeIntervals->sum(static fn($el) => (int) Carbon::parse($el->end_at)->diffInSeconds($el->start_at, true));
 
         return responder()->success([
             'time' => $totalTime,

config/app.php

@@ -38,6 +38,15 @@
     // Requests per minute and IP to the public signed screenshot routes (time-intervals/{id}/screenshot|thumb).
     // A timeline day of a user with 1-minute screenshots holds up to ~600 thumbnails (10 h of work).
     'screenshots_rate_limit' => (int) env('SCREENSHOTS_RATE_LIMIT', 600),
+    // Offline screenshots (offline-sync/upload-screenshots) are processed within the upload request, which must
+    // finish within Octane's max_execution_time (90 s). Larger archives are rejected before anything is extracted.
+    // 150 entries ≈ 1.5 working days of 96 screenshots: ~11 s at ~75 ms per 1920×1080 screenshot on the local disk,
+    // ~47 s at ~310 ms on S3, leaving headroom for extraction, queries and the response.
+    'offline_screenshots' => [
+        'max_files' => (int) env('OFFLINE_SCREENSHOTS_MAX_FILES', 150),
+        // Total uncompressed size of all archive entries
+        'max_size' => (int) env('OFFLINE_SCREENSHOTS_MAX_SIZE_BYTES', 1024 * 1024 * 1024),
+    ],
     'user_activity' => [
         'online_status_time' => 60,
         'heartbeat_period' => 30,

resources/lang/en/validation.php

@@ -114,7 +114,10 @@
         'screenshot_not_attached' => 'Screenshot not attached (see logs)',
         'time_interval_already_exist' => 'The time for this interval already exists.',
         'time_interval_added' => 'Added',
-        'wrong_extension' => 'File extension should be .cattr'
+        'wrong_extension' => 'File extension should be .cattr',
+        'too_many_files' => 'The archive contains too many screenshots (:count), the maximum is :max',
+        'too_large' => 'The unpacked screenshots are too large, the maximum is :max',
+        'wrong_file_name' => 'The archive must contain only screenshot files without folders'
     ],
 
     'tasks-relations' => [

resources/lang/ru/validation.php

@@ -149,7 +149,10 @@
         'screenshot_not_attached' => 'Скриншот не прикреплён (см. логи)',
         'time_interval_already_exist' => 'Время для этого интервала уже существует.',
         'time_interval_added' => 'Добавлен',
-        'wrong_extension' => 'Расширение файла должно быть .cattr'
+        'wrong_extension' => 'Расширение файла должно быть .cattr',
+        'too_many_files' => 'Архив содержит слишком много скриншотов (:count), максимум — :max',
+        'too_large' => 'Распакованные скриншоты слишком большие, максимум — :max',
+        'wrong_file_name' => 'Архив должен содержать только файлы скриншотов без папок'
     ],
 
     'tasks-relations' => [