error handling for async scanning

secheaders/secheaders.py

@@ -30,17 +30,7 @@ def main():
         parser.print_usage(sys.stderr)
         sys.exit(1)
 
-    target_list = []
-    if args.target_list:
-        with open(args.target_list, encoding='utf-8') as file:
-            target_list = [line.rstrip() for line in file]
     if args.url:
-        target_list.append(args.url)
-
-    target_list = list(set(target_list))  # Remove possible duplicates
-
-    if args.url:
-
         try:
             res = scan_target(args.url, args)
         except SecurityHeadersException as e:
@@ -55,20 +45,18 @@ def main():
 
 
 def async_scan_done(scan):
-    try:
-        res, args = scan.result()
+    res, args = scan.result()
+    if 'error' in res:
+        print(f"Scanning target {res['target']}...")
+        print(f"Error: {res['error']}\n")
+    else:
         print(cmd_utils.output_text(res['target'], res['headers'], res['https'], args.no_color, args.verbose))
-    except SecurityHeadersException as e:
-        print(e, file=sys.stderr)
 
 
 def scan_target(url, args):
-    try:
-        header_check = SecurityHeaders(url, args.max_redirects, args.insecure)
-        header_check.fetch_headers()
-        headers = header_check.check_headers()
-    except SecurityHeadersException as e:
-        raise e
+    header_check = SecurityHeaders(url, args.max_redirects, args.insecure)
+    header_check.fetch_headers()
+    headers = header_check.check_headers()
 
     if not headers:
         raise FailedToFetchHeaders("Failed to fetch headers")
@@ -78,33 +66,38 @@ def scan_target(url, args):
 
 
 def scan_target_wrapper(url, args):
-    # A bit of a dirty hack to pass args to the done callback
-    return scan_target(url, args), args
+    try:
+        # Return the args also for the callback function
+        return scan_target(url, args), args
+    except SecurityHeadersException as e:
+        return {'target': url, 'error': str(e)}, args
 
 
 async def scan_multiple_targets(args):
     with open(args.target_list, encoding='utf-8') as file:
         targets = [line.rstrip() for line in file]
 
+    targets = list(set(targets))  # Remove possible duplicates
     loop = asyncio.get_event_loop()
     tasks = []
     for target in targets:
-        if args.json:
-            task = loop.run_in_executor(None, scan_target, target, args)
-        else:
-            task = loop.run_in_executor(None, scan_target_wrapper, target, args)
+        task = loop.run_in_executor(None, scan_target_wrapper, target, args)
+        if not args.json:
+            # Output result of each scan immediately
             task.add_done_callback(async_scan_done)
         tasks.append(task)
 
     res = []
     for task in tasks:
         await task
 
+    # When json output, aggregate the results and output the json dump at the end
     if args.json:
         for t in tasks:
-            res.append(t.result())
+            result, _args = t.result()
+            res.append(result)
 
-        print(str(res))
+        print(json.dumps(res, indent=2))
 
 if __name__ == "__main__":
     main()