Hash usernames to prevent path traversal on save directories (#35)

* Hash usernames to prevent path traversal on save directories

* Make sure the ROM file exists before running the SSH server

---------

Co-authored-by: Jeff Quast <contact@jeffquast.com>

Author: vxgmichel

gambaterm/ssh.py

@@ -3,6 +3,7 @@
 import os
 import time
 import hmac
+import hashlib
 import asyncio
 import argparse
 import traceback
@@ -112,14 +113,16 @@ async def ssh_process_handler(process: SSHServerProcess[str]) -> int:
         console_cls.add_console_arguments(parser)
         namespace = parser.parse_args(command.split(), namespace)
 
-    # Manage save directory
+    # Manage save directory — hash username to prevent path traversal
     if "save_directory" in namespace.__dict__:
-        save_directory = (
-            None
-            if getattr(namespace, "input_file", False)
-            else Path("ssh_save") / username
-        )
-        setattr(namespace, "save_directory", save_directory)
+        if getattr(namespace, "input_file", False):
+            setattr(namespace, "save_directory", None)
+        else:
+            safe_name = hashlib.sha256(username.encode("utf-8")).hexdigest()[:16]
+            save_directory = Path("ssh_save") / safe_name
+            save_directory.mkdir(parents=True, exist_ok=True)
+            (save_directory / "username").write_text(username)
+            setattr(namespace, "save_directory", save_directory)
 
     # Pop console arguments and extract configuration
     console_callback = console_cls.pop_console_arguments(namespace)
@@ -457,6 +460,11 @@ def main(
             "Both `--password` and `--no-auth` cannot be provided at the same time"
         )
 
+    # Make sure that the ROM file exists before starting the server
+    rom_path: Path = namespace.romfile
+    if not rom_path.exists():
+        raise SystemExit(f"ROM file `{rom_path}` does not exist")
+
     # Run an executor with no limit on the number of threads
     try:
         with ThreadPoolExecutor(max_workers=32) as executor: