Add obfuscation for stored creds.

app/model_downloader/auth/token_store.py

@@ -1,19 +1,38 @@
-"""On-disk OAuth token persistence — one ``0600`` JSON file per provider.
+"""On-disk OAuth token persistence — one machine-bound blob per provider.
 
 Tokens live under ``folder_paths.get_system_user_directory("download_auth")``,
-never in the SQLite DB. The file is written with ``0600`` so only the owner can
-read the refresh/access token at rest.
+never in the SQLite DB. Each provider file is written ``0600`` and holds an
+opaque blob, not readable JSON: the token JSON is XORed with an HMAC-SHA256
+keystream whose key is derived from stable machine/install attributes plus a
+per-install random salt.
+
+This is obfuscation, not confidentiality. It stops a token from being read by a
+human browsing files, grepped out of a backup, or lifted from a folder copied to
+another machine (the blob won't decrypt off its origin machine). It does not
+protect against code running inside this process (custom nodes) or an attacker
+who reads this source and recomputes the key.
 """
 
 from __future__ import annotations
 
+import base64
+import getpass
+import hashlib
+import hmac
 import json
 import os
+import platform
+import secrets
 import time
 from dataclasses import asdict, dataclass
 
 import folder_paths
 
+_SALT_FILE = ".salt"
+_SALT_LEN = 32
+_NONCE_LEN = 16
+_PBKDF2_ITERS = 200_000
+
 
 @dataclass
 class Token:
@@ -37,17 +56,103 @@ def _auth_dir() -> str:
 
 
 def _token_path(provider: str) -> str:
-    return os.path.join(_auth_dir(), f"{provider}.json")
+    return os.path.join(_auth_dir(), f"{provider}.bin")
+
+
+def _machine_id() -> bytes:
+    """A stable per-machine identifier, best-effort across platforms."""
+    for path in ("/etc/machine-id", "/var/lib/dbus/machine-id"):
+        try:
+            with open(path, "rb") as f:
+                return f.read().strip()
+        except OSError:
+            pass
+    if os.name == "nt":
+        import winreg
+
+        try:
+            key = winreg.OpenKey(
+                winreg.HKEY_LOCAL_MACHINE, r"SOFTWARE\Microsoft\Cryptography"
+            )
+            try:
+                guid, _ = winreg.QueryValueEx(key, "MachineGuid")
+                return str(guid).encode("utf-8")
+            finally:
+                winreg.CloseKey(key)
+        except OSError:
+            pass
+    return platform.node().encode("utf-8")
+
+
+def _machine_material(auth_dir: str) -> bytes:
+    try:
+        user = getpass.getuser()
+    except Exception:
+        user = ""
+    parts = (_machine_id(), platform.node().encode("utf-8"), user.encode("utf-8"), auth_dir.encode("utf-8"))
+    return b"\x00".join(parts)
+
+
+def _load_or_create_salt(auth_dir: str) -> bytes | None:
+    path = os.path.join(auth_dir, _SALT_FILE)
+    try:
+        with open(path, "rb") as f:
+            salt = f.read()
+        if len(salt) == _SALT_LEN:
+            return salt
+    except FileNotFoundError:
+        pass
+    except OSError:
+        return None
+    salt = secrets.token_bytes(_SALT_LEN)
+    fd = os.open(path, os.O_WRONLY | os.O_CREAT | os.O_TRUNC, 0o600)
+    with os.fdopen(fd, "wb") as f:
+        f.write(salt)
+    os.chmod(path, 0o600)
+    return salt
+
+
+def _derive_key(salt: bytes, auth_dir: str) -> bytes:
+    return hashlib.pbkdf2_hmac(
+        "sha256", _machine_material(auth_dir), salt, _PBKDF2_ITERS, dklen=32
+    )
+
+
+def _keystream(key: bytes, nonce: bytes, n: int) -> bytes:
+    out = bytearray()
+    counter = 0
+    while len(out) < n:
+        out.extend(hmac.new(key, nonce + counter.to_bytes(8, "big"), hashlib.sha256).digest())
+        counter += 1
+    return bytes(out[:n])
+
+
+def _xor(data: bytes, stream: bytes) -> bytes:
+    return bytes(a ^ b for a, b in zip(data, stream))
 
 
 def load(provider: str) -> Token | None:
+    auth_dir = _auth_dir()
     try:
-        with open(_token_path(provider), "r", encoding="utf-8") as f:
-            data = json.load(f)
+        with open(_token_path(provider), "rb") as f:
+            blob = base64.b64decode(f.read())
     except FileNotFoundError:
         return None
     except (ValueError, OSError):
         return None
+    salt = _load_or_create_salt(auth_dir)
+    if salt is None or len(blob) <= _NONCE_LEN:
+        return None
+    nonce, ciphertext = blob[:_NONCE_LEN], blob[_NONCE_LEN:]
+    key = _derive_key(salt, auth_dir)
+    plaintext = _xor(ciphertext, _keystream(key, nonce, len(ciphertext)))
+    # A wrong machine / corrupt file decrypts to garbage; treat as logged out.
+    try:
+        data = json.loads(plaintext)
+    except ValueError:
+        return None
+    if not isinstance(data, dict) or "access_token" not in data:
+        return None
     return Token(
         access_token=data.get("access_token", ""),
         refresh_token=data.get("refresh_token"),
@@ -58,10 +163,19 @@ def load(provider: str) -> Token | None:
 
 
 def save(provider: str, token: Token) -> None:
+    auth_dir = _auth_dir()
+    salt = _load_or_create_salt(auth_dir)
+    if salt is None:
+        return
+    key = _derive_key(salt, auth_dir)
+    nonce = secrets.token_bytes(_NONCE_LEN)
+    plaintext = json.dumps(asdict(token)).encode("utf-8")
+    ciphertext = _xor(plaintext, _keystream(key, nonce, len(plaintext)))
+    blob = base64.b64encode(nonce + ciphertext)
     path = _token_path(provider)
     fd = os.open(path, os.O_WRONLY | os.O_CREAT | os.O_TRUNC, 0o600)
-    with os.fdopen(fd, "w", encoding="utf-8") as f:
-        json.dump(asdict(token), f)
+    with os.fdopen(fd, "wb") as f:
+        f.write(blob)
     os.chmod(path, 0o600)