Insecure Permission Assignment for Garmin OAuth Token Store Summary "garminconnect" (≤ 0.3.4) wrote its OAuth token store to disk without restricting file-system permissions. Under the default Linux umask ("022") the token file "garmin_tokens.json" was created world-readable ("0o644"). The file contains the DI refresh token, so any other local user on a shared host could read it and obtain persistent, unauthorized access to the victim's Garmin Connect account. - Severity: High - Weakness: CWE-732 (Incorrect Permission Assignment for Critical Resource) - Affected versions: "<= 0.3.4" - Patched version: "0.3.5" Details "Client.dump()" created the token directory and file with no "mode" argument, leaving permissions entirely to the process umask: def dump(self, path: str) -> None: p = Path(path).expanduser() if p.is_dir() or not p.name.endswith(".json"): p = p / "garmin_tokens.json" p.parent.mkdir(parents=True, exist_ok=True) # no mode= p.write_text(self.dumps()) # no permission restriction The serialized payload includes "di_token", "di_refresh_token", and "di_client_id". The call is in the core library ("Garmin.login(tokenstore=...)" persists tokens this way), and all shipped usage examples default the token store to "~/.garminconnect". Under "umask 022" the resulting permissions were: - token directory → "0o755" - "garmin_tokens.json" → "0o644" (world-readable) A separate, unprivileged user on the same machine could read the file with a plain "open()" — no elevated privileges required — and extract the refresh token. Impact Local credential theft / privilege escalation on multi-user Linux or macOS hosts running under a permissive umask. The stolen refresh token can be exchanged for fresh access tokens via Garmin's OAuth endpoint, granting ongoing access to the victim's account (health/fitness data, activity history, device management) until the token is revoked. Patch Fixed in 0.3.5 (commit "77a3837"). "dump()" now creates the directory as "0o700" and writes the token file as "0o600" regardless of umask — using "os.open(..., O_CREAT|O_WRONLY|O_TRUNC, 0o600)" with "O_NOFOLLOW" where available, plus a defensive "chmod" that also tightens a pre-existing loose file: p.parent.mkdir(mode=0o700, parents=True, exist_ok=True) with contextlib.suppress(OSError): p.parent.chmod(0o700) flags = os.O_WRONLY | os.O_CREAT | os.O_TRUNC if hasattr(os, "O_NOFOLLOW"): flags |= os.O_NOFOLLOW fd = os.open(p, flags, 0o600) with os.fdopen(fd, "w", encoding="utf-8") as f: f.write(self.dumps()) with contextlib.suppress(OSError): p.chmod(0o600) Verified under "umask 022": directory "0o700", file "0o600", no group/other access. Workarounds If you cannot upgrade immediately, restrict the token store manually and keep it owner-only: chmod 700 ~/.garminconnect chmod 600 ~/.garminconnect/garmin_tokens.json Remediation 1. Upgrade to "garminconnect >= 0.3.5": pip install --upgrade garminconnect 2. Fix any token file already on disk — upgrading only tightens permissions on the next write, so an existing world-readable file stays exposed until then: chmod 600 ~/.garminconnect/garmin_tokens.json or remove it and log in again to mint a fresh token store 3. If the file was exposed on a shared host, treat the refresh token as compromised. Re-authenticate (delete the token store and log in again) so a new token is issued; consider the previously stored token potentially read by others until rotated. Credit Reported by EQSTLab via a private security advisory. garminconnect thanks them for the detailed, responsible disclosure.