Prepare KarlDNS production deployment

karldns/security.py

@@ -0,0 +1,181 @@
+from __future__ import annotations
+
+import base64
+import hashlib
+import hmac
+import secrets
+import time
+from datetime import UTC, datetime
+from ipaddress import ip_address, ip_network
+
+from fastapi import HTTPException, Request
+
+from .settings import DdnsSettings
+
+DASHBOARD_UNLOCK_COOKIE = "ddns_dashboard_unlock"
+DASHBOARD_UNLOCK_DEFAULT_SECONDS = 24 * 60 * 60
+DASHBOARD_UNLOCK_STAY_SIGNED_IN_SECONDS = 30 * 24 * 60 * 60
+
+
+def credentials_from_basic_auth(header: str) -> tuple[str | None, str | None]:
+    try:
+        raw = base64.b64decode(header.split(" ", 1)[1]).decode("utf-8")
+    except Exception:
+        return None, None
+    if ":" not in raw:
+        return None, None
+    username, password = raw.split(":", 1)
+    return username, password
+
+
+def hash_secret(token: str) -> str:
+    salt = secrets.token_hex(16)
+    digest = hashlib.pbkdf2_hmac("sha256", token.encode("utf-8"), salt.encode("ascii"), 200_000)
+    return f"pbkdf2_sha256${salt}${digest.hex()}"
+
+
+def verify_secret(token: str, stored: str) -> bool:
+    try:
+        algorithm, salt, expected = stored.split("$", 2)
+    except ValueError:
+        return False
+    if algorithm != "pbkdf2_sha256":
+        return False
+    digest = hashlib.pbkdf2_hmac("sha256", token.encode("utf-8"), salt.encode("ascii"), 200_000)
+    return hmac.compare_digest(digest.hex(), expected)
+
+
+def hash_lookup_token(token: str) -> str:
+    return hashlib.sha256(token.encode("utf-8")).hexdigest()
+
+
+def sign_dashboard_unlock_cookie(
+    hostname: str,
+    management_slug: str,
+    password_hash: str,
+    signing_secret: str,
+    max_age_seconds: int,
+    now: int | None = None,
+) -> str:
+    timestamp = int(time.time() if now is None else now)
+    bounded_max_age = _bounded_dashboard_unlock_seconds(max_age_seconds)
+    signature = _dashboard_unlock_signature(
+        hostname,
+        management_slug,
+        password_hash,
+        signing_secret,
+        timestamp,
+        bounded_max_age,
+    )
+    return f"v3:{timestamp}:{bounded_max_age}:{signature}"
+
+
+def verify_dashboard_unlock_cookie(
+    hostname: str,
+    management_slug: str,
+    password_hash: str | None,
+    signing_secret: str,
+    cookie_value: str | None,
+) -> bool:
+    if not password_hash or not signing_secret or not cookie_value:
+        return False
+    try:
+        version, raw_timestamp, raw_max_age, supplied = cookie_value.split(":", 3)
+        timestamp = int(raw_timestamp)
+        max_age_seconds = _bounded_dashboard_unlock_seconds(int(raw_max_age))
+    except ValueError:
+        return False
+    if version != "v3":
+        return False
+    now = int(time.time())
+    if timestamp > now + 60 or now - timestamp > max_age_seconds:
+        return False
+    expected = _dashboard_unlock_signature(
+        hostname,
+        management_slug,
+        password_hash,
+        signing_secret,
+        timestamp,
+        max_age_seconds,
+    )
+    return hmac.compare_digest(supplied, expected)
+
+
+def _dashboard_unlock_signature(
+    hostname: str,
+    management_slug: str,
+    password_hash: str,
+    signing_secret: str,
+    timestamp: int,
+    max_age_seconds: int,
+) -> str:
+    payload = f"{hostname}\0{management_slug}\0{password_hash}\0{timestamp}\0{max_age_seconds}".encode()
+    return hmac.new(signing_secret.encode(), payload, hashlib.sha256).hexdigest()
+
+
+def dashboard_cookie_signing_secret(settings: DdnsSettings) -> str:
+    return settings.dashboard_cookie_secret or settings.admin_password
+
+
+def dashboard_csrf_token(management_slug: str, account: dict[str, str | int | None]) -> str:
+    hostname = str(account["hostname"])
+    password_hash = str(account.get("dashboard_password_hash") or "")
+    day = datetime.now(UTC).strftime("%Y-%m-%d")
+    key = f"{management_slug}\0{password_hash}".encode()
+    return hmac.new(key, f"dashboard:{hostname}:{day}".encode(), hashlib.sha256).hexdigest()
+
+
+def require_dashboard_csrf(management_slug: str, account: dict[str, str | int | None], supplied: str) -> None:
+    if not supplied or not hmac.compare_digest(supplied, dashboard_csrf_token(management_slug, account)):
+        raise HTTPException(status_code=403, detail="invalid csrf token")
+
+
+def _bounded_dashboard_unlock_seconds(max_age_seconds: int) -> int:
+    return max(60, min(max_age_seconds, DASHBOARD_UNLOCK_STAY_SIGNED_IN_SECONDS))
+
+
+def admin_csrf_token(settings: DdnsSettings) -> str:
+    day = datetime.now(UTC).strftime("%Y-%m-%d")
+    return hmac.new(settings.admin_password.encode("utf-8"), f"admin:{day}".encode(), hashlib.sha256).hexdigest()
+
+
+def require_admin_csrf(settings: DdnsSettings, supplied: str) -> None:
+    if not supplied or not hmac.compare_digest(supplied, admin_csrf_token(settings)):
+        raise HTTPException(status_code=403, detail="invalid csrf token")
+
+
+def client_ip(request: Request, settings: DdnsSettings | None = None) -> str:
+    peer = request.client.host if request.client else "unknown"
+    forwarded = request.headers.get("x-forwarded-for", "")
+    if forwarded and settings and _trusted_proxy(peer, settings.trusted_proxy_ips):
+        return forwarded.split(",", 1)[0].strip()
+    return peer
+
+
+def is_rate_limited_path(path: str) -> bool:
+    return path == "/" or path.startswith(("/m/", "/api/v1/hostnames", "/api/v1/router/"))
+
+
+def rate_limit_bucket(path: str) -> str:
+    for prefix in ("/m/", "/api/v1/hostnames", "/api/v1/router/"):
+        if path.startswith(prefix):
+            return prefix.rstrip("/")
+    return path
+
+
+def _trusted_proxy(peer: str, trusted: set[str]) -> bool:
+    if not trusted:
+        return False
+    try:
+        peer_ip = ip_address(peer)
+    except ValueError:
+        return False
+    for candidate in trusted:
+        try:
+            if "/" in candidate and peer_ip in ip_network(candidate, strict=False):
+                return True
+            if "/" not in candidate and peer_ip == ip_address(candidate):
+                return True
+        except ValueError:
+            continue
+    return False