feat(http): implement URL normalization and validation for LibreTranslate service

meshchatx/src/backend/http_url_guard.py

@@ -4,7 +4,9 @@
 
 from __future__ import annotations
 
-from urllib.parse import urlparse, urlunparse
+import ipaddress
+import re
+from urllib.parse import unquote, urlparse, urlunparse
 
 
 class UnsafeOutboundUrlError(ValueError):
@@ -41,7 +43,69 @@ def normalize_loopback_http_service_base(url: str) -> str:
         msg = "URL host must be 127.0.0.1, localhost, or ::1"
         raise UnsafeOutboundUrlError(msg)
 
-    # Rebuild origin only (LibreTranslate mounts at /languages, /translate, etc.)
+    authority = netloc
+    origin = urlunparse((parsed.scheme, authority, "", "", "", ""))
+    return origin.rstrip("/")
+
+
+_WS_CTRL = re.compile(r"[\x00-\x20\x7f]")
+
+
+def normalize_libretranslate_http_service_base(url: str) -> str:
+    """Return scheme://host:port with no path, query, or fragment.
+
+    Accepts any HTTP(S) hostname or IP reachable from this process (remote LibreTranslate or
+    public API). Embedded credentials are rejected; non-http(s) schemes are rejected.
+
+    Literal IPv4 link-local targets (``169.254.0.0/16``) are rejected as a common SSRF/metadata
+    path. Other private or loopback addresses are allowed so local servers and overlays (e.g. VPN
+    mesh) continue to work.
+    """
+    if not url or not isinstance(url, str):
+        msg = "URL must be a non-empty string"
+        raise UnsafeOutboundUrlError(msg)
+
+    trimmed = url.strip()
+    if _WS_CTRL.search(trimmed):
+        msg = "URL must not contain whitespace or control characters"
+        raise UnsafeOutboundUrlError(msg)
+
+    parsed = urlparse(trimmed)
+    if parsed.scheme not in ("http", "https"):
+        msg = "URL must use http or https"
+        raise UnsafeOutboundUrlError(msg)
+
+    netloc = parsed.netloc or ""
+    if "@" in netloc:
+        msg = "URL must not contain credentials"
+        raise UnsafeOutboundUrlError(msg)
+
+    host = parsed.hostname
+    if host is None:
+        msg = "URL must include a hostname"
+        raise UnsafeOutboundUrlError(msg)
+
+    host_decoded = unquote(host, errors="strict")
+    if _WS_CTRL.search(host_decoded):
+        msg = "URL must not contain whitespace or control characters"
+        raise UnsafeOutboundUrlError(msg)
+
+    host_for_ip_check = host_decoded.lower().strip("[]")
+    try:
+        addr = ipaddress.ip_address(host_for_ip_check)
+    except ValueError:
+        pass
+    else:
+        if addr.version == 4 and addr.is_link_local:
+            msg = "URL must not target an IPv4 link-local address"
+            raise UnsafeOutboundUrlError(msg)
+        if addr.is_multicast or addr.is_unspecified:
+            msg = "URL must not target a multicast or unspecified address"
+            raise UnsafeOutboundUrlError(msg)
+        if addr.is_reserved:
+            msg = "URL must not target a reserved address"
+            raise UnsafeOutboundUrlError(msg)
+
     authority = netloc
     origin = urlunparse((parsed.scheme, authority, "", "", "", ""))
     return origin.rstrip("/")