removed validators library and improved url validation

cookbook/helper/HelperFunctions.py

@@ -1,4 +1,12 @@
+import socket
+from urllib.parse import urlparse
+
+from django.core.exceptions import ValidationError
+from django.core.validators import URLValidator
 from django.db.models import Func
+from ipaddress import ip_address
+
+from recipes import settings
 
 
 class Round(Func):
@@ -11,3 +19,30 @@ def str2bool(v):
         return v
     else:
         return v.lower() in ("yes", "true", "1")
+
+
+"""
+validates an url that is supposed to be imported
+checks that the protocol used is http(s) and that no local address is accessed
+@:param url to test
+@:return true if url is valid, false otherwise
+"""
+
+
+def validate_import_url(url):
+    try:
+        validator = URLValidator(schemes=['http', 'https'])
+        validator(url)
+    except ValidationError:
+        # if schema is not http or https, consider url invalid
+        return False
+
+    # resolve IP address of url
+    try:
+        url_ip_address = ip_address(str(socket.gethostbyname(urlparse(url).hostname)))
+    except (ValueError, AttributeError, TypeError, Exception) as e:
+        # if ip cannot be parsed, consider url invalid
+        return False
+
+    # validate that IP is neither private nor any other special address
+    return not any([url_ip_address.is_private, url_ip_address.is_reserved, url_ip_address.is_loopback,  url_ip_address.is_multicast, url_ip_address.is_link_local, ])