Better ipv6 support when checking network bans

- Rely on using `in` between IP addresses and IP Networks
  (https://docs.python.org/3/library/ipaddress.html#networks-as-containers-of-addresses)
  rather than re-implement that ip address / network matching with
  CIDRs ourselves.
- Brings in *much* better ipv6 support
- Adds a few test cases for ipv6 support as well

Discovered while investigating the test failures in
#1856

binderhub/base.py

@@ -38,12 +38,12 @@ def check_request_ip(self):
         match = ip_in_networks(
             request_ip,
             ban_networks,
-            min_prefix_len=self.settings["ban_networks_min_prefix_len"],
         )
         if match:
-            network, message = match
+            network_spec = match
+            message = ban_networks[network_spec]
             app_log.warning(
-                f"Blocking request from {request_ip} matching banned network {network}: {message}"
+                f"Blocking request from {request_ip} matching banned network {network_spec}: {message}"
             )
             raise web.HTTPError(403, f"Requests from {message} are not allowed")
 

binderhub/tests/test_utils.py

@@ -1,4 +1,3 @@
-import ipaddress
 from unittest import mock
 
 import pytest
@@ -116,24 +115,14 @@ def later():
         ("192.168.1.2", ["192.168.1.0/24", "255.255.0.0/16"], True),
         ("192.168.1.2", ["255.255.0.0/16", "192.168.1.0/24"], True),
         ("192.168.1.2", [], False),
+        ("2001:db8:0:0:0:0:0:1", ["2001:db8::/32", "192.168.1.1/32"], True),
+        ("3001:db8:0:0:0:0:0:1", ["2001:db8::/32", "192.168.1.1/32"], False),
     ],
 )
 def test_ip_in_networks(ip, cidrs, found):
-    networks = {ipaddress.ip_network(cidr): f"message {cidr}" for cidr in cidrs}
-    if networks:
-        min_prefix = min(net.prefixlen for net in networks)
-    else:
-        min_prefix = 1
-    match = utils.ip_in_networks(ip, networks, min_prefix)
+    match = utils.ip_in_networks(ip, cidrs)
     if found:
         assert match
-        net, message = match
-        assert message == f"message {net}"
-        assert ipaddress.ip_address(ip) in net
+        assert match in cidrs
     else:
         assert match is False
-
-
-def test_ip_in_networks_invalid():
-    with pytest.raises(ValueError):
-        utils.ip_in_networks("1.2.3.4", {}, 0)

binderhub/utils.py

@@ -4,6 +4,7 @@
 import time
 from collections import OrderedDict
 from hashlib import blake2b
+from typing import Iterable
 from unittest.mock import Mock
 
 from kubernetes.client import api_client
@@ -167,32 +168,20 @@ def url_path_join(*pieces):
     return result
 
 
-def ip_in_networks(ip, networks, min_prefix_len=1):
-    """Return whether `ip` is in the dict of networks
-
-    This is O(1) regardless of the size of networks
-
-    Implementation based on netaddr.IPSet.__contains__
-
-    Repeatedly checks if ip/32; ip/31; ip/30; etc. is in networks
-    for all netmasks that match the given ip,
-    for a max of 32 dict key lookups for ipv4.
+def ip_in_networks(ip_addr: str, networks: Iterable[str]):
+    """
+    Checks if `ip_addr` is contained within any of the networks in `networks`
 
-    If all netmasks have a prefix length of e.g. 24 or greater,
-    min_prefix_len prevents checking wider network masks that can't possibly match.
+    If ip_addr is in any of the provided networks, return the first network that matches.
+    If not, return False
 
-    Returns `(netmask, networks[netmask])` for matching netmask
-    in networks, if found; False, otherwise.
+    Both ipv6 and ipv4 are supported
     """
-    if min_prefix_len < 1:
-        raise ValueError(f"min_prefix_len must be >= 1, got {min_prefix_len}")
-    if not networks:
-        return False
-    check_net = ipaddress.ip_network(ip)
-    while check_net.prefixlen >= min_prefix_len:
-        if check_net in networks:
-            return check_net, networks[check_net]
-        check_net = check_net.supernet(1)
+    ip = ipaddress.ip_address(ip_addr)
+    for network_spec in networks:
+        network = ipaddress.ip_network(network_spec)
+        if ip in network:
+            return network_spec
     return False