add dns-based ldap domain controller lookup

   and rotate through the returned list of servers, per request!

1 files changed, 20 insertions, 0 deletions

diff --git a/session_ldap.py b/session_ldap.py
index b478ef5..d12f008 100644
--- a/session_ldap.py
+++ b/session_ldap.py
@@ -28,3 +28,23 @@ def authenticated_user(server_uri, user_format, username, password):
    #   print("Either an ldap password is required, or we had another bind error.")
    #   return False
    return False
+
+def list_ldap_servers_for_domain(domain):
+   # return list of hostnames from the _ldap._tcp.{domain} SRV lookup
+   try:
+      import dns
+      import dns.resolver
+   except:
+      print("Need python3-dns installed for dns lookups.")
+      return [domain]
+   namelist = []
+   try:
+      query = dns.resolver.query(f"_ldap._tcp.{domain}","SRV")
+   except dns.resolver.NXDOMAIN:
+      # no records exist that match the request, so we were probably given a specific hostname, and an empty query will trigger the logic below that will add the original domain to the list.
+      query = []
+   for i in query:
+      namelist.append(i.target.to_text().rstrip("."))
+   if not len(namelist):
+      namelist.append(domain)
+   return namelist