ipaserver/dcerpc: Ensure LSA pipe has session key before using it

With Samba 4.2 there is a bug that prevents Samba to consider Kerberos
credentials used by IPA httpd process when talking to smbd. As result,
LSA RPC connection is seen as anonymous by Samba client code and we cannot
derive session key to use for encrypting trust secrets before transmitting
them.

Additionally, rewrite of the SMB protocol support in Samba caused previously
working logic of choosing DCE RPC binding string to fail. We need to try
a different set of priorities until they fail or succeed.

Requires Samba fixes from https://bugzilla.redhat.com/show_bug.cgi?id=1219832

Fixes https://bugzilla.redhat.com/show_bug.cgi?id=1219834

Reviewed-By: Tomas Babej <tbabej@redhat.com>

1 files changed, 14 insertions, 5 deletions

diff --git a/ipaserver/dcerpc.py b/ipaserver/dcerpc.py
index e342c4973..44689cc96 100644
--- a/ipaserver/dcerpc.py
+++ b/ipaserver/dcerpc.py
@@ -89,6 +89,10 @@ dcerpc_error_codes = {
     -1073741811: # NT_STATUS_INVALID_PARAMETER
         errors.RemoteRetrieveError(
             reason=_('AD domain controller complains about communication sequence. It may mean unsynchronized time on both sides, for example')),
+    -1073741776: # NT_STATUS_INVALID_PARAMETER_MIX, we simply will skip the binding
+        access_denied_error,
+    -1073741772: # NT_STATUS_OBJECT_NAME_NOT_FOUND
+        errors.RemoteRetrieveError(reason=_('CIFS server configuration does not allow access to \\\\pipe\\lsarpc')),
 }
 
 dcerpc_error_messages = {
@@ -728,16 +732,20 @@ class TrustDomainInstance(object):
             return
 
         attempts = 0
+        session_attempts = 0
         bindings = self.__gen_lsa_bindings(remote_host)
         for binding in bindings:
             try:
                 self._pipe = self.__gen_lsa_connection(binding)
-                if self._pipe:
+                if self._pipe and self._pipe.session_key:
                     break
             except errors.ACIError, e:
                 attempts = attempts + 1
+            except RuntimeError, e:
+                # When session key is not available, we just skip this binding
+                session_attempts = session_attempts + 1
 
-        if self._pipe is None and attempts == len(bindings):
+        if self._pipe is None and (attempts + session_attempts) == len(bindings):
             raise errors.ACIError(
                 info=_('CIFS server %(host)s denied your credentials') % dict(host=remote_host))
 
@@ -745,6 +753,7 @@ class TrustDomainInstance(object):
             raise errors.RemoteRetrieveError(
                 reason=_('Cannot establish LSA connection to %(host)s. Is CIFS server running?') % dict(host=remote_host))
         self.binding = binding
+        self.session_key = self._pipe.session_key
 
     def __gen_lsa_bindings(self, remote_host):
         """
@@ -753,11 +762,11 @@ class TrustDomainInstance(object):
         Generate all we can use. init_lsa_pipe() will try them one by one until
         there is one working.
 
-        We try NCACN_NP before NCACN_IP_TCP and signed sessions before unsigned.
+        We try NCACN_NP before NCACN_IP_TCP and use SMB2 before SMB1 or defaults.
         """
         transports = (u'ncacn_np', u'ncacn_ip_tcp')
-        options = ( u',', u'')
-        binding_template=lambda x,y,z: u'%s:%s[%s]' % (x, y, z)
+        options = ( u'smb2', u'smb1', u'')
+        binding_template=lambda x,y,z: u'%s:%s[%s,print]' % (x, y, z)
         return [binding_template(t, remote_host, o) for t in transports for o in options]
 
     def retrieve_anonymously(self, remote_host, discover_srv=False, search_pdc=False):