sdap: improve filtering of multiple results in GC lookups

The Global Catalog of AD contains some information about all users and
groups in an AD forest. Users from different domain in the forest can
have the same name. The most obvious example is the Administrator user
which is present in all domains. Although SSSD uses a domain specific
search base for looking up users in the GC the search might still return
multiple results if there is a user with the same name in one of the
child (or grand-child ...) domains because of the hierarchic nature of
the LDAP tree. Limiting the search depth would not help because users
can be created in deeply nested OUs.

Currently SSSD expects in this case that the user object is store in
CN=Users or below. This works for all default users like Administrator
but in general users can be created anywhere in the directory tree. If a
user is created outside of CN=Users and there is a user with the same
name in a child domain the initgroups command to look up the
group-memberships of the user fails because it is not clear which of the
two results should be used (initgroups for the child domain user works
fine).

This patch adds an additional scheme to select the right result based on
the domain component attribute name 'dc'. This attribute indicates an
additional component in the domain name and hence a child domain. So as
long as the result contains a dc component following out search base it
cannot be the object we are looking for. This scheme includes the old
CN=Users based one but since it is more expensive I kept the old scheme
which so far worked all the time and only use the new one if the old one
fails.

Resolves https://fedorahosted.org/sssd/ticket/2961

Reviewed-by: Jakub Hrozek <jhrozek@redhat.com>

1 files changed, 6 insertions, 0 deletions

diff --git a/src/db/sysdb.h b/src/db/sysdb.h
index bb8ca08b1..4b2feffd0 100644
--- a/src/db/sysdb.h
+++ b/src/db/sysdb.h
@@ -1228,4 +1228,10 @@ errno_t sysdb_handle_original_uuid(const char *orig_name,
                                    const char *src_name,
                                    struct sysdb_attrs *dest_attrs,
                                    const char *dest_name);
+
+errno_t sysdb_try_to_find_expected_dn(struct sss_domain_info *dom,
+                                      const char *domain_component_name,
+                                      struct sysdb_attrs **usr_attrs,
+                                      size_t count,
+                                      struct sysdb_attrs **exp_usr);
 #endif /* __SYS_DB_H__ */