ipa-kdb: simplify trusted domain parent search

In terms of cross-forest trust parent domain is the root domain of
the forest because we only have trust established with the forest root.

In FreeIPA LDAP store all sub-domains stored in cn=<forest root>,
cn=ad,cn=trusts,... subtree. Thus, a first RDN after cn=ad is the
forest root domain. This allows us to simplify logic of finding
the parent domain.

For complex hierachical forests with more than two levels of
sub-domains, this will still be true because of the forest trust:
as forest trust is established to the forest root domain, any
communication to any sub-domain must traverse forest root domain's
domain controller.

Note that SSSD also generated incorrectly CA paths information
for forests with non-hierarchical tree-roots. In such cases
IPA KDC got confused and mistakenly assumed direct trust to the
non-hierarchical tree-root instead of going through the forest
root domain. See https://fedorahosted.org/sssd/ticket/3103 for
details.

Resolves: https://fedorahosted.org/freeipa/ticket/5738
Reviewed-By: Martin Babinsky <mbabinsk@redhat.com>

1 files changed, 14 insertions, 13 deletions

diff --git a/daemons/ipa-kdb/ipa_kdb_mspac.c b/daemons/ipa-kdb/ipa_kdb_mspac.c
index 65cc03565..cf1bd5b4e 100644
--- a/daemons/ipa-kdb/ipa_kdb_mspac.c
+++ b/daemons/ipa-kdb/ipa_kdb_mspac.c
@@ -2429,6 +2429,7 @@ krb5_error_code ipadb_mspac_get_trusted_domains(struct ipadb_context *ipactx)
     char *base = NULL;
     char *dnstr = NULL;
     char *dnl = NULL;
+    LDAPDN dn = NULL;
     char **sid_blacklist_incoming = NULL;
     char **sid_blacklist_outgoing = NULL;
     int ret, n, i;
@@ -2556,26 +2557,26 @@ krb5_error_code ipadb_mspac_get_trusted_domains(struct ipadb_context *ipactx)
             goto done;
         }
 
-        /* Note that after ldap_str2rdn() call dnl will point to end of one RDN
-         * which would be '\0' for trust root domain and ',' for subdomain */
         dnl--; dnl[0] = '\0';
-        ret = ldap_str2rdn(dnstr, &rdn, &dnl, LDAP_DN_FORMAT_LDAPV3);
+        /* Create a DN, which is now everything before the base,
+         * to get list of rdn values -- the last one would be a root domain.
+         * Since with cross-forest trust we have to route everything via root
+         * domain, that is enough for us to assign parentship. */
+        ret = ldap_str2dn(dnstr, &dn, LDAP_DN_FORMAT_LDAPV3);
         if (ret) {
             goto done;
         }
 
-        ldap_rdnfree(rdn);
-
-        if (dnl[0] != '\0') {
-            dnl++;
-            ret = ldap_str2rdn(dnl, &rdn, &dnl, LDAP_DN_FORMAT_LDAPV3);
-            if (ret) {
-                goto done;
-            }
-            t[n].parent_name = strndup(rdn[0]->la_value.bv_val, rdn[0]->la_value.bv_len);
-            ldap_rdnfree(rdn);
+        rdn = NULL;
+        for (i = 0; dn[i] != NULL; i++) {
+            rdn = dn[i];
         }
 
+        /* We should have a single AVA in the domain RDN */
+        t[n].parent_name = strndup(rdn[0]->la_value.bv_val, rdn[0]->la_value.bv_len);
+
+        ldap_dnfree(dn);
+
         free(dnstr);
         dnstr = NULL;
     }