Modify principal selection for keytab authentication

Currently we construct the principal as host/fqdn@REALM. The problem
with this is that this principal doesn't have to be in the keytab. In
that case the provider fails to start. It is better to scan the keytab
and find the most suitable principal to use. Only in case no suitable
principal is found the backend should fail to start.

The second issue solved by this patch is that the realm we are
authenticating the machine to can be in general different from the realm
our users are part of (in case of cross Kerberos trust).

The patch adds new configuration option SDAP_SASL_REALM.

https://fedorahosted.org/sssd/ticket/781

1 files changed, 7 insertions, 2 deletions

diff --git a/src/providers/ldap/sdap_async_connection.c b/src/providers/ldap/sdap_async_connection.c
index b295c56e9..500e5f886 100644
--- a/src/providers/ldap/sdap_async_connection.c
+++ b/src/providers/ldap/sdap_async_connection.c
@@ -1318,6 +1318,12 @@ static void sdap_cli_kinit_step(struct tevent_req *req)
     struct sdap_cli_connect_state *state = tevent_req_data(req,
                                              struct sdap_cli_connect_state);
     struct tevent_req *subreq;
+    const char *realm;
+
+    realm = dp_opt_get_string(state->opts->basic, SDAP_SASL_REALM);
+    if (!realm) {
+        realm = dp_opt_get_string(state->opts->basic, SDAP_KRB5_REALM);
+    }
 
     subreq = sdap_kinit_send(state, state->ev,
                              state->be,
@@ -1329,8 +1335,7 @@ static void sdap_cli_kinit_step(struct tevent_req *req)
                                                    SDAP_KRB5_KEYTAB),
                         dp_opt_get_string(state->opts->basic,
                                                    SDAP_SASL_AUTHID),
-                        dp_opt_get_string(state->opts->basic,
-                                                   SDAP_KRB5_REALM),
+                        realm,
                         dp_opt_get_int(state->opts->basic,
                                                    SDAP_KRB5_TICKET_LIFETIME));
     if (!subreq) {