heimdal:kdc: add support for HDB_ERR_WRONG_REALM

A backend can return this if asked with HDB_F_GET_CLIENT|HDB_F_FOR_AS_REQ
for a KRB5_NT_ENTERPRISE_PRINCIPAL record or for HDB_F_GET_SERVER | HDB_F_FOR_TGS_REQ.

entry_ex->entry.principal->realm needs to return the real realm of the principal
(or at least a the realm of the next cross-realm trust hop).

This is needed to route enterprise principals between AD domain trusts.

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>

4 files changed, 59 insertions, 1 deletions

diff --git a/source4/heimdal/kdc/kerberos5.c b/source4/heimdal/kdc/kerberos5.c
index cb97390d3e3..7e7aefd21e5 100644
--- a/source4/heimdal/kdc/kerberos5.c
+++ b/source4/heimdal/kdc/kerberos5.c
@@ -1060,6 +1060,30 @@ _kdc_as_rep(krb5_context context,
     if(ret == HDB_ERR_NOT_FOUND_HERE) {
 	kdc_log(context, config, 5, "client %s does not have secrets at this KDC, need to proxy", client_name);
 	goto out;
+    } else if (ret == HDB_ERR_WRONG_REALM) {
+	char *fixed_client_name = NULL;
+
+	ret = krb5_unparse_name(context, client->entry.principal,
+				&fixed_client_name);
+	if (ret) {
+	    goto out;
+	}
+
+	kdc_log(context, config, 0, "WRONG_REALM - %s -> %s",
+		client_name, fixed_client_name);
+	free(fixed_client_name);
+
+	ret = krb5_mk_error_ext(context,
+				KRB5_KDC_ERR_WRONG_REALM,
+				NULL, /* e_text */
+				NULL, /* e_data */
+				server_princ,
+				NULL, /* client_name */
+				&client->entry.principal->realm,
+				NULL, /* client_time */
+				NULL, /* client_usec */
+				reply);
+	goto out;
     } else if(ret){
 	const char *msg = krb5_get_error_message(context, ret);
 	kdc_log(context, config, 0, "UNKNOWN -- %s: %s", client_name, msg);
@@ -1779,7 +1803,7 @@ _kdc_as_rep(krb5_context context,
 
 out:
     free_AS_REP(&rep);
-    if(ret != 0 && ret != HDB_ERR_NOT_FOUND_HERE){
+    if(ret != 0 && ret != HDB_ERR_NOT_FOUND_HERE && reply->length == 0) {
 	krb5_mk_error(context,
 		      ret,
 		      e_text,
diff --git a/source4/heimdal/kdc/krb5tgs.c b/source4/heimdal/kdc/krb5tgs.c
index ca589e87fa0..1d0d1ddc3fa 100644
--- a/source4/heimdal/kdc/krb5tgs.c
+++ b/source4/heimdal/kdc/krb5tgs.c
@@ -1616,6 +1616,32 @@ server_lookup:
     if(ret == HDB_ERR_NOT_FOUND_HERE) {
 	kdc_log(context, config, 5, "target %s does not have secrets at this KDC, need to proxy", sp);
 	goto out;
+    } else if (ret == HDB_ERR_WRONG_REALM) {
+	if (ref_realm)
+	    free(ref_realm);
+	ref_realm = strdup(server->entry.principal->realm);
+	if (ref_realm == NULL) {
+	    ret = ENOMEM;
+	    goto out;
+	}
+
+	kdc_log(context, config, 5,
+		"Returning a referral to realm %s for "
+		"server %s.",
+		ref_realm, spn);
+	krb5_free_principal(context, sp);
+	sp = NULL;
+	free(spn);
+	spn = NULL;
+	ret = krb5_make_principal(context, &sp, r, KRB5_TGS_NAME,
+				  ref_realm, NULL);
+	if (ret)
+	    goto out;
+	ret = krb5_unparse_name(context, sp, &spn);
+	if (ret)
+	    goto out;
+
+	goto server_lookup;
     } else if(ret){
 	const char *new_rlm, *msg;
 	Realm req_rlm;
diff --git a/source4/heimdal/kdc/misc.c b/source4/heimdal/kdc/misc.c
index 4ef5439cf14..b0bc38a2b6f 100644
--- a/source4/heimdal/kdc/misc.c
+++ b/source4/heimdal/kdc/misc.c
@@ -99,6 +99,13 @@ _kdc_db_fetch(krb5_context context,
 	config->db[i]->hdb_close(context, config->db[i]);
 
 	switch (ret) {
+	case HDB_ERR_WRONG_REALM:
+	    /*
+	     * the ent->entry.principal just contains hints for the client
+	     * to retry. This is important for enterprise principal routing
+	     * between trusts.
+	     */
+	    /* fall through */
 	case 0:
 	    if (db)
 		*db = config->db[i];
diff --git a/source4/heimdal/lib/hdb/hdb_err.et b/source4/heimdal/lib/hdb/hdb_err.et
index 0bdcb385f6b..135747b0564 100644
--- a/source4/heimdal/lib/hdb/hdb_err.et
+++ b/source4/heimdal/lib/hdb/hdb_err.et
@@ -27,5 +27,6 @@ error_code MANDATORY_OPTION,	"Entry contains unknown mandatory extension"
 error_code NO_WRITE_SUPPORT,	"HDB backend doesn't contain write support"
 error_code NOT_FOUND_HERE,	"The secret for this entry is not replicated to this database"
 error_code MISUSE,		"Incorrect use of the API"
+error_code WRONG_REALM,		"The principal exists in another realm."
 
 end