s4-dns: added a dns update task

This task watches for changes in the list of DCs, and creates a bind9
formatted file that grants update permission to all DCs, plus to the
administration, and machines update for their own names.

Pair-Programmed-With: Andrew Bartlett <abartlet@samba.org>

2 files changed, 235 insertions, 0 deletions

diff --git a/source4/dsdb/config.mk b/source4/dsdb/config.mk
index 5ea31c3e2c..b038b5e062 100644
--- a/source4/dsdb/config.mk
+++ b/source4/dsdb/config.mk
@@ -90,3 +90,16 @@ KCC_SRV_OBJ_FILES = $(addprefix $(dsdbsrcdir)/kcc/, \
 
 $(eval $(call proto_header_template,$(dsdbsrcdir)/kcc/kcc_service_proto.h,$(KCC_SRV_OBJ_FILES:.o=.c)))
 
+#######################
+# Start SUBSYSTEM DNS_UPDATE_SRV
+[MODULE::DNS_UPDATE_SRV]
+INIT_FUNCTION = server_service_dnsupdate_init
+SUBSYSTEM = service
+PRIVATE_DEPENDENCIES = \
+		SAMDB \
+		process_model
+# End SUBSYSTEM DNS_UPDATE_SRV
+#######################
+
+DNS_UPDATE_SRV_OBJ_FILES = $(addprefix $(dsdbsrcdir)/dns/, \
+		dns_update.o)
diff --git a/source4/dsdb/dns/dns_update.c b/source4/dsdb/dns/dns_update.c
new file mode 100644
index 0000000000..90ada8810e
--- /dev/null
+++ b/source4/dsdb/dns/dns_update.c
@@ -0,0 +1,222 @@
+/*
+   Unix SMB/CIFS mplementation.
+
+   DNS udpate service
+
+   Copyright (C) Andrew Tridgell 2009
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+*/
+
+/*
+  this module auto-creates the named.conf.update file, which tells
+  bind9 what KRB5 principals it should accept for updates to our zone
+ */
+
+#include "includes.h"
+#include "dsdb/samdb/samdb.h"
+#include "auth/auth.h"
+#include "smbd/service.h"
+#include "lib/events/events.h"
+#include "lib/messaging/irpc.h"
+#include "lib/ldb/include/ldb_errors.h"
+#include "param/param.h"
+#include "system/filesys.h"
+#include "lib/tevent/tevent.h"
+
+struct dnsupdate_service {
+	struct task_server *task;
+	struct auth_session_info *system_session_info;
+	struct ldb_context *samdb;
+
+	struct {
+		uint32_t interval;
+		struct tevent_timer *te;
+	} periodic;
+};
+
+/*
+  called every dnsupdate:interval seconds
+ */
+static void dnsupdate_rebuild(struct dnsupdate_service *service)
+{
+	int ret;
+	struct ldb_result *res;
+	const char *tmp_path, *path;
+	int fd, i;
+	const char *attrs[] = { "sAMAccountName", NULL };
+	const char *realm = lp_realm(service->task->lp_ctx);
+	TALLOC_CTX *tmp_ctx = talloc_new(service);
+	const char *rndc_cmd;
+
+	ret = ldb_search(service->samdb, tmp_ctx, &res, NULL, LDB_SCOPE_SUBTREE,
+			 attrs, "(&(primaryGroupID=%u)(objectClass=computer))",
+			 DOMAIN_RID_DCS);
+	if (ret != LDB_SUCCESS) {
+		DEBUG(0,(__location__ ": Unable to find DCs list - %s", ldb_errstring(service->samdb)));
+		talloc_free(tmp_ctx);
+		return;
+	}
+
+	path = lp_parm_string(service->task->lp_ctx, NULL, "dnsupdate", "path");
+	if (path == NULL) {
+		path = private_path(tmp_ctx, service->task->lp_ctx, "named.conf.update");
+	}
+
+	tmp_path = talloc_asprintf(tmp_ctx, "%s.tmp", path);
+	if (path == NULL || tmp_path == NULL) {
+		DEBUG(0,(__location__ ": Unable to get paths"));
+		talloc_free(tmp_ctx);
+		return;
+	}
+
+	fd = open(tmp_path, O_CREAT|O_TRUNC|O_WRONLY, 0444);
+	if (fd == -1) {
+		DEBUG(1,(__location__ ": Unable to open %s - %s\n", tmp_path, strerror(errno)));
+		talloc_free(tmp_ctx);
+		return;
+	}
+
+	dprintf(fd, "/* this file is auto-generated - do not edit */\n");
+	dprintf(fd, "update-policy {\n");
+	dprintf(fd, "\tgrant %s ms-self * A AAAA;\n", realm);
+	dprintf(fd, "\tgrant administrator@%s wildcard * A AAAA SRV CNAME TXT;\n", realm);
+
+	for (i=0; i<res->count; i++) {
+		const char *acctname;
+		acctname = ldb_msg_find_attr_as_string(res->msgs[i],
+						       "sAMAccountName", NULL);
+		if (!acctname) continue;
+		dprintf(fd, "\tgrant %s@%s wildcard * A AAAA SRV CNAME;\n",
+			acctname, realm);
+	}
+	dprintf(fd, "};\n");
+	close(fd);
+
+	if (file_compare(tmp_path, path) == true) {
+		talloc_free(tmp_ctx);
+		return;
+	}
+
+	if (rename(tmp_path, path) != 0) {
+		DEBUG(0,(__location__ ": Failed to rename %s to %s - %s\n",
+			 tmp_path, path, strerror(errno)));
+		talloc_free(tmp_ctx);
+		return;
+	}
+
+	DEBUG(1,("Loaded new DNS update grant rules\n"));
+
+	rndc_cmd = lp_parm_string(service->task->lp_ctx, NULL, "dnsupdate", "rndc reload command");
+	if (!rndc_cmd) {
+		rndc_cmd = "/usr/sbin/rndc reload";
+	}
+	ret = system(rndc_cmd);
+	if (ret != 0) {
+		DEBUG(0,(__location__ ": Failed rndc reload command: '%s' - %d\n",
+			 rndc_cmd, ret));
+	}
+
+	talloc_free(tmp_ctx);
+}
+
+static NTSTATUS dnsupdate_periodic_schedule(struct dnsupdate_service *service);
+
+/*
+  called every dnsupdate:interval seconds
+ */
+static void dnsupdate_periodic_handler_te(struct tevent_context *ev, struct tevent_timer *te,
+					  struct timeval t, void *ptr)
+{
+	struct dnsupdate_service *service = talloc_get_type(ptr, struct dnsupdate_service);
+
+	dnsupdate_rebuild(service);
+	dnsupdate_periodic_schedule(service);
+}
+
+
+static NTSTATUS dnsupdate_periodic_schedule(struct dnsupdate_service *service)
+{
+	service->periodic.te = tevent_add_timer(service->task->event_ctx, service,
+						timeval_current_ofs(service->periodic.interval, 0),
+						dnsupdate_periodic_handler_te, service);
+	NT_STATUS_HAVE_NO_MEMORY(service->periodic.te);
+	return NT_STATUS_OK;
+}
+
+/*
+  startup the dns update task
+*/
+static void dnsupdate_task_init(struct task_server *task)
+{
+	NTSTATUS status;
+	struct dnsupdate_service *service;
+
+	if (lp_server_role(task->lp_ctx) != ROLE_DOMAIN_CONTROLLER) {
+		/* not useful for non-DC */
+		return;
+	}
+
+	task_server_set_title(task, "task[dnsupdate]");
+
+	service = talloc_zero(task, struct dnsupdate_service);
+	if (!service) {
+		task_server_terminate(task, "dnsupdate_task_init: out of memory", true);
+		return;
+	}
+	service->task		= task;
+	task->private_data	= service;
+
+	service->system_session_info = system_session(service->task->lp_ctx);
+	if (!service->system_session_info) {
+		task_server_terminate(task,
+				      "dnsupdate: Failed to obtain server credentials\n",
+				      true);
+		return;
+	}
+
+	service->samdb = samdb_connect(service, service->task->event_ctx, task->lp_ctx,
+				       service->system_session_info);
+	if (!service->samdb) {
+		task_server_terminate(task, "dnsupdate: Failed to connect to local samdb\n",
+				      true);
+		return;
+	}
+
+	service->periodic.interval	= lp_parm_int(task->lp_ctx, NULL,
+						      "dnsupdate", "interval", 60); /* in seconds */
+
+	status = dnsupdate_periodic_schedule(service);
+	if (!NT_STATUS_IS_OK(status)) {
+		task_server_terminate(task, talloc_asprintf(task,
+				      "dnsupdate: Failed to periodic schedule: %s\n",
+							    nt_errstr(status)), true);
+		return;
+	}
+
+	irpc_add_name(task->msg_ctx, "dnsupdate");
+
+	/* create the intial file */
+	dnsupdate_rebuild(service);
+
+}
+
+/*
+  register ourselves as a available server
+*/
+NTSTATUS server_service_dnsupdate_init(void)
+{
+	return register_server_service("dnsupdate", dnsupdate_task_init);
+}