From: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>
Date: Sat, 5 Jun 2021 06:04:55 +0000 (+1200)
Subject: dns scavenging: tombstone deletion uses correct time units
X-Git-Tag: tevent-0.11.0~300
X-Git-Url: http://git.ipfire.org/gitweb/gitweb.cgi?a=commitdiff_plain;h=dbfbbd429766c1c8a161b8950fbed98c5cfbcc16;p=thirdparty%2Fsamba.git

dns scavenging: tombstone deletion uses correct time units

Before we were comparing hours to 1e-7 second units.

Now we do it both ways. That's because in dns_tombstone_records (in
this same file) we have been putting hour timestamps in EntombedTime,
but this field is supposed to have NTTIME timestamps, and those
timestamps won't have updated themselves.

This wouldn't matter much in pure Samba networks if we weren't also
using the correct timestamp in dns_common_replace().

Signed-off-by: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>
---

diff --git a/selftest/knownfail.d/dns-aging b/selftest/knownfail.d/dns-aging
index bcde00bf072..daf13e731ef 100644
--- a/selftest/knownfail.d/dns-aging
+++ b/selftest/knownfail.d/dns-aging
@@ -46,4 +46,3 @@ samba.tests.dns_aging.+test_A_5_days_A_5_days_aging
 samba.tests.dns_aging.+test_A_6_days_AAAA_40_days_no_aging
 samba.tests.dns_aging.+test_A_9_days_AAAA_10_days_no_aging
 samba.tests.dns_aging.+test_samba_scavenging
-samba.tests.dns_aging.+test_tombstone_in_hours_and_nttime
diff --git a/source4/dsdb/kcc/scavenge_dns_records.c b/source4/dsdb/kcc/scavenge_dns_records.c
index be4bfaa213f..e82d834e94f 100644
--- a/source4/dsdb/kcc/scavenge_dns_records.c
+++ b/source4/dsdb/kcc/scavenge_dns_records.c
@@ -372,7 +372,9 @@ NTSTATUS dns_tombstone_records(TALLOC_CTX *mem_ctx,
 
 /*
  * Delete all DNS tombstones that have been around for longer than the server
- * property 'DsTombstoneInterval' which we store in smb.conf
+ * property 'dns_tombstone_interval' which we store in smb.conf, which
+ * corresponds to DsTombstoneInterval in [MS-DNSP] 3.1.1.1.1 "DNS Server
+ * Integer Properties".
  */
 NTSTATUS dns_delete_tombstones(TALLOC_CTX *mem_ctx,
 			       struct ldb_context *samdb,
@@ -381,10 +383,13 @@ NTSTATUS dns_delete_tombstones(TALLOC_CTX *mem_ctx,
 	struct dns_server_zone *zones = NULL;
 	struct dns_server_zone *z = NULL;
 	int ret, i;
+	NTSTATUS status;
 	uint32_t current_time;
+	uint32_t tombstone_interval;
+	uint32_t tombstone_hours;
+	NTTIME tombstone_nttime;
 	enum ndr_err_code ndr_err;
 	struct ldb_result *res = NULL;
-	int tombstone_time;
 	TALLOC_CTX *tmp_ctx = NULL;
 	struct loadparm_context *lp_ctx = NULL;
 	struct ldb_message_element *el = NULL;
@@ -395,10 +400,19 @@ NTSTATUS dns_delete_tombstones(TALLOC_CTX *mem_ctx,
 	current_time = unix_to_dns_timestamp(time(NULL));
 
 	lp_ctx = (struct loadparm_context *)ldb_get_opaque(samdb, "loadparm");
-	tombstone_time =
-	    current_time -
-	    lpcfg_parm_int(
-		lp_ctx, NULL, "dnsserver", "dns_tombstone_interval", 24 * 14);
+	tombstone_interval = lpcfg_parm_ulong(lp_ctx, NULL,
+					      "dnsserver",
+					      "dns_tombstone_interval",
+					      24 * 14);
+
+	tombstone_hours = current_time - tombstone_interval;
+	status = dns_timestamp_to_nt_time(&tombstone_nttime,
+					  tombstone_hours);
+
+	if (!NT_STATUS_IS_OK(status)) {
+		DBG_ERR("DNS timestamp exceeds NTTIME epoch.\n");
+		return NT_STATUS_INTERNAL_ERROR;
+	}
 
 	dns_common_zones(samdb, mem_ctx, NULL, &zones);
 	for (z = zones; z; z = z->next) {
@@ -453,7 +467,27 @@ NTSTATUS dns_delete_tombstones(TALLOC_CTX *mem_ctx,
 				continue;
 			}
 
-			if (rec->data.EntombedTime > tombstone_time) {
+			if (rec->data.EntombedTime > tombstone_nttime) {
+				continue;
+			}
+			/*
+			 * Between 4.9 and 4.14 in some places we saved the
+			 * tombstone time as hours since the start of 1601,
+			 * not in NTTIME ten-millionths of a second units.
+			 *
+			 * We can accomodate these bad values by noting that
+			 * all the realistic timestamps in that measurement
+			 * fall within the first *second* of NTTIME, that is,
+			 * before 1601-01-01 00:00:01; and that these
+			 * timestamps are not realistic for NTTIME timestamps.
+			 *
+			 * Calculation: there are roughly 365.25 * 24 = 8766
+			 * hours per year, and < 500 years since 1601, so
+			 * 4383000 would be a fine threshold. We round up to
+			 * the crore-second (c. 2741CE) in honour of NTTIME.
+			 */
+			if ((rec->data.EntombedTime < 10000000) &&
+			    (rec->data.EntombedTime > tombstone_hours)) {
 				continue;
 			}