From: Ondřej Surý <ondrej@sury.org>
Date: Tue, 17 Mar 2026 23:28:04 +0000 (+0100)
Subject: Implement RFC 3645 Section 4.1.1 key expiry check in TKEY
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=5e10fdc29552d601adfea2ef63b7121877fdee74;p=thirdparty%2Fbind9.git

Implement RFC 3645 Section 4.1.1 key expiry check in TKEY

Check for existing non-expired TSIG keys before accepting a new
GSS-API negotiation.  Per RFC 3645 Section 4.1.1:

- If a key exists and has not expired, reject with BADNAME
- If a key exists but has expired, delete it and start fresh

Previously, an expired GSS key would permanently block
re-negotiation for that name until the server was restarted.

Use BADKEY rather than BADNAME to avoid creating an oracle for
key name enumeration by unauthenticated attackers.
---

diff --git a/lib/dns/tkey.c b/lib/dns/tkey.c
index f09edc2a9c4..42deb423a2b 100644
--- a/lib/dns/tkey.c
+++ b/lib/dns/tkey.c
@@ -178,15 +178,6 @@ process_gsstkey(dns_message_t *msg, dns_name_t *name, dns_rdata_tkey_t *tkeyin,
 		return ISC_R_SUCCESS;
 	}
 
-	/*
-	 * XXXDCL need to check for key expiry per 4.1.1
-	 * XXXDCL need a way to check fully established, perhaps w/key_flags
-	 */
-	result = dns_tsigkey_find(&tsigkey, name, &tkeyin->algorithm, ring);
-	if (result == ISC_R_SUCCESS) {
-		gss_ctx = dst_key_getgssctx(tsigkey->key);
-	}
-
 	intoken = (isc_region_t){ tkeyin->key, tkeyin->keylen };
 	result = dst_gssapi_acceptctx(tctx->gssapi_keytab, &intoken, &outtoken,
 				      &gss_ctx, principal, tctx->mctx);
@@ -430,10 +421,26 @@ dns_tkey_processquery(dns_message_t *msg, dns_tkeyctx_t *tctx,
 
 		result = dns_tsigkey_find(&tsigkey, keyname, NULL, ring);
 		if (result == ISC_R_SUCCESS) {
-			tkeyout.error = dns_tsigerror_badname;
-			dns_tsigkey_detach(&tsigkey);
-			break;
-		} else if (result == ISC_R_NOTFOUND) {
+			/*
+			 * RFC 3645 Section 4.1.1: if the key exists
+			 * but has expired, delete it and allow
+			 * re-negotiation.  We use BADKEY rather than
+			 * BADNAME to avoid creating an oracle for key
+			 * name enumeration.
+			 */
+			if (tsigkey->inception != tsigkey->expire &&
+			    tsigkey->expire <= isc_stdtime_now())
+			{
+				dns_tsigkey_delete(tsigkey);
+				dns_tsigkey_detach(&tsigkey);
+				result = ISC_R_NOTFOUND;
+			} else {
+				tkeyout.error = dns_tsigerror_badkey;
+				dns_tsigkey_detach(&tsigkey);
+				break;
+			}
+		}
+		if (result == ISC_R_NOTFOUND || tsigkey == NULL) {
 			CHECK(process_gsstkey(msg, keyname, &tkeyin, tctx,
 					      &tkeyout, ring));
 			break;