From: Petr Špaček <pspacek@isc.org>
Date: Thu, 16 May 2024 10:10:41 +0000 (+0200)
Subject: Remove support for SIG(0) message verification
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=9dc5c3709ffcfa3b9c8ba81fd28baebafe097f44;p=thirdparty%2Fbind9.git

Remove support for SIG(0) message verification

(cherry picked from commit 857fd5c346e3309ee8e280c29174b46579af5a13)
---

diff --git a/bin/named/client.c b/bin/named/client.c
index 15fcfcd3c30..761d72a9b2a 100644
--- a/bin/named/client.c
+++ b/bin/named/client.c
@@ -3012,6 +3012,12 @@ client_request(isc_task_t *task, isc_event_t *event) {
 		ns_client_log(client, DNS_LOGCATEGORY_SECURITY,
 			      NS_LOGMODULE_CLIENT, ISC_LOG_DEBUG(3),
 			      "request is signed by a nonauthoritative key");
+	} else if (result == DNS_R_NOTVERIFIEDYET &&
+		   client->message->sig0 != NULL) {
+		ns_client_log(client, DNS_LOGCATEGORY_SECURITY,
+			      NS_LOGMODULE_CLIENT, ISC_LOG_DEBUG(3),
+			      "request has a SIG(0) signature but its support "
+			      "was removed (CVE-2024-1975)");
 	} else {
 		char tsigrcode[64];
 		isc_buffer_t b;
diff --git a/lib/dns/message.c b/lib/dns/message.c
index a44eb2d1e95..03ed2a178dc 100644
--- a/lib/dns/message.c
+++ b/lib/dns/message.c
@@ -3373,102 +3373,24 @@ dns_message_dumpsig(dns_message_t *msg, char *txt1) {
 
 isc_result_t
 dns_message_checksig(dns_message_t *msg, dns_view_t *view) {
-	isc_buffer_t b, msgb;
+	isc_buffer_t msgb;
 
 	REQUIRE(DNS_MESSAGE_VALID(msg));
 
-	if (msg->tsigkey == NULL && msg->tsig == NULL && msg->sig0 == NULL)
+	if (msg->tsigkey == NULL && msg->tsig == NULL) {
 		return (ISC_R_SUCCESS);
+	}
 
 	INSIST(msg->saved.base != NULL);
 	isc_buffer_init(&msgb, msg->saved.base, msg->saved.length);
 	isc_buffer_add(&msgb, msg->saved.length);
-	if (msg->tsigkey != NULL || msg->tsig != NULL) {
 #ifdef SKAN_MSG_DEBUG
-		dns_message_dumpsig(msg, "dns_message_checksig#1");
-#endif
-		if (view != NULL)
-			return (dns_view_checksig(view, &msgb, msg));
-		else
-			return (dns_tsig_verify(&msgb, msg, NULL, NULL));
+	dns_message_dumpsig(msg, "dns_message_checksig#1");
+#endif /* ifdef SKAN_MSG_DEBUG */
+	if (view != NULL) {
+		return (dns_view_checksig(view, &msgb, msg));
 	} else {
-		dns_rdata_t rdata = DNS_RDATA_INIT;
-		dns_rdata_sig_t sig;
-		dns_rdataset_t keyset;
-		isc_result_t result;
-
-		result = dns_rdataset_first(msg->sig0);
-		INSIST(result == ISC_R_SUCCESS);
-		dns_rdataset_current(msg->sig0, &rdata);
-
-		/*
-		 * This can occur when the message is a dynamic update, since
-		 * the rdata length checking is relaxed.  This should not
-		 * happen in a well-formed message, since the SIG(0) is only
-		 * looked for in the additional section, and the dynamic update
-		 * meta-records are in the prerequisite and update sections.
-		 */
-		if (rdata.length == 0)
-			return (ISC_R_UNEXPECTEDEND);
-
-		result = dns_rdata_tostruct(&rdata, &sig, msg->mctx);
-		if (result != ISC_R_SUCCESS)
-			return (result);
-
-		dns_rdataset_init(&keyset);
-		if (view == NULL)
-			return (DNS_R_KEYUNAUTHORIZED);
-		result = dns_view_simplefind(view, &sig.signer,
-					     dns_rdatatype_key /* SIG(0) */,
-					     0, 0, false, &keyset, NULL);
-
-		if (result != ISC_R_SUCCESS) {
-			/* XXXBEW Should possibly create a fetch here */
-			result = DNS_R_KEYUNAUTHORIZED;
-			goto freesig;
-		} else if (keyset.trust < dns_trust_secure) {
-			/* XXXBEW Should call a validator here */
-			result = DNS_R_KEYUNAUTHORIZED;
-			goto freesig;
-		}
-		result = dns_rdataset_first(&keyset);
-		INSIST(result == ISC_R_SUCCESS);
-		for (;
-		     result == ISC_R_SUCCESS;
-		     result = dns_rdataset_next(&keyset))
-		{
-			dst_key_t *key = NULL;
-
-			dns_rdata_reset(&rdata);
-			dns_rdataset_current(&keyset, &rdata);
-			isc_buffer_init(&b, rdata.data, rdata.length);
-			isc_buffer_add(&b, rdata.length);
-
-			result = dst_key_fromdns(&sig.signer, rdata.rdclass,
-						 &b, view->mctx, &key);
-			if (result != ISC_R_SUCCESS)
-				continue;
-			if (dst_key_alg(key) != sig.algorithm ||
-			    dst_key_id(key) != sig.keyid ||
-			    !(dst_key_proto(key) == DNS_KEYPROTO_DNSSEC ||
-			      dst_key_proto(key) == DNS_KEYPROTO_ANY))
-			{
-				dst_key_free(&key);
-				continue;
-			}
-			result = dns_dnssec_verifymessage(&msgb, msg, key);
-			dst_key_free(&key);
-			if (result == ISC_R_SUCCESS)
-				break;
-		}
-		if (result == ISC_R_NOMORE)
-			result = DNS_R_KEYUNAUTHORIZED;
-
- freesig:
-		if (dns_rdataset_isassociated(&keyset))
-			dns_rdataset_disassociate(&keyset);
-		dns_rdata_freestruct(&sig);
-		return (result);
+		return (dns_tsig_verify(&msgb, msg, NULL, NULL));
 	}
 }