From: Matthijs Mekking <matthijs@isc.org>
Date: Tue, 29 Jan 2019 17:10:27 +0000 (+0100)
Subject: Some thoughts on a solution
X-Git-Tag: v9.13.6~22^2~9
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=1302dea18434c72b083f164e56fb0e15621d3049;p=thirdparty%2Fbind9.git

Some thoughts on a solution
---

diff --git a/lib/dns/tkey.c b/lib/dns/tkey.c
index 87d1b483532..4bade507cce 100644
--- a/lib/dns/tkey.c
+++ b/lib/dns/tkey.c
@@ -497,7 +497,7 @@ process_dhtkey(dns_message_t *msg, dns_name_t *signer, dns_name_t *name,
 }
 
 static isc_result_t
-process_gsstkey(dns_name_t *name, dns_rdata_tkey_t *tkeyin,
+process_gsstkey(dns_message_t *msg, dns_name_t *name, dns_rdata_tkey_t *tkeyin,
 		dns_tkeyctx_t *tctx, dns_rdata_tkey_t *tkeyout,
 		dns_tsig_keyring_t *ring)
 {
@@ -515,7 +515,7 @@ process_gsstkey(dns_name_t *name, dns_rdata_tkey_t *tkeyin,
 	 * You have to define either a gss credential (principal) to
 	 * accept with tkey-gssapi-credential, or you have to
 	 * configure a specific keytab (with tkey-gssapi-keytab) in
-	 * order to use gsstkey
+	 * order to use gsstkey.
 	 */
 	if (tctx->gsscred == NULL && tctx->gssapi_keytab == NULL) {
 		tkey_log("process_gsstkey(): no tkey-gssapi-credential "
@@ -589,7 +589,7 @@ process_gsstkey(dns_name_t *name, dns_rdata_tkey_t *tkeyin,
 		RETERR(dns_tsigkey_createfromkey(name, &tkeyin->algorithm,
 						 dstkey, true, principal,
 						 now, expire, ring->mctx, ring,
-						 NULL));
+						 &tsigkey));
 		dst_key_free(&dstkey);
 		tkeyout->inception = now;
 		tkeyout->expire = expire;
@@ -624,6 +624,29 @@ process_gsstkey(dns_name_t *name, dns_rdata_tkey_t *tkeyin,
 
 	tkey_log("process_gsstkey(): dns_tsigerror_noerror");   /* XXXSRA */
 
+	/*
+	 * [#821] WMM: So we found a TKEY to respond with.  We don't know if
+	 * the request is TSIG signed, but if it is not we need to make an
+	 * effort so that the response is signed, as described in the except
+	 * case in RFC 2845 Section 2.2:
+	 *
+	 *   The server MUST not generate a signed response to an unsigned
+	 *   request, except in case of response to client's unsigned TKEY
+	 *   query if secret key is established on server side after server
+	 *   processed client's query.  Signing responses to unsigned TKEY
+	 *   queries MUST be explicitly specified in the description of an
+	 *   individual secret key establishment algorithm.
+	 *
+	 * In dns_message_reply() it is checked whether to TSIG sign the
+	 * response by checking if msg->tsigkey is non-NULL.  A first naive
+	 * attempt to set the tsigkey here with:
+	 *
+         *      RETERR(dns_message_settsigkey(msg, tsigkey));
+	 *
+	 * is not the right approach, but captures the idea of what needs
+	 * to be done: signal that the msg needs to be TSIG signed.
+	 */
+
 	return (ISC_R_SUCCESS);
 
 failure:
@@ -757,9 +780,9 @@ dns_tkey_processquery(dns_message_t *msg, dns_tkeyctx_t *tctx,
 	result = dns_message_signer(msg, &tsigner);
 	if (result != ISC_R_SUCCESS) {
 		if (tkeyin.mode == DNS_TKEYMODE_GSSAPI &&
-		    result == ISC_R_NOTFOUND)
-		       signer = NULL;
-		else {
+		    result == ISC_R_NOTFOUND) {
+			signer = NULL;
+		} else {
 			tkey_log("dns_tkey_processquery: query was not "
 				 "properly signed - rejecting");
 			result = DNS_R_FORMERR;
@@ -862,7 +885,7 @@ dns_tkey_processquery(dns_message_t *msg, dns_tkeyctx_t *tctx,
 			break;
 		case DNS_TKEYMODE_GSSAPI:
 			tkeyout.error = dns_rcode_noerror;
-			RETERR(process_gsstkey(keyname, &tkeyin, tctx,
+			RETERR(process_gsstkey(msg, keyname, &tkeyin, tctx,
 					       &tkeyout, ring));
 			break;
 		case DNS_TKEYMODE_DELETE:
@@ -879,6 +902,7 @@ dns_tkey_processquery(dns_message_t *msg, dns_tkeyctx_t *tctx,
 	}
 
  failure_with_tkey:
+
 	dns_rdata_init(&rdata);
 	isc_buffer_init(&tkeyoutbuf, tkeyoutdata, sizeof(tkeyoutdata));
 	result = dns_rdata_fromstruct(&rdata, tkeyout.common.rdclass,
@@ -912,6 +936,7 @@ dns_tkey_processquery(dns_message_t *msg, dns_tkeyctx_t *tctx,
 	return (ISC_R_SUCCESS);
 
  failure:
+
 	if (freetkeyin)
 		dns_rdata_freestruct(&tkeyin);
 	if (!ISC_LIST_EMPTY(namelist))