Trigger retransmission only for fragment 1/x, otherwise each received

fragment can trigger retransmission of the full fragment queue.

From RFC7383, 2.6.1:
"[...] that even MUST only trigger a retransmission of the response message
 (fragmented or no) if the Fragment Number field in the received
 fragments is set to 1; otherwise, it MUST be ignored."

from markus

sbin/iked/iked.h

@@ -1,4 +1,4 @@
-/*	$OpenBSD: iked.h,v 1.229 2024/02/15 20:10:45 tobhe Exp $	*/
+/*	$OpenBSD: iked.h,v 1.230 2024/03/02 16:16:07 tobhe Exp $	*/
 
 /*
  * Copyright (c) 2019 Tobias Heider <tobias.heider@stusta.de>
@@ -656,6 +656,7 @@ struct iked_message {
 	struct iked_addr	*msg_cp_addr;	/* requested address */
 	struct iked_addr	*msg_cp_addr6;	/* requested address */
 	struct iked_addr	*msg_cp_dns;	/* requested dns */
+	uint16_t		 msg_frag_num;
 
 	/* MOBIKE */
 	int			 msg_update_sa_addresses;
@@ -1130,7 +1131,7 @@ struct iked_socket *
 int	 ikev2_msg_enqueue(struct iked *, struct iked_msgqueue *,
 	    struct iked_message *, int);
 int	 ikev2_msg_retransmit_response(struct iked *, struct iked_sa *,
-	    struct iked_message *, uint8_t);
+	    struct iked_message *, struct ike_header *);
 void	 ikev2_msg_prevail(struct iked *, struct iked_msgqueue *,
 	    struct iked_message *);
 void	 ikev2_msg_dispose(struct iked *, struct iked_msgqueue *,
@@ -1143,6 +1144,8 @@ struct iked_msg_retransmit *
 /* ikev2_pld.c */
 int	 ikev2_pld_parse(struct iked *, struct ike_header *,
 	    struct iked_message *, size_t);
+int	 ikev2_pld_parse_quick(struct iked *, struct ike_header *,
+	    struct iked_message *, size_t);
 
 /* eap.c */
 int	 eap_parse(struct iked *, const struct iked_sa *, struct iked_message*,

sbin/iked/ikev2.c

@@ -1,4 +1,4 @@
-/*	$OpenBSD: ikev2.c,v 1.384 2024/02/15 19:11:00 tobhe Exp $	*/
+/*	$OpenBSD: ikev2.c,v 1.385 2024/03/02 16:16:07 tobhe Exp $	*/
 
 /*
  * Copyright (c) 2019 Tobias Heider <tobias.heider@stusta.de>
@@ -756,8 +756,8 @@ ikev2_recv(struct iked *env, struct iked_message *msg)
 		 * See if we have responded to this request before
 		 * For return values 0 and -1 we have.
 		 */
-		if ((r = ikev2_msg_retransmit_response(env, sa, msg,
-		    hdr->ike_exchange)) != -2) {
+		if ((r = ikev2_msg_retransmit_response(env, sa, msg, hdr))
+		     != -2) {
 			if (r == -1) {
 				log_warn("%s: failed to retransmit a "
 				    "response", __func__);

sbin/iked/ikev2_msg.c

@@ -1,4 +1,4 @@
-/*	$OpenBSD: ikev2_msg.c,v 1.100 2023/08/04 19:06:25 claudio Exp $	*/
+/*	$OpenBSD: ikev2_msg.c,v 1.101 2024/03/02 16:16:07 tobhe Exp $	*/
 
 /*
  * Copyright (c) 2019 Tobias Heider <tobias.heider@stusta.de>
@@ -1275,15 +1275,25 @@ ikev2_msg_lookup(struct iked *env, struct iked_msgqueue *queue,
 
 int
 ikev2_msg_retransmit_response(struct iked *env, struct iked_sa *sa,
-    struct iked_message *msg, uint8_t exchange)
+    struct iked_message *msg, struct ike_header *hdr)
 {
 	struct iked_msg_retransmit	*mr = NULL;
-	struct iked_message	*m = NULL;
+	struct iked_message		*m = NULL;
 
-	if ((mr = ikev2_msg_lookup(env, &sa->sa_responses, msg, exchange))
-	    == NULL)
+	if ((mr = ikev2_msg_lookup(env, &sa->sa_responses, msg,
+	    hdr->ike_exchange)) == NULL)
 		return (-2);	/* not found */
 
+	if (hdr->ike_nextpayload == IKEV2_PAYLOAD_SKF) {
+		/* only retransmit for fragment number one */
+		if (ikev2_pld_parse_quick(env, hdr, msg,
+		    msg->msg_offset) != 0 || msg->msg_frag_num != 1) {
+			log_debug("%s: ignoring fragment", SPI_SA(sa, __func__));
+			return (0);
+		}
+		log_debug("%s: first fragment", SPI_SA(sa, __func__));
+	}
+
 	TAILQ_FOREACH(m, &mr->mrt_frags, msg_entry) {
 		if (sendtofrom(m->msg_fd, ibuf_data(m->msg_data),
 		    ibuf_size(m->msg_data), 0,
@@ -1295,7 +1305,7 @@ ikev2_msg_retransmit_response(struct iked *env, struct iked_sa *sa,
 		}
 		log_info("%sretransmit %s res %u local %s peer %s",
 		    SPI_SA(sa, NULL),
-		    print_map(exchange, ikev2_exchange_map),
+		    print_map(hdr->ike_exchange, ikev2_exchange_map),
 		    m->msg_msgid,
 		    print_addr(&m->msg_local),
 		    print_addr(&m->msg_peer));

sbin/iked/ikev2_pld.c

@@ -1,4 +1,4 @@
-/*	$OpenBSD: ikev2_pld.c,v 1.133 2023/09/02 18:36:30 tobhe Exp $	*/
+/*	$OpenBSD: ikev2_pld.c,v 1.134 2024/03/02 16:16:07 tobhe Exp $	*/
 
 /*
  * Copyright (c) 2019 Tobias Heider <tobias.heider@stusta.de>
@@ -2103,3 +2103,79 @@ ikev2_pld_eap(struct iked *env, struct ikev2_payload *pld,
 
 	return (0);
 }
+
+/* parser for the initial IKE_AUTH payload, does not require msg_sa */
+int
+ikev2_pld_parse_quick(struct iked *env, struct ike_header *hdr,
+    struct iked_message *msg, size_t offset)
+{
+	struct ikev2_payload	 pld;
+	struct ikev2_frag_payload frag;
+	uint8_t			*msgbuf = ibuf_data(msg->msg_data);
+	uint8_t			*buf;
+	size_t			 len, total, left;
+	size_t			 length;
+	unsigned int		 payload;
+
+	log_debug("%s: header ispi %s rspi %s"
+	    " nextpayload %s version 0x%02x exchange %s flags 0x%02x"
+	    " msgid %d length %u response %d", __func__,
+	    print_spi(betoh64(hdr->ike_ispi), 8),
+	    print_spi(betoh64(hdr->ike_rspi), 8),
+	    print_map(hdr->ike_nextpayload, ikev2_payload_map),
+	    hdr->ike_version,
+	    print_map(hdr->ike_exchange, ikev2_exchange_map),
+	    hdr->ike_flags,
+	    betoh32(hdr->ike_msgid),
+	    betoh32(hdr->ike_length),
+	    msg->msg_response);
+
+	length = betoh32(hdr->ike_length);
+
+	if (ibuf_size(msg->msg_data) < length) {
+		log_debug("%s: short message", __func__);
+		return (-1);
+	}
+
+	offset += sizeof(*hdr);
+
+	/* Bytes left in datagram. */
+	total = length - offset;
+
+	payload = hdr->ike_nextpayload;
+
+	while (payload != 0 && offset < length) {
+		if (ikev2_validate_pld(msg, offset, total, &pld))
+			return (-1);
+
+		log_debug("%s: %spayload %s"
+		    " nextpayload %s critical 0x%02x length %d",
+		    __func__, msg->msg_e ? "decrypted " : "",
+		    print_map(payload, ikev2_payload_map),
+		    print_map(pld.pld_nextpayload, ikev2_payload_map),
+		    pld.pld_reserved & IKEV2_CRITICAL_PAYLOAD,
+		    betoh16(pld.pld_length));
+
+		/* Skip over generic payload header. */
+		offset += sizeof(pld);
+		total -= sizeof(pld);
+		left = betoh16(pld.pld_length) - sizeof(pld);
+
+		switch (payload) {
+		case IKEV2_PAYLOAD_SKF:
+			len = left;
+			buf = msgbuf + offset;
+			if (len < sizeof(frag))
+				return (-1);
+			memcpy(&frag, buf, sizeof(frag));
+			msg->msg_frag_num = betoh16(frag.frag_num);
+			break;
+		}
+
+		payload = pld.pld_nextpayload;
+		offset += left;
+		total -= left;
+	}
+
+	return (0);
+}