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Date:      Tue, 29 Sep 2020 09:36:07 +0000 (UTC)
From:      Michael Tuexen <tuexen@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r366248 - head/sys/netinet
Message-ID:  <202009290936.08T9a7vv062087@repo.freebsd.org>
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Author: tuexen
Date: Tue Sep 29 09:36:06 2020
New Revision: 366248
URL: https://svnweb.freebsd.org/changeset/base/366248

Log:
  Improve the input validation and processing of cookies.
  This avoids setting the association in an inconsistent
  state, which could result in a use-after-free situation.
  This can be triggered by a malicious peer, if the peer
  can modify the cookie without the local endpoint recognizing
  it.
  Thanks to Ned Williamson for reporting the issue.
  
  MFC after:		3 days

Modified:
  head/sys/netinet/sctp_input.c
  head/sys/netinet/sctp_pcb.c

Modified: head/sys/netinet/sctp_input.c
==============================================================================
--- head/sys/netinet/sctp_input.c	Tue Sep 29 09:25:52 2020	(r366247)
+++ head/sys/netinet/sctp_input.c	Tue Sep 29 09:36:06 2020	(r366248)
@@ -2032,10 +2032,6 @@ sctp_process_cookie_new(struct mbuf *m, int iphlen, in
 		    vrf_id, port);
 		return (NULL);
 	}
-	/* get the correct sctp_nets */
-	if (netp)
-		*netp = sctp_findnet(stcb, init_src);
-
 	asoc = &stcb->asoc;
 	/* get scope variables out of cookie */
 	asoc->scope.ipv4_local_scope = cookie->ipv4_scope;
@@ -2074,10 +2070,7 @@ sctp_process_cookie_new(struct mbuf *m, int iphlen, in
 	asoc->advanced_peer_ack_point = asoc->last_acked_seq;
 
 	/* process the INIT info (peer's info) */
-	if (netp)
-		retval = sctp_process_init(init_cp, stcb);
-	else
-		retval = 0;
+	retval = sctp_process_init(init_cp, stcb);
 	if (retval < 0) {
 		(void)sctp_free_assoc(inp, stcb, SCTP_NORMAL_PROC,
 		    SCTP_FROM_SCTP_INPUT + SCTP_LOC_19);
@@ -2191,19 +2184,21 @@ sctp_process_cookie_new(struct mbuf *m, int iphlen, in
 		 */
 		;
 	}
-	/* since we did not send a HB make sure we don't double things */
-	if ((netp) && (*netp))
-		(*netp)->hb_responded = 1;
-
 	if (stcb->asoc.sctp_autoclose_ticks &&
 	    sctp_is_feature_on(inp, SCTP_PCB_FLAGS_AUTOCLOSE)) {
 		sctp_timer_start(SCTP_TIMER_TYPE_AUTOCLOSE, inp, stcb, NULL);
 	}
 	(void)SCTP_GETTIME_TIMEVAL(&stcb->asoc.time_entered);
-	if ((netp != NULL) && (*netp != NULL)) {
+	*netp = sctp_findnet(stcb, init_src);
+	if (*netp != NULL) {
 		struct timeval old;
 
-		/* calculate the RTT and set the encaps port */
+		/*
+		 * Since we did not send a HB, make sure we don't double
+		 * things.
+		 */
+		(*netp)->hb_responded = 1;
+		/* Calculate the RTT. */
 		old.tv_sec = cookie->time_entered.tv_sec;
 		old.tv_usec = cookie->time_entered.tv_usec;
 		sctp_calculate_rto(stcb, asoc, *netp, &old, SCTP_RTT_FROM_NON_DATA);

Modified: head/sys/netinet/sctp_pcb.c
==============================================================================
--- head/sys/netinet/sctp_pcb.c	Tue Sep 29 09:25:52 2020	(r366247)
+++ head/sys/netinet/sctp_pcb.c	Tue Sep 29 09:36:06 2020	(r366248)
@@ -4242,7 +4242,9 @@ sctp_aloc_assoc(struct sctp_inpcb *inp, struct sockadd
 			if ((ntohs(sin->sin_port) == 0) ||
 			    (sin->sin_addr.s_addr == INADDR_ANY) ||
 			    (sin->sin_addr.s_addr == INADDR_BROADCAST) ||
-			    IN_MULTICAST(ntohl(sin->sin_addr.s_addr))) {
+			    IN_MULTICAST(ntohl(sin->sin_addr.s_addr)) ||
+			    (((inp->sctp_flags & SCTP_PCB_FLAGS_BOUND_V6) != 0) &&
+			    (SCTP_IPV6_V6ONLY(inp) != 0))) {
 				/* Invalid address */
 				SCTP_INP_RUNLOCK(inp);
 				SCTP_LTRACE_ERR_RET(inp, NULL, NULL, SCTP_FROM_SCTP_PCB, EINVAL);
@@ -4261,7 +4263,8 @@ sctp_aloc_assoc(struct sctp_inpcb *inp, struct sockadd
 			sin6 = (struct sockaddr_in6 *)firstaddr;
 			if ((ntohs(sin6->sin6_port) == 0) ||
 			    IN6_IS_ADDR_UNSPECIFIED(&sin6->sin6_addr) ||
-			    IN6_IS_ADDR_MULTICAST(&sin6->sin6_addr)) {
+			    IN6_IS_ADDR_MULTICAST(&sin6->sin6_addr) ||
+			    ((inp->sctp_flags & SCTP_PCB_FLAGS_BOUND_V6) == 0)) {
 				/* Invalid address */
 				SCTP_INP_RUNLOCK(inp);
 				SCTP_LTRACE_ERR_RET(inp, NULL, NULL, SCTP_FROM_SCTP_PCB, EINVAL);

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