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Date:      Mon, 1 Oct 2018 14:05:32 +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: r339042 - head/sys/netinet
Message-ID:  <201810011405.w91E5WbA032630@repo.freebsd.org>
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Author: tuexen
Date: Mon Oct  1 14:05:31 2018
New Revision: 339042
URL: https://svnweb.freebsd.org/changeset/base/339042

Log:
  Mitigate providing a timing signal if the COOKIE or AUTH
  validation fails.
  Thanks to jmg@ for reporting the issue, which was discussed in
  https://admbugs.freebsd.org/show_bug.cgi?id=878
  
  Approved by:            re (TBD@)
  MFC after:              1 week

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

Modified: head/sys/netinet/sctp_auth.c
==============================================================================
--- head/sys/netinet/sctp_auth.c	Mon Oct  1 14:02:29 2018	(r339041)
+++ head/sys/netinet/sctp_auth.c	Mon Oct  1 14:05:31 2018	(r339042)
@@ -1706,7 +1706,7 @@ sctp_handle_auth(struct sctp_tcb *stcb, struct sctp_au
 	    m, offset, computed_digest);
 
 	/* compare the computed digest with the one in the AUTH chunk */
-	if (memcmp(digest, computed_digest, digestlen) != 0) {
+	if (timingsafe_bcmp(digest, computed_digest, digestlen) != 0) {
 		SCTP_STAT_INCR(sctps_recvauthfailed);
 		SCTPDBG(SCTP_DEBUG_AUTH1,
 		    "SCTP Auth: HMAC digest check failed\n");

Modified: head/sys/netinet/sctp_input.c
==============================================================================
--- head/sys/netinet/sctp_input.c	Mon Oct  1 14:02:29 2018	(r339041)
+++ head/sys/netinet/sctp_input.c	Mon Oct  1 14:05:31 2018	(r339042)
@@ -2554,7 +2554,7 @@ sctp_handle_cookie_echo(struct mbuf *m, int iphlen, in
 		return (NULL);
 	}
 	/* compare the received digest with the computed digest */
-	if (memcmp(calc_sig, sig, SCTP_SIGNATURE_SIZE) != 0) {
+	if (timingsafe_bcmp(calc_sig, sig, SCTP_SIGNATURE_SIZE) != 0) {
 		/* try the old cookie? */
 		if ((cookie->time_entered.tv_sec == (long)ep->time_of_secret_change) &&
 		    (ep->current_secret_number != ep->last_secret_number)) {
@@ -2563,7 +2563,7 @@ sctp_handle_cookie_echo(struct mbuf *m, int iphlen, in
 			    (uint8_t *)ep->secret_key[(int)ep->last_secret_number],
 			    SCTP_SECRET_SIZE, m, cookie_offset, calc_sig, 0);
 			/* compare */
-			if (memcmp(calc_sig, sig, SCTP_SIGNATURE_SIZE) == 0)
+			if (timingsafe_bcmp(calc_sig, sig, SCTP_SIGNATURE_SIZE) == 0)
 				cookie_ok = 1;
 		}
 	} else {

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