Date: Tue, 14 Aug 2018 18:12:02 +0000 (UTC) From: "Jonathan T. Looney" <jtl@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-11@freebsd.org Subject: svn commit: r337801 - stable/11/sys/netinet6 Message-ID: <201808141812.w7EIC2i1042899@repo.freebsd.org>
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Author: jtl Date: Tue Aug 14 18:12:02 2018 New Revision: 337801 URL: https://svnweb.freebsd.org/changeset/base/337801 Log: MFC r337784: Drop 0-byte IPv6 fragments. Currently, we process IPv6 fragments with 0 bytes of payload, add them to the reassembly queue, and do not recognize them as duplicating or overlapping with adjacent 0-byte fragments. An attacker can exploit this to create long fragment queues. There is no legitimate reason for a fragment with no payload. However, because IPv6 packets with an empty payload are acceptable, allow an "atomic" fragment with no payload. Approved by: so Security: FreeBSD-SA-18:10.ip Security: CVE-2018-6923 Modified: stable/11/sys/netinet6/frag6.c Directory Properties: stable/11/ (props changed) Modified: stable/11/sys/netinet6/frag6.c ============================================================================== --- stable/11/sys/netinet6/frag6.c Tue Aug 14 18:11:06 2018 (r337800) +++ stable/11/sys/netinet6/frag6.c Tue Aug 14 18:12:02 2018 (r337801) @@ -269,6 +269,16 @@ frag6_input(struct mbuf **mp, int *offp, int proto) return (ip6f->ip6f_nxt); } + /* Get fragment length and discard 0-byte fragments. */ + frgpartlen = sizeof(struct ip6_hdr) + ntohs(ip6->ip6_plen) - offset; + if (frgpartlen == 0) { + icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER, + offsetof(struct ip6_hdr, ip6_plen)); + in6_ifstat_inc(dstifp, ifs6_reass_fail); + IP6STAT_INC(ip6s_fragdropped); + return IPPROTO_DONE; + } + hashkeyp = hashkey; memcpy(hashkeyp, &ip6->ip6_src, sizeof(struct in6_addr)); hashkeyp += sizeof(struct in6_addr) / sizeof(*hashkeyp); @@ -365,7 +375,6 @@ frag6_input(struct mbuf **mp, int *offp, int proto) * in size. * If it would exceed, discard the fragment and return an ICMP error. */ - frgpartlen = sizeof(struct ip6_hdr) + ntohs(ip6->ip6_plen) - offset; if (q6->ip6q_unfrglen >= 0) { /* The 1st fragment has already arrived. */ if (q6->ip6q_unfrglen + fragoff + frgpartlen > IPV6_MAXPACKET) {
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