From 7a414c941a0fca9f111c2f3d405eb16c71c8374d Mon Sep 17 00:00:00 2001 From: kp Date: Fri, 1 Mar 2019 18:12:07 +0000 Subject: [PATCH] MFC r344691: pf: IPv6 fragments with malformed extension headers could be erroneously passed by pf or cause a panic We mistakenly used the extoff value from the last packet to patch the next_header field. If a malicious host sends a chain of fragmented packets where the first packet and the final packet have different lengths or number of extension headers we'd patch the next_header at the wrong offset. This can potentially lead to panics or rule bypasses. Reported by: Corentin Bayet, Nicolas Collignon, Luca Moro at Synacktiv Approved by: so Obtained from: OpenBSD Security: CVE-2019-5597 --- sys/netpfil/pf/pf_norm.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/sys/netpfil/pf/pf_norm.c b/sys/netpfil/pf/pf_norm.c index ee7d5e21f9c..e096b8a07c3 100644 --- a/sys/netpfil/pf/pf_norm.c +++ b/sys/netpfil/pf/pf_norm.c @@ -659,11 +659,11 @@ pf_reassemble6(struct mbuf **m0, struct ip6_hdr *ip6, struct ip6_frag *fraghdr, } /* We have all the data. */ + frent = TAILQ_FIRST(&frag->fr_queue); + KASSERT(frent != NULL, ("frent != NULL")); extoff = frent->fe_extoff; maxlen = frag->fr_maxlen; frag_id = frag->fr_id; - frent = TAILQ_FIRST(&frag->fr_queue); - KASSERT(frent != NULL, ("frent != NULL")); total = TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_off + TAILQ_LAST(&frag->fr_queue, pf_fragq)->fe_len; hdrlen = frent->fe_hdrlen - sizeof(struct ip6_frag); -- 2.45.0