From d31d0981286a3c9383f46867ff0a11ee377ecaf1 Mon Sep 17 00:00:00 2001 From: Fabrice Fontaine Date: Sat, 29 Feb 2020 23:46:43 +0100 Subject: [PATCH] package/suricata: fix CVE-2019-18792 An issue was discovered in Suricata 5.0.0. It is possible to bypass/evade any tcp based signature by overlapping a TCP segment with a fake FIN packet. The fake FIN packet is injected just before the PUSH ACK packet we want to bypass. The PUSH ACK packet (containing the data) will be ignored by Suricata because it overlaps the FIN packet (the sequence and ack number are identical in the two packets). The client will ignore the fake FIN packet because the ACK flag is not set. Both linux and windows clients are ignoring the injected packet. Signed-off-by: Fabrice Fontaine Signed-off-by: Yann E. MORIN (cherry picked from commit 2914843b394cf905f8bec98a23ba44c692f4b862) Signed-off-by: Peter Korsgaard --- ...004-stream-reject-broken-ACK-packets.patch | 40 +++++++++++++++++++ package/suricata/suricata.mk | 3 ++ 2 files changed, 43 insertions(+) create mode 100644 package/suricata/0004-stream-reject-broken-ACK-packets.patch diff --git a/package/suricata/0004-stream-reject-broken-ACK-packets.patch b/package/suricata/0004-stream-reject-broken-ACK-packets.patch new file mode 100644 index 0000000000..9670d73158 --- /dev/null +++ b/package/suricata/0004-stream-reject-broken-ACK-packets.patch @@ -0,0 +1,40 @@ +From 1c63d3905852f746ccde7e2585600b2199cefb4b Mon Sep 17 00:00:00 2001 +From: Victor Julien +Date: Thu, 21 Nov 2019 16:10:21 +0100 +Subject: [PATCH] stream: reject broken ACK packets + +Fix evasion posibility by rejecting packets with a broken ACK field. +These packets have a non-0 ACK field, but do not have a ACK flag set. + +Bug #3324. + +Reported-by: Nicolas Adba +(cherry picked from commit fa692df37a796c3330c81988d15ef1a219afc006) +[Retrieved from: +https://github.com/OISF/suricata/commit/1c63d3905852f746ccde7e2585600b2199cefb4b] +Signed-off-by: Fabrice Fontaine +--- + src/stream-tcp.c | 3 ++- + 1 file changed, 2 insertions(+), 1 deletion(-) + +diff --git a/src/stream-tcp.c b/src/stream-tcp.c +index 35e489acba..8653d670c6 100644 +--- a/src/stream-tcp.c ++++ b/src/stream-tcp.c +@@ -4759,6 +4759,7 @@ int StreamTcpPacket (ThreadVars *tv, Packet *p, StreamTcpThread *stt, + /* broken TCP http://ask.wireshark.org/questions/3183/acknowledgment-number-broken-tcp-the-acknowledge-field-is-nonzero-while-the-ack-flag-is-not-set */ + if (!(p->tcph->th_flags & TH_ACK) && TCP_GET_ACK(p) != 0) { + StreamTcpSetEvent(p, STREAM_PKT_BROKEN_ACK); ++ goto error; + } + + /* If we are on IPS mode, and got a drop action triggered from +@@ -6883,7 +6884,7 @@ static int StreamTcpTest10 (void) + + tcph.th_win = htons(5480); + tcph.th_seq = htonl(10); +- tcph.th_ack = htonl(11); ++ tcph.th_ack = 0; + tcph.th_flags = TH_SYN; + p->tcph = &tcph; + diff --git a/package/suricata/suricata.mk b/package/suricata/suricata.mk index ebd830ea77..3857c7b202 100644 --- a/package/suricata/suricata.mk +++ b/package/suricata/suricata.mk @@ -11,6 +11,9 @@ SURICATA_LICENSE_FILES = COPYING LICENSE # We're patching configure.ac SURICATA_AUTORECONF = YES +# 0004-stream-reject-broken-ACK-packets.patch +SURICATA_IGNORE_CVES += CVE-2019-18792 + SURICATA_DEPENDENCIES = \ host-pkgconf \ $(if $(BR2_PACKAGE_JANSSON),jansson) \