From: Philippe Antoine <contact@catenacyber.fr>
Date: Mon, 19 Jul 2021 15:31:32 +0000 (+0200)
Subject: ipv6: decoder event on invalid length
X-Git-Tag: suricata-5.0.8~51
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=87001775bb5cce0ce48e1cb8ed7d2fafcbc467ff;p=thirdparty%2Fsuricata.git

ipv6: decoder event on invalid length

From RFC 2460, section 4.5,
each fragment, except the last one, must have a length
which is a multiple of 8

(cherry picked from commit ca760e305cd74933b685b1bd5be795b24a7d94a7)
---

diff --git a/rules/decoder-events.rules b/rules/decoder-events.rules
index 515e93325d..362bd62e4a 100644
--- a/rules/decoder-events.rules
+++ b/rules/decoder-events.rules
@@ -104,6 +104,7 @@ alert pkthdr any any -> any any (msg:"SURICATA FRAG IPv4 Packet size too large";
 alert pkthdr any any -> any any (msg:"SURICATA FRAG IPv4 Fragmentation overlap"; decode-event:ipv4.frag_overlap; classtype:protocol-command-decode; sid:2200070; rev:2;)
 alert pkthdr any any -> any any (msg:"SURICATA FRAG IPv6 Packet size too large"; decode-event:ipv6.frag_pkt_too_large; classtype:protocol-command-decode; sid:2200071; rev:3;)
 alert pkthdr any any -> any any (msg:"SURICATA FRAG IPv6 Fragmentation overlap"; decode-event:ipv6.frag_overlap; classtype:protocol-command-decode; sid:2200072; rev:2;)
+alert pkthdr any any -> any any (msg:"SURICATA FRAG IPv6 Fragment invalid length"; decode-event:ipv6.frag_invalid_length; classtype:protocol-command-decode; sid:2200119; rev:1;)
 
 # checksum rules
 alert ip any any -> any any (msg:"SURICATA IPv4 invalid checksum"; ipv4-csum:invalid; classtype:protocol-command-decode; sid:2200073; rev:2;)
@@ -145,4 +146,4 @@ alert pkthdr any any -> any any (msg:"SURICATA DCE packet too small"; decode-eve
 
 alert pkthdr any any -> any any (msg:"SURICATA packet with too many layers"; decode-event:too_many_layers; classtype:protocol-command-decode; sid:2200116; rev:1;)
 
-# next sid is 2200117
+# next sid is 2200120
diff --git a/src/decode-events.c b/src/decode-events.c
index a900bc3b15..0a9cfab962 100644
--- a/src/decode-events.c
+++ b/src/decode-events.c
@@ -153,10 +153,26 @@ const struct DecodeEvents_ DEvents[] = {
     { "decoder.sctp.pkt_too_small", SCTP_PKT_TOO_SMALL, },
 
     /* Fragmentation reasembly events. */
-    { "decoder.ipv4.frag_pkt_too_large", IPV4_FRAG_PKT_TOO_LARGE, },
-    { "decoder.ipv6.frag_pkt_too_large", IPV6_FRAG_PKT_TOO_LARGE, },
-    { "decoder.ipv4.frag_overlap", IPV4_FRAG_OVERLAP, },
-    { "decoder.ipv6.frag_overlap", IPV6_FRAG_OVERLAP, },
+    {
+            "decoder.ipv4.frag_pkt_too_large",
+            IPV4_FRAG_PKT_TOO_LARGE,
+    },
+    {
+            "decoder.ipv6.frag_pkt_too_large",
+            IPV6_FRAG_PKT_TOO_LARGE,
+    },
+    {
+            "decoder.ipv4.frag_overlap",
+            IPV4_FRAG_OVERLAP,
+    },
+    {
+            "decoder.ipv6.frag_overlap",
+            IPV6_FRAG_OVERLAP,
+    },
+    {
+            "decoder.ipv6.frag_invalid_length",
+            IPV6_FRAG_INVALID_LENGTH,
+    },
     /* Fragment ignored due to internal error */
     { "decoder.ipv4.frag_ignored", IPV4_FRAG_IGNORED, },
     { "decoder.ipv6.frag_ignored", IPV6_FRAG_IGNORED, },
diff --git a/src/decode-events.h b/src/decode-events.h
index 088453315b..329860ffce 100644
--- a/src/decode-events.h
+++ b/src/decode-events.h
@@ -162,6 +162,7 @@ enum {
     IPV6_FRAG_PKT_TOO_LARGE,
     IPV4_FRAG_OVERLAP,
     IPV6_FRAG_OVERLAP,
+    IPV6_FRAG_INVALID_LENGTH,
 
     /* Fragment ignored due to internal error */
     IPV4_FRAG_IGNORED,
diff --git a/src/decode-ipv6.c b/src/decode-ipv6.c
index 8ddce2e10a..0f1243aab8 100644
--- a/src/decode-ipv6.c
+++ b/src/decode-ipv6.c
@@ -459,6 +459,12 @@ DecodeIPV6ExtHdrs(ThreadVars *tv, DecodeThreadVars *dtv, Packet *p,
                     plen -= hdrextlen;
                     break;
                 }
+                if (p->ip6eh.fh_more_frags_set != 0 && plen % 8 != 0) {
+                    // cf https://datatracker.ietf.org/doc/html/rfc2460#section-4.5
+                    // each, except possibly the last ("rightmost") one,
+                    // being an integer multiple of 8 octets long.
+                    ENGINE_SET_EVENT(p, IPV6_FRAG_INVALID_LENGTH);
+                }
 
                 /* the rest is parsed upon reassembly */
                 p->flags |= PKT_IS_FRAGMENT;