detect/sctp: add sctp.hdr sticky buffer

Implement a sticky buffer to match the raw SCTP header
(common header + chunks)

Ticket #4251

src/Makefile.am

@@ -228,6 +228,7 @@ noinst_HEADERS = \
 	detect-id.h \
 	detect-igmphdr.h \
 	detect-igmp-type.h \
+	detect-sctphdr.h \
 	detect-ipaddr.h \
 	detect-ipopts.h \
 	detect-ipproto.h \
@@ -804,6 +805,7 @@ libsuricata_c_a_SOURCES = \
 	detect-id.c \
 	detect-igmphdr.c \
 	detect-igmp-type.c \
+	detect-sctphdr.c \
 	detect-ipaddr.c \
 	detect-ipopts.c \
 	detect-ipproto.c \

src/detect-engine-register.c

@@ -155,6 +155,7 @@
 #include "detect-icmpv4hdr.h"
 #include "detect-igmphdr.h"
 #include "detect-igmp-type.h"
+#include "detect-sctphdr.h"
 #include "detect-urilen.h"
 #include "detect-bsize.h"
 #include "detect-detection-filter.h"
@@ -676,6 +677,7 @@ void SigTableSetup(void)
     DetectIcmpv4HdrRegister();
     DetectIGMPHdrRegister();
     DetectIGMPTypeRegister();
+    DetectSCTPHdrRegister();
     DetectTlsRegister();
     DetectTlsValidityRegister();
     DetectTlsVersionRegister();

src/detect-engine-register.h

@@ -51,6 +51,7 @@ enum DetectKeywordId {
     DETECT_ICMPV4HDR,
     DETECT_IGMPHDR,
     DETECT_IGMP_TYPE,
+    DETECT_SCTPHDR,
     DETECT_DSIZE,
 
     DETECT_FLOW,

src/detect-sctphdr.c

@@ -0,0 +1,111 @@
+/* Copyright (C) 2026 Open Information Security Foundation
+ *
+ * You can copy, redistribute or modify this Program under the terms of
+ * the GNU General Public License version 2 as published by the Free
+ * Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * version 2 along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA.
+ */
+
+/**
+ * \file
+ *
+ * Implements sctp.hdr sticky buffer
+ *
+ * Author: Giuseppe Longo <glongo@oisf.net>
+ */
+
+#include "suricata-common.h"
+
+#include "detect.h"
+#include "detect-engine.h"
+#include "detect-engine-buffer.h"
+#include "detect-engine-mpm.h"
+#include "detect-sctphdr.h"
+#include "detect-engine-prefilter.h"
+
+static int DetectSCTPHdrSetup(DetectEngineCtx *, Signature *, const char *);
+
+static int g_sctphdr_buffer_id = 0;
+
+static InspectionBuffer *GetData(DetectEngineThreadCtx *det_ctx,
+        const DetectEngineTransforms *transforms, Packet *p, const int list_id);
+
+void DetectSCTPHdrRegister(void)
+{
+    sigmatch_table[DETECT_SCTPHDR].name = "sctp.hdr";
+    sigmatch_table[DETECT_SCTPHDR].desc = "sticky buffer to match on the SCTP header";
+    sigmatch_table[DETECT_SCTPHDR].url = "/rules/sctp-keywords.html#sctp-hdr";
+    sigmatch_table[DETECT_SCTPHDR].Setup = DetectSCTPHdrSetup;
+    sigmatch_table[DETECT_SCTPHDR].flags |= SIGMATCH_NOOPT | SIGMATCH_INFO_STICKY_BUFFER;
+
+    g_sctphdr_buffer_id = DetectBufferTypeRegister("sctp.hdr");
+    BUG_ON(g_sctphdr_buffer_id < 0);
+
+    DetectBufferTypeSupportsPacket("sctp.hdr");
+
+    DetectPktMpmRegister("sctp.hdr", 2, PrefilterGenericMpmPktRegister, GetData);
+
+    DetectPktInspectEngineRegister("sctp.hdr", GetData, DetectEngineInspectPktBufferGeneric);
+}
+
+/**
+ * \brief setup sctp.hdr sticky buffer
+ *
+ * \param de_ctx pointer to the Detection Engine Context
+ * \param s pointer to the current Signature
+ * \param _unused unused
+ *
+ * \retval 0 on Success
+ * \retval -1 on Failure
+ */
+static int DetectSCTPHdrSetup(DetectEngineCtx *de_ctx, Signature *s, const char *_unused)
+{
+    if (!(DetectProtoContainsProto(s->proto, IPPROTO_SCTP)))
+        return -1;
+
+    s->flags |= SIG_FLAG_REQUIRE_PACKET;
+
+    if (SCDetectBufferSetActiveList(de_ctx, s, g_sctphdr_buffer_id) < 0)
+        return -1;
+
+    return 0;
+}
+
+static InspectionBuffer *GetData(DetectEngineThreadCtx *det_ctx,
+        const DetectEngineTransforms *transforms, Packet *p, const int list_id)
+{
+    SCEnter();
+
+    if (!PacketIsSCTP(p)) {
+        SCReturnPtr(NULL, "InspectionBuffer");
+    }
+
+    InspectionBuffer *buffer = SCInspectionBufferGet(det_ctx, list_id);
+    if (buffer->inspect == NULL) {
+        const SCTPHdr *sctph = PacketGetSCTP(p);
+        const uint16_t hlen = p->l4.vars.sctp.hlen;
+        if (((uint8_t *)sctph + (ptrdiff_t)hlen) >
+                ((uint8_t *)GET_PKT_DATA(p) + (ptrdiff_t)GET_PKT_LEN(p))) {
+            SCLogDebug("data out of range: %p > %p", ((uint8_t *)sctph + (ptrdiff_t)hlen),
+                    ((uint8_t *)GET_PKT_DATA(p) + (ptrdiff_t)GET_PKT_LEN(p)));
+            SCReturnPtr(NULL, "InspectionBuffer");
+        }
+
+        const uint32_t data_len = hlen;
+        const uint8_t *data = (const uint8_t *)sctph;
+
+        SCInspectionBufferSetupAndApplyTransforms(
+                det_ctx, list_id, buffer, data, data_len, transforms);
+    }
+
+    SCReturnPtr(buffer, "InspectionBuffer");
+}

src/detect-sctphdr.h

@@ -0,0 +1,27 @@
+/* Copyright (C) 2026 Open Information Security Foundation
+ *
+ * You can copy, redistribute or modify this Program under the terms of
+ * the GNU General Public License version 2 as published by the Free
+ * Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * version 2 along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA.
+ */
+
+/**
+ * \file
+ */
+
+#ifndef SURICATA_DETECT_SCTPHDR_H
+#define SURICATA_DETECT_SCTPHDR_H
+
+void DetectSCTPHdrRegister(void);
+
+#endif /* SURICATA_DETECT_SCTPHDR_H */