detect: add tls.alpn keyword

Ticket: #7108.

doc/userguide/rules/tls-keywords.rst

@@ -319,3 +319,16 @@ Example::
 
   alert tls any any -> any any (msg:"cert chain not value"; \
  tls.cert_chain_len:!2; classtype:misc-activity; sid:4; rev:1;)
+
+tls.alpn
+--------
+
+Matches on the ALPN buffers.
+
+Example::
+
+  alert tls any any -> any any (msg:"TLS ALPN test"; \
+    tls.alpn; content:"http/1.1"; sid:1;)
+
+``tls.alpn`` is a sticky buffer.
+

src/Makefile.am

@@ -314,6 +314,7 @@ noinst_HEADERS = \
 	detect-template.h \
 	detect-template-rust-buffer.h \
 	detect-threshold.h \
+	detect-tls-alpn.h \
 	detect-tls-cert-fingerprint.h \
 	detect-tls-cert-issuer.h \
 	detect-tls-cert-serial.h \
@@ -914,6 +915,7 @@ libsuricata_c_a_SOURCES = \
 	detect-template-rust-buffer.c \
 	detect-threshold.c \
 	detect-tls.c \
+	detect-tls-alpn.c \
 	detect-tls-cert-fingerprint.c \
 	detect-tls-cert-issuer.c \
 	detect-tls-certs.c \

src/detect-engine-register.c

@@ -59,6 +59,7 @@
 #include "detect-tls-cert-issuer.h"
 #include "detect-tls-cert-subject.h"
 #include "detect-tls-cert-serial.h"
+#include "detect-tls-alpn.h"
 #include "detect-tls-subjectaltname.h"
 #include "detect-tls-random.h"
 #include "detect-tls-ja3-hash.h"
@@ -562,6 +563,7 @@ void SigTableSetup(void)
     DetectTlsCertsRegister();
     DetectTlsCertChainLenRegister();
     DetectTlsSubjectAltNameRegister();
+    DetectTlsAlpnRegister();
     DetectTlsRandomRegister();
 
     DetectTlsJa3HashRegister();

src/detect-engine-register.h

@@ -128,6 +128,7 @@ enum DetectKeywordId {
     DETECT_AL_TLS_FINGERPRINT,
     DETECT_AL_TLS_STORE,
     DETECT_AL_TLS_CHAIN_LEN,
+    DETECT_TLS_ALPN,
 
     DETECT_AL_HTTP_COOKIE,
     DETECT_HTTP_COOKIE,

src/detect-tls-alpn.c

@@ -0,0 +1,148 @@
+/* Copyright (C) 2024 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
+ *
+ * \author Victor Julien <vjulien@oisf.net>
+ *
+ * Implements support for tls.alpn keyword.
+ */
+
+#include "suricata-common.h"
+#include "threads.h"
+#include "decode.h"
+#include "detect.h"
+
+#include "detect-parse.h"
+#include "detect-engine.h"
+#include "detect-engine-mpm.h"
+#include "detect-engine-prefilter.h"
+#include "detect-engine-content-inspection.h"
+#include "detect-content.h"
+#include "detect-tls-alpn.h"
+#include "detect-engine-uint.h"
+
+#include "flow.h"
+#include "flow-util.h"
+#include "flow-var.h"
+
+#include "util-debug.h"
+#include "util-spm.h"
+#include "util-print.h"
+
+#include "stream-tcp.h"
+
+#include "app-layer.h"
+#include "app-layer-ssl.h"
+#include "util-profiling.h"
+
+static int DetectTlsAlpnSetup(DetectEngineCtx *, Signature *, const char *);
+static InspectionBuffer *TlsAlpnGetData(DetectEngineThreadCtx *det_ctx,
+        const DetectEngineTransforms *transforms, Flow *f, uint8_t flags, void *txv, int list_id,
+        uint32_t index);
+
+static int g_tls_alpn_buffer_id = 0;
+
+/**
+ * \brief Registration function for keyword: tls.alpn
+ */
+void DetectTlsAlpnRegister(void)
+{
+    sigmatch_table[DETECT_TLS_ALPN].name = "tls.alpn";
+    sigmatch_table[DETECT_TLS_ALPN].desc = "sticky buffer to match the TLS ALPN buffer";
+    sigmatch_table[DETECT_TLS_ALPN].url = "/rules/tls-keywords.html#tls-alpn";
+    sigmatch_table[DETECT_TLS_ALPN].Setup = DetectTlsAlpnSetup;
+    sigmatch_table[DETECT_TLS_ALPN].flags |= SIGMATCH_NOOPT;
+    sigmatch_table[DETECT_TLS_ALPN].flags |= SIGMATCH_INFO_STICKY_BUFFER;
+
+    DetectAppLayerMultiRegister("tls.alpn", ALPROTO_TLS, SIG_FLAG_TOSERVER, 0, TlsAlpnGetData, 2,
+            TLS_STATE_IN_PROGRESS);
+    DetectAppLayerMultiRegister(
+            "tls.alpn", ALPROTO_TLS, SIG_FLAG_TOCLIENT, 0, TlsAlpnGetData, 2, TLS_STATE_CERT_READY);
+
+    DetectBufferTypeSetDescriptionByName("tls.alpn", "TLS APLN");
+
+    DetectBufferTypeSupportsMultiInstance("tls.alpn");
+
+    g_tls_alpn_buffer_id = DetectBufferTypeGetByName("tls.alpn");
+}
+
+/**
+ * \brief This function setup the tls.alpn sticky buffer keyword
+ *
+ * \param de_ctx Pointer to the Detect Engine Context
+ * \param s      Pointer to the Signature to which the keyword belongs
+ * \param str    Should hold an empty string always
+ *
+ * \retval  0 On success
+ * \retval -1 On failure
+ */
+static int DetectTlsAlpnSetup(DetectEngineCtx *de_ctx, Signature *s, const char *str)
+{
+    if (DetectBufferSetActiveList(de_ctx, s, g_tls_alpn_buffer_id) < 0)
+        return -1;
+
+    if (DetectSignatureSetAppProto(s, ALPROTO_TLS) < 0)
+        return -1;
+
+    return 0;
+}
+
+static InspectionBuffer *TlsAlpnGetData(DetectEngineThreadCtx *det_ctx,
+        const DetectEngineTransforms *transforms, Flow *f, uint8_t flags, void *txv, int list_id,
+        uint32_t idx)
+{
+    SCEnter();
+    InspectionBuffer *buffer = InspectionBufferMultipleForListGet(det_ctx, list_id, idx);
+    if (buffer == NULL || buffer->initialized)
+        return buffer;
+
+    const SSLState *ssl_state = (SSLState *)f->alstate;
+    const SSLStateConnp *connp;
+
+    if (flags & STREAM_TOSERVER) {
+        connp = &ssl_state->client_connp;
+    } else {
+        connp = &ssl_state->server_connp;
+    }
+
+    if (TAILQ_EMPTY(&connp->alpns)) {
+        InspectionBufferSetupMultiEmpty(buffer);
+        return NULL;
+    }
+
+    SSLAlpns *a;
+    if (idx == 0) {
+        a = TAILQ_FIRST(&connp->alpns);
+    } else {
+        // TODO optimize ?
+        a = TAILQ_FIRST(&connp->alpns);
+        for (uint32_t i = 0; i < idx; i++) {
+            a = TAILQ_NEXT(a, next);
+        }
+    }
+    if (a == NULL) {
+        InspectionBufferSetupMultiEmpty(buffer);
+        return NULL;
+    }
+
+    InspectionBufferSetupMulti(buffer, transforms, a->alpn, a->size);
+    buffer->flags = DETECT_CI_FLAGS_SINGLE;
+
+    SCReturnPtr(buffer, "InspectionBuffer");
+}

src/detect-tls-alpn.h

@@ -0,0 +1,29 @@
+/* Copyright (C) 2024 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
+ *
+ * \author Victor Julien <vjulien@oisf.net>
+ */
+
+#ifndef SURICATA_DETECT_TLS_ALPN_H
+#define SURICATA_DETECT_TLS_ALPN_H
+
+void DetectTlsAlpnRegister(void);
+
+#endif /* SURICATA_DETECT_TLS_ALPN_H */