detect/tls-subjectaltname: add sticky buffer

Add TLS SubjectAltName sticky buffer. It is implemented as multi-buffer.

Feature 5234

src/Makefile.am

@@ -330,6 +330,7 @@ noinst_HEADERS = \
 	detect-tls-certs.h \
 	detect-tls-cert-subject.h \
 	detect-tls-cert-validity.h \
+	detect-tls-subjectaltname.h \
 	detect-tls.h \
 	detect-tls-ja3-hash.h \
 	detect-tls-ja3s-hash.h \
@@ -941,6 +942,7 @@ libsuricata_c_a_SOURCES = \
 	detect-tls-cert-serial.c \
 	detect-tls-cert-subject.c \
 	detect-tls-cert-validity.c \
+	detect-tls-subjectaltname.c \
 	detect-tls-ja3-hash.c \
 	detect-tls-ja3s-hash.c \
 	detect-tls-ja3s-string.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-subjectaltname.h"
 #include "detect-tls-random.h"
 #include "detect-tls-ja3-hash.h"
 #include "detect-tls-ja3-string.h"
@@ -551,6 +552,7 @@ void SigTableSetup(void)
     DetectTlsFingerprintRegister();
     DetectTlsCertsRegister();
     DetectTlsCertChainLenRegister();
+    DetectTlsSubjectAltNameRegister();
     DetectTlsRandomRegister();
 
     DetectTlsJa3HashRegister();

src/detect-engine-register.h

@@ -240,6 +240,7 @@ enum DetectKeywordId {
     DETECT_AL_TLS_CERT_SUBJECT,
     DETECT_AL_TLS_CERT_SERIAL,
     DETECT_AL_TLS_CERT_FINGERPRINT,
+    DETECT_AL_TLS_SUBJECTALTNAME,
     DETECT_AL_TLS_RANDOM_TIME,
     DETECT_AL_TLS_RANDOM_BYTES,
     DETECT_AL_TLS_RANDOM,

src/detect-tls-subjectaltname.c

@@ -0,0 +1,208 @@
+/* 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 Shivani Bhardwaj <shivani@oisf.net>
+ *
+ * Implements support for tls.subjectaltname 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-subjectaltname.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 DetectTlsSubjectAltNameSetup(DetectEngineCtx *, Signature *, const char *);
+static uint8_t DetectEngineInspectTlsSubjectAltName(DetectEngineCtx *de_ctx,
+        DetectEngineThreadCtx *det_ctx, const DetectEngineAppInspectionEngine *engine,
+        const Signature *s, Flow *f, uint8_t flags, void *alstate, void *txv, uint64_t tx_id);
+static int PrefilterMpmTlsSubjectAltNameRegister(DetectEngineCtx *de_ctx, SigGroupHead *sgh,
+        MpmCtx *mpm_ctx, const DetectBufferMpmRegistry *mpm_reg, int list_id);
+
+static int g_tls_subjectaltname_buffer_id = 0;
+
+typedef struct PrefilterMpmTlsSubjectAltName {
+    int list_id;
+    const MpmCtx *mpm_ctx;
+    const DetectEngineTransforms *transforms;
+} PrefilterMpmTlsSubjectAltName;
+
+/**
+ * \brief Registration function for keyword: tls.subjectaltname
+ */
+void DetectTlsSubjectAltNameRegister(void)
+{
+    sigmatch_table[DETECT_AL_TLS_SUBJECTALTNAME].name = "tls.subjectaltname";
+    sigmatch_table[DETECT_AL_TLS_SUBJECTALTNAME].desc =
+            "sticky buffer to match the TLS Subject Alternative Name buffer";
+    sigmatch_table[DETECT_AL_TLS_SUBJECTALTNAME].url =
+            "/rules/tls-keywords.html#tls-subjectaltname";
+    sigmatch_table[DETECT_AL_TLS_SUBJECTALTNAME].Setup = DetectTlsSubjectAltNameSetup;
+    sigmatch_table[DETECT_AL_TLS_SUBJECTALTNAME].flags |= SIGMATCH_NOOPT;
+    sigmatch_table[DETECT_AL_TLS_SUBJECTALTNAME].flags |= SIGMATCH_INFO_STICKY_BUFFER;
+
+    DetectAppLayerInspectEngineRegister("tls.subjectaltname", ALPROTO_TLS, SIG_FLAG_TOCLIENT,
+            TLS_STATE_CERT_READY, DetectEngineInspectTlsSubjectAltName, NULL);
+
+    DetectAppLayerMpmRegister("tls.subjectaltname", SIG_FLAG_TOCLIENT, 2,
+            PrefilterMpmTlsSubjectAltNameRegister, NULL, ALPROTO_TLS, TLS_STATE_CERT_READY);
+
+    DetectBufferTypeSetDescriptionByName("tls.subjectaltname", "TLS Subject Alternative Name");
+
+    DetectBufferTypeSupportsMultiInstance("tls.subjectaltname");
+
+    g_tls_subjectaltname_buffer_id = DetectBufferTypeGetByName("tls.subjectaltname");
+}
+
+/**
+ * \brief This function setup the tls.subjectaltname 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 DetectTlsSubjectAltNameSetup(DetectEngineCtx *de_ctx, Signature *s, const char *str)
+{
+    if (DetectBufferSetActiveList(de_ctx, s, g_tls_subjectaltname_buffer_id) < 0)
+        return -1;
+
+    if (DetectSignatureSetAppProto(s, ALPROTO_TLS) < 0)
+        return -1;
+
+    return 0;
+}
+
+static InspectionBuffer *TlsSubjectAltNameGetData(DetectEngineThreadCtx *det_ctx,
+        const DetectEngineTransforms *transforms, Flow *f, uint8_t flags, uint16_t idx, int list_id)
+{
+    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;
+
+    connp = &ssl_state->server_connp;
+
+    if (idx >= connp->cert0_sans_len) {
+        return NULL;
+    }
+
+    InspectionBufferSetupMulti(buffer, transforms, (const uint8_t *)connp->cert0_sans[idx],
+            strlen(connp->cert0_sans[idx]));
+
+    SCReturnPtr(buffer, "InspectionBuffer");
+}
+
+static uint8_t DetectEngineInspectTlsSubjectAltName(DetectEngineCtx *de_ctx,
+        DetectEngineThreadCtx *det_ctx, const DetectEngineAppInspectionEngine *engine,
+        const Signature *s, Flow *f, uint8_t flags, void *alstate, void *txv, uint64_t tx_id)
+{
+    const DetectEngineTransforms *transforms = NULL;
+    if (!engine->mpm) {
+        transforms = engine->v2.transforms;
+    }
+
+    for (uint16_t i = 0;; i++) {
+        InspectionBuffer *buffer =
+                TlsSubjectAltNameGetData(det_ctx, transforms, f, flags, i, engine->sm_list);
+        if (buffer == NULL || buffer->inspect == NULL)
+            break;
+        const bool match = DetectEngineContentInspection(de_ctx, det_ctx, s, engine->smd, NULL, f,
+                buffer->inspect, buffer->inspect_len, buffer->inspect_offset,
+                DETECT_CI_FLAGS_SINGLE, DETECT_ENGINE_CONTENT_INSPECTION_MODE_STATE);
+        if (match) {
+            return DETECT_ENGINE_INSPECT_SIG_MATCH;
+        }
+    }
+
+    return DETECT_ENGINE_INSPECT_SIG_NO_MATCH;
+}
+
+static void PrefilterTxTlsSubjectAltName(DetectEngineThreadCtx *det_ctx, const void *pectx,
+        Packet *p, Flow *f, void *txv, const uint64_t idx, const AppLayerTxData *_txd,
+        const uint8_t flags)
+{
+    SCEnter();
+
+    const PrefilterMpmTlsSubjectAltName *ctx = (const PrefilterMpmTlsSubjectAltName *)pectx;
+    const MpmCtx *mpm_ctx = ctx->mpm_ctx;
+    const int list_id = ctx->list_id;
+
+    for (uint16_t i = 0;; i++) {
+        InspectionBuffer *buffer =
+                TlsSubjectAltNameGetData(det_ctx, ctx->transforms, f, flags, i, list_id);
+        if (buffer == NULL)
+            break;
+
+        if (buffer->inspect_len >= mpm_ctx->minlen) {
+            (void)mpm_table[mpm_ctx->mpm_type].Search(
+                    mpm_ctx, &det_ctx->mtc, &det_ctx->pmq, buffer->inspect, buffer->inspect_len);
+            PREFILTER_PROFILING_ADD_BYTES(det_ctx, buffer->inspect_len);
+        }
+    }
+}
+
+static void PrefilterMpmTlsSubjectAltNameFree(void *ptr)
+{
+    SCFree(ptr);
+}
+
+static int PrefilterMpmTlsSubjectAltNameRegister(DetectEngineCtx *de_ctx, SigGroupHead *sgh,
+        MpmCtx *mpm_ctx, const DetectBufferMpmRegistry *mpm_reg, int list_id)
+{
+    PrefilterMpmTlsSubjectAltName *pectx = SCCalloc(1, sizeof(*pectx));
+    if (pectx == NULL)
+        return -1;
+
+    pectx->list_id = list_id;
+    pectx->mpm_ctx = mpm_ctx;
+    pectx->transforms = &mpm_reg->transforms;
+
+    return PrefilterAppendTxEngine(de_ctx, sgh, PrefilterTxTlsSubjectAltName,
+            mpm_reg->app_v2.alproto, mpm_reg->app_v2.tx_min_progress, pectx,
+            PrefilterMpmTlsSubjectAltNameFree, mpm_reg->name);
+}

src/detect-tls-subjectaltname.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 Shivani Bhardwaj <shivani@oisf.net>
+ */
+
+#ifndef SURICATA_DETECT_TLS_SUBJECTALTNAME_H
+#define SURICATA_DETECT_TLS_SUBJECTALTNAME_H
+
+void DetectTlsSubjectAltNameRegister(void);
+
+#endif /* SURICATA_DETECT_TLS_SUBJECTALTNAME_H */