Add keyword to match on 'raw' TLS certificates

doc/userguide/rules/tls-keywords.rst

@@ -136,6 +136,21 @@ Usage::
 
   tls_cert_valid;
 
+tls.cert
+--------
+
+Do a "raw" match on the TLS certificate. This keyword only matches on the
+first certificate in the certificate chain.
+
+Example::
+
+  alert tls any any -> any any (msg:"match bytes in TLS cert"; tls.cert; \
+    content:"|06 09 2a 86|"; sid:200070;)
+
+``tls.cert`` is a 'sticky buffer'.
+
+``tls.cert`` can be used as ``fast_pattern``.
+
 tls.version
 -----------
 

src/Makefile.am

@@ -112,6 +112,7 @@ detect-tls-cert-issuer.c detect-tls-cert-issuer.h \
 detect-tls-cert-subject.c detect-tls-cert-subject.h \
 detect-tls-cert-serial.c detect-tls-cert-serial.h \
 detect-tls-cert-fingerprint.c detect-tls-cert-fingerprint.h \
+detect-tls-cert.c detect-tls-cert.h \
 detect-dsize.c detect-dsize.h \
 detect-engine.c detect-engine.h \
 detect-engine-address.c detect-engine-address.h \

src/detect-engine-register.c

@@ -47,6 +47,7 @@
 #include "detect-engine-dcepayload.h"
 #include "detect-dns-query.h"
 #include "detect-tls-sni.h"
+#include "detect-tls-cert.h"
 #include "detect-tls-cert-fingerprint.h"
 #include "detect-tls-cert-issuer.h"
 #include "detect-tls-cert-subject.h"
@@ -432,6 +433,7 @@ void SigTableSetup(void)
     DetectTlsSubjectRegister();
     DetectTlsSerialRegister();
     DetectTlsFingerprintRegister();
+    DetectTlsCertRegister();
 
     DetectTlsJa3HashRegister();
     DetectTlsJa3StringRegister();

src/detect-engine-register.h

@@ -194,6 +194,7 @@ enum {
 
     DETECT_AL_DNS_QUERY,
     DETECT_AL_TLS_SNI,
+    DETECT_AL_TLS_CERT,
     DETECT_AL_TLS_CERT_ISSUER,
     DETECT_AL_TLS_CERT_SUBJECT,
     DETECT_AL_TLS_CERT_SERIAL,

src/detect-tls-cert.c

@@ -0,0 +1,142 @@
+/* Copyright (C) 2019 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 Mats Klepsland <[email protected]>
+ *
+ * Implements support for tls.cert keyword.
+ */
+
+#include "suricata-common.h"
+#include "threads.h"
+#include "debug.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-content.h"
+#include "detect-pcre.h"
+#include "detect-tls-cert.h"
+
+#include "flow.h"
+#include "flow-util.h"
+#include "flow-var.h"
+
+#include "util-debug.h"
+#include "util-unittest.h"
+#include "util-spm.h"
+#include "util-print.h"
+
+#include "stream-tcp.h"
+
+#include "app-layer.h"
+#include "app-layer-ssl.h"
+
+#include "util-unittest.h"
+#include "util-unittest-helper.h"
+
+static int DetectTlsCertSetup(DetectEngineCtx *, Signature *, const char *);
+#ifdef UNITTESTS
+static void DetectTlsCertRegisterTests(void);
+#endif
+static InspectionBuffer *GetData(DetectEngineThreadCtx *det_ctx,
+        const DetectEngineTransforms *transforms,
+        Flow *_f, const uint8_t _flow_flags,
+        void *txv, const int list_id);
+static int g_tls_cert_buffer_id = 0;
+
+/**
+ * \brief Registration function for keyword: tls.cert
+ */
+void DetectTlsCertRegister(void)
+{
+    sigmatch_table[DETECT_AL_TLS_CERT].name = "tls.cert";
+    sigmatch_table[DETECT_AL_TLS_CERT].desc = "content modifier to match the TLS certificate buffer";
+    sigmatch_table[DETECT_AL_TLS_CERT].url = DOC_URL DOC_VERSION "/rules/tls-keywords.html#tls.cert";
+    sigmatch_table[DETECT_AL_TLS_CERT].Setup = DetectTlsCertSetup;
+#ifdef UNITTESTS
+    sigmatch_table[DETECT_AL_TLS_CERT].RegisterTests = DetectTlsCertRegisterTests;
+#endif
+    sigmatch_table[DETECT_AL_TLS_CERT].flags |= SIGMATCH_NOOPT;
+
+    DetectAppLayerInspectEngineRegister2("tls.cert", ALPROTO_TLS,
+            SIG_FLAG_TOCLIENT, TLS_STATE_CERT_READY,
+            DetectEngineInspectBufferGeneric, GetData);
+
+    DetectAppLayerMpmRegister2("tls.cert", SIG_FLAG_TOCLIENT, 2,
+            PrefilterGenericMpmRegister, GetData, ALPROTO_TLS,
+            TLS_STATE_CERT_READY);
+
+    DetectBufferTypeSetDescriptionByName("tls.cert", "TLS certificate");
+
+    g_tls_cert_buffer_id = DetectBufferTypeGetByName("tls.cert");
+}
+
+/**
+ * \brief This function setup the tls.cert modifier 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 DetectTlsCertSetup(DetectEngineCtx *de_ctx, Signature *s,
+                              const char *str)
+{
+    if (DetectBufferSetActiveList(s, g_tls_cert_buffer_id) < 0)
+        return -1;
+
+    if (DetectSignatureSetAppProto(s, ALPROTO_TLS) < 0)
+        return -1;
+
+    return 0;
+}
+
+static InspectionBuffer *GetData(DetectEngineThreadCtx *det_ctx,
+        const DetectEngineTransforms *transforms, Flow *f,
+        const uint8_t flow_flags, void *txv, const int list_id)
+{
+    InspectionBuffer *buffer = InspectionBufferGet(det_ctx, list_id);
+    if (buffer->inspect == NULL) {
+        const SSLState *ssl_state = (SSLState *)f->alstate;
+
+        if (TAILQ_EMPTY(&ssl_state->server_connp.certs)) {
+            return NULL;
+        }
+
+        const SSLCertsChain *cert = TAILQ_FIRST(&ssl_state->server_connp.certs);
+        if (cert == NULL) {
+            return NULL;
+        }
+
+        InspectionBufferSetup(buffer, cert->cert_data, cert->cert_len);
+        InspectionBufferApplyTransforms(buffer, transforms);
+    }
+
+    return buffer;
+}
+
+#ifdef UNITTESTS
+#include "tests/detect-tls-cert.c"
+#endif

src/detect-tls-cert.h

@@ -0,0 +1,29 @@
+/* Copyright (C) 2019 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 Mats Klepsland <[email protected]>
+ */
+
+#ifndef __DETECT_TLS_CERT_H__
+#define __DETECT_TLS_CERT_H__
+
+void DetectTlsCertRegister(void);
+
+#endif /* __DETECT_TLS_CERT_H__ */