dns: add dns.response.answer.name keyword

rust/src/dns/dns.rs

@@ -881,6 +881,24 @@ pub unsafe extern "C" fn rs_dns_tx_get_query_name(
     return 0;
 }
 
+/// Get the DNS response answer name and index i.
+#[no_mangle]
+pub unsafe extern "C" fn SCDnsTxGetAnswerName(
+    tx: &mut DNSTransaction, i: u32, buf: *mut *const u8, len: *mut u32,
+) -> bool {
+    let index = i as usize;
+    if let Some(response) = &tx.response {
+        if let Some(name) = response.answers.get(index).map(|answer| &answer.name) {
+            if !name.is_empty() {
+                *buf = name.as_ptr();
+                *len = name.len() as u32;
+                return true;
+            }
+        }
+    }
+    false
+}
+
 /// Get the DNS transaction ID of a transaction.
 //
 /// extern uint16_t rs_dns_tx_get_tx_id(RSDNSTransaction *);

src/Makefile.am

@@ -121,6 +121,7 @@ noinst_HEADERS = \
 	detect-detection-filter.h \
 	detect-distance.h \
 	detect-dnp3.h \
+	detect-dns-answer-name.h \
 	detect-dns-opcode.h \
 	detect-dns-query.h \
 	detect-dsize.h \
@@ -732,6 +733,7 @@ libsuricata_c_a_SOURCES = \
 	detect-detection-filter.c \
 	detect-distance.c \
 	detect-dnp3.c \
+	detect-dns-answer-name.c \
 	detect-dns-opcode.c \
 	detect-dns-query.c \
 	detect-dsize.c \

src/detect-dns-answer-name.c

@@ -0,0 +1,173 @@
+/* Copyright (C) 2023 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
+ *
+ * Detect keyword for DNS answer rdata: dns.response.answer.rdata
+ */
+
+#include "detect.h"
+#include "detect-parse.h"
+#include "detect-engine.h"
+#include "detect-engine-prefilter.h"
+#include "detect-engine-content-inspection.h"
+#include "detect-dns-answer-name.h"
+#include "util-profiling.h"
+#include "rust.h"
+
+static int DetectSetup(DetectEngineCtx *, Signature *, const char *);
+static uint8_t DetectEngineInspectCb(DetectEngineCtx *de_ctx, DetectEngineThreadCtx *det_ctx,
+        const struct DetectEngineAppInspectionEngine_ *engine, const Signature *s, Flow *f,
+        uint8_t flags, void *alstate, void *txv, uint64_t tx_id);
+static int PrefilterMpmRegister(DetectEngineCtx *de_ctx, SigGroupHead *sgh, MpmCtx *mpm_ctx,
+        const DetectBufferMpmRegistry *mpm_reg, int list_id);
+
+static int dns_response_answer_name_id = 0;
+
+void DetectDnsResponseAnswerNameRegister(void)
+{
+    static const char *keyword = "dns.response.answer.name";
+    sigmatch_table[DETECT_AL_DNS_RESPONSE_ANSWER_NAME].name = keyword;
+    sigmatch_table[DETECT_AL_DNS_RESPONSE_ANSWER_NAME].desc = "DNS answer name sticky buffer";
+    sigmatch_table[DETECT_AL_DNS_RESPONSE_ANSWER_NAME].url = "/rules/TODOTODOTODO";
+    sigmatch_table[DETECT_AL_DNS_RESPONSE_ANSWER_NAME].Setup = DetectSetup;
+    sigmatch_table[DETECT_AL_DNS_RESPONSE_ANSWER_NAME].flags |= SIGMATCH_NOOPT;
+    sigmatch_table[DETECT_AL_DNS_RESPONSE_ANSWER_NAME].flags |= SIGMATCH_INFO_STICKY_BUFFER;
+
+    DetectAppLayerInspectEngineRegister(
+            keyword, ALPROTO_DNS, SIG_FLAG_TOCLIENT, 0, DetectEngineInspectCb, NULL);
+    DetectAppLayerMpmRegister(
+            keyword, SIG_FLAG_TOCLIENT, 2, PrefilterMpmRegister, NULL, ALPROTO_DNS, 1);
+
+    DetectBufferTypeSetDescriptionByName(keyword, "dns response answer name");
+    DetectBufferTypeSupportsMultiInstance(keyword);
+
+    dns_response_answer_name_id = DetectBufferTypeGetByName(keyword);
+}
+
+static int DetectSetup(DetectEngineCtx *de_ctx, Signature *s, const char *str)
+{
+    if (DetectBufferSetActiveList(de_ctx, s, dns_response_answer_name_id) < 0) {
+        return -1;
+    }
+    if (DetectSignatureSetAppProto(s, ALPROTO_DNS) < 0) {
+        return -1;
+    }
+
+    return 0;
+}
+
+static InspectionBuffer *GetBuffer(DetectEngineThreadCtx *det_ctx,
+        const DetectEngineTransforms *transforms, void *txv, uint32_t index, int list_id)
+{
+    InspectionBuffer *buffer = InspectionBufferMultipleForListGet(det_ctx, list_id, index);
+    if (buffer == NULL) {
+        return NULL;
+    }
+    if (buffer->initialized) {
+        return buffer;
+    }
+
+    const uint8_t *data = NULL;
+    uint32_t data_len = 0;
+
+    if (!SCDnsTxGetAnswerName(txv, index, &data, &data_len)) {
+        InspectionBufferSetupMultiEmpty(buffer);
+        return NULL;
+    }
+    InspectionBufferSetupMulti(buffer, transforms, data, data_len);
+    return buffer;
+}
+
+static uint8_t DetectEngineInspectCb(DetectEngineCtx *de_ctx, DetectEngineThreadCtx *det_ctx,
+        const struct 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 (uint32_t i = 0;; i++) {
+        InspectionBuffer *buffer = GetBuffer(det_ctx, transforms, txv, i, engine->sm_list);
+        if (buffer == NULL || buffer->inspect == NULL) {
+            break;
+        }
+
+        det_ctx->buffer_offset = 0;
+        det_ctx->discontinue_matching = 0;
+        det_ctx->inspection_recursion_counter = 0;
+
+        const int match = DetectEngineContentInspection(de_ctx, det_ctx, s, engine->smd, NULL, f,
+                (uint8_t *)buffer->inspect, buffer->inspect_len, buffer->inspect_offset,
+                DETECT_CI_FLAGS_SINGLE, DETECT_ENGINE_CONTENT_INSPECTION_MODE_STATE);
+        if (match == 1) {
+            return DETECT_ENGINE_INSPECT_SIG_MATCH;
+        }
+    }
+
+    return DETECT_ENGINE_INSPECT_SIG_NO_MATCH;
+}
+
+typedef struct PrefilterMpm {
+    int list_id;
+    const MpmCtx *mpm_ctx;
+    const DetectEngineTransforms *transforms;
+} PrefilterMpm;
+
+static void PrefilterTx(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 PrefilterMpm *ctx = (const PrefilterMpm *)pectx;
+    const MpmCtx *mpm_ctx = ctx->mpm_ctx;
+    const int list_id = ctx->list_id;
+
+    for (uint32_t i = 0;; i++) {
+        InspectionBuffer *buffer = GetBuffer(det_ctx, ctx->transforms, txv, 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->mtcu, &det_ctx->pmq, buffer->inspect, buffer->inspect_len);
+            PREFILTER_PROFILING_ADD_BYTES(det_ctx, buffer->inspect_len);
+        }
+    }
+}
+
+static void PrefilterMpmFree(void *ptr)
+{
+    SCFree(ptr);
+}
+
+static int PrefilterMpmRegister(DetectEngineCtx *de_ctx, SigGroupHead *sgh, MpmCtx *mpm_ctx,
+        const DetectBufferMpmRegistry *mpm_reg, int list_id)
+{
+    PrefilterMpm *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, PrefilterTx, mpm_reg->app_v2.alproto,
+            mpm_reg->app_v2.tx_min_progress, pectx, PrefilterMpmFree, mpm_reg->pname);
+}

src/detect-dns-answer-name.h

@@ -0,0 +1,29 @@
+/* Copyright (C) 2023 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 FirstName LastName <yourname@domain>
+ */
+
+#ifndef __DETECT_DNS_ANSWER_RDATA_H__
+#define __DETECT_DNS_ANSWER_RDATA_H__
+
+void DetectDnsResponseAnswerNameRegister(void);
+
+#endif /* __DETECT_DNS_ANSWER_RDATA_H__ */

src/detect-engine-register.c

@@ -47,6 +47,7 @@
 #include "detect-engine-dcepayload.h"
 #include "detect-dns-opcode.h"
 #include "detect-dns-query.h"
+#include "detect-dns-answer-name.h"
 #include "detect-tls-sni.h"
 #include "detect-tls-certs.h"
 #include "detect-tls-cert-fingerprint.h"
@@ -511,6 +512,7 @@ void SigTableSetup(void)
 
     DetectDnsQueryRegister();
     DetectDnsOpcodeRegister();
+    DetectDnsResponseAnswerNameRegister();
     DetectModbusRegister();
     DetectCipServiceRegister();
     DetectEnipCommandRegister();

src/detect-engine-register.h

@@ -223,6 +223,7 @@ enum DetectKeywordId {
 
     DETECT_AL_DNS_QUERY,
     DETECT_AL_DNS_OPCODE,
+    DETECT_AL_DNS_RESPONSE_ANSWER_NAME,
     DETECT_AL_TLS_SNI,
     DETECT_AL_TLS_CERTS,
     DETECT_AL_TLS_CERT_ISSUER,