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-rw-r--r--src/detect-tls-cert-fingerprint.c246
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diff --git a/src/detect-tls-cert-fingerprint.c b/src/detect-tls-cert-fingerprint.c
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+/* Copyright (C) 2017-2022 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 <mats.klepsland@gmail.com>
+ *
+ * Implements support for tls_cert_fingerprint 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-content.h"
+#include "detect-pcre.h"
+#include "detect-tls-cert-fingerprint.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-unittest.h"
+#include "util-unittest-helper.h"
+
+static int DetectTlsFingerprintSetup(DetectEngineCtx *, Signature *, const char *);
+#ifdef UNITTESTS
+static void DetectTlsFingerprintRegisterTests(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 void DetectTlsFingerprintSetupCallback(const DetectEngineCtx *de_ctx,
+ Signature *s);
+static bool DetectTlsFingerprintValidateCallback(const Signature *s,
+ const char **sigerror);
+static int g_tls_cert_fingerprint_buffer_id = 0;
+
+/**
+ * \brief Registration function for keyword: tls.cert_fingerprint
+ */
+void DetectTlsFingerprintRegister(void)
+{
+ sigmatch_table[DETECT_AL_TLS_CERT_FINGERPRINT].name = "tls.cert_fingerprint";
+ sigmatch_table[DETECT_AL_TLS_CERT_FINGERPRINT].alias = "tls_cert_fingerprint";
+ sigmatch_table[DETECT_AL_TLS_CERT_FINGERPRINT].desc =
+ "sticky buffer to match the TLS cert fingerprint buffer";
+ sigmatch_table[DETECT_AL_TLS_CERT_FINGERPRINT].url = "/rules/tls-keywords.html#tls-cert-fingerprint";
+ sigmatch_table[DETECT_AL_TLS_CERT_FINGERPRINT].Setup = DetectTlsFingerprintSetup;
+#ifdef UNITTESTS
+ sigmatch_table[DETECT_AL_TLS_CERT_FINGERPRINT].RegisterTests = DetectTlsFingerprintRegisterTests;
+#endif
+ sigmatch_table[DETECT_AL_TLS_CERT_FINGERPRINT].flags |= SIGMATCH_NOOPT;
+ sigmatch_table[DETECT_AL_TLS_CERT_FINGERPRINT].flags |= SIGMATCH_INFO_STICKY_BUFFER;
+
+ DetectAppLayerInspectEngineRegister2("tls.cert_fingerprint", ALPROTO_TLS,
+ SIG_FLAG_TOCLIENT, TLS_STATE_CERT_READY,
+ DetectEngineInspectBufferGeneric, GetData);
+
+ DetectAppLayerMpmRegister2("tls.cert_fingerprint", SIG_FLAG_TOCLIENT, 2,
+ PrefilterGenericMpmRegister, GetData, ALPROTO_TLS,
+ TLS_STATE_CERT_READY);
+
+ DetectAppLayerInspectEngineRegister2("tls.cert_fingerprint", ALPROTO_TLS, SIG_FLAG_TOSERVER,
+ TLS_STATE_CERT_READY, DetectEngineInspectBufferGeneric, GetData);
+
+ DetectAppLayerMpmRegister2("tls.cert_fingerprint", SIG_FLAG_TOSERVER, 2,
+ PrefilterGenericMpmRegister, GetData, ALPROTO_TLS, TLS_STATE_CERT_READY);
+
+ DetectBufferTypeSetDescriptionByName("tls.cert_fingerprint",
+ "TLS certificate fingerprint");
+
+ DetectBufferTypeRegisterSetupCallback("tls.cert_fingerprint",
+ DetectTlsFingerprintSetupCallback);
+
+ DetectBufferTypeRegisterValidateCallback("tls.cert_fingerprint",
+ DetectTlsFingerprintValidateCallback);
+
+ g_tls_cert_fingerprint_buffer_id = DetectBufferTypeGetByName("tls.cert_fingerprint");
+}
+
+/**
+ * \brief this function setup the tls_cert_fingerprint modifier keyword used in the rule
+ *
+ * \param de_ctx Pointer to the Detection Engine Context
+ * \param s Pointer to the Signature to which the current keyword belongs
+ * \param str Should hold an empty string always
+ *
+ * \retval 0 On success
+ * \retval -1 On failure
+ */
+static int DetectTlsFingerprintSetup(DetectEngineCtx *de_ctx, Signature *s,
+ const char *str)
+{
+ if (DetectBufferSetActiveList(de_ctx, s, g_tls_cert_fingerprint_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;
+ const SSLStateConnp *connp;
+
+ if (flow_flags & STREAM_TOSERVER) {
+ connp = &ssl_state->client_connp;
+ } else {
+ connp = &ssl_state->server_connp;
+ }
+
+ if (connp->cert0_fingerprint == NULL) {
+ return NULL;
+ }
+
+ const uint32_t data_len = strlen(connp->cert0_fingerprint);
+ const uint8_t *data = (uint8_t *)connp->cert0_fingerprint;
+
+ InspectionBufferSetup(det_ctx, list_id, buffer, data, data_len);
+ InspectionBufferApplyTransforms(buffer, transforms);
+ }
+
+ return buffer;
+}
+
+static bool DetectTlsFingerprintValidateCallback(const Signature *s,
+ const char **sigerror)
+{
+ for (uint32_t x = 0; x < s->init_data->buffer_index; x++) {
+ if (s->init_data->buffers[x].id != (uint32_t)g_tls_cert_fingerprint_buffer_id)
+ continue;
+ const SigMatch *sm = s->init_data->buffers[x].head;
+ for (; sm != NULL; sm = sm->next) {
+ if (sm->type != DETECT_CONTENT)
+ continue;
+
+ const DetectContentData *cd = (DetectContentData *)sm->ctx;
+
+ if (cd->content_len != 59) {
+ *sigerror = "Invalid length of the specified fingerprint. "
+ "This rule will therefore never match.";
+ SCLogWarning("rule %u: %s", s->id, *sigerror);
+ return false;
+ }
+
+ bool have_delimiters = false;
+ uint32_t u;
+ for (u = 0; u < cd->content_len; u++) {
+ if (cd->content[u] == ':') {
+ have_delimiters = true;
+ break;
+ }
+ }
+
+ if (!have_delimiters) {
+ *sigerror = "No colon delimiters ':' detected in content after "
+ "tls.cert_fingerprint. This rule will therefore "
+ "never match.";
+ SCLogWarning("rule %u: %s", s->id, *sigerror);
+ return false;
+ }
+
+ if (cd->flags & DETECT_CONTENT_NOCASE) {
+ *sigerror = "tls.cert_fingerprint should not be used together "
+ "with nocase, since the rule is automatically "
+ "lowercased anyway which makes nocase redundant.";
+ SCLogWarning("rule %u: %s", s->id, *sigerror);
+ }
+ }
+ }
+ return true;
+}
+
+static void DetectTlsFingerprintSetupCallback(const DetectEngineCtx *de_ctx,
+ Signature *s)
+{
+ for (uint32_t x = 0; x < s->init_data->buffer_index; x++) {
+ if (s->init_data->buffers[x].id != (uint32_t)g_tls_cert_fingerprint_buffer_id)
+ continue;
+ SigMatch *sm = s->init_data->buffers[x].head;
+ for (; sm != NULL; sm = sm->next) {
+ if (sm->type != DETECT_CONTENT)
+ continue;
+
+ DetectContentData *cd = (DetectContentData *)sm->ctx;
+
+ bool changed = false;
+ uint32_t u;
+ for (u = 0; u < cd->content_len; u++) {
+ if (isupper(cd->content[u])) {
+ cd->content[u] = u8_tolower(cd->content[u]);
+ changed = true;
+ }
+ }
+
+ /* recreate the context if changes were made */
+ if (changed) {
+ SpmDestroyCtx(cd->spm_ctx);
+ cd->spm_ctx =
+ SpmInitCtx(cd->content, cd->content_len, 1, de_ctx->spm_global_thread_ctx);
+ }
+ }
+ }
+}
+
+#ifdef UNITTESTS
+#include "detect-engine-alert.h"
+#include "tests/detect-tls-cert-fingerprint.c"
+#endif
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