/* Copyright (C) 2019-2022 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.certs 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-pcre.h"

#include "detect-tls-certs.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"

#include "util-unittest.h"

#include "util-unittest-helper.h"

static int DetectTlsCertsSetup(DetectEngineCtx *, Signature *, const char *);

#ifdef UNITTESTS

static void DetectTlsCertsRegisterTests(void);

#endif

static uint8_t DetectEngineInspectTlsCerts(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 PrefilterMpmTlsCertsRegister(DetectEngineCtx *de_ctx, SigGroupHead *sgh, MpmCtx *mpm_ctx,

        const DetectBufferMpmRegistry *mpm_reg, int list_id);

static int g_tls_certs_buffer_id = 0;

struct TlsCertsGetDataArgs {

    uint32_t local_id; /**< used as index into thread inspect array */

    SSLCertsChain *cert;

    const uint8_t flags;

};

typedef struct PrefilterMpmTlsCerts {

    int list_id;

    const MpmCtx *mpm_ctx;

    const DetectEngineTransforms *transforms;

} PrefilterMpmTlsCerts;

/**

 * \brief Registration function for keyword: tls.certs

 */

void DetectTlsCertsRegister(void)

{

    sigmatch_table[DETECT_AL_TLS_CERTS].name = "tls.certs";

    sigmatch_table[DETECT_AL_TLS_CERTS].desc = "sticky buffer to match the TLS certificate buffer";

    sigmatch_table[DETECT_AL_TLS_CERTS].url = "/rules/tls-keywords.html#tls-certs";

    sigmatch_table[DETECT_AL_TLS_CERTS].Setup = DetectTlsCertsSetup;

#ifdef UNITTESTS

    sigmatch_table[DETECT_AL_TLS_CERTS].RegisterTests = DetectTlsCertsRegisterTests;

#endif

    sigmatch_table[DETECT_AL_TLS_CERTS].flags |= SIGMATCH_NOOPT;

    sigmatch_table[DETECT_AL_TLS_CERTS].flags |= SIGMATCH_INFO_STICKY_BUFFER;

    DetectAppLayerInspectEngineRegister2("tls.certs", ALPROTO_TLS,

            SIG_FLAG_TOCLIENT, TLS_STATE_CERT_READY,

            DetectEngineInspectTlsCerts, NULL);

    DetectAppLayerMpmRegister2("tls.certs", SIG_FLAG_TOCLIENT, 2,

            PrefilterMpmTlsCertsRegister, NULL, ALPROTO_TLS,

            TLS_STATE_CERT_READY);

    DetectAppLayerInspectEngineRegister2("tls.certs", ALPROTO_TLS, SIG_FLAG_TOSERVER,

            TLS_STATE_CERT_READY, DetectEngineInspectTlsCerts, NULL);

    DetectAppLayerMpmRegister2("tls.certs", SIG_FLAG_TOSERVER, 2, PrefilterMpmTlsCertsRegister,

            NULL, ALPROTO_TLS, TLS_STATE_CERT_READY);

    DetectBufferTypeSetDescriptionByName("tls.certs", "TLS certificate");

    DetectBufferTypeSupportsMultiInstance("tls.certs");

    g_tls_certs_buffer_id = DetectBufferTypeGetByName("tls.certs");

}

/**

 * \brief This function setup the tls.certs 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 DetectTlsCertsSetup(DetectEngineCtx *de_ctx, Signature *s,

                               const char *str)

{

    if (DetectBufferSetActiveList(de_ctx, s, g_tls_certs_buffer_id) < 0)

        return -1;

    if (DetectSignatureSetAppProto(s, ALPROTO_TLS) < 0)

        return -1;

    return 0;

}

static InspectionBuffer *TlsCertsGetData(DetectEngineThreadCtx *det_ctx,

        const DetectEngineTransforms *transforms, Flow *f,

  struct TlsCertsGetDataArgs *cbdata, int list_id)

{

    SCEnter();

    InspectionBuffer *buffer =

            InspectionBufferMultipleForListGet(det_ctx, list_id, cbdata->local_id);

    if (buffer == NULL || buffer->initialized)

        return buffer;

    const SSLState *ssl_state = (SSLState *)f->alstate;

    const SSLStateConnp *connp;

    if (cbdata->flags & STREAM_TOSERVER) {

        connp = &ssl_state->client_connp;

    } else {

        connp = &ssl_state->server_connp;

    }

    if (TAILQ_EMPTY(&connp->certs)) {

        InspectionBufferSetupMultiEmpty(buffer);

        return NULL;

    }

    if (cbdata->cert == NULL) {

        cbdata->cert = TAILQ_FIRST(&connp->certs);

    } else {

        cbdata->cert = TAILQ_NEXT(cbdata->cert, next);

    }

    if (cbdata->cert == NULL) {

        InspectionBufferSetupMultiEmpty(buffer);

        return NULL;

    }

    InspectionBufferSetupMulti(buffer, transforms, cbdata->cert->cert_data, cbdata->cert->cert_len);

    SCReturnPtr(buffer, "InspectionBuffer");

}

static uint8_t DetectEngineInspectTlsCerts(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;

    }

    struct TlsCertsGetDataArgs cbdata = { .local_id = 0, .cert = NULL, .flags = flags };

    while (1)

    {

        InspectionBuffer *buffer = TlsCertsGetData(det_ctx, transforms, f,

                                 &cbdata, 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;

        }

        cbdata.local_id++;

    }

    return DETECT_ENGINE_INSPECT_SIG_NO_MATCH;

}

static void PrefilterTxTlsCerts(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 PrefilterMpmTlsCerts *ctx = (const PrefilterMpmTlsCerts *)pectx;

    const MpmCtx *mpm_ctx = ctx->mpm_ctx;

    const int list_id = ctx->list_id;

    struct TlsCertsGetDataArgs cbdata = { .local_id = 0, .cert = NULL, .flags = flags };

    while (1)

    {

        InspectionBuffer *buffer = TlsCertsGetData(det_ctx, ctx->transforms,

                                                   f, &cbdata, 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);

        }

        cbdata.local_id++;

    }

}

static void PrefilterMpmTlsCertsFree(void *ptr)

{

    SCFree(ptr);

}

static int PrefilterMpmTlsCertsRegister(DetectEngineCtx *de_ctx, SigGroupHead *sgh, MpmCtx *mpm_ctx,

        const DetectBufferMpmRegistry *mpm_reg, int list_id)

{

    PrefilterMpmTlsCerts *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, PrefilterTxTlsCerts,

            mpm_reg->app_v2.alproto, mpm_reg->app_v2.tx_min_progress,

            pectx, PrefilterMpmTlsCertsFree, mpm_reg->name);

}

static int g_tls_cert_buffer_id = 0;

#define BUFFER_NAME  "tls_validity"

#define KEYWORD_ID   DETECT_AL_TLS_CHAIN_LEN

#define KEYWORD_NAME "tls.cert_chain_len"

#define KEYWORD_DESC "match TLS certificate chain length"

#define KEYWORD_URL  "/rules/tls-keywords.html#tls-cert-chain-len"

/**

 * \internal

 * \brief Function to match cert chain length in TLS

 *

 * \param t       Pointer to thread vars.

 * \param det_ctx Pointer to the pattern matcher thread.

 * \param f       Pointer to the current flow.

 * \param flags   Flags.

 * \param state   App layer state.

 * \param s       Pointer to the Signature.

 * \param m       Pointer to the sigmatch that we will cast into

 *                DetectU64Data.

 *

 * \retval 0 no match.

 * \retval 1 match.

 */

static int DetectTLSCertChainLenMatch(DetectEngineThreadCtx *det_ctx, Flow *f, uint8_t flags,

        void *state, void *txv, const Signature *s, const SigMatchCtx *ctx)

{

    SCEnter();

    SSLState *ssl_state = state;

    if (flags & STREAM_TOCLIENT) {

        SSLStateConnp *connp = &ssl_state->server_connp;

        uint32_t cnt = 0;

        SSLCertsChain *cert;

        TAILQ_FOREACH (cert, &connp->certs, next) {

            cnt++;

        }

        SCLogDebug("%u certs in chain", cnt);

        const DetectU32Data *dd = (const DetectU32Data *)ctx;

        if (DetectU32Match(cnt, dd)) {

            SCReturnInt(1);

        }

    }

    SCReturnInt(0);

}

/**

 * \internal

 * \brief Function to free memory associated with DetectU64Data.

 *

 * \param de_ptr Pointer to DetectU64Data.

 */

static void DetectTLSCertChainLenFree(DetectEngineCtx *de_ctx, void *ptr)

{

    rs_detect_u32_free(ptr);

}

/**

 * \brief Function to add the parsed tls cert chain len field into the current signature.

 *

 * \param de_ctx Pointer to the Detection Engine Context.

 * \param s      Pointer to the Current Signature.

 * \param rawstr Pointer to the user provided flags options.

 * \param type   Defines if this is notBefore or notAfter.

 *

 * \retval 0 on Success.

 * \retval -1 on Failure.

 */

static int DetectTLSCertChainLenSetup(DetectEngineCtx *de_ctx, Signature *s, const char *rawstr)

{

    if (DetectSignatureSetAppProto(s, ALPROTO_TLS) != 0)

        return -1;

    DetectU32Data *dd = DetectU32Parse(rawstr);

    if (dd == NULL) {

        SCLogError("Parsing \'%s\' failed for %s", rawstr, sigmatch_table[KEYWORD_ID].name);

        return -1;

    }

    SigMatch *sm = SigMatchAlloc();

    if (sm == NULL) {

        rs_detect_u32_free(dd);

        return -1;

    }

    sm->type = KEYWORD_ID;

    sm->ctx = (void *)dd;

    SigMatchAppendSMToList(s, sm, g_tls_cert_buffer_id);

    return 0;

}

void DetectTlsCertChainLenRegister(void)

{

    sigmatch_table[KEYWORD_ID].name = KEYWORD_NAME;

    sigmatch_table[KEYWORD_ID].desc = KEYWORD_DESC;

    sigmatch_table[KEYWORD_ID].url = KEYWORD_URL;

    sigmatch_table[KEYWORD_ID].AppLayerTxMatch = DetectTLSCertChainLenMatch;

    sigmatch_table[KEYWORD_ID].Setup = DetectTLSCertChainLenSetup;

    sigmatch_table[KEYWORD_ID].Free = DetectTLSCertChainLenFree;

    DetectAppLayerInspectEngineRegister2(BUFFER_NAME, ALPROTO_TLS, SIG_FLAG_TOCLIENT,

            TLS_STATE_CERT_READY, DetectEngineInspectGenericList, NULL);

    g_tls_cert_buffer_id = DetectBufferTypeGetByName(BUFFER_NAME);

}

#ifdef UNITTESTS

#include "tests/detect-tls-certs.c"

#endif