/* Copyright (C) 2017 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 ja3.hash 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-ja3-hash.h"

#include "flow.h"

#include "flow-util.h"

#include "flow-var.h"

#include "conf.h"

#include "conf-yaml-loader.h"

#include "util-debug.h"

#include "util-spm.h"

#include "util-print.h"

#include "util-ja3.h"

#include "stream-tcp.h"

#include "app-layer.h"

#include "app-layer-ssl.h"

#include "util-unittest.h"

#include "util-unittest-helper.h"

#ifndef HAVE_JA3

static int DetectJA3SetupNoSupport(DetectEngineCtx *a, Signature *b, const char *c)

{

    SCLogError("no JA3 support built in");

    return -1;

}

#endif

static int DetectTlsJa3HashSetup(DetectEngineCtx *, Signature *, const char *);

static InspectionBuffer *GetData(DetectEngineThreadCtx *det_ctx,

       const DetectEngineTransforms *transforms,

       Flow *f, const uint8_t flow_flags,

       void *txv, const int list_id);

static void DetectTlsJa3HashSetupCallback(const DetectEngineCtx *de_ctx,

       Signature *s);

static bool DetectTlsJa3HashValidateCallback(const Signature *s,

       const char **sigerror);

static int g_tls_ja3_hash_buffer_id = 0;

/**

 * \brief Registration function for keyword: ja3_hash

 */

void DetectTlsJa3HashRegister(void)

{

    sigmatch_table[DETECT_AL_TLS_JA3_HASH].name = "ja3.hash";

    sigmatch_table[DETECT_AL_TLS_JA3_HASH].alias = "ja3_hash";

    sigmatch_table[DETECT_AL_TLS_JA3_HASH].desc = "sticky buffer to match the JA3 hash buffer";

    sigmatch_table[DETECT_AL_TLS_JA3_HASH].url = "/rules/ja3-keywords.html#ja3-hash";

#ifdef HAVE_JA3

    sigmatch_table[DETECT_AL_TLS_JA3_HASH].Setup = DetectTlsJa3HashSetup;

#else  /* HAVE_JA3 */

    sigmatch_table[DETECT_AL_TLS_JA3_HASH].Setup = DetectJA3SetupNoSupport;

#endif /* HAVE_JA3 */

    sigmatch_table[DETECT_AL_TLS_JA3_HASH].flags |= SIGMATCH_NOOPT;

    sigmatch_table[DETECT_AL_TLS_JA3_HASH].flags |= SIGMATCH_INFO_STICKY_BUFFER;

#ifdef HAVE_JA3

    DetectAppLayerInspectEngineRegister2("ja3.hash", ALPROTO_TLS, SIG_FLAG_TOSERVER, 0,

            DetectEngineInspectBufferGeneric, GetData);

    DetectAppLayerMpmRegister2("ja3.hash", SIG_FLAG_TOSERVER, 2,

            PrefilterGenericMpmRegister, GetData, ALPROTO_TLS, 0);

    DetectAppLayerMpmRegister2("ja3.hash", SIG_FLAG_TOSERVER, 2, PrefilterGenericMpmRegister,

            Ja3DetectGetHash, ALPROTO_QUIC, 1);

    DetectAppLayerInspectEngineRegister2("ja3.hash", ALPROTO_QUIC, SIG_FLAG_TOSERVER, 1,

            DetectEngineInspectBufferGeneric, Ja3DetectGetHash);

    DetectBufferTypeSetDescriptionByName("ja3.hash", "TLS JA3 hash");

    DetectBufferTypeRegisterSetupCallback("ja3.hash",

            DetectTlsJa3HashSetupCallback);

    DetectBufferTypeRegisterValidateCallback("ja3.hash",

            DetectTlsJa3HashValidateCallback);

    g_tls_ja3_hash_buffer_id = DetectBufferTypeGetByName("ja3.hash");

#endif /* HAVE_JA3 */

}

/**

 * \brief this function setup the ja3.hash 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

 * \retval -2 on failure that should be silent after the first

 */

static int DetectTlsJa3HashSetup(DetectEngineCtx *de_ctx, Signature *s, const char *str)

{

    if (DetectBufferSetActiveList(de_ctx, s, g_tls_ja3_hash_buffer_id) < 0)

        return -1;

    if (s->alproto != ALPROTO_UNKNOWN && s->alproto != ALPROTO_TLS && s->alproto != ALPROTO_QUIC) {

        SCLogError("rule contains conflicting protocols.");

        return -1;

    }

    /* try to enable JA3 */

    SSLEnableJA3();

    /* Check if JA3 is disabled */

    if (!RunmodeIsUnittests() && Ja3IsDisabled("rule")) {

        if (!SigMatchSilentErrorEnabled(de_ctx, DETECT_AL_TLS_JA3_HASH)) {

            SCLogError("ja3 support is not enabled");

        }

        return -2;

    }

    s->init_data->init_flags |= SIG_FLAG_INIT_JA;

    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 (ssl_state->client_connp.ja3_hash == NULL) {

            return NULL;

        }

        const uint32_t data_len = strlen(ssl_state->client_connp.ja3_hash);

        const uint8_t *data = (uint8_t *)ssl_state->client_connp.ja3_hash;

        InspectionBufferSetup(det_ctx, list_id, buffer, data, data_len);

        InspectionBufferApplyTransforms(buffer, transforms);

    }

    return buffer;

}

static bool DetectTlsJa3HashValidateCallback(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_ja3_hash_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->flags & DETECT_CONTENT_NOCASE) {

                *sigerror = "ja3.hash 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);

            }

            if (cd->content_len == SC_MD5_HEX_LEN)

                return true;

            *sigerror = "Invalid length of the specified JA3 hash (should "

                        "be 32 characters long). This rule will therefore "

                        "never match.";

            SCLogWarning("rule %u: %s", s->id, *sigerror);

            return false;

        }

    }

    return true;

}

static void DetectTlsJa3HashSetupCallback(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_ja3_hash_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);

            }

        }

    }

}