/* Copyright (C) 2007-2020 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 Vadym Malakhatko <v.malakhatko@sirinsoftware.com>

 */

#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-state.h"

#include "detect-engine-prefilter.h"

#include "flow.h"

#include "flow-var.h"

#include "flow-util.h"

#include "util-debug.h"

#include "util-unittest.h"

#include "util-unittest-helper.h"

#include "stream-tcp.h"

#include "app-layer.h"

#include "app-layer-parser.h"

#include "app-layer-ssh.h"

#include "detect-ssh-hassh-string.h"

#include "rust.h"

#define KEYWORD_NAME "ssh.hassh.string"

#define KEYWORD_ALIAS "ssh-hassh-string"

#define KEYWORD_DOC "ssh-keywords.html#hassh.string"

#define BUFFER_NAME "ssh.hassh.string"

#define BUFFER_DESC "Ssh Client Key Exchange methods For ssh Clients "

static int g_ssh_hassh_string_buffer_id = 0;

static InspectionBuffer *GetSshData(DetectEngineThreadCtx *det_ctx,

        const DetectEngineTransforms *transforms, Flow *_f,

        const uint8_t flow_flags, void *txv, const int list_id)

{

    SCEnter();

    InspectionBuffer *buffer = InspectionBufferGet(det_ctx, list_id);

    if (buffer->inspect == NULL) {

        const uint8_t *hassh = NULL;

        uint32_t b_len = 0;

        if (rs_ssh_tx_get_hassh_string(txv, &hassh, &b_len, flow_flags) != 1)

            return NULL;

        if (hassh == NULL || b_len == 0) {

            SCLogDebug("SSH hassh string is not set");

            return NULL;

        }

        InspectionBufferSetup(det_ctx, list_id, buffer, hassh, b_len);

        InspectionBufferApplyTransforms(buffer, transforms);

    }

    return buffer;

}

/**

 * \brief this function setup the hassh.string 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 DetectSshHasshStringSetup(DetectEngineCtx *de_ctx, Signature *s, const char *arg)

{

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

        return -1;

    if (DetectSignatureSetAppProto(s, ALPROTO_SSH) < 0)

        return -1;

    /* try to enable Hassh */

    rs_ssh_enable_hassh();

    /* Check if Hassh is disabled */

    if (!RunmodeIsUnittests() && !rs_ssh_hassh_is_enabled()) {

        if (!SigMatchSilentErrorEnabled(de_ctx, DETECT_AL_SSH_HASSH_STRING)) {

            SCLogError("hassh support is not enabled");

        }

        return -2;

    }

    return 0;

}

/**

 * \brief Registration function for hassh.string keyword.

 */

void DetectSshHasshStringRegister(void) 

{

    sigmatch_table[DETECT_AL_SSH_HASSH_STRING].name = KEYWORD_NAME;

    sigmatch_table[DETECT_AL_SSH_HASSH_STRING].alias = KEYWORD_ALIAS;

    sigmatch_table[DETECT_AL_SSH_HASSH_STRING].desc = BUFFER_NAME " sticky buffer";

    sigmatch_table[DETECT_AL_SSH_HASSH_STRING].url = "/rules/" KEYWORD_DOC;

    sigmatch_table[DETECT_AL_SSH_HASSH_STRING].Setup = DetectSshHasshStringSetup;

    sigmatch_table[DETECT_AL_SSH_HASSH_STRING].flags |= SIGMATCH_INFO_STICKY_BUFFER | SIGMATCH_NOOPT;

    DetectAppLayerMpmRegister2(BUFFER_NAME, SIG_FLAG_TOSERVER, 2, 

            PrefilterGenericMpmRegister, GetSshData, 

            ALPROTO_SSH, SshStateBannerDone);

    DetectAppLayerInspectEngineRegister2(BUFFER_NAME, ALPROTO_SSH, 

            SIG_FLAG_TOSERVER, SshStateBannerDone, 

            DetectEngineInspectBufferGeneric, GetSshData);

    DetectBufferTypeSetDescriptionByName(BUFFER_NAME, BUFFER_DESC);

    g_ssh_hassh_string_buffer_id = DetectBufferTypeGetByName(BUFFER_NAME);

}