/* 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-buffer.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 "stream-tcp.h"

#include "util-debug.h"

#include "util-unittest.h"

#include "util-unittest-helper.h"

#include "app-layer.h"

#include "app-layer-parser.h"

#include "app-layer-ssh.h"

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

#include "rust.h"

#define KEYWORD_NAME "ssh.hassh.server.string"

#define KEYWORD_ALIAS "ssh-hassh-server-string"

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

#define BUFFER_NAME "ssh.hassh.server.string"

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

static int g_ssh_hassh_server_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 (SCSshTxGetHasshString(txv, &hassh, &b_len, flow_flags) != 1)

            return NULL;

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

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

            return NULL;

        }

        InspectionBufferSetupAndApplyTransforms(det_ctx, list_id, buffer, hassh, b_len, transforms);

    }

    return buffer;

}

/**

 * \brief this function setup the ssh.hassh.server.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 DetectSshHasshServerStringSetup(DetectEngineCtx *de_ctx, Signature *s, const char *arg)

{

    if (SCDetectBufferSetActiveList(de_ctx, s, g_ssh_hassh_server_string_buffer_id) < 0)

        return -1;

    if (SCDetectSignatureSetAppProto(s, ALPROTO_SSH) < 0)

        return -1;

    /* try to enable Hassh */

    SCSshEnableHassh();

    /* Check if Hassh is disabled */

    if (!RunmodeIsUnittests() && !SCSshHasshIsEnabled()) {

        if (!SigMatchSilentErrorEnabled(de_ctx, DETECT_SSH_HASSH_SERVER_STRING)) {

            SCLogError("hassh support is not enabled");

        }

        return -2;

    }

    return 0;

}

/**

 * \brief Registration function for hasshServer.string keyword.

 */

void DetectSshHasshServerStringRegister(void) 

{

    sigmatch_table[DETECT_SSH_HASSH_SERVER_STRING].name = KEYWORD_NAME;

    sigmatch_table[DETECT_SSH_HASSH_SERVER_STRING].alias = KEYWORD_ALIAS;

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

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

    sigmatch_table[DETECT_SSH_HASSH_SERVER_STRING].Setup = DetectSshHasshServerStringSetup;

    sigmatch_table[DETECT_SSH_HASSH_SERVER_STRING].flags |=

            SIGMATCH_INFO_STICKY_BUFFER | SIGMATCH_NOOPT;

    DetectAppLayerMpmRegister(BUFFER_NAME, SIG_FLAG_TOCLIENT, 2, PrefilterGenericMpmRegister,

            GetSshData, ALPROTO_SSH, SshStateBannerDone);

    DetectAppLayerInspectEngineRegister(BUFFER_NAME, ALPROTO_SSH, SIG_FLAG_TOCLIENT,

            SshStateBannerDone, DetectEngineInspectBufferGeneric, GetSshData);

    DetectBufferTypeSetDescriptionByName(BUFFER_NAME, BUFFER_DESC);

    g_ssh_hassh_server_string_buffer_id = DetectBufferTypeGetByName(BUFFER_NAME);

}