suricata/src/detect-rfb-sectype.c

/* Copyright (C) 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.
 */

/**
 *
 * \author Sascha Steinbiss <sascha.steinbiss@dcso.de>
 */

#include "suricata-common.h"
#include "conf.h"
#include "detect.h"
#include "detect-parse.h"
#include "detect-engine.h"
#include "detect-engine-content-inspection.h"
#include "detect-rfb-sectype.h"
#include "app-layer-parser.h"
#include "util-byte.h"

#include "rust-bindings.h"

/**
 *   [rfb.sectype]:[<|>|<=|>=]<type>;
 */
#define PARSE_REGEX "^\\s*(<=|>=|<|>)?\\s*([0-9]+)\\s*$"
static DetectParseRegex parse_regex;

enum DetectRfbSectypeCompareMode {
    PROCEDURE_EQ = 1, /* equal */
    PROCEDURE_LT, /* less than */
    PROCEDURE_LE, /* less than or equal */
    PROCEDURE_GT, /* greater than */
    PROCEDURE_GE, /* greater than or equal */
};

typedef struct {
    uint32_t version;
    enum DetectRfbSectypeCompareMode mode;
} DetectRfbSectypeData;

static DetectRfbSectypeData *DetectRfbSectypeParse (const char *);
static int DetectRfbSectypeSetup (DetectEngineCtx *, Signature *s, const char *str);
static void DetectRfbSectypeFree(DetectEngineCtx *, void *);
static int g_rfb_sectype_buffer_id = 0;

static int DetectEngineInspectRfbSectypeGeneric(DetectEngineCtx *de_ctx,
        DetectEngineThreadCtx *det_ctx, const struct DetectEngineAppInspectionEngine_ *engine,
        const Signature *s, Flow *f, uint8_t flags, void *alstate, void *txv, uint64_t tx_id);

static int DetectRfbSectypeMatch (DetectEngineThreadCtx *, Flow *,
                                   uint8_t, void *, void *, const Signature *,
                                   const SigMatchCtx *);

/**
 * \brief Registration function for rfb.sectype keyword.
 */
void DetectRfbSectypeRegister (void)
{
    sigmatch_table[DETECT_AL_RFB_SECTYPE].name = "rfb.sectype";
    sigmatch_table[DETECT_AL_RFB_SECTYPE].desc = "match RFB security type";
    sigmatch_table[DETECT_AL_RFB_SECTYPE].url = "/rules/rfb-keywords.html#rfb-sectype";
    sigmatch_table[DETECT_AL_RFB_SECTYPE].AppLayerTxMatch = DetectRfbSectypeMatch;
    sigmatch_table[DETECT_AL_RFB_SECTYPE].Setup = DetectRfbSectypeSetup;
    sigmatch_table[DETECT_AL_RFB_SECTYPE].Free = DetectRfbSectypeFree;

    DetectSetupParseRegexes(PARSE_REGEX, &parse_regex);

    DetectAppLayerInspectEngineRegister2("rfb.sectype", ALPROTO_RFB, SIG_FLAG_TOSERVER, 1,
            DetectEngineInspectRfbSectypeGeneric, NULL);

    g_rfb_sectype_buffer_id = DetectBufferTypeGetByName("rfb.sectype");
}

static int DetectEngineInspectRfbSectypeGeneric(DetectEngineCtx *de_ctx,
        DetectEngineThreadCtx *det_ctx, const struct DetectEngineAppInspectionEngine_ *engine,
        const Signature *s, Flow *f, uint8_t flags, void *alstate, void *txv, uint64_t tx_id)
{
    return DetectEngineInspectGenericList(
            de_ctx, det_ctx, s, engine->smd, f, flags, alstate, txv, tx_id);
}

static inline int SectypeMatch(const uint32_t version,
        enum DetectRfbSectypeCompareMode mode, uint32_t ref_version)
{
    switch (mode) {
        case PROCEDURE_EQ:
            if (version == ref_version)
                SCReturnInt(1);
            break;
        case PROCEDURE_LT:
            if (version < ref_version)
                SCReturnInt(1);
            break;
        case PROCEDURE_LE:
            if (version <= ref_version)
                SCReturnInt(1);
            break;
        case PROCEDURE_GT:
            if (version > ref_version)
                SCReturnInt(1);
            break;
        case PROCEDURE_GE:
            if (version >= ref_version)
                SCReturnInt(1);
            break;
    }
    SCReturnInt(0);
}

/**
 * \internal
 * \brief Function to match security type of a RFB TX
 *
 * \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 txv     Pointer to the RFBTransaction.
 * \param s       Pointer to the Signature.
 * \param ctx     Pointer to the sigmatch that we will cast into DetectRfbSectypeData.
 *
 * \retval 0 no match.
 * \retval 1 match.
 */
static int DetectRfbSectypeMatch (DetectEngineThreadCtx *det_ctx,
                                   Flow *f, uint8_t flags, void *state,
                                   void *txv, const Signature *s,
                                   const SigMatchCtx *ctx)
{
    SCEnter();

    const DetectRfbSectypeData *dd = (const DetectRfbSectypeData *)ctx;
    uint32_t version;
    rs_rfb_tx_get_sectype(txv, &version);
    if (SectypeMatch(version, dd->mode, dd->version))
        SCReturnInt(1);
    SCReturnInt(0);
}

/**
 * \internal
 * \brief Function to parse options passed via rfb.sectype keywords.
 *
 * \param rawstr Pointer to the user provided options.
 *
 * \retval dd pointer to DetectRfbSectypeData on success.
 * \retval NULL on failure.
 */
static DetectRfbSectypeData *DetectRfbSectypeParse (const char *rawstr)
{
    DetectRfbSectypeData *dd = NULL;
#define MAX_SUBSTRINGS 30
    int ret = 0, res = 0;
    int ov[MAX_SUBSTRINGS];
    char mode[2] = "";
    char value1[20] = "";

    ret = DetectParsePcreExec(&parse_regex, rawstr, 0, 0, ov, MAX_SUBSTRINGS);
    if (ret < 3 || ret > 5) {
        SCLogError(SC_ERR_PCRE_MATCH, "Parse error %s", rawstr);
        goto error;
    }

    res = pcre_copy_substring((char *)rawstr, ov, MAX_SUBSTRINGS, 1, mode,
                              sizeof(mode));
    if (res < 0) {
        SCLogError(SC_ERR_PCRE_GET_SUBSTRING, "pcre_copy_substring failed");
        goto error;
    }

    res = pcre_copy_substring((char *)rawstr, ov, MAX_SUBSTRINGS, 2, value1,
                              sizeof(value1));
    if (res < 0) {
        SCLogError(SC_ERR_PCRE_GET_SUBSTRING, "pcre_copy_substring failed");
        goto error;
    }

    dd = SCCalloc(1, sizeof(DetectRfbSectypeData));
    if (unlikely(dd == NULL))
        goto error;

    if (strlen(mode) == 0) {
        dd->mode = PROCEDURE_EQ;
    } else if (strlen(mode) == 1) {
        if (mode[0] == '<')
            dd->mode = PROCEDURE_LT;
        else if (mode[0] == '>')
            dd->mode = PROCEDURE_GT;
    } else if (strlen(mode) == 2) {
        if (strcmp(mode, "<=") == 0)
            dd->mode = PROCEDURE_LE;
        if (strcmp(mode, ">=") == 0)
            dd->mode = PROCEDURE_GE;
    } else {
        SCLogError(SC_ERR_INVALID_SIGNATURE, "invalid mode for rfb.sectype keyword");
        goto error;
    }

    if (dd->mode == 0) {
        dd->mode = PROCEDURE_EQ;
    }

    /* set the first value */
    if (ByteExtractStringUint32(&dd->version, 10, strlen(value1), value1) <= 0) {
        SCLogError(SC_ERR_INVALID_SIGNATURE, "invalid character as arg "
                   "to rfb.sectype keyword");
        goto error;
    }

    return dd;

error:
    if (dd)
        SCFree(dd);
    return NULL;
}

/**
 * \brief Function to add the parsed RFB security type 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.
 *
 * \retval 0 on Success.
 * \retval -1 on Failure.
 */
static int DetectRfbSectypeSetup (DetectEngineCtx *de_ctx, Signature *s, const char *rawstr)
{
    if (DetectSignatureSetAppProto(s, ALPROTO_RFB) != 0)
        return -1;

    DetectRfbSectypeData *dd = DetectRfbSectypeParse(rawstr);
    if (dd == NULL) {
        SCLogError(SC_ERR_INVALID_ARGUMENT,"Parsing \'%s\' failed", rawstr);
        goto error;
    }

    /* okay so far so good, lets get this into a SigMatch
     * and put it in the Signature. */
    SigMatch *sm = SigMatchAlloc();
    if (sm == NULL)
        goto error;

    sm->type = DETECT_AL_RFB_SECTYPE;
    sm->ctx = (void *)dd;

    SigMatchAppendSMToList(s, sm, g_rfb_sectype_buffer_id);
    return 0;

error:
    DetectRfbSectypeFree(de_ctx, dd);
    return -1;
}

/**
 * \internal
 * \brief Function to free memory associated with DetectRfbSectypeData.
 *
 * \param de_ptr Pointer to DetectRfbSectypeData.
 */
static void DetectRfbSectypeFree(DetectEngineCtx *de_ctx, void *ptr)
{
    SCFree(ptr);
}