suricata/src/detect-icode.c

/**
 * Copyright (c) 2009 Open Information Security Foundation
 *
 * \file detect-icode.c
 * \author Gerardo Iglesias <iglesiasg@gmail.com>
 *
 * "icode" keyword support
 */

#include "suricata-common.h"
#include "debug.h"
#include "decode.h"
#include "detect.h"

#include "detect-icode.h"

#include "util-byte.h"
#include "util-unittest.h"
#include "util-debug.h"

/**
 *\brief Regex for parsing our icode options
 */
#define PARSE_REGEX "^\\s*(<|>)?\\s*([0-9]+)\\s*(?:<>\\s*([0-9]+))?\\s*$"

static pcre *parse_regex;
static pcre_extra *parse_regex_study;

int DetectICodeMatch(ThreadVars *, DetectEngineThreadCtx *, Packet *, Signature *, SigMatch *);
int DetectICodeSetup(DetectEngineCtx *, Signature *, SigMatch *, char *);
void DetectICodeRegisterTests(void);
void DetectICodeFree(void *);


/**
 * \brief Registration function for icode: keyword
 */
void DetectICodeRegister (void) {
    sigmatch_table[DETECT_ICODE].name = "icode";
    sigmatch_table[DETECT_ICODE].Match = DetectICodeMatch;
    sigmatch_table[DETECT_ICODE].Setup = DetectICodeSetup;
    sigmatch_table[DETECT_ICODE].Free = DetectICodeFree;
    sigmatch_table[DETECT_ICODE].RegisterTests = DetectICodeRegisterTests;

    const char *eb;
    int eo;
    int opts = 0;

    parse_regex = pcre_compile(PARSE_REGEX, opts, &eb, &eo, NULL);
    if(parse_regex == NULL)
    {
        SCLogError(SC_PCRE_COMPILE_FAILED, "pcre compile of \"%s\" failed at offset %" PRId32 ": %s", PARSE_REGEX, eo, eb);
        goto error;
    }

    parse_regex_study = pcre_study(parse_regex, 0, &eb);
    if(eb != NULL)
    {
        SCLogError(SC_PCRE_COMPILE_FAILED, "pcre study failed: %s", eb);
        goto error;
    }
    return;

error:
    return;
}

/**
 * \brief This function is used to match icode rule option set on a packet with those passed via icode:
 *
 * \param t pointer to thread vars
 * \param det_ctx pointer to the pattern matcher thread
 * \param p pointer to the current packet
 * \param m pointer to the sigmatch that we will cast into DetectICodeData
 *
 * \retval 0 no match
 * \retval 1 match
 */
int DetectICodeMatch (ThreadVars *t, DetectEngineThreadCtx *det_ctx, Packet *p, Signature *s, SigMatch *m) {
    int ret = 0;
    uint8_t picode;
    DetectICodeData *icd = (DetectICodeData *)m->ctx;

    if (PKT_IS_ICMPV4(p)) {
        picode = ICMPV4_GET_CODE(p);
    } else if (PKT_IS_ICMPV6(p)) {
        picode = ICMPV6_GET_CODE(p);
    } else {
        /* Packet not ICMPv4 nor ICMPv6 */
        return ret;
    }

    switch(icd->mode) {
        case DETECT_ICODE_EQ:
            ret = (picode == icd->code1) ? 1 : 0;
            break;
        case DETECT_ICODE_LT:
            ret = (picode < icd->code1) ? 1 : 0;
            break;
        case DETECT_ICODE_GT:
            ret = (picode > icd->code1) ? 1 : 0;
            break;
        case DETECT_ICODE_RN:
            ret = (picode >= icd->code1 && picode <= icd->code2) ? 1 : 0;
            break;
    }

    return ret;
}

/**
 * \brief This function is used to parse icode options passed via icode: keyword
 *
 * \param icodestr Pointer to the user provided icode options
 *
 * \retval icd pointer to DetectICodeData on success
 * \retval NULL on failure
 */
DetectICodeData *DetectICodeParse(char *icodestr) {
    DetectICodeData *icd = NULL;
    char *args[3] = {NULL, NULL, NULL};
#define MAX_SUBSTRINGS 30
    int ret = 0, res = 0;
    int ov[MAX_SUBSTRINGS];

    ret = pcre_exec(parse_regex, parse_regex_study, icodestr, strlen(icodestr), 0, 0, ov, MAX_SUBSTRINGS);
    if (ret < 1 || ret > 4) {
        SCLogError(SC_PCRE_MATCH_FAILED, "DetectICodeParse: parse error");
        goto error;
    }

    int i;
    const char *str_ptr;
    for (i = 1; i < ret; i++) {
        res = pcre_get_substring((char *)icodestr, ov, MAX_SUBSTRINGS, i, &str_ptr);
        if (res < 0) {
            SCLogError(SC_PCRE_GET_SUBSTRING_FAILED, "DetectICodeParse: pcre_get_substring failed");
            goto error;
        }
        args[i-1] = (char *)str_ptr;
    }

    icd = malloc(sizeof(DetectICodeData));
    if (icd == NULL) {
        SCLogError(SC_ERR_MEM_ALLOC, "Error allocating memory");
        goto error;
    }
    icd->code1 = 0;
    icd->code2 = 0;
    icd->mode = 0;

    /* we have either "<" or ">" */
    if (strlen(args[0]) != 0) {
        /* we have a third part ("<> y"), therefore it's invalid */
        if (args[2] != NULL) {
            SCLogInfo("icode: invalid value");
            goto error;
        }
        /* we have only a comparison ("<", ">") */
        ByteExtractStringUint8(&icd->code1, 10, 0, args[1]);
        if ((strcmp(args[0], ">")) == 0) icd->mode = DETECT_ICODE_GT;
        else icd->mode = DETECT_ICODE_LT;
    } else { /* no "<", ">" */
        /* we have a range ("<>") */
        if (args[2] != NULL) {
            icd->mode = (uint8_t) DETECT_ICODE_RN;
            ByteExtractStringUint8(&icd->code1, 10, 0, args[1]);
            ByteExtractStringUint8(&icd->code2, 10, 0, args[2]);
            /* we check that the first given value in the range is less than
               the second, otherwise we swap them */
            if (icd->code1 > icd->code2) {
                uint8_t temp = icd->code1;
                icd->code1 = icd->code2;
                icd->code2 = temp;
            }
        } else { /* we have an equality */
            icd->mode = DETECT_ICODE_EQ;
            ByteExtractStringUint8(&icd->code1, 10, 0, args[1]);
        }
    }

    for (i = 0; i < (ret-1); i++) {
        if (args[i] != NULL) free(args[i]);
    }
    return icd;

error:
    for (i = 0; i < (ret-1); i++) {
        if (args[i] != NULL) free(args[i]);
    }
    if (icd != NULL) DetectICodeFree(icd);
    return NULL;
}

/**
 * \brief this function is used to add the parsed icode data into the current signature
 *
 * \param de_ctx pointer to the Detection Engine Context
 * \param s pointer to the Current Signature
 * \param m pointer to the Current SigMatch
 * \param icodestr pointer to the user provided icode options
 *
 * \retval 0 on Success
 * \retval -1 on Failure
 */
int DetectICodeSetup(DetectEngineCtx *de_ctx, Signature *s, SigMatch *m, char *icodestr) {

    DetectICodeData *icd = NULL;
    SigMatch *sm = NULL;

    icd = DetectICodeParse(icodestr);
    if (icd == NULL) goto error;

    sm = SigMatchAlloc();
    if (sm == NULL) goto error;

    sm->type = DETECT_ICODE;
    sm->ctx = (void *)icd;

    SigMatchAppend(s, m, sm);

    return 0;

error:
    if (icd != NULL) DetectICodeFree(icd);
    if (sm != NULL) free(sm);
    return -1;
}

/**
 * \brief this function will free memory associated with DetectICodeData
 *
 * \param ptr pointer to DetectICodeData
 */
void DetectICodeFree(void *ptr) {
    DetectICodeData *icd = (DetectICodeData *)ptr;
    free(icd);
}

#ifdef UNITTESTS

#include "detect-parse.h"
#include "detect-engine.h"
#include "detect-engine-mpm.h"

/**
 * \test DetectICodeParseTest01 is a test for setting a valid icode value
 */
int DetectICodeParseTest01(void) {
    DetectICodeData *icd = NULL;
    int result = 0;
    icd = DetectICodeParse("8");
    if (icd != NULL) {
        if (icd->code1 == 8 && icd->mode == DETECT_ICODE_EQ)
            result = 1;
        DetectICodeFree(icd);
    }
    return result;
}

/**
 * \test DetectICodeParseTest02 is a test for setting a valid icode value
 *       with ">" operator
 */
int DetectICodeParseTest02(void) {
    DetectICodeData *icd = NULL;
    int result = 0;
    icd = DetectICodeParse(">8");
    if (icd != NULL) {
        if (icd->code1 == 8 && icd->mode == DETECT_ICODE_GT)
            result = 1;
        DetectICodeFree(icd);
    }
    return result;
}

/**
 * \test DetectICodeParseTest03 is a test for setting a valid icode value
 *       with "<" operator
 */
int DetectICodeParseTest03(void) {
    DetectICodeData *icd = NULL;
    int result = 0;
    icd = DetectICodeParse("<8");
    if (icd != NULL) {
        if (icd->code1 == 8 && icd->mode == DETECT_ICODE_LT)
            result = 1;
        DetectICodeFree(icd);
    }
    return result;
}

/**
 * \test DetectICodeParseTest04 is a test for setting a valid icode value
 *       with "<>" operator
 */
int DetectICodeParseTest04(void) {
    DetectICodeData *icd = NULL;
    int result = 0;
    icd = DetectICodeParse("8<>20");
    if (icd != NULL) {
        if (icd->code1 == 8 && icd->code2 == 20 && icd->mode == DETECT_ICODE_RN)
            result = 1;
        DetectICodeFree(icd);
    }
    return result;
}

/**
 * \test DetectICodeParseTest05 is a test for setting a valid icode value
 *       with spaces all around
 */
int DetectICodeParseTest05(void) {
    DetectICodeData *icd = NULL;
    int result = 0;
    icd = DetectICodeParse("  8 ");
    if (icd != NULL) {
        if (icd->code1 == 8 && icd->mode == DETECT_ICODE_EQ)
            result = 1;
        DetectICodeFree(icd);
    }
    return result;
}

/**
 * \test DetectICodeParseTest06 is a test for setting a valid icode value
 *       with ">" operator and spaces all around
 */
int DetectICodeParseTest06(void) {
    DetectICodeData *icd = NULL;
    int result = 0;
    icd = DetectICodeParse("  >  8 ");
    if (icd != NULL) {
        if (icd->code1 == 8 && icd->mode == DETECT_ICODE_GT)
            result = 1;
        DetectICodeFree(icd);
    }
    return result;
}

/**
 * \test DetectICodeParseTest07 is a test for setting a valid icode value
 *       with "<>" operator and spaces all around
 */
int DetectICodeParseTest07(void) {
    DetectICodeData *icd = NULL;
    int result = 0;
    icd = DetectICodeParse("  8  <>  20 ");
    if (icd != NULL) {
        if (icd->code1 == 8 && icd->code2 == 20 && icd->mode == DETECT_ICODE_RN)
            result = 1;
        DetectICodeFree(icd);
    }
    return result;
}

/**
 * \test DetectICodeParseTest08 is a test for setting an invalid icode value
 */
int DetectICodeParseTest08(void) {
    DetectICodeData *icd = NULL;
    icd = DetectICodeParse("> 8 <> 20");
    if (icd == NULL)
        return 1;
    DetectICodeFree(icd);
    return 0;
}

/**
 * \test DetectICodeMatchTest01 is a test for checking the working of icode
 *       keyword by creating 5 rules and matching a crafted packet against
 *       them. 4 out of 5 rules shall trigger.
 */
int DetectICodeMatchTest01(void) {

    Packet p;
    Signature *s = NULL;
    ThreadVars th_v;
    DetectEngineThreadCtx *det_ctx;
    int result = 0;
    IPV4Hdr ip4h;
    ICMPV4Hdr icmpv4h;

    memset(&th_v, 0, sizeof(th_v));
    memset(&p, 0, sizeof(p));
    memset(&ip4h, 0, sizeof(ip4h));
    memset(&icmpv4h, 0, sizeof(icmpv4h));

    p.src.family = AF_INET;
    p.dst.family = AF_INET;
    p.proto = IPPROTO_ICMP;
    p.ip4h = &ip4h;
    icmpv4h.code = 10;
    p.icmpv4h = &icmpv4h;

    DetectEngineCtx *de_ctx = DetectEngineCtxInit();
    if (de_ctx == NULL) {
        goto end;
    }

    de_ctx->flags |= DE_QUIET;

    s = de_ctx->sig_list = SigInit(de_ctx,"alert icmp any any -> any any (icode:10; sid:1;)");
    if (s == NULL) {
        goto end;
    }

    s = s->next = SigInit(de_ctx,"alert icmp any any -> any any (icode:<15; sid:2;)");
    if (s == NULL) {
        goto end;
    }

    s = s->next = SigInit(de_ctx,"alert icmp any any -> any any (icode:>20; sid:3;)");
    if (s == NULL) {
        goto end;
    }

    s = s->next = SigInit(de_ctx,"alert icmp any any -> any any (icode:8<>20; sid:4;)");
    if (s == NULL) {
        goto end;
    }

    s = s->next = SigInit(de_ctx,"alert icmp any any -> any any (icode:20<>8; sid:5;)");
    if (s == NULL) {
        goto end;
    }

    SigGroupBuild(de_ctx);
    DetectEngineThreadCtxInit(&th_v, (void *)de_ctx, (void *)&det_ctx);

    SigMatchSignatures(&th_v, de_ctx, det_ctx, &p);
    if (PacketAlertCheck(&p, 1) == 0) {
        SCLogDebug("sid 1 did not alert, but should have");
        goto cleanup;
    } else if (PacketAlertCheck(&p, 2) == 0) {
        SCLogDebug("sid 2 did not alert, but should have");
        goto cleanup;
    } else if (PacketAlertCheck(&p, 3)) {
        SCLogDebug("sid 3 alerted, but should not have");
        goto cleanup;
    } else if (PacketAlertCheck(&p, 4) == 0) {
        SCLogDebug("sid 4 did not alert, but should have");
        goto cleanup;
    } else if (PacketAlertCheck(&p, 5) == 0) {
        SCLogDebug("sid 5 did not alert, but should have");
        goto cleanup;
    }

    result = 1;

cleanup:
    SigGroupCleanup(de_ctx);
    SigCleanSignatures(de_ctx);

    DetectEngineThreadCtxDeinit(&th_v, (void *)det_ctx);
    DetectEngineCtxFree(de_ctx);

end:
    return result;
}

#endif /* UNITTESTS */

/**
 * \brief this function registers unit tests for DetectICode
 */
void DetectICodeRegisterTests(void) {
#ifdef UNITTESTS
    UtRegisterTest("DetectICodeParseTest01", DetectICodeParseTest01, 1);
    UtRegisterTest("DetectICodeParseTest02", DetectICodeParseTest02, 1);
    UtRegisterTest("DetectICodeParseTest03", DetectICodeParseTest03, 1);
    UtRegisterTest("DetectICodeParseTest04", DetectICodeParseTest04, 1);
    UtRegisterTest("DetectICodeParseTest05", DetectICodeParseTest05, 1);
    UtRegisterTest("DetectICodeParseTest06", DetectICodeParseTest06, 1);
    UtRegisterTest("DetectICodeParseTest07", DetectICodeParseTest07, 1);
    UtRegisterTest("DetectICodeParseTest08", DetectICodeParseTest08, 1);
    UtRegisterTest("DetectICodeMatchTest01", DetectICodeMatchTest01, 1);
#endif /* UNITTESTS */
}