suricata/src/detect-ipopts.c

/* Copyright (c) 2009 Open Information Security Foundation */

/** \file
 *  \author Breno Silva <breno.silva@gmail.com>
 */

#include "eidps-common.h"
#include "eidps.h"
#include "decode.h"
#include "detect.h"
#include "flow-var.h"
#include "decode-events.h"

/* Need to get the DIpOpts[] array */
#define DETECT_EVENTS

#include "detect-ipopts.h"
#include "util-unittest.h"

#define PARSE_REGEX "\\S[A-z]"

static pcre *parse_regex;
static pcre_extra *parse_regex_study;

int DetectIpOptsMatch (ThreadVars *, DetectEngineThreadCtx *, Packet *, Signature *, SigMatch *);
int DetectIpOptsSetup (DetectEngineCtx *, Signature *s, SigMatch *m, char *str);
void IpOptsRegisterTests(void);
void DetectIpOptsFree(void *);

/**
 * \brief Registration function for ipopts: keyword
 */
void DetectIpOptsRegister (void) {
    sigmatch_table[DETECT_IPOPTS].name = "ipopts";
    sigmatch_table[DETECT_IPOPTS].Match = DetectIpOptsMatch;
    sigmatch_table[DETECT_IPOPTS].Setup = DetectIpOptsSetup;
    sigmatch_table[DETECT_IPOPTS].Free  = DetectIpOptsFree;
    sigmatch_table[DETECT_IPOPTS].RegisterTests = IpOptsRegisterTests;

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

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

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

error:
    return;

}

/**
 * \internal
 * \brief This function is used to match ip option on a packet with those passed via ipopts:
 *
 * \param t pointer to thread vars
 * \param det_ctx pointer to the pattern matcher thread
 * \param p pointer to the current packet
 * \param s pointer to the Signature
 * \param m pointer to the sigmatch
 *
 * \retval 0 no match
 * \retval 1 match
 */
int DetectIpOptsMatch (ThreadVars *t, DetectEngineThreadCtx *det_ctx, Packet *p, Signature *s, SigMatch *m)
{
    int ret = 0;
    int ipopt = 0;
    DetectIpOptsData *de = (DetectIpOptsData *)m->ctx;

    if(!de || !PKT_IS_IPV4(p) || !p)
        return ret;

    /* IPV4_OPT_ANY matches on any options */

    if (p->IPV4_OPTS_CNT && (de->ipopt == IPV4_OPT_ANY)) {
        return 1;
    }

    /* Loop through instead of using o_xxx direct access fields so that
     * future options do not require any modification here.
     */

    while(ipopt < p->IPV4_OPTS_CNT) {
        if (p->IPV4_OPTS[ipopt].type == de->ipopt) {
            return 1;
        }
        ipopt++;
    }

    return ret;
}

/**
 * \internal
 * \brief This function is used to parse ipopts options passed via ipopts: keyword
 *
 * \param rawstr Pointer to the user provided ipopts options
 *
 * \retval de pointer to DetectIpOptsData on success
 * \retval NULL on failure
 */
DetectIpOptsData *DetectIpOptsParse (char *rawstr)
{
    int i;
    DetectIpOptsData *de = NULL;
#define MAX_SUBSTRINGS 30
    int ret = 0, found = 0;
    int ov[MAX_SUBSTRINGS];

    ret = pcre_exec(parse_regex, parse_regex_study, rawstr, strlen(rawstr), 0, 0, ov, MAX_SUBSTRINGS);
    if (ret < 1) {
        goto error;
    }

    for(i = 0; DIpOpts[i].ipopt_name != NULL; i++)  {
        if((strcasecmp(DIpOpts[i].ipopt_name,rawstr)) == 0) {
            found = 1;
            break;
        }
    }

    if(found == 0)
        goto error;

    de = malloc(sizeof(DetectIpOptsData));
    if (de == NULL) {
        printf("DetectIpOptsSetup malloc failed\n");
        goto error;
    }

    de->ipopt = DIpOpts[i].code;

    return de;

error:
    if (de) free(de);
    return NULL;
}

/**
 * \internal
 * \brief this function is used to add the parsed ipopts 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 rawstr pointer to the user provided ipopts options
 *
 * \retval 0 on Success
 * \retval -1 on Failure
 */
int DetectIpOptsSetup (DetectEngineCtx *de_ctx, Signature *s, SigMatch *m, char *rawstr)
{
    DetectIpOptsData *de = NULL;
    SigMatch *sm = NULL;

    de = DetectIpOptsParse(rawstr);
    if (de == NULL)
        goto error;

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

    sm->type = DETECT_IPOPTS;
    sm->ctx = (void *)de;

    SigMatchAppend(s,m,sm);
    return 0;

error:
    if (de) free(de);
    if (sm) free(sm);
    return -1;
}

/**
 * \internal
 * \brief this function will free memory associated with DetectIpOptsData
 *
 * \param de pointer to DetectIpOptsData
 */
void DetectIpOptsFree(void *de_ptr) {
    DetectIpOptsData *de = (DetectIpOptsData *)de_ptr;
    if(de) free(de);
}

/*
 * ONLY TESTS BELOW THIS COMMENT
 */

#ifdef UNITTESTS
/**
 * \test IpOptsTestParse01 is a test for a  valid ipopts value
 *
 *  \retval 1 on succces
 *  \retval 0 on failure
 */
int IpOptsTestParse01 (void) {
    DetectIpOptsData *de = NULL;
    de = DetectIpOptsParse("lsrr");
    if (de) {
        DetectIpOptsFree(de);
        return 1;
    }

    return 0;
}

/**
 * \test IpOptsTestParse02 is a test for an invalid ipopts value
 *
 *  \retval 1 on succces
 *  \retval 0 on failure
 */
int IpOptsTestParse02 (void) {
    DetectIpOptsData *de = NULL;
    de = DetectIpOptsParse("invalidopt");
    if (de) {
        DetectIpOptsFree(de);
        return 1;
    }

    return 0;
}

/**
 * \test IpOptsTestParse03 test the match function on a packet that needs to match
 *
 *  \retval 1 on succces
 *  \retval 0 on failure
 */
int IpOptsTestParse03 (void) {
    Packet p;
    ThreadVars tv;
    int ret = 0;
    DetectIpOptsData *de = NULL;
    SigMatch *sm = NULL;
    IPV4Hdr ip4h;

    memset(&tv, 0, sizeof(ThreadVars));
    memset(&p, 0, sizeof(Packet));
    memset(&ip4h, 0, sizeof(IPV4Hdr));

    p.ip4h = &ip4h;
    p.IPV4_OPTS[0].type = IPV4_OPT_RR;

    p.IPV4_OPTS_CNT++;

    de = DetectIpOptsParse("rr");

    if (de == NULL)
        goto error;

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

    sm->type = DETECT_IPOPTS;
    sm->ctx = (void *)de;

    ret = DetectIpOptsMatch(&tv,NULL,&p,NULL,sm);

    if(ret)
        return 1;

error:
    if (de) free(de);
    if (sm) free(sm);
    return 0;
}

/**
 * \test IpOptsTestParse04 test the match function on a packet that needs to not match
 *
 *  \retval 1 on succces
 *  \retval 0 on failure
 */
int IpOptsTestParse04 (void) {
    Packet p;
    ThreadVars tv;
    int ret = 0;
    DetectIpOptsData *de = NULL;
    SigMatch *sm = NULL;
    IPV4Hdr ip4h;

    memset(&tv, 0, sizeof(ThreadVars));
    memset(&p, 0, sizeof(Packet));
    memset(&ip4h, 0, sizeof(IPV4Hdr));

    p.ip4h = &ip4h;
    p.IPV4_OPTS[0].type = IPV4_OPT_RR;

    p.IPV4_OPTS_CNT++;

    de = DetectIpOptsParse("lsrr");

    if (de == NULL)
        goto error;

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

    sm->type = DETECT_IPOPTS;
    sm->ctx = (void *)de;

    ret = DetectIpOptsMatch(&tv,NULL,&p,NULL,sm);

    if(ret)
        return 1;

error:
    if (de) free(de);
    if (sm) free(sm);
    return 0;
}
#endif /* UNITTESTS */

/**
 * \brief this function registers unit tests for IpOpts
 */
void IpOptsRegisterTests(void) {
#ifdef UNITTESTS
    UtRegisterTest("IpOptsTestParse01", IpOptsTestParse01, 1);
    UtRegisterTest("IpOptsTestParse02", IpOptsTestParse02, 0);
    UtRegisterTest("IpOptsTestParse03", IpOptsTestParse03, 1);
    UtRegisterTest("IpOptsTestParse04", IpOptsTestParse04, 0);
#endif /* UNITTESTS */
}