suricata/src/detect-isdataat.c

/**
 * \file
 * \author Pablo Rincon <pablo.rincon.crespo@gmail.com>
 *
 * Isdataat: part of the detection engine.
 */

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

#include "util-unittest.h"
#include "util-unittest-helper.h"

#include "detect-isdataat.h"
#include "detect-content.h"

#include "flow.h"
#include "flow-var.h"

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

/**
 * \brief Regex for parsing our isdataat options
 */
#define PARSE_REGEX  "^\\s*([0-9]{1,5})\\s*(,\\s*relative)?\\s*(,\\s*rawbytes\\s*)?\\s*$"

static pcre *parse_regex;
static pcre_extra *parse_regex_study;

int DetectIsdataatMatch (ThreadVars *, DetectEngineThreadCtx *, Packet *, Signature *, SigMatch *);
int DetectIsdataatSetup (DetectEngineCtx *, Signature *, SigMatch *, char *);
void DetectIsdataatRegisterTests(void);
void DetectIsdataatFree(void *);

/**
 * \brief Registration function for isdataat: keyword
 */
void DetectIsdataatRegister (void) {
    sigmatch_table[DETECT_ISDATAAT].name = "isdataat";
    sigmatch_table[DETECT_ISDATAAT].Match = DetectIsdataatMatch;
    sigmatch_table[DETECT_ISDATAAT].Setup = DetectIsdataatSetup;
    sigmatch_table[DETECT_ISDATAAT].Free  = DetectIsdataatFree;
    sigmatch_table[DETECT_ISDATAAT].RegisterTests = DetectIsdataatRegisterTests;

    sigmatch_table[DETECT_ISDATAAT].flags |= SIGMATCH_PAYLOAD;

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

    parse_regex = pcre_compile(PARSE_REGEX, opts, &eb, &eo, NULL);
    if(parse_regex == NULL) {
        SCLogError(SC_ERR_PCRE_COMPILE, "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_ERR_PCRE_STUDY, "pcre study failed: %s", eb);
        goto error;
    }
    return;

error:
    /* XXX */
    return;
}

/**
 * \brief This function is used to match isdataat on a packet
 * \todo We need to add support for rawbytes
 *
 * \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 DetectIsdataatData
 *
 * \retval 0 no match
 * \retval 1 match
 */
int DetectIsdataatMatch (ThreadVars *t, DetectEngineThreadCtx *det_ctx, Packet *p, Signature *s, SigMatch *m)
{
    DetectIsdataatData *idad = (DetectIsdataatData *)m->ctx;

    SCLogDebug("payload_len: %u , dataat? %u ; relative? %u...", p->payload_len,idad->dataat,idad->flags &ISDATAAT_RELATIVE);

    /* Relative to the last matched content is not performed here, returning match (content should take care of this)*/
    if (idad->flags & ISDATAAT_RELATIVE)
        return 1;

    /* its not relative and we have more data in the packet than the offset of isdataat */
    if (p->payload_len >= idad->dataat) {
        SCLogDebug("matched with payload_len: %u , dataat? %u ; relative? %u...", p->payload_len,idad->dataat,idad->flags &ISDATAAT_RELATIVE);
        return 1;
    }

    return 0;
}

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

    ret = pcre_exec(parse_regex, parse_regex_study, isdataatstr, strlen(isdataatstr), 0, 0, ov, MAX_SUBSTRINGS);
    if (ret < 1 || ret > 4) {
        SCLogError(SC_ERR_PCRE_MATCH, "pcre_exec parse error, ret %" PRId32 ", string %s", ret, isdataatstr);
        goto error;
    }

    if (ret > 1) {
        const char *str_ptr;
        res = pcre_get_substring((char *)isdataatstr, ov, MAX_SUBSTRINGS, 1, &str_ptr);
        if (res < 0) {
            SCLogError(SC_ERR_PCRE_GET_SUBSTRING, "pcre_get_substring failed");
            goto error;
        }
        args[0] = (char *)str_ptr;


        if (ret > 2) {
            res = pcre_get_substring((char *)isdataatstr, ov, MAX_SUBSTRINGS, 2, &str_ptr);
            if (res < 0) {
                SCLogError(SC_ERR_PCRE_GET_SUBSTRING, "pcre_get_substring failed");
                goto error;
            }
            args[1] = (char *)str_ptr;
        }
        if (ret > 3) {
            res = pcre_get_substring((char *)isdataatstr, ov, MAX_SUBSTRINGS, 3, &str_ptr);
            if (res < 0) {
                SCLogError(SC_ERR_PCRE_GET_SUBSTRING, "pcre_get_substring failed");
                goto error;
            }
            args[2] = (char *)str_ptr;
        }

        idad = malloc(sizeof(DetectIsdataatData));
        if (idad == NULL) {
            SCLogError(SC_ERR_MEM_ALLOC, "malloc failed");
            goto error;
        }

        idad->flags = 0;
        idad->dataat = 0;

        if (args[0] != NULL) {
            if (ByteExtractStringUint16(&idad->dataat, 10,
                strlen(args[0]), args[0]) < 0 ) {
                SCLogError(SC_ERR_INVALID_VALUE, "isdataat out of range");
                free(idad);
                idad=NULL;
                goto error;
            }
        } else {
            goto error;
        }

        if (args[1] !=NULL) {
            idad->flags |= ISDATAAT_RELATIVE;

            if(args[2] !=NULL)
                idad->flags |= ISDATAAT_RAWBYTES;
        }

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

        return idad;

    }

error:

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

    if (idad != NULL) DetectIsdataatFree(idad);
    return NULL;

}

/**
 * \brief this function is used to add the parsed isdataatdata 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 isdataatstr pointer to the user provided isdataat options
 *
 * \retval 0 on Success
 * \retval -1 on Failure
 */
int DetectIsdataatSetup (DetectEngineCtx *de_ctx, Signature *s, SigMatch *m, char *isdataatstr)
{
    DetectIsdataatData *idad = NULL;
    SigMatch *sm = NULL;
    DetectContentData *cd = NULL;

    idad = DetectIsdataatParse(isdataatstr);
    if (idad == NULL) goto error;

    if(idad->flags & ISDATAAT_RELATIVE) {
        /** Set it in the last parsed contet because it is relative to that content match */
        SCLogDebug("set it in the last parsed content because it is relative to that content match");

        if( m == NULL ) {
            SCLogError(SC_ERR_INVALID_SIGNATURE, "No previous content, the flag "
                                   "'relative' cant be used without content");
            goto  error;
        } else {
            SigMatch *pm = NULL;
            /** Search for the first previous DetectContent
              * SigMatch (it can be the same as this one) */
            pm = DetectContentFindPrevApplicableSM(m);
            if (pm == NULL) {
                SCLogError(SC_ERR_INVALID_SIGNATURE, "Unknown previous keyword!");
                return -1;
            }

            cd = (DetectContentData *)pm->ctx;
            if (cd == NULL) {
                SCLogError(SC_ERR_INVALID_SIGNATURE, "Unknown previous keyword!");
                return -1;
            }

            cd->flags |= DETECT_CONTENT_ISDATAAT_RELATIVE;
            cd->isdataat = idad->dataat;

            /** Propagate the changes */
            DetectContentPropagateIsdataat(pm);
        }
    }
    else {
        SCLogDebug("set it as a normal SigMatch");

        /** else Set it as a normal SigMatch */
        sm = SigMatchAlloc();
        if (sm == NULL)
            goto error;

        sm->type = DETECT_ISDATAAT;
        sm->ctx = (void *)idad;

        SigMatchAppend(s,m,sm);
    }

    return 0;

error:
    if (idad != NULL) DetectIsdataatFree(idad);
    if (sm != NULL) free(sm);
    return -1;

}

/**
 * \brief this function will free memory associated with DetectIsdataatData
 *
 * \param idad pointer to DetectIsdataatData
 */
void DetectIsdataatFree(void *ptr) {
    DetectIsdataatData *idad = (DetectIsdataatData *)ptr;
    free(idad);
}


#ifdef UNITTESTS

/**
 * \test DetectIsdataatTestParse01 is a test to make sure that we return a correct IsdataatData structure
 *  when given valid isdataat opt
 */
int DetectIsdataatTestParse01 (void) {
    int result = 0;
    DetectIsdataatData *idad = NULL;
    idad = DetectIsdataatParse("30 ");
    if (idad != NULL) {
        DetectIsdataatFree(idad);
        result = 1;
    }

    return result;
}

/**
 * \test DetectIsdataatTestParse02 is a test to make sure that we return a correct IsdataatData structure
 *  when given valid isdataat opt
 */
int DetectIsdataatTestParse02 (void) {
    int result = 0;
    DetectIsdataatData *idad = NULL;
    idad = DetectIsdataatParse("30 , relative");
    if (idad != NULL && idad->flags & ISDATAAT_RELATIVE && !(idad->flags & ISDATAAT_RAWBYTES)) {
        DetectIsdataatFree(idad);
        result = 1;
    }

    return result;
}

/**
 * \test DetectIsdataatTestParse03 is a test to make sure that we return a correct IsdataatData structure
 *  when given valid isdataat opt
 */
int DetectIsdataatTestParse03 (void) {
    int result = 0;
    DetectIsdataatData *idad = NULL;
    idad = DetectIsdataatParse("30,relative, rawbytes ");
    if (idad != NULL && idad->flags & ISDATAAT_RELATIVE && idad->flags & ISDATAAT_RAWBYTES) {
        DetectIsdataatFree(idad);
        result = 1;
    }

    return result;
}

/**
 * \test DetectIsdataatTestPacket01 is a test to check matches of
 * isdataat, and isdataat relative
 */
int DetectIsdataatTestPacket01 (void) {
    int result = 0;
    uint8_t *buf = (uint8_t *)"Hi all!";
    uint16_t buflen = strlen((char *)buf);
    Packet *p[3];
    p[0] = UTHBuildPacket((uint8_t *)buf, buflen, IPPROTO_TCP);
    p[1] = UTHBuildPacket((uint8_t *)buf, buflen, IPPROTO_UDP);
    p[2] = UTHBuildPacket((uint8_t *)buf, buflen, IPPROTO_ICMP);

    if (p[0] == NULL || p[1] == NULL ||p[2] == NULL)
        goto end;

    char *sigs[5];
    sigs[0]= "alert ip any any -> any any (msg:\"Testing window 1\"; isdataat:6; sid:1;)";
    sigs[1]= "alert ip any any -> any any (msg:\"Testing window 2\"; content:\"all\"; isdataat:1, relative; isdataat:7; sid:2;)";
    sigs[2]= "alert ip any any -> any any (msg:\"Testing window 3\"; isdataat:8; sid:3;)";
    sigs[3]= "alert ip any any -> any any (msg:\"Testing window 4\"; content:\"Hi\"; isdataat:5, relative; sid:4;)";
    sigs[4]= "alert ip any any -> any any (msg:\"Testing window 4\"; content:\"Hi\"; isdataat:6, relative; sid:5;)";

    uint32_t sid[5] = {1, 2, 3, 4, 5};

    uint32_t results[3][5] = {
                              /* packet 0 match sid 1 but should not match sid 2 */
                              {1, 1, 0, 1, 0},
                              /* packet 1 should not match */
                              {1, 1, 0, 1, 0},
                              /* packet 2 should not match */
                              {1, 1, 0, 1, 0} };

    result = UTHGenericTest(p, 3, sigs, sid, (uint32_t *) results, 5);

    UTHFreePackets(p, 3);
end:
    return result;
}
#endif

/**
 * \brief this function registers unit tests for DetectIsdataat
 */
void DetectIsdataatRegisterTests(void) {
    #ifdef UNITTESTS
    UtRegisterTest("DetectIsdataatTestParse01", DetectIsdataatTestParse01, 1);
    UtRegisterTest("DetectIsdataatTestParse02", DetectIsdataatTestParse02, 1);
    UtRegisterTest("DetectIsdataatTestParse03", DetectIsdataatTestParse03, 1);
    UtRegisterTest("DetectIsdataatTestPacket01", DetectIsdataatTestPacket01, 1);
    #endif
}