suricata/src/detect-seq.c

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

/**
 * \file
 * \author Brian Rectanus <brectanu@gmail.com>
 *
 * Implements the "seq" keyword.
 */

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

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

#include "detect-seq.h"

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

static int DetectSeqSetup(DetectEngineCtx *, Signature *s, SigMatch *m,
                          char *sidstr);
static int DetectSeqMatch(ThreadVars *t, DetectEngineThreadCtx *det_ctx,
                          Packet *p, Signature *s, SigMatch *m);
static void DetectSeqRegisterTests(void);
static void DetectSeqFree(void *ptr);


void DetectSeqRegister(void) {
    sigmatch_table[DETECT_SEQ].name = "seq";
    sigmatch_table[DETECT_SEQ].Match = DetectSeqMatch;
    sigmatch_table[DETECT_SEQ].Setup = DetectSeqSetup;
    sigmatch_table[DETECT_SEQ].Free = DetectSeqFree;
    sigmatch_table[DETECT_SEQ].RegisterTests = DetectSeqRegisterTests;
}

/**
 * \internal
 * \brief This function is used to match packets with a given Seq number
 *
 * \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 DetectSeqData
 *
 * \retval 0 no match
 * \retval 1 match
 */
static int DetectSeqMatch(ThreadVars *t, DetectEngineThreadCtx *det_ctx,
                          Packet *p, Signature *s, SigMatch *m)
{
    DetectSeqData *data = (DetectSeqData *)m->ctx;

    /* This is only needed on TCP packets */
    if (IPPROTO_TCP != p->proto) {
        return 0;
    }

    return (data->seq == TCP_GET_SEQ(p)) ? 1 : 0;
}

/**
 * \internal
 * \brief this function is used to add the seq option into the 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 optstr pointer to the user provided options
 *
 * \retval 0 on Success
 * \retval -1 on Failure
 */
static int DetectSeqSetup (DetectEngineCtx *de_ctx, Signature *s,
                           SigMatch *m, char *optstr)
{
    DetectSeqData *data;
    SigMatch *sm = NULL;

    //printf("DetectSeqSetup: \'%s\'\n", optstr);

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

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

    sm->type = DETECT_SEQ;

    if (-1 == ByteExtractStringUint32(&data->seq, 10, 0, optstr)) {
        goto error;
    }
    sm->ctx = data;

    SigMatchAppend(s, m, sm);

    return 0;

error:
    if (data) free(data);
    return -1;

}

/**
 * \internal
 * \brief this function will free memory associated with seq option
 *
 * \param data pointer to seq configuration data
 */
static void DetectSeqFree(void *ptr)
{
    DetectSeqData *data = (DetectSeqData *)ptr;
    free(data);
}


#ifdef UNITTESTS

/**
 * \test DetectSeqSigTest01 tests parses
 */
static int DetectSeqSigTest01(void)
{
    int result = 0;
    DetectEngineCtx *de_ctx = DetectEngineCtxInit();
    if (de_ctx == NULL)
        goto end;

    /* These three are crammed in here as there is no Parse */
    if (SigInit(de_ctx,
                "alert tcp any any -> any any "
                "(msg:\"Testing seq\";seq:foo;sid:1;)") != NULL)
    {
        printf("invalid seq accepted: ");
        goto cleanup;
    }
    if (SigInit(de_ctx,
                "alert tcp any any -> any any "
                "(msg:\"Testing seq\";seq:9999999999;sid:1;)") != NULL)
    {
        printf("overflowing seq accepted: ");
        goto cleanup;
    }
    if (SigInit(de_ctx,
                "alert tcp any any -> any any "
                "(msg:\"Testing seq\";seq:-100;sid:1;)") != NULL)
    {
        printf("negative seq accepted: ");
        goto cleanup;
    }
    result = 1;

cleanup:
    if (de_ctx) {
        SigGroupCleanup(de_ctx);
        SigCleanSignatures(de_ctx);
        DetectEngineCtxFree(de_ctx);
    }
end:
    return result;
}

/**
 * \test DetectSeqSigTest02 tests seq keyword
 */
static int DetectSeqSigTest02(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_TCP);
    p[2] = UTHBuildPacket((uint8_t *)buf, buflen, IPPROTO_ICMP);
    if (p[0] == NULL || p[1] == NULL ||p[2] == NULL)
        goto end;

    /* TCP w/seq=42 */
    p[0]->tcph->th_seq = htonl(42);

    /* TCP w/seq=100 */
    p[1]->tcph->th_seq = htonl(100);

    char *sigs[2];
    sigs[0]= "alert tcp any any -> any any (msg:\"Testing seq\"; seq:41; sid:1;)";
    sigs[1]= "alert tcp any any -> any any (msg:\"Testing seq\"; seq:42; sid:2;)";

    uint32_t sid[2] = {1, 2};

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

    result = UTHGenericTest(p, 3, sigs, sid, (uint32_t *) results, 2);
    UTHFreePackets(p, 3);
end:
    return result;
}

#endif /* UNITTESTS */

/**
 * \internal
 * \brief This function registers unit tests for DetectSeq
 */
static void DetectSeqRegisterTests(void)
{
#ifdef UNITTESTS
    UtRegisterTest("DetectSeqSigTest01", DetectSeqSigTest01, 1);
    UtRegisterTest("DetectSeqSigTest02", DetectSeqSigTest02, 1);
#endif /* UNITTESTS */
}