suricata/src/detect-metadata.c

/* Copyright (C) 2007-2017 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.
 */

/**
 * \file
 *
 * \author Victor Julien <victor@inliniac.net>
 *
 * Implements metadata keyword support
 *
 * \todo Do we need to do anything more this is used in snort host attribute table
 *       It is also used for rule managment.
 */

#include "suricata-common.h"
#include "detect.h"
#include "detect-parse.h"
#include "detect-engine.h"
#include "detect-metadata.h"

#include "util-unittest.h"

#define PARSE_REGEX "^\\s*([^\\s]+)\\s+([^\\s]+)(?:,\\s*([^\\s]+)\\s+([^\\s]+))*$"
#define PARSE_TAG_REGEX "\\s*([^\\s]+)\\s+([^,]+)\\s*"

static pcre *parse_regex;
static pcre_extra *parse_regex_study;
static pcre *parse_tag_regex;
static pcre_extra *parse_tag_regex_study;

static int DetectMetadataSetup (DetectEngineCtx *, Signature *, const char *);
static void DetectMetadataRegisterTests(void);

void DetectMetadataRegister (void)
{
    sigmatch_table[DETECT_METADATA].name = "metadata";
    sigmatch_table[DETECT_METADATA].desc = "used by suricata for logging";
    sigmatch_table[DETECT_METADATA].url = DOC_URL DOC_VERSION "/rules/meta.html#metadata";
    sigmatch_table[DETECT_METADATA].Match = NULL;
    sigmatch_table[DETECT_METADATA].Setup = DetectMetadataSetup;
    sigmatch_table[DETECT_METADATA].Free  = NULL;
    sigmatch_table[DETECT_METADATA].RegisterTests = DetectMetadataRegisterTests;

    DetectSetupParseRegexes(PARSE_REGEX, &parse_regex, &parse_regex_study);
    DetectSetupParseRegexes(PARSE_TAG_REGEX, &parse_tag_regex, &parse_tag_regex_study);
}

/**
 *  \brief Free a Metadata object
 */
void DetectMetadataFree(DetectMetadata *mdata)
{
    SCEnter();

    SCFree(mdata);

    SCReturn;
}

/* djb2 string hashing */
static uint32_t StringHashFunc(HashTable *ht, void *data, uint16_t datalen)
{
    uint32_t hash = 5381;
    int c;

    while ((c = *(char *)data++))
        hash = ((hash << 5) + hash) + c; /* hash * 33 + c */

    hash = hash % ht->array_size;

    return hash;
}

static char StringHashCompareFunc(void *data1, uint16_t datalen1,
                               void *data2, uint16_t datalen2)
{
    int len1 = strlen((char *)data1);
    int len2 = strlen((char *)data2);

    if (len1 == len2 && memcmp(data1, data2, len1) == 0) {
        return 1;
    }

    return 0;
}

static void StringHashFreeFunc(void *data)
{
    SCFree(data);
}

int DetectMetadataHashInit(DetectEngineCtx *de_ctx)
{
    if (! DetectEngineMustParseMetadata())
        return 0;

    de_ctx->metadata_table = HashTableInit(4096, StringHashFunc, StringHashCompareFunc, StringHashFreeFunc);
    if (de_ctx->metadata_table == NULL)
        return -1;
    return 0;
}

void DetectMetadataHashFree(DetectEngineCtx *de_ctx)
{
    if (de_ctx->metadata_table)
        HashTableFree(de_ctx->metadata_table);
}

static const char *DetectMedatataHashAdd(DetectEngineCtx *de_ctx, const char *string)
{
    const char * hstring = (char *)HashTableLookup(de_ctx->metadata_table, (void *)string, strlen(string));
    if (hstring) {
        return hstring;
    }

    const char *astring = SCStrdup(string);
    if (astring == NULL) {
        return NULL;
    }

    if (HashTableAdd(de_ctx->metadata_table, (void *)astring, strlen(astring)) == 0) {
        return (char *)HashTableLookup(de_ctx->metadata_table, (void *)astring, strlen(astring));
    } else {
        SCFree((void *)astring);
    }
    return NULL;
}

static int DetectMetadataParse(DetectEngineCtx *de_ctx, Signature *s, const char *metadatastr)
{
#define MAX_SUBSTRINGS 30
    int ret = 0, res = 0;
    int ov[MAX_SUBSTRINGS];

    ret = pcre_exec(parse_regex, parse_regex_study, metadatastr,
                    strlen(metadatastr), 0, 0, ov, MAX_SUBSTRINGS);
    if (ret < 2) {
        /* Only warn user that the metadata are not parsed due
         * to invalid format */
        SCLogInfo("signature metadata not in key value format, ret %" PRId32
                    ", string %s", ret, metadatastr);
        return 0;
    }

    size_t metadatalen = strlen(metadatastr)+1;
    char rawstr[metadatalen];
    strlcpy(rawstr, metadatastr, metadatalen);
    const char *key = NULL;
    const char *value = NULL;
    char pkey[256];
    char pvalue[256];

    char *saveptr = NULL;
    char *kv = strtok_r(rawstr, ",", &saveptr);
    if (kv == NULL) {
        goto error;
    }

    /* now check key value */
    do {
        DetectMetadata *dkv;

        ret = pcre_exec(parse_tag_regex, parse_tag_regex_study, kv, strlen(kv), 0, 0, ov, MAX_SUBSTRINGS);
        if (ret < 2) {
            SCLogError(SC_ERR_PCRE_MATCH, "pcre_exec parse error, ret %" PRId32
                    ", string %s", ret, rawstr);
            goto error;
        }

        res =  pcre_copy_substring(kv, ov, MAX_SUBSTRINGS, 1, pkey, sizeof(pkey));
        if (res < 0) {
            SCLogError(SC_ERR_PCRE_GET_SUBSTRING, "pcre_copy_substring failed");
            goto error;
        }
        key = DetectMedatataHashAdd(de_ctx, pkey);
        if (key == NULL) {
            SCLogError(SC_ERR_MEM_ALLOC, "can't create metadata key");
            goto error;
        }

        res =  pcre_copy_substring(kv, ov, MAX_SUBSTRINGS, 2, pvalue, sizeof(pvalue));
        if (res < 0) {
            SCLogError(SC_ERR_PCRE_GET_SUBSTRING, "pcre_copy_substring failed");
            goto error;
        }
        value = DetectMedatataHashAdd(de_ctx, pvalue);
        if (value == NULL) {
            SCLogError(SC_ERR_MEM_ALLOC, "can't create metadata value");
            goto error;
        }

        SCLogDebug("key: %s, value: %s", key, value);

        dkv = SCMalloc(sizeof(DetectMetadata));
        if (dkv == NULL) {
            goto error;
        }
        dkv->key = key;
        dkv->value = value;
        dkv->next = s->metadata;
        s->metadata = dkv;

        kv = strtok_r(NULL, ",", &saveptr);
    } while (kv);

    return 0;

error:
    return -1;
}

static int DetectMetadataSetup(DetectEngineCtx *de_ctx, Signature *s, const char *rawstr)
{
    if (DetectEngineMustParseMetadata()) {
        DetectMetadataParse(de_ctx, s, rawstr);
    }

    return 0;
}

#ifdef UNITTESTS

static int DetectMetadataParseTest01(void)
{
    DetectEngineUnsetParseMetadata();
    DetectEngineCtx *de_ctx = DetectEngineCtxInit();
    FAIL_IF_NULL(de_ctx);

    Signature *sig = DetectEngineAppendSig(de_ctx,
                                           "alert tcp any any -> any any "
                                           "(metadata: toto 1; sid:1; rev:1;)");
    FAIL_IF_NULL(sig);
    FAIL_IF(sig->metadata); 

    DetectEngineCtxFree(de_ctx);
    PASS;
}

static int DetectMetadataParseTest02(void)
{
    DetectEngineSetParseMetadata();
    DetectEngineCtx *de_ctx = NULL;
    DetectMetadata *dm;

    de_ctx = DetectEngineCtxInit();
    FAIL_IF_NULL(de_ctx);
    Signature *sig = DetectEngineAppendSig(de_ctx,
                                           "alert tcp any any -> any any "
                                           "(metadata: toto 1; "
                                           "metadata: titi 2, jaivu gros_minet;"
                                           "sid:1; rev:1;)");
    FAIL_IF_NULL(sig);
    FAIL_IF_NULL(sig->metadata); 
    FAIL_IF_NULL(sig->metadata->key); 
    FAIL_IF(strcmp("jaivu", sig->metadata->key));
    FAIL_IF(strcmp("gros_minet", sig->metadata->value));
    FAIL_IF_NULL(sig->metadata->next); 
    dm = sig->metadata->next;
    FAIL_IF(strcmp("titi", dm->key));
    dm = dm->next;
    FAIL_IF_NULL(dm);
    FAIL_IF(strcmp("toto", dm->key));

    DetectEngineCtxFree(de_ctx);
    PASS;
}

#endif /* UNITTESTS */

/**
 * \brief this function registers unit tests for DetectCipService
 */
static void DetectMetadataRegisterTests(void)
{
#ifdef UNITTESTS
    UtRegisterTest("DetectMetadataParseTest01", DetectMetadataParseTest01);
    UtRegisterTest("DetectMetadataParseTest02", DetectMetadataParseTest02);
#endif /* UNITTESTS */
}