detect-metadata.c

Go to the documentation of this file.

/* 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 management.
 */
 
#include "suricata-common.h"
#include "detect.h"
#include "detect-parse.h"
#include "detect-engine.h"
#include "detect-metadata.h"
#include "util-hash-string.h"
#include "rust.h"
#include "util-validate.h"
 
static int DetectMetadataSetup (DetectEngineCtx *, Signature *, const char *);
#ifdef UNITTESTS
static void DetectMetadataRegisterTests(void);
#endif
 
void DetectMetadataRegister (void)
{
    sigmatch_table[DETECT_METADATA].name = "metadata";
    sigmatch_table[DETECT_METADATA].desc = "used for logging";
    sigmatch_table[DETECT_METADATA].url = "/rules/meta.html#metadata";
    sigmatch_table[DETECT_METADATA].Match = NULL;
    sigmatch_table[DETECT_METADATA].Setup = DetectMetadataSetup;
    sigmatch_table[DETECT_METADATA].Free  = NULL;
#ifdef UNITTESTS
    sigmatch_table[DETECT_METADATA].RegisterTests = DetectMetadataRegisterTests;
#endif
}
 
/**
 *  \brief Free a Metadata object
 */
void DetectMetadataFree(DetectMetadata *mdata)
{
    SCEnter();
 
    SCFree(mdata);
 
    SCReturn;
}
 
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 *DetectMetadataHashAdd(DetectEngineCtx *de_ctx, const char *string)
{
    const char *hstring = (char *)HashTableLookup(
            de_ctx->metadata_table, (void *)string, (uint16_t)strlen(string));
    if (hstring) {
        return hstring;
    }
 
    const char *astring = SCStrdup(string);
    if (astring == NULL) {
        return NULL;
    }
 
    if (HashTableAdd(de_ctx->metadata_table, (void *)astring, (uint16_t)strlen(astring)) == 0) {
        return (char *)HashTableLookup(
                de_ctx->metadata_table, (void *)astring, (uint16_t)strlen(astring));
    } else {
        SCFree((void *)astring);
    }
    return NULL;
}
 
static int SortHelper(const void *a, const void *b)
{
    const DetectMetadata *ma = *(const DetectMetadata **)a;
    const DetectMetadata *mb = *(const DetectMetadata **)b;
    return strcasecmp(ma->key, mb->key);
}
 
static char *CraftPreformattedJSON(const DetectMetadata *head)
{
    int cnt = 0;
    for (const DetectMetadata *m = head; m != NULL; m = m->next) {
        cnt++;
    }
    if (cnt == 0)
        return NULL;
 
    // a rule can not have that many metadata
    DEBUG_VALIDATE_BUG_ON(cnt > DETECT_MAX_RULE_SIZE);
    const DetectMetadata *array[cnt];
    int i = 0;
    for (const DetectMetadata *m = head; m != NULL; m = m->next) {
        array[i++] = m;
    }
    BUG_ON(i != cnt);
    qsort(array, cnt, sizeof(DetectMetadata *), SortHelper);
 
    SCJsonBuilder *js = SCJbNewObject();
    if (js == NULL)
        return NULL;
 
    /* array is sorted by key, so we can create a jsonbuilder object
     * with each key appearing just once with one or more values */
    bool array_open = false;
    for (int j = 0; j < cnt; j++) {
        const DetectMetadata *m = array[j];
        const DetectMetadata *nm = j + 1 < cnt ? array[j + 1] : NULL;
        DEBUG_VALIDATE_BUG_ON(m == NULL); // for scan-build
 
        if (nm && strcasecmp(m->key, nm->key) == 0) {
            if (!array_open) {
                SCJbOpenArray(js, m->key);
                array_open = true;
            }
            SCJbAppendString(js, m->value);
        } else {
            if (!array_open) {
                SCJbOpenArray(js, m->key);
            }
            SCJbAppendString(js, m->value);
            SCJbClose(js);
            array_open = false;
        }
    }
    SCJbClose(js);
    /* we have a complete json builder. Now store it as a C string */
    const size_t len = SCJbLen(js);
#define MD_STR "\"metadata\":"
#define MD_STR_LEN (sizeof(MD_STR) - 1)
    char *str = SCMalloc(len + MD_STR_LEN + 1);
    if (str == NULL) {
        SCJbFree(js);
        return NULL;
    }
    char *ptr = str;
    memcpy(ptr, MD_STR, MD_STR_LEN);
    ptr += MD_STR_LEN;
    memcpy(ptr, SCJbPtr(js), len);
    ptr += len;
    *ptr = '\0';
#undef MD_STR
#undef MD_STR_LEN
    SCJbFree(js);
    return str;
}
 
static int DetectMetadataParse(DetectEngineCtx *de_ctx, Signature *s, const char *metadatastr)
{
    DetectMetadata *head = s->metadata ? s->metadata->list : NULL;
    char copy[strlen(metadatastr)+1];
    strlcpy(copy, metadatastr, sizeof(copy));
    char *xsaveptr = NULL;
    char *key = strtok_r(copy, ",", &xsaveptr);
    while (key != NULL) {
        while (*key != '\0' && isblank(*key)) {
            key++;
        }
        char *val = strchr(key, ' ');
        if (val != NULL) {
            *val++ = '\0';
            while (*val != '\0' && isblank(*val)) {
                val++;
            }
        } else {
            /* Skip metadata without a value. */
            goto next;
        }
 
        /* Also skip metadata if the key or value is empty. */
        if (strlen(key) == 0 || strlen(val) == 0) {
            goto next;
        }
 
        const char *hkey = DetectMetadataHashAdd(de_ctx, key);
        if (hkey == NULL) {
            SCLogError("can't create metadata key");
            continue;
        }
 
        const char *hval = DetectMetadataHashAdd(de_ctx, val);
        if (hval == NULL) {
            SCLogError("can't create metadata value");
            goto next;
        }
 
        SCLogDebug("key: %s, value: %s", hkey, hval);
 
        DetectMetadata *dkv = SCMalloc(sizeof(DetectMetadata));
        if (dkv == NULL) {
            goto next;
        }
        dkv->key = hkey;
        dkv->value = hval;
        dkv->next = head;
        head = dkv;
 
    next:
        key = strtok_r(NULL, ",", &xsaveptr);
    }
    if (head != NULL) {
        if (s->metadata == NULL) {
            s->metadata = SCCalloc(1, sizeof(*s->metadata));
            if (s->metadata == NULL) {
                for (DetectMetadata *m = head; m != NULL; ) {
                    DetectMetadata *next_m = m->next;
                    DetectMetadataFree(m);
                    m = next_m;
                }
                return -1;
            }
        }
        s->metadata->list = head;
        SCFree(s->metadata->json_str);
        s->metadata->json_str = CraftPreformattedJSON(head);
    }
    return 0;
}
 
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 = 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->list); 
    FAIL_IF_NULL(sig->metadata->list->key); 
    FAIL_IF(strcmp("jaivu", sig->metadata->list->key));
    FAIL_IF(strcmp("gros_minet", sig->metadata->list->value));
    FAIL_IF_NULL(sig->metadata->list->next); 
    DetectMetadata *dm = sig->metadata->list->next;
    FAIL_IF(strcmp("titi", dm->key));
    dm = dm->next;
    FAIL_IF_NULL(dm);
    FAIL_IF(strcmp("toto", dm->key));
    FAIL_IF_NOT(strcmp(sig->metadata->json_str,
        "\"metadata\":{\"jaivu\":[\"gros_minet\"],\"titi\":[\"2\"],\"toto\":[\"1\"]}") == 0);
    DetectEngineCtxFree(de_ctx);
    PASS;
}
 
/**
 * \brief this function registers unit tests for DetectCipService
 */
static void DetectMetadataRegisterTests(void)
{
    UtRegisterTest("DetectMetadataParseTest01", DetectMetadataParseTest01);
    UtRegisterTest("DetectMetadataParseTest02", DetectMetadataParseTest02);
}
#endif /* UNITTESTS */