suricata/src/detect-filemagic.c

/* Copyright (C) 2007-2011 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>
 *
 */

#include "suricata-common.h"
#include "threads.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-engine-state.h"

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

#include "util-debug.h"
#include "util-spm-bm.h"
#include "util-magic.h"
#include "util-print.h"

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

#include "app-layer.h"

#include "stream-tcp.h"

#include "detect-filemagic.h"

int DetectFilemagicMatch (ThreadVars *, DetectEngineThreadCtx *, Flow *, uint8_t, void *, Signature *, SigMatch *);
static int DetectFilemagicSetup (DetectEngineCtx *, Signature *, char *);
void DetectFilemagicRegisterTests(void);
void DetectFilemagicFree(void *);

/**
 * \brief Registration function for keyword: filemagic
 */
void DetectFilemagicRegister(void) {
    sigmatch_table[DETECT_FILEMAGIC].name = "filemagic";
    sigmatch_table[DETECT_FILEMAGIC].Match = NULL;
    sigmatch_table[DETECT_FILEMAGIC].AppLayerMatch = DetectFilemagicMatch;
    sigmatch_table[DETECT_FILEMAGIC].alproto = ALPROTO_HTTP;
    sigmatch_table[DETECT_FILEMAGIC].Setup = DetectFilemagicSetup;
    sigmatch_table[DETECT_FILEMAGIC].Free  = DetectFilemagicFree;
    sigmatch_table[DETECT_FILEMAGIC].RegisterTests = DetectFilemagicRegisterTests;

	SCLogDebug("registering filemagic rule option");
    return;
}

#define FILEMAGIC_MIN_SIZE  512

/**
 *  \brief run the magic check
 *
 *  \param file the file
 *
 *  \retval -1 error
 *  \retval 0 ok
 */
int FilemagicLookup(File *file) {
    if (file == NULL || file->chunks_head == NULL) {
        SCReturnInt(-1);
    }

    /* initial chunk already matching our requirement */
    if (file->chunks_head->len >= FILEMAGIC_MIN_SIZE) {
        file->magic = MagicLookup(file->chunks_head->data, FILEMAGIC_MIN_SIZE);
    } else {
        uint8_t *buf = SCMalloc(FILEMAGIC_MIN_SIZE);
        uint32_t size = 0;

        if (buf != NULL) {
            FileData *ffd = file->chunks_head;

            for ( ; ffd != NULL; ffd = ffd->next) {
                uint32_t copy_len = ffd->len;
                if (size + ffd->len > FILEMAGIC_MIN_SIZE)
                    copy_len = FILEMAGIC_MIN_SIZE - size;

                memcpy(buf + size, ffd->data, copy_len);
                size += copy_len;

                if (size >= FILEMAGIC_MIN_SIZE) {
                    file->magic = MagicLookup(buf, size);
                    break;
                }
                /* file is done but smaller than FILEMAGIC_MIN_SIZE */
                if (ffd->next == NULL && file->state >= FILE_STATE_CLOSED) {
                    file->magic = MagicLookup(buf, size);
                    break;
                }
            }

            SCFree(buf);
        }
    }

    SCReturnInt(0);
}

/**
 * \brief match the specified filemagic
 *
 * \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 DetectFilemagicData
 *
 * \retval 0 no match
 * \retval 1 match
 */
int DetectFilemagicMatch (ThreadVars *t, DetectEngineThreadCtx *det_ctx, Flow *f, uint8_t flags, void *state, Signature *s, SigMatch *m)
{
    SCEnter();
    int ret = 0;
    DetectFilemagicData *filemagic = (DetectFilemagicData *)m->ctx;

    File *file = (File *)state;

    if (file->txid < det_ctx->tx_id)
        SCReturnInt(0);

    if (file->txid > det_ctx->tx_id)
        SCReturnInt(0);

    if (file->magic == NULL) {
        FilemagicLookup(file);
    }

    if (file->magic != NULL) {
        SCLogDebug("magic %s", file->magic);

        /* we include the \0 in the inspection, so patterns can match on the
         * end of the string. */
        if (BoyerMooreNocase(filemagic->name, filemagic->len, (uint8_t *)file->magic,
                    strlen(file->magic) + 1, filemagic->bm_ctx->bmGs,
                    filemagic->bm_ctx->bmBc) != NULL)
        {
#ifdef DEBUG
            if (SCLogDebugEnabled()) {
                char *name = SCMalloc(filemagic->len + 1);
                memcpy(name, filemagic->name, filemagic->len);
                name[filemagic->len] = '\0';
                SCLogDebug("will look for filemagic %s", name);
            }
#endif

            if (!(filemagic->flags & DETECT_CONTENT_NEGATED)) {
                ret = 1;
            }
        }

        if (ret == 0 && filemagic->flags & DETECT_CONTENT_NEGATED) {
            SCLogDebug("negated match");
            ret = 1;
        }
    }

    SCReturnInt(ret);
}

/**
 * \brief Parse the filemagic keyword
 *
 * \param idstr Pointer to the user provided option
 *
 * \retval filemagic pointer to DetectFilemagicData on success
 * \retval NULL on failure
 */
DetectFilemagicData *DetectFilemagicParse (char *str)
{
    DetectFilemagicData *filemagic = NULL;

    /* We have a correct filemagic option */
    filemagic = SCMalloc(sizeof(DetectFilemagicData));
    if (filemagic == NULL)
        goto error;

    memset(filemagic, 0x00, sizeof(DetectFilemagicData));

    if (DetectParseContentString (str, &filemagic->name, &filemagic->len, &filemagic->flags) == -1) {
        goto error;
    }

    filemagic->bm_ctx = BoyerMooreCtxInit(filemagic->name, filemagic->len);
    if (filemagic->bm_ctx == NULL) {
        goto error;
    }

    SCLogDebug("flags %02X", filemagic->flags);
    if (filemagic->flags & DETECT_CONTENT_NEGATED) {
        SCLogDebug("negated filemagic");
    }

    BoyerMooreCtxToNocase(filemagic->bm_ctx, filemagic->name, filemagic->len);
#ifdef DEBUG
    if (SCLogDebugEnabled()) {
        char *name = SCMalloc(filemagic->len + 1);
        memcpy(name, filemagic->name, filemagic->len);
        name[filemagic->len] = '\0';
        SCLogDebug("will look for filemagic %s", name);
    }
#endif

    return filemagic;

error:
    if (filemagic != NULL)
        DetectFilemagicFree(filemagic);
    return NULL;
}

/**
 * \brief this function is used to parse filemagic options
 * \brief into the current signature
 *
 * \param de_ctx pointer to the Detection Engine Context
 * \param s pointer to the Current Signature
 * \param str pointer to the user provided "filemagic" option
 *
 * \retval 0 on Success
 * \retval -1 on Failure
 */
static int DetectFilemagicSetup (DetectEngineCtx *de_ctx, Signature *s, char *str)
{
    DetectFilemagicData *filemagic = NULL;
    SigMatch *sm = NULL;

    filemagic = DetectFilemagicParse(str);
    if (filemagic == NULL)
        goto error;

    /* Okay so far so good, lets get this into a SigMatch
     * and put it in the Signature. */
    sm = SigMatchAlloc();
    if (sm == NULL)
        goto error;

    sm->type = DETECT_FILEMAGIC;
    sm->ctx = (void *)filemagic;

    SigMatchAppendSMToList(s, sm, DETECT_SM_LIST_FILEMATCH);

    if (s->alproto != ALPROTO_UNKNOWN && s->alproto != ALPROTO_HTTP) {
        SCLogError(SC_ERR_CONFLICTING_RULE_KEYWORDS, "rule contains conflicting keywords.");
        goto error;
    }

    AppLayerHtpNeedFileInspection();

    /** \todo remove this once we support more than http */
    s->alproto = ALPROTO_HTTP;

    s->file_flags |= (FILE_SIG_NEED_FILE|FILE_SIG_NEED_MAGIC);
    return 0;

error:
    if (filemagic != NULL)
        DetectFilemagicFree(filemagic);
    if (sm != NULL)
        SCFree(sm);
    return -1;
}

/**
 * \brief this function will free memory associated with DetectFilemagicData
 *
 * \param filemagic pointer to DetectFilemagicData
 */
void DetectFilemagicFree(void *ptr) {
    if (ptr != NULL) {
        DetectFilemagicData *filemagic = (DetectFilemagicData *)ptr;
        if (filemagic->bm_ctx != NULL) {
            BoyerMooreCtxDeInit(filemagic->bm_ctx);
        }
        SCFree(filemagic);
    }
}

#ifdef UNITTESTS /* UNITTESTS */

/**
 * \test DetectFilemagicTestParse01
 */
int DetectFilemagicTestParse01 (void) {
    DetectFilemagicData *dnd = DetectFilemagicParse("secret.pdf");
    if (dnd != NULL) {
        DetectFilemagicFree(dnd);
        return 1;
    }
    return 0;
}

/**
 * \test DetectFilemagicTestParse02
 */
int DetectFilemagicTestParse02 (void) {
    int result = 0;

    DetectFilemagicData *dnd = DetectFilemagicParse("\"backup.tar.gz\"");
    if (dnd != NULL) {
        if (dnd->len == 13 && memcmp(dnd->name, "backup.tar.gz", 13) == 0) {
            result = 1;
        }

        DetectFilemagicFree(dnd);
        return result;
    }
    return 0;
}

/**
 * \test DetectFilemagicTestParse03
 */
int DetectFilemagicTestParse03 (void) {
    int result = 0;

    DetectFilemagicData *dnd = DetectFilemagicParse("cmd.exe");
    if (dnd != NULL) {
        if (dnd->len == 7 && memcmp(dnd->name, "cmd.exe", 7) == 0) {
            result = 1;
        }

        DetectFilemagicFree(dnd);
        return result;
    }
    return 0;
}

#endif /* UNITTESTS */

/**
 * \brief this function registers unit tests for DetectFilemagic
 */
void DetectFilemagicRegisterTests(void) {
#ifdef UNITTESTS /* UNITTESTS */
    UtRegisterTest("DetectFilemagicTestParse01", DetectFilemagicTestParse01, 1);
    UtRegisterTest("DetectFilemagicTestParse02", DetectFilemagicTestParse02, 1);
    UtRegisterTest("DetectFilemagicTestParse03", DetectFilemagicTestParse03, 1);
#endif /* UNITTESTS */
}