detect-filemagic.c

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/* Copyright (C) 2007-2022 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 "decode.h"
 
#include "detect.h"
#include "detect-parse.h"
#include "detect-content.h"
 
#include "detect-engine.h"
#include "detect-engine-mpm.h"
#include "detect-engine-prefilter.h"
#include "detect-engine-content-inspection.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 "util-profiling.h"
 
#include "app-layer.h"
#include "app-layer-parser.h"
 
#include "stream-tcp.h"
 
#include "detect-filemagic.h"
 
#include "conf.h"
 
#ifndef HAVE_MAGIC
 
static int DetectFilemagicSetupNoSupport (DetectEngineCtx *de_ctx, Signature *s, const char *str)
{
    SCLogError("no libmagic support built in, needed for filemagic keyword");
    return -1;
}
 
/**
 * \brief Registration function for keyword: filemagic
 */
void DetectFilemagicRegister(void)
{
    sigmatch_table[DETECT_FILEMAGIC].name = "filemagic";
    sigmatch_table[DETECT_FILEMAGIC].desc = "match on the information libmagic returns about a file";
    sigmatch_table[DETECT_FILEMAGIC].url = "/rules/file-keywords.html#filemagic";
    sigmatch_table[DETECT_FILEMAGIC].Setup = DetectFilemagicSetupNoSupport;
    sigmatch_table[DETECT_FILEMAGIC].flags = SIGMATCH_QUOTES_MANDATORY|SIGMATCH_HANDLE_NEGATION;
}
 
#else /* HAVE_MAGIC */
 
typedef struct DetectFilemagicThreadData {
    magic_t ctx;
} DetectFilemagicThreadData;
 
typedef struct DetectFilemagicData {
    uint8_t *name; /** name of the file to match */
    BmCtx *bm_ctx; /** BM context */
    uint16_t len;  /** name length */
    uint32_t flags;
} DetectFilemagicData;
 
static int DetectFilemagicMatch (DetectEngineThreadCtx *, Flow *,
        uint8_t, File *, const Signature *, const SigMatchCtx *);
static int DetectFilemagicSetup (DetectEngineCtx *, Signature *, const char *);
#ifdef UNITTESTS
static void DetectFilemagicRegisterTests(void);
#endif
static void DetectFilemagicFree(DetectEngineCtx *, void *);
static int g_file_match_list_id = 0;
 
static int DetectFilemagicSetupSticky(DetectEngineCtx *de_ctx, Signature *s, const char *str);
static int g_file_magic_buffer_id = 0;
 
static int PrefilterMpmFilemagicRegister(DetectEngineCtx *de_ctx, SigGroupHead *sgh,
        MpmCtx *mpm_ctx, const DetectBufferMpmRegistry *mpm_reg, int list_id);
static uint8_t DetectEngineInspectFilemagic(DetectEngineCtx *de_ctx, DetectEngineThreadCtx *det_ctx,
        const DetectEngineAppInspectionEngine *engine, const Signature *s, Flow *f, uint8_t flags,
        void *alstate, void *txv, uint64_t tx_id);
 
static int g_magic_thread_ctx_id = -1;
 
/**
 * \brief Registration function for keyword: filemagic
 */
void DetectFilemagicRegister(void)
{
    sigmatch_table[DETECT_FILEMAGIC].name = "filemagic";
    sigmatch_table[DETECT_FILEMAGIC].desc = "match on the information libmagic returns about a file";
    sigmatch_table[DETECT_FILEMAGIC].url = "/rules/file-keywords.html#filemagic";
    sigmatch_table[DETECT_FILEMAGIC].FileMatch = DetectFilemagicMatch;
    sigmatch_table[DETECT_FILEMAGIC].Setup = DetectFilemagicSetup;
    sigmatch_table[DETECT_FILEMAGIC].Free  = DetectFilemagicFree;
#ifdef UNITTESTS
    sigmatch_table[DETECT_FILEMAGIC].RegisterTests = DetectFilemagicRegisterTests;
#endif
    sigmatch_table[DETECT_FILEMAGIC].flags = SIGMATCH_QUOTES_MANDATORY|SIGMATCH_HANDLE_NEGATION;
    sigmatch_table[DETECT_FILEMAGIC].alternative = DETECT_FILE_MAGIC;
 
    sigmatch_table[DETECT_FILE_MAGIC].name = "file.magic";
    sigmatch_table[DETECT_FILE_MAGIC].desc = "sticky buffer to match on the file magic";
    sigmatch_table[DETECT_FILE_MAGIC].url = "/rules/file-keywords.html#filemagic";
    sigmatch_table[DETECT_FILE_MAGIC].Setup = DetectFilemagicSetupSticky;
    sigmatch_table[DETECT_FILE_MAGIC].flags = SIGMATCH_NOOPT|SIGMATCH_INFO_STICKY_BUFFER;
 
    g_file_match_list_id = DetectBufferTypeRegister("files");
 
    AppProto protos_ts[] = { ALPROTO_HTTP1, ALPROTO_SMTP, ALPROTO_FTP, ALPROTO_SMB, ALPROTO_NFS,
        ALPROTO_HTTP2, 0 };
    AppProto protos_tc[] = { ALPROTO_HTTP1, ALPROTO_FTP, ALPROTO_SMB, ALPROTO_NFS, ALPROTO_HTTP2,
        0 };
 
    for (int i = 0; protos_ts[i] != 0; i++) {
        DetectAppLayerInspectEngineRegister2("file.magic", protos_ts[i],
                SIG_FLAG_TOSERVER, 0,
                DetectEngineInspectFilemagic, NULL);
 
        DetectAppLayerMpmRegister2("file.magic", SIG_FLAG_TOSERVER, 2,
                PrefilterMpmFilemagicRegister, NULL, protos_ts[i],
                0);
    }
    for (int i = 0; protos_tc[i] != 0; i++) {
        DetectAppLayerInspectEngineRegister2("file.magic", protos_tc[i],
                SIG_FLAG_TOCLIENT, 0,
                DetectEngineInspectFilemagic, NULL);
 
        DetectAppLayerMpmRegister2("file.magic", SIG_FLAG_TOCLIENT, 2,
                PrefilterMpmFilemagicRegister, NULL, protos_tc[i],
                0);
    }
 
    DetectBufferTypeSetDescriptionByName("file.magic",
            "file magic");
    DetectBufferTypeSupportsMultiInstance("file.magic");
 
    g_file_magic_buffer_id = DetectBufferTypeGetByName("file.magic");
    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 FilemagicThreadLookup(magic_t *ctx, File *file)
{
    if (ctx == NULL || file == NULL || FileDataSize(file) == 0) {
        SCReturnInt(-1);
    }
 
    const uint8_t *data = NULL;
    uint32_t data_len = 0;
    uint64_t offset = 0;
 
    StreamingBufferGetData(file->sb,
                           &data, &data_len, &offset);
    if (offset == 0) {
        if (FileDataSize(file) >= FILEMAGIC_MIN_SIZE) {
            file->magic = MagicThreadLookup(ctx, data, data_len);
        } else if (file->state >= FILE_STATE_CLOSED) {
            file->magic = MagicThreadLookup(ctx, data, data_len);
        }
    }
    SCReturnInt(0);
}
 
/**
 * \brief match the specified filemagic
 *
 * \param t thread local vars
 * \param det_ctx pattern matcher thread local data
 * \param f *LOCKED* flow
 * \param flags direction flags
 * \param file file being inspected
 * \param s signature being inspected
 * \param m sigmatch that we will cast into DetectFilemagicData
 *
 * \retval 0 no match
 * \retval 1 match
 */
static int DetectFilemagicMatch (DetectEngineThreadCtx *det_ctx,
        Flow *f, uint8_t flags, File *file, const Signature *s, const SigMatchCtx *m)
{
    SCEnter();
    int ret = 0;
    DetectFilemagicData *filemagic = (DetectFilemagicData *)m;
 
    DetectFilemagicThreadData *tfilemagic =
        (DetectFilemagicThreadData *)DetectThreadCtxGetKeywordThreadCtx(det_ctx, g_magic_thread_ctx_id);
    if (tfilemagic == NULL) {
        SCReturnInt(0);
    }
 
    if (file->magic == NULL) {
        FilemagicThreadLookup(&tfilemagic->ctx, 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) != NULL)
        {
#ifdef DEBUG
            if (SCLogDebugEnabled()) {
                char *name = SCMalloc(filemagic->len + 1);
                if (name != NULL) {
                    memcpy(name, filemagic->name, filemagic->len);
                    name[filemagic->len] = '\0';
                    SCLogDebug("will look for filemagic %s", name);
                    SCFree(name);
                }
            }
#endif
 
            if (!(filemagic->flags & DETECT_CONTENT_NEGATED)) {
                ret = 1;
            }
        } else if (filemagic->flags & DETECT_CONTENT_NEGATED) {
            SCLogDebug("negated match");
            ret = 1;
        }
    }
 
    SCReturnInt(ret);
}
 
/**
 * \brief Parse the filemagic keyword
 *
 * \param de_ctx Pointer to the detection engine context
 * \param idstr Pointer to the user provided option
 *
 * \retval filemagic pointer to DetectFilemagicData on success
 * \retval NULL on failure
 */
static DetectFilemagicData *DetectFilemagicParse (DetectEngineCtx *de_ctx, const char *str, bool negate)
{
    DetectFilemagicData *filemagic = NULL;
 
    /* We have a correct filemagic option */
    filemagic = SCMalloc(sizeof(DetectFilemagicData));
    if (unlikely(filemagic == NULL))
        goto error;
 
    memset(filemagic, 0x00, sizeof(DetectFilemagicData));
 
    if (DetectContentDataParse ("filemagic", str, &filemagic->name, &filemagic->len) == -1) {
        goto error;
    }
 
    filemagic->bm_ctx = BoyerMooreNocaseCtxInit(filemagic->name, filemagic->len);
    if (filemagic->bm_ctx == NULL) {
        goto error;
    }
 
    if (negate) {
        filemagic->flags |= DETECT_CONTENT_NEGATED;
    }
 
    SCLogDebug("flags %02X", filemagic->flags);
    if (filemagic->flags & DETECT_CONTENT_NEGATED) {
        SCLogDebug("negated filemagic");
    }
 
#ifdef DEBUG
    if (SCLogDebugEnabled()) {
        char *name = SCMalloc(filemagic->len + 1);
        if (name != NULL) {
            memcpy(name, filemagic->name, filemagic->len);
            name[filemagic->len] = '\0';
            SCLogDebug("will look for filemagic %s", name);
            SCFree(name);
        }
    }
#endif
 
    return filemagic;
 
error:
    if (filemagic != NULL)
        DetectFilemagicFree(de_ctx, filemagic);
    return NULL;
}
 
static void *DetectFilemagicThreadInit(void *data /*@unused@*/)
{
    DetectFilemagicThreadData *t = SCCalloc(1, sizeof(DetectFilemagicThreadData));
    if (unlikely(t == NULL)) {
        SCLogError("couldn't alloc ctx memory");
        return NULL;
    }
 
    t->ctx = MagicInitContext();
    if (t->ctx == NULL)
        goto error;
 
    return (void *)t;
 
error:
    if (t->ctx)
        magic_close(t->ctx);
    SCFree(t);
    return NULL;
}
 
static void DetectFilemagicThreadFree(void *ctx)
{
    if (ctx != NULL) {
        DetectFilemagicThreadData *t = (DetectFilemagicThreadData *)ctx;
        if (t->ctx)
            magic_close(t->ctx);
        SCFree(t);
    }
}
 
/**
 * \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, const char *str)
{
    SigMatch *sm = NULL;
 
    DetectFilemagicData *filemagic = DetectFilemagicParse(de_ctx, str, s->init_data->negated);
    if (filemagic == NULL)
        return -1;
 
    g_magic_thread_ctx_id = DetectRegisterThreadCtxFuncs(
            de_ctx, "filemagic", DetectFilemagicThreadInit, NULL, DetectFilemagicThreadFree, 1);
    if (g_magic_thread_ctx_id == -1)
        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, g_file_match_list_id);
 
    s->file_flags |= (FILE_SIG_NEED_FILE|FILE_SIG_NEED_MAGIC);
    return 0;
 
error:
    DetectFilemagicFree(de_ctx, filemagic);
    if (sm != NULL)
        SCFree(sm);
    return -1;
}
 
/**
 * \brief this function will free memory associated with DetectFilemagicData
 *
 * \param filemagic pointer to DetectFilemagicData
 */
static void DetectFilemagicFree(DetectEngineCtx *de_ctx, void *ptr)
{
    if (ptr != NULL) {
        DetectFilemagicData *filemagic = (DetectFilemagicData *)ptr;
        if (filemagic->bm_ctx != NULL) {
            BoyerMooreCtxDeInit(filemagic->bm_ctx);
        }
        if (filemagic->name != NULL)
            SCFree(filemagic->name);
        SCFree(filemagic);
    }
}
 
/* file.magic implementation */
 
/**
 * \brief this function setup the file.magic keyword used in the rule
 *
 * \param de_ctx   Pointer to the Detection Engine Context
 * \param s        Pointer to the Signature to which the current keyword belongs
 * \param str      Should hold an empty string always
 *
 * \retval 0       On success
 */
static int DetectFilemagicSetupSticky(DetectEngineCtx *de_ctx, Signature *s, const char *str)
{
    if (DetectBufferSetActiveList(de_ctx, s, g_file_magic_buffer_id) < 0)
        return -1;
 
    if (g_magic_thread_ctx_id == -1) {
        g_magic_thread_ctx_id = DetectRegisterThreadCtxFuncs(de_ctx, "filemagic",
                DetectFilemagicThreadInit, NULL,
                DetectFilemagicThreadFree, 1);
        if (g_magic_thread_ctx_id == -1)
            return -1;
    }
    return 0;
}
 
static InspectionBuffer *FilemagicGetDataCallback(DetectEngineThreadCtx *det_ctx,
        const DetectEngineTransforms *transforms, Flow *f, uint8_t flow_flags, File *cur_file,
        int list_id, int local_file_id)
{
    SCEnter();
 
    InspectionBuffer *buffer = InspectionBufferMultipleForListGet(det_ctx, list_id, local_file_id);
    if (buffer == NULL)
        return NULL;
    if (buffer->initialized)
        return buffer;
 
    if (cur_file->magic == NULL) {
        DetectFilemagicThreadData *tfilemagic =
            (DetectFilemagicThreadData *)DetectThreadCtxGetKeywordThreadCtx(det_ctx, g_magic_thread_ctx_id);
        if (tfilemagic == NULL) {
            InspectionBufferSetupMultiEmpty(buffer);
            return NULL;
        }
 
        FilemagicThreadLookup(&tfilemagic->ctx, cur_file);
    }
    if (cur_file->magic == NULL) {
        return NULL;
    }
 
    const uint8_t *data = (const uint8_t *)cur_file->magic;
    uint32_t data_len = (uint32_t)strlen(cur_file->magic);
 
    InspectionBufferSetupMulti(buffer, transforms, data, data_len);
 
    SCReturnPtr(buffer, "InspectionBuffer");
}
 
static uint8_t DetectEngineInspectFilemagic(DetectEngineCtx *de_ctx, DetectEngineThreadCtx *det_ctx,
        const DetectEngineAppInspectionEngine *engine, const Signature *s, Flow *f, uint8_t flags,
        void *alstate, void *txv, uint64_t tx_id)
{
    const DetectEngineTransforms *transforms = NULL;
    if (!engine->mpm) {
        transforms = engine->v2.transforms;
    }
 
    AppLayerGetFileState files = AppLayerParserGetTxFiles(f, alstate, txv, flags);
    FileContainer *ffc = files.fc;
    if (ffc == NULL) {
        return DETECT_ENGINE_INSPECT_SIG_CANT_MATCH_FILES;
    }
 
    uint8_t r = DETECT_ENGINE_INSPECT_SIG_NO_MATCH;
    int local_file_id = 0;
    for (File *file = ffc->head; file != NULL; file = file->next) {
        InspectionBuffer *buffer = FilemagicGetDataCallback(
                det_ctx, transforms, f, flags, file, engine->sm_list, local_file_id);
        if (buffer == NULL)
            continue;
 
        det_ctx->buffer_offset = 0;
        det_ctx->discontinue_matching = 0;
        det_ctx->inspection_recursion_counter = 0;
        int match = DetectEngineContentInspection(de_ctx, det_ctx, s, engine->smd,
                                              NULL, f,
                                              (uint8_t *)buffer->inspect,
                                              buffer->inspect_len,
                                              buffer->inspect_offset, DETECT_CI_FLAGS_SINGLE,
                                              DETECT_ENGINE_CONTENT_INSPECTION_MODE_STATE);
        if (match == 1) {
            return DETECT_ENGINE_INSPECT_SIG_MATCH;
        } else {
            r = DETECT_ENGINE_INSPECT_SIG_CANT_MATCH_FILES;
        }
        local_file_id++;
    }
    return r;
}
 
typedef struct PrefilterMpmFilemagic {
    int list_id;
    const MpmCtx *mpm_ctx;
    const DetectEngineTransforms *transforms;
} PrefilterMpmFilemagic;
 
/** \brief Filedata Filedata Mpm prefilter callback
 *
 *  \param det_ctx detection engine thread ctx
 *  \param p packet to inspect
 *  \param f flow to inspect
 *  \param txv tx to inspect
 *  \param pectx inspection context
 */
static void PrefilterTxFilemagic(DetectEngineThreadCtx *det_ctx, const void *pectx, Packet *p,
        Flow *f, void *txv, const uint64_t idx, const AppLayerTxData *txd, const uint8_t flags)
{
    SCEnter();
 
    if (!AppLayerParserHasFilesInDir(txd, flags))
        return;
 
    const PrefilterMpmFilemagic *ctx = (const PrefilterMpmFilemagic *)pectx;
    const MpmCtx *mpm_ctx = ctx->mpm_ctx;
    const int list_id = ctx->list_id;
 
    AppLayerGetFileState files = AppLayerParserGetTxFiles(f, f->alstate, txv, flags);
    FileContainer *ffc = files.fc;
    if (ffc != NULL) {
        int local_file_id = 0;
        for (File *file = ffc->head; file != NULL; file = file->next) {
            InspectionBuffer *buffer = FilemagicGetDataCallback(
                    det_ctx, ctx->transforms, f, flags, file, list_id, local_file_id);
            if (buffer == NULL)
                continue;
 
            if (buffer->inspect_len >= mpm_ctx->minlen) {
                (void)mpm_table[mpm_ctx->mpm_type].Search(mpm_ctx,
                        &det_ctx->mtcu, &det_ctx->pmq,
                        buffer->inspect, buffer->inspect_len);
                PREFILTER_PROFILING_ADD_BYTES(det_ctx, buffer->inspect_len);
            }
            local_file_id++;
        }
    }
}
 
static void PrefilterMpmFilemagicFree(void *ptr)
{
    SCFree(ptr);
}
 
static int PrefilterMpmFilemagicRegister(DetectEngineCtx *de_ctx, SigGroupHead *sgh,
        MpmCtx *mpm_ctx, const DetectBufferMpmRegistry *mpm_reg, int list_id)
{
    PrefilterMpmFilemagic *pectx = SCCalloc(1, sizeof(*pectx));
    if (pectx == NULL)
        return -1;
    pectx->list_id = list_id;
    pectx->mpm_ctx = mpm_ctx;
    pectx->transforms = &mpm_reg->transforms;
 
    return PrefilterAppendTxEngine(de_ctx, sgh, PrefilterTxFilemagic,
            mpm_reg->app_v2.alproto, mpm_reg->app_v2.tx_min_progress,
            pectx, PrefilterMpmFilemagicFree, mpm_reg->pname);
}
#ifdef UNITTESTS /* UNITTESTS */
 
/**
 * \test DetectFilemagicTestParse01
 */
static int DetectFilemagicTestParse01 (void)
{
    DetectFilemagicData *dnd = DetectFilemagicParse(NULL, "secret.pdf", false);
    FAIL_IF_NULL(dnd);
    DetectFilemagicFree(NULL, dnd);
    PASS;
}
 
/**
 * \test DetectFilemagicTestParse02
 */
static int DetectFilemagicTestParse02 (void)
{
    DetectFilemagicData *dnd = DetectFilemagicParse(NULL, "backup.tar.gz", false);
    FAIL_IF_NULL(dnd);
    FAIL_IF_NOT(dnd->len == 13);
    FAIL_IF_NOT(memcmp(dnd->name, "backup.tar.gz", 13) == 0);
    DetectFilemagicFree(NULL, dnd);
    PASS;
}
 
/**
 * \test DetectFilemagicTestParse03
 */
static int DetectFilemagicTestParse03 (void)
{
    DetectFilemagicData *dnd = DetectFilemagicParse(NULL, "cmd.exe", false);
    FAIL_IF_NULL(dnd);
    FAIL_IF_NOT(dnd->len == 7);
    FAIL_IF_NOT(memcmp(dnd->name, "cmd.exe", 7) == 0);
    DetectFilemagicFree(NULL, dnd);
    PASS;
}
 
/**
 * \brief this function registers unit tests for DetectFilemagic
 */
void DetectFilemagicRegisterTests(void)
{
    UtRegisterTest("DetectFilemagicTestParse01", DetectFilemagicTestParse01);
    UtRegisterTest("DetectFilemagicTestParse02", DetectFilemagicTestParse02);
    UtRegisterTest("DetectFilemagicTestParse03", DetectFilemagicTestParse03);
}
#endif /* UNITTESTS */
#endif /* HAVE_MAGIC */