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/* Copyright (C) 2007-2020 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 Gurvinder Singh <gurvindersighdahiya@gmail.com>
* \author Victor Julien <victor@inliniac.net>
*
* Implements the ttl keyword including prefilter support.
*/
#include "suricata-common.h"
#include "stream-tcp.h"
#include "detect.h"
#include "detect-parse.h"
#include "detect-engine-prefilter-common.h"
#include "detect-engine-uint.h"
#include "detect-ttl.h"
#include "util-debug.h"
#include "util-byte.h"
/* prototypes */
static int DetectTtlMatch (DetectEngineThreadCtx *, Packet *,
const Signature *, const SigMatchCtx *);
static int DetectTtlSetup (DetectEngineCtx *, Signature *, const char *);
void DetectTtlFree (DetectEngineCtx *, void *);
#ifdef UNITTESTS
void DetectTtlRegisterTests (void);
#endif
static int PrefilterSetupTtl(DetectEngineCtx *de_ctx, SigGroupHead *sgh);
static bool PrefilterTtlIsPrefilterable(const Signature *s);
/**
* \brief Registration function for ttl: keyword
*/
void DetectTtlRegister(void)
{
sigmatch_table[DETECT_TTL].name = "ttl";
sigmatch_table[DETECT_TTL].desc = "check for a specific IP time-to-live value";
sigmatch_table[DETECT_TTL].url = "/rules/header-keywords.html#ttl";
sigmatch_table[DETECT_TTL].Match = DetectTtlMatch;
sigmatch_table[DETECT_TTL].Setup = DetectTtlSetup;
sigmatch_table[DETECT_TTL].Free = DetectTtlFree;
#ifdef UNITTESTS
sigmatch_table[DETECT_TTL].RegisterTests = DetectTtlRegisterTests;
#endif
sigmatch_table[DETECT_TTL].SupportsPrefilter = PrefilterTtlIsPrefilterable;
sigmatch_table[DETECT_TTL].SetupPrefilter = PrefilterSetupTtl;
return;
}
/**
* \brief This function is used to match TTL rule option on a packet with
* those passed via ttl
*
* \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 DetectU8Data
*
* \retval 0 no match
* \retval 1 match
*/
static int DetectTtlMatch (DetectEngineThreadCtx *det_ctx, Packet *p,
const Signature *s, const SigMatchCtx *ctx)
{
if (PKT_IS_PSEUDOPKT(p))
return 0;
uint8_t pttl;
if (PKT_IS_IPV4(p)) {
pttl = IPV4_GET_IPTTL(p);
} else if (PKT_IS_IPV6(p)) {
pttl = IPV6_GET_HLIM(p);
} else {
SCLogDebug("Packet is not IPv4 or IPv6");
return 0;
}
const DetectU8Data *ttld = (const DetectU8Data *)ctx;
return DetectU8Match(pttl, ttld);
}
/**
* \brief this function is used to attld the parsed ttl data into the current signature
*
* \param de_ctx pointer to the Detection Engine Context
* \param s pointer to the Current Signature
* \param ttlstr pointer to the user provided ttl options
*
* \retval 0 on Success
* \retval -1 on Failure
*/
static int DetectTtlSetup (DetectEngineCtx *de_ctx, Signature *s, const char *ttlstr)
{
DetectU8Data *ttld = DetectU8Parse(ttlstr);
if (ttld == NULL)
return -1;
SigMatch *sm = SigMatchAlloc();
if (sm == NULL) {
DetectTtlFree(de_ctx, ttld);
return -1;
}
sm->type = DETECT_TTL;
sm->ctx = (SigMatchCtx *)ttld;
SigMatchAppendSMToList(s, sm, DETECT_SM_LIST_MATCH);
s->flags |= SIG_FLAG_REQUIRE_PACKET;
return 0;
}
/**
* \brief this function will free memory associated with DetectU8Data
*
* \param ptr pointer to DetectU8Data
*/
void DetectTtlFree(DetectEngineCtx *de_ctx, void *ptr)
{
rs_detect_u8_free(ptr);
}
/* prefilter code */
static void
PrefilterPacketTtlMatch(DetectEngineThreadCtx *det_ctx, Packet *p, const void *pectx)
{
if (PKT_IS_PSEUDOPKT(p)) {
SCReturn;
}
uint8_t pttl;
if (PKT_IS_IPV4(p)) {
pttl = IPV4_GET_IPTTL(p);
} else if (PKT_IS_IPV6(p)) {
pttl = IPV6_GET_HLIM(p);
} else {
SCLogDebug("Packet is not IPv4 or IPv6");
return;
}
const PrefilterPacketHeaderCtx *ctx = pectx;
if (!PrefilterPacketHeaderExtraMatch(ctx, p))
return;
DetectU8Data du8;
du8.mode = ctx->v1.u8[0];
du8.arg1 = ctx->v1.u8[1];
du8.arg2 = ctx->v1.u8[2];
if (DetectU8Match(pttl, &du8)) {
SCLogDebug("packet matches ttl/hl %u", pttl);
PrefilterAddSids(&det_ctx->pmq, ctx->sigs_array, ctx->sigs_cnt);
}
}
static int PrefilterSetupTtl(DetectEngineCtx *de_ctx, SigGroupHead *sgh)
{
return PrefilterSetupPacketHeader(de_ctx, sgh, DETECT_TTL, PrefilterPacketU8Set,
PrefilterPacketU8Compare, PrefilterPacketTtlMatch);
}
static bool PrefilterTtlIsPrefilterable(const Signature *s)
{
const SigMatch *sm;
for (sm = s->init_data->smlists[DETECT_SM_LIST_MATCH] ; sm != NULL; sm = sm->next) {
switch (sm->type) {
case DETECT_TTL:
return true;
}
}
return false;
}
#ifdef UNITTESTS
#include "tests/detect-ttl.c"
#endif
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