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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 Victor Julien <victor@inliniac.net>
*
*/
#include "suricata-common.h"
#include "detect.h"
#include "detect-parse.h"
#include "detect-engine-prefilter-common.h"
#include "detect-engine-uint.h"
#include "util-byte.h"
#include "detect-tcpmss.h"
/* prototypes */
static int DetectTcpmssMatch (DetectEngineThreadCtx *, Packet *,
const Signature *, const SigMatchCtx *);
static int DetectTcpmssSetup (DetectEngineCtx *, Signature *, const char *);
void DetectTcpmssFree (DetectEngineCtx *, void *);
#ifdef UNITTESTS
void DetectTcpmssRegisterTests (void);
#endif
static int PrefilterSetupTcpmss(DetectEngineCtx *de_ctx, SigGroupHead *sgh);
static bool PrefilterTcpmssIsPrefilterable(const Signature *s);
/**
* \brief Registration function for tcpmss: keyword
*/
void DetectTcpmssRegister(void)
{
sigmatch_table[DETECT_TCPMSS].name = "tcp.mss";
sigmatch_table[DETECT_TCPMSS].desc = "match on TCP MSS option field";
sigmatch_table[DETECT_TCPMSS].url = "/rules/header-keywords.html#tcpmss";
sigmatch_table[DETECT_TCPMSS].Match = DetectTcpmssMatch;
sigmatch_table[DETECT_TCPMSS].Setup = DetectTcpmssSetup;
sigmatch_table[DETECT_TCPMSS].Free = DetectTcpmssFree;
sigmatch_table[DETECT_TCPMSS].SupportsPrefilter = PrefilterTcpmssIsPrefilterable;
sigmatch_table[DETECT_TCPMSS].SetupPrefilter = PrefilterSetupTcpmss;
return;
}
/**
* \brief This function is used to match TCPMSS rule option on a packet with those passed via
* tcpmss:
*
* \param det_ctx pointer to the pattern matcher thread
* \param p pointer to the current packet
* \param ctx pointer to the sigmatch that we will cast into DetectU16Data
*
* \retval 0 no match
* \retval 1 match
*/
static int DetectTcpmssMatch (DetectEngineThreadCtx *det_ctx, Packet *p,
const Signature *s, const SigMatchCtx *ctx)
{
if (!(PKT_IS_TCP(p)) || PKT_IS_PSEUDOPKT(p))
return 0;
if (!(TCP_HAS_MSS(p)))
return 0;
uint16_t ptcpmss = TCP_GET_MSS(p);
const DetectU16Data *tcpmssd = (const DetectU16Data *)ctx;
return DetectU16Match(ptcpmss, tcpmssd);
}
/**
* \brief this function is used to attach the parsed tcpmss data into the current signature
*
* \param de_ctx pointer to the Detection Engine Context
* \param s pointer to the Current Signature
* \param tcpmssstr pointer to the user provided tcpmss options
*
* \retval 0 on Success
* \retval -1 on Failure
*/
static int DetectTcpmssSetup (DetectEngineCtx *de_ctx, Signature *s, const char *tcpmssstr)
{
DetectU16Data *tcpmssd = DetectU16Parse(tcpmssstr);
if (tcpmssd == NULL)
return -1;
SigMatch *sm = SigMatchAlloc();
if (sm == NULL) {
DetectTcpmssFree(de_ctx, tcpmssd);
return -1;
}
sm->type = DETECT_TCPMSS;
sm->ctx = (SigMatchCtx *)tcpmssd;
SigMatchAppendSMToList(s, sm, DETECT_SM_LIST_MATCH);
s->flags |= SIG_FLAG_REQUIRE_PACKET;
return 0;
}
/**
* \brief this function will free memory associated with DetectU16Data
*
* \param ptr pointer to DetectU16Data
*/
void DetectTcpmssFree(DetectEngineCtx *de_ctx, void *ptr)
{
rs_detect_u16_free(ptr);
}
/* prefilter code */
static void
PrefilterPacketTcpmssMatch(DetectEngineThreadCtx *det_ctx, Packet *p, const void *pectx)
{
if (!(PKT_IS_TCP(p)) || PKT_IS_PSEUDOPKT(p))
return;
if (!(TCP_HAS_MSS(p)))
return;
uint16_t ptcpmss = TCP_GET_MSS(p);
/* during setup Suricata will automatically see if there is another
* check that can be added: alproto, sport or dport */
const PrefilterPacketHeaderCtx *ctx = pectx;
if (!PrefilterPacketHeaderExtraMatch(ctx, p))
return;
DetectU16Data du16;
du16.mode = ctx->v1.u8[0];
du16.arg1 = ctx->v1.u16[1];
du16.arg2 = ctx->v1.u16[2];
/* if we match, add all the sigs that use this prefilter. This means
* that these will be inspected further */
if (DetectU16Match(ptcpmss, &du16)) {
SCLogDebug("packet matches tcpmss/hl %u", ptcpmss);
PrefilterAddSids(&det_ctx->pmq, ctx->sigs_array, ctx->sigs_cnt);
}
}
static int PrefilterSetupTcpmss(DetectEngineCtx *de_ctx, SigGroupHead *sgh)
{
return PrefilterSetupPacketHeader(de_ctx, sgh, DETECT_TCPMSS, PrefilterPacketU16Set,
PrefilterPacketU16Compare, PrefilterPacketTcpmssMatch);
}
static bool PrefilterTcpmssIsPrefilterable(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_TCPMSS:
return true;
}
}
return false;
}
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