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/* Copyright (C) 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 Jeff Lucovsky <jeff@lucovsky.org>
*
* Implements the pcrexform transform keyword with option support
*/
#include "suricata-common.h"
#include "detect.h"
#include "detect-engine.h"
#include "detect-parse.h"
#include "detect-transform-pcrexform.h"
#include "detect-pcre.h"
typedef struct DetectTransformPcrexformData {
pcre2_code *regex;
pcre2_match_context *context;
} DetectTransformPcrexformData;
static int DetectTransformPcrexformSetup (DetectEngineCtx *, Signature *, const char *);
static void DetectTransformPcrexformFree(DetectEngineCtx *, void *);
static void DetectTransformPcrexform(InspectionBuffer *buffer, void *options);
#ifdef UNITTESTS
void DetectTransformPcrexformRegisterTests (void);
#endif
void DetectTransformPcrexformRegister(void)
{
sigmatch_table[DETECT_TRANSFORM_PCREXFORM].name = "pcrexform";
sigmatch_table[DETECT_TRANSFORM_PCREXFORM].desc =
"modify buffer via PCRE before inspection";
sigmatch_table[DETECT_TRANSFORM_PCREXFORM].url = "/rules/transforms.html#pcre-xform";
sigmatch_table[DETECT_TRANSFORM_PCREXFORM].Transform =
DetectTransformPcrexform;
sigmatch_table[DETECT_TRANSFORM_PCREXFORM].Free =
DetectTransformPcrexformFree;
sigmatch_table[DETECT_TRANSFORM_PCREXFORM].Setup =
DetectTransformPcrexformSetup;
#ifdef UNITTESTS
sigmatch_table[DETECT_TRANSFORM_PCREXFORM].RegisterTests = DetectTransformPcrexformRegisterTests;
#endif
sigmatch_table[DETECT_TRANSFORM_PCREXFORM].flags |= SIGMATCH_QUOTES_MANDATORY;
}
static void DetectTransformPcrexformFree(DetectEngineCtx *de_ctx, void *ptr)
{
if (ptr != NULL) {
DetectTransformPcrexformData *pxd = (DetectTransformPcrexformData *) ptr;
pcre2_match_context_free(pxd->context);
pcre2_code_free(pxd->regex);
SCFree(pxd);
}
}
/**
* \internal
* \brief Apply the pcrexform keyword to the last pattern match
* \param det_ctx detection engine ctx
* \param s signature
* \param regexstr options string
* \retval 0 ok
* \retval -1 failure
*/
static int DetectTransformPcrexformSetup (DetectEngineCtx *de_ctx, Signature *s, const char *regexstr)
{
SCEnter();
// Create pxd from regexstr
DetectTransformPcrexformData *pxd = SCCalloc(1, sizeof(*pxd));
if (pxd == NULL) {
SCLogDebug("pxd allocation failed");
SCReturnInt(-1);
}
pxd->context = pcre2_match_context_create(NULL);
if (pxd->context == NULL) {
SCFree(pxd);
SCReturnInt(-1);
}
pcre2_set_match_limit(pxd->context, SC_MATCH_LIMIT_DEFAULT);
pcre2_set_recursion_limit(pxd->context, SC_MATCH_LIMIT_RECURSION_DEFAULT);
int en;
PCRE2_SIZE eo;
pxd->regex = pcre2_compile((PCRE2_SPTR8)regexstr, PCRE2_ZERO_TERMINATED, 0, &en, &eo, NULL);
if (pxd->regex == NULL) {
PCRE2_UCHAR buffer[256];
pcre2_get_error_message(en, buffer, sizeof(buffer));
SCLogError("pcre2 compile of \"%s\" failed at "
"offset %d: %s",
regexstr, (int)eo, buffer);
pcre2_match_context_free(pxd->context);
SCFree(pxd);
SCReturnInt(-1);
}
// check pcd->regex has exactly one capture expression
uint32_t nb;
if (pcre2_pattern_info(pxd->regex, PCRE2_INFO_CAPTURECOUNT, &nb) < 0) {
SCLogError("pcrexform failed getting info about capturecount");
DetectTransformPcrexformFree(de_ctx, pxd);
SCReturnInt(-1);
}
if (nb != 1) {
SCLogError("pcrexform needs exactly one substring capture, found %" PRIu32, nb);
DetectTransformPcrexformFree(de_ctx, pxd);
SCReturnInt(-1);
}
int r = DetectSignatureAddTransform(s, DETECT_TRANSFORM_PCREXFORM, pxd);
if (r != 0) {
DetectTransformPcrexformFree(de_ctx, pxd);
}
SCReturnInt(r);
}
static void DetectTransformPcrexform(InspectionBuffer *buffer, void *options)
{
const char *input = (const char *)buffer->inspect;
const uint32_t input_len = buffer->inspect_len;
DetectTransformPcrexformData *pxd = options;
pcre2_match_data *match = pcre2_match_data_create_from_pattern(pxd->regex, NULL);
int ret = pcre2_match(pxd->regex, (PCRE2_SPTR8)input, input_len, 0, 0, match, pxd->context);
if (ret > 0) {
const char *str;
PCRE2_SIZE caplen;
ret = pcre2_substring_get_bynumber(match, 1, (PCRE2_UCHAR8 **)&str, &caplen);
if (ret >= 0) {
InspectionBufferCopy(buffer, (uint8_t *)str, (uint32_t)caplen);
pcre2_substring_free((PCRE2_UCHAR8 *)str);
}
}
pcre2_match_data_free(match);
}
#ifdef UNITTESTS
#include "tests/detect-transform-pcrexform.c"
#endif
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