--- /dev/null
+/* 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 Philippe Antoine <p.antoine@catenacyber.fr>
+ *
+ * Implements the url_decode transform keyword
+ */
+
+#include "suricata-common.h"
+
+#include "detect.h"
+#include "detect-engine.h"
+#include "detect-engine-prefilter.h"
+#include "detect-parse.h"
+#include "detect-transform-urldecode.h"
+
+#include "util-unittest.h"
+#include "util-print.h"
+
+static int DetectTransformUrlDecodeSetup (DetectEngineCtx *, Signature *, const char *);
+#ifdef UNITTESTS
+static void DetectTransformUrlDecodeRegisterTests(void);
+#endif
+
+static void TransformUrlDecode(InspectionBuffer *buffer, void *options);
+
+void DetectTransformUrlDecodeRegister(void)
+{
+ sigmatch_table[DETECT_TRANSFORM_URL_DECODE].name = "url_decode";
+ sigmatch_table[DETECT_TRANSFORM_URL_DECODE].desc =
+ "modify buffer to decode urlencoded data before inspection";
+ sigmatch_table[DETECT_TRANSFORM_URL_DECODE].url = "/rules/transforms.html#url-decode";
+ sigmatch_table[DETECT_TRANSFORM_URL_DECODE].Transform =
+ TransformUrlDecode;
+ sigmatch_table[DETECT_TRANSFORM_URL_DECODE].Setup =
+ DetectTransformUrlDecodeSetup;
+#ifdef UNITTESTS
+ sigmatch_table[DETECT_TRANSFORM_URL_DECODE].RegisterTests =
+ DetectTransformUrlDecodeRegisterTests;
+#endif
+
+ sigmatch_table[DETECT_TRANSFORM_URL_DECODE].flags |= SIGMATCH_NOOPT;
+}
+
+/**
+ * \internal
+ * \brief Apply the transform keyword to the last pattern match
+ * \param det_ctx detection engine ctx
+ * \param s signature
+ * \param nullstr should be null
+ * \retval 0 ok
+ * \retval -1 failure
+ */
+static int DetectTransformUrlDecodeSetup (DetectEngineCtx *de_ctx, Signature *s, const char *nullstr)
+{
+ SCEnter();
+ int r = DetectSignatureAddTransform(s, DETECT_TRANSFORM_URL_DECODE, NULL);
+ SCReturnInt(r);
+}
+
+// util function so as to ease reuse sometimes
+static bool BufferUrlDecode(const uint8_t *input, const uint32_t input_len, uint8_t *output, uint32_t *output_size)
+{
+ bool changed = false;
+ uint8_t *oi = output;
+ //PrintRawDataFp(stdout, input, input_len);
+ for (uint32_t i = 0; i < input_len; i++) {
+ if (input[i] == '%') {
+ if (i + 2 < input_len) {
+ if ((isxdigit(input[i+1])) && (isxdigit(input[i+2]))) {
+ // Decode %HH encoding.
+ *oi = (input[i+1] >= 'A' ? ((input[i+1] & 0xdf) - 'A') + 10 : (input[i+1] - '0')) << 4;
+ *oi |= (input[i+2] >= 'A' ? ((input[i+2] & 0xdf) - 'A') + 10 : (input[i+2] - '0'));
+ oi++;
+ // one more increment before looping
+ i += 2;
+ changed = true;
+ } else {
+ // leaves incorrect percent
+ // does not handle unicode %u encoding
+ *oi++ = input[i];
+ }
+ } else {
+ // leaves trailing incomplete percent
+ *oi++ = input[i];
+ }
+ } else if (input[i] == '+') {
+ *oi++ = ' ';
+ changed = true;
+ } else {
+ *oi++ = input[i];
+ }
+ }
+ *output_size = oi - output;
+ return changed;
+}
+
+static void TransformUrlDecode(InspectionBuffer *buffer, void *options)
+{
+ uint32_t output_size;
+ bool changed;
+
+ const uint8_t *input = buffer->inspect;
+ const uint32_t input_len = buffer->inspect_len;
+ uint8_t output[input_len]; // we can only shrink
+
+ changed = BufferUrlDecode(input, input_len, output, &output_size);
+
+ if (changed) {
+ InspectionBufferCopy(buffer, output, output_size);
+ }
+}
+
+#ifdef UNITTESTS
+static int DetectTransformUrlDecodeTest01(void)
+{
+ const uint8_t *input = (const uint8_t *)"Suricata%20is+%27%61wesome%21%27%25%30%30%ZZ%4";
+ uint32_t input_len = strlen((char *)input);
+
+ InspectionBuffer buffer;
+ InspectionBufferInit(&buffer, 8);
+ InspectionBufferSetup(&buffer, input, input_len);
+ PrintRawDataFp(stdout, buffer.inspect, buffer.inspect_len);
+ TransformUrlDecode(&buffer, NULL);
+ PrintRawDataFp(stdout, buffer.inspect, buffer.inspect_len);
+ FAIL_IF (buffer.inspect_len != strlen("Suricata is 'awesome!'%00%ZZ%4"));
+ FAIL_IF (memcmp(buffer.inspect, "Suricata is 'awesome!'%00%ZZ%4", buffer.inspect_len) != 0);
+ InspectionBufferFree(&buffer);
+ PASS;
+}
+
+static int DetectTransformUrlDecodeTest02(void)
+{
+ const char rule[] = "alert http any any -> any any (http.request_body; url_decode; content:\"mail=test@oisf.net\"; sid:1;)";
+ ThreadVars th_v;
+ DetectEngineThreadCtx *det_ctx = NULL;
+ memset(&th_v, 0, sizeof(th_v));
+
+ DetectEngineCtx *de_ctx = DetectEngineCtxInit();
+ FAIL_IF_NULL(de_ctx);
+ Signature *s = DetectEngineAppendSig(de_ctx, rule);
+ FAIL_IF_NULL(s);
+ SigGroupBuild(de_ctx);
+ DetectEngineThreadCtxInit(&th_v, (void *)de_ctx, (void *)&det_ctx);
+ DetectEngineThreadCtxDeinit(&th_v, (void *)det_ctx);
+ DetectEngineCtxFree(de_ctx);
+ PASS;
+}
+
+static void DetectTransformUrlDecodeRegisterTests(void)
+{
+ UtRegisterTest("DetectTransformUrlDecodeTest01",
+ DetectTransformUrlDecodeTest01);
+ UtRegisterTest("DetectTransformUrlDecodeTest02",
+ DetectTransformUrlDecodeTest02);
+}
+#endif
projects / thirdparty / suricata.git / commitdiff
