transform: Add case-changing transforms

doc/userguide/rules/transforms.rst

@@ -134,3 +134,23 @@ Example::
 
     alert http any any -> any any (msg:"HTTP with xor"; http.uri; \
         xor:"0d0ac8ff"; content:"password="; sid:1;)
+
+to_lowercase
+------------
+
+Converts the buffer to lowercase.
+
+Example::
+
+    alert http any any -> any any (http.uri; to_lowercase; \
+        content:"|this text has been converted to lowercase|"; sid:1;)
+
+to_uppercase
+------------
+
+Converts the buffer to uppercase.
+
+Example::
+
+    alert http any any -> any any (http.uri; to_uppercase; \
+        content:"|THIS TEXT HAS BEEN CONVERTED TO UPPERCASE|"; sid:1;)

src/Makefile.am

@@ -337,6 +337,7 @@ noinst_HEADERS = \
 	detect-tls-version.h \
 	detect-tls-random.h \
 	detect-tos.h \
+	detect-transform-casechange.h \
 	detect-transform-compress-whitespace.h \
 	detect-transform-dotprefix.h \
 	detect-transform-md5.h \
@@ -946,6 +947,7 @@ libsuricata_c_a_SOURCES = \
 	detect-tls-version.c \
 	detect-tls-random.c \
 	detect-tos.c \
+	detect-transform-casechange.c \
 	detect-transform-compress-whitespace.c \
 	detect-transform-dotprefix.c \
 	detect-transform-md5.c \

src/detect-engine-register.c

@@ -244,6 +244,7 @@
 #include "detect-transform-pcrexform.h"
 #include "detect-transform-urldecode.h"
 #include "detect-transform-xor.h"
+#include "detect-transform-casechange.h"
 
 #include "util-rule-vars.h"
 
@@ -696,6 +697,8 @@ void SigTableSetup(void)
     DetectTransformPcrexformRegister();
     DetectTransformUrlDecodeRegister();
     DetectTransformXorRegister();
+    DetectTransformToLowerRegister();
+    DetectTransformToUpperRegister();
 
     DetectFileHandlerRegister();
 

src/detect-engine-register.h

@@ -321,6 +321,8 @@ enum DetectKeywordId {
     DETECT_TRANSFORM_PCREXFORM,
     DETECT_TRANSFORM_URL_DECODE,
     DETECT_TRANSFORM_XOR,
+    DETECT_TRANSFORM_TOLOWER,
+    DETECT_TRANSFORM_TOUPPER,
 
     DETECT_AL_IKE_EXCH_TYPE,
     DETECT_AL_IKE_SPI_INITIATOR,

src/detect-transform-casechange.c

@@ -0,0 +1,118 @@
+/* Copyright (C) 2023 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 <jlucovsky@oisf.net>
+ *
+ * Implements case changing transforms
+ */
+#include "suricata-common.h"
+#include "detect.h"
+#include "detect-engine.h"
+#include "detect-parse.h"
+#include "detect-transform-casechange.h"
+
+/**
+ *  \internal
+ *  \brief Apply the to_lowercase keyword to the last pattern match
+ *  \param det_ctx detection engine ctx
+ *  \param s signature
+ *  \param optstr options string
+ *  \retval 0 ok
+ *  \retval -1 failure
+ */
+static int DetectTransformToLowerSetup(DetectEngineCtx *de_ctx, Signature *s, const char *optstr)
+{
+    SCEnter();
+
+    int r = DetectSignatureAddTransform(s, DETECT_TRANSFORM_TOLOWER, NULL);
+
+    SCReturnInt(r);
+}
+
+static void DetectTransformToLower(InspectionBuffer *buffer, void *options)
+{
+    const uint8_t *input = buffer->inspect;
+    const uint32_t input_len = buffer->inspect_len;
+
+    if (input_len == 0) {
+        return;
+    }
+
+    uint8_t output[input_len];
+    for (uint32_t i = 0; i < input_len; i++) {
+        output[i] = u8_tolower(input[i]);
+    }
+
+    InspectionBufferCopy(buffer, output, input_len);
+}
+/**
+ *  \internal
+ *  \brief Apply the to_uppercase keyword to the last pattern match
+ *  \param det_ctx detection engine ctx
+ *  \param s signature
+ *  \param optstr options string
+ *  \retval 0 ok
+ *  \retval -1 failure
+ */
+static int DetectTransformToUpperSetup(DetectEngineCtx *de_ctx, Signature *s, const char *optstr)
+{
+    SCEnter();
+
+    int r = DetectSignatureAddTransform(s, DETECT_TRANSFORM_TOUPPER, NULL);
+
+    SCReturnInt(r);
+}
+
+static void DetectTransformToUpper(InspectionBuffer *buffer, void *options)
+{
+    const uint8_t *input = buffer->inspect;
+    const uint32_t input_len = buffer->inspect_len;
+
+    if (input_len == 0) {
+        return;
+    }
+
+    uint8_t output[input_len];
+    for (uint32_t i = 0; i < input_len; i++) {
+        output[i] = u8_toupper(input[i]);
+    }
+
+    InspectionBufferCopy(buffer, output, input_len);
+}
+
+void DetectTransformToUpperRegister(void)
+{
+    sigmatch_table[DETECT_TRANSFORM_TOUPPER].name = "to_uppercase";
+    sigmatch_table[DETECT_TRANSFORM_TOUPPER].desc = "convert buffer to uppercase";
+    sigmatch_table[DETECT_TRANSFORM_TOUPPER].url = "/rules/transforms.html#to_uppercase";
+    sigmatch_table[DETECT_TRANSFORM_TOUPPER].Transform = DetectTransformToUpper;
+    sigmatch_table[DETECT_TRANSFORM_TOUPPER].Setup = DetectTransformToUpperSetup;
+    sigmatch_table[DETECT_TRANSFORM_TOUPPER].flags |= SIGMATCH_NOOPT;
+}
+
+void DetectTransformToLowerRegister(void)
+{
+    sigmatch_table[DETECT_TRANSFORM_TOLOWER].name = "to_lowercase";
+    sigmatch_table[DETECT_TRANSFORM_TOLOWER].desc = "convert buffer to lowercase";
+    sigmatch_table[DETECT_TRANSFORM_TOLOWER].url = "/rules/transforms.html#to_lowercase";
+    sigmatch_table[DETECT_TRANSFORM_TOLOWER].Transform = DetectTransformToLower;
+    sigmatch_table[DETECT_TRANSFORM_TOLOWER].Setup = DetectTransformToLowerSetup;
+    sigmatch_table[DETECT_TRANSFORM_TOLOWER].flags |= SIGMATCH_NOOPT;
+}

src/detect-transform-casechange.h

@@ -0,0 +1,31 @@
+/* Copyright (C) 2023 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 <jlucovsky@oisf.net>
+ */
+
+#ifndef __DETECT_TRANSFORM_CASECHANGE_H
+#define __DETECT_TRANSFORM_CASECHANGE_H
+
+/* prototypes */
+void DetectTransformToLowerRegister(void);
+void DetectTransformToUpperRegister(void);
+
+#endif /* __DETECT_TRANSFORM_CASECHANGE_H */