1 files changed, 88 insertions, 0 deletions
diff --git a/src/detect-transform-header-lowercase.c b/src/detect-transform-header-lowercase.c
new file mode 100644
index 0000000..7c77620
--- /dev/null
+++ b/src/detect-transform-header-lowercase.c
@@ -0,0 +1,88 @@
+/* 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 Philippe Antoine <contact@catenacyber.fr>
+ *
+ * Implements the header_lowercase transform keyword with option support
+ */
+
+#include "suricata-common.h"
+#include "detect.h"
+#include "detect-engine.h"
+#include "detect-parse.h"
+#include "detect-transform-header-lowercase.h"
+
+/**
+ *  \internal
+ *  \brief Apply the header_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 DetectTransformHeaderLowercaseSetup(
+        DetectEngineCtx *de_ctx, Signature *s, const char *optstr)
+{
+    SCEnter();
+    int r = DetectSignatureAddTransform(s, DETECT_TRANSFORM_HEADER_LOWERCASE, NULL);
+    SCReturnInt(r);
+}
+
+static void DetectTransformHeaderLowercase(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];
+
+    // state 0 is header name, 1 is header value
+    int state = 0;
+    for (uint32_t i = 0; i < input_len; i++) {
+        if (state == 0) {
+            if (input[i] == ':') {
+                output[i] = input[i];
+                state = 1;
+            } else {
+                output[i] = u8_tolower(input[i]);
+            }
+        } else {
+            output[i] = input[i];
+            if (input[i] == '\n') {
+                state = 0;
+            }
+        }
+    }
+    InspectionBufferCopy(buffer, output, input_len);
+}
+
+void DetectTransformHeaderLowercaseRegister(void)
+{
+    sigmatch_table[DETECT_TRANSFORM_HEADER_LOWERCASE].name = "header_lowercase";
+    sigmatch_table[DETECT_TRANSFORM_HEADER_LOWERCASE].desc =
+            "modify buffer via lowercaseing header names";
+    sigmatch_table[DETECT_TRANSFORM_HEADER_LOWERCASE].url =
+            "/rules/transforms.html#header_lowercase";
+    sigmatch_table[DETECT_TRANSFORM_HEADER_LOWERCASE].Transform = DetectTransformHeaderLowercase;
+    sigmatch_table[DETECT_TRANSFORM_HEADER_LOWERCASE].Setup = DetectTransformHeaderLowercaseSetup;
+    sigmatch_table[DETECT_TRANSFORM_HEADER_LOWERCASE].flags |= SIGMATCH_NOOPT;
+}