detect/ftp.command: Add sticky buffer

doc/userguide/rules/ftp-keywords.rst

@@ -44,4 +44,30 @@ Signature Example:
   :example-rule-options:`file.name; content:"file.txt";` \
   classtype:bad-unknown; sid:1; rev:1;)
 
-For additional information on the ``file.name`` keyword, see :doc:`file-keywords`.
+For additional information on the ``file.name`` keyword, see :doc:`file-keywords`.
+
+ftp.command
+-----------
+
+This keyword matches on the command name from a FTP client request. ``ftp.command``
+is a sticky buffer and can be used as a fast pattern.
+
+Syntax::
+
+  ftp.command; content: <command>;
+
+Signature Example:
+
+.. container:: example-rule
+
+  alert ftp any any -> any any (:example-rule-options:`ftp.command; content:"PASS";` sid: 1;)
+
+Examples of commands are:
+
+* USER
+* PASS
+* PORT
+* EPRT
+* PASV
+* RETR
+

src/Makefile.am

@@ -168,6 +168,7 @@ noinst_HEADERS = \
 	detect-frame.h \
 	detect-ftpbounce.h \
 	detect-ftpdata.h \
+	detect-ftp-command.h \
 	detect-geoip.h \
 	detect-gid.h \
 	detect.h \
@@ -737,6 +738,7 @@ libsuricata_c_a_SOURCES = \
 	detect-frame.c \
 	detect-ftpbounce.c \
 	detect-ftpdata.c \
+	detect-ftp-command.c \
 	detect-geoip.c \
 	detect-gid.c \
 	detect-hostbits.c \

src/detect-engine-register.c

@@ -210,6 +210,7 @@
 #include "detect-quic-cyu-hash.h"
 #include "detect-quic-cyu-string.h"
 #include "detect-ja4-hash.h"
+#include "detect-ftp-command.h"
 
 #include "detect-bypass.h"
 #include "detect-ftpdata.h"
@@ -706,6 +707,7 @@ void SigTableSetup(void)
     DetectQuicCyuHashRegister();
     DetectQuicCyuStringRegister();
     DetectJa4HashRegister();
+    DetectFtpCommandRegister();
 
     DetectBypassRegister();
     DetectConfigRegister();

src/detect-engine-register.h

@@ -333,6 +333,8 @@ enum DetectKeywordId {
 
     DETECT_JA4_HASH,
 
+    DETECT_FTP_COMMAND,
+
     DETECT_VLAN_ID,
     DETECT_VLAN_LAYERS,
 

src/detect-ftp-command.c

@@ -0,0 +1,103 @@
+/* Copyright (C) 2025 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.
+ */
+
+/**
+ *
+ * \author Jeff Lucovsky <[email protected]>
+ *
+ * Implements the ftp.command sticky buffer
+ *
+ */
+
+#include "suricata-common.h"
+#include "detect.h"
+
+#include "detect-parse.h"
+#include "detect-engine.h"
+#include "detect-engine-mpm.h"
+#include "detect-engine-prefilter.h"
+#include "detect-content.h"
+
+#include "flow.h"
+
+#include "util-debug.h"
+
+#include "app-layer.h"
+#include "app-layer-ftp.h"
+
+#include "detect-ftp-command.h"
+
+#define KEYWORD_NAME "ftp.command"
+#define KEYWORD_DOC  "ftp-keywords.html#ftp-command"
+#define BUFFER_NAME  "ftp.command"
+#define BUFFER_DESC  "ftp command"
+
+static int g_ftp_cmd_buffer_id = 0;
+
+static int DetectFtpCommandSetup(DetectEngineCtx *de_ctx, Signature *s, const char *str)
+{
+    if (DetectBufferSetActiveList(de_ctx, s, g_ftp_cmd_buffer_id) < 0)
+        return -1;
+
+    if (DetectSignatureSetAppProto(s, ALPROTO_FTP) < 0)
+        return -1;
+
+    return 0;
+}
+
+static InspectionBuffer *GetData(DetectEngineThreadCtx *det_ctx,
+        const DetectEngineTransforms *transforms, Flow *_f, const uint8_t _flow_flags, void *txv,
+        const int list_id)
+{
+    InspectionBuffer *buffer = InspectionBufferGet(det_ctx, list_id);
+    if (buffer->inspect == NULL) {
+        FTPTransaction *tx = (FTPTransaction *)txv;
+
+        if (tx->command_descriptor->command_name == NULL ||
+                tx->command_descriptor->command_length == 0)
+            return NULL;
+
+        InspectionBufferSetup(det_ctx, list_id, buffer,
+                (const uint8_t *)tx->command_descriptor->command_name,
+                tx->command_descriptor->command_length);
+        InspectionBufferApplyTransforms(buffer, transforms);
+    }
+
+    return buffer;
+}
+
+void DetectFtpCommandRegister(void)
+{
+    /* ftp.command sticky buffer */
+    sigmatch_table[DETECT_FTP_COMMAND].name = KEYWORD_NAME;
+    sigmatch_table[DETECT_FTP_COMMAND].desc = "sticky buffer to match on the FTP command buffer";
+    sigmatch_table[DETECT_FTP_COMMAND].url = "/rules/" KEYWORD_DOC;
+    sigmatch_table[DETECT_FTP_COMMAND].Setup = DetectFtpCommandSetup;
+    sigmatch_table[DETECT_FTP_COMMAND].flags |= SIGMATCH_NOOPT;
+
+    DetectAppLayerInspectEngineRegister(BUFFER_NAME, ALPROTO_FTP, SIG_FLAG_TOSERVER, 0,
+            DetectEngineInspectBufferGeneric, GetData);
+
+    DetectAppLayerMpmRegister(BUFFER_NAME, SIG_FLAG_TOSERVER, 2, PrefilterGenericMpmRegister,
+            GetData, ALPROTO_FTP, 1);
+
+    DetectBufferTypeSetDescriptionByName(BUFFER_NAME, BUFFER_DESC);
+
+    g_ftp_cmd_buffer_id = DetectBufferTypeGetByName(BUFFER_NAME);
+
+    SCLogDebug("registering " BUFFER_NAME " rule option");
+}

src/detect-ftp-command.h

@@ -0,0 +1,29 @@
+/* Copyright (C) 2025 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  <[email protected]>
+ */
+
+#ifndef SURICATA_DETECT_FTP_COMMAND_H
+#define SURICATA_DETECT_FTP_COMMAND_H
+
+void DetectFtpCommandRegister(void);
+
+#endif /* SURICATA_DETECT_FTP_COMMAND_H */