imap: extend detection patterns

Ticket: OISF#2886

Signed-off-by: mmaatuq <mahmoudmatook.mm@gmail.com>

src/Makefile.am

@@ -45,6 +45,7 @@ noinst_HEADERS = \
 	app-layer-ssh.h \
 	app-layer-ssl.h \
 	app-layer-tftp.h \
+	app-layer-imap.h \
 	build-info.h \
 	conf.h \
 	conf-yaml-loader.h \
@@ -658,6 +659,7 @@ libsuricata_c_a_SOURCES = \
 	app-layer-ssh.c \
 	app-layer-ssl.c \
 	app-layer-tftp.c \
+	app-layer-imap.c \
 	conf.c \
 	conf-yaml-loader.c \
 	counters.c \

src/app-layer-imap.c

@@ -0,0 +1,96 @@
+/* Copyright (C) 2024 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 Mahmoud Maatuq <mahmoudmatook.mm@gmail.com>
+ *
+ */
+
+#include "app-layer.h"
+#include "app-layer-detect-proto.h"
+#include "app-layer-imap.h"
+
+static int IMAPRegisterPatternsForProtocolDetection(void)
+{
+    if (AppLayerProtoDetectPMRegisterPatternCI(
+                IPPROTO_TCP, ALPROTO_IMAP, "* OK ", 5, 0, STREAM_TOCLIENT) < 0) {
+        return -1;
+    }
+
+    if (AppLayerProtoDetectPMRegisterPatternCI(
+                IPPROTO_TCP, ALPROTO_IMAP, "* NO ", 5, 0, STREAM_TOCLIENT) < 0) {
+        return -1;
+    }
+
+    if (AppLayerProtoDetectPMRegisterPatternCI(
+                IPPROTO_TCP, ALPROTO_IMAP, "* BAD ", 6, 0, STREAM_TOCLIENT) < 0) {
+        return -1;
+    }
+
+    if (AppLayerProtoDetectPMRegisterPatternCI(
+                IPPROTO_TCP, ALPROTO_IMAP, "* LIST ", 7, 0, STREAM_TOCLIENT) < 0) {
+        return -1;
+    }
+
+    if (AppLayerProtoDetectPMRegisterPatternCI(
+                IPPROTO_TCP, ALPROTO_IMAP, "* ESEARCH ", 10, 0, STREAM_TOCLIENT) < 0) {
+        return -1;
+    }
+
+    if (AppLayerProtoDetectPMRegisterPatternCI(
+                IPPROTO_TCP, ALPROTO_IMAP, "* STATUS ", 9, 0, STREAM_TOCLIENT) < 0) {
+        return -1;
+    }
+
+    if (AppLayerProtoDetectPMRegisterPatternCI(
+                IPPROTO_TCP, ALPROTO_IMAP, "* FLAGS ", 8, 0, STREAM_TOCLIENT) < 0) {
+        return -1;
+    }
+
+    /**
+     * there is no official document that limits the length of the tag
+     * some practical implementations limit it to 20 characters
+     * but keeping depth equal to 31 fails unit tests such  AppLayerTest10
+     * so keeping depth 17 for now to pass unit tests, that might miss some detections
+     * until we find a better solution for the unit tests.
+     *
+     * AppLayerTest10 fails because it expects protocol detection to be completed with only 17 bytes
+     * as input, and with this new pattern, we would need more bytes to finish protocol detection.
+     */
+    if (AppLayerProtoDetectPMRegisterPatternCI(IPPROTO_TCP, ALPROTO_IMAP, " CAPABILITY",
+                17 /*6 for max tag len + space + len(CAPABILITY)*/, 0, STREAM_TOSERVER) < 0) {
+        return -1;
+    }
+
+    return 0;
+}
+
+void RegisterIMAPParsers(void)
+{
+    const char *proto_name = "imap";
+
+    if (AppLayerProtoDetectConfProtoDetectionEnabled("tcp", proto_name)) {
+        SCLogDebug("IMAP protocol detection is enabled.");
+        AppLayerProtoDetectRegisterProtocol(ALPROTO_IMAP, proto_name);
+        if (IMAPRegisterPatternsForProtocolDetection() < 0)
+            SCLogError("Failed to register IMAP protocol detection patterns.");
+    } else {
+        SCLogDebug("Protocol detector and parser disabled for IMAP.");
+    }
+}

src/app-layer-imap.h

@@ -0,0 +1,28 @@
+/* Copyright (C) 2024 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 Mahmoud Maatuq <mahmoudmatook.mm@gmail.com>
+ *
+ */
+
+#ifndef SURICATA_APP_LAYER_IMAP_H
+#define SURICATA_APP_LAYER_IMAP_H
+void RegisterIMAPParsers(void);
+#endif

src/app-layer-parser.c

@@ -55,6 +55,7 @@
 #include "app-layer-ike.h"
 #include "app-layer-rfb.h"
 #include "app-layer-http2.h"
+#include "app-layer-imap.h"
 
 struct AppLayerParserThreadCtx_ {
     void *alproto_local_storage[FLOW_PROTO_MAX][ALPROTO_MAX];
@@ -1755,19 +1756,7 @@ void AppLayerParserRegisterProtocolParsers(void)
     rs_rdp_register_parser();
     RegisterHTTP2Parsers();
     rs_telnet_register_parser();
-
-    /** IMAP */
-    AppLayerProtoDetectRegisterProtocol(ALPROTO_IMAP, "imap");
-    if (AppLayerProtoDetectConfProtoDetectionEnabled("tcp", "imap")) {
-        if (AppLayerProtoDetectPMRegisterPatternCS(IPPROTO_TCP, ALPROTO_IMAP,
-                                  "1|20|capability", 12, 0, STREAM_TOSERVER) < 0)
-        {
-            FatalError("imap proto registration failure");
-        }
-    } else {
-        SCLogInfo("Protocol detection and parser disabled for %s protocol.",
-                  "imap");
-    }
+    RegisterIMAPParsers();
 
     /** POP3 */
     AppLayerProtoDetectRegisterProtocol(ALPROTO_POP3, "pop3");