add example plugin that jails clients

Signed-off-by: Abilio Marques <abiliojr@gmail.com>

plugins/examples/CMakeLists.txt

@@ -17,4 +17,5 @@ add_subdirectory(payload-size-stats)
 add_subdirectory(plugin-event-stats)
 add_subdirectory(print-ip-on-publish)
 add_subdirectory(topic-modification)
+add_subdirectory(topic-jail)
 add_subdirectory(wildcard-temp)

plugins/examples/Makefile

@@ -16,6 +16,7 @@ DIRS= \
 		plugin-event-stats \
 		print-ip-on-publish \
 		topic-modification \
+		topic-jail \
 		wildcard-temp
 
 .PHONY : all binary check clean reallyclean test test-compile install uninstall

plugins/examples/topic-jail/CMakeLists.txt

@@ -0,0 +1,26 @@
+set (PLUGIN_NAME mosquitto_topic_jail)
+
+add_library(${PLUGIN_NAME} MODULE
+	${PLUGIN_NAME}.c
+)
+
+target_include_directories(${PLUGIN_NAME} PRIVATE
+	"${OPENSSL_INCLUDE_DIR}"
+	"${STDBOOL_H_PATH}"
+	"${STDINT_H_PATH}"
+	"${mosquitto_SOURCE_DIR}"
+	"${mosquitto_SOURCE_DIR}/include"
+)
+
+link_directories(${mosquitto_SOURCE_DIR})
+
+set_target_properties(${PLUGIN_NAME} PROPERTIES
+	PREFIX ""
+	POSITION_INDEPENDENT_CODE 1
+)
+if(WIN32)
+	target_link_libraries(${PLUGIN_NAME} mosquitto)
+endif()
+
+# Don't install, these are example plugins only.
+#install(TARGETS ${PLUGIN_NAME} RUNTIME DESTINATION "${CMAKE_INSTALL_BINDIR}" LIBRARY DESTINATION "${CMAKE_INSTALL_LIBDIR}")

plugins/examples/topic-jail/Makefile

@@ -0,0 +1,29 @@
+R=../../..
+include ${R}/config.mk
+
+.PHONY : all binary check clean reallyclean test install uninstall
+
+PLUGIN_NAME=mosquitto_topic_jail
+PLUGIN_CFLAGS+=-I${R}/include -I${R}/
+
+all : binary
+
+binary : ${PLUGIN_NAME}.so
+
+${PLUGIN_NAME}.so : ${PLUGIN_NAME}.c
+	$(CROSS_COMPILE)$(CC) $(PLUGIN_CPPFLAGS) $(PLUGIN_CFLAGS) $(PLUGIN_LDFLAGS) -fPIC -shared $< -o $@
+
+reallyclean : clean
+clean:
+	-rm -f *.o ${PLUGIN_NAME}.so *.gcda *.gcno
+
+check: test
+test:
+
+install: ${PLUGIN_NAME}.so
+	# Don't install, these are examples only.
+	#$(INSTALL) -d "${DESTDIR}$(libdir)"
+	#$(INSTALL) ${STRIP_OPTS} ${PLUGIN_NAME}.so "${DESTDIR}${libdir}/${PLUGIN_NAME}.so"
+
+uninstall :
+	-rm -f "${DESTDIR}${libdir}/${PLUGIN_NAME}.so"

plugins/examples/topic-jail/mosquitto_topic_jail.c

@@ -0,0 +1,257 @@
+/*
+Copyright (c) 2020-2021 Roger Light <roger@atchoo.org>
+
+All rights reserved. This program and the accompanying materials
+are made available under the terms of the Eclipse Public License 2.0
+and Eclipse Distribution License v1.0 which accompany this distribution.
+
+The Eclipse Public License is available at
+   https://www.eclipse.org/legal/epl-2.0/
+and the Eclipse Distribution License is available at
+  http://www.eclipse.org/org/documents/edl-v10.php.
+
+SPDX-License-Identifier: EPL-2.0 OR BSD-3-Clause
+
+Contributors:
+   Abilio Marques - initial implementation and documentation.
+*/
+
+/*
+ * This is an *example* plugin which demonstrates how to jail a client.
+ * It mounts such client topics in a subtree starting with the client id.
+ * It modifies it's subscriptions and the topics of the messages destined to
+ * that client. It also modifies the topics of the messages published
+ * by the client.
+ *
+ *  client | event | destination | original topic       | modified topic
+ *  -------|-------|-------------|----------------------|--------------------
+ *  jailed |  sub  |     ---     | topic                | ${jailed_id}/topic
+ *  normal |  pub  |   jailed    | ${jailed_id}/topic   | topic
+ *  jailed |  pub  |   normal    | topic                | ${jailed_id}/topic
+ *
+ * For simplicity of this example, all clients with id starting with "jailed"
+ * will be jailed. All other clients will work as normal.
+ * 
+ * Two jailed clients cannot interact with each other. Normal clients can interact
+ * with any jailed client by publishing or subscribing to the mounted topic.
+ *
+ * You should be very sure of what you are doing before making use of this feature.
+ *
+ * Compile with:
+ *   gcc -I<path to mosquitto-repo/include> -fPIC -shared mosquitto_topic_jail.c -o mosquitto_topic_jail.so
+ *
+ * Use in config with:
+ *
+ *   plugin /path/to/mosquitto_topic_jail.so
+ *
+ * Note that this only works on Mosquitto 2.0 or later.
+ */
+#include <stdio.h>
+#include <string.h>
+
+#include "mosquitto_broker.h"
+#include "mosquitto_plugin.h"
+#include "mosquitto.h"
+#include "mqtt_protocol.h"
+
+#define PLUGIN_NAME "topic-jail"
+#define PLUGIN_VERSION "1.0"
+
+#define UNUSED(A) (void)(A)
+
+MOSQUITTO_PLUGIN_DECLARE_VERSION(5);
+
+static mosquitto_plugin_id_t *mosq_pid = NULL;
+
+static bool is_jailed(const char *str)
+{
+	return strncmp("jailed", str, 6) == 0;
+}
+
+
+static int callback_message_write(int event, void *event_data, void *userdata)
+{
+	struct mosquitto_evt_message *ed = event_data;
+	char *new_topic;
+	size_t new_topic_len;
+
+	UNUSED(event);
+	UNUSED(userdata);
+
+	const char *client_id = mosquitto_client_id(ed->client);
+
+	if(!is_jailed(client_id)){
+		/* will only modify the topic of jailed clients */
+		return MOSQ_ERR_SUCCESS;
+	}
+
+	/* put the client_id on front of the topic */
+
+	/* calculate the length of the new payload */
+	new_topic_len = strlen(client_id) + sizeof('/') + strlen(ed->topic) + 1;
+
+	/* Allocate some memory - use
+	 * mosquitto_calloc/mosquitto_malloc/mosquitto_strdup when allocating, to
+	 * allow the broker to track memory usage */
+	new_topic = mosquitto_calloc(1, new_topic_len);
+	if(new_topic == NULL){
+		return MOSQ_ERR_NOMEM;
+	}
+
+	/* prepend the client_id to the topic */
+	snprintf(new_topic, new_topic_len, "%s/%s", client_id, ed->topic);
+
+	/* Assign the new topic to the event data structure. You
+	 * must *not* free the original topic, it will be handled by the
+	 * broker. */
+	ed->topic = new_topic;
+
+	return MOSQ_ERR_SUCCESS;
+}
+
+static int callback_message_read(int event, void *event_data, void *userdata)
+{
+	struct mosquitto_evt_message *ed = event_data;
+	size_t client_id_len;
+
+	UNUSED(event);
+	UNUSED(userdata);
+
+	const char *client_id = mosquitto_client_id(ed->client);
+
+	if(!is_jailed(client_id)){
+		/* will only modify the topic of jailed clients */
+		return MOSQ_ERR_SUCCESS;
+	}
+
+	/* remove the client_id from the front of the topic */
+	client_id_len = strlen(client_id);
+
+	if(strlen(ed->topic) <= client_id_len + 1){
+		/* the topic is not long enough to contain the
+		 * client_id + '/' */
+		return MOSQ_ERR_SUCCESS;
+	}
+
+	if(!strncmp(client_id, ed->topic, client_id_len) && ed->topic[client_id_len] == '/'){
+		/* Allocate some memory - use
+		 * mosquitto_calloc/mosquitto_malloc/mosquitto_strdup when allocating, to
+		 * allow the broker to track memory usage */
+
+		/* skip the client_id + '/' */
+		char *new_topic = mosquitto_strdup(ed->topic + client_id_len + 1);
+
+		if(new_topic == NULL){
+			return MOSQ_ERR_NOMEM;
+		}
+
+		/* Assign the new topic to the event data structure. You
+		 * must *not* free the original topic, it will be handled by the
+		 * broker. */
+		ed->topic = new_topic;
+	}
+
+	return MOSQ_ERR_SUCCESS;
+}
+
+static int callback_subscribe(int event, void *event_data, void *userdata)
+{
+	struct mosquitto_evt_subscribe *ed = event_data;
+	char *new_sub;
+	size_t new_sub_len;
+
+	UNUSED(event);
+	UNUSED(userdata);
+
+	const char *client_id = mosquitto_client_id(ed->client);
+
+	if(!is_jailed(client_id)){
+		/* will only modify the topic of jailed clients */
+		return MOSQ_ERR_SUCCESS;
+	}
+
+	/* put the client_id on front of the topic */
+
+	/* calculate the length of the new payload */
+	new_sub_len = strlen(client_id) + sizeof('/') + strlen(ed->topic) + 1;
+
+	/* Allocate some memory - use
+	 * mosquitto_calloc/mosquitto_malloc/mosquitto_strdup when allocating, to
+	 * allow the broker to track memory usage */
+	new_sub = mosquitto_calloc(1, new_sub_len);
+	if(new_sub == NULL){
+		return MOSQ_ERR_NOMEM;
+	}
+
+	/* prepend the client_id to the subscription */
+	snprintf(new_sub, new_sub_len, "%s/%s", client_id, ed->topic);
+
+	/* Assign the new topic to the event data structure. You
+	 * must *not* free the original topic, it will be handled by the
+	 * broker. */
+	ed->topic = new_sub;
+
+	return MOSQ_ERR_SUCCESS;
+}
+
+static int callback_unsubscribe(int event, void *event_data, void *userdata)
+{
+	struct mosquitto_evt_unsubscribe *ed = event_data;
+	char *new_sub;
+	size_t new_sub_len;
+
+	UNUSED(event);
+	UNUSED(userdata);
+
+	const char *client_id = mosquitto_client_id(ed->client);
+
+	if(!is_jailed(client_id)){
+		/* will only modify the topic of jailed clients */
+		return MOSQ_ERR_SUCCESS;
+	}
+
+	/* put the client_id on front of the topic */
+
+	/* calculate the length of the new payload */
+	new_sub_len = strlen(client_id) + sizeof('/') + strlen(ed->topic) + 1;
+
+	/* Allocate some memory - use
+	 * mosquitto_calloc/mosquitto_malloc/mosquitto_strdup when allocating, to
+	 * allow the broker to track memory usage */
+	new_sub = mosquitto_calloc(1, new_sub_len);
+	if(new_sub == NULL){
+		return MOSQ_ERR_NOMEM;
+	}
+
+	/* prepend the client_id to the subscription */
+	snprintf(new_sub, new_sub_len, "%s/%s", client_id, ed->topic);
+
+	/* Assign the new topic to the event data structure. You
+	 * must *not* free the original topic, it will be handled by the
+	 * broker. */
+	ed->topic = new_sub;
+
+	return MOSQ_ERR_SUCCESS;
+}
+
+
+int mosquitto_plugin_init(mosquitto_plugin_id_t *identifier, void **user_data, struct mosquitto_opt *opts, int opt_count)
+{
+	UNUSED(user_data);
+	UNUSED(opts);
+	UNUSED(opt_count);
+
+	mosq_pid = identifier;
+	mosquitto_plugin_set_info(identifier, PLUGIN_NAME, PLUGIN_VERSION);
+
+	int rc;
+
+	rc = mosquitto_callback_register(mosq_pid, MOSQ_EVT_MESSAGE_WRITE, callback_message_write, NULL, NULL);
+	if(rc) return rc;
+	rc = mosquitto_callback_register(mosq_pid, MOSQ_EVT_MESSAGE_READ, callback_message_read, NULL, NULL);
+	if(rc) return rc;
+	rc = mosquitto_callback_register(mosq_pid, MOSQ_EVT_SUBSCRIBE, callback_subscribe, NULL, NULL);
+	if(rc) return rc;
+	rc = mosquitto_callback_register(mosq_pid, MOSQ_EVT_UNSUBSCRIBE, callback_unsubscribe, NULL, NULL);
+	return rc;
+}

plugins/examples/topic-jail/test.conf

@@ -0,0 +1 @@
+plugin ./mosquitto_topic_jail.so

plugins/examples/topic-jail/test.sh

@@ -0,0 +1,3 @@
+#!/bin/sh
+
+../../../src/mosquitto -c test.conf -v