/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 2013, Digium, Inc.
 *
 * Mark Michelson <mmichelson@digium.com>
 *
 * See http://www.asterisk.org for more information about
 * the Asterisk project. Please do not directly contact
 * any of the maintainers of this project for assistance;
 * the project provides a web site, mailing lists and IRC
 * channels for your use.
 *
 * This program is free software, distributed under the terms of
 * the GNU General Public License Version 2. See the LICENSE file
 * at the top of the source tree.
 */

/*** MODULEINFO
	<depend>pjproject</depend>
	<depend>res_pjsip</depend>
	<support_level>core</support_level>
 ***/

#include "asterisk.h"

#include <pjsip.h>

#include "asterisk/res_pjsip.h"
#include "asterisk/res_pjsip_cli.h"
#include "asterisk/module.h"
#include "asterisk/acl.h"
#include "asterisk/manager.h"
#include "res_pjsip/include/res_pjsip_private.h"

/*** DOCUMENTATION
	<configInfo name="res_pjsip_endpoint_identifier_ip" language="en_US">
		<synopsis>Module that identifies endpoints via source IP address</synopsis>
		<configFile name="pjsip.conf">
			<configObject name="identify">
				<synopsis>Identifies endpoints via source IP address</synopsis>
				<configOption name="endpoint">
					<synopsis>Name of Endpoint</synopsis>
				</configOption>
				<configOption name="match">
					<synopsis>IP addresses or networks to match against</synopsis>
					<description><para>
						The value is a comma-delimited list of IP addresses. IP addresses may
						have a subnet mask appended. The subnet mask may be written in either
						CIDR or dot-decimal notation. Separate the IP address and subnet
						mask with a slash ('/')
					</para></description>
				</configOption>
				<configOption name="srv_lookups" default="yes">
					<synopsis>Perform SRV lookups for provided hostnames.</synopsis>
					<description><para>When enabled, <replaceable>srv_lookups</replaceable> will
					perform SRV lookups for _sip._udp, _sip._tcp, and _sips._tcp of the given
					hostnames to determine additional addresses that traffic may originate from.
					</para></description>
                                </configOption>
				<configOption name="type">
					<synopsis>Must be of type 'identify'.</synopsis>
				</configOption>
			</configObject>
		</configFile>
	</configInfo>
 ***/

/*! \brief The number of buckets for storing hosts for resolution */
#define HOSTS_BUCKETS 53

/*! \brief Structure for an IP identification matching object */
struct ip_identify_match {
	/*! \brief Sorcery object details */
	SORCERY_OBJECT(details);
	/*! \brief Stringfields */
	AST_DECLARE_STRING_FIELDS(
		/*! The name of the endpoint */
		AST_STRING_FIELD(endpoint_name);
	);
	/*! \brief Networks or addresses that should match this */
	struct ast_ha *matches;
	/*! \brief Perform SRV resolution of hostnames */
	unsigned int srv_lookups;
	/*! \brief Hosts to be resolved after applying configuration */
	struct ao2_container *hosts;
};

/*! \brief Destructor function for a matching object */
static void ip_identify_destroy(void *obj)
{
	struct ip_identify_match *identify = obj;

	ast_string_field_free_memory(identify);
	ast_free_ha(identify->matches);
	ao2_cleanup(identify->hosts);
}

/*! \brief Allocator function for a matching object */
static void *ip_identify_alloc(const char *name)
{
	struct ip_identify_match *identify = ast_sorcery_generic_alloc(sizeof(*identify), ip_identify_destroy);

	if (!identify || ast_string_field_init(identify, 256)) {
		ao2_cleanup(identify);
		return NULL;
	}

	return identify;
}

/*! \brief Comparator function for a matching object */
static int ip_identify_match_check(void *obj, void *arg, int flags)
{
	struct ip_identify_match *identify = obj;
	struct ast_sockaddr *addr = arg;
	int sense;

	sense = ast_apply_ha(identify->matches, addr);
	if (sense != AST_SENSE_ALLOW) {
		ast_debug(3, "Source address %s matches identify '%s'\n",
				ast_sockaddr_stringify(addr),
				ast_sorcery_object_get_id(identify));
		return CMP_MATCH | CMP_STOP;
	} else {
		ast_debug(3, "Source address %s does not match identify '%s'\n",
				ast_sockaddr_stringify(addr),
				ast_sorcery_object_get_id(identify));
		return 0;
	}
}

static struct ast_sip_endpoint *ip_identify(pjsip_rx_data *rdata)
{
	struct ast_sockaddr addr = { { 0, } };
	RAII_VAR(struct ao2_container *, candidates, NULL, ao2_cleanup);
	RAII_VAR(struct ip_identify_match *, match, NULL, ao2_cleanup);
	struct ast_sip_endpoint *endpoint;

	/* If no possibilities exist return early to save some time */
	if (!(candidates = ast_sorcery_retrieve_by_fields(ast_sip_get_sorcery(), "identify", AST_RETRIEVE_FLAG_MULTIPLE | AST_RETRIEVE_FLAG_ALL, NULL)) ||
		!ao2_container_count(candidates)) {
		ast_debug(3, "No identify sections to match against\n");
		return NULL;
	}

	ast_sockaddr_parse(&addr, rdata->pkt_info.src_name, PARSE_PORT_FORBID);
	ast_sockaddr_set_port(&addr, rdata->pkt_info.src_port);

	if (!(match = ao2_callback(candidates, 0, ip_identify_match_check, &addr))) {
		ast_debug(3, "'%s' did not match any identify section rules\n",
				ast_sockaddr_stringify(&addr));
		return NULL;
	}

	endpoint = ast_sorcery_retrieve_by_id(ast_sip_get_sorcery(), "endpoint", match->endpoint_name);
	if (endpoint) {
		ast_debug(3, "Retrieved endpoint %s\n", ast_sorcery_object_get_id(endpoint));
	} else {
		ast_log(LOG_WARNING, "Identify section '%s' points to endpoint '%s' but endpoint could not be looked up\n",
				ast_sorcery_object_get_id(match), match->endpoint_name);
	}

	return endpoint;
}

static struct ast_sip_endpoint_identifier ip_identifier = {
	.identify_endpoint = ip_identify,
};

/*! \brief Helper function which performs a host lookup and adds result to identify match */
static int ip_identify_match_host_lookup(struct ip_identify_match *identify, const char *host)
{
	struct ast_sockaddr *addrs;
	int num_addrs = 0, error = 0, i;
	int results = 0;

	num_addrs = ast_sockaddr_resolve(&addrs, host, PARSE_PORT_FORBID, AST_AF_UNSPEC);
	if (!num_addrs) {
		return -1;
	}

	for (i = 0; i < num_addrs; ++i) {
		/* Check if the address is already in the list, if so don't bother adding it again */
		if (identify->matches && (ast_apply_ha(identify->matches, &addrs[i]) != AST_SENSE_ALLOW)) {
			continue;
		}

		/* We deny what we actually want to match because there is an implicit permit all rule for ACLs */
		identify->matches = ast_append_ha("d", ast_sockaddr_stringify_addr(&addrs[i]), identify->matches, &error);

		if (!identify->matches || error) {
			results = -1;
			break;
		}

		results += 1;
	}

	ast_free(addrs);

	return results;
}

/*! \brief Helper function which performs an SRV lookup and then resolves the hostname */
static int ip_identify_match_srv_lookup(struct ip_identify_match *identify, const char *prefix, const char *host)
{
	char service[NI_MAXHOST];
	struct srv_context *context = NULL;
	int srv_ret;
	const char *srvhost;
	unsigned short srvport;
	int results = 0;

	snprintf(service, sizeof(service), "%s.%s", prefix, host);

	while (!(srv_ret = ast_srv_lookup(&context, service, &srvhost, &srvport))) {
		int hosts;

		/* In the case of the SRV lookup we don't care if it fails, we will output a log message
		 * when we fallback to a normal lookup.
		 */
		hosts = ip_identify_match_host_lookup(identify, srvhost);
		if (hosts == -1) {
			results = -1;
			break;
		} else {
			results += hosts;
		}
	}

	ast_srv_cleanup(&context);

	return results;
}

/*! \brief Custom handler for match field */
static int ip_identify_match_handler(const struct aco_option *opt, struct ast_variable *var, void *obj)
{
	struct ip_identify_match *identify = obj;
	char *input_string = ast_strdupa(var->value);
	char *current_string;

	if (ast_strlen_zero(var->value)) {
		return 0;
	}

	while ((current_string = ast_strip(strsep(&input_string, ",")))) {
		char *mask = strrchr(current_string, '/');
		int error = 0;

		if (ast_strlen_zero(current_string)) {
			continue;
		}

		if (mask) {
			identify->matches = ast_append_ha("d", current_string, identify->matches, &error);

			if (!identify->matches || error) {
				ast_log(LOG_ERROR, "Failed to add address '%s' to ip endpoint identifier '%s'\n",
					current_string, ast_sorcery_object_get_id(obj));
				return -1;
			}

			continue;
		}

		if (!identify->hosts) {
			identify->hosts = ast_str_container_alloc_options(AO2_ALLOC_OPT_LOCK_NOLOCK, HOSTS_BUCKETS);
			if (!identify->hosts) {
				ast_log(LOG_ERROR, "Failed to create container to store hosts on ip endpoint identifier '%s'\n",
					ast_sorcery_object_get_id(obj));
				return -1;
			}
		}

		error = ast_str_container_add(identify->hosts, current_string);
		if (error) {
			ast_log(LOG_ERROR, "Failed to store host '%s' for resolution on ip endpoint identifier '%s'\n",
				current_string, ast_sorcery_object_get_id(obj));
			return -1;
		}
	}

	return 0;
}

/*! \brief Apply handler for identify type */
static int ip_identify_apply(const struct ast_sorcery *sorcery, void *obj)
{
	struct ip_identify_match *identify = obj;
	char *current_string;
	struct ao2_iterator i;

	if (!identify->hosts) {
		return 0;
	}

	i = ao2_iterator_init(identify->hosts, 0);
	while ((current_string = ao2_iterator_next(&i))) {
		struct ast_sockaddr address;
		int results = 0;

		/* If the provided string is not an IP address perform SRV resolution on it */
		if (identify->srv_lookups && !ast_sockaddr_parse(&address, current_string, 0)) {
			results = ip_identify_match_srv_lookup(identify, "_sip._udp", current_string);
			if (results != -1) {
				results += ip_identify_match_srv_lookup(identify, "_sip._tcp", current_string);
			}
			if (results != -1) {
				results += ip_identify_match_srv_lookup(identify, "_sips._tcp", current_string);
			}
		}

		/* If SRV falls fall back to a normal lookup on the host itself */
		if (!results) {
			results = ip_identify_match_host_lookup(identify, current_string);
		}

		if (results == 0) {
			ast_log(LOG_ERROR, "Address '%s' provided on ip endpoint identifier '%s' did not resolve to any address\n",
				current_string, ast_sorcery_object_get_id(obj));
		} else if (results == -1) {
			ast_log(LOG_ERROR, "An error occurred when adding resolution results of '%s' on '%s'\n",
				current_string, ast_sorcery_object_get_id(obj));
			ao2_ref(current_string, -1);
			ao2_iterator_destroy(&i);
			return -1;
		}

		ao2_ref(current_string, -1);
	}
	ao2_iterator_destroy(&i);

	ao2_ref(identify->hosts, -1);
	identify->hosts = NULL;

	return 0;
}

static int match_to_str(const void *obj, const intptr_t *args, char **buf)
{
	RAII_VAR(struct ast_str *, str, ast_str_create(MAX_OBJECT_FIELD), ast_free);
	const struct ip_identify_match *identify = obj;

	ast_ha_join(identify->matches, &str);
	*buf = ast_strdup(ast_str_buffer(str));
	return 0;
}

static int match_to_var_list(const void *obj, struct ast_variable **fields)
{
	char str[MAX_OBJECT_FIELD];
	const struct ip_identify_match *identify = obj;
	struct ast_variable *head = NULL;
	struct ast_ha *ha = identify->matches;

	for (; ha; ha = ha->next) {
		const char *addr = ast_strdupa(ast_sockaddr_stringify_addr(&ha->addr));
		snprintf(str, MAX_OBJECT_FIELD, "%s%s/%s", ha->sense == AST_SENSE_ALLOW ? "!" : "",
			addr, ast_sockaddr_stringify_addr(&ha->netmask));

		ast_variable_list_append(&head, ast_variable_new("match", str, ""));

	}

	if (head) {
		*fields = head;
	}

	return 0;
}

static int sip_identify_to_ami(const struct ip_identify_match *identify,
			       struct ast_str **buf)
{
	return ast_sip_sorcery_object_to_ami(identify, buf);
}

static int find_identify_by_endpoint(void *obj, void *arg, int flags)
{
	struct ip_identify_match *identify = obj;
	const char *endpoint_name = arg;

	return strcmp(identify->endpoint_name, endpoint_name) ? 0 : CMP_MATCH;
}

static int format_ami_endpoint_identify(const struct ast_sip_endpoint *endpoint,
					struct ast_sip_ami *ami)
{
	RAII_VAR(struct ao2_container *, identifies, NULL, ao2_cleanup);
	RAII_VAR(struct ip_identify_match *, identify, NULL, ao2_cleanup);
	RAII_VAR(struct ast_str *, buf, NULL, ast_free);

	identifies = ast_sorcery_retrieve_by_fields(ast_sip_get_sorcery(), "identify",
		AST_RETRIEVE_FLAG_MULTIPLE | AST_RETRIEVE_FLAG_ALL, NULL);
	if (!identifies) {
		return -1;
	}

	identify = ao2_callback(identifies, 0, find_identify_by_endpoint,
		(void *) ast_sorcery_object_get_id(endpoint));
	if (!identify) {
		return 1;
	}

	if (!(buf = ast_sip_create_ami_event("IdentifyDetail", ami))) {
		return -1;
	}

	if (sip_identify_to_ami(identify, &buf)) {
		return -1;
	}

	ast_str_append(&buf, 0, "EndpointName: %s\r\n",
		ast_sorcery_object_get_id(endpoint));

	astman_append(ami->s, "%s\r\n", ast_str_buffer(buf));
	ami->count++;

	return 0;
}

struct ast_sip_endpoint_formatter endpoint_identify_formatter = {
	.format_ami = format_ami_endpoint_identify
};

static int cli_iterator(void *container, ao2_callback_fn callback, void *args)
{
	const struct ast_sip_endpoint *endpoint = container;
	struct ao2_container *identifies;

	struct ast_variable fields = {
		.name = "endpoint",
		.value = ast_sorcery_object_get_id(endpoint),
		.next = NULL,
	};

	identifies = ast_sorcery_retrieve_by_fields(ast_sip_get_sorcery(), "identify",
		AST_RETRIEVE_FLAG_MULTIPLE, &fields);
	if (!identifies) {
		return -1;
	}

	ao2_callback(identifies, OBJ_NODATA, callback, args);
	ao2_cleanup(identifies);

	return 0;
}

static struct ao2_container *cli_get_container(const char *regex)
{
	RAII_VAR(struct ao2_container *, container, NULL, ao2_cleanup);
	struct ao2_container *s_container;

	container =  ast_sorcery_retrieve_by_regex(ast_sip_get_sorcery(), "identify", regex);
	if (!container) {
		return NULL;
	}

	s_container = ao2_container_alloc_list(AO2_ALLOC_OPT_LOCK_NOLOCK, 0,
		ast_sorcery_object_id_sort, ast_sorcery_object_id_compare);
	if (!s_container) {
		return NULL;
	}

	if (ao2_container_dup(s_container, container, 0)) {
		ao2_ref(s_container, -1);
		return NULL;
	}

	return s_container;
}

static void *cli_retrieve_by_id(const char *id)
{
	return ast_sorcery_retrieve_by_id(ast_sip_get_sorcery(), "identify", id);
}

static int cli_print_header(void *obj, void *arg, int flags)
{
	struct ast_sip_cli_context *context = arg;
	int indent = CLI_INDENT_TO_SPACES(context->indent_level);
	int filler = CLI_MAX_WIDTH - indent - 22;

	ast_assert(context->output_buffer != NULL);

	ast_str_append(&context->output_buffer, 0,
		"%*s:  <Identify/Endpoint%*.*s>\n",
		indent, "Identify", filler, filler, CLI_HEADER_FILLER);

	if (context->recurse) {
		context->indent_level++;
		indent = CLI_INDENT_TO_SPACES(context->indent_level);
		filler = CLI_LAST_TABSTOP - indent - 24;

		ast_str_append(&context->output_buffer, 0,
			"%*s:  <ip/cidr%*.*s>\n",
			indent, "Match", filler, filler, CLI_HEADER_FILLER);

		context->indent_level--;
	}

	return 0;
}

static int cli_print_body(void *obj, void *arg, int flags)
{
	RAII_VAR(struct ast_str *, str, ast_str_create(MAX_OBJECT_FIELD), ast_free);
	struct ip_identify_match *ident = obj;
	struct ast_sip_cli_context *context = arg;
	struct ast_ha *match;
	int indent;

	ast_assert(context->output_buffer != NULL);

	ast_str_append(&context->output_buffer, 0, "%*s:  %s/%s\n",
		CLI_INDENT_TO_SPACES(context->indent_level), "Identify",
		ast_sorcery_object_get_id(ident), ident->endpoint_name);

	if (context->recurse) {
		context->indent_level++;
		indent = CLI_INDENT_TO_SPACES(context->indent_level);

		for (match = ident->matches; match; match = match->next) {
			const char *addr = ast_sockaddr_stringify_addr(&match->addr);

			ast_str_append(&context->output_buffer, 0, "%*s: %s%s/%d\n",
				indent,
				"Match",
				match->sense == AST_SENSE_ALLOW ? "!" : "",
				addr, ast_sockaddr_cidr_bits(&match->netmask));
		}

		context->indent_level--;

		if (context->indent_level == 0) {
			ast_str_append(&context->output_buffer, 0, "\n");
		}
	}

	if (context->show_details
		|| (context->show_details_only_level_0 && context->indent_level == 0)) {
		ast_str_append(&context->output_buffer, 0, "\n");
		ast_sip_cli_print_sorcery_objectset(ident, context, 0);
	}

	return 0;
}

/*
 * A function pointer to callback needs to be within the
 * module in order to avoid problems with an undefined
 * symbol when the module is loaded.
 */
static char *my_cli_traverse_objects(struct ast_cli_entry *e, int cmd,
	struct ast_cli_args *a)
{
	return ast_sip_cli_traverse_objects(e, cmd, a);
}

static struct ast_cli_entry cli_identify[] = {
AST_CLI_DEFINE(my_cli_traverse_objects, "List PJSIP Identifies",
	.command = "pjsip list identifies",
	.usage = "Usage: pjsip list identifies [ like <pattern> ]\n"
	"       List the configured PJSIP Identifies\n"
	"       Optional regular expression pattern is used to filter the list.\n"),
AST_CLI_DEFINE(my_cli_traverse_objects, "Show PJSIP Identifies",
	.command = "pjsip show identifies",
	.usage = "Usage: pjsip show identifies [ like <pattern> ]\n"
	"       Show the configured PJSIP Identifies\n"
	"       Optional regular expression pattern is used to filter the list.\n"),
AST_CLI_DEFINE(my_cli_traverse_objects, "Show PJSIP Identify",
	.command = "pjsip show identify",
	.usage = "Usage: pjsip show identify <id>\n"
	"       Show the configured PJSIP Identify\n"),
};

static struct ast_sip_cli_formatter_entry *cli_formatter;

static int load_module(void)
{
	CHECK_PJSIP_MODULE_LOADED();

	ast_sorcery_apply_config(ast_sip_get_sorcery(), "res_pjsip_endpoint_identifier_ip");
	ast_sorcery_apply_default(ast_sip_get_sorcery(), "identify", "config", "pjsip.conf,criteria=type=identify");

	if (ast_sorcery_object_register(ast_sip_get_sorcery(), "identify", ip_identify_alloc, NULL, ip_identify_apply)) {
		return AST_MODULE_LOAD_DECLINE;
	}

	ast_sorcery_object_field_register(ast_sip_get_sorcery(), "identify", "type", "", OPT_NOOP_T, 0, 0);
	ast_sorcery_object_field_register(ast_sip_get_sorcery(), "identify", "endpoint", "", OPT_STRINGFIELD_T, 0, STRFLDSET(struct ip_identify_match, endpoint_name));
	ast_sorcery_object_field_register_custom(ast_sip_get_sorcery(), "identify", "match", "", ip_identify_match_handler, match_to_str, match_to_var_list, 0, 0);
	ast_sorcery_object_field_register(ast_sip_get_sorcery(), "identify", "srv_lookups", "yes", OPT_BOOL_T, 1, FLDSET(struct ip_identify_match, srv_lookups));
	ast_sorcery_load_object(ast_sip_get_sorcery(), "identify");

	ast_sip_register_endpoint_identifier_with_name(&ip_identifier, "ip");
	ast_sip_register_endpoint_formatter(&endpoint_identify_formatter);

	cli_formatter = ao2_alloc(sizeof(struct ast_sip_cli_formatter_entry), NULL);
	if (!cli_formatter) {
		ast_log(LOG_ERROR, "Unable to allocate memory for cli formatter\n");
		return AST_MODULE_LOAD_DECLINE;
	}
	cli_formatter->name = "identify";
	cli_formatter->print_header = cli_print_header;
	cli_formatter->print_body = cli_print_body;
	cli_formatter->get_container = cli_get_container;
	cli_formatter->iterate = cli_iterator;
	cli_formatter->get_id = ast_sorcery_object_get_id;
	cli_formatter->retrieve_by_id = cli_retrieve_by_id;

	ast_sip_register_cli_formatter(cli_formatter);
	ast_cli_register_multiple(cli_identify, ARRAY_LEN(cli_identify));

	return AST_MODULE_LOAD_SUCCESS;
}

static int reload_module(void)
{
	ast_sorcery_reload_object(ast_sip_get_sorcery(), "identify");

	return 0;
}

static int unload_module(void)
{
	ast_cli_unregister_multiple(cli_identify, ARRAY_LEN(cli_identify));
	ast_sip_unregister_cli_formatter(cli_formatter);
	ast_sip_unregister_endpoint_formatter(&endpoint_identify_formatter);
	ast_sip_unregister_endpoint_identifier(&ip_identifier);

	return 0;
}

AST_MODULE_INFO(ASTERISK_GPL_KEY, AST_MODFLAG_LOAD_ORDER, "PJSIP IP endpoint identifier",
		.support_level = AST_MODULE_SUPPORT_CORE,
		.load = load_module,
		.reload = reload_module,
		.unload = unload_module,
		.load_pri = AST_MODPRI_CHANNEL_DEPEND - 4,
	       );
