/* Copyright (c) 2002-2018 Dovecot authors, see the included COPYING file */

#include "pop3-common.h"
#include "ioloop.h"
#include "buffer.h"
#include "istream.h"
#include "istream-concat.h"
#include "ostream.h"
#include "path-util.h"
#include "base64.h"
#include "str.h"
#include "process-title.h"
#include "restrict-access.h"
#include "settings-parser.h"
#include "master-service.h"
#include "master-login.h"
#include "master-interface.h"
#include "var-expand.h"
#include "mail-error.h"
#include "mail-user.h"
#include "mail-namespace.h"
#include "mail-storage-service.h"

#include <stdio.h>
#include <unistd.h>

#define IS_STANDALONE() \
        (getenv(MASTER_IS_PARENT_ENV) == NULL)

static bool verbose_proctitle = FALSE;
static struct mail_storage_service_ctx *storage_service;
static struct master_login *master_login = NULL;

pop3_client_created_func_t *hook_client_created = NULL;

pop3_client_created_func_t *
pop3_client_created_hook_set(pop3_client_created_func_t *new_hook)
{
	pop3_client_created_func_t *old_hook = hook_client_created;

	hook_client_created = new_hook;
	return old_hook;
}

void pop3_refresh_proctitle(void)
{
	struct client *client;
	string_t *title = t_str_new(128);

	if (!verbose_proctitle)
		return;

	str_append_c(title, '[');
	switch (pop3_client_count) {
	case 0:
		str_append(title, "idling");
		break;
	case 1:
		client = pop3_clients;
		str_append(title, client->user->username);
		if (client->user->conn.remote_ip != NULL) {
			str_append_c(title, ' ');
			str_append(title,
				   net_ip2addr(client->user->conn.remote_ip));
		}
		if (client->destroyed)
			str_append(title, " (deinit)");
		break;
	default:
		str_printfa(title, "%u connections", pop3_client_count);
		break;
	}
	str_append_c(title, ']');
	process_title_set(str_c(title));
}

static void pop3_die(void)
{
	/* do nothing. pop3 connections typically die pretty quick anyway. */
}

static void client_add_input(struct client *client, const buffer_t *buf)
{
	struct ostream *output;

	if (buf != NULL && buf->used > 0) {
		struct istream *inputs[] = {
			i_stream_create_copy_from_data(buf->data, buf->used),
			client->input,
			NULL
		};
		client->input = i_stream_create_concat(inputs);
		i_stream_copy_fd(client->input, inputs[1]);
		i_stream_unref(&inputs[0]);
		i_stream_unref(&inputs[1]);
		i_stream_set_input_pending(client->input, TRUE);
	}

	output = client->output;
	o_stream_ref(output);
	o_stream_cork(output);
	(void)client_handle_input(client);
	o_stream_uncork(output);
	o_stream_unref(&output);
}

static int
client_create_from_input(const struct mail_storage_service_input *input,
			 int fd_in, int fd_out, struct client **client_r,
			 const char **error_r)
{
	const char *lookup_error_str =
		"-ERR [SYS/TEMP] "MAIL_ERRSTR_CRITICAL_MSG"\r\n";
	struct mail_storage_service_user *user;
	struct mail_user *mail_user;
	struct pop3_settings *set;
	const char *errstr;

	if (mail_storage_service_lookup_next(storage_service, input,
					     &user, &mail_user, error_r) <= 0) {
		if (write(fd_out, lookup_error_str, strlen(lookup_error_str)) < 0) {
			/* ignored */
		}
		return -1;
	}
	restrict_access_allow_coredumps(TRUE);

	set = mail_storage_service_user_get_set(user)[1];
	if (set->verbose_proctitle)
		verbose_proctitle = TRUE;

	if (settings_var_expand(&pop3_setting_parser_info, set,
				mail_user->pool, mail_user_var_expand_table(mail_user),
				&errstr) <= 0) {
		*error_r = t_strdup_printf("Failed to expand settings: %s", errstr);
		mail_user_deinit(&mail_user);
		mail_storage_service_user_unref(&user);
		return -1;
	}

	*client_r = client_create(fd_in, fd_out, mail_user, user, set);
	return 0;
}

static int lock_session(struct client *client)
{
	int ret;

	i_assert(client->user->namespaces != NULL);
	i_assert(client->set->pop3_lock_session);

	if ((ret = pop3_lock_session(client)) <= 0) {
		client_send_line(client, ret < 0 ?
			"-ERR [SYS/TEMP] Failed to create POP3 session lock." :
			"-ERR [IN-USE] Mailbox is locked by another POP3 session.");
		client_destroy(client, "Couldn't lock POP3 session");
		return -1;
	}

	return 0;
}

#define MSG_BYE_INTERNAL_ERROR "-ERR "MAIL_ERRSTR_CRITICAL_MSG
static int init_namespaces(struct client *client, bool already_logged_in)
{
	const char *error;

	/* finish initializing the user (see comment in main()) */
	if (mail_namespaces_init(client->user, &error) < 0) {
		if (!already_logged_in)
			client_send_line(client, MSG_BYE_INTERNAL_ERROR);

		i_error("%s", error);
		client_destroy(client, error);
		return -1;
	}

	i_assert(client->inbox_ns == NULL);
	client->inbox_ns = mail_namespace_find_inbox(client->user->namespaces);
	i_assert(client->inbox_ns != NULL);

	return 0;
}

static void client_init_session(struct client *client)
{
	const char *error;

	/*
	 * RFC 1939 requires that the session lock gets acquired before the
	 * positive response is sent to the client indicating a transition
	 * to the TRANSACTION state.
	 *
	 * Since the session lock is stored under the INBOX's storage
	 * directory, the locking code requires that the namespaces are
	 * initialized first.
	 *
	 * If the system administrator configured dovecot to not use session
	 * locks, we can send back the positive response before the
	 * potentially long-running namespace initialization occurs.  This
	 * avoids the client possibly timing out during authentication due
	 * to storage initialization taking too long.
	 */
	if (client->set->pop3_lock_session) {
		if (init_namespaces(client, FALSE) < 0)
			return; /* no need to propagate an error */

		if (lock_session(client) < 0)
			return; /* no need to propagate an error */

		if (!IS_STANDALONE())
			client_send_line(client, "+OK Logged in.");
	} else {
		if (!IS_STANDALONE())
			client_send_line(client, "+OK Logged in.");

		if (init_namespaces(client, TRUE) < 0)
			return; /* no need to propagate an error */
	}

	struct event_reason *reason = event_reason_begin("pop3:initialize");
	int ret = client_init_mailbox(client, &error);
	event_reason_end(&reason);

	if (ret < 0) {
		i_error("%s", error);
		client_destroy(client, error);
	}
}

static void main_stdio_run(const char *username)
{
	struct client *client;
	struct mail_storage_service_input input;
	buffer_t *input_buf;
	const char *value, *error, *input_base64;

	i_zero(&input);
	input.module = input.service = "pop3";
	input.username = username != NULL ? username : getenv("USER");
	if (input.username == NULL && IS_STANDALONE())
		input.username = getlogin();
	if (input.username == NULL)
		i_fatal("USER environment missing");
	if ((value = getenv("IP")) != NULL)
		(void)net_addr2ip(value, &input.remote_ip);
	if ((value = getenv("LOCAL_IP")) != NULL)
		(void)net_addr2ip(value, &input.local_ip);

	input_base64 = getenv("CLIENT_INPUT");
	input_buf = input_base64 == NULL ? NULL :
		t_base64_decode_str(input_base64);

	if (client_create_from_input(&input, STDIN_FILENO, STDOUT_FILENO,
				     &client, &error) < 0)
		i_fatal("%s", error);
	client_add_input(client, input_buf);
	client_create_finish(client);

	client_init_session(client);
	/* client may be destroyed now */
}

static void
login_client_connected(const struct master_login_client *login_client,
		       const char *username, const char *const *extra_fields)
{
	struct client *client;
	struct mail_storage_service_input input;
	enum mail_auth_request_flags flags = login_client->auth_req.flags;
	const char *error;
	buffer_t input_buf;

	i_zero(&input);
	input.module = input.service = "pop3";
	input.local_ip = login_client->auth_req.local_ip;
	input.remote_ip = login_client->auth_req.remote_ip;
	input.local_port = login_client->auth_req.local_port;
	input.remote_port = login_client->auth_req.remote_port;
	input.username = username;
	input.userdb_fields = extra_fields;
	input.session_id = login_client->session_id;
	if ((flags & MAIL_AUTH_REQUEST_FLAG_CONN_SECURED) != 0)
		input.conn_secured = TRUE;
	if ((flags & MAIL_AUTH_REQUEST_FLAG_CONN_SSL_SECURED) != 0)
		input.conn_ssl_secured = TRUE;

	buffer_create_from_const_data(&input_buf, login_client->data,
				      login_client->auth_req.data_size);
	if (client_create_from_input(&input, login_client->fd, login_client->fd,
				     &client, &error) < 0) {
		int fd = login_client->fd;

		i_error("%s", error);
		i_close_fd(&fd);
		master_service_client_connection_destroyed(master_service);
		return;
	}
	client_add_input(client, &input_buf);
	client_create_finish(client);

	client_init_session(client);
	/* client may be destroyed now */
}

static void login_client_failed(const struct master_login_client *client,
				const char *errormsg)
{
	const char *msg;

	msg = t_strdup_printf("-ERR [SYS/TEMP] %s\r\n", errormsg);
	if (write(client->fd, msg, strlen(msg)) < 0) {
		/* ignored */
	}
}

static void client_connected(struct master_service_connection *conn)
{
	/* when running standalone, we shouldn't even get here */
	i_assert(master_login != NULL);

	master_service_client_connection_accept(conn);
	master_login_add(master_login, conn->fd);
}

int main(int argc, char *argv[])
{
	static const struct setting_parser_info *set_roots[] = {
		&pop3_setting_parser_info,
		NULL
	};
	struct master_login_settings login_set;
	enum master_service_flags service_flags = 0;
	enum mail_storage_service_flags storage_service_flags =
		MAIL_STORAGE_SERVICE_FLAG_NO_SSL_CA;
	const char *username = NULL, *auth_socket_path = "auth-master";
	int c;

	i_zero(&login_set);
	login_set.postlogin_timeout_secs = MASTER_POSTLOGIN_TIMEOUT_DEFAULT;

	if (IS_STANDALONE() && getuid() == 0 &&
	    net_getpeername(1, NULL, NULL) == 0) {
		printf("-ERR [SYS/PERM] pop3 binary must not be started from "
		       "inetd, use pop3-login instead.\n");
		return 1;
	}

	if (IS_STANDALONE()) {
		service_flags |= MASTER_SERVICE_FLAG_STANDALONE |
			MASTER_SERVICE_FLAG_STD_CLIENT;
	} else {
		service_flags |= MASTER_SERVICE_FLAG_KEEP_CONFIG_OPEN;
	}

	/*
	 * We include MAIL_STORAGE_SERVICE_FLAG_NO_NAMESPACES so that the
	 * mail_user initialization is fast and we can quickly send back the
	 * OK response to LOGIN/AUTHENTICATE.  Otherwise we risk a very slow
	 * namespace initialization to cause client timeouts on login.
	 */
	storage_service_flags |= MAIL_STORAGE_SERVICE_FLAG_NO_NAMESPACES;

	master_service = master_service_init("pop3", service_flags,
					     &argc, &argv, "a:t:u:");
	while ((c = master_getopt(master_service)) > 0) {
		switch (c) {
		case 'a':
			auth_socket_path = optarg;
			break;
		case 't':
			if (str_to_uint(optarg, &login_set.postlogin_timeout_secs) < 0 ||
			    login_set.postlogin_timeout_secs == 0)
				i_fatal("Invalid -t parameter: %s", optarg);
			break;
		case 'u':
			storage_service_flags |=
				MAIL_STORAGE_SERVICE_FLAG_USERDB_LOOKUP;
			username = optarg;
			break;
		default:
			return FATAL_DEFAULT;
		}
	}

	const char *error;
	if (t_abspath(auth_socket_path, &login_set.auth_socket_path, &error) < 0) {
		i_fatal("t_abspath(%s) failed: %s", auth_socket_path, error);
	}
	if (argv[optind] != NULL) {
		if (t_abspath(argv[optind], &login_set.postlogin_socket_path, &error) < 0) {
			i_fatal("t_abspath(%s) failed: %s", argv[optind], error);
		}
	}
	login_set.callback = login_client_connected;
	login_set.failure_callback = login_client_failed;
	if (!IS_STANDALONE())
		master_login = master_login_init(master_service, &login_set);

	master_service_set_die_callback(master_service, pop3_die);

	storage_service =
		mail_storage_service_init(master_service,
					  set_roots, storage_service_flags);
	master_service_init_finish(master_service);
	/* NOTE: login_set.*_socket_path are now invalid due to data stack
	   having been freed */

	/* fake that we're running, so we know if client was destroyed
	   while handling its initial input */
	io_loop_set_running(current_ioloop);

	if (IS_STANDALONE()) {
		T_BEGIN {
			main_stdio_run(username);
		} T_END;
	} else {
		io_loop_set_running(current_ioloop);
	}

	if (io_loop_is_running(current_ioloop))
		master_service_run(master_service, client_connected);
	clients_destroy_all();

	if (master_login != NULL)
		master_login_deinit(&master_login);
	mail_storage_service_deinit(&storage_service);
	master_service_deinit(&master_service);
	return 0;
}