/* Copyright (c) 2006-2017 Dovecot authors, see the included COPYING file */

#include "lib.h"
#include "ioloop.h"
#include "array.h"
#include "str.h"
#include "safe-mkstemp.h"
#include "execv-const.h"
#include "istream.h"
#include "ostream.h"
#include "master-service.h"
#include "lmtp-client.h"
#include "lda-settings.h"
#include "mail-deliver.h"
#include "smtp-client.h"

#include <unistd.h>
#include <sys/wait.h>
#include <sysexits.h>
#include <signal.h>

#define DEFAULT_SUBMISSION_PORT 25

struct smtp_client {
	pool_t pool;
	struct ostream *output;
	int temp_fd;
	pid_t pid;

	bool use_smtp;
	bool success;
	bool finished;

	const struct lda_settings *set;
	const char *temp_path;
	ARRAY_TYPE(const_string) destinations;
	const char *return_path;
	const char *error;
	bool tempfail;
};

static void ATTR_NORETURN
smtp_client_run_sendmail(struct smtp_client *client, int fd)
{
	const char *const *sendmail_args, *const *argv, *str;
	ARRAY_TYPE(const_string) args;
	unsigned int i;

	sendmail_args = t_strsplit(client->set->sendmail_path, " ");
	t_array_init(&args, 16);
	for (i = 0; sendmail_args[i] != NULL; i++)
		array_append(&args, &sendmail_args[i], 1);

	str = "-i"; array_append(&args, &str, 1); /* ignore dots */
	str = "-f"; array_append(&args, &str, 1);
	str = client->return_path != NULL && *client->return_path != '\0' ?
		client->return_path : "<>";
	array_append(&args, &str, 1);

	str = "--"; array_append(&args, &str, 1);
	array_append_array(&args, &client->destinations);
	array_append_zero(&args);
	argv = array_idx(&args, 0);

	if (dup2(fd, STDIN_FILENO) < 0)
		i_fatal("dup2() failed: %m");

	master_service_env_clean();

	execv_const(argv[0], argv);
}

static int create_temp_file(const char **path_r)
{
	string_t *path;
	int fd;

	path = t_str_new(128);
	str_append(path, "/tmp/dovecot.");
	str_append(path, master_service_get_name(master_service));
	str_append_c(path, '.');

	fd = safe_mkstemp(path, 0600, (uid_t)-1, (gid_t)-1);
	if (fd == -1) {
		i_error("safe_mkstemp(%s) failed: %m", str_c(path));
		return -1;
	}

	/* we just want the fd, unlink it */
	if (i_unlink(str_c(path)) < 0) {
		/* shouldn't happen.. */
		i_close_fd(&fd);
		return -1;
	}

	*path_r = str_c(path);
	return fd;
}

struct smtp_client *
smtp_client_init(const struct lda_settings *set, const char *return_path)
{
	struct smtp_client *client;
	pool_t pool;

	pool = pool_alloconly_create("smtp client", 256);
	client = p_new(pool, struct smtp_client, 1);
	client->pool = pool;
	client->set = set;
	client->return_path = p_strdup(pool, return_path);
	client->use_smtp = *set->submission_host != '\0';
	p_array_init(&client->destinations, pool, 2);
	client->pid = (pid_t)-1;
	return client;
}

void smtp_client_add_rcpt(struct smtp_client *client, const char *address)
{
	i_assert(client->output == NULL);

	address = p_strdup(client->pool, address);
	array_append(&client->destinations, &address, 1);
}

static struct ostream *smtp_client_send_sendmail(struct smtp_client *client)
{
	int fd[2];
	pid_t pid;

	if (pipe(fd) < 0) {
		i_error("pipe() failed: %m");
		return o_stream_create_error(errno);
	}

	if ((pid = fork()) == (pid_t)-1) {
		i_error("fork() failed: %m");
		i_close_fd(&fd[0]); i_close_fd(&fd[1]);
		return o_stream_create_error(errno);
	}
	if (pid == 0) {
		/* child */
		i_close_fd(&fd[1]);
		smtp_client_run_sendmail(client, fd[0]);
	}
	i_close_fd(&fd[0]);

	client->output = o_stream_create_fd_autoclose(&fd[1], IO_BLOCK_SIZE);
	o_stream_set_no_error_handling(client->output, TRUE);
	client->pid = pid;
	return client->output;
}

struct ostream *smtp_client_send(struct smtp_client *client)
{
	const char *path;
	int fd;

	i_assert(array_count(&client->destinations) > 0);

	if (!client->use_smtp)
		return smtp_client_send_sendmail(client);

	if ((fd = create_temp_file(&path)) == -1)
		return o_stream_create_error(errno);
	client->temp_path = i_strdup(path);
	client->temp_fd = fd;
	client->output = o_stream_create_fd_autoclose(&fd, IO_BLOCK_SIZE);
	o_stream_set_no_error_handling(client->output, TRUE);
	return client->output;
}

static int smtp_client_deinit_sendmail(struct smtp_client *client)
{
	int ret = EX_TEMPFAIL, status;

	o_stream_destroy(&client->output);

	if (client->pid == (pid_t)-1) {
		/* smtp_client_send() failed already */
	} else if (waitpid(client->pid, &status, 0) < 0)
		i_error("waitpid() failed: %m");
	else if (WIFEXITED(status)) {
		ret = WEXITSTATUS(status);
		if (ret != 0) {
			i_error("Sendmail process terminated abnormally, "
				"exit status %d", ret);
		}
	} else if (WIFSIGNALED(status)) {
		i_error("Sendmail process terminated abnormally, signal %d",
			WTERMSIG(status));
	} else if (WIFSTOPPED(status)) {
		i_error("Sendmail process stopped, signal %d",
			WSTOPSIG(status));
	} else {
		i_error("Sendmail process terminated abnormally, "
			"return status %d", status);
	}
	pool_unref(&client->pool);
	return ret;
}

static void smtp_client_send_finished(void *context)
{
	struct smtp_client *smtp_client = context;

	smtp_client->finished = TRUE;
	io_loop_stop(current_ioloop);
}

static void
smtp_client_error(struct smtp_client *client, const char *error)
{
	if (client->error == NULL) {
		client->error = i_strdup_printf("smtp(%s): %s",
			client->set->submission_host, error);
	}
}

static void
rcpt_to_callback(enum lmtp_client_result result, const char *reply, void *context)
{
	struct smtp_client *client = context;

	if (result != LMTP_CLIENT_RESULT_OK) {
		if (reply[0] != '5')
			client->tempfail = TRUE;
		smtp_client_error(client, t_strdup_printf(
			"RCPT TO failed: %s", reply));
		smtp_client_send_finished(client);
	}
}

static void
data_callback(enum lmtp_client_result result, const char *reply, void *context)
{
	struct smtp_client *client = context;

	if (result != LMTP_CLIENT_RESULT_OK) {
		if (reply[0] != '5')
			client->tempfail = TRUE;
		smtp_client_error(client, t_strdup_printf(
			"DATA failed: %s", reply));
		smtp_client_send_finished(client);
	} else {
		client->success = TRUE;
	}
}

static int
smtp_client_send_flush(struct smtp_client *client,
		       unsigned int timeout_secs, const char **error_r)
{
	struct lmtp_client_settings client_set;
	struct lmtp_client *lmtp_client;
	struct ioloop *ioloop;
	struct istream *input;
	const char *host, *const *destp;
	in_port_t port;

	if (net_str2hostport(client->set->submission_host,
			     DEFAULT_SUBMISSION_PORT, &host, &port) < 0) {
		*error_r = t_strdup_printf(
			"Invalid submission_host: %s", host);
		return -1;
	}

	if (o_stream_nfinish(client->output) < 0) {
		*error_r = t_strdup_printf("write(%s) failed: %s",
			client->temp_path, o_stream_get_error(client->output));
		return -1;
	}

	if (o_stream_seek(client->output, 0) < 0) {
		*error_r = t_strdup_printf("lseek(%s) failed: %s",
			client->temp_path, o_stream_get_error(client->output));
		return -1;
	}

	i_zero(&client_set);
	client_set.mail_from = client->return_path == NULL ? "<>" :
		t_strconcat("<", client->return_path, ">", NULL);
	client_set.my_hostname = client->set->hostname;
	client_set.timeout_secs = timeout_secs;

	ioloop = io_loop_create();
	lmtp_client = lmtp_client_init(&client_set, smtp_client_send_finished,
				  client);

	if (lmtp_client_connect_tcp(lmtp_client, LMTP_CLIENT_PROTOCOL_SMTP,
				    host, port) < 0) {
		lmtp_client_deinit(&lmtp_client);
		io_loop_destroy(&ioloop);
		*error_r = t_strdup_printf("Couldn't connect to %s:%u",
					   host, port);
		return -1;
	}

	array_foreach(&client->destinations, destp) {
		lmtp_client_add_rcpt(lmtp_client, *destp, rcpt_to_callback,
				     data_callback, client);
	}

	input = i_stream_create_fd(client->temp_fd, (size_t)-1, FALSE);
	lmtp_client_send(lmtp_client, input);
	i_stream_unref(&input);

	if (!client->finished)
		io_loop_run(ioloop);
	io_loop_destroy(&ioloop);

	if (client->success)
		return 1;
	else if (client->tempfail) {
		i_assert(client->error != NULL);
		*error_r = t_strdup(client->error);
		return -1;
	} else {
		i_assert(client->error != NULL);
		*error_r = t_strdup(client->error);
		return 0;
	}
}

void smtp_client_abort(struct smtp_client **_client)
{
	struct smtp_client *client = *_client;

	*_client = NULL;

	o_stream_ignore_last_errors(client->output);
	if (!client->use_smtp) {
		if (client->pid != (pid_t)-1)
			(void)kill(client->pid, SIGTERM);
		(void)smtp_client_deinit_sendmail(client);
	} else {
		o_stream_destroy(&client->output);
		pool_unref(&client->pool);
	}
}

int smtp_client_deinit(struct smtp_client *client, const char **error_r)
{
	return smtp_client_deinit_timeout(client, 0, error_r);
}

int smtp_client_deinit_timeout(struct smtp_client *client,
			       unsigned int timeout_secs, const char **error_r)
{
	int ret;

	if (!client->use_smtp) {
		if (smtp_client_deinit_sendmail(client) != 0) {
			*error_r = "Failed to execute sendmail";
			return -1;
		}
		return 1;
	}

	/* the mail has been written to a file. now actually send it. */
	ret = smtp_client_send_flush(client, timeout_secs, error_r);

	smtp_client_abort(&client);
	return ret;
}

struct smtp_client *
smtp_client_open(const struct lda_settings *set, const char *destination,
		 const char *return_path, struct ostream **output_r)
{
	struct smtp_client *client;

	client = smtp_client_init(set, return_path);
	smtp_client_add_rcpt(client, destination);
	*output_r = smtp_client_send(client);
	return client;
}

int smtp_client_close(struct smtp_client *client)
{
	const char *error;
	int ret;

	if (!client->use_smtp)
		return smtp_client_deinit_sendmail(client);

	ret = smtp_client_deinit(client, &error);
	if (ret < 0) {
		i_error("%s", error);
		return EX_TEMPFAIL;
	}
	if (ret == 0) {
		i_error("%s", error);
		return EX_NOPERM;
	}
	return 0;
}