/* Copyright (C) 2000 Michael Elkins <me@mutt.org>
 * Modified 2004 by Alan Ford <alan@whirlnet.co.uk>
 * 
 * This is free software distributed under the terms of the GNU Public License.
 * See the file COPYING for details.
 */

/* A very simple SMTP relay client */

#define PACKAGE "smtppush"
#define VERSION "0.3"
#define DATE "2004-01-28"

#include <sysexits.h>
#include <unistd.h>
#include <stdio.h>
#include <stdarg.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <netdb.h>
#include <errno.h>
#include <string.h>
#include <stdlib.h>
#include <pwd.h>

int Verbose = 0;

void usage (void) {
	fprintf(stderr, "%s %s (%s)\n", PACKAGE, VERSION, DATE);
	fprintf(stderr, "usage: %s [ -hvV ] [ -f FROM ] [ -S SMTPSERVER ] [ -p PORT ] RECIPIENT ...\n", PACKAGE);
	fprintf(stderr, "\noptions:\n");
	fprintf(stderr, "  -f FROM\tUse FROM as envelope return address\n");
	fprintf(stderr, "  -h\t\tPrint this help message\n");
	fprintf(stderr, "  -p PORT\tConnect on PORT (default: 25)\n");
	fprintf(stderr, "  -S SERVER\tUse SERVER as SMTP relay (default: localhost)\n");
	fprintf(stderr, "  -v\t\tDisplay version information\n");
	fprintf(stderr, "  -V\t\tTurn on verbose mode\n");
	exit (EX_USAGE);
}

void version (void) {
	printf ("%s %s\nCopyright (C) 2000-1 Michael Elkins <me@mutt.org>\n",
			PACKAGE, VERSION);
	puts ("Copyright (C) 2004 Alan Ford <alan@whirlnet.co.uk>");
	puts ("http://www.ecs.soton.ac.uk/~ajf101/");
	exit (EX_OK);
}

int get_server_message (int fd) {
	char buf[1024];
	int buflen = 0;
	int n;

	while ((unsigned) buflen < sizeof (buf)) {
		n = read (fd, &buf[buflen], 1);
		if (n <= 0)
			return EX_IOERR;
		if (buf[buflen] == '\r') {
			n = read (fd, &buf[buflen], 1);
			if (n <= 0)
				return EX_IOERR;
		}
		if (buf[buflen] == '\n') {
			buf[buflen] = 0;
			n = strtol (buf, NULL, 10);
			if (Verbose || n >= 400) {
				/* some error occurred */
				fprintf (stderr, "%s: %s\n", PACKAGE, buf);
				if (n >= 400)
					return EX_PROTOCOL;
			}
			return 0;
		}
		buflen++;
	}
	/* line was too long */
	return EX_PROTOCOL;
}

int send_to_server (int fd, const char *fmt, ...) {
	va_list ap;
	char buf[1024];

	va_start (ap, fmt);
	vsnprintf (buf, sizeof (buf) - 3, fmt, ap);
	va_end (ap);

	if (Verbose)
		fprintf (stderr, "%s: <<< %s\n", PACKAGE, buf);

	/* safe since we only used sizeof(buf)-3 above */
	strcat (buf, "\r\n");
	if (write (fd, buf, strlen (buf)) != (int) strlen (buf))
		return -1;
	return 0;
}

int main (int argc, char **argv) {
	int i;
	char *from = NULL;
	char *host = "localhost";
	int port = 25;
	struct sockaddr_in sin;
	struct hostent *he;
	int sock;
	char *myhost = NULL;
	char buf[1024];
	char realhost[256];
	char realfrom[256];

	while ((i = getopt (argc, argv, "hvf:S:p:V")) != -1) {
		switch (i) {
		case 'f':
			from = optarg;
			break;
		case 'S':
			host = optarg;
			break;
		case 'p':
			port = atoi (optarg);
			break;
		case 'V':
			Verbose = 1;
			break;
		case 'v':
			version ();
		case 'h':
		default:
			usage ();
		}
	}
	if (argv[optind] == NULL)
		usage ();

	/* if the return envelope address was set, use the host part as this
	 * hosts dns name
	 */
	if (from) {
		myhost = strchr (from, '@');
		if (!myhost) {
			fprintf (stderr, "%s: no @ found in return address\n", PACKAGE);
			return EX_USAGE;
		}
		myhost++;
	} else {
		struct passwd *pw;

		/* otherwise we need to look it up */
		if (gethostname (realhost, sizeof (realhost))) {
			fprintf (stderr, "%s: gethostname: %s (errno %d)\n", PACKAGE,
					 strerror (errno), errno);
			return EX_OSERR;
		}
		if (Verbose)
			fprintf (stderr, "%s: local host name is %s\n", PACKAGE,
					 realhost);

		/* look up the fqdn */
		he = gethostbyname (realhost);
		if (!he) {
			fprintf (stderr, "%s: gethostbyname: %s: %s (errno %d)\n",
					 PACKAGE, realhost, strerror (h_errno), h_errno);
			exit (EX_NOHOST);
		}
		strcpy (realhost, he->h_name);
		if (Verbose)
			fprintf (stderr, "%s: fqdn is %s\n", PACKAGE, realhost);

		/* find the user's login name */
		pw = getpwuid (getuid ());
		if (!pw) {
			fprintf (stderr, "%s: getpwuid: %s (errno %d)\n", PACKAGE,
					 strerror (errno), errno);
			return EX_OSERR;
		}

		/* form the return address */
		snprintf (realfrom, sizeof (realfrom), "%s@%s", pw->pw_name,
				  realhost);
		if (Verbose)
			fprintf (stderr, "%s: realfrom is %s\n", PACKAGE, realfrom);

		from = realfrom;
		myhost = realhost;
	}

	memset (&sin, 0, sizeof (sin));
	sin.sin_family = AF_INET;
	sin.sin_port = htons (port);
	if (inet_aton (host, &sin.sin_addr) == 0) {
		/* not an ip address, look up hostname */
		he = gethostbyname (host);
		if (!he) {
			fprintf (stderr, "%s: gethostbyname: %s: %s (errno %d)\n",
					 PACKAGE, host, strerror (h_errno), h_errno);
			exit (EX_NOHOST);
		}
		sin.sin_addr.s_addr = *((int *) he->h_addr_list[0]);
	}

	sock = socket (AF_INET, SOCK_STREAM, 0);
	if (sock < 0) {
		fprintf (stderr, "%s: socket: %s (errno %d)\n", PACKAGE,
				 strerror (errno), errno);
		exit (EX_OSERR);
	}

	if (connect (sock, (struct sockaddr *) &sin, sizeof (sin))) {
		fprintf (stderr, "%s: connect: %s (errno %d)\n", PACKAGE,
				 strerror (errno), errno);
		exit (EX_OSERR);
	}

	/* eat the server's greeting */
	i = get_server_message (sock);
	if (i != EX_OK)
		exit (i);

	if (send_to_server (sock, "HELO %s", myhost))
		exit (EX_IOERR);
	i = get_server_message (sock);
	if (i != EX_OK)
		exit (i);

	if (send_to_server (sock, "MAIL FROM: <%s>", from))
		exit (EX_IOERR);
	i = get_server_message (sock);
	if (i != EX_OK)
		exit (i);

	while (argv[optind]) {
		if (send_to_server (sock, "RCPT TO: <%s>", argv[optind]))
			exit (EX_IOERR);
		i = get_server_message (sock);
		if (i != EX_OK)
			exit (i);
		optind++;
	}

	if (send_to_server (sock, "DATA", from))
		exit (EX_IOERR);
	i = get_server_message (sock);
	if (i != EX_OK)
		exit (i);

	/* copy the message from stdin */
	while (fgets (buf, sizeof (buf) - 1, stdin)) {
		buf[strlen (buf) - 1] = 0;
		if (buf[0] == '.')
			if (write (sock, ".", 1) != 1)
				exit (EX_IOERR);
		if (write (sock, buf, strlen (buf)) != (int) strlen (buf))
			exit (EX_IOERR);
		if (write (sock, "\r\n", 2) != 2)
			exit (EX_IOERR);
	}

	if (send_to_server (sock, ".", from))
		exit (EX_IOERR);
	i = get_server_message (sock);
	if (i != EX_OK)
		exit (i);

	close (sock);

	exit (EX_OK);
}