smtp.c

smtp proxy source code!

/*

    File: smtp/smtp.c
    
    Copyright (C) 1999 by Wolfgang Zekoll <[e-mail]>

    This source is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 1, or (at your option)
    any later version.

    This source is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

*/


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

#include <sys/types.h>
#include <sys/stat.h>
#include <sys/fcntl.h>
#include <sys/socket.h>
#include <signal.h>
#include <netdb.h>
#include <netinet/in.h>
#include <syslog.h>
#include <sys/time.h>

#include "smtp.h"
#include "ip-lib.h"
#include "lib.h"


int sdebug(char *line)
{
	if (debug != 0) {
		noctrl(line);
		fprintf (stderr, "*** %s\n", line);
		}

	return (0);
}

char *getline(char *line, int size, FILE *fp, int debug)
{
	*line = 0;
	if (fgets(line, size, fp) == NULL) {
		syslog(LOG_NOTICE, "sendmail closed read pipe.");
		return (NULL);
		}

	noctrl(line);
	if (debug != 0)
		sdebug(line);

	return (line);
}

int getresp(char *line, int size, FILE *fp, int debug)
{
	if (getline(line, size, fp, debug) == NULL)
		return (-1);

	return (atoi(line));
}


int echoline(FILE *fp, char *line, int rc)
{
	if (rc == -1) {
		syslog(LOG_NOTICE, "closing connection with 421");
		fprintf (fp, "421 service unavailable\r\n");
		}
	else {
		noctrl(line);
		fprintf (fp, "%s\r\n", line);
		}

	fflush(fp);
	return (0);
}

int putcmd(FILE *fp, char *cmd, char *par, char *dbg)
{
	fprintf (fp, "%s", cmd);
	if (par != NULL  &&  *par != 0)
		fprintf (fp, " %s", par);

	fprintf (fp, "\n");
	fflush(fp);
	
	if (debug != 0  &&  dbg != NULL  &&  *dbg != 0)
		fprintf (stderr, ">>> %s: %s %s\n", dbg, cmd, par);

	return (0);
}



int reset_connection(smtp_t *x)
{
	x->nrcpt    = 0;
	x->state    = WAITING;

	*x->sender  = 0;
	x->nrcpt    = 0;
	*x->jobid   = 0;
	*x->msgid   = 0;
	x->size     = 0;

	return (0);
}



void sigalrm_handler(int sig)
{
	syslog(LOG_NOTICE, "client timed out");
	fclose (stdin);
	return;
}

char *get_clientinput(char *line, int size, int timeout)
{
	char	*p;
	
	alarm(timeout);
	signal(SIGALRM, sigalrm_handler);
	
	*line = 0;
	p = fgets(line, size, stdin);
	noctrl(line);
	
	return (p);
}


char *get_emailadr(char *envelope, char *email, int size)
{
	char	*p, *r;

	*email = 0;

	/*
	 * Sonderfall: Es ist moeglich, dass die envelope Adresse `<>'
	 * ist.  In diesem liefern wir sie unveraendert zurueck.  Das
	 * beisst sich nicht mit Adressen der Form `<<>>', da geschachtelte
	 * spitze Klammern nicht unterstuetzt werden.
	 */

	if (strcmp(envelope, "<>") == 0) {
		strcpy(email, "<>");
		return (email);
		}


	p = envelope;
	if (*p != '<')
		return (email);
	
	p++;
	if ((r = strchr(p, '>')) == NULL)
		return (email);
	else if (r[1] != 0)
		return (email);

	get_quoted(&p, '>', email, size);
	return (email);
}

int check_emailadr(char *emailadr)
{
	char	*domain;

	if (strcmp(emailadr, "<>") == 0)
		return (1);
	else if (*emailadr == 0)
		return (0);
/*	else if (*emailadr == '@')
 *		return (0);
 */
	else if ((domain = strchr(emailadr, '@')) == NULL)
		return (0);
/*	else if (domain[1] == '0')
 *		return (0);
 */
	else if (strchr(&domain[1], '@') != NULL)
		return (0);
	else if (strchr(emailadr, '!') != NULL  ||  strchr(emailadr, '%') != NULL)
		return (0);
	else if (strchr(emailadr, ':') != NULL  ||  strchr(emailadr, ',') != NULL)
		return (0);
	
	return (1);
}

int search_allowlist(char *emailadr, char *list)
{
	char	*p, *domain, pattern[200];

	if (strcmp(emailadr, "<>") == 0)
		return (1);

	domain = strchr(emailadr, '@');
	if (domain == NULL  ||  *domain == 0) {

		/*
		 * Das kann eigentlich nicht passieren, die E-Mail Adresse
		 * wurde schon auf genau ein @-Zeichen getestet.
		 */

		return (0);
		}
	else if (list == NULL  ||  *list == 0) {
		
		/*
		 * Kann eigentlich auch nicht vorkommen.
		 */

		return (0);
		}

	p = list;
	while ((p = skip_ws(p)), *get_quoted(&p, ',', pattern, sizeof(pattern)) != 0) {
		noctrl(pattern);
		if (*pattern == '@'  &&  strpcmp(domain, pattern) == 0)
			return (1);
		else if (strpcmp(emailadr, pattern) == 0)
			return (1);
		}
	
	return (0);
}


int receive_data(smtp_t *x)
{
	int	lineno, isheader, bytes;
	char	line[2048];

	lineno   = 0;
	isheader = 1;
	while (1) {
		if (get_clientinput(line, sizeof(line), x->config->timeout) == NULL) {
			syslog(LOG_NOTICE, "client terminated while sending data");
			return (-1);
			}

		lineno++;
		noctrl(line);


		/* Received Zeile einbauen
		 */

		if (lineno == 1) {
			if (x->config->droppath != 2) {
				fprintf (x->sout, "Received: from %s (%s) by %s\r\n",
						x->client, x->ipnum, x->hostname);
				}
			}




		/*
		 * Ggf. Message-ID aus Mail-Header lesen, bzw. Mail-Path
		 * aus dem Header loeschen.
		 */

		if (isheader == 1) {
			if (*line == 0) {
				isheader = 0;

				if (*x->msgid == 0) {
					unsigned long now;

					now = time(NULL);
					snprintf (x->msgid, sizeof(x->msgid) - 2, "%lu.%d.%d", now, getpid(), x->mailcount);
					syslog(LOG_NOTICE, "no message id, assuming %s, client= %s", x->msgid, x->client);
					}
				}
			else {
				char	*p, word[80];

				p = line;
				get_word(&p, word, sizeof(word));
				strlwr(word);
				
				if (strcmp(word, "message-id:") == 0) {
					if (*x->msgid != 0) {
						syslog(LOG_NOTICE, "duplicate message id, client= %s", x->client);
						continue;
						}
					else {
						if ((p = strchr(p, '<')) != NULL) {
							p++;
							get_quoted(&p, '>', x->msgid, sizeof(x->msgid));
							}
						}
					}
				else if (strcmp(word, "received:") == 0) {
					if (x->config->droppath != 0)
						continue;
					}
				}
			}


		/* Zeile an Sendmail weitergeben
		 */

		if ((bytes = fprintf(x->sout, "%s\r\n", line)) != strlen(line) + 2) {
			syslog(LOG_NOTICE, "server terminated while receiving data");
			return (-1);
			}

		x->size += bytes;



		/* Ende der Mail erreicht?
		 */

		if (line[0] == '.'  &&  line[1] == 0) {
			fflush(x->sout);
			break;
			}
		}
		
	return (0);
}


int proxy_request(config_t *config)
{
	int	rc;
	char	*p, command[10], word[200], line[2048];
	smtp_t	*x;

	x = allocate(sizeof(smtp_t));

	get_client_info(0, x->ipnum, x->client);
	x->mailcount = 0;
	syslog(LOG_NOTICE, "connected to client: %s", x->ipnum);


	if (*config->clientdir != 0) {
		char	logfile[200];
		unsigned long now;
		struct stat sbuf;

		now = time(NULL);
		snprintf (logfile, sizeof(logfile) - 2, "%s/%s", config->clientdir, x->ipnum);
		if (stat(logfile, &sbuf) != 0  ||  (now - sbuf.st_mtime) >= config->accepttime) {
			printf ("421 service unavailable - authenticate with POP3 first\r\n");
			syslog(LOG_NOTICE, "client not permitted: %s", x->ipnum);
			goto end;
			}
		}

	if (*config->server != 0) {
		unsigned int port;
		char	server[200];

		copy_string(server, config->server, sizeof(server));
		port = get_port(server, 25);
		
		if ((x->sin = ip_open(server, port)) == NULL) {
			printf ("451 Service unavailable\r\n");
			syslog(LOG_NOTICE, "can't connect to server: %s:%u, %m", server, port);
			exit (1);
			}
			
		x->sout = x->sin;
		p = config->server;
		}
	else if (config->argv != NULL) {
		int	pid, pin[2], pout[2];

		if (pipe(pin) != 0  ||  pipe(pout) != 0) {
			printf ("451 Service unavailable\r\n");
			syslog(LOG_NOTICE, "can't pipe(): %m");
			exit (-1);
			}
		else if ((pid = fork()) < 0) {
			printf ("451 Service unavailable\r\n");
			syslog(LOG_NOTICE, "can't fork(): %m");
			exit (-1);
			}
		else if (pid == 0) {
			dup2(pin[1], 1);
			close (pin[0]);
			
			dup2(pout[0], 0);
			close(pout[1]);
			
			close (2);
			execvp(config->argv[0], config->argv);