smtp.c

smtp proxy source code!

			printf ("451 Service unavailable\r\n");
			syslog(LOG_NOTICE, "can't execute: %s: %m", config->argv[0]);
			exit (1);
			}
		else {	
			x->sin  = fdopen(pin[0], "r");
			close(pin[1]);
			
			x->sout = fdopen(pout[1], "w");
			close(pout[0]);

			p = config->argv[0];
			}
		}
	else {
		printf ("451 Service unavailable\r\n");
		syslog(LOG_NOTICE, "no server specified");
		exit (1);
		}


	syslog(LOG_NOTICE, "connected to server: %s", p);


	/* Konfiguration uebernehmen
	 */

	x->config = config;


	/* Hostnamen holen
	 */

	gethostname(word, sizeof(word));
	getdomainname(line, sizeof(line));
	snprintf (x->hostname, sizeof(x->hostname) - 2, word, line);
	

	/* Greeting Message vom Sendmail Server lesen, und an
	 * Client schicken.
	 */

	rc = getresp(line, sizeof(line), x->sin, debug);
	while (line[3] != ' ') {
		rc = getresp(line, sizeof(line), x->sin, debug);
		if (rc == -1) {
			syslog(LOG_NOTICE, "lost server while reading server greeting");
			exit (1);
			}
		}
		
	echoline(stdout, line, rc);


	/* Wir stellen uns beim lokalen Sendmail Server vor. Die
	 * EHLO-replys werden 'verschluckt' und durch einen eigenen
	 * ersetzt.
	 */

	putcmd(x->sout, "EHLO", "localhost", "SVR");
	while ((rc = getresp(line, sizeof(line), x->sin, debug)) != -1) {
		if (line[3] == ' ')
			break;
		}

	rc = atol(line);
	if (rc != 250) {
		syslog(LOG_NOTICE, "server HELO: status is not 250");
		echoline(stdout, "421 service unavailable", 0);

		return (-1);
		}
					



	/*
	 *  **  S M T P   M A I N L O O P
	 */

	x->state = WAITING;
	while (1) {
		rc = 0;		/* Server response code loeschen */


		/* Naechstes Kommando vom Client holen
		 */

		fflush(stdout);
		if (get_clientinput(line, sizeof(line), x->config->timeout) == NULL) {
			syslog(LOG_NOTICE, "client closed connection");
			break;
			}


		/* Kommando isolieren
		 */

		p = noctrl(line);
		get_word(&p, command, sizeof(command));
		strupr(command);
		p = skip_ws(p);


		/* QUIT ist immer moeglich.
		 */

		if (strcmp(command, "QUIT") == 0) {
			putcmd(x->sout, "QUIT", "", "SVR");
			rc = getresp(line, sizeof(line), x->sin, debug);
			echoline(stdout, line, rc);

			x->state = SEND_QUIT;
			break;
			}


		/* HELP
		 */

		else if (strcmp(command, "HELP") == 0) {
			echoline(stdout, "503 no help available", 0);
			}


		/* NOOP 
		 */

		else if (strcmp(command, "NOOP") == 0) {
			putcmd(x->sout, "NOOP", "", "SVR");
			rc = getresp(line, sizeof(line), x->sin, debug);
			echoline(stdout, line, rc);
			}


		/* RSET
		 */

		else if (strcmp(command, "RSET") == 0) {
			putcmd(x->sout, "RSET", "", "SVR");
			rc = getresp(line, sizeof(line), x->sin, debug);
			echoline(stdout, line, rc);

			reset_connection(x);
			syslog(LOG_NOTICE, "RSET command, client= %s", x->client);
			}


		/* ETRN
		 */

		else if (strcmp(command, "ETRN") == 0) {
			if (x->config->etrn == 0) {
				echoline(stdout, "500 unrecognized command", 0);
				syslog(LOG_NOTICE, "ETRN request rejected: client= %s", x->client);
				}
			else {
				if (*get_word(&p, word, sizeof(word)) == 0)
					echoline(stdout, "500 ETRN needs parameter", 0);
				else {
					putcmd(x->sout, "ETRN", word, "SVR");
					rc = getresp(line, sizeof(line), x->sin, debug);
					echoline(stdout, line, rc);
					if (rc != 250)
						syslog(LOG_NOTICE, "ETRN rejected by server, client= %s", x->client);
					}
				}
			}


		/* HELO und EHLO sind auch immer verfuegbar, aber nur
		 * einmal.
		 */

		else if (strcmp(command, "HELO") == 0  ||  strcmp(command, "EHLO") == 0) {
			if (x->helloseen != 0)
				echoline(stdout, "503 duplicate HELO/EHLO", 0);
			else if (*get_word(&p, word, sizeof(word)) == 0) {
				snprintf (line, sizeof(line) - 2, "501 %s requires domain name", command);
				echoline(stdout, line, 0);
				}
			else {
				if (strcmp(command, "HELO") == 0) {
					snprintf (line, sizeof(line) - 2, "250 SMTP server v%s ready %s [%s]", VERSION, x->client, x->ipnum);
					echoline(stdout, line, 0);
					}
				else {
					snprintf (line, sizeof(line) - 2, "250-SMTP server v%s ready %s [%s]", VERSION, x->client, x->ipnum);
					echoline(stdout, line, 0);
					
					echoline(stdout, "250-8BITMIME", 0);

					if (x->config->etrn != 0)
						echoline(stdout, "250-ETRN", 0);

					echoline(stdout, "250 HELP", 0);
					}
					
				x->helloseen = 1;
				}
			}


		/* MAIL, SEND, SOML, SAML
		 *
		 * Laut RFC 821 kann das MAIL Kommando jederzeit abgesetzt
		 * werden, es macht dabei einen impliziten SMTP-Reset. Der
		 * real existierende Sendmail will davon aber nichts wissen.
		 */

		else if (strcmp(command, "MAIL") == 0  || strcmp(command, "SEND") == 0  ||
		    strcmp(command, "SOML") == 0  || strcmp(command, "SAML") == 0) {
			
			get_quoted(&p, ':', word, sizeof(word));
			if (strcasecmp(word, "FROM") != 0)
				echoline(stdout, "500 syntax error", 0);
			else if (*x->sender != 0)
				echoline(stdout, "503 sender already specified", 0);
			else {
				int	allowed;
				char	sender[200], emailadr[200];
				
				p = skip_ws(p);
				get_word(&p, sender, sizeof(sender));
				strlwr(sender);


				/*
				 * Wir machen ein paar grundsaetzliche Tests mit
				 * der Absenderadresse:
				 *
				 *  - Ist die Adresse von spitzen Klammern
				 *    umgeben?
				 * ...
				 */

				allowed = 1;
				get_emailadr(sender, emailadr, sizeof(emailadr));
				if (*emailadr == 0)
					allowed = 0;

				/*
				 * ...
				 *  - Enthaelt die Adresse mindestens ein @-Zeichen?
				 *  - Enthaelt die Adresse genau ein @-Zeichen?
				 *  - Ist in der Adresse kein !- und kein %-Zeichen
				 *    enthalten.
				 * ...
				 */

				else if (check_emailadr(emailadr) == 0)
					allowed = 0;

				/*
				 * ...
				 *  - Schliesslich wird ggf. noch getestet,
				 *    ob die Absenderadresse auch auf der
				 *    allow-Liste steht.
				 *
				 * Mit den Empfaengeradressen werden die gleichen Tests
				 * durchgefuehrt.
				 */

				else if ((p = x->config->senderlist) == NULL  ||  *p == 0)
					allowed = 1;	/* kein Adresstest */
				else 
					allowed = search_allowlist(emailadr, x->config->senderlist);


				if (allowed == 0) {
					char	line[300];

					snprintf (line, sizeof(line) - 2, "550 not allowed: %s", sender);
					echoline(stdout, line, 0);
					syslog(LOG_NOTICE, "sender rejected: %s, client= %s", sender, x->client);
					}
				else {
					snprintf (line, sizeof(line) - 2, "%s FROM: %s", command, sender);
					putcmd(x->sout, line, "", "SVR");
					rc = getresp(line, sizeof(line), x->sin, debug);
					echoline(stdout, line, rc);

					if (rc == 250) {
						copy_string(x->sender, sender, sizeof(sender));
						x->state = MAIL_SEEN;
						}
					}
				}
			}


		/* RCPT
		 */

		else if (strcmp(command, "RCPT") == 0) {
			get_quoted(&p, ':', word, sizeof(word));
			if (strcasecmp(word, "TO") != 0)
				echoline(stdout, "500 syntax error", 0);
			else if (x->state != MAIL_SEEN  &&  x->state != RCPT_SEEN)
				echoline(stdout, "503 specify sender first", 0);
			else {
				int	allowed;
				char	rcpt[200], emailadr[200];
				
				p = skip_ws(p);
				get_word(&p, rcpt, sizeof(rcpt));
				strlwr(rcpt);


				get_emailadr(rcpt, emailadr, sizeof(emailadr));
				if (*emailadr == 0)
					allowed = 0;
				else if (check_emailadr(emailadr) == 0)
					allowed = 0;
				else if ((p = x->config->rcptlist) == NULL  ||  *p == 0)
					allowed = 1;
				else 
					allowed = search_allowlist(emailadr, x->config->rcptlist);


				if (allowed == 0) {
					char	line[300];

					snprintf (line, sizeof(line) - 2, "550 no such user: %s", rcpt);
					echoline(stdout, line, 0);
					syslog(LOG_NOTICE, "recipient rejected: %s, client= %s", rcpt, x->client);
					}
				else {
					putcmd(x->sout, "RCPT TO:", rcpt, "SVR");
					rc = getresp(line, sizeof(line), x->sin, debug);
					echoline(stdout, line, rc);

					if (rc == 250  ||  rc == 251) {
						x->nrcpt++;
						x->state = RCPT_SEEN;
						}
					}
				}
			}


		/* DATA
		 */

		else if (strcmp(command, "DATA") == 0) {
			x->mailcount++;

			if (x->state != RCPT_SEEN)
				echoline(stdout, "503 specify receipients first", 0);
			else {
				putcmd(x->sout, "DATA", "", "SVR");
				rc = getresp(line, sizeof(line), x->sin, debug);
				echoline(stdout, line, rc);

				if (rc == 354) {
					if ((rc = receive_data(x)) == 0) {
						rc = getresp(line, sizeof(line), x->sin, debug);
						echoline(stdout, line, rc);

						if (rc == 250) {
							p = line;
							get_word(&p, word, sizeof(word));
							get_word(&p, x->jobid, sizeof(x->jobid));
							}
						}
					}

				snprintf (line, sizeof(line) - 2, "client= %s, sender= %s, nrcpt= %d, size= %ld, jobid= <%s>, message-id= <%s>, status= %d",
									x->client, x->sender, x->nrcpt, x->size,
									x->jobid, x->msgid, rc);
				syslog(LOG_NOTICE, line);

				reset_connection(x);
				x->state = WAITING;
				}
			}


		/* Alles andere ist unserem Server unbekannt.
		 */

		else {
			fprintf (stderr, "500 unrecognized command\r\n");
			}


		if (rc == 421) {
			syslog(LOG_NOTICE, "sendmail returned 421, state= %d, command= %s", x->state, command);
			break;
			}
		else if (rc == -1) {
			syslog(LOG_NOTICE, "terminating (sendmail terminated)");
			x->state = NO_SENDMAIL;

			break;
			}
		}

	if (x->state != SEND_QUIT  &&  x->state != NO_SENDMAIL) {
		putcmd(x->sout, "QUIT", "", "SVR");
		rc = getresp(line, sizeof(line), x->sin, debug);
		}

end:
	syslog(LOG_NOTICE, "client %s disconnecting, %d mails", x->client, x->mailcount);
	return (0);
}