Esempio n. 1
0
static void psc_service(VSTREAM *smtp_client_stream,
			        char *unused_service,
			        char **unused_argv)
{
    const char *myname = "psc_service";
    PSC_STATE *state;
    struct sockaddr_storage addr_storage;
    SOCKADDR_SIZE addr_storage_len = sizeof(addr_storage);
    MAI_HOSTADDR_STR smtp_client_addr;
    MAI_SERVPORT_STR smtp_client_port;
    MAI_HOSTADDR_STR smtp_server_addr;
    MAI_SERVPORT_STR smtp_server_port;
    int     aierr;
    const char *stamp_str;
    int     saved_flags;

    /*
     * For sanity, require that at least one of INET or INET6 is enabled.
     * Otherwise, we can't look up interface information, and we can't
     * convert names or addresses.
     */
    if (inet_proto_info()->ai_family_list[0] == 0)
	msg_fatal("all network protocols are disabled (%s = %s)",
		  VAR_INET_PROTOCOLS, var_inet_protocols);

    /*
     * This program handles all incoming connections, so it must not block.
     * We use event-driven code for all operations that introduce latency.
     * 
     * Note: instead of using VSTREAM-level timeouts, we enforce limits on the
     * total amount of time to receive a complete SMTP command line.
     */
    non_blocking(vstream_fileno(smtp_client_stream), NON_BLOCKING);

    /*
     * We use the event_server framework. This means we get already-accepted
     * connections so we have to invoke getpeername() to find out the remote
     * address and port.
     */

    /* Best effort - if this non-blocking write(2) fails, so be it. */
#define PSC_SERVICE_DISCONNECT_AND_RETURN(stream) do { \
	(void) write(vstream_fileno(stream), \
		     "421 4.3.2 No system resources\r\n", \
		     sizeof("421 4.3.2 No system resources\r\n") - 1); \
	event_server_disconnect(stream); \
	return; \
    } while (0);

    /*
     * Look up the remote SMTP client address and port.
     */
    if (getpeername(vstream_fileno(smtp_client_stream), (struct sockaddr *)
		    & addr_storage, &addr_storage_len) < 0) {
	msg_warn("getpeername: %m -- dropping this connection");
	PSC_SERVICE_DISCONNECT_AND_RETURN(smtp_client_stream);
    }

    /*
     * Convert the remote SMTP client address and port to printable form for
     * logging and access control.
     */
    if ((aierr = sockaddr_to_hostaddr((struct sockaddr *) & addr_storage,
				      addr_storage_len, &smtp_client_addr,
				      &smtp_client_port, 0)) != 0) {
	msg_warn("cannot convert client address/port to string: %s"
		 " -- dropping this connection",
		 MAI_STRERROR(aierr));
	PSC_SERVICE_DISCONNECT_AND_RETURN(smtp_client_stream);
    }
    if (strncasecmp("::ffff:", smtp_client_addr.buf, 7) == 0)
	memmove(smtp_client_addr.buf, smtp_client_addr.buf + 7,
		sizeof(smtp_client_addr.buf) - 7);
    if (msg_verbose > 1)
	msg_info("%s: sq=%d cq=%d connect from [%s]:%s",
		 myname, psc_post_queue_length, psc_check_queue_length,
		 smtp_client_addr.buf, smtp_client_port.buf);

    /*
     * Look up the local SMTP server address and port.
     */
    if (getsockname(vstream_fileno(smtp_client_stream), (struct sockaddr *)
		    & addr_storage, &addr_storage_len) < 0) {
	msg_warn("getsockname: %m -- dropping this connection");
	PSC_SERVICE_DISCONNECT_AND_RETURN(smtp_client_stream);
    }

    /*
     * Convert the local SMTP server address and port to printable form for
     * logging and access control.
     */
    if ((aierr = sockaddr_to_hostaddr((struct sockaddr *) & addr_storage,
				      addr_storage_len, &smtp_server_addr,
				      &smtp_server_port, 0)) != 0) {
	msg_warn("cannot convert server address/port to string: %s"
		 " -- dropping this connection",
		 MAI_STRERROR(aierr));
	PSC_SERVICE_DISCONNECT_AND_RETURN(smtp_client_stream);
    }
    if (strncasecmp("::ffff:", smtp_server_addr.buf, 7) == 0)
	memmove(smtp_server_addr.buf, smtp_server_addr.buf + 7,
		sizeof(smtp_server_addr.buf) - 7);

    msg_info("CONNECT from [%s]:%s to [%s]:%s",
	     smtp_client_addr.buf, smtp_client_port.buf,
	     smtp_server_addr.buf, smtp_server_port.buf);

    /*
     * Bundle up all the loose session pieces. This zeroes all flags and time
     * stamps.
     */
    state = psc_new_session_state(smtp_client_stream, smtp_client_addr.buf,
				  smtp_client_port.buf);

    /*
     * Reply with 421 when the client has too many open connections.
     */
    if (var_psc_cconn_limit > 0
	&& state->client_concurrency > var_psc_cconn_limit) {
	msg_info("NOQUEUE: reject: CONNECT from [%s]:%s: too many connections",
		 state->smtp_client_addr, state->smtp_client_port);
	PSC_DROP_SESSION_STATE(state,
			       "421 4.7.0 Error: too many connections\r\n");
	return;
    }

    /*
     * Reply with 421 when we can't forward more connections.
     */
    if (var_psc_post_queue_limit > 0
	&& psc_post_queue_length >= var_psc_post_queue_limit) {
	msg_info("NOQUEUE: reject: CONNECT from [%s]:%s: all server ports busy",
		 state->smtp_client_addr, state->smtp_client_port);
	PSC_DROP_SESSION_STATE(state,
			       "421 4.3.2 All server ports are busy\r\n");
	return;
    }

    /*
     * The permanent white/blacklist has highest precedence.
     */
    if (psc_acl != 0) {
	switch (psc_acl_eval(state, psc_acl, VAR_PSC_ACL)) {

	    /*
	     * Permanently blacklisted.
	     */
	case PSC_ACL_ACT_BLACKLIST:
	    msg_info("BLACKLISTED [%s]:%s", PSC_CLIENT_ADDR_PORT(state));
	    PSC_FAIL_SESSION_STATE(state, PSC_STATE_FLAG_BLIST_FAIL);
	    switch (psc_blist_action) {
	    case PSC_ACT_DROP:
		PSC_DROP_SESSION_STATE(state,
			     "521 5.3.2 Service currently unavailable\r\n");
		return;
	    case PSC_ACT_ENFORCE:
		PSC_ENFORCE_SESSION_STATE(state,
			     "550 5.3.2 Service currently unavailable\r\n");
		break;
	    case PSC_ACT_IGNORE:
		PSC_UNFAIL_SESSION_STATE(state, PSC_STATE_FLAG_BLIST_FAIL);

		/*
		 * Not: PSC_PASS_SESSION_STATE. Repeat this test the next
		 * time.
		 */
		break;
	    default:
		msg_panic("%s: unknown blacklist action value %d",
			  myname, psc_blist_action);
	    }
	    break;

	    /*
	     * Permanently whitelisted.
	     */
	case PSC_ACL_ACT_WHITELIST:
	    msg_info("WHITELISTED [%s]:%s", PSC_CLIENT_ADDR_PORT(state));
	    psc_conclude(state);
	    return;

	    /*
	     * Other: dunno (don't know) or error.
	     */
	default:
	    break;
	}
    }

    /*
     * The temporary whitelist (i.e. the postscreen cache) has the lowest
     * precedence. This cache contains information about the results of prior
     * tests. Whitelist the client when all enabled test results are still
     * valid.
     */
    if ((state->flags & PSC_STATE_MASK_ANY_FAIL) == 0
	&& psc_cache_map != 0
	&& (stamp_str = psc_cache_lookup(psc_cache_map, state->smtp_client_addr)) != 0) {
	saved_flags = state->flags;
	psc_parse_tests(state, stamp_str, event_time());
	state->flags |= saved_flags;
	if (msg_verbose)
	    msg_info("%s: cached + recent flags: %s",
		     myname, psc_print_state_flags(state->flags, myname));
	if ((state->flags & PSC_STATE_MASK_ANY_TODO_FAIL) == 0) {
	    msg_info("PASS OLD [%s]:%s", PSC_CLIENT_ADDR_PORT(state));
	    psc_conclude(state);
	    return;
	}
    } else {
	saved_flags = state->flags;
	psc_new_tests(state);
	state->flags |= saved_flags;
	if (msg_verbose)
	    msg_info("%s: new + recent flags: %s",
		     myname, psc_print_state_flags(state->flags, myname));
    }

    /*
     * Don't whitelist clients that connect to backup MX addresses. Fail
     * "closed" on error.
     */
    if (addr_match_list_match(psc_wlist_if, smtp_server_addr.buf) == 0) {
	state->flags |= (PSC_STATE_FLAG_WLIST_FAIL | PSC_STATE_FLAG_NOFORWARD);
	msg_info("WHITELIST VETO [%s]:%s", PSC_CLIENT_ADDR_PORT(state));
    }

    /*
     * Reply with 421 when we can't analyze more connections. That also means
     * no deep protocol tests when the noforward flag is raised.
     */
    if (var_psc_pre_queue_limit > 0
	&& psc_check_queue_length - psc_post_queue_length
	>= var_psc_pre_queue_limit) {
	msg_info("reject: connect from [%s]:%s: all screening ports busy",
		 state->smtp_client_addr, state->smtp_client_port);
	PSC_DROP_SESSION_STATE(state,
			       "421 4.3.2 All screening ports are busy\r\n");
	return;
    }

    /*
     * If the client has no up-to-date results for some tests, do those tests
     * first. Otherwise, skip the tests and hand off the connection.
     */
    if (state->flags & PSC_STATE_MASK_EARLY_TODO)
	psc_early_tests(state);
    else if (state->flags & (PSC_STATE_MASK_SMTPD_TODO | PSC_STATE_FLAG_NOFORWARD))
	psc_smtpd_tests(state);
    else
	psc_conclude(state);
}
Esempio n. 2
0
static void psc_endpt_lookup_done(int endpt_status,
				          VSTREAM *smtp_client_stream,
				          MAI_HOSTADDR_STR *smtp_client_addr,
				          MAI_SERVPORT_STR *smtp_client_port,
				          MAI_HOSTADDR_STR *smtp_server_addr,
				          MAI_SERVPORT_STR *smtp_server_port)
{
    const char *myname = "psc_endpt_lookup_done";
    PSC_STATE *state;
    const char *stamp_str;
    int     saved_flags;

    /*
     * Best effort - if this non-blocking write(2) fails, so be it.
     */
    if (endpt_status < 0) {
	(void) write(vstream_fileno(smtp_client_stream),
		     "421 4.3.2 No system resources\r\n",
		     sizeof("421 4.3.2 No system resources\r\n") - 1);
	event_server_disconnect(smtp_client_stream);
	return;
    }
    if (msg_verbose > 1)
	msg_info("%s: sq=%d cq=%d connect from [%s]:%s",
		 myname, psc_post_queue_length, psc_check_queue_length,
		 smtp_client_addr->buf, smtp_client_port->buf);

    msg_info("CONNECT from [%s]:%s to [%s]:%s",
	     smtp_client_addr->buf, smtp_client_port->buf,
	     smtp_server_addr->buf, smtp_server_port->buf);

    /*
     * Bundle up all the loose session pieces. This zeroes all flags and time
     * stamps.
     */
    state = psc_new_session_state(smtp_client_stream, smtp_client_addr->buf,
				  smtp_client_port->buf,
				  smtp_server_addr->buf,
				  smtp_server_port->buf);

    /*
     * Reply with 421 when the client has too many open connections.
     */
    if (var_psc_cconn_limit > 0
	&& state->client_concurrency > var_psc_cconn_limit) {
	msg_info("NOQUEUE: reject: CONNECT from [%s]:%s: too many connections",
		 state->smtp_client_addr, state->smtp_client_port);
	PSC_DROP_SESSION_STATE(state,
			       "421 4.7.0 Error: too many connections\r\n");
	return;
    }

    /*
     * Reply with 421 when we can't forward more connections.
     */
    if (var_psc_post_queue_limit > 0
	&& psc_post_queue_length >= var_psc_post_queue_limit) {
	msg_info("NOQUEUE: reject: CONNECT from [%s]:%s: all server ports busy",
		 state->smtp_client_addr, state->smtp_client_port);
	PSC_DROP_SESSION_STATE(state,
			       "421 4.3.2 All server ports are busy\r\n");
	return;
    }

    /*
     * The permanent white/blacklist has highest precedence.
     */
    if (psc_acl != 0) {
	switch (psc_acl_eval(state, psc_acl, VAR_PSC_ACL)) {

	    /*
	     * Permanently blacklisted.
	     */
	case PSC_ACL_ACT_BLACKLIST:
	    msg_info("BLACKLISTED [%s]:%s", PSC_CLIENT_ADDR_PORT(state));
	    PSC_FAIL_SESSION_STATE(state, PSC_STATE_FLAG_BLIST_FAIL);
	    switch (psc_blist_action) {
	    case PSC_ACT_DROP:
		PSC_DROP_SESSION_STATE(state,
			     "521 5.3.2 Service currently unavailable\r\n");
		return;
	    case PSC_ACT_ENFORCE:
		PSC_ENFORCE_SESSION_STATE(state,
			     "550 5.3.2 Service currently unavailable\r\n");
		break;
	    case PSC_ACT_IGNORE:
		PSC_UNFAIL_SESSION_STATE(state, PSC_STATE_FLAG_BLIST_FAIL);

		/*
		 * Not: PSC_PASS_SESSION_STATE. Repeat this test the next
		 * time.
		 */
		break;
	    default:
		msg_panic("%s: unknown blacklist action value %d",
			  myname, psc_blist_action);
	    }
	    break;

	    /*
	     * Permanently whitelisted.
	     */
	case PSC_ACL_ACT_WHITELIST:
	    msg_info("WHITELISTED [%s]:%s", PSC_CLIENT_ADDR_PORT(state));
	    psc_conclude(state);
	    return;

	    /*
	     * Other: dunno (don't know) or error.
	     */
	default:
	    break;
	}
    }

    /*
     * The temporary whitelist (i.e. the postscreen cache) has the lowest
     * precedence. This cache contains information about the results of prior
     * tests. Whitelist the client when all enabled test results are still
     * valid.
     */
    if ((state->flags & PSC_STATE_MASK_ANY_FAIL) == 0
	&& psc_cache_map != 0
	&& (stamp_str = psc_cache_lookup(psc_cache_map, state->smtp_client_addr)) != 0) {
	saved_flags = state->flags;
	psc_parse_tests(state, stamp_str, event_time());
	state->flags |= saved_flags;
	if (msg_verbose)
	    msg_info("%s: cached + recent flags: %s",
		     myname, psc_print_state_flags(state->flags, myname));
	if ((state->flags & PSC_STATE_MASK_ANY_TODO_FAIL) == 0) {
	    msg_info("PASS OLD [%s]:%s", PSC_CLIENT_ADDR_PORT(state));
	    psc_conclude(state);
	    return;
	}
    } else {
	saved_flags = state->flags;
	psc_new_tests(state);
	state->flags |= saved_flags;
	if (msg_verbose)
	    msg_info("%s: new + recent flags: %s",
		     myname, psc_print_state_flags(state->flags, myname));
    }

    /*
     * Don't whitelist clients that connect to backup MX addresses. Fail
     * "closed" on error.
     */
    if (addr_match_list_match(psc_wlist_if, smtp_server_addr->buf) == 0) {
	state->flags |= (PSC_STATE_FLAG_WLIST_FAIL | PSC_STATE_FLAG_NOFORWARD);
	msg_info("WHITELIST VETO [%s]:%s", PSC_CLIENT_ADDR_PORT(state));
    }

    /*
     * Reply with 421 when we can't analyze more connections. That also means
     * no deep protocol tests when the noforward flag is raised.
     */
    if (var_psc_pre_queue_limit > 0
	&& psc_check_queue_length - psc_post_queue_length
	>= var_psc_pre_queue_limit) {
	msg_info("reject: connect from [%s]:%s: all screening ports busy",
		 state->smtp_client_addr, state->smtp_client_port);
	PSC_DROP_SESSION_STATE(state,
			       "421 4.3.2 All screening ports are busy\r\n");
	return;
    }

    /*
     * If the client has no up-to-date results for some tests, do those tests
     * first. Otherwise, skip the tests and hand off the connection.
     */
    if (state->flags & PSC_STATE_MASK_EARLY_TODO)
	psc_early_tests(state);
    else if (state->flags & (PSC_STATE_MASK_SMTPD_TODO | PSC_STATE_FLAG_NOFORWARD))
	psc_smtpd_tests(state);
    else
	psc_conclude(state);
}