-/* $Cambridge: exim/src/src/smtp_in.c,v 1.54 2007/02/20 11:37:16 ph10 Exp $ */
+/* $Cambridge: exim/src/src/smtp_in.c,v 1.55 2007/02/20 15:58:02 ph10 Exp $ */
/*************************************************
* Exim - an Internet mail transport agent *
+
/*************************************************
* Read one command line *
*************************************************/
+/*************************************************
+* Recheck synchronization *
+*************************************************/
+
+/* Synchronization checks can never be perfect because a packet may be on its
+way but not arrived when the check is done. Such checks can in any case only be
+done when TLS is not in use. Normally, the checks happen when commands are
+read: Exim ensures that there is no more input in the input buffer. In normal
+cases, the response to the command will be fast, and there is no further check.
+
+However, for some commands an ACL is run, and that can include delays. In those
+cases, it is useful to do another check on the input just before sending the
+response. This also applies at the start of a connection. This function does
+that check by means of the select() function, as long as the facility is not
+disabled or inappropriate. A failure of select() is ignored.
+
+When there is unwanted input, we read it so that it appears in the log of the
+error.
+
+Arguments: none
+Returns: TRUE if all is well; FALSE if there is input pending
+*/
+
+static BOOL
+check_sync(void)
+{
+int fd, rc;
+fd_set fds;
+struct timeval tzero;
+
+if (!smtp_enforce_sync || sender_host_address == NULL ||
+ sender_host_notsocket || tls_active >= 0)
+ return TRUE;
+
+fd = fileno(smtp_in);
+FD_ZERO(&fds);
+FD_SET(fd, &fds);
+tzero.tv_sec = 0;
+tzero.tv_usec = 0;
+rc = select(fd + 1, (SELECT_ARG2_TYPE *)&fds, NULL, NULL, &tzero);
+
+if (rc <= 0) return TRUE; /* Not ready to read */
+rc = smtp_getc();
+if (rc < 0) return TRUE; /* End of file or error */
+
+smtp_ungetc(rc);
+rc = smtp_inend - smtp_inptr;
+if (rc > 150) rc = 150;
+smtp_inptr[rc] = 0;
+return FALSE;
+}
+
+
+
/*************************************************
* Forced closedown of call *
*************************************************/
/* Before we write the banner, check that there is no input pending, unless
this synchronisation check is disabled. */
-if (smtp_enforce_sync && sender_host_address != NULL && !sender_host_notsocket)
+if (!check_sync())
{
- fd_set fds;
- struct timeval tzero;
- tzero.tv_sec = 0;
- tzero.tv_usec = 0;
- FD_ZERO(&fds);
- FD_SET(fileno(smtp_in), &fds);
- if (select(fileno(smtp_in) + 1, (SELECT_ARG2_TYPE *)&fds, NULL, NULL,
- &tzero) > 0)
- {
- int rc = read(fileno(smtp_in), smtp_inbuffer, in_buffer_size);
- if (rc > 0)
- {
- if (rc > 150) rc = 150;
- smtp_inbuffer[rc] = 0;
- log_write(0, LOG_MAIN|LOG_REJECT, "SMTP protocol "
- "synchronization error (input sent without waiting for greeting): "
- "rejected connection from %s input=\"%s\"", host_and_ident(TRUE),
- string_printing(smtp_inbuffer));
- smtp_printf("554 SMTP synchronization error\r\n");
- return FALSE;
- }
- }
+ log_write(0, LOG_MAIN|LOG_REJECT, "SMTP protocol "
+ "synchronization error (input sent without waiting for greeting): "
+ "rejected connection from %s input=\"%s\"", host_and_ident(TRUE),
+ string_printing(smtp_inptr));
+ smtp_printf("554 SMTP synchronization error\r\n");
+ return FALSE;
}
/* Now output the banner */
spf_init(sender_helo_name, sender_host_address);
#endif
- /* Apply an ACL check if one is defined */
+ /* Apply an ACL check if one is defined; afterwards, recheck
+ synchronization in case the client started sending in a delay. */
if (acl_smtp_helo != NULL)
{
host_build_sender_fullhost(); /* Rebuild */
break;
}
+ else if (!check_sync()) goto SYNC_FAILURE;
}
/* Generate an OK reply. The default string includes the ident if present,
}
}
- /* Apply an ACL check if one is defined, before responding */
+ /* Apply an ACL check if one is defined, before responding. Afterwards,
+ when pipelining is not advertised, do another sync check in case the ACL
+ delayed and the client started sending in the meantime. */
- rc = (acl_smtp_mail == NULL)? OK :
- acl_check(ACL_WHERE_MAIL, NULL, acl_smtp_mail, &user_msg, &log_msg);
+ if (acl_smtp_mail == NULL) rc = OK; else
+ {
+ rc = acl_check(ACL_WHERE_MAIL, NULL, acl_smtp_mail, &user_msg, &log_msg);
+ if (rc == OK && !pipelining_advertised && !check_sync())
+ goto SYNC_FAILURE;
+ }
if (rc == OK || rc == DISCARD)
{
}
/* If the MAIL ACL discarded all the recipients, we bypass ACL checking
- for them. Otherwise, check the access control list for this recipient. */
+ for them. Otherwise, check the access control list for this recipient. As
+ there may be a delay in this, re-check for a synchronization error
+ afterwards, unless pipelining was advertised. */
- rc = recipients_discarded? DISCARD :
- acl_check(ACL_WHERE_RCPT, recipient, acl_smtp_rcpt, &user_msg, &log_msg);
+ if (recipients_discarded) rc = DISCARD; else
+ {
+ rc = acl_check(ACL_WHERE_RCPT, recipient, acl_smtp_rcpt, &user_msg,
+ &log_msg);
+ if (rc == OK && !pipelining_advertised && !check_sync())
+ goto SYNC_FAILURE;
+ }
/* The ACL was happy */
break;
}
+ /* If there is an ACL, re-check the synchronization afterwards, since the
+ ACL may have delayed. */
+
if (acl_smtp_predata == NULL) rc = OK; else
{
enable_dollar_recipients = TRUE;
rc = acl_check(ACL_WHERE_PREDATA, NULL, acl_smtp_predata, &user_msg,
&log_msg);
enable_dollar_recipients = FALSE;
+ if (rc == OK && !check_sync()) goto SYNC_FAILURE;
}
if (rc == OK)
else
done = smtp_handle_acl_fail(ACL_WHERE_PREDATA, rc, user_msg, log_msg);
-
break;
case BADSYN_CMD:
+ SYNC_FAILURE:
if (smtp_inend >= smtp_inbuffer + in_buffer_size)
smtp_inend = smtp_inbuffer + in_buffer_size - 1;
c = smtp_inend - smtp_inptr;
git://git.exim.org / exim.git / blobdiff