Add preauth.c

 2007-12-03  Sergey Poznyakoff  <gray@gnu.org.ua>
 
+	* NEWS: Update.
 	* gnulib.modules: Add des. Sort lines.
 	* imap4d/Makefile.am (imap4d_SOURCES): Add preauth.c
+	* imap4d/preauth.c: New file.
 	* imap4d/authenticate.c (imap4d_authenticate): Use
 	imap4d_session_setup.
 	* imap4d/imap4d.c (imap4d_session_setup)

-GNU mailutils NEWS -- history of user-visible changes. 2007-11-30
+GNU mailutils NEWS -- history of user-visible changes. 2007-12-03
 Copyright (C) 2002, 2003, 2004, 2005, 2006, 2007 Free Software Foundation, Inc.
 See the end of file for copying conditions.
 
@@ -146,6 +146,33 @@ Previous versions incorrectly understood such an URL as `a/b'
 
 * Fixed APOP handling.
 
+* imap4d supports PREAUTH mode.
+
+Three mechanisms are provided for authentifying the connection in
+PREAUTH mode:
+
+ 1. stdio - PREAUTH mode is enabled automatically if imap4d is started
+    from command line in interactive mode (-i command line
+    option). The current login name is used as the user name.
+
+ 2. ident - The remote machine is asked about the requester identity
+    using the identification protocol (RFC 1413). Both plaintext and
+    DES encrypted replies are understood.
+
+ 3. prog - Imap4d invokes an external program to authenticate the
+    connection. Four arguments are supplied to the program:
+
+      1) Remote IP address in dotted-quad notation;
+      2) Remote port number;
+      3) Local IP address (currently "0.0.0.0");
+      4) Local port number.
+
+    If the connection is authenticated, the program should print the
+    user name, followed by a newline character, on its standard
+    output and exit with code 0.
+
+    Otherwise, it shoud exit with a non-zero exit code.
+
 * Remove v0.6 compatibility layer.