+ (text-loop (conc text text-line "\n")))))
+ (message-user-set! msg (smtp-session 'user))
+ (message-password-set! msg (smtp-session 'password))
+ (smtp-session 'send "250 ok")
+ (loop (make-empty-message) (cons msg received-messages)))
+ ((smtp-command? "quit" line)
+ (smtp-session 'send "221 closing transmission channel")
+ received-messages)
+ ((string=? "" (string-trim line))
+ (loop msg received-messages))
+ (else
+ (smtp-session 'send "502 command not implemented")
+ (loop msg received-messages)))))))
+
+
+;;; Sending/Delivering messages
+;;
+
+(define (deliver-messages config messages)
+ (print "**** Attempting delivery of " (length messages) " mail items.")
+ (filter (lambda (msg) (not (deliver-message msg config)))
+ messages))
+
+(define (deliver-message msg config)
+ (print "From: " (message-from msg))
+ (print "To: " (message-to msg))
+ (condition-case
+ (let* ((local-addresses (get-local-addresses config))
+ (dest (assoc (message-to msg) local-addresses))
+ (orig (assoc (message-from msg) local-addresses)))
+ (cond
+ (dest
+ (let ((dest-dir (cadr dest)))
+ (deliver-message-local msg dest-dir)))
+ (orig
+ (let ((password (caddr orig)))
+ (if (and (string=? (conc "<" (message-user msg) "@" (config-host config) ">")
+ (message-from msg))
+ password
+ (string=? (message-password msg) password))
+ (deliver-message-remote msg config)
+ (begin
+ (print "* REMOTE DELIVERY NOT ALLOWED (auth failure)")
+ #t))))
+ (else
+ (print "* REMOTE DELIVERY REJECTED (relay forbidden)")
+ #t)))
+ (o (exn)
+ (print "* DELIVERY FAILED")
+ (print-error-message o)
+ #t)))
+
+
+;; Local delivery
+
+(define (get-local-addresses config)
+ (map (lambda (p) (cons
+ (conc "<" (car p) "@" (config-host config) ">")
+ (cdr p)))
+ (map (lambda (file)
+ (list (pathname-file file) file
+ (let ((password-file (conc file ".auth")))
+ (if (file-exists? password-file)
+ (with-input-from-file password-file read-line)
+ #f))))
+ (filter directory-exists?
+ (glob (conc (config-spool-dir config) "/*"))))))
+
+(define (deliver-message-local msg dest-dir)
+ (with-output-to-file (conc dest-dir "/" (current-seconds))
+ (lambda ()
+ (print (message-text msg))))
+ (print "* MESSAGE DELIVERED (local)")
+ #t)
+
+
+;; Remote delivery
+
+(define (get-domain-from-email email-string)
+ (car (string-split (cadr (string-split email-string "@")) ">")))
+
+;; This is a hack - there's no built-in interface to res_query()
+;; in chicken, so we have to resort to a system call to dig...
+(define (get-mail-server-for-domain domain)
+ (let* ((mx-lines (let-values (((in out id) (process (conc "dig " domain " mx +short"))))
+ (with-input-from-port in read-lines)))
+ (mx-entries (map (lambda (l)
+ (let ((s (string-split l)))
+ (list (string->number (car s))
+ (string-drop-right (cadr s) 1)))) ; remove trailing "."
+ mx-lines))
+ (sorted-mx-entries (sort mx-entries (lambda (e f) (< (car e) (car f))))))
+ (if (null? sorted-mx-entries)
+ domain ; fall-back to email address domain if no mx entries
+ (cadar sorted-mx-entries)))) ; otherwise pick the highest priority server
+
+(define (deliver-message-remote msg config)
+ (let* ((domain (get-domain-from-email (message-to msg)))
+ (mail-server (get-mail-server-for-domain domain)))
+ (print "Attempting delivery to " mail-server)
+ (let-values (((tcp-in tcp-out) (tcp-connect mail-server 25)))
+ (let ((smtp-session (make-outgoing-smtp-session tcp-in tcp-out)))
+ (let ((result (and
+ (smtp-session 'expect "220")
+ (smtp-session 'send "helo " (config-host config))
+ (smtp-session 'expect "250")
+ (smtp-session 'send "mail from:" (message-from msg))
+ (smtp-session 'expect "250")
+ (smtp-session 'send "rcpt to:" (message-to msg))
+ (smtp-session 'expect "250")
+ (smtp-session 'send "data")
+ (smtp-session 'expect "354")
+ (smtp-session 'send (message-text msg))
+ (smtp-session 'send ".")
+ (smtp-session 'expect "250")
+ (smtp-session 'send "quit"))))
+ (close-input-port tcp-in)
+ (close-output-port tcp-out)
+ (print "Connection closed.")
+ (if result
+ (print "* MESSAGE DELIVERED (remote)")
+ (print "* REMOTE DELIVERY FAILED (unexpected server response)"))
+ result)))))
+
+(define ((make-outgoing-smtp-session tcp-in tcp-out) . command)
+ (match command
+ (('expect code)
+ (let ((result (read-line tcp-in)))
+ (print "Expecting " code " got " result)
+ (string-prefix? code result)))
+ (('send strings ...)
+ (print "Sending " (if (> (string-length (car strings)) 30)
+ (string-take (car strings) 30)
+ (car strings)))
+ (let ((processed-string
+ (string-translate* (conc (apply conc strings) "\n")
+ '(("\n" . "\r\n")))))
+ (write-string processed-string #f tcp-out)))))
+
+
+;;; Command line argument parsing
+;;
+
+(define (print-usage progname)
+ (print "Usage:\n"
+ progname " -h/--help\n"
+ progname " [-u/--user UID] [-g/--group GID] hostname [[port [spooldir]]\n"
+ "\n"
+ "The -u and -g options can be used to set the UID and GID of the process\n"
+ "following the creation of the TCP port listener (which often requires root)."))
+
+(define (main)
+ (let ((progname (pathname-file (car (argv))))
+ (config (make-config "" 25 "/var/spool/mail" '() '())))
+ (if (null? (cdr (argv)))
+ (print-usage progname)
+ (let loop ((args (cdr (argv))))
+ (let ((this-arg (car args))
+ (rest-args (cdr args)))
+ (if (string-prefix? "-" this-arg)
+ (cond
+ ((or (equal? this-arg "-u")
+ (equal? this-arg "--user"))
+ (config-user-set! config (string->number (car rest-args)))
+ (loop (cdr rest-args)))
+ ((or (equal? this-arg "-g")
+ (equal? this-arg "--group"))
+ (config-group-set! config (string->number (car rest-args)))
+ (loop (cdr rest-args)))
+ ((or (equal? this-arg "-h")
+ (equal? this-arg "--help"))
+ (print-usage progname))
+ (else
+ (print "Unknown option " this-arg "\n")
+ (print-usage progname)))
+ (begin
+ (config-host-set! config this-arg)
+ (unless (null? rest-args)
+ (config-port-set! config (string->number (car rest-args)))
+ (unless (null? (cdr rest-args))
+ (config-spool-dir-set! config (cadr rest-args))))
+ (run-server config))))))))
+
+(main)
+
+;; (define (test)
+;; (run-server (make-config "localhost" 2525 "spool" '() '())))