(chicken string)
(chicken pathname)
(chicken file)
+ (chicken time)
(chicken time posix)
- srfi-1 srfi-13 matchable)
+ (chicken process)
+ (chicken process-context)
+ (chicken process-context posix)
+ (chicken condition)
+ (chicken sort)
+ srfi-1 srfi-13 matchable base64)
-(define lambdamail-version "0.0.1")
+(define lambdamail-version "LambdaMail v1.0.0")
-(define-record config port)
-(define-record message to from text helo)
-(define (make-empty-message) (make-message "" "" "" ""))
+(define-record config host port spool-dir user group)
+(define-record message to from text user password)
+(define (make-empty-message) (make-message "" "" "" "" ""))
+
+(define (time-stamp)
+ (time->string (seconds->local-time) "%d %b %Y %T %z"))
+
+
+;;; Server initialization
+;;
+
+(define (drop-privs config)
+ (let ((uid (config-user config))
+ (gid (config-group config)))
+ (if (not (null? gid)) ; Group first, since only root can switch groups.
+ (set! (current-group-id) gid))
+ (if (not (null? uid))
+ (set! (current-user-id) uid))))
(define (run-server config)
(set-buffering-mode! (current-output-port) #:line)
(let ((listener (tcp-listen (config-port config) 10 "::")))
- (print "LambdaMail listening on port " (config-port config) " ...")
- (server-loop listener config)))
-
-(define (server-loop listener config)
- (let-values (((in-port out-port) (tcp-accept listener)))
- (let-values (((local-ip remote-ip) (tcp-addresses in-port)))
- (print "Accepted connection from " remote-ip " on " (seconds->string)))
- (write-line (conc "Welcome to lambamail v" lambdamail-version) out-port)
- (process-smtp in-port out-port)
- (print "Connection terminated.")
- (close-input-port in-port)
- (close-output-port out-port))
- (server-loop listener config))
-
-(define (smtp-reply reply out-port)
- (write-line (conc reply "\r\n") out-port))
-
-(define (smtp-ok out-port)
- (smtp-reply "250 OK" out-port))
-
-(define (smtp-close out-port)
- (smtp-reply "221 Closing transmission channel" out-port))
-
-(define (smtp-no out-port)
- (smtp-reply "502 Command not implemented" out-port))
-
-(define (process-smtp in-port out-port)
+ (print lambdamail-version
+ " listening on port " (config-port config) " ...")
+ (print "(Host name: " (config-host config)
+ ", Spool dir: " (config-spool-dir config) ")")
+ (drop-privs config)
+ (server-loop listener config '())))
+
+
+;;; Main server loop
+;;
+
+(define (server-loop listener config undelivered-messages)
+ (let* ((messages (append (receive-messages listener config) undelivered-messages)))
+ (server-loop listener config (deliver-messages config messages))))
+
+
+;;; Receiving messages
+;;
+
+(define (receive-messages listener config)
+ (let ((messages '()))
+ (print "*** Waiting for incoming mail")
+ (let-values (((in-port out-port) (tcp-accept listener)))
+ (let-values (((local-ip remote-ip) (tcp-addresses in-port)))
+ (print "Accepted connection from " remote-ip " on " (time-stamp)))
+ (condition-case
+ (set! messages (process-smtp (make-smtp-session in-port out-port config) config))
+ (o (exn)
+ (print-error-message o)))
+ (print "Terminating connection.")
+ (close-input-port in-port)
+ (close-output-port out-port))
+ messages))
+
+(define (make-smtp-session in-port out-port config)
+ (let ((user "")
+ (password "")
+ (helo ""))
+ (lambda command
+ (match command
+ (('get-line) (read-line in-port))
+ (('send strings ...) (write-line (conc (apply conc strings) "\r") out-port))
+ (('set-user! u) (set! user u))
+ (('set-password! p) (set! password p))
+ (('set-helo! h) (set! helo h))
+ (('user) user)
+ (('password) password)
+ (('helo) helo)))))
+
+(define (smtp-command? cmd-string input-string)
+ (string-prefix? cmd-string (string-downcase input-string)))
+
+(define (smtp-command-args cmd-string input-string)
+ (if (> (string-length input-string) (string-length cmd-string))
+ (string-trim (string-drop input-string (string-length cmd-string)))
+ ""))
+
+(define (process-smtp smtp-session config)
+ (smtp-session 'send "220 " (config-host config) " " lambdamail-version)
(let loop ((msg (make-empty-message))
- (line (string-downcase (read-line in-port))))
- (cond
- ((string-prefix? "helo" line)
- (message-helo-set! msg (string-drop line (string-length "helo")))
- (smtp-ok out-port)
- (loop msg (string-downcase (read-line in-port))))
- ((string-prefix? "mail from:" line)
- (message-from-set! msg (string-drop line (string-length "mail from:")))
- (smtp-ok out-port)
- (loop msg (string-downcase (read-line in-port))))
- ((string-prefix? "rcpt to:" line)
- (message-to-set! msg (string-drop line (string-length "rcpt to:")))
- (smtp-ok out-port)
- (loop msg (string-downcase (read-line in-port))))
- ((string-prefix? "data" line)
- (let text-loop ((text-line (read-line in-port))
- (text ""))
- (print "Received '" text-line "'")
- (if (string=? "." text-line)
- (message-text-set! msg text)
- (text-loop (read-line in-port)
- (conc text text-line))))
- (deliver-message msg)
- (smtp-ok out-port)
- (loop (make-empty-message)
- (string-downcase (read-line in-port))))
- ((string-prefix? "quit" line)
- (smtp-close out-port)
- 'done)
- (else
- (smtp-no out-port)))))
-
-(define (deliver-message msg)
- (print "Message delivered:")
- (print " * From: " (message-from msg))
- (print " * To: " (message-to msg))
- (print " * Text: " (message-text msg)))
-
-(define (test)
- (run-server (make-config 2525)))
-
-(test)
+ (received-messages '()))
+ (let ((line (smtp-session 'get-line)))
+ (when (string? line)
+ (print "got " line)
+ (cond
+ ((smtp-command? "helo" line)
+ (smtp-session 'set-helo! (smtp-command-args "helo" line))
+ (smtp-session 'send "250 ok")
+ (loop msg received-messages))
+ ((smtp-command? "ehlo" line)
+ (smtp-session 'set-helo! (smtp-command-args "helo" line))
+ (smtp-session 'send
+ "250-" (config-host config)
+ " Hello " (smtp-command-args "ehlo" line))
+ (smtp-session 'send "250 AUTH PLAIN")
+ ;; (smtp-session 'send "250 STARTTLS")
+ (loop msg received-messages))
+ ((smtp-command? "auth plain" line)
+ (let* ((auth-string (smtp-command-args "auth plain" line))
+ (auth-decoded (base64-decode auth-string))
+ (auth-list (string-split auth-decoded "\x00"))
+ (user (car auth-list))
+ (password (cadr auth-list)))
+ (smtp-session 'set-user! user)
+ (smtp-session 'set-password! password)
+ (print "Attempted login, user: " user ", password: " password)
+ (smtp-session 'send "235 authentication successful")
+ (loop msg received-messages)))
+ ((smtp-command? "mail from:" line)
+ (message-from-set! msg (smtp-command-args "mail from:" line))
+ (smtp-session 'send "250 ok")
+ (loop msg received-messages))
+ ((smtp-command? "rcpt to:" line)
+ (message-to-set! msg (smtp-command-args "rcpt to:" line))
+ (smtp-session 'send "250 ok")
+ (loop msg received-messages))
+ ((smtp-command? "data" line)
+ (smtp-session 'send "354 intermediate")
+ (let text-loop ((text (conc "Received: from " (smtp-session 'helo) "\n"
+ "\tby " (config-host config) "\n"
+ "\tfor " (message-to msg) ";\n"
+ "\t" (time-stamp) "\n")))
+ (let ((text-line (smtp-session 'get-line)))
+ (if (string=? "." text-line)
+ (message-text-set! msg text)
+ (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" '() '())))
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