X-Git-Url: https://thelambdalab.xyz/gitweb/index.cgi?p=lambdamail.git;a=blobdiff_plain;f=lambdamail.scm;h=fad257d9239b4bb9555a0a2ee4fcf7867375b7fa;hp=1cfe6a07014599108e7c57c75331d240fad452a8;hb=refs%2Fheads%2Fmaster;hpb=928dfdbfd14f5aaca67b5b9ca166f1c62aeac6fb

diff --git a/lambdamail.scm b/lambdamail.scm
index 1cfe6a0..7d37b30 100644
--- a/lambdamail.scm
+++ b/lambdamail.scm
@@ -8,163 +8,398 @@
         (chicken string)
         (chicken pathname)
         (chicken file)
+        (chicken time)
         (chicken time posix)
+        (chicken process)
         (chicken process-context)
+        (chicken process-context posix)
         (chicken condition)
-        srfi-1 srfi-13 matchable)
+        (chicken sort)
+        (chicken random)
+        srfi-1 srfi-13 matchable base64)
 
-(define lambdamail-version "0.0.1")
+(define lambdamail-version "LambdaMail v1.7.0")
 
+(define-record config host port spool-dir user group)
 
-(define-record config
-  host port spool-dir)
-(define-record message to from text helo)
-(define (make-empty-message) (make-message "" "" "" ""))
-
-
-;;; SMTP transactions
-;;
-
-(define ((make-smtp in-port out-port config) type)
-  (if (eq? type 'get-line)
-      (read-line in-port)
-      (write-line (conc
-                   (case type
-                     ((greeting) (conc "220 " (config-host config)
-                                       " LambdaMail v" lambdamail-version))
-                     ((ok) "250 ok")
-                     ((intermediate) "354 intermediate")
-                     ((close) "221 closing transmission channel")
-                     ((not-implemented) "502 command not implemented"))
-                   "\r") out-port)))
+(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 v" lambdamail-version
+    (print lambdamail-version
            " listening on port " (config-port config) " ...")
     (print "(Host name: " (config-host config)
            ", Spool dir: " (config-spool-dir config) ")")
-    (server-loop listener config)))
+    (drop-privs config)
+    (server-loop listener config '())))
 
 
 ;;; Main server loop
 ;;
 
-(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)))
-    (condition-case
-        (let ((smtp (make-smtp in-port out-port config)))
-          (smtp 'greeting)
-          (process-smtp smtp config))
-      (o (exn)
-         (print-error-message o)))
-    (print "Terminating connection.")
-    (close-input-port in-port)
-    (close-output-port out-port)
-    (server-loop listener config)))
-
-;;; SMTP processing 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))))
+
+
+;;; Messages
+;;
+
+(define-record message to from text user password stamp)
+(define-record multi-message tos from text user password stamps)
+(define (make-empty-multi-message) (make-multi-message '() "" "" "" "" '()))
+
+
+;;; Receiving messages
 ;;
 
-(define (process-smtp smtp config)
-  (let loop ((msg (make-empty-message))
-             (line-orig (smtp 'get-line)))
-    (if (string? line-orig)
-        (let ((line (string-downcase line-orig)))
-          (print "got " line)
+(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 ((helo ""))
+    (lambda command
+      (match command
+        (('get-line) (read-line in-port))
+        (('send strings ...) (write-line (conc (apply conc strings) "\r") out-port))
+        (('set-helo! h) (set! helo h))
+        (('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 ((mmsg (make-empty-multi-message))
+             (received-messages '()))
+    (let ((line (smtp-session 'get-line)))
+      (print "got " line)
+      (if (not (string? line))
+          '() ; Don't keep anything on unexpected termination.
           (cond
-           ((string-prefix? "helo" line)
-            (message-helo-set! msg (string-drop line (string-length "helo")))
-            (smtp 'ok)
-            (loop msg (smtp 'get-line)))
-           ((string-prefix? "mail from:" line)
-            (message-from-set! msg (string-drop line (string-length "mail from:")))
-            (smtp 'ok)
-            (loop msg (smtp 'get-line)))
-           ((string-prefix? "rcpt to:" line)
-            (message-to-set! msg (string-drop line (string-length "rcpt to:")))
-            (smtp 'ok)
-            (loop msg (smtp 'get-line)))
-           ((string-prefix? "data" line)
-            (smtp 'intermediate)
-            (let text-loop ((text-line (smtp 'get-line))
-                            (text ""))
-              (if (string=? "." text-line)
-                  (message-text-set! msg text)
-                  (text-loop (smtp 'get-line)
-                             (conc text text-line "\n"))))
-            (deliver-message msg config)
-            (smtp 'ok)
-            (loop (make-empty-message)
-                  (smtp 'get-line)))
-           ((string-prefix? "quit" line)
-            (smtp 'close)
-            'done)
-           ((string=? "" line)
-            (loop msg (smtp 'get-line)))
+           ((smtp-command? "helo" line)
+            (smtp-session 'set-helo! (smtp-command-args "helo" line))
+            (smtp-session 'send "250 ok")
+            (loop mmsg 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 mmsg 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)))
+              (multi-message-user-set! mmsg user)
+              (multi-message-password-set! mmsg password)
+              (print "Attempted login, user: " user ", password: " password)
+              (smtp-session 'send "235 authentication successful")
+              (loop mmsg received-messages)))
+           ((smtp-command? "mail from:" line)
+            (multi-message-from-set! mmsg (smtp-command-args "mail from:" line))
+            (smtp-session 'send "250 ok")
+            (loop mmsg received-messages))
+           ((smtp-command? "rcpt to:" line)
+            (let* ((to (smtp-command-args "rcpt to:" line))
+                   (stamp (make-message-stamp to mmsg config)))
+              (print to)
+              (if (car stamp)
+                  (begin
+                    (multi-message-tos-set! mmsg (cons to (multi-message-tos mmsg)))
+                    (multi-message-stamps-set! mmsg (cons stamp (multi-message-stamps mmsg)))
+                    (smtp-session 'send "250 ok"))
+                  (begin
+                    (smtp-session 'send "551 relay forbidden"))))
+            (loop mmsg received-messages))
+           ((smtp-command? "data" line)
+            (smtp-session 'send "354 intermediate")
+            (let text-loop ((text ""))
+              (let ((text-line (smtp-session 'get-line)))
+                (if (string=? "." text-line)
+                    (multi-message-text-set! mmsg text)
+                    (text-loop (conc text text-line "\n")))))
+            (smtp-session 'send "250 ok")
+            (loop (make-empty-multi-message)
+                  (append (make-single-recipient-messages mmsg smtp-session config)
+                          received-messages)))
+           ((smtp-command? "quit" line)
+            (smtp-session 'send "221 closing transmission channel")
+            received-messages)
+           ((string=? "" (string-trim line))
+            (loop mmsg received-messages))
            (else
-            (smtp 'not-implemented)
-            (loop msg (smtp 'get-line)))))
-        'done)))
+            (smtp-session 'send "502 command not implemented")
+            (loop mmsg received-messages)))))))
+
+(define (make-single-recipient-messages mmsg smtp-session config)
+  (map
+   (lambda (to stamp)
+     (print "making singleton messages: " to " " stamp)
+     (make-message to (multi-message-from mmsg)
+                   (conc "Received: from " (smtp-session 'helo) "\n"
+                         "\tby " (config-host config) "\n"
+                         "\tfor " to ";\n"
+                         "\t" (time-stamp) "\n"
+                         (multi-message-text mmsg))
+                   (multi-message-user mmsg)
+                   (multi-message-password mmsg)
+                   stamp))
+   (multi-message-tos mmsg)
+   (multi-message-stamps mmsg)))
 
 
-;;; Message delivery
+;;; Message stamping and validation
 ;;
 
-(define (get-to-addresses config)
+(define (get-local-addresses config)
   (map (lambda (p) (cons
                     (conc "<" (car p) "@" (config-host config) ">")
                     (cdr p)))
-       (map (lambda (file) (cons (pathname-file file) file))
-            (glob (conc (config-spool-dir config) "/*")))))
+       (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 (remove-angle-brackets addr)
-  (let ((left-idx (substring-index "<" addr))
-        (right-idx (substring-index ">" addr)))
-    (substring addr (+ left-idx 1) right-idx)))
+(define (make-message-stamp to mmsg config)
+  (let* ((local-addresses (get-local-addresses config))
+         (local-dest (assoc to local-addresses))
+         (local-src (assoc (multi-message-from mmsg) local-addresses)))
+    (cond
+     (local-dest
+      (list #t 'local (cadr local-dest)))
+     (local-src
+      (let ((host-password (caddr local-src)))
+        (if (and (string=? (conc "<" (multi-message-user mmsg) "@" (config-host config) ">")
+                           (multi-message-from mmsg))
+                 host-password
+                 (string=? (multi-message-password mmsg) host-password))
+            (list #t 'remote)
+            (begin
+              (print "Provided password " (multi-message-password mmsg))
+              (print "Host password " host-password)
+              (list #f 'remote)))))
+     (else
+      (list #f 'relay)))))
+
+
+;;; 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)
-  (let ((dest (assoc (message-to msg) (get-to-addresses config))))
-    (if dest
-        (begin
-          (with-output-to-file (cdr dest)
-            (lambda ()
-              (print "\nFrom " (remove-angle-brackets (message-from msg)))
-              (print (message-text msg)))
-            #:append)
-          (print "Message DELIVERED:"))
-        (print "Message REJECTED:"))
-    (print " * From: " (message-from msg))
-    (print " * To: " (message-to msg))))
+  (print "From: " (message-from msg))
+  (print "To: " (message-to msg))
+  (condition-case
+    (match (message-stamp msg)
+      ((#t 'local dest-dir) (deliver-message-local msg dest-dir))
+      ((#t 'remote) (deliver-message-remote msg config))
+      ((#f 'remote)
+       (print "* REMOTE DELIVERY NOT ALLOWED (auth failure)")
+       #t)
+      (else
+       (print "* DELIVERY NOT ALLOWED (relay forbidden)")
+       #t))
+    (o (exn)
+       (print "* DELIVERY FAILED")
+       (print-error-message o)
+       #t)))
+
+;; Local delivery
+
+(define unique-file-name
+  (let ((counter 0))
+    (lambda ()
+      (set! counter (modulo (+ counter 1) 1000))
+      (conc (current-seconds) "_" counter))))
+
+(define (deliver-message-local msg dest-dir)
+  (with-output-to-file (conc dest-dir "/" (unique-file-name))
+    (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-servers-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 (map cadr (sort mx-entries (lambda (e f) (< (car e) (car f)))))))
+    (if (null? sorted-mx-entries)
+        (list domain) ; fall-back to email address domain if no mx entries
+        sorted-mx-entries))) ; otherwise pick the highest priority server
+
+(define (deliver-message-remote msg config)
+  (let ((domain (get-domain-from-email (message-to msg))))
+    (let loop ((mail-servers (get-mail-servers-for-domain domain)))
+      (if (null? mail-servers)
+          (begin
+            (print "* REMOTE DELIVERY FAILED (Could not connect to any mail server)")
+            #f)
+          (condition-case
+              (let ((mail-server (car mail-servers)))
+                (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" "5") ;Do not try again on rejects.
+                                   (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))))
+            (o (exn)
+               (print-error-messsage o)
+               (print "* Failed to connect.  Trying next server.")
+               (loop (cdr mail-servers))))))))
+
+(define (or-list l)
+  (fold (lambda (a b) (or a b)) #f l))
+
+(define ((make-outgoing-smtp-session tcp-in tcp-out) . command)
+  (match command
+    (('expect codes ...)
+     (let loop ((result (read-line tcp-in)))
+       (if (and (> (string-length result) 3)
+                (eq? (string-ref result 3) #\-))
+           (loop (read-line tcp-in)) ;status continues on next line
+           (begin
+             (print "Expecting one of " codes " got " result)
+             (or-list (map (lambda (code)
+                             (string-prefix? code result))
+                           codes))))))
+    (('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: " progname " hostname [port [spooldir]]"))
+  (print "Usage:\n"
+         progname " -h/--help\n"
+         progname " -v/--version\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 (print-version)
+  (print lambdamail-version))
 
 (define (main)
   (let ((progname (pathname-file (car (argv))))
-        (args (cdr (argv)))
-        (config (make-config "" 25 "/var/spool/mail")))
-    (if (null? args)
+        (config (make-config "" 25 "/var/spool/mail" '() '())))
+    (if (null? (cdr (argv)))
         (print-usage progname)
-        (begin
-          (config-host-set! config (car args))
-          (unless (null? (cdr args))
-            (config-port-set! config (string->number (cadr args)))
-            (unless (null? (cddr args))
-              (config-spool-dir-set! (caddr args))))
-          (run-server config)))))
+        (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))
+                 ((or (equal? this-arg "-v")
+                      (equal? this-arg "--version"))
+                  (print-version))
+                 (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)
 
-;; (run-server (make-config "thelambdalab.xyz" 2525 "/var/spool/mail"))
+;; (define (test)
+;;   (run-server (make-config "localhost" 2525 "spool" '() '())))
+
+;; (test)