607 lines
22 KiB
Scheme
607 lines
22 KiB
Scheme
;;; SMTP client code -*- Scheme -*-
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;;; Copyright (c) 1995 by Brian D. Carlstrom and Olin Shivers.
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;;; <bdc@ai.mit.edu>, <shivers@lcs.mit.edu>
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;;;
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;;; See rfc821: /ftp@ftp.internic.net:/rfc/rfc821.txt
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;;; External dependencies and non-R4RS'isms
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;;; system-name user-login-name (for high-level SENDMAIL proc)
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;;; receive values (MV return)
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;;; write-string read-string/partial (scsh I/O procs)
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;;; force-output
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;;; scsh's socket module
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;;; :optional
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;;; error
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;;; switchq (Conditional macro)
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;;; ? (COND)
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;;; read-crlf-line write-crlf
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;;; \n \r in strings (Not R4RS)
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;;; SMTP protocol procedures tend to return two values:
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;;; - CODE The integer SMTP reply code returned by server for the transaction.
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;;; - TEXT A list of strings -- the text messages tagged by the code.
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;;; The text strings have the initial code numerals and the terminating
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;;; cr/lf's stripped. Codes in the range [1,399] are sucess codes; codes
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;;; in the range [400,599] are error codes; codes >= 600 are not part
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;;; of the official SMTP spec. This module uses codes >= 600 to indicate
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;;; extra-protocol errors. There are two of these:
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;;; - 600 Server reply could not be parsed.
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;;; The server sent back some sort of incomprehensible garbage reply.
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;;; - 621 Premature EOF while reading server reply.
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;;; The server shut down in the middle of a reply.
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;;; A list of the official protocol return codes is appended at the end of
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;;; this file.
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;;; These little cover functions are trivial packagings of the protocol.
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;;; You could write your own to handle, e.g., mailing a message to a list
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;;; of addresses.
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;;; This is broken -- the (SYSTEM-NAME) proc returns a local name, not a
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;;; useful Internet host name. How do we do that?
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;;; (sendmail to-list body [host])
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;;; Mail message to recipients in list TO-LIST. Message handed off to server
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;;; running on HOST; default is the local host. Returns two values: code and
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;;; text-list. However, if only problem with message is that some recipients
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;;; were rejected, sendmail sends to the rest of the recipients, and the
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;;; partial-success return is [700 loser-alist] where loser-alist
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;;; is a list whose elements are of the form (loser-recipient code . text) --
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;;; that is, for each recipient refused by the server, you get the error
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;;; data sent back for that guy. The success check is (< code 400).
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;;;
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;;; BODY is a string or an input port.
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(define (sendmail to-list body . maybe-host)
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(call-with-current-continuation
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(lambda (bailout)
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(let ((local (system-name))
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(socket (smtp/open (:optional maybe-host "localhost"))))
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(receive (code text) (smtp-transactions socket ; Do prologue.
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(smtp/helo socket local)
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(smtp/mail socket (string-append (user-login-name)
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"@" local)))
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(if (>= code 400) (values code text) ; error
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;; Send over recipients and collect the losers.
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(let ((losers (filter-map
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(lambda (to)
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(receive (code text) (smtp/rcpt socket to)
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(and (>= code 400) ; Error
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(cond ((>= code 600)
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(smtp/quit socket)
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(bailout code text))
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(else `(,to ,code ,@text))))))
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to-list)))
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;; Send the message body and wrap things up.
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(receive (code text) (smtp-transactions socket
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(smtp/data socket body)
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(smtp/quit socket))
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(if (and (< code 400) (null? losers))
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(values code text)
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(values 700 losers))))))))))
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;;; Trivial utility -- like map, but filter out #f's.
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(define (filter-map f lis)
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(let lp ((ans '()) (lis lis))
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(if (pair? lis)
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(lp (? ((f (car lis)) => (lambda (val) (cons val ans)))
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(else ans))
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(cdr lis))
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(reverse ans))))
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(define (%sendmail from local-host to dest-host message)
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(let ((socket (smtp/open dest-host)))
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(smtp-transactions socket
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(smtp/helo socket local-host)
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(smtp/mail socket from)
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(smtp/rcpt socket to)
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(smtp/data socket message)
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(smtp/quit socket))))
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;;; EXPN, VRFY, MAIL-HELP
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;;; These three are simple queries of the server.
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(define (smtp-query socket query arg)
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(receive (code text)
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(smtp-transactions socket
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(smtp/helo socket (system-name))
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(query socket arg))
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(if (not (or (= code 421) (= code 221)))
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(smtp/quit socket))
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(values code text)))
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(define (expn name host)
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(smtp-query (smtp/open host) smtp/expn name))
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(define (vrfy name host)
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(smtp-query (smtp/open host) smtp/vrfy name))
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(define (mail-help host . details)
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(smtp-query (smtp/open host) smtp/help (apply string-append details)))
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;;; (smtp-transactions socket ?transaction1 ...)
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;;; (smtp-transactions/no-close socket ?transaction1 ...)
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;;; These macros make it easy to do simple sequences of SMTP commands.
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;;;
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;;; Evaluate a series of expressions ?transaction1, ?transaction2, ...
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;;; - Each expression should perform an SMTP transaction,
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;;; and return two values:
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;;; + CODE (the integer reply code)
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;;; + TEXT (list of strings that came with the reply).
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;;;
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;;; - If the transaction's reply code is 221 or 421 (meaning the socket has
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;;; been closed), then the transaction sequence is is aborted, and the
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;;; SMTP-TRANSACTIONS form returns the CODE and TEXT values for the current
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;;; transaction.
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;;;
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;;; - If the reply code is an error code (in the four- or five-hundred range),
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;;; the transaction sequence is aborted, and the fatal transaction's CODE
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;;; and TEXT values are returned. SMTP-TRANSACTIONS will additionally
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;;; close the socket for you; SMTP-TRANSACTIONS/NO-CLOSE will not.
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;;;
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;;; - If the transaction is the last in the transaction sequence,
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;;; its CODE and TEXT values are returned.
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;;;
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;;; - Otherwise, we throw away the current CODE and TEXT values, and
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;;; proceed to the next transaction.
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;;;
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;;; Since SMTP-TRANSACTIONS closes the socket whenever it aborts a sequence,
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;;; an SMTP-TRANSACTIONS form terminated with an (smtp/quit socket) transaction
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;;; will always close the socket.
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;;;
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;;; If the socket should be kept open in the case of an abort, use
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;;; SMTP-TRANSACTIONS/NO-CLOSE.
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;;;
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;;; We abort sequences if a transaction results in a 400-class error code.
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;;; So, a sequence mailing a message to five people, with 5 RCPT's, would
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;;; abort if the mailing address for one of these people was wrong, rather
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;;; than proceeding to mail the other four. This may not be what you want;
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;;; if so, you'll have to roll your own.
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(define-syntax smtp-transactions
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(syntax-rules ()
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((smtp-transactions socket ?T1 ?T2 ...)
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(let ((s socket))
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(receive (code text) (smtp-transactions/no-close s ?T1 ?T2 ...)
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(if (<= 400 code) (smtp/quit s))
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(values code text))))))
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(define-syntax smtp-transactions/no-close
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(syntax-rules ()
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((smtp-transactions/no-close socket ?T1 ?T2 ...)
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;; %smtp-transactions/no-close replicates the socket argument,
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;; so we have to force it to be a variable.
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(let ((s socket))
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(%smtp-transactions/no-close s ?T1 ?T2 ...)))))
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;;; SOCKET must be a variable, hence replicable.
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(define-syntax %smtp-transactions/no-close
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(syntax-rules ()
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((%smtp-transactions/no-close socket ?T1 ?T2 ?T3 ...)
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(receive (code text) ?T1
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(if (or (= code 221)
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(= code 421) ; Redundant, I know.
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(<= 400 code))
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(values code text)
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(%smtp-transactions/no-close socket ?T2 ?T3 ...))))
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((%smtp-transactions/no-close socket ?T1)
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?T1)))
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;;; I can't make this nested definition work. I'm not enough of a macro stud.
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;(define-syntax smtp-transactions/no-close
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; (syntax-rules ()
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; ((smtp-transactions/no-close socket ?T1 ...)
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; (letrec-syntax ((%smtp-transactions/no-close
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; (syntax-rules ()
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;
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; ((%smtp-transactions/no-close socket ?T1 ?T2 ...)
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; (receive (code text) ?T1
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; (if (or (= code 221)
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; (= code 421) ; Redundant, I know.
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; (<= 400 code))
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; (values code text)
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; (%smtp-transactions/no-close socket ?T2 ...))))
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;
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; ((%smtp-transactions/no-close socket ?T1)
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; ?T1))))
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;
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; ;; %smtp-transactions/no-close replicates the socket argument,
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; ;; so we have to force it to be a variable.
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; (let ((s socket))
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; (%smtp-transactions/no-close s ?T1 ...))))))
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;;; The basics of the protocol
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(define (nullary-smtp-command command)
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(lambda (socket)
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(let ((port (socket:outport socket)))
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(write-string command port)
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(write-crlf port))
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(handle-smtp-reply socket)))
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(define (unary-smtp-command command)
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(lambda (socket data)
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(let ((port (socket:outport socket)))
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(write-string command port)
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(display #\space port)
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(write-string data port)
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(write-crlf port))
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(handle-smtp-reply socket)))
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(define (smtp/open host . maybe-port)
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(let ((sock (socket-connect protocol-family/internet socket-type/stream host
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(:optional maybe-port "smtp"))))
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(receive (code text) (handle-smtp-reply sock)
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(if (< code 400) sock
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(error "SMTP socket-open server-reply error" sock code text)))))
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;; HELLO <local-hostname>
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(define smtp/helo (unary-smtp-command "HELO"))
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;; MAIL FROM: <sender-address>
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(define smtp/mail (unary-smtp-command "MAIL FROM:"))
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;; RECIPIENT TO: <destination-address>
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(define smtp/rcpt (unary-smtp-command "RCPT TO:"))
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;; DATA
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(define smtp/data
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(let ((send-DATA-msg (nullary-smtp-command "DATA")))
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(lambda (socket message) ; MESSAGE is a string or an input port.
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(receive (code text) (send-DATA-msg socket)
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(if (>= code 400) (values code text) ; Error.
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;; We got a positive acknowledgement for the DATA msg,
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;; now send the message body.
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(let ((p (socket:outport socket)))
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(? ((string? message)
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(receive (data last-char) (smtp-stuff message #f)
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(write-string data p)))
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((input-port? message)
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(let lp ((last-char #f))
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(? ((read-string/partial 1024 message) =>
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(lambda (chunk)
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(receive (data last-char)
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(smtp-stuff chunk last-char)
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(write-string data p)
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(lp last-char)))))))
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(else (error "Message must be string or input-port.")))
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(write-string "\r\n.\r\n" p)
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(force-output p)
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(handle-smtp-reply socket)))))))
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;; SEND FROM: <sender-address>
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(define smtp/send (unary-smtp-command "SEND FROM:"))
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;; SEND OR MAIL <sender-address>
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(define smtp/soml (unary-smtp-command "SOML FROM:"))
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;; SEND AND MAIL <sender-address>
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(define smtp/saml (unary-smtp-command "SOML SAML:"))
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;; RESET
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(define smtp/rset (nullary-smtp-command "RSET"))
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;; VERIFY <user>
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(define smtp/vrfy (unary-smtp-command "VRFY"))
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;; EXPAND <user>
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(define smtp/expn (unary-smtp-command "EXPN"))
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;; HELP <details>
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(define smtp/help
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(let ((send-help (unary-smtp-command "HELP")))
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(lambda (socket . details)
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(send-help socket (apply string-append details)))))
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;; NOOP
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(define smtp/noop (nullary-smtp-command "NOOP"))
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;; QUIT
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(define smtp/quit
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(let ((quit (nullary-smtp-command "QUIT")))
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(lambda (socket)
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(receive (code text) (quit socket) ; Quit & close socket gracefully.
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(switchq = code
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((221 421))
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(else (close-socket socket))) ; But close in any event.
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(values code text)))))
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;; TURN
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(define smtp/turn (nullary-smtp-command "TURN"))
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;;; Read and handle the reply. Return an integer (the reply code),
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;;; and a list of the text lines that came tagged by the reply code.
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;;; The text lines have the reply-code prefix (first 4 chars) and the
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;;; terminating cr/lf's stripped.
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;;;
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;;; In bdc's analog of this proc, he would read another reply if the code was
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;;; in the one-hundred range (1xx). These codes aren't even used in smtp,
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;;; according to the RFC. So why?
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(define (handle-smtp-reply socket)
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(receive (code text) (read-smtp-reply (socket:inport socket))
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(switchq = code
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((221 421) (close-socket socket))) ; All done.
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(values code text)))
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;;; Read a reply from the SMTP server. Returns two values:
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;;; - CODE Integer. The reply code.
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;;; - TEXT String list. A list of the text lines comprising the reply.
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;;; Each line of text is stripped of the initial reply-code
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;;; numerals (e.g., the first four chars of the reply), and
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;;; the trailing cr/lf. We are in fact generous about what
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;;; we take to be a line -- the protocol requires cr/lf
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;;; terminators, but we'll accept just lf. This appears to
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;;; true to the spirit of the "be strict in what you send,
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;;; and generous in what you accept" Internet protocol philosphy.
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(define (read-smtp-reply port)
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(let lp ((replies '()))
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(let ((ln (read-crlf-line port)))
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(if (eof-object? ln)
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(values 621 (cons "Premature EOF during smtp reply."
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(reverse replies)))
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(receive (code line more?) (parse-smtp-reply ln)
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(let ((replies (cons line replies)))
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(if more? (lp replies)
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(values code (reverse replies)))))))))
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;;; Parse a line of SMTP reply. Return three values:
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;;; CODE integer - the reply code that prefixes the string.
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;;; REST string - the rest of the line.
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;;; MORE? boolean - is there more reply to read (i.e., was the numeric
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;;; reply code terminated by a "-" character?)
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(define (parse-smtp-reply line)
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(if (and (string? line) ; This is all checking
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(> (string-length line) 3) ; to see if the line
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(char-numeric? (string-ref line 0)) ; is properly formatted.
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(char-numeric? (string-ref line 1))
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(char-numeric? (string-ref line 2))
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(let ((c (string-ref line 3)))
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(or (char=? c #\space) (char=? c #\-))))
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(values (string->number (substring line 0 3)) ; It is.
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(substring line 4 (string-length line))
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(char=? (string-ref line 3) #\-))
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(values 600 ; It isn't.
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(string-append "Improperly-formatted smtp reply: " line)
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#f)))
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;;; The message body of a piece of email is terminated by the sequence
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;;; <crlf> <period> <crlf>
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;;; If the message body contains this magic sequence, it has to be escaped.
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;;; We do this by mapping the sequence <lf> <period> to <lf> <period> <period>;
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;;; the SMTP receiver undoes this mapping.
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;;; S is a string to stuff, PCHAR was the character read just before S
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;;; (which matters if it is a line-feed). If S is the first chunk of the entire
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;;; msg, then PCHAR can be #f. Return two values: the stuffed string, and the
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;;; last char in S (or PCHAR if S is empty). The last-char value returned can
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;;; be used as the PCHAR arg for the following call to SMTP-STUFF.
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(define (smtp-stuff s pchar)
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(let* ((slen (string-length s))
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(hits ; Count up all the <lf> <period> seqs in the string.
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(let lp ((count 0)
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(nl? (eqv? pchar #\newline)) ; Was last char a newline?
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(i 0))
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(if (< i slen)
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(let ((c (string-ref s i)))
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(lp (if (and nl? (char=? c #\.)) (+ count 1) count)
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(eq? c #\newline)
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(+ i 1)))
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count))))
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(values (if (zero? hits) s
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;; Make a new string, and do the dot-stuffing copy.
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(let ((ns (make-string (+ hits slen))))
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(let lp ((nl? (eqv? pchar #\newline))
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(i 0) ; S index.
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(j 0)) ; NS index.
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(if (< i slen)
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(let ((c (string-ref s i)))
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(string-set! ns j c)
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(? ((and nl? (char=? c #\.))
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(string-set! ns (+ j 1) #\.)
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(lp #f (+ i 1) (+ j 2)))
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(else (lp (char=? c #\newline) (+ i 1) (+ j 1)))))))
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ns))
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(if (zero? slen) pchar (string-ref s (- slen 1)))))) ; LAST-CHAR
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;;; Reply codes
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;;; This material taken from the RFC.
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;;;
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;;; 1yz Positive Preliminary reply
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;;;
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;;; The command has been accepted, but the requested action
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;;; is being held in abeyance, pending confirmation of the
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;;; information in this reply. The sender-SMTP should send
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;;; another command specifying whether to continue or abort
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;;; the action.
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;;;
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;;; [Note: SMTP does not have any commands that allow this
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;;; type of reply, and so does not have the continue or
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;;; abort commands.]
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;;;
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;;; 2yz Positive Completion reply
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;;;
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;;; The requested action has been successfully completed. A
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;;; new request may be initiated.
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;;;
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;;; 3yz Positive Intermediate reply
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;;;
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;;; The command has been accepted, but the requested action
|
|
;;; is being held in abeyance, pending receipt of further
|
|
;;; information. The sender-SMTP should send another command
|
|
;;; specifying this information. This reply is used in
|
|
;;; command sequence groups.
|
|
;;;
|
|
;;; 4yz Transient Negative Completion reply
|
|
;;;
|
|
;;; The command was not accepted and the requested action did
|
|
;;; not occur. However, the error condition is temporary and
|
|
;;; the action may be requested again. The sender should
|
|
;;; return to the beginning of the command sequence (if any).
|
|
;;; It is difficult to assign a meaning to "transient" when
|
|
;;; two different sites (receiver- and sender- SMTPs) must
|
|
;;; agree on the interpretation. Each reply in this category
|
|
;;; might have a different time value, but the sender-SMTP is
|
|
;;; encouraged to try again. A rule of thumb to determine if
|
|
;;; a reply fits into the 4yz or the 5yz category (see below)
|
|
;;; is that replies are 4yz if they can be repeated without
|
|
;;; any change in command form or in properties of the sender
|
|
;;; or receiver. (E.g., the command is repeated identically
|
|
;;; and the receiver does not put up a new implementation.)
|
|
;;;
|
|
;;; 5yz Permanent Negative Completion reply
|
|
;;;
|
|
;;; The command was not accepted and the requested action did
|
|
;;; not occur. The sender-SMTP is discouraged from repeating
|
|
;;; the exact request (in the same sequence). Even some
|
|
;;; "permanent" error conditions can be corrected, so the
|
|
;;; human user may want to direct the sender-SMTP to
|
|
;;; reinitiate the command sequence by direct action at some
|
|
;;; point in the future (e.g., after the spelling has been
|
|
;;; changed, or the user has altered the account status).
|
|
;;;
|
|
;;;The second digit encodes responses in specific categories:
|
|
;;;
|
|
;;; x0z Syntax -- These replies refer to syntax errors,
|
|
;;; syntactically correct commands that don't fit any
|
|
;;; functional category, and unimplemented or superfluous
|
|
;;; commands.
|
|
;;;
|
|
;;; x1z Information -- These are replies to requests for
|
|
;;; information, such as status or help.
|
|
;;;
|
|
;;; x2z Connections -- These are replies referring to the
|
|
;;; transmission channel.
|
|
;;;
|
|
;;; x3z Unspecified as yet.
|
|
;;;
|
|
;;; x4z Unspecified as yet.
|
|
;;;
|
|
;;; x5z Mail system -- These replies indicate the status of
|
|
;;; the receiver mail system vis-a-vis the requested
|
|
;;; transfer or other mail system action.
|
|
|
|
;;; Complete list (grouped by function)
|
|
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
|
;;; 500 Syntax error, command unrecognized
|
|
;;; [This may include errors such as command line too long]
|
|
;;; 501 Syntax error in parameters or arguments
|
|
;;; 502 Command not implemented
|
|
;;; 503 Bad sequence of commands
|
|
;;; 504 Command parameter not implemented
|
|
;;;
|
|
;;; 211 System status, or system help reply
|
|
;;; 214 Help message
|
|
;;; [Information on how to use the receiver or the meaning of a
|
|
;;; particular non-standard command; this reply is useful only
|
|
;;; to the human user]
|
|
;;;
|
|
;;; 220 <domain> Service ready
|
|
;;; 221 <domain> Service closing transmission channel
|
|
;;; 421 <domain> Service not available,
|
|
;;; closing transmission channel
|
|
;;; [This may be a reply to any command if the service knows it
|
|
;;; must shut down]
|
|
;;;
|
|
;;; 250 Requested mail action okay, completed
|
|
;;; 251 User not local; will forward to <forward-path>
|
|
;;; 450 Requested mail action not taken: mailbox unavailable
|
|
;;; [E.g., mailbox busy]
|
|
;;; 550 Requested action not taken: mailbox unavailable
|
|
;;; [E.g., mailbox not found, no access]
|
|
;;; 451 Requested action aborted: error in processing
|
|
;;; 551 User not local; please try <forward-path>
|
|
;;; 452 Requested action not taken: insufficient system storage
|
|
;;; 552 Requested mail action aborted: exceeded storage allocation
|
|
;;; 553 Requested action not taken: mailbox name not allowed
|
|
;;; [E.g., mailbox syntax incorrect]
|
|
;;; 354 Start mail input; end with <CRLF>.<CRLF>
|
|
;;; 554 Transaction failed
|
|
;;;
|
|
|
|
;;; State diagram
|
|
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
|
;;; CONNECTION ESTABLISHMENT
|
|
;;; S: 220
|
|
;;; F: 421
|
|
;;; HELO
|
|
;;; S: 250
|
|
;;; E: 500, 501, 504, 421
|
|
;;; MAIL
|
|
;;; S: 250
|
|
;;; F: 552, 451, 452
|
|
;;; E: 500, 501, 421
|
|
;;; RCPT
|
|
;;; S: 250, 251
|
|
;;; F: 550, 551, 552, 553, 450, 451, 452
|
|
;;; E: 500, 501, 503, 421
|
|
;;; DATA
|
|
;;; I: 354 -> data -> S: 250
|
|
;;; F: 552, 554, 451, 452
|
|
;;; F: 451, 554
|
|
;;; E: 500, 501, 503, 421
|
|
;;; RSET
|
|
;;; S: 250
|
|
;;; E: 500, 501, 504, 421
|
|
;;; SEND
|
|
;;; S: 250
|
|
;;; F: 552, 451, 452
|
|
;;; E: 500, 501, 502, 421
|
|
;;; SOML
|
|
;;; S: 250
|
|
;;; F: 552, 451, 452
|
|
;;; E: 500, 501, 502, 421
|
|
;;; SAML
|
|
;;; S: 250
|
|
;;; F: 552, 451, 452
|
|
;;; E: 500, 501, 502, 421
|
|
;;; VRFY
|
|
;;; S: 250, 251
|
|
;;; F: 550, 551, 553
|
|
;;; E: 500, 501, 502, 504, 421
|
|
;;; EXPN
|
|
;;; S: 250
|
|
;;; F: 550
|
|
;;; E: 500, 501, 502, 504, 421
|
|
;;; HELP
|
|
;;; S: 211, 214
|
|
;;; E: 500, 501, 502, 504, 421
|
|
;;; NOOP
|
|
;;; S: 250
|
|
;;; E: 500, 421
|
|
;;; QUIT
|
|
;;; S: 221
|
|
;;; E: 500
|
|
;;; TURN
|
|
;;; S: 250
|
|
;;; F: 502
|
|
;;; E: 500, 503
|