Re: pop3.el broken

[Katsumi Yamaoka <yamaoka@jpl.org>]

Let's assume that the following premises are correct.

1. A POP3 server will use only ascii characters to generate a
   timestamp string in its banner greeting, which is described
   in RFC1460.  There is no problem that pop3.el uses the
   coding-system binary and a multibyte buffer to transfer such
   a string from a server.

2. A password string may be either an ascii-only string or a
   string which includes non-ascii characters.  The latter
   should be encoded with a reasonable coding-system before
   passing it to md5bin (which is mentioned below).

   I don't know how to set a non-ascii password using the
   popauth command, and I think the use of a non-ascii password
   is not popular, though.

3. Both a timestamp string and a password string do not contain
   newlines.

4. There is the imaginary function md5bin which will not encode
   a given string.  It can be provided with one of the built-in
   md5, the lisp function md5 and the external process md5 which
   is called with the coding-system binary.

Do you have any doubts?  If none, pop3.el can be modified
something like follows.  It can be simplified if we don't have
to handle to encode a password string.


(defvar pop3-apop-passwd-coding-system nil
  "*Coding system used to encode a non-ascii password for APOP.")

(defvar pop3-md5-binary nil)

(defmacro pop3-make-apop-auth (password)
  "Return a string for the apop authentication corresponding to the value
of `pop3-timestamp' and PASSWORD."
  (if (and nil;(fboundp 'md5)
	   (subrp (symbol-function 'md5)))
      (if (and (featurep 'xemacs)
	       (< (function-max-args 'md5) 4))
	  (if (featurep 'mule)
	      ;; XEmacs 20 with MULE
	      `(let ((pass ,password))
		 (md5 (concat pop3-timestamp
			      (if pop3-apop-passwd-coding-system
				  (encode-coding-string
				   pass pop3-apop-passwd-coding-system)
				pass))))
	    ;; XEmacs 20 without MULE
	    `(md5 (concat pop3-timestamp ,password)))
	(if (featurep 'mule)
	    ;; Emacs 21 or XEmacs 21 with MULE
	    `(let ((pass ,password))
	       (md5 (concat pop3-timestamp
			    (if pop3-apop-passwd-coding-system
				(encode-coding-string
				 pass pop3-apop-passwd-coding-system)
			      pass))
		    nil nil 'binary))
	  ;; XEmacs 21 without MULE
	  `(md5 (concat pop3-timestamp ,password) nil nil
		'binary)))
    (let ((fn '(if (not pop3-md5-binary)
		   (setq pop3-md5-binary
			 (if (condition-case nil
				 (require 'md5)
			       (error nil))
			     'md5
			   (lambda (string)
			     (with-temp-buffer
			       (insert string)
			       (let ((coding-system-for-write 'binary))
				 (call-process-region (point-min) (point-max)
						      pop3-md5-program
						      t (current-buffer))
				 (buffer-substring 1 33)))))))))
      (if (featurep 'mule)
	  `(let ((pass ,password))
	     ,fn
	     (funcall pop3-md5-binary
		      (concat pop3-timestamp
			      (if pop3-apop-passwd-coding-system
				  (encode-coding-string
				   pass pop3-apop-passwd-coding-system)
				pass))))
	`(progn
	   ,fn
	   (funcall pop3-md5-binary (concat pop3-timestamp ,password)))))))

(defun pop3-apop (process user)
[...]
	;;(let ((hash (pop3-md5 (concat pop3-timestamp pass))))
	(let ((hash (pop3-make-apop-auth pass)))
-- 
Katsumi Yamaoka <yamaoka@jpl.org>