Source Code 1992 March/Source_Code_CD-ROM_Walnut_Creek_March_1992.iso/usenet/altsrcs/3/3409

Internet Message Format | 1991-05-24 | 10.5 KB

From: [e-mail] (Johan Vromans)
Newsgroups: alt.sources,gnu.emacs.gnus,gnu.emacs.sources
Subject: MD4 support for GNU Emacs GNUS version 1.4
Message-ID: <[e-mail]>
Date: 22 May 91 14:21:50 GMT


This release
  * includes instructions for use
  * corrects the inclusion of the .signature file
  * provides the necessary 'add-hook' function
  * includes a decent README

---- Cut Here and feed the following to sh ----
#!/bin/sh
# This is md4, a shell archive (produced by shar 3.49)
# To extract the files from this archive, save it to a file, remove
# everything above the "!/bin/sh" line above, and type "sh file_name".
#
# made 05/22/1991 12:18 UTC by [e-mail]
# Source directory /u1/users/jv/elisp/src/md4
#
# existing files will NOT be overwritten unless -c is specified
#
# This shar contains:
# length  mode       name
# ------ ---------- ------------------------------------------
#   1318 -rw-r--r-- README
#   5865 -r--r--r-- md4.el
#    647 -rw-r--r-- add-hook.el
#
if test -r _shar_seq_.tmp; then
    echo 'Must unpack archives in sequence!'
    echo Please unpack part `cat _shar_seq_.tmp` next
    exit 1
fi
# ============= README ==============
if test -f 'README' -a X"$1" != X"-c"; then
    echo 'x - skipping README (File already exists)'
    rm -f _shar_wnt_.tmp
else
> _shar_wnt_.tmp
echo 'x - extracting README (Text)'
sed 's/^X//' << 'SHAR_EOF' > 'README' &&
This is MD4 signature support for the GNU Emacs GNUS newsreader.
X
MD4 can be used to apply a fingerprint on an article posted to USENET that,
when run through a verification tool, will tell you whether an article has
been corrupted. It does not detect or prevent complete replacement of the
article. Think of MD4 as a super-strong checksum.
X
This package allows for automatic insertion of the MD4 signature in
news articles posted with GNUS, and the automatic verification of MD4
signatures in articles when retrieved. The main source file, 'md4.el'
is heavily commented on usage and customization.
X
As stated in RFC1186:
X
X   This  note describes the MD4 message digest algorithm.  The algorithm
X   takes as input an input message of arbitrary length and produces as
X   output a 128-bit "fingerprint" or "message digest" of the input.  It
X   is conjectured that it is computationally infeasible to produce two
X   messages having the same message digest, or to produce any message
X   having a given prespecified target message digest.  The MD4 algorithm
X   is thus ideal for digital signature applications, where a large file
X   must be "compressed" in a secure manner before being signed with the
X   RSA public-key cryptosystem.
X
Please read RFC1186 for more details about MD4.
X
Have fun,
X
X    Johan Vromans <[e-mail]>
SHAR_EOF
chmod 0644 README ||
echo 'restore of README failed'
Wc_c="`wc -c < 'README'`"
test 1318 -eq "$Wc_c" ||
    echo 'README: original size 1318, current size' "$Wc_c"
rm -f _shar_wnt_.tmp
fi
# ============= md4.el ==============
if test -f 'md4.el' -a X"$1" != X"-c"; then
    echo 'x - skipping md4.el (File already exists)'
    rm -f _shar_wnt_.tmp
else
> _shar_wnt_.tmp
echo 'x - extracting md4.el (Text)'
sed 's/^X//' << 'SHAR_EOF' > 'md4.el' &&
;; md4.el -- MD4 support for GNUS
;;
;; SCCS Status     : @(#)@ md4    1.4
;; Author          : Johan Vromans
;; Created On      : Sat May 11 09:10:04 1991
;; Last Modified By: Johan Vromans
;; Last Modified On: Wed May 22 13:36:56 1991
;; Update Count    : 11
;; Status          : OK
;;
;; This file defines functions to calculate a MD4 signature, add
;; it to outgoing postings, and validate it on incoming postings.
;;
;; It uses "gnus-Inews-article-hook", called by GNUS just before passing
;; the articel to inews, to install the signature.
;;
;; "gnus-Article-prepare-hook" is used to validate the signature on
;; an article if you read it.
;;
;; Advised usage: load this file after loading gnus, e.g. from the
;; gnus-Startup-hook.
;; You also can do this explicitly:
;;
;;      (load "gnus" nil t)
;;    (load "md4" t nil)    ; optional
;;    (gnus)
;;
;; This file, if useful, is covered by the GPL.
;;
;;    Johan Vromans <[e-mail]>
X
;; HISTORY
;; 22-May-1991        Johan Vromans
;;    Enhanced comments and improved customization.
;;    Added provide 'md4 and require 'add-hook.
;;    Normalized .signature file inclusion.
X
(provide 'md4)
(or (fboundp 'add-hook)
X    (require 'add-hook))    ; by Dan LaLiberte <[e-mail]>
X
;; Customizations
;;
;; This function only uses program md4; it doesn't need md4hash nor
;; md4check.
;; The md4 programs can be retrieved from your nearest comp.sources.misc
;; archive site. Contact the moderator of comp.sources.misc for details.
;;
(defvar md4-command "md4"
X  "*Where to find the md4 program. This program should be in your PATH.")
X
(defvar md4-insertion t
X  "*Controls MD4 signature insertion. If nil, no signature is inserted.")
X
(defvar md4-validation 1
X  "*Controls MD4 signature validation. If nil, no validation is
X  performed. If t, validation is performed, and failures are reported.
X  Any other value causes validation to be performed, and failures as
X  well as successes to be reported.")
X
;; If the variable gnus-signature-file is not null, GNUS will append
;; this file to the article before posting. If null, your .signature
;; is supposed to be added by your news system. In this case, the md4
;; calculation will temporary insert the signature to make sure a
;; correct checksum is calculated.
;; You may have to change the md4-signature-separator if needed.
X
(defvar md4-signature-separator "-- \n"
X  "*If your news posting system appends your .signature file for you,
X  then set this variable to the separator string used. In this case,
X  the signature will be added on behalf of the calculation of the MD4
X  checksum, and removed before the article is transferred to the news
X  system.
X  In general, set it to "--\\n" or "-- \\n" for classic B-news or C-news.")
X
;;
;; End of customizations
;;
X
(defvar md4-signature-header "X-Md4-Signature")
X
;; Hook definitions and insertions.
X
(add-hook 'gnus-Inews-article-hook 'md4-add-signature)
(add-hook 'gnus-Article-prepare-hook 'md4-validate-signature)
;;
;; Calcuates the MD4 signature for the article to be posted, which
;; is assumed to be in the current buffer.
;;
(defun md4-add-signature ()
X  "Adds a MD4-signature to the article being posted. Must be called
from gnus-Inews-article-hook."
X  (interactive)
X
X  (if (null md4-insertion)
X      nil
X    (let (start-of-body end-of-body sigfile)
X
X      ;; .signature handling. may be system specific
X      (goto-char (point-max))
X      (setq end-of-body (point-marker))
X      (if (not gnus-signature-file)    ;skip if gnus-sig set
X      (if (file-exists-p
X           (setq sigfile (expand-file-name "~/.signature")))
X          (progn
X        (insert md4-signature-separator)
X        (insert-file sigfile))
X        (setq sigfile nil)))    ;signal 'no file'
X
X      (goto-char (point-min))
X      (search-forward "\n\n")
X      (setq start-of-body (point-marker))    ; remember where
X
X      ;; Run md4 and add the signature.
X      (forward-line -1)
X      (insert md4-signature-header ": ")
X      (insert (md4-signature-region start-of-body (point-max)))
X      (insert "\n")
X
X      (if sigfile
X      (delete-region end-of-body (point-max)))
X      )))
X
;;
;; Validate MD4 signature. A message is shown with the result.
;; If the signature does not match, buffer "*MD4 Buffer*" holds more
;; information.
;;
(defun md4-validate-signature ()
X  "Checks a MD4-signature in the article being read. May be called
from gnus-article-prepare-hook."
X  (interactive)
X
X  (if (null md4-validation)
X      nil
X    (let (start-of-body)
X      (goto-char (point-min))
X      (search-forward "\n\n")
X      (setq start-of-body (point-marker))    ; remember where
X
X      ;; Check if a signature header is present
X      (goto-char (point-min))
X      (if (search-forward
X       (concat "\n" md4-signature-header ": ")
X       start-of-body t)
X      (let (signature (here (point)))
X        (forward-line 1)
X        (setq signature (buffer-substring here (1- (point))))
X
X        ;; Validate
X        (if (string=
X         signature
X         (md4-signature-region start-of-body (point-max)))
X        (progn
X          (if (not (equal md4-validation t))
X              (message "MD4 signature valid."))
X          (bury-buffer md4-buffer))
X          (beep)
X          (save-excursion
X        (set-buffer md4-buffer)
X        (goto-char (point-min))
X        (insert (message "MD4 signature mismatch!")
X            "\nPosted:     " signature
X            "\nCalculated: ")
X        (goto-char (point-min))))
X        )))))
X
(defun md4-signature-region (start end)
X  "Calculates MD4 signature."
X
X  ;; Get buffer and clear it
X  (setq md4-buffer (get-buffer-create "*MD4 Buffer*"))
X  (save-excursion
X    (set-buffer md4-buffer)
X    (erase-buffer))
X
X  ;; Run md4
X  (call-process-region start end
X               md4-command nil md4-buffer nil)
X
X  ;; Verify normal result
X  (save-excursion
X    (set-buffer md4-buffer)
X    (if (= (buffer-size) 33)
X    (buffer-substring (point-min) (1- (point-max)))
X      (error "Unexpected result from %s: %s" md4-command
X         (buffer-substring (point-min) (point-max))))))
SHAR_EOF
chmod 0444 md4.el ||
echo 'restore of md4.el failed'
Wc_c="`wc -c < 'md4.el'`"
test 5865 -eq "$Wc_c" ||
    echo 'md4.el: original size 5865, current size' "$Wc_c"
rm -f _shar_wnt_.tmp
fi
# ============= add-hook.el ==============
if test -f 'add-hook.el' -a X"$1" != X"-c"; then
    echo 'x - skipping add-hook.el (File already exists)'
    rm -f _shar_wnt_.tmp
else
> _shar_wnt_.tmp
echo 'x - extracting add-hook.el (Text)'
sed 's/^X//' << 'SHAR_EOF' > 'add-hook.el' &&
;; add-hook function by Dan LaLiberte <[e-mail]>
X
(provide 'add-hook)
X
(defun add-hook (hook-var hook-function)
X  "Prepend to the value of HOOK-VAR the function HOOK-FUNCTION, if it
is not already an element.
hook-var's value may be a single function or a list of functions."
X  (if (boundp hook-var)
X      (let ((value (symbol-value hook-var)))
X    (if (and (listp value) (not (eq (car value) 'lambda)))
X        (and (not (memq hook-function value))
X         (set hook-var
X              (cons hook-function value)))
X      (and (not (eq hook-function value))
X           (set hook-var
X            (list hook-function value)))))
X    (set hook-var hook-function)
X    ))
SHAR_EOF
chmod 0644 add-hook.el ||
echo 'restore of add-hook.el failed'
Wc_c="`wc -c < 'add-hook.el'`"
test 647 -eq "$Wc_c" ||
    echo 'add-hook.el: original size 647, current size' "$Wc_c"
rm -f _shar_wnt_.tmp
fi
exit 0
--
Johan Vromans                       [e-mail] via internet backbones
Multihouse Automatisering bv               uucp: ..!{uunet,hp4nl}!mh.nl!jv
Doesburgweg 7, 2803 PL Gouda, The Netherlands  phone/fax: [phone]/62500
------------------------ "Arms are made for hugging" -------------------------