lisp/gnus/rfc2104.el

   1 ;;; rfc2104.el --- RFC2104 Hashed Message Authentication Codes
   2 ;; Copyright (C) 1998,1999 Free Software Foundation, Inc.
   3
   4 ;; Author: Simon Josefsson <jas@pdc.kth.se>
   5 ;; Keywords: mail
   6
   7 ;; This file is part of GNU Emacs.
   8
   9 ;; GNU Emacs is free software; you can redistribute it and/or modify
  10 ;; it under the terms of the GNU General Public License as published by
  11 ;; the Free Software Foundation; either version 2, or (at your option)
  12 ;; any later version.
  13
  14 ;; GNU Emacs is distributed in the hope that it will be useful,
  15 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  16 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17 ;; GNU General Public License for more details.
  18
  19 ;; You should have received a copy of the GNU General Public License
  20 ;; along with GNU Emacs; see the file COPYING.  If not, write to the
  21 ;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  22 ;; Boston, MA 02111-1307, USA.
  23
  24 ;;; Commentary:
  25
  26 ;;; This is a quick'n'dirty, low performance, implementation of RFC2104.
  27 ;;;
  28 ;;; Example:
  29 ;;;
  30 ;;; (require 'md5)
  31 ;;; (rfc2104-hash 'md5 64 16 "Jefe" "what do ya want for nothing?")
  32 ;;; "750c783e6ab0b503eaa86e310a5db738"
  33 ;;;
  34 ;;; 64 is block length of hash function (64 for MD5 and SHA), 16 is
  35 ;;; resulting hash length (16 for MD5, 20 for SHA).
  36 ;;;
  37 ;;; Tested with Emacs 20.2 and XEmacs 20.3.
  38
  39 ;;; Release history:
  40 ;;;
  41 ;;; 1998-08-16  initial release posted to gnu.emacs.sources
  42 ;;; 1998-08-17  use append instead of char-list-to-string
  43 ;;; 1998-08-26  don't require hexl
  44 ;;; 1998-09-25  renamed from hmac.el to rfc2104.el, also renamed functions
  45 ;;; 1999-10-23  included in pgnus
  46
  47 (eval-when-compile (require 'cl))
  48
  49 ;; Magic character for inner HMAC round. 0x36 == 54 == '6'
  50 (defconst rfc2104-ipad ?\x36)
  51
  52 ;; Magic character for outer HMAC round. 0x5C == 92 == '\'
  53 (defconst rfc2104-opad ?\x5C)
  54
  55 ;; Not so magic character for padding the key. 0x00
  56 (defconst rfc2104-zero ?\x00)
  57
  58 ;; Alist for converting hex to decimal.
  59 (defconst rfc2104-hex-alist
  60   '((?0 . 0)          (?a . 10)       (?A . 10)
  61     (?1 . 1)          (?b . 11)       (?B . 11)
  62     (?2 . 2)          (?c . 12)       (?C . 12)
  63     (?3 . 3)          (?d . 13)       (?D . 13)
  64     (?4 . 4)          (?e . 14)       (?E . 14)
  65     (?5 . 5)          (?f . 15)       (?F . 15)
  66     (?6 . 6)
  67     (?7 . 7)
  68     (?8 . 8)
  69     (?9 . 9)))
  70
  71 (defun rfc2104-hex-to-int (str)
  72   (if str
  73       (if (listp str)
  74           (+ (* 16 (rfc2104-hex-to-int (cdr str)))
  75              (cdr (assoc (car str) rfc2104-hex-alist)))
  76         (rfc2104-hex-to-int (reverse (append str nil))))
  77     0))
  78
  79 (defun rfc2104-hash (hash block-length hash-length key text)
  80   (let* (;; if key is longer than B, reset it to HASH(key)
  81          (key (if (> (length key) block-length)
  82                   (funcall hash key) key))
  83          (k_ipad (append key nil))
  84          (k_opad (append key nil)))
  85     ;; zero pad k_ipad/k_opad
  86     (while (< (length k_ipad) block-length)
  87       (setq k_ipad (append k_ipad (list rfc2104-zero))))
  88     (while (< (length k_opad) block-length)
  89       (setq k_opad (append k_opad (list rfc2104-zero))))
  90     ;; XOR key with ipad/opad into k_ipad/k_opad
  91     (setq k_ipad (mapcar (lambda (c) (logxor c rfc2104-ipad)) k_ipad))
  92     (setq k_opad (mapcar (lambda (c) (logxor c rfc2104-opad)) k_opad))
  93     ;; perform inner hash
  94     (let ((first-round (funcall hash (concat k_ipad text)))
  95           de-hexed)
  96       (while (< 0 (length first-round))
  97         (push (rfc2104-hex-to-int (substring first-round -2)) de-hexed)
  98         (setq first-round (substring first-round 0 -2)))
  99       ;; perform outer hash
 100       (funcall hash (concat k_opad de-hexed)))))
 101
 102 (provide 'rfc2104)
 103
 104 ;;; rfc2104.el ends here