lisp/gnus/rfc2104.el

   1 ;;; rfc2104.el --- RFC2104 Hashed Message Authentication Codes
   2 ;; Copyright (C) 1998, 1999, 2000 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 ;;; (require 'sha-1)
  35 ;;; (rfc2104-hash 'sha1-encode 64 20 "Jefe" "what do ya want for nothing?")
  36 ;;; "effcdf6ae5eb2fa2d27416d5f184df9c259a7c79"
  37 ;;;
  38 ;;; 64 is block length of hash function (64 for MD5 and SHA), 16 is
  39 ;;; resulting hash length (16 for MD5, 20 for SHA).
  40 ;;;
  41 ;;; Tested with Emacs 20.2 and XEmacs 20.3.
  42 ;;;
  43 ;;; Test case reference: RFC 2202.
  44
  45 ;;; Release history:
  46 ;;;
  47 ;;; 1998-08-16  initial release posted to gnu.emacs.sources
  48 ;;; 1998-08-17  use append instead of char-list-to-string
  49 ;;; 1998-08-26  don't require hexl
  50 ;;; 1998-09-25  renamed from hmac.el to rfc2104.el, also renamed functions
  51 ;;; 1999-10-23  included in pgnus
  52 ;;; 2000-08-15  `rfc2104-hexstring-to-bitstring'
  53 ;;; 2000-05-12  added sha-1 example, added test case reference
  54
  55 (eval-when-compile (require 'cl))
  56
  57 ;; Magic character for inner HMAC round. 0x36 == 54 == '6'
  58 (defconst rfc2104-ipad ?\x36)
  59
  60 ;; Magic character for outer HMAC round. 0x5C == 92 == '\'
  61 (defconst rfc2104-opad ?\x5C)
  62
  63 ;; Not so magic character for padding the key. 0x00
  64 (defconst rfc2104-zero ?\x00)
  65
  66 ;; Alist for converting hex to decimal.
  67 (defconst rfc2104-hex-alist
  68   '((?0 . 0)          (?a . 10)       (?A . 10)
  69     (?1 . 1)          (?b . 11)       (?B . 11)
  70     (?2 . 2)          (?c . 12)       (?C . 12)
  71     (?3 . 3)          (?d . 13)       (?D . 13)
  72     (?4 . 4)          (?e . 14)       (?E . 14)
  73     (?5 . 5)          (?f . 15)       (?F . 15)
  74     (?6 . 6)
  75     (?7 . 7)
  76     (?8 . 8)
  77     (?9 . 9)))
  78
  79 (defun rfc2104-hex-to-int (str)
  80   (if str
  81       (if (listp str)
  82           (+ (* 16 (rfc2104-hex-to-int (cdr str)))
  83              (cdr (assoc (car str) rfc2104-hex-alist)))
  84         (rfc2104-hex-to-int (reverse (append str nil))))
  85     0))
  86
  87 (defun rfc2104-hexstring-to-bitstring (str)
  88   (let (out)
  89     (while (< 0 (length str))
  90       (push (rfc2104-hex-to-int (substring str -2)) out)
  91       (setq str (substring str 0 -2)))
  92     (concat out)))
  93
  94 (defun rfc2104-hash (hash block-length hash-length key text)
  95   (let* (;; if key is longer than B, reset it to HASH(key)
  96          (key (if (> (length key) block-length)
  97                   (funcall hash key) key))
  98          (k_ipad (append key nil))
  99          (k_opad (append key nil)))
 100     ;; zero pad k_ipad/k_opad
 101     (while (< (length k_ipad) block-length)
 102       (setq k_ipad (append k_ipad (list rfc2104-zero))))
 103     (while (< (length k_opad) block-length)
 104       (setq k_opad (append k_opad (list rfc2104-zero))))
 105     ;; XOR key with ipad/opad into k_ipad/k_opad
 106     (setq k_ipad (mapcar (lambda (c) (logxor c rfc2104-ipad)) k_ipad))
 107     (setq k_opad (mapcar (lambda (c) (logxor c rfc2104-opad)) k_opad))
 108     ;; perform outer hash
 109     (funcall hash (concat k_opad (rfc2104-hexstring-to-bitstring
 110                                   ;; perform inner hash
 111                                   (funcall hash (concat k_ipad text)))))))
 112
 113 (provide 'rfc2104)
 114
 115 ;;; rfc2104.el ends here