lisp/gnus/rfc2104.el

   1 ;;; rfc2104.el --- RFC2104 Hashed Message Authentication Codes
   2
   3 ;; Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003, 2004,
   4 ;;   2005, 2006, 2007 Free Software Foundation, Inc.
   5
   6 ;; Author: Simon Josefsson <jas@pdc.kth.se>
   7 ;; Keywords: mail
   8
   9 ;; This file is part of GNU Emacs.
  10
  11 ;; GNU Emacs is free software; you can redistribute it and/or modify
  12 ;; it under the terms of the GNU General Public License as published by
  13 ;; the Free Software Foundation; either version 3, or (at your option)
  14 ;; any later version.
  15
  16 ;; GNU Emacs is distributed in the hope that it will be useful,
  17 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  18 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  19 ;; GNU General Public License for more details.
  20
  21 ;; You should have received a copy of the GNU General Public License
  22 ;; along with GNU Emacs; see the file COPYING.  If not, write to the
  23 ;; Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  24 ;; Boston, MA 02110-1301, USA.
  25
  26 ;;; Commentary:
  27
  28 ;;; This is a quick'n'dirty, low performance, implementation of RFC2104.
  29 ;;;
  30 ;;; Example:
  31 ;;;
  32 ;;; (require 'md5)
  33 ;;; (rfc2104-hash 'md5 64 16 "Jefe" "what do ya want for nothing?")
  34 ;;; "750c783e6ab0b503eaa86e310a5db738"
  35 ;;;
  36 ;;; (require 'sha-1)
  37 ;;; (rfc2104-hash 'sha1-encode 64 20 "Jefe" "what do ya want for nothing?")
  38 ;;; "effcdf6ae5eb2fa2d27416d5f184df9c259a7c79"
  39 ;;;
  40 ;;; 64 is block length of hash function (64 for MD5 and SHA), 16 is
  41 ;;; resulting hash length (16 for MD5, 20 for SHA).
  42 ;;;
  43 ;;; Tested with Emacs 20.2 and XEmacs 20.3.
  44 ;;;
  45 ;;; Test case reference: RFC 2202.
  46
  47 ;;; Release history:
  48 ;;;
  49 ;;; 1998-08-16  initial release posted to gnu.emacs.sources
  50 ;;; 1998-08-17  use append instead of char-list-to-string
  51 ;;; 1998-08-26  don't require hexl
  52 ;;; 1998-09-25  renamed from hmac.el to rfc2104.el, also renamed functions
  53 ;;; 1999-10-23  included in pgnus
  54 ;;; 2000-08-15  `rfc2104-hexstring-to-bitstring'
  55 ;;; 2000-05-12  added sha-1 example, added test case reference
  56
  57 ;;; Code:
  58
  59 (eval-when-compile (require 'cl))
  60
  61 ;; Magic character for inner HMAC round. 0x36 == 54 == '6'
  62 (defconst rfc2104-ipad ?\x36)
  63
  64 ;; Magic character for outer HMAC round. 0x5C == 92 == '\'
  65 (defconst rfc2104-opad ?\x5C)
  66
  67 ;; Not so magic character for padding the key. 0x00
  68 (defconst rfc2104-zero ?\x00)
  69
  70 ;; Alist for converting hex to decimal.
  71 (defconst rfc2104-hex-alist
  72   '((?0 . 0)          (?a . 10)       (?A . 10)
  73     (?1 . 1)          (?b . 11)       (?B . 11)
  74     (?2 . 2)          (?c . 12)       (?C . 12)
  75     (?3 . 3)          (?d . 13)       (?D . 13)
  76     (?4 . 4)          (?e . 14)       (?E . 14)
  77     (?5 . 5)          (?f . 15)       (?F . 15)
  78     (?6 . 6)
  79     (?7 . 7)
  80     (?8 . 8)
  81     (?9 . 9)))
  82
  83 (defun rfc2104-hex-to-int (str)
  84   (if str
  85       (if (listp str)
  86           (+ (* 16 (rfc2104-hex-to-int (cdr str)))
  87              (cdr (assoc (car str) rfc2104-hex-alist)))
  88         (rfc2104-hex-to-int (reverse (append str nil))))
  89     0))
  90
  91 (defun rfc2104-hexstring-to-bitstring (str)
  92   (let (out)
  93     (while (< 0 (length str))
  94       (push (rfc2104-hex-to-int (substring str -2)) out)
  95       (setq str (substring str 0 -2)))
  96     (concat out)))
  97
  98 (defun rfc2104-hash (hash block-length hash-length key text)
  99   (let* (;; if key is longer than B, reset it to HASH(key)
 100          (key (if (> (length key) block-length)
 101                   (funcall hash key) key))
 102          (k_ipad (append key nil))
 103          (k_opad (append key nil)))
 104     ;; zero pad k_ipad/k_opad
 105     (while (< (length k_ipad) block-length)
 106       (setq k_ipad (append k_ipad (list rfc2104-zero))))
 107     (while (< (length k_opad) block-length)
 108       (setq k_opad (append k_opad (list rfc2104-zero))))
 109     ;; XOR key with ipad/opad into k_ipad/k_opad
 110     (setq k_ipad (mapcar (lambda (c) (logxor c rfc2104-ipad)) k_ipad))
 111     (setq k_opad (mapcar (lambda (c) (logxor c rfc2104-opad)) k_opad))
 112     ;; perform outer hash
 113     (funcall hash (concat k_opad (rfc2104-hexstring-to-bitstring
 114                                   ;; perform inner hash
 115                                   (funcall hash (concat k_ipad text)))))))
 116
 117 (provide 'rfc2104)
 118
 119 ;;; arch-tag: cf671d5c-a45f-4a09-815e-704e59e43950
 120 ;;; rfc2104.el ends here