;;; rfc2104.el --- RFC2104 Hashed Message Authentication Codes
;; Copyright (C) 1998, 1999, 2000 Free Software Foundation, Inc.
;; Author: Simon Josefsson <email@example.com>
;; Keywords: mail
;; This file is part of GNU Emacs.
;; GNU Emacs is free software; you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation; either version 2, or (at your option)
;; any later version.
;; GNU Emacs is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
;; GNU General Public License for more details.
;; You should have received a copy of the GNU General Public License
;; along with GNU Emacs; see the file COPYING. If not, write to the
;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
;; Boston, MA 02111-1307, USA.
;;; This is a quick'n'dirty, low performance, implementation of RFC2104.
;;; (require 'md5)
;;; (rfc2104-hash 'md5 64 16 "Jefe" "what do ya want for nothing?")
;;; (require 'sha-1)
;;; (rfc2104-hash 'sha1-encode 64 20 "Jefe" "what do ya want for nothing?")
;;; 64 is block length of hash function (64 for MD5 and SHA), 16 is
;;; resulting hash length (16 for MD5, 20 for SHA).
;;; Tested with Emacs 20.2 and XEmacs 20.3.
;;; Test case reference: RFC 2202.
;;; Release history:
;;; 1998-08-16 initial release posted to gnu.emacs.sources
;;; 1998-08-17 use append instead of char-list-to-string
;;; 1998-08-26 don't require hexl
;;; 1998-09-25 renamed from hmac.el to rfc2104.el, also renamed functions
;;; 1999-10-23 included in pgnus
;;; 2000-08-15 `rfc2104-hexstring-to-bitstring'
;;; 2000-05-12 added sha-1 example, added test case reference
(eval-when-compile (require 'cl))
;; Magic character for inner HMAC round. 0x36 == 54 == '6'
(defconst rfc2104-ipad ?\x36)
;; Magic character for outer HMAC round. 0x5C == 92 == '\'
(defconst rfc2104-opad ?\x5C)
;; Not so magic character for padding the key. 0x00
(defconst rfc2104-zero ?\x00)
;; Alist for converting hex to decimal.
'((?0 . 0) (?a . 10) (?A . 10)
(?1 . 1) (?b . 11) (?B . 11)
(?2 . 2) (?c . 12) (?C . 12)
(?3 . 3) (?d . 13) (?D . 13)
(?4 . 4) (?e . 14) (?E . 14)
(?5 . 5) (?f . 15) (?F . 15)
(?6 . 6)
(?7 . 7)
(?8 . 8)
(?9 . 9)))
(defun rfc2104-hex-to-int (str)
(if (listp str)
(+ (* 16 (rfc2104-hex-to-int (cdr str)))
(cdr (assoc (car str) rfc2104-hex-alist)))
(rfc2104-hex-to-int (reverse (append str nil))))
(defun rfc2104-hexstring-to-bitstring (str)
(while (< 0 (length str))
(push (rfc2104-hex-to-int (substring str -2)) out)
(setq str (substring str 0 -2)))
(defun rfc2104-hash (hash block-length hash-length key text)
(let* (;; if key is longer than B, reset it to HASH(key)
(key (if (> (length key) block-length)
(funcall hash key) key))
(k_ipad (append key nil))
(k_opad (append key nil)))
;; zero pad k_ipad/k_opad
(while (< (length k_ipad) block-length)
(setq k_ipad (append k_ipad (list rfc2104-zero))))
(while (< (length k_opad) block-length)
(setq k_opad (append k_opad (list rfc2104-zero))))
;; XOR key with ipad/opad into k_ipad/k_opad
(setq k_ipad (mapcar (lambda (c) (logxor c rfc2104-ipad)) k_ipad))
(setq k_opad (mapcar (lambda (c) (logxor c rfc2104-opad)) k_opad))
;; perform outer hash
(funcall hash (concat k_opad (rfc2104-hexstring-to-bitstring
;; perform inner hash
(funcall hash (concat k_ipad text)))))))
;;; rfc2104.el ends here