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|
;;; rfc2104.el --- RFC2104 Hashed Message Authentication Codes
;; Copyright (C) 1998-2011 Free Software Foundation, Inc.
;; Author: Simon Josefsson <jas@pdc.kth.se>
;; 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 3 of the License, 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. If not, see <http://www.gnu.org/licenses/>.
;;; Commentary:
;; This is a high performance implementation of RFC2104.
;;
;; Example:
;;
;; (require 'md5)
;; (rfc2104-hash 'md5 64 16 "Jefe" "what do ya want for nothing?")
;; "750c783e6ab0b503eaa86e310a5db738"
;;
;; (require 'sha1)
;; (rfc2104-hash 'sha1 64 20 "Jefe" "what do ya want for nothing?")
;; "effcdf6ae5eb2fa2d27416d5f184df9c259a7c79"
;;
;; 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.
;;; 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
;; 2003-11-13 change rfc2104-hexstring-to-bitstring to ...-byte-list
;; 2008-04-25 rewrite rfc2104-hash for speed
;;; Code:
(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)
(defconst rfc2104-nybbles
(let ((v (make-vector
;; Find upper bound to save some space.
(1+ (max ?0 ?9 ?a ?f ?A ?F))
;; Use non-numeric default to catch bogus hex strings.
nil))
(ls '((?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))))
(while ls
(aset v (caar ls) (cdar ls))
(setq ls (cdr ls)))
v))
(eval-when-compile
(defmacro rfc2104-string-make-unibyte (string)
"Return the unibyte equivalent of STRING.
In XEmacs return just STRING."
(if (featurep 'xemacs)
string
`(string-make-unibyte ,string))))
(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))
(len (length key))
(ipad (make-string block-length rfc2104-ipad))
(opad (make-string (+ block-length hash-length) rfc2104-opad))
c partial)
;; Prefix *pad with key, appropriately XORed.
(do ((i 0 (1+ i)))
((= len i))
(setq c (aref key i))
(aset ipad i (logxor rfc2104-ipad c))
(aset opad i (logxor rfc2104-opad c)))
;; Perform inner hash.
(setq partial (rfc2104-string-make-unibyte
(funcall hash (concat ipad text))))
;; Pack latter part of opad.
(do ((r 0 (+ 2 r))
(w block-length (1+ w)))
((= (* 2 hash-length) r))
(aset opad w
(+ (* 16 (aref rfc2104-nybbles (aref partial r)))
( aref rfc2104-nybbles (aref partial (1+ r))))))
;; Perform outer hash.
(rfc2104-string-make-unibyte (funcall hash opad))))
(provide 'rfc2104)
;;; rfc2104.el ends here
|
