112 lines
3.7 KiB
EmacsLisp
112 lines
3.7 KiB
EmacsLisp
;;; rfc2104.el --- RFC2104 Hashed Message Authentication Codes -*- lexical-binding:t -*-
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;; Copyright (C) 1998-2024 Free Software Foundation, Inc.
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;; Author: Simon Josefsson <jas@pdc.kth.se>
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;; Keywords: mail
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;; This file is part of GNU Emacs.
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;; GNU Emacs is free software: you can redistribute it and/or modify
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;; it under the terms of the GNU General Public License as published by
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;; the Free Software Foundation, either version 3 of the License, or
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;; (at your option) any later version.
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;; GNU Emacs is distributed in the hope that it will be useful,
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;; but WITHOUT ANY WARRANTY; without even the implied warranty of
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;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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;; GNU General Public License for more details.
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;; You should have received a copy of the GNU General Public License
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;; along with GNU Emacs. If not, see <https://www.gnu.org/licenses/>.
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;;; Commentary:
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;; This is a high performance implementation of RFC2104.
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;;
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;; Example:
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;;
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;; (rfc2104-hash 'md5 64 16 "Jefe" "what do ya want for nothing?")
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;; "750c783e6ab0b503eaa86e310a5db738"
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;;
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;; (rfc2104-hash 'sha1 64 20 "Jefe" "what do ya want for nothing?")
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;; "effcdf6ae5eb2fa2d27416d5f184df9c259a7c79"
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;;
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;; 64 is block length of hash function (64 for MD5 and SHA), 16 is
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;; resulting hash length (16 for MD5, 20 for SHA).
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;;
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;; Test case reference: RFC 2202.
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;;; History:
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;; 1998-08-16 initial release posted to gnu.emacs.sources
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;; 1998-08-17 use append instead of char-list-to-string
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;; 1998-08-26 don't require hexl
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;; 1998-09-25 renamed from hmac.el to rfc2104.el, also renamed functions
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;; 1999-10-23 included in pgnus
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;; 2000-08-15 `rfc2104-hexstring-to-bitstring'
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;; 2000-05-12 added sha-1 example, added test case reference
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;; 2003-11-13 change rfc2104-hexstring-to-bitstring to ...-byte-list
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;; 2008-04-25 rewrite rfc2104-hash for speed
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;;; Code:
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(eval-when-compile (require 'cl-lib))
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;; Magic character for inner HMAC round. 0x36 == 54 == '6'
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(defconst rfc2104-ipad ?\x36)
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;; Magic character for outer HMAC round. 0x5C == 92 == '\'
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(defconst rfc2104-opad ?\x5C)
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(defconst rfc2104-nybbles
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(let ((v (make-vector
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;; Find upper bound to save some space.
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(1+ (max ?0 ?9 ?a ?f ?A ?F))
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;; Use non-numeric default to catch bogus hex strings.
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nil))
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(ls '((?0 . 0) (?a . 10) (?A . 10)
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(?1 . 1) (?b . 11) (?B . 11)
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(?2 . 2) (?c . 12) (?C . 12)
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(?3 . 3) (?d . 13) (?D . 13)
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(?4 . 4) (?e . 14) (?E . 14)
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(?5 . 5) (?f . 15) (?F . 15)
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(?6 . 6)
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(?7 . 7)
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(?8 . 8)
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(?9 . 9))))
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(while ls
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(aset v (caar ls) (cdar ls))
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(setq ls (cdr ls)))
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v))
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(defun rfc2104-hash (hash block-length hash-length key text)
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(let* (;; if key is longer than B, reset it to HASH(key)
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(key (if (> (length key) block-length)
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(funcall hash key) key))
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(len (length key))
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(ipad (make-string block-length rfc2104-ipad))
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(opad (make-string (+ block-length hash-length) rfc2104-opad))
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c partial)
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;; Prefix *pad with key, appropriately XORed.
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(cl-do ((i 0 (1+ i)))
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((= len i))
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(setq c (aref key i))
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(aset ipad i (logxor rfc2104-ipad c))
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(aset opad i (logxor rfc2104-opad c)))
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;; Perform inner hash.
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(setq partial (funcall hash (concat ipad text)))
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;; Pack latter part of opad.
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(cl-do ((r 0 (+ 2 r))
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(w block-length (1+ w)))
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((= (* 2 hash-length) r))
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(aset opad w
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(+ (* 16 (aref rfc2104-nybbles (aref partial r)))
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( aref rfc2104-nybbles (aref partial (1+ r))))))
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;; Perform outer hash.
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(funcall hash opad)))
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(provide 'rfc2104)
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;;; rfc2104.el ends here
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