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Diffstat (limited to 'lisp/net/hmac-def.el')
| -rw-r--r-- | lisp/net/hmac-def.el | 86 |
1 files changed, 86 insertions, 0 deletions
diff --git a/lisp/net/hmac-def.el b/lisp/net/hmac-def.el new file mode 100644 index 00000000000..bfff7282adf --- /dev/null +++ b/lisp/net/hmac-def.el @@ -0,0 +1,86 @@ +;;; hmac-def.el --- A macro for defining HMAC functions. + +;; Copyright (C) 1999, 2001, 2007 Free Software Foundation, Inc. + +;; Author: Shuhei KOBAYASHI <shuhei@aqua.ocn.ne.jp> +;; Keywords: HMAC, RFC 2104 + +;; 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, 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., 51 Franklin Street, Fifth Floor, +;; Boston, MA 02110-1301, USA. + +;;; Commentary: + +;; This program is implemented from RFC 2104, +;; "HMAC: Keyed-Hashing for Message Authentication". + +;;; Code: + +(defmacro define-hmac-function (name H B L &optional bit) + "Define a function NAME(TEXT KEY) which computes HMAC with function H. + +HMAC function is H(KEY XOR opad, H(KEY XOR ipad, TEXT)): + +H is a cryptographic hash function, such as SHA1 and MD5, which takes +a string and return a digest of it (in binary form). +B is a byte-length of a block size of H. (B=64 for both SHA1 and MD5.) +L is a byte-length of hash outputs. (L=16 for MD5, L=20 for SHA1.) +If BIT is non-nil, truncate output to specified bits." + `(defun ,name (text key) + ,(concat "Compute " + (upcase (symbol-name name)) + " over TEXT with KEY.") + (let ((key-xor-ipad (make-string ,B ?\x36)) + (key-xor-opad (make-string ,B ?\x5C)) + (len (length key)) + (pos 0)) + (unwind-protect + (progn + ;; if `key' is longer than the block size, apply hash function + ;; to `key' and use the result as a real `key'. + (if (> len ,B) + (setq key (,H key) + len ,L)) + (while (< pos len) + (aset key-xor-ipad pos (logxor (aref key pos) ?\x36)) + (aset key-xor-opad pos (logxor (aref key pos) ?\x5C)) + (setq pos (1+ pos))) + (setq key-xor-ipad (unwind-protect + (concat key-xor-ipad text) + (fillarray key-xor-ipad 0)) + key-xor-ipad (unwind-protect + (,H key-xor-ipad) + (fillarray key-xor-ipad 0)) + key-xor-opad (unwind-protect + (concat key-xor-opad key-xor-ipad) + (fillarray key-xor-opad 0)) + key-xor-opad (unwind-protect + (,H key-xor-opad) + (fillarray key-xor-opad 0))) + ;; now `key-xor-opad' contains + ;; H(KEY XOR opad, H(KEY XOR ipad, TEXT)). + ,(if (and bit (< (/ bit 8) L)) + `(substring key-xor-opad 0 ,(/ bit 8)) + ;; return a copy of `key-xor-opad'. + `(concat key-xor-opad))) + ;; cleanup. + (fillarray key-xor-ipad 0) + (fillarray key-xor-opad 0))))) + +(provide 'hmac-def) + +;;; arch-tag: 645adcef-b835-4900-a10a-11f636c982b9 +;;; hmac-def.el ends here |