Merge remote-tracking branch 'remotes/origin/flim-1_14'.

[elisp/flim.git] / hmac-def.el

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+;;; hmac-def.el --- A macro for defining HMAC functions.
+
+;; Copyright (C) 1999, 2001  Free Software Foundation, Inc.
+
+;; Author: Shuhei KOBAYASHI <shuhei@aqua.ocn.ne.jp>
+;; Keywords: HMAC, RFC 2104
+
+;; This file is part of FLIM (Faithful Library about Internet Message).
+
+;; This program 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.
+
+;; This program 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 this program; 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)
+
+;;; hmac-def.el ends here