| 1 | ;;; hmac-def.el --- A macro for defining HMAC functions. |
| 2 | |
| 3 | ;; Copyright (C) 1999, 2001, 2007, 2008 Free Software Foundation, Inc. |
| 4 | |
| 5 | ;; Author: Shuhei KOBAYASHI <shuhei@aqua.ocn.ne.jp> |
| 6 | ;; Keywords: HMAC, RFC 2104 |
| 7 | |
| 8 | ;; This file is part of GNU Emacs. |
| 9 | |
| 10 | ;; GNU Emacs is free software: you can redistribute it and/or modify |
| 11 | ;; it under the terms of the GNU General Public License as published by |
| 12 | ;; the Free Software Foundation, either version 3 of the License, or |
| 13 | ;; (at your option) any later version. |
| 14 | |
| 15 | ;; GNU Emacs is distributed in the hope that it will be useful, |
| 16 | ;; but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 17 | ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 18 | ;; GNU General Public License for more details. |
| 19 | |
| 20 | ;; You should have received a copy of the GNU General Public License |
| 21 | ;; along with GNU Emacs. If not, see <http://www.gnu.org/licenses/>. |
| 22 | |
| 23 | ;;; Commentary: |
| 24 | |
| 25 | ;; This program is implemented from RFC 2104, |
| 26 | ;; "HMAC: Keyed-Hashing for Message Authentication". |
| 27 | |
| 28 | ;;; Code: |
| 29 | |
| 30 | (defmacro define-hmac-function (name H B L &optional bit) |
| 31 | "Define a function NAME(TEXT KEY) which computes HMAC with function H. |
| 32 | |
| 33 | HMAC function is H(KEY XOR opad, H(KEY XOR ipad, TEXT)): |
| 34 | |
| 35 | H is a cryptographic hash function, such as SHA1 and MD5, which takes |
| 36 | a string and return a digest of it (in binary form). |
| 37 | B is a byte-length of a block size of H. (B=64 for both SHA1 and MD5.) |
| 38 | L is a byte-length of hash outputs. (L=16 for MD5, L=20 for SHA1.) |
| 39 | If BIT is non-nil, truncate output to specified bits." |
| 40 | `(defun ,name (text key) |
| 41 | ,(concat "Compute " |
| 42 | (upcase (symbol-name name)) |
| 43 | " over TEXT with KEY.") |
| 44 | (let ((key-xor-ipad (make-string ,B ?\x36)) |
| 45 | (key-xor-opad (make-string ,B ?\x5C)) |
| 46 | (len (length key)) |
| 47 | (pos 0)) |
| 48 | (unwind-protect |
| 49 | (progn |
| 50 | ;; if `key' is longer than the block size, apply hash function |
| 51 | ;; to `key' and use the result as a real `key'. |
| 52 | (if (> len ,B) |
| 53 | (setq key (,H key) |
| 54 | len ,L)) |
| 55 | (while (< pos len) |
| 56 | (aset key-xor-ipad pos (logxor (aref key pos) ?\x36)) |
| 57 | (aset key-xor-opad pos (logxor (aref key pos) ?\x5C)) |
| 58 | (setq pos (1+ pos))) |
| 59 | (setq key-xor-ipad (unwind-protect |
| 60 | (concat key-xor-ipad text) |
| 61 | (fillarray key-xor-ipad 0)) |
| 62 | key-xor-ipad (unwind-protect |
| 63 | (,H key-xor-ipad) |
| 64 | (fillarray key-xor-ipad 0)) |
| 65 | key-xor-opad (unwind-protect |
| 66 | (concat key-xor-opad key-xor-ipad) |
| 67 | (fillarray key-xor-opad 0)) |
| 68 | key-xor-opad (unwind-protect |
| 69 | (,H key-xor-opad) |
| 70 | (fillarray key-xor-opad 0))) |
| 71 | ;; now `key-xor-opad' contains |
| 72 | ;; H(KEY XOR opad, H(KEY XOR ipad, TEXT)). |
| 73 | ,(if (and bit (< (/ bit 8) L)) |
| 74 | `(substring key-xor-opad 0 ,(/ bit 8)) |
| 75 | ;; return a copy of `key-xor-opad'. |
| 76 | `(concat key-xor-opad))) |
| 77 | ;; cleanup. |
| 78 | (fillarray key-xor-ipad 0) |
| 79 | (fillarray key-xor-opad 0))))) |
| 80 | |
| 81 | (provide 'hmac-def) |
| 82 | |
| 83 | ;; arch-tag: 645adcef-b835-4900-a10a-11f636c982b9 |
| 84 | ;;; hmac-def.el ends here |