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1 | ;;; hmac-def.el --- A macro for defining HMAC functions. |
2 | ||
ba318903 | 3 | ;; Copyright (C) 1999, 2001, 2007-2014 Free Software Foundation, Inc. |
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4 | |
5 | ;; Author: Shuhei KOBAYASHI <shuhei@aqua.ocn.ne.jp> | |
88f4758e | 6 | ;; Keywords: HMAC, RFC2104 |
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7 | |
8 | ;; This file is part of GNU Emacs. | |
9 | ||
874a927a | 10 | ;; GNU Emacs is free software: you can redistribute it and/or modify |
0cd1fac2 | 11 | ;; it under the terms of the GNU General Public License as published by |
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12 | ;; the Free Software Foundation, either version 3 of the License, or |
13 | ;; (at your option) any later version. | |
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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 | |
874a927a | 21 | ;; along with GNU Emacs. If not, see <http://www.gnu.org/licenses/>. |
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22 | |
23 | ;;; Commentary: | |
24 | ||
88f4758e | 25 | ;; This program is implemented from RFC2104, |
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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 | ||
0cd1fac2 | 83 | ;;; hmac-def.el ends here |