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bc511a64f6
Most of this change is to boilerplate commentary such as license URLs. This change was prompted by ftp://ftp.gnu.org's going-away party, planned for November. Change these FTP URLs to https://ftp.gnu.org instead. Make similar changes for URLs to other organizations moving away from FTP. Also, change HTTP to HTTPS for URLs to gnu.org and fsf.org when this works, as this will further help defend against man-in-the-middle attacks (for this part I omitted the MS-DOS and MS-Windows sources and the test tarballs to keep the workload down). HTTPS is not fully working to lists.gnu.org so I left those URLs alone for now.
83 lines
2.9 KiB
EmacsLisp
83 lines
2.9 KiB
EmacsLisp
;;; hmac-def.el --- A macro for defining HMAC functions.
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;; Copyright (C) 1999, 2001, 2007-2017 Free Software Foundation, Inc.
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;; Author: Shuhei KOBAYASHI <shuhei@aqua.ocn.ne.jp>
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;; Keywords: HMAC, RFC2104
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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 program is implemented from RFC2104,
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;; "HMAC: Keyed-Hashing for Message Authentication".
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;;; Code:
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(defmacro define-hmac-function (name H B L &optional bit)
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"Define a function NAME(TEXT KEY) which computes HMAC with function H.
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HMAC function is H(KEY XOR opad, H(KEY XOR ipad, TEXT)):
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H is a cryptographic hash function, such as SHA1 and MD5, which takes
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a string and return a digest of it (in binary form).
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B is a byte-length of a block size of H. (B=64 for both SHA1 and MD5.)
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L is a byte-length of hash outputs. (L=16 for MD5, L=20 for SHA1.)
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If BIT is non-nil, truncate output to specified bits."
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`(defun ,name (text key)
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,(concat "Compute "
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(upcase (symbol-name name))
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" over TEXT with KEY.")
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(let ((key-xor-ipad (make-string ,B ?\x36))
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(key-xor-opad (make-string ,B ?\x5C))
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(len (length key))
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(pos 0))
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(unwind-protect
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(progn
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;; if `key' is longer than the block size, apply hash function
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;; to `key' and use the result as a real `key'.
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(if (> len ,B)
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(setq key (,H key)
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len ,L))
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(while (< pos len)
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(aset key-xor-ipad pos (logxor (aref key pos) ?\x36))
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(aset key-xor-opad pos (logxor (aref key pos) ?\x5C))
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(setq pos (1+ pos)))
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(setq key-xor-ipad (unwind-protect
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(concat key-xor-ipad text)
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(fillarray key-xor-ipad 0))
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key-xor-ipad (unwind-protect
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(,H key-xor-ipad)
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(fillarray key-xor-ipad 0))
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key-xor-opad (unwind-protect
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(concat key-xor-opad key-xor-ipad)
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(fillarray key-xor-opad 0))
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key-xor-opad (unwind-protect
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(,H key-xor-opad)
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(fillarray key-xor-opad 0)))
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;; now `key-xor-opad' contains
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;; H(KEY XOR opad, H(KEY XOR ipad, TEXT)).
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,(if (and bit (< (/ bit 8) L))
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`(substring key-xor-opad 0 ,(/ bit 8))
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;; return a copy of `key-xor-opad'.
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`(concat key-xor-opad)))
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;; cleanup.
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(fillarray key-xor-ipad 0)
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(fillarray key-xor-opad 0)))))
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(provide 'hmac-def)
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;;; hmac-def.el ends here
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