-;;; hmac-def.el --- Functions/macros for defining HMAC functions.
+;;; hmac-def.el --- A macro for defining HMAC functions.
;; Copyright (C) 1999 Shuhei KOBAYASHI
;;; Commentary:
-;; See RFC 2104, "HMAC: Keyed-Hashing for Message Authentication"
-;; for definition of HMAC.
+;; This program is implemented from RFC 2104,
+;; "HMAC: Keyed-Hashing for Message Authentication".
;;; Code:
-(require 'hmac-util)
-
-(defmacro hmac-unhex-string-macro (string length)
- (let* ((len (eval length))
- (dst (make-string (/ len 2) 0)))
- `(let ((str ,string)
- (dst ,dst)
- (idx 0)(pos 0))
- (while (< pos ,len)
- (aset dst idx (+ (* (hmac-hex-to-int (aref str pos)) 16)
- (hmac-hex-to-int (aref str (1+ pos)))))
- (setq idx (1+ idx)
- pos (+ 2 pos)))
- dst)))
-
-;; Note that H, B, and L will be evaluated multiple times. They are
-;; usually constants, so I don't want to bother to bind them locally.
(defmacro define-hmac-function (name H B L &optional bit)
- "Define a function NAME which computes HMAC with hash function H.
+ "Define a function NAME(TEXT KEY) which computes HMAC with function H.
-HMAC function is H\(KEY XOR opad, H\(KEY XOR ipad, TEXT\)\):
+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 \(in hexadecimal form\).
-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. \(L=16 for MD5, L=20 for SHA1.\)
+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))
- (when (> len ,B)
- (setq key (hmac-unhex-string-macro (,H key) ,(* L 2)))
- (setq 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)))
- ;; If outer `hmac-unhex-string-macro' is removed, return value
- ;; will be in hexadecimal form. It is useful for test.
- ,(if (and bit (< (/ bit 8) L))
- `(substring
- (hmac-unhex-string-macro
- (,H
- (concat key-xor-opad
- (hmac-unhex-string-macro
- (,H (concat key-xor-ipad text))
- ,(* L 2))))
- ,(* L 2))
- 0 ,(/ bit 8))
- `(hmac-unhex-string-macro
- (,H
- (concat key-xor-opad
- (hmac-unhex-string-macro
- (,H (concat key-xor-ipad text))
- ,(* L 2))))
- ,(* L 2))))))
+ (` (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.
+;;; hmac-def.el ends here