import hmac code from sean mcafee to remove gnutls dependency

1 files changed, 33 insertions, 2 deletions

diff --git a/kasi-totp.el b/kasi-totp.el
index d14e00a..b8fe078 100644
--- a/kasi-totp.el
+++ b/kasi-totp.el
@@ -1,10 +1,41 @@
 ;; TOTP code taken from Mastering Emacs which took from Jürgen Hötzel's `totp.el'.
 ;; Base32 code taken from same Mastering Emacs article.
+;; HMAC code taken from Sean McAfee.
 ;; https://www.masteringemacs.org/article/securely-generating-totp-tokens-emacs
 ;; https://github.com/juergenhoetzel/emacs-totp
+;; https://github.com/grimnebulin/emacs-hmac
 (require 'bindat)
-(require 'gnutls)
 (require 'hexl)
+(require 'cl-lib)
+(require 'subr-x)
+
+(defconst hmac-algorithm-blocksizes
+  '((md5 . 64)
+    (sha1 . 64)
+    (sha224 . 64)
+    (sha256 . 64)
+    (sha384 . 128)
+    (sha512 . 128))
+  "Mapping from HMAC algorithm to the algorithm's blocksize.")
+
+(defun hmac (algorithm key message &optional binary)
+  "Compute the HMAC for a given message, private key and algorithm.
+
+ALGORITHM is a symbol naming one of the algorithms recognized by
+`secure-hash'.  KEY is a the private key to use.  MESSAGE, a
+string, is the message to hash.  If BINARY is non-nil, the hmac
+will be returned as a binary string, otherwise as a hexadecimal
+string."
+  (if-let (blocksize (alist-get algorithm hmac-algorithm-blocksizes))
+      (progn
+        (when (> (length key) blocksize)
+          (setq key (secure-hash algorithm key)))
+        (when (< (length key) blocksize)
+          (setq key (concat key (make-string (- blocksize (length key)) 0))))
+        (let ((o-key-pad (cl-map 'string #'logxor key (make-string blocksize #x5c)))
+              (i-key-pad (cl-map 'string #'logxor key (make-string blocksize #x36))))
+          (secure-hash algorithm (concat o-key-pad (secure-hash algorithm (concat i-key-pad message) nil nil t)) nil nil binary)))
+    (error "Unsupported hash algorithm %s" algorithm)))
 
 (defconst base32-alphabet
   (let ((tbl (make-char-table nil)))
@@ -50,7 +81,7 @@ required for HMAC-TOTP."
          ;; we have to manually split the 64 bit number (u64 not supported in Emacs 27.2)
          (counter-bytes (bindat-pack  '((:high u32) (:low u32))
                                       `((:high . ,(ash counter -32)) (:low . ,(logand counter #xffffffff)))))
-         (mac (gnutls-hash-mac 'SHA1 key-bytes counter-bytes))
+         (mac (hmac 'sha1 key-bytes counter-bytes))
          (offset (logand (bindat-get-field (bindat-unpack '((:offset u8)) mac 19) :offset) #xf)))
     (format "%06d"
             (mod