missing hexstrint->plaintext conversion

[Kiss Gabor (Bitman)]

Dear Werner et al.,

At 2006-07-29 (svn revision 4209) gpg-preset-passphrases was changed
in order to send passphrases as hexstring.
Unfortunately the receiver side did not follow this change well.
Received hexstring is cached without converting back to plaintext.

This patch below fixes the problem.

Regards

Gabor

--- command.c-orig	2008-08-26 14:43:16.037456000 +0200
+++ command.c	2008-08-26 17:44:36.935945453 +0200
@@ -263,6 +263,28 @@
   return 0;
 }
 
+/* Convert (in place) an already parsed hexstring of
+ * 'len' digits to native bytes. */
+#define fromhex(h) ( (h)<='9' ? (h)-'0' : ((h)|0x20)-'a'+10 )
+static char *
+decode_hexstring (char *string, int len)
+{
+  unsigned char *from, *to;
+
+  for (from=to=(unsigned char*)string; len>0; to++)
+    {
+      unsigned char value;
+      value = fromhex(*from);
+      from++;
+      value <<=  4;
+      value |= fromhex(*from);
+      from++;
+      *to = value;
+      len -= 2;
+    }
+  return string;
+}
+
 /* Parse the keygrip in STRING into the provided buffer BUF.  BUF must
    provide space for 20 bytes. BUF is not changed if the function
    returns an error. */
@@ -1135,7 +1157,10 @@
   /* If there is a passphrase, use it.  Currently, a passphrase is
      required.  */
   if (*line)
-    passphrase = line;
+    {
+      passphrase = decode_hexstring(line, len);
+      passphrase[len/2] = '\0';
+    }
   else
     return gpg_error (GPG_ERR_NOT_IMPLEMENTED);