patch 8.2.3247: using uninitialized memory when checking for crypt method

Problem:    Using uninitialized memory when checking for crypt method.
Solution:   Check the header length before using the salt and seed.

Author: brammool

src/fileio.c

@@ -2917,15 +2917,16 @@ check_for_cryptkey(
 	{
 	    int header_len;
 
-	    curbuf->b_cryptstate = crypt_create_from_header(
-						       method, cryptkey, ptr);
-	    crypt_set_cm_option(curbuf, method);
-
-	    // Remove cryptmethod specific header from the text.
 	    header_len = crypt_get_header_len(method);
 	    if (*sizep <= header_len)
 		// invalid header, buffer can't be encrypted
 		return NULL;
+
+	    curbuf->b_cryptstate = crypt_create_from_header(
+							method, cryptkey, ptr);
+	    crypt_set_cm_option(curbuf, method);
+
+	    // Remove cryptmethod specific header from the text.
 	    *filesizep += header_len;
 	    *sizep -= header_len;
 	    mch_memmove(ptr, ptr + header_len, (size_t)*sizep);

src/version.c

@@ -755,6 +755,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    3247,
 /**/
     3246,
 /**/