Control character and non-printables check

Added a check for non-printables and control characters, to return -1 (in "err") if found.

lib/fields.c

@@ -22,8 +22,8 @@
  * The supplied field is scanned for non-printable and other illegal
  * characters.
  *  + -1 is returned if an illegal character is present.
- *  +  1 is returned if no illegal characters are present, but the field
- *       contains a non-printable character.
+ *  + -1 is returned if no illegal characters are present, but the field
+ *       contains non-printables or control characters.
  *  +  0 is returned otherwise.
  */
 int valid_field (const char *field, const char *illegal)
@@ -43,12 +43,12 @@ int valid_field (const char *field, const char *illegal)
 			break;
 		}
 	}
-
+	
 	if (0 == err) {
-		/* Search if there are some non-printable characters */
+		/* Search if there are non-printables or control characters */
 		for (cp = field; '\0' != *cp; cp++) {
-			if (!isprint (*cp)) {
-				err = 1;
+			if (!isprint(*cp) || !iscntrl(*cp)) {
+				err = -1;
 				break;
 			}
 		}