Fix bug #7669.

Fix bug #7669.

Fix bug #7669 (buffer overflow in sid_parse() in Samba3 and dom_sid_parse in
Samba4).

CVE-2010-3069:

===========
Description
===========

All current released versions of Samba are vulnerable to
a buffer overrun vulnerability. The sid_parse() function
(and related dom_sid_parse() function in the source4 code)
do not correctly check their input lengths when reading a
binary representation of a Windows SID (Security ID). This
allows a malicious client to send a sid that can overflow
the stack variable that is being used to store the SID in the
Samba smbd server.

A connection to a file share is needed to exploit this
vulnerability, either authenticated or unauthenticated
(guest connection).
(cherry picked from commit df20a300758bc12286820e31fcf573bdfc2147bc)