Mailing-List: contact cygwin-developers-help AT sourceware DOT cygnus DOT com; run by ezmlm
List-Subscribe: <mailto:cygwin-developers-subscribe AT sources DOT redhat DOT com>
List-Archive: <http://sources.redhat.com/ml/cygwin-developers/>
List-Post: <mailto:cygwin-developers AT sources DOT redhat DOT com>
List-Help: <mailto:cygwin-developers-help AT sources DOT redhat DOT com>, <http://sources.redhat.com/ml/#faqs>
Sender: cygwin-developers-owner AT sources DOT redhat DOT com
Delivered-To: mailing list cygwin-developers AT sources DOT redhat DOT com
Date: Wed, 18 Apr 2001 19:04:08 +0400
From: egor duda <deo AT logos-m DOT ru>
X-Mailer: The Bat! (v1.45) Personal
Reply-To: egor duda <cygwin-developers AT cygwin DOT com>
Organization: deo
X-Priority: 3 (Normal)
Message-ID: <53342543912.20010418190408@logos-m.ru>
To: Corinna Vinschen <cygwin-developers AT cygwin DOT com>
Subject: Re: handle protection - please comment
In-reply-To: <20010418164712.J15005@cygbert.vinschen.de>
References: <EA18B9FA0FE4194AA2B4CDB91F73C0EF79C2 AT itdomain002 DOT itdomain DOT net DOT au>
 <20010418120530 DOT Q15962 AT cygbert DOT vinschen DOT de>
 <00a401c0c7f0$02bb1f30$0200a8c0 AT lifelesswks>
 <13327115627 DOT 20010418144700 AT logos-m DOT ru>
 <20010418155552 DOT S15962 AT cygbert DOT vinschen DOT de>
 <175340295909 DOT 20010418182640 AT logos-m DOT ru>
 <20010418164712 DOT J15005 AT cygbert DOT vinschen DOT de>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit

Hi!

Wednesday, 18 April, 2001 Corinna Vinschen vinschen AT redhat DOT com wrote:

>> the problem is that if i (process B) have handle of process with only
>> PROCESS_DUP_HANDLE access, and process A have at least one private
>> handle of itself with full access, i can elevate my privileges
>> using the code quoted above. for cygwin programs the second thing is
>> true -- every process has hMainProcess handle of itself. It won't give
>> it to me, sure, but i can just try to guess it. i'll start duplicating
>> all values 0x4,0x8,0xc,0x10,... (remember, i can duplicate handles
>> from process  A), and sooner or later i'll find hMainProcess. voila,
>> process B have all access to process' A address space.

CV> I see. But that's a Cygwin specific problem only, AFAICS. Since
CV> `_dll_crt0' creates hMainProc as a duplicate of `GetCurrentProcess()'
CV> all processes have a real process handle to itself with full access
CV> rights which could be duplicated by other processes. I'm not sure
CV> why this is done because the return value of `GetCurrentProcess()'
CV> should fit our needs and it can neither be duplicated nor used by
CV> other processes.

well, we can remove or restrict rights on hMainProcess, but it'll just
make exploit a bit harder.
for example, process A may need to open some sensitive file he has
access to, and process B will be able to duplicate it.
Or i'll wait till some process calls fork(), and duplicate child's handle
it's got from CreateProcess()

Egor.            mailto:deo AT logos-m DOT ru ICQ 5165414 FidoNet 2:5020/496.19