From owner-freebsd-security@FreeBSD.ORG Mon Jun 2 08:37:28 2003 Return-Path: Delivered-To: freebsd-security@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 3B10637B401 for ; Mon, 2 Jun 2003 08:37:28 -0700 (PDT) Received: from pyroxene.sentex.ca (pyroxene.sentex.ca [199.212.134.18]) by mx1.FreeBSD.org (Postfix) with ESMTP id 8091243F93 for ; Mon, 2 Jun 2003 08:37:27 -0700 (PDT) (envelope-from mike@sentex.net) Received: from simian.sentex.net (simeon.sentex.ca [192.168.43.27]) by pyroxene.sentex.ca (8.12.9/8.12.8) with ESMTP id h52FbQ8D020096 for ; Mon, 2 Jun 2003 11:37:26 -0400 (EDT) (envelope-from mike@sentex.net) Message-Id: <5.2.0.9.0.20030602113454.047e4088@209.112.4.2> X-Sender: mdtpop@209.112.4.2 (Unverified) X-Mailer: QUALCOMM Windows Eudora Version 5.2.0.9 Date: Mon, 02 Jun 2003 11:36:53 -0400 To: security@freebsd.org From: Mike Tancsa Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; format=flowed X-Virus-Scanned: By Sentex Communications (lava/20020517) Subject: sbsize and local DoS issue via kernel panic X-BeenThere: freebsd-security@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Security issues [members-only posting] List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 02 Jun 2003 15:37:28 -0000 I noticed with active ftp clients (specifically IMP's .forward modification plugin), an sbsize of something under 32M in /etc/login.conf on the target server now gives Can't create data socket (M-^A> (^A,_^R(^C): No buffer space available. in the ftp logs. What is a safe value to prevent users from abusing the system by eating up all mbufs ? There is a local DoS if sbsize was left as unlimited. (http://groups.google.ca/groups?hl=en&lr=&ie=UTF-8&oe=UTF-8&threadm=20000603234039.X17973_fw.wintelcom.net%40ns.sol.net&rnum=2&prev=/groups%3Fhl%3Den%26lr%3D%26ie%3DUTF-8%26oe%3DUTF-8%26q%3Dsbsize%2Bfreebsd%2Bdos) 32MB seems like an oddly large number for just a small ftp session. This changed sometime between Jan 21st and Feb 15th it would seem. Previously an sbzise of :sbsize=512K:\ would work just fine. Not sure if its ftpd or something in the kernel ? Is there any way for an active ftp session to work as well as protecting my system from a local DoS ? ---Mike -------------------------------------------------------------------- Mike Tancsa, tel +1 519 651 3400 Sentex Communications, mike@sentex.net Providing Internet since 1994 www.sentex.net Cambridge, Ontario Canada www.sentex.net/mike