From sacadmin Wed Aug 29 13:48:26 2007 Received: from sac.sfbay.sun.com (localhost [127.0.0.1]) by sac.sfbay.sun.com (8.13.8+Sun/8.13.8) with ESMTP id l7TKmPeb025055; Wed, 29 Aug 2007 13:48:25 -0700 (PDT) Received: (from alanc@localhost) by sac.sfbay.sun.com (8.13.8+Sun/8.13.8/Submit) id l7TKmPga025051; Wed, 29 Aug 2007 13:48:25 -0700 (PDT) Date: Wed, 29 Aug 2007 13:48:25 -0700 (PDT) From: Alan Coopersmith Message-Id: <200708292048.l7TKmPga025051@sac.sfbay.sun.com> To: PSARC-record@sac.sfbay.sun.com Cc: Alan.Coopersmith@Sun.COM Subject: X11 MIT-SHM Extension across zones [PSARC/2007/500 FastTrack] Status: RO Content-Length: 572 Template Version: @(#)sac_nextcase 1.64 07/13/07 SMI This information is Copyright 2007 Sun Microsystems 1. Introduction 1.1. Project/Component Working Name: X11 MIT-SHM Extension across zones 1.2. Name of Document Author/Supplier: Author: Alan Coopersmith 1.3 Date of This Document: 29 August, 2007 4. Technical Description See the case directory for more detail 6. Resources and Schedule 6.4. Steering Committee requested information 6.4.1. Consolidation C-team Name: X 6.5. ARC review type: FastTrack 6.6. ARC Exposure: open From alan.coopersmith@sun.com Thu Sep 6 14:40:58 2007 Received: from sunmail4.Singapore.Sun.COM (sunmail4.Singapore.Sun.COM [129.158.71.19]) by sac.sfbay.sun.com (8.13.8+Sun/8.13.8) with ESMTP id l86Lev7H008241 for ; Thu, 6 Sep 2007 14:40:57 -0700 (PDT) Received: from nwk-avmta-2.sfbay.sun.com (nwk-avmta-2.SFBay.Sun.COM [129.145.155.6]) by sunmail4.Singapore.Sun.COM (8.13.4+Sun/8.13.3/ENSMAIL,v2.2) with ESMTP id l86Lc8j6012408; Fri, 7 Sep 2007 05:38:09 +0800 (SGT) Received: from pmxchannel-daemon.nwk-avmta-2.sfbay.sun.com by nwk-avmta-2.sfbay.sun.com (Sun Java System Messaging Server 6.2-3.04 (built Jul 15 2005)) id <0JNY00705URK0A00@nwk-avmta-2.sfbay.sun.com>; Thu, 06 Sep 2007 14:38:08 -0700 (PDT) Received: from jurassic.eng.sun.com ([129.146.104.45]) by nwk-avmta-2.sfbay.sun.com (Sun Java System Messaging Server 6.2-3.04 (built Jul 15 2005)) with ESMTP id <0JNY000UGURJ3B70@nwk-avmta-2.sfbay.sun.com>; Thu, 06 Sep 2007 14:38:08 -0700 (PDT) Received: from [129.146.108.211] (almas.SFBay.Sun.COM [129.146.108.211]) by jurassic.eng.sun.com (8.13.8+Sun/8.13.8) with ESMTP id l86Lc7EF981623; Thu, 06 Sep 2007 14:38:07 -0700 (PDT) Date: Thu, 06 Sep 2007 14:38:07 -0700 From: Alan Coopersmith Subject: X11 MIT-SHM Extension across zones [PSARC 2007/500, fast-track timeout 9/13/07] To: PSARC-EXT@sun.com Cc: Glenn Faden Message-id: <46E0733F.7030209@sun.com> MIME-version: 1.0 Content-type: text/plain; charset=ISO-8859-1 Content-transfer-encoding: 7BIT X-PMX-Version: 5.2.0.264296 X-Enigmail-Version: 0.95.1 User-Agent: Thunderbird 2.0.0.4 (X11/20070731) Status: RO Content-Length: 3906 I am sponsoring this fasttrack for myself, and have set the timeout to Thursday, Sept. 13. It requests a patch release binding. This project enhances the X server to allow the MIT-SHM extension to operate between clients in non-global zones and the X server in the global zone. The MIT-SHM extension uses SysV shared memory to transport pixmaps between X clients and X servers without having to write them to the socket or pipe and read them back out. The current Solaris implementation contains two impediments blocking use of this extension between different zones on the same system. 1) access control check in X servers Since the X client tells the X server what shared memory segment it has created for the pixmap and the X server attachs to it with its privilege level/uid (which is usually higher than the client's and often at least different from the client), the X server first verifies the client isn't asking it to connect to a segment the client shouldn't have access to. It uses getpeerucred() to get the client credentials, and shmctl() to get the ownership and permissions of the shared memory segment and compares to make sure the credentials returned by shmctl should be able to perform the requested access (depending on the operation, either read-only or read-write), If getpeerucred() fails, or if the zoneid returned by getpeerucred does not match the zone returned by getzoneid(), access will only be allowed if the shared memory segment may be read (and if needed, written) by "other". This project modifies the check so that instead of requiring the client zoneid to match the X server's, it uses the shmctl64() function to get the zoneid that created the shared memory segment and compares the client's zone to that zone. If that matches, then the clients uid & gid may be used to verify access, otherwise the client will still be restricted to shared memory segments using the "other" access permissions. Since shmctl64() is a Project Private function in libc, this project includes a contract between the X team and the Zones team allowing cross-consolidation use of this interface. 2) XShmQueryExtension() in libXext To avoid telling clients they can use MIT-SHM when the connection to the Xserver is remote, XShmQueryExtension() in libXext returns False if it believes the X server is on another machine. The current algorithm used is: if stat(display_connection) returns a mode of S_IFIFO connection is local else getpeername(display_connection) if socket_family is AF_UNIX connection is local else for each local interface returned by SIOCGLIFCONF ioctl if address == peer socket address connection is local and if none of those find the connection is local, the function reports that MIT-SHM is not connected. This project greatly simplifies the above algorithm to a single check: if getpeerucred(display_connection) == 0 && ucred_getzoneid() != -1 connection is local else connection is remote Interfaces Imported: ==================== Interface: Stability: Definition/Comments: ------------------------------------------------------------------------------ shmctl64() Contracted Project Private [1], [2] getpeerucred() Evolving PSARC 2003/197, PSARC 2004/336 Interfaces Exported: ==================== no new interfaces exported References: [1] shmctl64.txt in case materials directory [2] contract-01.txt in case materials directory -- -Alan Coopersmith- alan.coopersmith@sun.com Sun Microsystems, Inc. - X Window System Engineering