FreeBSD Security Advisory FreeBSD-SA-05:02.sendfile

From: FreeBSD Security Advisories (security-advisories_at_freebsd.org)
Date: 04/05/05

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    =============================================================================
    FreeBSD-SA-05:02.sendfile Security Advisory
                                                              The FreeBSD Project

    Topic: sendfile kernel memory disclosure

    Category: core
    Module: sys_kern
    Announced: 2005-04-04
    Credits: Sven Berkvens <sven@berkvens.net>
                    Marc Olzheim <zlo@zlo.nu>
    Affects: All FreeBSD 4.x releases
                    All FreeBSD 5.x releases prior to 5.4-RELEASE
    Corrected: 2005-04-04 23:52:02 UTC (RELENG_5, 5.4-STABLE)
                    2005-04-04 23:52:35 UTC (RELENG_5_4, 5.4-RELEASE)
                    2005-04-04 23:53:24 UTC (RELENG_5_3, 5.3-RELEASE-p7)
                    2005-04-04 23:53:36 UTC (RELENG_4, 4.11-STABLE)
                    2005-04-04 23:53:56 UTC (RELENG_4_11, 4.11-RELEASE-p2)
                    2005-04-04 23:54:13 UTC (RELENG_4_10, 4.10-RELEASE-p7)
                    2005-04-04 23:54:33 UTC (RELENG_4_8, 4.8-RELEASE-p29)
    CVE Name: CAN-2005-0708

    For general information regarding FreeBSD Security Advisories,
    including descriptions of the fields above, security branches, and the
    following sections, please visit
    <URL:http://www.freebsd.org/security/>.

    I. Background

    The sendfile(2) system call allows a server application (such as an HTTP
    or FTP server) to transmit the contents of a file over a network
    connection without first copying it to application memory. High
    performance servers such as Apache and ftpd use sendfile.

    II. Problem Description

    If the file being transmitted is truncated after the transfer has
    started but before it completes, sendfile(2) will transfer the contents
    of more or less random portions of kernel memory in lieu of the
    missing part of the file.

    III. Impact

    A local user could create a large file and truncate it while
    transferring it to himself, thus obtaining a copy of portions of system
    memory to which he would normally not have access. Such memory might
    contain sensitive information, such as portions of the file cache or
    terminal buffers. This information might be directly useful, or it
    might be leveraged to obtain elevated privileges in some way. For
    example, a terminal buffer might include a user-entered password.

    IV. Workaround

    No known workaround.

    V. Solution

    Perform one of the following:

    1) Upgrade your vulnerable system to 4-STABLE or 5-STABLE, or to the
    RELENG_5_3, RELENG_4_11, RELENG_4_10, or RELENG_4_8 security branch
    dated after the correction date.

    2) To patch your present system:

    The following patches have been verified to apply to FreeBSD 4.8, 4.10,
    4.11, and 5.3 systems.

    a) Download the relevant patch from the location below, and verify the
    detached PGP signature using your PGP utility.

    [FreeBSD 4.x]
    # fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-05:02/sendfile_4.patch
    # fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-05:02/sendfile_4.patch.asc

    [FreeBSD 5.3]
    # fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-05:02/sendfile_5.patch
    # fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-05:02/sendfile_5.patch.asc

    b) Apply the patch.

    # cd /usr/src
    # patch < /path/to/patch

    c) Recompile your kernel as described in
    <URL:http://www.freebsd.org/handbook/kernelconfig.html> and reboot the
    system.

    VI. Correction details

    The following list contains the revision numbers of each file that was
    corrected in FreeBSD.

    Branch Revision
      Path
    - -------------------------------------------------------------------------
    RELENG_4
      src/sys/ufs/ffs/ffs_inode.c 1.56.2.6
    RELENG_4_11
      src/UPDATING 1.73.2.91.2.3
      src/sys/conf/newvers.sh 1.44.2.39.2.6
      src/sys/ufs/ffs/ffs_inode.c 1.56.2.5.12.1
    RELENG_4_10
      src/UPDATING 1.73.2.90.2.8
      src/sys/conf/newvers.sh 1.44.2.34.2.8
      src/sys/ufs/ffs/ffs_inode.c 1.56.2.5.10.1
    RELENG_4_8
      src/UPDATING 1.73.2.80.2.33
      src/sys/conf/newvers.sh 1.44.2.29.2.29
      src/sys/ufs/ffs/ffs_inode.c 1.56.2.5.6.1
    RELENG_5
      src/sys/ufs/ffs/ffs_inode.c 1.93.2.2
    RELENG_5_4
      src/UPDATING 1.342.2.24.2.1
      src/sys/ufs/ffs/ffs_inode.c 1.93.2.1.2.1
    RELENG_5_3
      src/UPDATING 1.342.2.13.2.10
      src/sys/conf/newvers.sh 1.62.2.15.2.12
      src/sys/ufs/ffs/ffs_inode.c 1.93.4.1
    - -------------------------------------------------------------------------

    The latest revision of this advisory is available at
    ftp://ftp.freebsd.org/pub/CERT/advisories/FreeBSD-SA-05:02.sendfile.asc
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