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  • [FreeBSD-Announce] FreeBSD Errata Notice FreeBSD-EN-20:01.ssp

    From FreeBSD Errata Notices@21:1/5 to All on Tue Jan 28 21:00:01 2020
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    ============================================================================= FreeBSD-EN-20:01.ssp Errata Notice
    The FreeBSD Project

    Topic: Imprecise ordering of SSP canary initialization

    Category: core
    Module: libc
    Announced: 2020-01-28
    Credits: Kyle Evans
    Affects: All supported versions of FreeBSD.
    Corrected: 2019-11-25 03:49:38 UTC (stable/12, 12.1-STABLE)
    2020-01-28 18:53:14 UTC (releng/12.1, 12.1-RELEASE-p2)
    2020-01-28 18:53:14 UTC (releng/12.0, 12.0-RELEASE-p13)
    2019-11-25 03:49:38 UTC (stable/11, 11.3-STABLE)
    2020-01-28 18:53:14 UTC (releng/11.3, 11.3-RELEASE-p6)

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

    I. Background

    The Stack Smashing Protector ("SSP") relies on a stack canary being
    initialized early on in application startup. On FreeBSD, this is
    accomplished with a constructor in libc.

    II. Problem Description

    When a binary is statically linked, constructor invocation order is based on priority and sorted arbitrarily within a priority level across all
    constructors present in the single statically linked object. The stack
    canary guard constructor had no priority, so statically linked binary could
    not predictably order their constructors to avoid bad interactions with
    respect to the stack canary constructor leading to false-positive detection
    of a stack overflow condition and erroneous process abort in some rare cases.

    Dynamically linked binaries are generally not affected, since the stack
    canary is initialized in libc and libc is ordered very early in constructor invocation.

    III. Impact

    Affected programs will abort and log a "stack overflow detected" message to syslog(3).

    IV. Workaround

    No workaround is available, but dynamically linked binaries are not affected.

    V. Solution

    Upgrade your system to a supported FreeBSD stable or release / security
    branch (releng) dated after the correction date. Statically linked binaries should be relinked against the updated base system.

    Perform one of the following:

    1) To update your system via a binary patch:

    Systems running a RELEASE version of FreeBSD on the i386 or amd64
    platforms can be updated via the freebsd-update(8) utility:

    # freebsd-update fetch
    # freebsd-update install

    2) To update your system via a source code patch:

    The following patches have been verified to apply to the applicable
    FreeBSD release branches.

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

    # fetch https://security.FreeBSD.org/patches/EN-20:01/ssp.patch
    # fetch https://security.FreeBSD.org/patches/EN-20:01/ssp.patch.asc
    # gpg --verify ssp.patch.asc

    b) Apply the patch. Execute the following commands as root:

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

    c) Recompile the operating system using buildworld and installworld as described in <URL:https://www.FreeBSD.org/handbook/makeworld.html>.

    VI. Correction details

    The following list contains the correction revision numbers for each
    affected branch.

    Branch/path Revision
    - ------------------------------------------------------------------------- stable/12/ r355080 releng/12.1/ r357215 releng/12.0/ r357215 stable/11/ r355080 releng/11.3/ r357215
    - -------------------------------------------------------------------------

    To see which files were modified by a particular revision, run the
    following command, replacing NNNNNN with the revision number, on a
    machine with Subversion installed:

    # svn diff -cNNNNNN --summarize svn://svn.freebsd.org/base

    Or visit the following URL, replacing NNNNNN with the revision number:

    <URL:https://svnweb.freebsd.org/base?view=revision&revision=NNNNNN>

    VII. References

    <URL:https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=241905>

    The latest revision of this advisory is available at <URL:https://security.FreeBSD.org/advisories/FreeBSD-EN-20:01.ssp.asc> -----BEGIN PGP SIGNATURE-----

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