FreeBSD Security Advisory FreeBSD-SA-03:01.cvs

From: FreeBSD Security Advisories (security-advisories@freebsd.org)
Date: 02/04/03

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From: FreeBSD Security Advisories <security-advisories@freebsd.org>
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    =============================================================================
    FreeBSD-SA-03:01.cvs Security Advisory
                                                              The FreeBSD Project

    Topic: remotely exploitable vulnerability in cvs server

    Category: contrib
    Module: contrib_cvs
    Announced: 2003-02-04
    Credits: Stefan Esser <s.esser@e-matters.de>
    Affects: All FreeBSD versions prior to 4.6-RELEASE-p7, 4.7-RELEASE-p4,
                    5.0-RELEASE-p1
    Corrected: 2003-01-21 22:26:46 UTC (RELENG_4)
                    2003-02-04 18:05:07 UTC (RELENG_5_0)
                    2003-02-04 18:07:20 UTC (RELENG_4_7)
                    2003-02-04 18:08:26 UTC (RELENG_4_6)
    FreeBSD only: NO

    I. Background

    The Concurrent Versions System (CVS) is a version control system. It
    may be used to access a repository locally, or to access a `remote
    repository' using several different methods, including `ext' (rsh),
    and `pserver' (password-authenticated server). When accessing a
    remote repository, the target machine runs the CVS server to fulfill
    client requests.

    II. Problem Description

    The implementation of the CVS server contains a programming error which
    can lead to a block of memory being freed more than once (i.e. a
    double-free bug).

    Separately, the CVS server allows clients with write access to specify
    arbitrary commands to execute as part of an update (update-prog) or
    commit (checkin-prog). This is a dangerous feature that is generally
    not needed: there are other, safer methods of triggering program
    execution.

    III. Impact

    An attacker may exploit the double-free bug in order to bypass write
    access checks. Combined with the update-prog/checkin-prog feature,
    the attacker may be able to execute arbitrary commands with the
    privileges of the CVS server. The impact is most severe when running
    the CVS server in `pserver' mode to provide read-only access to the
    world (anoncvs).

    IV. Workaround

    Do not use `pserver' mode directly. Instead, use one of the safer
    methods described in the following online resources:

    <URL:http://openbsd.sunsite.ualberta.ca/papers/anoncvs-paper.ps>
    <URL:http://www.netsys.com/library/papers/chrooted-ssh-cvs-server.txt>

    V. Solution

    1) Upgrade your vulnerable system to 4.7-STABLE; or to the RELENG_4_7
    (4.7-RELEASE-p4), RELENG_4_6 (4.6-RELEASE-p7), or RELENG_5_0
    (5.0-RELEASE-p1) security branch dated after the correction date.

    2) To patch your present system:

    The following patch has been verified to apply to FreeBSD 4.6, 4.7, and
    5.0 systems.

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

    # fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-03:01/cvs.patch
    # fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-03:01/cvs.patch.asc

    b) Execute the following commands as root:

    # cd /usr/src
    # patch < /path/to/patch
    # cd /usr/src/gnu/usr.bin/cvs
    # make obj && make depend && make && make install

    VI. Correction details

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

    Path Revision
      Branch
    - -------------------------------------------------------------------------
    src/contrib/cvs/src/server.c
      RELENG_5_0 1.17.2.1
      RELENG_4_7 1.13.2.2.6.1
      RELENG_4_6 1.13.2.2.4.1
    - -------------------------------------------------------------------------

    VII. References

    <URL:http://online.securityfocus.com/archive/1/72584>
    <URL:http://security.e-matters.de/advisories/012003.html>
    <URL:http://ccvs.cvshome.org/servlets/NewsItemView?newsID=51>
    <URL:http://www.kb.cert.org/vuls/id/650937>
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    Relevant Pages

    • [Full-Disclosure] FreeBSD Security Advisory FreeBSD-SA-03:01.cvs
      ... FreeBSD only: NO ... the target machine runs the CVS server to fulfill ... the attacker may be able to execute arbitrary commands with the ... To patch your present system: ...
      (Full-Disclosure)
    • Re: Eclipse and CVS
      ... you should have a running CVS server I think. ... The path to the repository should be the absolute path where the CVSROOT ... The login and password will be those defined for one of the users of your ...
      (comp.lang.java.programmer)
    • Is CVS security on topic for this list?
      ... I'm wondering about the security implications of running a CVS server with group write permission on the repository and various other configuration details. ...
      (FreeBSD-Security)
    • cvs on a iis virtual directory
      ... cvs server because i am working on my own. ... directory for my sandbox or as repository. ...
      (microsoft.public.dotnet.framework.aspnet)