[Full-Disclosure] iDEFENSE Security Advisory 09.30.04: Samba Arbitrary File Access Vulnerability

idlabs-advisories_at_idefense.com
Date: 09/30/04

  • Next message: Alexander Antipov: "[Full-Disclosure] Multiple vulnerabilities in w-agora forum" 
    To: <idlabs-advisories@idefense.com>
Date: Thu, 30 Sep 2004 15:01:12 -0400

    Samba Arbitrary File Access Vulnerability

    iDEFENSE Security Advisory 09.30.04
    www.idefense.com/application/poi/display?id=146&type=vulnerabilities
    September 30, 2004

    I. BACKGROUND

    Samba is an Open Source/Free Software suite that provides seamless file
    and print services to SMB/CIFS clients.

    II. DESCRIPTION

    Remote exploitation of an input validation vulnerability in Samba allows
    attackers to access files and directories outside of the specified share
    path.

    Each file and directory name passed into Samba is converted and checked
    with the functions unix_convert() and check_name(). The main purpose of
    the unix_convert() routine is to convert names from the DOS namespace to
    Unix namespace. It calls unix_clean_name(), which in turn removes double
    slashes, leading './' characters and '..' directory-traversal
    characters. check_name() does any final checks necessary to confirm the
    validity of the converted filename and calls reduce_name(), which in
    turn calls unix_clean_name() for a second time. The end result allows
    for an attacker to specify the realpath of any file on the computer.

    Example:
    /./////etc is passed to unix_clean_name(). It becomes /.///etc. The
    leading slash is then trimmed off to make .///etc. It is then passed to
    unix_clean_name() again. The resulting string is /etc, which is an
    absolute path on the system.

    III. ANALYSIS

    Successful exploitation allows remote attackers to bypass the specified
    share restrictions to gain read, write and list access to files and
    directories under the privileges of the user. In situations where a
    public share is available, the attack can be performed by
    unauthenticated attackers.

    An attacker does not need exploit code to exploit this vulnerability.
    The smbclient program can be used to request/write/list files using the
    "get", "put" and "dir" commands, respectively.

    IV. DETECTION

    iDEFENSE has confirmed that Samba versions 3.0.2 and 2.2.9 are
    vulnerable. It is suspected that all versions of Samba are vulnerable.

    V. WORKAROUND

    Only allow trusted users/hosts to connect to samba shares.

    VI. VENDOR RESPONSE

    Samba 2.2.12 upgrade for Samba 2.2.x:
    http://us4.samba.org/samba/ftp/samba-2.2.12.tar.gz

    Samba 3.0.5 patch:
    http://us4.samba.org/samba/ftp/patches/security/samba-3.0.5-reduce_name.
    patch

    Samba 3.0.7 is not vulnerable.

    VII. CVE INFORMATION

    The Common Vulnerabilities and Exposures (CVE) project has assigned the
    names CAN-2004-0815 to these issues. This is a candidate for inclusion
    in the CVE list (http://cve.mitre.org), which standardizes names for
    security problems.

    VIII. DISCLOSURE TIMELINE

    09/22/2004 Initial vendor notification
    09/22/2004 iDEFENSE clients notified
    09/22/2004 Initial vendor response
    09/30/2004 Coordinated public disclosure

    IX. CREDIT

    Karol Wiesek is credited with this discovery.

    Get paid for vulnerability research
    http://www.idefense.com/poi/teams/vcp.jsp

    X. LEGAL NOTICES

    Copyright (c) 2004 iDEFENSE, Inc.

    Permission is granted for the redistribution of this alert
    electronically. It may not be edited in any way without the express
    written consent of iDEFENSE. If you wish to reprint the whole or any
    part of this alert in any other medium other than electronically, please
    email customerservice@idefense.com for permission.

    Disclaimer: The information in the advisory is believed to be accurate
    at the time of publishing based on currently available information. Use
    of the information constitutes acceptance for use in an AS IS condition.
    There are no warranties with regard to this information. Neither the
    author nor the publisher accepts any liability for any direct, indirect,
    or consequential loss or damage arising from use of, or reliance on,
    this information.

    _______________________________________________
    Full-Disclosure - We believe in it.
    Charter: http://lists.netsys.com/full-disclosure-charter.html

  • Next message: Alexander Antipov: "[Full-Disclosure] Multiple vulnerabilities in w-agora forum"

    Relevant Pages