AusCERT - AA-97.28 -- Vulnerability in GlimpseHTTP and WebGlimpse cgi-bin Packages

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AA-97.28 -- Vulnerability in GlimpseHTTP and WebGlimpse cgi-bin Packages
Date: 14 November 1997

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AA-97.28                        AUSCERT Advisory
        Vulnerability in GlimpseHTTP and WebGlimpse cgi-bin Packages
                                14 November 1997

Last Revised: --

- ---------------------------------------------------------------------------

The Australian Computer Emergency Response Team (AUSCERT) has received
information about vulnerabilities in the GlimpseHTTP and WebGlimpse cgi-bin 
packages.

AUSCERT is currently receiving reports of intruders exploiting these
vulnerabilities.

AUSCERT recommends that sites that have either of these packages installed
take the steps outlined in Section 3 as soon as possible.

- ---------------------------------------------------------------------------

1.  Description

    AUSCERT has received information that vulnerabilities exist in the
    GlimpseHTTP and WebGlimpse packages.  Both of these packages provide
    a web interface which allows you to use Glimpse, an indexing and query
    system, to provide a search facility for your web site.

    The cgi-bin programs in these packages perform insufficient argument
    checking.  Due to this, intruders may be able to execute arbitrary
    commands with the privileges of the httpd process.

    GlimpseHTTP 2.0 is known to be vulnerable in this fashion.  The authors
    of GlimpseHTTP and WebGlimpse also believe earlier versions of both
    GlimpseHTTP (prior to 2.0) and WebGlimpse (prior to 1.5) may be
    vulnerable to similar attacks.   WebGlimpse version 1.5 addresses the
    vulnerabilities in both of these packages.

    In particular, AUSCERT is receiving reports of attacks using the
    aglimpse cgi-bin program (part of GlimpseHTTP).  To check whether
    exploitation of the GlimpseHTTP vulnerability has been attempted
    against your site, search for accesses to the aglimpse program in your
    access logs.  An example of how to do this is:

        # egrep -i 'aglimpse.*(||IFS)' {WWW_HOME}/logs/access_log

    Where {WWW_HOME} is the base directory for your web server.
    
    If this command returns anything, further investigation is necessary.

    Both GlimpseHTTP and WebGlimpse are commonly used packages and sites
    are encouraged to check for aglimpse (part of GlimpseHTTP) and
    webglimpse (part of WebGlimpse).  If either GlimpseHTTP or WebGlimpse
    is installed it is recommended that the workarounds given in section
    3 are applied.

    Up-to-date information regarding this vulnerability has been made
    available by the authors of GlimpseHTTP and WebGlimpse.  It is
    available from:

	http://glimpse.cs.arizona.edu/security.html

2.  Impact

    Remote users may be able to execute arbitrary commands with the
    privileges of the httpd process which answers HTTP requests.  This
    may be used to compromise the http server and under certain
    configurations gain privileged access.

3.  Workarounds/Solution

    GlimpseHTTP 2.0 is known to be affected by the vulnerability described
    in this advisory.  The authors of GlimpseHTTP and WebGlimpse also
    believe earlier versions of both GlimpseHTTP (prior to 2.0) and
    WebGlimpse (prior to 1.5) should be considered vulnerable to similar
    attacks.

    Information on removing the GlimpseHTTP and WebGlimpse vulnerabilities
    described in this advisory may be found in Sections 3.2 and 3.3.

    Until these packages can be upgraded it is advised that the functionality
    provided by these packages be disabled (Section 3.1).

3.1 Remove execute permissions

    To prevent the exploitation of the vulnerabilities described in this
    advisory, AUSCERT recommends that the execute permissions for all
    cgi-bin programs associated with GlimpseHTTP and WebGlimpse be removed.
    Note that this will have the side effect of preventing the search
    facilities provided by these packages from functioning.

3.2 Replacing GlimpseHTTP with WebGlimpse

    GlimpseHTTP is no longer supported and its authors recommend that
    sites replace it with the current version of the WebGlimpse package
    (see Section 3.3).  Sites should ensure that all programs related to
    GlimpseHTTP are removed or disabled prior to installing the WebGlimpse
    package.

3.3 Upgrading to the current version of WebGlimpse

    A new version of WebGlimpse has been released which addresses the
    vulnerabilities described in this advisory.  Sites using WebGlimpse
    should upgrade to the current version, which at the moment is 1.5
    (released on 13 November 1997).  It can be retrieved from:

	ftp://ftp.cs.arizona.edu/glimpse/webglimpse-1.5.src.tar.gz

    More information on WebGlimpse may be found at:

	http://glimpse.cs.arizona.edu/webglimpse/

4.  Additional measures

    It is important to note that attacks similar to this may succeed
    against any CGI program which has not been written with due consideration
    for security.  Sites using HTTP servers, and in particular CGI
    applications, are encouraged to develop an understanding of the security
    issues involved.

    Sites should consider taking this opportunity to examine their httpd
    configuration and web servers.  In particular, all CGI programs that
    are not required should be removed, and all those remaining should be
    examined for possible security vulnerabilities.

    It is also important to ensure that all child processes of httpd are
    running as a non-privileged user.  This is often a configurable option.
    See the documentation for your httpd distribution for more details.

    Numerous resources relating to WWW security are available.  The following
    pages may provide a useful starting point.  They include links describing 
    general WWW security, secure httpd setup and secure CGI programming.

        W3C Security Resources (including WWW Security FAQ):
                http://www.w3.org/Security/

        NSCA's "Security Concerns on the Web" Page:
                http://hoohoo.ncsa.uiuc.edu/security-1.0/

    The following books contain useful information on Web security
    including sections on secure programming techniques.

        "Web Security Sourcebook", Aviel Rubin, Daniel Geer and Marcus Ranum,
        John Wiley & Sons, Inc., 1997.

	"Web Security & Commerce", Simson Garfinkel with Gene Spafford,
	O'Reilly and Associates, 1997.

    CERT/CC have also produced a document describing how to sanitise
    user-supplied data to cgi-bin programs.  This can be retreived from:

	ftp://ftp.cert.org/pub/tech_tips/cgi_metacharacters	
	ftp://ftp.auscert.org.au/pub/cert/tech_tips/cgi_metacharacters

    Please note that the URLs and books referenced in this advisory are
    not under AUSCERT's control and therefore AUSCERT cannot be responsible
    for their availability or content.

- ---------------------------------------------------------------------------
AUSCERT thanks Udi Manber and CERT/CC for their assistance in the
preparation of this advisory.  Thanks also to Stephane Bortzmeyer for the
initial report to the authors of GlimpseHTTP.
- ---------------------------------------------------------------------------

The AUSCERT team have made every effort to ensure that the information
contained in this document is accurate.  However, the decision to use the
information described is the responsibility of each user or organisation.
The appropriateness of this document for an organisation or individual
system should be considered before application in conjunction with local
policies and procedures.  AUSCERT takes no responsibility for the
consequences of applying the contents of this document.

If you believe that your system has been compromised, contact AUSCERT or
your representative in FIRST (Forum of Incident Response and Security
Teams).

AUSCERT is located at The University of Queensland within the Prentice
Centre.  AUSCERT is a full member of the Forum of Incident Response and
Security Teams (FIRST).

AUSCERT maintains an anonymous FTP service which is found on:
ftp://ftp.auscert.org.au/pub/.  This archive contains past SERT and AUSCERT
Advisories, and other computer security information.

AUSCERT also maintains a World Wide Web service which is found on:
http://www.auscert.org.au/.

Internet Email: auscert@auscert.org.au
Facsimile:	(07) 3365 4477
Telephone:	(07) 3365 4417 (International: +61 7 3365 4417)
		AUSCERT personnel answer during Queensland business hours
		which are GMT+10:00 (AEST).
		On call after hours for emergencies.

Postal:
Australian Computer Emergency Response Team
Prentice Centre
The University of Queensland
Brisbane
Qld.  4072.
AUSTRALIA


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