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Sendmail-SA-200609-01                                       Security Advisory
                                                               Sendmail, Inc.

Topic: OpenSSL RSA Signature Forgery

Class:          Policy Bypass
Severity:       High
Announced:      2006-10-02 09:00 PDT
Affects:        Sendmail Proxy 2.2.4 and earlier
                Sendmail Switch 3.2.4 and earlier
                Sendmail Switch for Windows 3.1.5 and earlier
                Sendmail Switch 3.1.10 and earlier
                Intelligent Quarantine 3.0 (includes Switch)
                Sendmail Advanced Message Store (SAMS) (includes Switch)
                Sendmail Sentrion 1.5.4 and earlier
                Mailstream Gatekeeper (includes Sentrion OS)
                Mailstream Governor (includes Sentrion OS)
                Sendmail Pro all versions
Resolved:       Sendmail Proxy 2.2.5
                Sendmail Switch 3.2.5
                Sendmail Switch for Windows 3.1.6
                Sendmail Switch 3.1.11
                Sendmail Sentrion 1.5.5

For general information regarding Sendmail, Inc. Security Advisories,
including descriptions of the fields above, other security advisories,
and the following sections, please visit <http://www.sendmail.com/security/>.


I. Background

    Both the sendmail MTA (part of several Sendmail products such
    as Sendmail Switch, Sendmail Advanced Message Store (SAMS), and
    Sentrion) and the Sendmail Proxy server (included with Sendmail
    Advanced Message Store (SAMS)) have the ability to accept SSL
    connections and validate client-side certificates sent to the MTA or
    Proxy server.  The MTA can also initiate SSL connects and validate
    server-side certificates.  This is accomplished using the OpenSSL
    library.


II. Problem Description

    The OpenSSL Project recently released a security advisory announcing
    that it was possible to forge certificates for certain types of
    certificate authorities.  More details regarding the vulnerability
    can be found in their advisory, referenced below.


III. Impact

    The sendmail MTA and Sendmail Proxy server can optionally request
    and validate an SSL certificate to identify the connecting client
    or server.  This validation is used to make policy decisions, such
    as whether to accept the connection, allow relaying, digitally sign
    the message, etc.  Due to the OpenSSL bug, this validation can be
    subverted and the attacker can bypass policy restrictions.

    Note that this bug only affects sites using an exponent 3
    certificate authority.  You can check the exponent type used with
    the command:

      /usr/local/sendmail/smmta-8.13/sbin/openssl x509 -text -in cacert.pem | grep Exponent


IV. Workaround

    If you are using an exponent 3 certificate authority and are unable
    to install the patch immediately, you can work around this problem
    by employing alternative methods of validating connections, such as
    SMTP authentication for MTA related policy.


V. Solution

    Sendmail, Inc. has released patches for Sendmail Proxy, Switch,
    and Sentrion to address this problem.  The patch incorporates the
    software fix provided by the OpenSSL project.

    Those patches are available to supported customers on their download
    site at:

      https://www.sendmail.com/customerlogin/

    All customers can download the patches from:

      ftp://ftp.sendmail.com/patch/

    Refer to the README included with each patch for installation
    instructions.  The checksums for the available patches are:

    MD5 (smproxy-patch-2.2.5-Linux.tar.gz) = 35cfc377c0080102e7c125f4532a2679
    MD5 (smproxy-patch-2.2.5-Solaris.tar.Z) = 34f79cffe304a77b7e9304ac8d77f7f5
    MD5 (smswitch-patch-3.1.6-Windows.zip) = 66482522ae2825911affe95db467908b
    MD5 (smswitch-patch-3.1.11-Linux.tar.gz) = 9f1f595fca3ff5ddc84939fbdf2fffd9
    MD5 (smswitch-patch-3.1.11-Solaris8.tar.Z) = 76072644f79d098dc5989c0ac4226bd8
    MD5 (smswitch-patch-3.2.5-Linux.tar.gz) = 6188c2f4d1aae41bc062278bd3dbfd60
    MD5 (smswitch-patch-3.2.5-Solaris8.tar.Z) = 90dc22433e492b4c40bc3869c72aef30
    MD5 (SentriOS-1.5.5-906.tar) = 0a73437a1b6c9f3c4912010b2084775c


VI. References

      CVE: http://www.cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2006-4339

      OpenSSL Advisory: http://www.openssl.org/news/secadv_20060905.txt

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