OSEC

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From: iDEFENSE Labs (labs_at_idefense.com)
Date: Wed Jan 29 2003 - 11:51:42 CST

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    iDEFENSE Security Advisory 01.28.03: SSH2 Clients Insecurely Store
    Passwords (AbsoluteTelnet, SecureCRT, Entunnel, SecureFx, and PuTTY)
    http://www.idefense.com/advisory/01.28.03.txt
    January 28, 2003

    I. BACKGROUND

    PuTTY is a free implementation of Telnet and SSH for Win32 platforms,
    along with an xterm terminal emulator. More information is available at
    http://www.chiark.greenend.org.uk/~sgtatham/putty/.

    SecureCRT provides security for remote access, file transfer, and data
    tunneling by combining the open Secure Shell protocol with emulation.
    Entunnel provides SSH2 data tunneling (port forwarding) services when
    connected to an SSH2 server. The SecureFX client application is an SFTP
    and FTP over an encrypted SSH2 client. More information is available at
    www.vandyke.com/products.

    AbsoluteTelnet is a terminal client program developed for the Microsoft
    Windows platform. AbsoluteTelnet supports multiple protocols including
    Telnet, SSH1, SSH2, TAPI Dialup and direct COM. More information is
    available at http://www.celestialsoftware.net/telnet/index.html.

    II. DESCRIPTION

    AbsoluteTelnet, SecureCRT, Entunnel, SecureFx, and PuTTY do not properly
    scrub memory allowing an attacker with access to memory or a memory dump
    to retrieve authentication information.

    When connected via SSH2, an attacker can search memory or a memory dump
    for logon credentials. Passwords transmitted by PuTTY can be found by
    searching for the second occurrence of the string "password:". The user's
    password is stored in plaintext shortly after this string. Passwords
    transmitted by SecureCRT can be found by searching for the string
    "ssh-connection". The logon and password is stored in plaintext on the
    respective sides of this keyword. Passwords transmitted by AbsoluteTelnet
    can be found by searching for the first occurrence of the string
    "Password", that lies in a segment of read/write memory. The logon and
    password is stored in plaintext on the respective sides of this keyword.

    III. ANALYSIS

    An attacker able to ascertain a target user's memory dump will be able to
    recover passwords for remote systems. This is of special concern in shared
    environments.

    IV. DETECTION

    iDEFENSE has verified the existence of this vulnerability in the following
    versions of the above mentioned clients:

    • AbsoluteTelnet: latest (2.11)
    • SecureCRT: latest (4.0.2) and 3.4.6
    • SecureFX : 2.1.2 and 2.0.4
    • Entunnel: 1.0.2 and earlier
    • PuTTY: latest (0.53b)

    Earlier versions of the tested clients as well as other clients may be
    vulnerable as well.

    V. VENDOR RESPONSE(S)/FIX

    Current development snapshots of PuTTY are believed to have this problem
    fixed. Unfortunately, we are in the middle of heavy code restructuring and
    not currently in a position to make a stable release, but the current
    snapshots should be good enough for anyone for whom this is a problem.
    - ---------------
    The SSH password vulnerability discovered by iDEFENSE has been found to
    exist in all versions of AbsoluteTelnet prior to (and including) version
    2.11.

    Version 2.12, which Celestial Software will make available as a FREE
    update to ALL existing users, fixes the problem by keeping password memory
    "scrubbed" and free of plaintext copies of the password.

    Version 2.12 is currently in beta testing pending the beta test group's
    acceptance of the changes it contains. Upon release, it will be available
    for download at the Celestial Software website:

    http://www.celestialsoftware.net/telnet

    For a sneak peak at the 2.12 beta, go here:

    http://www.celestialsoftware.net/telnet/beta_software.html

    Thanks to iDEFENSE for bringing this to my attention and for allowing
    adequate time to make corrections! In particular, thanks to David Endler
    for staying on top of this!
    - ---------------
    VanDyke Software recognizes the efforts of iDEFENSE in discovering this
    security issue and commends iDEFENSE for the responsible manner in which
    the security issue was made known so as to allow time for revisions to be
    made before the information was released to the public.

    The vulnerability reported by iDEFENSE exists in the following versions of
    VanDyke Software client applications:

        SecureCRT: 4.0.2 and 3.4.7
        SecureFX : 2.1.2 and 2.0.4
        Entunnel: 1.0.2 and earlier

    Earlier versions of these client applications are vulnerable as well.
    VanDyke encourages all users whose licenses were purchased prior to June
    1, 2000 to consider upgrading to the current version(s) of their licensed
    applications.

    Vulnerability fix downloads are available:
        SecureCRT 4.0.3 - http://www.vandyke.com/download/securecrt/index.html
        SecureCRT 3.4.8 -
    http://www.vandyke.com/download/securecrt/3.4/index.html

        SecureFX 2.1.3 - http://www.vandyke.com/download/securefx/index.html
        SecureFX 2.0.5 -
    http://www.vandyke.com/download/securefx/2.0/index.html

        Entunnel 1.0.3 - http://www.vandyke.com/download/entunnel/index.html
    - --------

    VI. CVE INFORMATION

    The Mitre Corp.'s Common Vulnerabilities and Exposures (CVE) Project
    assigned the following identification numbers to these issue:

    CAN-2003-0046 - AbsoluteTelnet
    CAN-2003-0047 - SecureCRT
    CAN-2003-0048 - PuTTY, SecureFx, and Entunnel

    VII. DISCLOSURE TIMELINE

    12/13/2002 Issues disclosed to iDEFENSE
    01/09/2003 puttyprojects.tartarus.org, Mark.Walkervandyke.com, and
                    bpencecelestialsoftware.net notified
    01/09/2003 iDEFENSE clients notified
    01/09/2003 Response received from Simon Tatham [anakinpobox.com]
    01/10/2003 Response received from Celestial Software
                    [bpencemindspring.com]
    01/10/2003 Response received from Van Dyke Software
                    [mark.walkervandyke.com]
    01/28/2003 Coordinated public disclosure

    VIII. CREDIT

    Knud Erik Højgaard (knudskodliv.dk) discovered these vulnerabilities.

    Get paid for security research
    http://www.idefense.com/contributor.html

    Subscribe to iDEFENSE Advisories:
    send email to listservidefense.com, subject line: "subscribe"

    About iDEFENSE:

    iDEFENSE is a global security intelligence company that proactively
    monitors sources throughout the world — from technical
    vulnerabilities and hacker profiling to the global spread of viruses
    and other malicious code. Our security intelligence services provide
    decision-makers, frontline security professionals and network
    administrators with timely access to actionable intelligence
    and decision support on cyber-related threats. For more information,
    visit http://www.idefense.com .

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