[NEWS] SSH2 Clients Insecurely Store Passwords (AbsoluteTelnet, SecureCRT, Entunnel, SecureFx, and PuTTY)

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Date: 01/29/03

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      SSH2 Clients Insecurely Store Passwords (AbsoluteTelnet, SecureCRT,
    Entunnel, SecureFx, and PuTTY)
    ------------------------------------------------------------------------

    SUMMARY

    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/>
    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
    <http://www.vandyke.com/products> http://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>
    http://www.celestialsoftware.net/telnet/index.html.

    A vulnerability in the products allows a local attacker to gain access the
    passwords protected by the products.

    DETAILS

    Vulnerable systems:
    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.

    Details:
    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.

    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.

    Vendor response(s) / Fix(es):
    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>
    http://www.celestialsoftware.net/telnet

    For a sneak peak at the 2.12 beta, go here:
    <http://www.celestialsoftware.net/telnet/beta_software.html>
    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 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>
    http://www.vandyke.com/download/securecrt/index.html
     * SecureCRT 3.4.8 -
    <http://www.vandyke.com/download/securecrt/3.4/index.html>
    http://www.vandyke.com/download/securecrt/3.4/index.html

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

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

    Disclosure timeline:
    12/13/2002 Issues disclosed to iDEFENSE
    01/09/2003 putty@projects.tartarus.org, Mark.Walker@vandyke.com, and
    bpence@celestialsoftware.net notified
    01/09/2003 iDEFENSE clients notified
    01/09/2003 Response received from Simon Tatham [anakin@pobox.com]
    01/10/2003 Response received from Celestial Software
    [bpence@mindspring.com]
    01/10/2003 Response received from Van Dyke Software
    [mark.walker@vandyke.com]
    01/28/2003 Coordinated public disclosure

    ADDITIONAL INFORMATION

    The original advisory can be downloaded from:
     <http://www.idefense.com/advisory/01.28.03.txt>
    http://www.idefense.com/advisory/01.28.03.txt

    The information has been provided by <mailto:listserv@idefense.com>
    iDEFENSE Labs, the vulnerabilities were discovered by
    <mailto:knud@skodliv.dk> Knud Erik Højgaard.

    ========================================

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