__________________________________________________________ The U.S. Department of Energy Computer Incident Advisory Capability ___ __ __ _ ___ / | /_\ / \___ __|__ / \ \___ __________________________________________________________ INFORMATION BULLETIN SSH Tectia Server Private Key Permission Vulnerability in Windows [SSH Vendor Reference Number: RQ#11775] July 20, 2005 19:00 GMT Number P-257 ______________________________________________________________________________ PROBLEM: When SSH Tectia Server in Windows generates a host identification key (the Secure Shell host key), it sets insufficient file permissions. PLATFORM: SSH Secure Shell for Windows Servers (all versions) SSH Tectia Server (Windows) 4.3.1 and older versions Other than Windows versions are NOT affected. DAMAGE: Any user who has been successfully authenticated to the server and can access the local file system, can also access the Windows server's host identification key (the Secure Shell host key) without having administrative privileges. Also, it can potentially be used to collect passwords. SOLUTION: Upgrade to the appropriate version. ______________________________________________________________________________ VULNERABILITY The risk is LOW. This exploit would require also other active ASSESSMENT: attacks against the network since connections to the original server would need to be diverted towards the malicious server. ______________________________________________________________________________ LINKS: CIAC BULLETIN: http://www.ciac.org/ciac/bulletins/p-257.shtml ORIGINAL BULLETIN: http://www.ssh.com/company/newsroom/article/653/ ADDITIONAL LINK: UC-CERT Vulnerability Note VU#973635 http://www.kb.cert.org/vuls/id/973635 CVE/CAN: http://www.cve.mitre.org/cgi-bin/cvename.cgi?name= CAN-2005-2146 ______________________________________________________________________________ [***** Start SSH Vendor Reference Number: RQ#11775 *****] SSH Tectia Server Private Key Permission Vulnerability in Windows SSH Communications Security >> http://www.ssh.com ====================================================== [SSH Tectia Server Private Key Permission Vulnerability in Windows] < June 30, 2005 > ====================================================== Vendor reference number: RQ #11775 DESCRIPTION When SSH Tectia Server in Windows generates a host identification key (the Secure Shell host key), it sets insufficient file permissions. As a result, any user who has been successfully authenticated to the server and can access the local file system, can also access the Windows server's host identification key (the Secure Shell host key) without having administrative privileges. Furthermore, it is possible that this user makes a copy of the server's host identification key and installs it in a server that can now pretend to be the original server. If the authentication on such server relies solely on passwords, it can potentially be used to collect passwords. This exploit would require also other active attacks against the network since connections to the original server would need to be diverted towards the malicious server. We are not aware of any existing exploits of this specific vulnerability. AFFECTED PRODUCTS * SSH Secure Shell for Windows Servers (all versions) * SSH Tectia Server (Windows) 4.3.1 and older versions Other than Windows versions are NOT affected. FIX / WORK-AROUND SSH Tectia Server 4.3.2 fixes the vulnerability by changing the private key permissions so that the file is only readable by the owner and system accounts. The permissions of existing private keys are changed during the software update and when new private keys are generated, they have the proper permissions set. Alternatively, the host key file can be made readable only for the Administrator group. The default location of the secret part of the host key is C:\Program Files\SSH Communications Security\SSH Secure Shell Server\hostkey The default location of the file may have been modified in the server configuration. In both cases, whether the SSH Tectia Server software is updated or permissions are manually updated, we strongly recommend updating all old Windows server keys. The SSH Tectia Server 4.3.2 update does not automatically update the keys. Note that once the server key has been updated, a warning message will appear in clients connecting to the server and manual key hash verification is required. UPDATING SSH TECTIA SERVER If you have a valid SSH Tectia Server 4.3.x license file, you can get the update package for this product from http://www.ssh.com/support/downloads/tectia-server/updates-and-packages-4-3.html SSH Communications Security apologizes for any inconvenience that this vulnerability may have caused. We take security of the systems of our customers very seriously and do our utmost to provide secure software with minimum defects. We strongly urge all customers to consider the implications of this vulnerability carefully and to make an educated decision on whether or not to update. [***** End SSH Vendor Reference Number: RQ#11775 *****] _______________________________________________________________________________ CIAC wishes to acknowledge the contributions of SSH for the information contained in this bulletin. _______________________________________________________________________________ CIAC, the Computer Incident Advisory Capability, is the computer security incident response team for the U.S. Department of Energy (DOE) and the emergency backup response team for the National Institutes of Health (NIH). CIAC is located at the Lawrence Livermore National Laboratory in Livermore, California. CIAC is also a founding member of FIRST, the Forum of Incident Response and Security Teams, a global organization established to foster cooperation and coordination among computer security teams worldwide. CIAC services are available to DOE, DOE contractors, and the NIH. CIAC can be contacted at: Voice: +1 925-422-8193 (7x24) FAX: +1 925-423-8002 STU-III: +1 925-423-2604 E-mail: ciac@ciac.org Previous CIAC notices, anti-virus software, and other information are available from the CIAC Computer Security Archive. World Wide Web: http://www.ciac.org/ Anonymous FTP: ftp.ciac.org PLEASE NOTE: Many users outside of the DOE, ESnet, and NIH computing communities receive CIAC bulletins. If you are not part of these communities, please contact your agency's response team to report incidents. Your agency's team will coordinate with CIAC. The Forum of Incident Response and Security Teams (FIRST) is a world-wide organization. A list of FIRST member organizations and their constituencies can be obtained via WWW at http://www.first.org/. This document was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor the University of California nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial products, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation or favoring by the United States Government or the University of California. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or the University of California, and shall not be used for advertising or product endorsement purposes. 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