On 02/20/2002, Martin O'Neal of Corsaire Ltd. posted: -- Corsaire Limited Security Advisory -- Title: Symantec Enterprise Firewall (SEF) SMTP proxy inconsistencies Date: 18.01.02 Application: Symantec Enterprise Firewall (SEF) 6.5.x Environment: WinNT, Win2000 Author: Martin O'Neal [martin.oneal@corsaire.com] Audience: General distribution -- Scope -- The aim of this document is to clearly define some issues related to a some SMTP proxy inconsistencies within the Symantec Enterprise Firewall (SEF) environment as provided by Symantec [1]. -- History -- Vendor notified: 18.01.02 Document released: 21.02.02 -- Overview -- The SEF firewall product uses an application proxy strategy to provide enhanced security features for a variety of common protocols. For the SMTP proxy, part of this additional functionality allows the firewall to restrict the sender / recipient domains and to hide internal infrastructure information from external recipients. However, when the firewall is configured to provide network address translation (NAT) to an SMTP connection (effectively hiding the internal server behind a publicly routable address), this might not always be conducted as desired. ---------------------------snip- Symantec Security Response Advisory 15 February, 2002 Symantec Enterprise Firewall SMTP Proxy Issues Reference Corsaire Limited Security Advisory 020118-001a.txt Risk Impact Low Affected Components Symantec Enterprise Firewall versions 6.5.x and 7.0 Overview Corsaire Limited has discovered two low-risk issues with Symantec Enterprise Firewall. The first is a potential information leak in the Symantec Enterprise Firewall Simple Mail Transfer Protocol (SMTP) proxy environment that could provide inappropriate information on the firewall configuration. The second is that inconsistencies in the SMTP protocol exchange could cause a connection to be denied. Details Corsaire Limited notified Symantec Corporation of some issues in the way the Symantec Enterprise Firewall SMTP proxy worked with network address translation (NAT). These issues could cause some undesirable results. Symantec Enterprise Firewall uses application proxies to provide enhanced security. Uses of this feature include restricting the sender/recipient domains and hiding internal infrastructure information from external users. Corsaire Limited discovered that when Symantec Enterprise Firewall is configured to provide NAT to an SMTP connection, the function to hide the internal server address by mapping it to an external public address is not performed in a completely desirable manner. The Symantec Enterprise Firewall SMTP proxy should analyze the SMTP format and dynamically change the IP address as well as edit the required IP header. Corsaire Limited's research demonstrated that when the inbound or outbound SMTP connection was translated to an address other than the address assigned to the physical firewall interface, the SMTP proxy continued to use the name and address of the physical interface in the SMTP protocol exchange. There are two low-risk issues with the way Symantec Enterprise Firewall is handling the SMTP proxy interface. First, there is a potential information leak. Information is included in the SMTP protocol exchange that could, possibly, aid a malicious intruder in analyzing the firewall configuration. Second, a receiving/transmitting host that is configured to enforce strict checks on the SMTP protocol exchange may not accept the connection due to inconsistencies in the field. This could result in the nondelivery or bouncing of mail messages. Symantec Response Symantec has verified the issues discovered by Corsaire Limited and developed a fix that will be included with the near-future release of Symantec Enterprise Firewall version 8.0. Until then, use the following workarounds to address these issues: * Configure Symantec Enterprise Firewall to use the same name for the firewall name and the firewall external interface name. This workaround results in consistent names for SMTP replies. * If NAT is not needed, use the SMTP wizard included with Symantec Enterprise Firewall to set up rules and redirects for all inbound and outbound SMTP traffic. Credit Symantec takes the security of its products very seriously. Symantec appreciates the coordination of Martin O'Neal and Corsaire Limited in identifying and providing technical details of potential areas of concern so it can quickly address the issue. Anyone with information on security issues with Symantec products should contact symsecurity@symantec.com. This advisory can be viewed at http://securityresponse.symantec.com/avcenter/security/Content/2002.02.20.html Copyright (c) 2001 by Symantec Corp. Permission to redistribute this Advisory electronically is granted as long as it is not edited in any way unless authorized by Symantec Security Response. Reprinting the whole or part of this Advisory in a medium other than electronically requires permission from Sym Security@symantec.com. Disclaimer The information in the advisory is believed to be accurate at the time of printing based on currently available information. Use of the information constitutes acceptance for use in an AS IS condition. There are no warranties with regard to this information. Neither the author nor the publisher accepts any liability for any direct, indirect or consequential loss or damage arising from use of, or reliance on this information. 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