Table Of Contents
Release Notes for the PIX Firewall Version 4.4(5)
PIX Firewall Manager Interoperability
Cisco Security Policy Manager Interoperability
fixup protocol ftp Command Option
ip verify reverse-path Command
Obtaining Technical Assistance
Release Notes for the PIX Firewall Version 4.4(5)
June 2000
Contents
This document includes the following sections:
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Obtaining Technical Assistance
Introduction
This document describes only the changes for version 4.4(5) of the PIX Firewall software.
For information on previous version 4.4 features, installation notes, limitations and restrictions, usage notes, and caveats, refer to the release notes at these following sites:
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System Requirements
The information contained in these release notes applies to all PIX Firewall hardware models running software version 4.4 or later.
Version 4.4 supports one of the following interface combinations:
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Memory Requirements
Version 4.4 requires at least 16 MB of RAM (optional memory upgrades are available) and at least
2 MB of Flash memory. Use the show version command to verify how much Flash and RAM memory is in your PIX Firewall.Maximum Configuration Size
The maximum configuration size is 350 KB for all Flash memory sizes.
PIX Firewall Manager Interoperability
You can use PIX Firewall version 4.4(5) with the PIX Firewall Manager version 4.3(2)e. Refer to the Release Notes for the PIX Firewall Manager Version 4.3(2)e for more information. You can view this document online at the following site:
http://www.cisco.com/univercd/cc/td/doc/product/iaabu/pix/pix_v44/pfm432e.htm
The PIX Firewall Manager (PFM) lets you manage PIX Firewall units; however, it does not let you configure any PIX Firewall features added after version 4.3(2).
The "Frequently Asked Questions" section in the PFM release notes provides useful troubleshooting information.
Cisco Security Policy Manager Interoperability
Cisco Security Policy Manager (CSPM), version 2.1, provides policy-based management support for PIX Firewall units running version 4.2(n), 4.4(n), and 5.1(n) software images.
Refer to the documentation set for CSPM at the following site:
http://www.cisco.com/univercd/cc/td/doc/product/ismg/policy/index.htm
New and Changed Information
Version 4.4(5) contains bug fixes and command changes described in the following sections.
fixup protocol ftp Command Option
The new fixup protocol ftp strict command option was added. The command syntax is as follows:
fixup protocol ftp [strict] [port]
The strict option indicates that this command prevents web browsers from sending embedded commands in FTP requests. Each FTP command must be acknowledged before a new command is allowed. Connections sending embedded commands are dropped. The strict option only lets an FTP server generate the 227 command and only lets an FTP client generate the PORT command. The 227 and PORT commands are checked to ensure they do not appear in an error string. In addition, the FTP port can now only be in the range of 1 to 1024.
The port parameter lets you specify the port at which the PIX Firewall listens for FTP traffic. Typically, this value is 21. [CSCdp86352]
ip verify reverse-path Command
The new ip verify reverse-path command implements unicast RPF IP spoofing protection. (Configuration mode.) [CSCdp70632] The command syntax is as follows:
ip verify reverse-path interface int_name
no ip verify reverse-path interface int_name
show ip verify [reverse-path [interface int_name]]
clear ip verify [reverse-path [interface int_name]]
Syntax Description
Usage Guidelines
The ip verify reverse-path command lets you specify which interfaces to protect from an IP spoofing attack using network ingress and egress filtering, which is described in RFC 2267. This command is disabled by default and provides unicast RPF (Reverse Path Forwarding) functionality for the PIX Firewall. The show ip verify command lists the ip verify commands in the configuration. The clear ip verify command removes ip verify commands from the configuration. Unicast RPF is a unidirectional input function that screens inbound packets arriving on an interface. Outbound packets are not screened.
Due to the danger of IP spoofing in the IP protocol, measures need to be taken to reduce this risk when possible. Unicast RPF (Reverse Path Forwarding), or reverse route lookups, prevents such manipulation under certain circumstances.
The ip verify reverse-path command provides both ingress and egress filtering. Ingress filtering checks inbound packets for IP source address integrity, and is limited to addresses for networks in the enforcing entity's local routing table. If the incoming packet does not have a source address represented by a route, then it is impossible to know whether the packet has arrived on the best possible path back to its origin. This is often the case when routing entities cannot maintain routes for every network.
Egress filtering verifies that packets destined for hosts outside the managed domain have IP source addresses verifiable by routes in the enforcing entity's local routing table. If an exiting packet does not arrive on the best return path back to the originator, then the packet is dropped and the activity is logged. Egress filtering prevents internal users from launching attacks using IP source addresses outside of the local domain because most attacks use IP spoofing to hide the identity of the attacking host. Egress filtering makes the task of tracing the origin of an attack much easier. When employed, egress filtering enforces what IP source addresses are obtained from a valid pool of network addresses. Addresses are kept local to the enforcing entity and are therefore easily traceable.
Unicast RPF is implemented as follows:
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Note
Use the show interface command to view the number dropped packets, which appears in the "unicast rpf drops" counter.
Examples
The following example protects traffic between the inside and outside interfaces and provides route command statements for two networks 10.1.2.0 and 10.1.3.0 that connect to the inside interface via a hub:
ip address inside 10.1.1.1 255.255.255.0route inside 10.1.2.0 255.255.255.0 10.1.1.1 1route inside 10.1.3.0 255.255.255.0 10.1.1.1 1ip verify reverse-path interface outsideip verify reverse-path interface insideThe ip verify reverse-path interface outside command statement protects the outside interface from network ingress attacks from the Internet, whereas the ip verify reverse-path interface inside command statement protects the inside interface from network egress attacks from users on the internal network.
Installation Notes
No new installation notes were added in version 4.4(5).
Limitations and Restrictions
No new limitations and restrictions were added in version 4.4(5).
Important Notes
This section lists all important notes that apply to this version.
FTP Change
PIX Firewall now restricts FTP commands so that only FTP servers can submit a 227 reply and only FTP clients can submit a PORT command. Furthermore, the only PORT command permitted can only be one port number lower than the FTP control channel. This change removes the wildcard port for connection created from the PORT command. PIX Firewall now also enforces that the first SYN packet from the dynamic back channel must be from the expected side. [CSCdp86352]
Inconsistent Syslog Message
Syslog message PIX-6-302002 listed the wrong number of bytes transferred during the last TCP connection. If a client tried to connect to an FTP server outside the PIX Firewall unit and FTP was not active, the server occasionally sent an RST (reset). The reset ended the connection, which created incorrect TCP header lengths. If the TCP header length was larger than the packet length, the result produced a negative number of bytes transferred that syslog displayed as an extremely large number.
Error checking has been updated to prevent the inconsistent syslog message and syslog message PIX-5-500003 was added to indicate when a bad TCP header length occurs. [CSCdp74486]
DNS Root Name Server Access
A DNS server on a higher level security interface needing to get updates from a root name server on the outside interface cannot use PAT (Port Address Translation). Instead, a static command statement must be added to map the DNS server to a global address on the outside interface.
For example, PAT is enabled with these commands:
nat (inside) 1 192.168.1.0 255.255.255.0global (inside) 1 209.165.202.128 netmask 255.255.255.224However, a DNS server on the inside at IP address 192.168.1.5 cannot correctly reach the root name server on the outside at IP address 209.165.202.130.
To ensure that the inside DNS server can access the root name server, insert the following static command statement:
static (inside,outside) 209.165.202.129 192.168.1.5The global address 209.165.202.129 provides a translated address for the inside server at IP address 192.168.1.5. [CSCdp48115]
Failover
The failover timeout command does not work in this release. [CSCdm64497]
static Command
Command statements for the static command cannot contain overlapping IP addresses. When IP addresses are overlapped, PIX Firewall experiences service denials without sending denial statements to syslog. [CSCdp22217] In this caveat report, an FTP session was attempted but was denied without a denial message sent to syslog.
For example, the following command statements do not work:
nat (inside) 0 10.0.0.0 255.0.0.0static (inside,outside) 10.0.0.0 10.0.0.0 netmask 255.0.0.0static (inside,perim1) 10.64.0.0 10.64.0.0 netmask 255.255.0.0In this example, the nat 0 command statement enables the identity feature so that any host on the 10.0.0.0 network can start connections to a lower security level interface. The first static command statement lets all hosts on the inside 10.0.0.0 network be visible on the outside network. The second static statement attempts to use a subset of the 10.0.0.0 address range on another interface. Because 10.64.0.0 is a part of the 10.0.0.0 range of addresses, the addresses overlap.
Caveats
The sections that follow list open and resolved caveats in this release.
Open Caveats
The following open caveats were reported in version 4.4:
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A DNS server behind the PIX Firewall cannot use PAT; however, adding a static command statement can be used as a workaround.
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Command statements for the static command cannot contain IP addresses that overlap between statements.
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The failover timeout command does not work in this release.
Resolved Caveats
The following caveats were fixed in version 4.4(5):
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A failover Standby unit no longer sends Websense requests to the Websense server.
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The TACACS+ per-user idle and absolute timeouts now work correctly.
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PIX Firewall no longer fails when detecting a bad SQL*Net packet.
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If the new fixup protocol ftp strict command is entered, PIX Firewall now prevents FTP clients from initiating FTP server commands. Refer to "fixup protocol ftp Command Option" for more information.
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A command line error appears if you enter the aaa command with abbreviated matching letters of aaa-server command statements. For example, using the letter "t" when there is more than one server that starts with the letter "t." The server name must be defined enough to differentiate between names.
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Syslog has been updated to correct the missing message PIX-6-302002.
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If a bad TCP header length was detected, syslog message PIX-6-302002 reported an incorrect number of bytes transferred. The PIX-5-500003 syslog message has been added to indicate when a bad TCP header length occurs.
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Address spoofing is no longer possible using perimeter interface address ranges when the new ip verify reverse-path command is used. Refer to "ip verify reverse-path Command" for more information.
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Logging now occurs for a URL when performing JAVA filtering.
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When retransmitting an access request that has timed out, use the previously generated authenticator. Creating a new authenticator may cause the access reply to be ignored.
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The terminal no monitor command now works correctly.
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TCP flags are now printed for all SYS_DENY_TCP_OUT syslog messages.
Related Documentation
Use this document in conjunction with the version 4.4 PIX Firewall documentation set. You can view these documents at the following site:
http://www.cisco.com/univercd/cc/td/doc/product/iaabu/pix/pix_v44/index.htm
Obtaining Documentation
World Wide Web
You can access the most current Cisco documentation on the World Wide Web at http://www.cisco.com, http://www-china.cisco.com, or http://www-europe.cisco.com.
Documentation CD-ROM
Cisco documentation and additional literature are available in a CD-ROM package, which ships with your product. The Documentation CD-ROM is updated monthly. Therefore, it is probably more current than printed documentation. The CD-ROM package is available as a single unit or as an annual subscription.
Ordering Documentation
Registered CCO users can order the Documentation CD-ROM and other Cisco Product documentation through our online Subscription Services at http://www.cisco.com/pcgi-bin/subcat/kaojump.cgi.
Nonregistered CCO users can order documentation through a local account representative by calling Cisco's corporate headquarters (California, USA) at 408 526-4000 or, in North America, call 800 553-NETS (6387).
Obtaining Technical Assistance
Cisco provides Cisco Connection Online (CCO) as a starting point for all technical assistance. Warranty or maintenance contract customers can use the Technical Assistance Center. All customers can submit technical feedback on Cisco documentation using the web, e-mail, a self-addressed stamped response card included in many printed docs, or by sending mail to Cisco.
Cisco Connection Online
Cisco continues to revolutionize how business is done on the Internet. Cisco Connection Online is the foundation of a suite of interactive, networked services that provides immediate, open access to Cisco information and resources at anytime, from anywhere in the world. This highly integrated Internet application is a powerful, easy-to-use tool for doing business with Cisco.
CCO's broad range of features and services helps customers and partners to streamline business processes and improve productivity. Through CCO, you will find information about Cisco and our networking solutions, services, and programs. In addition, you can resolve technical issues with online support services, download and test software packages, and order Cisco learning materials and merchandise. Valuable online skill assessment, training, and certification programs are also available.
Customers and partners can self-register on CCO to obtain additional personalized information and services. Registered users may order products, check on the status of an order and view benefits specific to their relationships with Cisco.
You can access CCO in the following ways:
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You can e-mail questions about using CCO to cco-team@cisco.com.
Technical Assistance Center
The Cisco Technical Assistance Center (TAC) is available to warranty or maintenance contract customers who need technical assistance with a Cisco product that is under warranty or covered by a maintenance contract.
To display the TAC web site that includes links to technical support information and software upgrades and for requesting TAC support, use www.cisco.com/techsupport.
To contact by e-mail, use one of the following:
In North America, TAC can be reached at 800 553-2447 or 408 526-7209. For other telephone numbers and TAC e-mail addresses worldwide, consult the following web site: http://www.cisco.com/warp/public/687/Directory/DirTAC.shtml.
Documentation Feedback
If you are reading Cisco product documentation on the World Wide Web, you can submit technical comments electronically. Click Feedback in the toolbar and select Documentation. After you complete the form, click Submit to send it to Cisco.
You can e-mail your comments to bug-doc@cisco.com.
To submit your comments by mail, for your convenience many documents contain a response card behind the front cover. Otherwise, you can mail your comments to the following address:
Cisco Systems, Inc.
Document Resource Connection
170 West Tasman Drive
San Jose, CA 95134-9883We appreciate and value your comments.
This document is to be used in conjunction with the documents listed in the "Related Documentation" section.
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