HP-UX IPFilter A.03.05.13 Administrator's Guide: HP-UX 11i v3
Table Of Contents
- HP-UX IPFilter Version A.03.05.13 Administrator's Guide
- Legal Notices
- Table of Contents
- Preface: About This Document
- 1 Installing and Configuring HP-UX IPFilter
- Overview of HP-UX IPFilter Installation
- Step 1: Checking HP-UX IPFilter Installation Prerequisites
- Step 2: Loading HP-UX IPFilter Software
- Step 3: Determining the Rules for IPFilter
- Step 4: Adding Rules to the Rules Files
- Step 5: Loading IPFilter and NAT Rules
- Step 6: Verifying the Installation and Configuration
- Kernel Tunable Parameters
- Supported and Unsupported Interfaces
- Troubleshooting HP-UX IPFilter
- 2 HP-UX IPFilter on HP-UX 11i Version 3
- 3 Rules and Keywords
- IPFilter Configuration Files
- Basic Rules Processing
- IPFilter Keywords
- pass and block: Controlling IP Traffic
- in and out: Bidirectional Filtering
- quick: Optimizing IPFilter Rules Processing
- on: Filtering by Network Interfaces
- from and to: Filtering by IP Addresses and Subnets
- log: Tracking Packets on a System
- proto: Controlling Specific Protocols
- opt and ipopts: Filtering on IP Options
- icmp-type: Filtering ICMP Traffic by Type
- port: Filtering on TCP and UDP Ports
- keep state: Protecting TCP, UDP, and ICMP Sessions
- flags: Tight Filtering Based on TCP Header Flags
- keep frags: Letting Fragmented Packets Pass
- with frags: Dropping Fragmented Packets
- with short: Dropping Short Fragments
- return-rst: Responding to Blocked TCP Packets
- return-icmp: Responding to Blocked ICMP Packets
- dup-to: Drop-Safe Logging
- NAT Keywords
- 4 Dynamic Connection Allocation
- 5 Firewall Building Concepts
- Blocking Services by Port Number
- Using Keep State
- Using Keep State with UDP
- Using Keep State with ICMP
- Logging Techniques
- Improving Performance with Rule Groups
- Localhost Filtering
- Using the to
- Creating a Complete Filter by Interface
- Combining IP Address and Network Interface Filtering
- Using Bidirectional Filtering Capabilities
- Using port and proto to Create a Secure Filter
- 6 HP-UX IPFilter Utilities
- 7 HP-UX IPFilter and FTP
- 8 HP-UX IPFilter and RPC
- 9 HP-UX IPFilter and IPSec
- 10 HP-UX IPFilter and Serviceguard
- A HP-UX IPFilter Configuration Examples
- B HP-UX IPFilter Static Linking
- C Performance Guidelines
- Index
Rules and Keywords
IPFilter Keywords
Chapter 340
proto: Controlling Specific Protocols
IPFilter can filter traffic based on protocol, such as TCP or ICMP, using
the proto keyword.
For example, many Denial of Service (DoS) attacks rely on glitches in the
TCP/IP stack of the OS, in the form of ICMP packets. To block ICMP
packets, add the proto command to your ruleset as follows:
block in log quick on lan0 proto icmp from any to any
In this example, any ICMP traffic coming in from lan0 will be logged and
discarded.
IPFilter also has a shorthand for rules that apply to proto tcp and
proto udp at the same time, such as portmap or NFS. The rule for
portmap would be:
block in log quick on lan0 proto tcp/udp from any to
20.20.20.0/24 port = 111
opt and ipopts: Filtering on IP Options
IPFilter can filter packets based on IP options using the opt and ipopts
keywords. You can configure IPFilter rules to pass or block packets that
have a specific option set. For example:
block in quick all with opt lsrr, ssrr
NOTE If you configure IPFilter to filter on more than one option with the opt
keyword, use a comma and a space to delimit each option. See the
previous example for correct syntax.
You can also configure rules to pass or block packets that do not have a
specific option set. For example:
pass in from any to any with opt ssrr not opt lsrr
If you want to block or pass a packet that has any IP option set or no IP
options set, use the ipopts keyword. For example:
block in all with ipopts
For a complete list of IP options, see the IETF RFC at
http://www.faqs.org/rfcs/std/std2.html.