HTTP Inspection Engine
The HTTP Inspection Engine feature allows users to configure their Cisco IOS Firewall to detect and prohibit HTTP connections--such as tunneling over port 80, unauthorized request methods, and non-HTTP compliant file transfers--that are not authorized within the scope of the security policy configuration. Tunneling unauthorized protocols through port 80 and over HTTP exposes a network to significant security risks.
The Cisco IOS Firewall can now be configured with a security policy that adheres to the following tasks:
- Allowing specific traffic targeted for port 80 to traverse the firewall. The traffic is inspected for protocol conformance and for the types of HTTP commands that are allowed or disallowed.
- Denying specific traffic targeted for port 80 that does not comply to HTTP traffic standards. The firewall is enabled to drop the packet, reset the connection, and send a syslog message, as appropriate.
Feature History for HTTP Inspection Engine
| Release |
Modification |
|---|---|
| 12.3(14)T |
This feature was introduced. |
Finding Feature Information
Your software release may not support all the features documented in this module. For the latest feature information and caveats, see the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the Feature Information Table at the end of this document.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.
Restrictions for HTTP Inspection Engine
The Cisco 831 router with 48M RAM does not have enough memory to support this feature.
Information About HTTP Inspection Engine
Before configuring an application firewall to detect and police specific traffic targeted for port 80, you should understand the following concepts:
What Is a Security Policy
The application firewall uses a security policy, which consists of a collection of static signatures, to detect security violations. A static signature is a collection of parameters that specify protocol conditions that must be met before an action is taken. (For example, a signature may specify that an HTTP data stream containing the POST method must reset the connection.) These protocol conditions and reactions are defined by the end user via the command-line interface (CLI) to form a security policy.
Cisco IOS HTTP Application Policy Overview
HTTP uses port 80 to transport Internet web services, which are commonly used on the network and rarely challenged with regards to their legitimacy and conformance to standards. Because port 80 traffic is typically allowed through the network without being challenged, many application developers are leveraging HTTP traffic as an alternative transport protocol in which to enable their application to travel through or even bypass the firewall.
Most firewalls provide only packet filtering capabilities that simply permit or deny port 80 traffic without inspecting the data stream; the Cisco IOS application firewall for HTTP performs packet inspection as follows:
- Detects HTTP connections that are not authorized within the scope of the security policy configuration.
- Detects users who are tunneling applications through port 80.
If the packet is not in compliance with the HTTP protocol, it will be dropped, the connection will be reset, and a syslog message will be generated, as appropriate.
How to Define and Apply an HTTP Application Policy to a Firewall for Inspection
- Defining an HTTP Application Policy
- Applying an HTTP Application Policy to a Firewall for Inspection
Defining an HTTP Application Policy
Use this task to create an HTTP application firewall policy.
 Note |
Although application firewall policies are defined in global configuration mode, only one global policy for a given protocol is allowed per interface. > |
DETAILED STEPS
What to Do Next
After you have successfully defined an application policy for HTTP traffic inspection, you must apply the policy to an inspection rule. Thereafter, the inspection rule must be applied to an interface. For information on completing this task, see the section "Applying an HTTP Application Policy to a Firewall for Inspection."
Applying an HTTP Application Policy to a Firewall for Inspection
Use this task to apply an HTTP application policy to an inspection rule, followed by applying the inspection rule to an interface.
Note |
An application policy can coexist with other inspection protocols (for example, an HTTP policy and an FTP policy can coexist). |
You must have already defined an application policy (as shown in the section "Defining an HTTP Application Policy").
or
show ip inspect name inspection-name | config | interfaces | session [detail] | statistics | all}
DETAILED STEPS
| Command or Action | Purpose | |
|---|---|---|
|
|
Example: Router> enable |
Enables privileged EXEC mode.
|
|
|
Example: Router# configure terminal |
Enters global configuration mode. |
|
|
Example: Router(config)# ip inspect name firewall appfw mypolicy |
Defines a set of inspection rules for the application policy.
|
|
|
Example: Router(config)# ip inspect name firewall http |
Defines a set of inspection rules that is to be applied to all HTTP traffic.
|
|
|
Example: Router#(config)# interface FastEthernet0/0 |
Configures an interface type and enters interface configuration mode. |
|
|
Example: Router#(config-if)# ip inspect firewall in |
Applies the inspection rules (defined in Step 3 and Step 4) to all traffic entering the specified interface.
|
|
|
Example: Router#(config-if)# exit |
Exits interface configuration mode. |
|
|
Example: Router(config)# exit |
Exits global configuration mode. |
|
|
Example: Router# show appfw configuration Example:
Example: or Example: show ip inspect {name inspection-name | config | interfaces | session [detail] | statistics | all} Example: Router# show ip inspect config |
(Optional) Displays application firewall policy configuration information. (Optional) Displays firewall-related configuration information. |
Troubleshooting Tips
To help troubleshoot the application firewall configuration, issue the following application-firewall specific debug command: debug appfw application protocol | function-trace | object-creation | object-deletion | events | timers | detailed} .
The following sample configuration shows how to configure an HTTP policy with application firewall debugging enabled:
Router(config)# appfw policy-name myPolicyAPPFW FUNC:appfw_policy_find APPFW FUNC:appfw_policy_find -- Policy myPolicy is not found APPFW FUNC:appfw_policy_alloc APPFW FUNC:appfw_policy_alloc -- policy_alloc 0x65727278 APPFW FUNC:appfw_policy_alloc -- Policy 0x65727278 is set to valid APPFW FUNC:appfw_policy_alloc -- Policy myPolicy has been created APPFW FUNC:appfw_policy_command -- memlock policy 0x65727278 ! Debugging sample for application (HTTP) creation Router(cfg-appfw-policy)# application httpAPPFW FUNC:appfw_http_command APPFW FUNC:appfw_http_appl_find APPFW FUNC:appfw_http_appl_find -- Application not found APPFW FUNC:appfw_http_appl_alloc APPFW FUNC:appfw_http_appl_alloc -- appl_http 0x64D7A25C APPFW FUNC:appfw_http_appl_alloc -- Application HTTP parser structure 64D7A25C created ! Debugging sample for HTTP-specific application inspection Router(cfg-appfw-policy-http)# Router(cfg-appfw-policy-http)# strict-http action reset alarm APPFW FUNC:appfw_http_subcommand APPFW FUNC:appfw_http_subcommand -- strict-http cmd turned on Router# debug appfw detailed APPFW Detailed Debug debugging is on fw7-7206a#debug appfw object-creation APPFW Object Creations debugging is on fw7-7206a#debug appfw object-deletion APPFW Object Deletions debugging is on
Configuration Examples for Setting Up an HTTP Inspection Engine
Setting Up and Verifying an HTTP Inspection Engine Example
The following example show how to define the HTTP application firewall policy "mypolicy." This policy includes all supported HTTP policy rules. This example also includes sample output from the show appfw configuration and show ip inspect config commands, which allow you to verify the configured setting for the application policy.
! Define the HTTP policy. appfw policy-name mypolicy application http strict-http action allow alarm content-length maximum 1 action allow alarm content-type-verification match-req-rsp action allow alarm max-header-length request 1 response 1 action allow alarm max-uri-length 1 action allow alarm port-misuse default action allow alarm request-method rfc put action allow alarm transfer-encoding type default action allow alarm ! ! ! Apply the policy to an inspection rule. ip inspect name firewall appfw mypolicy ip inspect name firewall http ! ! ! Apply the inspection rule to all HTTP traffic entering the FastEthernet0/0 interface. interface FastEthernet0/0 ip inspect firewall in ! ! ! Issue the show appfw configuration command and the show ip inspect config command after the inspection rule "mypolicy" is applied to all incoming HTTP traffic on the FastEthernet0/0 interface. ! Router# show appfw configuration Application Firewall Rule configuration Application Policy name mypolicy Application http strict-http action allow alarm content-length minimum 0 maximum 1 action allow alarm content-type-verification match-req-rsp action allow alarm max-header-length request length 1 response length 1 action allow alarm max-uri-length 1 action allow alarm port-misuse default action allow alarm request-method rfc put action allow alarm transfer-encoding default action allow alarm Router# show ip inspect config Session audit trail is disabled Session alert is enabled one-minute (sampling period) thresholds are [400:500] connections max-incomplete sessions thresholds are [400:500] max-incomplete tcp connections per host is 50. Block-time 0 minute. tcp synwait-time is 30 sec -- tcp finwait-time is 5 sec tcp idle-time is 3600 sec -- udp idle-time is 30 sec dns-timeout is 5 sec Inspection Rule Configuration Inspection name firewall http alert is on audit-trail is off timeout 3600
Additional References
The following sections provide references related to the HTTP Inspection Engine feature.
Related Documents
| Related Topic |
Document Title |
|---|---|
| Firewall commands: complete command syntax, command mode, defaults, usage guidelines, and examples |
Cisco IOS Security Command Reference |
Standards
| Standards |
Title |
|---|---|
| No new or modified standards are supported by this feature. |
-- |
MIBs
| MIBs |
MIBs Link |
|---|---|
| No new or modified MIBs are supported by this feature. |
To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL: |
RFCs
| RFCs |
Title |
|---|---|
| RFC 2616 |
Technical Assistance
| Description |
Link |
|---|---|
| The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password. |
Cisco and the Cisco Logo are trademarks of Cisco Systems, Inc. and/or its affiliates in the U.S. and other countries. A listing of Cisco's trademarks can be found at www.cisco.com/go/trademarks. Third party trademarks mentioned are the property of their respective owners. The use of the word partner does not imply a partnership relationship between Cisco and any other company. (1005R)
Any Internet Protocol (IP) addresses and phone numbers used in this document are not intended to be actual addresses and phone numbers. Any examples, command display output, network topology diagrams, and other figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses or phone numbers in illustrative content is unintentional and coincidental.
© 2011 Cisco Systems, Inc. All rights reserved.
Feedback