Advisory ID: cisco-amb-20111026-camera
http://tools.cisco.com/security/center/content/CiscoAppliedMitigationBulletin/cisco-amb-20111026-camera
Revision 1.1
Last Updated on 2012 February 2 17:32 UTC (GMT)
For Public Release 2011 October 26 16:00 UTC (GMT)
Contents
Cisco ResponseDevice-Specific Mitigation and Identification
Additional Information
Revision History
Cisco Security Procedures
Related Information
Cisco Response
This Applied Mitigation Bulletin is a companion document to the PSIRT Security Advisory Denial of Service Vulnerability in Cisco Video Surveillance IP Cameras and provides identification and mitigation techniques that administrators can deploy on Cisco network devices.Vulnerability Characteristics
The Cisco Video Surveillance IP Camera exhibits a vulnerability when processing crafted Real Time Streaming Protocol (RTSP) packets. This vulnerability can be exploited remotely without authentication and without end-user interaction. Successful exploitation of this vulnerability may cause the affected device to reboot. Repeated attempts to exploit this vulnerability could result in a sustained denial of service (DoS) condition. The attack vector for exploitation is through RTSP packets using TCP port 554.
This vulnerability has been assigned Common Vulnerabilities and Exposures (CVE) identifier CVE-2011-3318.Vulnerability Overview
Information about vulnerable, unaffected, and fixed software is available in the PSIRT Security Advisory, which is available at the following link: http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20111026-camera.Mitigation Technique Overview
Cisco devices provide several countermeasures for this vulnerability. Administrators are advised to consider these protection methods to be general security best practices for infrastructure devices and the traffic that transits the network. This section of the document provides an overview of these techniques.
Cisco IOS Software can provide effective means of exploit prevention using transit access control lists (tACLs).
This protection mechanism filters and drops packets that are attempting to exploit this vulnerability.
Effective exploit prevention can also be provided by the Cisco ASA 5500 Series Adaptive Security Appliance and the Firewall Services Module (FWSM) for Cisco Catalyst 6500 using tACLS.
This protection mechanism filters and drops packets that are attempting to exploit this vulnerability.
Cisco IOS NetFlow records can provide visibility into network-based exploitation attempts.
Cisco IOS Software, Cisco ASA, and FWSM firewalls can provide visibility through syslog messages and counter values displayed in the output from show commands.
Risk Management
Organizations are advised to follow their standard risk evaluation and mitigation processes to determine the potential impact of this vulnerability. Triage refers to sorting projects and prioritizing efforts that are most likely to be successful. Cisco has provided documents that can help organizations develop a risk-based triage capability for their information security teams. Risk Triage for Security Vulnerability Announcements and Risk Triage and Prototyping can help organizations develop repeatable security evaluation and response processes.Device-Specific Mitigation and Identification
Caution: The effectiveness of any mitigation technique is dependent on specific customer situations such as product mix, network topology, traffic behavior, and organizational mission. As with any configuration change, evaluate the impact of this configuration prior to applying the change.Specific information about mitigation and identification is available for these devices:
Cisco IOS Routers and Switches
Mitigation: Transit Access Control Lists
To protect the network from traffic that enters the network at ingress access points, which may include Internet connection points, partner and supplier connection points, or VPN connection points, administrators are advised to deploy transit access control lists (tACLs) to perform policy enforcement. Administrators can construct a tACL by explicitly permitting only authorized traffic to enter the network at ingress access points or permitting authorized traffic to transit the network in accordance with existing security policies and configurations. A tACL workaround cannot provide complete protection against this vulnerability when the attack originates from a trusted source address.
The tACL policy denies unauthorized RTSP packets on TCP port 554 that are sent to affected devices. In the following example, 192.168.60.0/24 is the IP address space that is used by the affected devices, and the host at 192.168.100.1 is considered a trusted source that requires access to the affected devices. Care should be taken to allow required traffic for routing and administrative access prior to denying all unauthorized traffic.
Additional information about tACLs is in Transit Access Control Lists: Filtering at Your Edge.
!-- Include explicit permit statements for trusted sources
!-- that require access on the vulnerable TCP port
! access-list 150 permit tcp host 192.168.100.1 192.168.60.0 0.0.0.255 eq 554 !
!-- The following vulnerability-specific access control entry
!-- (ACE) can aid in identification of attacks
! access-list 150 deny tcp any 192.168.60.0 0.0.0.255 eq 554 !
!-- Permit or deny all other Layer 3 and Layer 4 traffic in accordance
!-- with existing security policies and configurations
!
!-- Explicit deny for all other IP traffic
! access-list 150 deny ip any any !
!-- Apply tACL to interfaces in the ingress direction
! interface GigabitEthernet0/0 ip access-group 150 in
Note that filtering with an interface access list will elicit the transmission of ICMP unreachable messages back to the source of the filtered traffic. Generating these messages could have the undesired effect of increasing CPU utilization on the device. In Cisco IOS Software, ICMP unreachable generation is limited to one packet every 500 milliseconds by default. ICMP unreachable message generation can be disabled using the interface configuration command no ip unreachables. ICMP unreachable rate limiting can be changed from the default using the global configuration command ip icmp rate-limit unreachable interval-in-ms.
Identification: Transit Access Control Lists
After the administrator applies the tACL to an interface, the show ip access-lists command will identify the number of RTSP packets on TCP port 554 that have been filtered. Administrators are advised to investigate filtered packets to determine whether they are attempts to exploit this vulnerability. Example output for show ip access-lists 150 follows:
router#show ip access-lists 150 Extended IP access list 150
10 permit tcp host 192.168.100.1 192.168.60.0 0.0.0.255 eq 554
20 deny tcp any 192.168.60.0 0.0.0.255 eq 554 (26 matches)
30 deny ip any any router#
In the preceding example, access list 150 has dropped 26 RTSP packets on TCP port 554 for access control list entry (ACE) line 20.
For additional information about investigating incidents using ACE counters and syslog events, reference the Identifying Incidents Using Firewall and IOS Router Syslog Events Applied Intelligence white paper.
Administrators can use Embedded Event Manager to provide instrumentation when specific conditions are met, such as ACE counter hits. The Applied Intelligence white paper Embedded Event Manager in a Security Context provides additional details about how to use this feature.
Identification: Access List Logging
The log and log-input access control list (ACL) option will cause packets that match specific ACEs to be logged. The log-input option enables logging of the ingress interface in addition to the packet source and destination IP addresses and ports.
Caution: Access control list logging can be very CPU intensive and must be used with extreme caution. Factors that drive the CPU impact of ACL logging are log generation, log transmission, and process switching to forward packets that match log-enabled ACEs.
For Cisco IOS Software, the ip access-list logging interval interval-in-ms command can limit the effects of process switching induced by ACL logging. The logging rate-limit rate-per-second [except loglevel] command limits the impact of log generation and transmission.
The CPU impact from ACL logging can be addressed in hardware on the Cisco Catalyst 6500 Series switches and Cisco 7600 Series routers with Supervisor Engine 720 or Supervisor Engine 32 using optimized ACL logging.
For additional information about the configuration and use of ACL logging, reference the Understanding Access Control List Logging Applied Intelligence white paper.
Cisco IOS NetFlow
Identification: Traffic Flow Identification Using NetFlow Records
Administrators can configure Cisco IOS NetFlow on Cisco IOS routers and switches to aid in the identification of traffic flows that may be attempts to exploit the vulnerability described in this document that has a network attack vector. Administrators are advised to investigate flows to determine whether they are attempts to exploit this vulnerability or whether they are legitimate traffic flows.
router#show ip cache flow
IP packet size distribution (2568 total packets):
1-32 64 96 128 160 192 224 256 288 320 352 384 416 448 480
.331 .668 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000
512 544 576 1024 1536 2048 2560 3072 3584 4096 4608
.000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000
IP Flow Switching Cache, 278544 bytes
99 active, 3997 inactive, 356 added
4937 ager polls, 0 flow alloc failures
Active flows timeout in 30 minutes
Inactive flows timeout in 15 seconds
IP Sub Flow Cache, 34056 bytes
0 active, 1024 inactive, 0 added, 0 added to flow
0 alloc failures, 0 force free
1 chunk, 1 chunk added
last clearing of statistics never
Protocol Total Flows Packets Bytes Packets Active(Sec) Idle(Sec)
-------- Flows /Sec /Flow /Pkt /Sec /Flow /Flow
TCP-WWW 36 0.0 8 40 0.0 0.0 15.5
TCP-other 135 0.0 6 40 0.2 0.0 15.4
UDP-TFTP 19 0.0 3 28 0.0 0.0 15.5
UDP-other 67 0.0 8 28 0.1 0.0 15.5
Total: 257 0.0 7 35 0.4 0.0 15.4
SrcIf SrcIPaddress DstIf DstIPaddress Pr SrcP DstP Pkts
Et0/0 192.168.57.1 Et0/1 192.168.95.0 06 DE34 D540 9
Et0/0 192.168.0.20 Et0/1 192.168.60.22 06 2697 01BB 5
Et0/0 192.168.0.170 Et0/1 192.168.60.225 06 E73A 01BB 1
Et0/0 192.168.0.134 Et0/1 192.168.60.65 06 A691 01BB 5
Et0/0 192.168.191.62 Et0/1 192.168.173.207 11 A944 F0AB 7
Et0/0 192.168.67.236 Et0/1 192.168.60.192 11 1405 0045 6
Et0/0 192.168.4.249 Et0/1 192.168.181.123 06 B171 F167 8
Et0/0 192.168.251.9 Et0/1 192.168.60.153 11 1D7D 0045 2
Et0/0 192.168.151.52 Et0/1 192.168.230.41 06 F502 7A8A 3
Et0/0 192.168.234.183 Et0/1 192.168.69.162 11 4A08 2F6C 6
Et0/0 192.168.0.7 Et0/1 192.168.60.2 06 D4FA 022A 2
Et0/0 192.168.129.193 Et0/1 192.168.15.3 11 DCCE C9F3 9
Et0/0 192.168.190.255 Et0/1 192.168.55.154 11 B022 D068 7
Et0/0 192.168.47.173 Et0/1 192.168.2.123 06 D83B A3E7 20
Et0/0 192.168.0.96 Et0/1 192.168.60.17 06 4205 022A 6
Et0/0 192.168.212.119 Et0/1 192.168.0.67 06 BD92 4DB5 12
Et0/0 192.168.81.85 Et0/1 192.168.229.141 11 D657 FAAD 1
Et0/0 192.168.131.184 Et0/1 192.168.191.159 06 B9FE 30C1 11
Et0/0 192.168.0.189 Et0/1 192.168.60.132 06 6C70 0050 16
Et0/0 192.168.176.16 Et0/1 192.168.145.248 06 C00A 1B7B 9
Et0/0 192.168.62.92 Et0/1 192.168.60.85 11 BCF1 0045 1
Et0/0 192.168.0.215 Et0/1 192.168.60.192 06 DEAB 022A 2
In the preceding example, there are multiple flows for RTSP on TCP port 554 (hex value 022A).
This traffic is sent to addresses within the 192.168.60.0/24 address block, which is used by affected devices. Administrators are advised to compare these flows to baseline utilization for RTSP traffic sent on TCP port 554 and also investigate the flows to determine whether they are sourced from untrusted hosts or networks.
To view only the traffic flows for RTSP packets on TCP port 554 (hex value 022A), the command show ip cache flow | include SrcIf|_06_.*022A will display the related TCP NetFlow records as shown here:
TCP Flows
router#show ip cache flow | include SrcIf|_06_.*022A SrcIf SrcIPaddress DstIf DstIPaddress Pr SrcP DstP Pkts Et0/0 192.168.0.209 Et0/1 192.168.60.24 06 0598 022A 1
Et0/0 192.168.0.253 Et0/1 192.168.60.150 06 D5AC 022A 3
Et0/0 192.168.0.61 Et0/1 192.168.60.123 06 7042 022A 5
Et0/0 192.168.0.90 Et0/1 192.168.60.108 06 72C8 022A 7
Et0/0 192.168.0.84 Et0/1 192.168.60.68 06 ED93 022A 3
Et0/0 192.168.0.239 Et0/1 192.168.60.38 06 5E4F 022A 2
Et0/0 192.168.0.219 Et0/1 192.168.60.44 06 2F83 022A 2
Et0/0 192.168.0.11 Et0/1 192.168.60.90 06 FEDF 022A 4
Et0/0 192.168.0.12 Et0/1 192.168.60.158 06 6892 022A 1
Et0/0 192.168.0.220 Et0/1 192.168.60.124 06 2A3E 022A 4
Cisco ASA and FWSM Firewalls
Mitigation: Transit Access Control Lists
To protect the network from traffic that enters the network at ingress access points, which may include Internet connection points, partner and supplier connection points, or VPN connection points, administrators are advised to deploy tACLs to perform policy enforcement. Administrators can construct a tACL by explicitly permitting only authorized traffic to enter the network at ingress access points or permitting authorized traffic to transit the network in accordance with existing security policies and configurations. A tACL workaround cannot provide complete protection against this vulnerability when the attack originates from a trusted source address.
The tACL policy denies unauthorized RTSP packets on TCP port 554 that are sent to affected devices. In the following example, 192.168.60.0/24 is the IP address space that is used by the affected devices, and the host at 192.168.100.1 is considered a trusted source that requires access to the affected devices. Care should be taken to allow required traffic for routing and administrative access prior to denying all unauthorized traffic.
Additional information about tACLs is in Transit Access Control Lists: Filtering at Your Edge.
!
!-- Include explicit permit statements for trusted sources
!-- that require access on the vulnerable TCP port
! access-list tACL-Policy extended permit tcp host 192.168.100.1 192.168.60.0 255.255.255.0 eq 554 !
!-- The following vulnerability-specific access control entry
!-- (ACE) can aid in identification of attacks
! access-list tACL-Policy extended deny tcp any 192.168.60.0 255.255.255.0 eq 554 !
!-- Permit or deny all other Layer 3 and Layer 4 traffic in accordance
!-- with existing security policies and configurations
!
!-- Explicit deny for all other IP traffic
! access-list tACL-Policy extended deny ip any any !
!-- Apply tACL to interface(s) in the ingress direction
! access-group tACL-Policy in interface outside
Identification: Transit Access Control Lists
After the tACL has been applied to an interface, administrators can use the show access-list command to identify the number of RTSP packets on TCP port 554 that have been filtered. Administrators are advised to investigate filtered packets to determine whether they are attempts to exploit this vulnerability. Example output for show access-list tACL-Policy follows:
firewall#show access-list tACL-Policy
access-list tACL-Policy; 3 elements
access-list tACL-Policy line 1 extended permit tcp host 192.168.100.1
192.168.60.0 255.255.255.0 eq rtsp (hitcnt=34)
access-list tACL-Policy line 2 extended deny tcp any
192.168.60.0 255.255.255.0 eq rtsp (hitcnt=119)
access-list tACL-Policy line 3 extended deny ip any any (hitcnt=8)
firewall#
In the preceding example, access list tACL-Policy has dropped 119 RTSP packets on TCP port 554 (rtsp) received from an untrusted host or network. In addition, syslog message 106023 can provide valuable information, which includes the source and destination IP address, the source and destination port numbers, and the IP protocol for the denied packet.
Identification: Firewall Access List Syslog Messages
Firewall syslog message 106023 will be generated for packets denied by an access control entry (ACE) that does not have the log keyword present. Additional information about this syslog message is in Cisco ASA 5500 Series System Log Message, 8.2 - 106023.
Information about configuring syslog for the Cisco ASA 5500 Series Adaptive Security Appliance is in Monitoring - Configuring Logging. Information about configuring syslog on the FWSM for Cisco Catalyst 6500 Series switches and Cisco 7600 Series routers is in Monitoring the Firewall Services Module.
In the following example, the show logging | grep regex command extracts syslog messages from the logging buffer on the firewall. These messages provide additional information about denied packets that could indicate potential attempts to exploit the vulnerability that is described in this document. It is possible to use different regular expressions with the grep keyword to search for specific data in the logged messages.
Additional information about regular expression syntax is in Creating a Regular Expression.
firewall#show logging | grep 106023 Oct 26 2011 03:31:29: %ASA-4-106023: Deny tcp src outside:192.168.0.8/30496 dst inside:192.168.60.6/554 by access-group "tACL-Policy" Oct 26 2011 03:31:29: %ASA-4-106023: Deny tcp src outside:192.168.1.10/56574 dst inside:192.168.60.7/554 by access-group "tACL-Policy" Oct 26 2011 03:31:29: %ASA-4-106023: Deny tcp src outside:192.168.0.10/5587 dst inside:192.168.60.4/554 by access-group "tACL-Policy" Oct 26 2011 03:31:29: %ASA-4-106023: Deny tcp src outside:192.168.2.7/1024 dst inside:192.168.60.4/554 by access-group "tACL-Policy" Oct 26 2011 03:31:29: %ASA-4-106023: Deny tcp src outside:192.168.7.5/1024 dst inside:192.168.60.2/554 by access-group "tACL-Policy" firewall#
In the preceding example, the messages logged for the tACL tACL-Policy show RTSP packets on TCP port 554 sent to the address block assigned to the affected devices.
Additional information about syslog messages for ASA security appliances is in Cisco ASA 5500 Series System Log Messages, 8.2. Additional information about syslog messages for the FWSM is in Catalyst 6500 Series Switch and Cisco 7600 Series Router Firewall Services Module Logging System Log Messages.
For additional information about investigating incidents using syslog events, reference the Identifying Incidents Using Firewall and IOS Router Syslog Events Applied Intelligence white paper.
Additional Information
THIS DOCUMENT IS PROVIDED ON AN "AS IS" BASIS AND DOES NOT IMPLY ANY KIND OF GUARANTEE OR WARRANTY, INCLUDING THE WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR USE. YOUR USE OF THE INFORMATION ON THE DOCUMENT OR MATERIALS LINKED FROM THE DOCUMENT IS AT YOUR OWN RISK. CISCO RESERVES THE RIGHT TO CHANGE OR UPDATE THIS DOCUMENT AT ANY TIME.Revision History
| Revision 1.1 | 2012-February-2 | Fixed HTML tag to resolve formatting issue. |
| Revision 1.0 | 2011-October-26 | Initial public release. |
Cisco Security Procedures
Complete information on reporting security vulnerabilities in Cisco products, obtaining assistance with security incidents, and registering to receive security information from Cisco, is available on Cisco's worldwide website at http://www.cisco.com/en/US/products/products_security_vulnerability_policy.html. This includes instructions for press inquiries regarding Cisco security notices. All Cisco security advisories are available at http://www.cisco.com/go/psirt.
Related Information
- Cisco Applied Mitigation Bulletins
- Cisco Security Intelligence Operations
- Cisco IOS NetFlow - Home Page on Cisco.com
- Cisco IOS NetFlow White Papers
- NetFlow Performance Analysis
- Cisco Firewall Products - Home Page on Cisco.com
- Common Vulnerabilities and Exposures (CVE)