Cisco 操作系统IOS存在DLSw拒绝服务漏洞

Cisco IOS在处理UDP和IP 91协议报文时存在多个漏洞，这些漏洞不影响TCP报文处理，成功攻击可能导致系统重启或设备内存泄露，造成拒绝服务的情况。

发布日期：2008-03-26

更新日期：2008-04-08

受影响系统：

Cisco IOS 12.4

Cisco IOS 12.3

Cisco IOS 12.2

Cisco IOS 12.1

Cisco IOS 12.0

描述：

BUGTRAQ ID: 28465

CVE(CAN) ID: CVE-2008-1152

Cisco IOS是思科网络设备中所使用的互联网操作系统。

数据-链路交换（DLSw）允许通过IP网络传输IBM系统网络架构（SNA）和网络基本输入/输出系统（NetBIOS）通讯。Cisco的DLSw实现还使用UDP 2067端口和IP 91协 议进行快速顺序传输（FST）。

Cisco IOS在处理UDP和IP 91协议报文时存在多个漏洞，这些漏洞不影响TCP报文处理，成功攻击可能导致系统重启或设备内存泄露，造成拒绝服务的情况。

链接：http://secunia.com/advisories/29507/

http://www.cisco.com/warp/public/707/cisco-sa-20080326-dlsw.shtml

http://www.us-cert.gov/cas/techalerts/TA08-087B.html

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建议：

临时解决方法：

• 如下配置iACL

!--- Permit DLSw (UDP port 2067 and IP protocol 91) packets

!--- from trusted hosts destined to infrastructure addresses.

access-list 150 permit udp TRUSTED_HOSTS MASK INFRASTRUCTURE_ADDRESSES MASK eq 2067
access-list 150 permit 91 TRUSTED_HOSTS MASK INFRASTRUCTURE_ADDRESSES MASK

!--- Deny DLSw (UDP port 2067 and IP protocol 91) packets from
!--- all other sources destined to infrastructure addresses.

access-list 150 deny udp any INFRASTRUCTURE_ADDRESSES MASK eq 2067
access-list 150 deny 91 any INFRASTRUCTURE_ADDRESSES MASK

!--- Permit/deny all other Layer 3 and Layer 4 traffic in accordance
!--- with existing security policies and configurations
!--- Permit all other traffic to transit the device.

access-list 150 permit ip any any
interface serial 2/0
ip access-group 150 in

• 如下配置控制面整形（CoPP）

!--- Deny DLSw traffic from trusted hosts to all IP addresses

!--- configured on all interfaces of the affected device so that
!--- it will be allowed by the CoPP feature

access-list 111 deny udp host 192.168.100.1 any eq 2067
access-list 111 deny 91 host 192.168.100.1 any

!--- Permit all other DLSw traffic sent to all IP addresses
!--- configured on all interfaces of the affected device so that it
!--- will be policed and dropped by the CoPP feature

access-list 111 permit udp any any eq 2067
access-list 111 permit 91 any any

!--- Permit (Police or Drop)/Deny (Allow) all other Layer 3 and Layer 4
!--- traffic in accordance with existing security policies and
!--- configurations for traffic that is authorized to be sent
!--- to infrastructure devices
!--- Create a Class-Map for traffic to be policed by
!--- the CoPP feature

class-map match-all drop-DLSw-class
match access-group 111

!--- Create a Policy-Map that will be applied to the
!--- Control-Plane of the device.

policy-map drop-DLSw-traffic
class drop-DLSw-class
drop

!--- Apply the Policy-Map to the Control-Plane of the
!--- device

control-plane
service-policy input drop-DLSw-traffic

请注意在Cisco IOS 12.2S和12.0S系列中policy-map句法有所不同：

policy-map drop-DLSw-traffic

class drop-DLSw-class
police 32000 1500 1500 conform-action drop exceed-action drop

厂商补丁：

Cisco

Cisco已经为此发布了一个安全公告（cisco-sa-20080326-dlsw）以及相应补丁:

cisco-sa-20080326-dlsw：Multiple DLSw Denial of Service Vulnerabilities in Cisco IOS

链接：http://www.cisco.com/warp/public/707/cisco-sa-20080326-dlsw.shtml