The Cisco router must be configured to enforce approved authorizations for controlling the flow of management information within the device based on control policies.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-216523	CISC-ND-000140	SV-216523r539428_rule		Medium

Description
A mechanism to detect and prevent unauthorized communication flow must be configured or provided as part of the system design. If management information flow is not enforced based on approved authorizations, the network device may become compromised. Information flow control regulates where management information is allowed to travel within a network device. The flow of all management information must be monitored and controlled so it does not introduce any unacceptable risk to the network device or data. Application-specific examples of enforcement occur in systems that employ rule sets or establish configuration settings that restrict information system services or message-filtering capability based on message content (e.g., implementing key word searches or using document characteristics). Applications providing information flow control must be able to enforce approved authorizations for controlling the flow of management information within the system in accordance with applicable policy.

Description

A mechanism to detect and prevent unauthorized communication flow must be configured or provided as part of the system design. If management information flow is not enforced based on approved authorizations, the network device may become compromised. Information flow control regulates where management information is allowed to travel within a network device. The flow of all management information must be monitored and controlled so it does not introduce any unacceptable risk to the network device or data. Application-specific examples of enforcement occur in systems that employ rule sets or establish configuration settings that restrict information system services or message-filtering capability based on message content (e.g., implementing key word searches or using document characteristics). Applications providing information flow control must be able to enforce approved authorizations for controlling the flow of management information within the system in accordance with applicable policy.

STIG	Date
Cisco IOS XR Router NDM Security Technical Implementation Guide	2021-03-26

Details

Check Text ( C-17758r569665_chk )
Review the Cisco router configuration to verify that it is compliant with this requirement. Step 1: Verify that the line vty has an ACL inbound applied as shown in the example below. line default access-class ingress MANAGEMENT_NET transport input ssh ! vty-pool default 0 4 Step 2: Verify that the ACL permits only hosts from the management network to access the router. ipv4 access-list MANAGEMENT_NET 10 permit ipv4 10.1.1.0 255.255.255.0 any 20 deny ipv4 any any log-input If the Cisco router is not configured to enforce approved authorizations for controlling the flow of management information within the device based on control policies, this is a finding.

Check Text ( C-17758r569665_chk )

Review the Cisco router configuration to verify that it is compliant with this requirement.

Step 1: Verify that the line vty has an ACL inbound applied as shown in the example below.

line default
access-class ingress MANAGEMENT_NET
transport input ssh
!
vty-pool default 0 4

Step 2: Verify that the ACL permits only hosts from the management network to access the router.

ipv4 access-list MANAGEMENT_NET
10 permit ipv4 10.1.1.0 255.255.255.0 any
20 deny ipv4 any any log-input

If the Cisco router is not configured to enforce approved authorizations for controlling the flow of management information within the device based on control policies, this is a finding.

Fix Text (F-17755r569623_fix)
Configure the Cisco router to restrict management access to specific IP addresses via SSH as shown in the example below. RP/0/0/CPU0:ios(config)#ipv4 access-list MANAGEMENT_NET RP/0/0/CPU0:ios(config-ipv4-acl)#permit ipv4 10.1.1.0 255.255.255.0 any RP/0/0/CPU0:ios(config-ipv4-acl)#deny ipv4 any any log-input RP/0/0/CPU0:ios(config-ipv4-acl)#exit RP/0/0/CPU0:R3(config)#vty default 0 4 RP/0/0/CPU0:R3(config)#line default RP/0/0/CPU0:R3(config-line)#transport input ssh RP/0/0/CPU0:R3(config-line)#access-class MANAGEMENT_NET in RP/0/0/CPU0:R3(config-line)#end

Fix Text (F-17755r569623_fix)

Configure the Cisco router to restrict management access to specific IP addresses via SSH as shown in the example below.

RP/0/0/CPU0:ios(config)#ipv4 access-list MANAGEMENT_NET
RP/0/0/CPU0:ios(config-ipv4-acl)#permit ipv4 10.1.1.0 255.255.255.0 any
RP/0/0/CPU0:ios(config-ipv4-acl)#deny ipv4 any any log-input
RP/0/0/CPU0:ios(config-ipv4-acl)#exit
RP/0/0/CPU0:R3(config)#vty default 0 4
RP/0/0/CPU0:R3(config)#line default
RP/0/0/CPU0:R3(config-line)#transport input ssh
RP/0/0/CPU0:R3(config-line)#access-class MANAGEMENT_NET in
RP/0/0/CPU0:R3(config-line)#end