The Cisco router must be configured to implement replay-resistant authentication mechanisms for network access to privileged accounts.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-216531	CISC-ND-000530	SV-216531r531088_rule		Medium

Description
A replay attack may enable an unauthorized user to gain access to the application. Authentication sessions between the authenticator and the application validating the user credentials must not be vulnerable to a replay attack. An authentication process resists replay attacks if it is impractical to achieve a successful authentication by recording and replaying a previous authentication message. Techniques used to address this include protocols using nonces (e.g., numbers generated for a specific one-time use) or challenges (e.g., TLS, WS_Security). Additional techniques include time-synchronous or challenge-response one-time authenticators.

Description

A replay attack may enable an unauthorized user to gain access to the application. Authentication sessions between the authenticator and the application validating the user credentials must not be vulnerable to a replay attack. An authentication process resists replay attacks if it is impractical to achieve a successful authentication by recording and replaying a previous authentication message. Techniques used to address this include protocols using nonces (e.g., numbers generated for a specific one-time use) or challenges (e.g., TLS, WS_Security). Additional techniques include time-synchronous or challenge-response one-time authenticators.

STIG	Date
Cisco IOS XR Router NDM Security Technical Implementation Guide	2020-09-23

Details

Check Text ( C-17766r288279_chk )
Review the router configuration to verify that SSH version 2 is configured as shown in the example below. ssh server v2 Note: IOS XR supports SSHv1 and SSHv2. SSHv1 uses Rivest, Shamir, and Adelman (RSA) keys while SSHv2 uses Digital Signature Algorithm (DSA) keys. If the router is not configured to implement replay-resistant authentication mechanisms for network access to privileged accounts, this is a finding.

Check Text ( C-17766r288279_chk )

Review the router configuration to verify that SSH version 2 is configured as shown in the example below.

ssh server v2

Note: IOS XR supports SSHv1 and SSHv2. SSHv1 uses Rivest, Shamir, and Adelman (RSA) keys while SSHv2 uses Digital Signature Algorithm (DSA) keys.

If the router is not configured to implement replay-resistant authentication mechanisms for network access to privileged accounts, this is a finding.

Fix Text (F-17763r288280_fix)
Configure the router to use SSH version 2 as shown in the example below. RP/0/0/CPU0:R3(config)#ssh server v2