Appendix: Enhancing System Security According to NIST SP 800-131A

Our switch systems, by default, work with NIST SP 800-131A, as described in the table below.

This appendix describes how to enhance the security of a system in order to comply with the NIST SP 800-131A standard. This standard is a document which defines cryptographically “acceptable” technologies. This document explains how to protect against possible cryptographic vulnerabilities in the system by using secure methods. Because of compatibility issues, this security state is not the default of the system and it should be manually set.

The OS supports signature generation of sha256WithRSAEncryption, sha1WithRSAEncryption self-signed certificates, and importing certificates as text in PEM format.

To configure a default certificate:

1. Create a new sha256 certificate.

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   switch (config) # crypto certificate name <cert name> generate self-signed hash-algorithm sha256
           

   Warning

   For more details and parameters refer to the command “crypto certificate name”.

2. Show crypto certificate detail.

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   switch (config) # show crypto certificate detail
           

   Search for “signature algorithm” in the output.

3. Set this certificate as the default certificate. Run:

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   switch (config) # crypto certificate default-cert name <cert name>
           

To configure default parameters and create a new certificate:

1. Define the default hash algorithm.

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   switch (config) # crypto certificate generation default hash-algorithm sha256
           

2. Generate a new certificate with default values.

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   switch (config) # crypto certificate name <cert name> generate self-signed
           

   Warning

   When no options are selected, the generated certificate uses the default values for each field.

To test strict mode connect to the WebUI using HTTPS and get the certificate. Search for “signature algorithm”.

SNMPv3 supports configuring username, authentication keys and privacy keys. For authentication keys it is possible to use MD5 or SHA. For privacy keys AES or DES are to be used.

To configure strict mode, create a new user with HMAC-SHA1-96 and AES-128. Run:

            

            
switch (config) # snmp-server user <username> v3 auth sha <password1> priv aes-128 <password2>
        

To verify the user in the CLI, run:

            

            
switch (config) # show snmp user
        

By default, the OS supports HTTPS encryption using TLS1.2 only. Working in TLS1.2 mode also bans MD5 ciphers which are not allowed per NIST 800-131a. In strict mode, the switch supports encryption with TLS1.2 only with the following supported ciphers:

• RSA_WITH_AES_128_CBC_SHA256

• RSA_WITH_AES_256_CBC_SHA256

• DHE_RSA_WITH_AES_128_CBC_SHA256

• DHE_RSA_WITH_AES_256_CBC_SHA256

• TLS_RSA_WITH_AES_128_GCM_SHA256

• TLS_RSA_WITH_AES_256_GCM_SHA384

• TLS_DHE_RSA_WITH_AES_128_GCM_SHA256

• TLS_DHE_RSA_WITH_AES_256_GCM_SHA384

To enable all encryption methods, run:

            

            
switch (config) # web https ssl ciphers all
        

To enable only TLS ciphers (enabled by default), run:

            

            
switch (config) # web https ssl ciphers TLS
        

To enable HTTPS strict mode, run:

            

            
switch (config) # web https ssl ciphers TLS1.2
        

To verify which encryption methods are used, run:

            

            
switch (config)# show web
Web User Interface:
 Web interface enabled: yes
 HTTP enabled: yes
 HTTP port: 80
 HTTP redirect to HTTPS: no
 HTTPS enabled: yes
 HTTPS port: 443
 HTTPS ssl-ciphers: TLS1.2
 HTTPS certificate name: default-cert
 Listen enabled: yes
 No Listen Interfaces.
 
 Inactivity timeout: disabled
 Session timeout: 2 hr 30 min
 Session renewal: 30 min
 
Web file transfer proxy:
 Proxy enabled: no
 
Web file transfer certificate authority:
 HTTPS server cert verify: yes
 HTTPS supplemental CA list: default-ca-list
        

On top of enabling HTTPS, to prevent security breaches HTTP must be disabled.

To disable HTTP, run:

            

            
switch (config) # no web http enable
        

Code signing is used to verify that the data in the image is not modified by any third-party. The operating system supports signing the image files with SHA256, RSA2048 using GnuPG.

The SSH server on the switch by default uses secure ciphers only, message authentication code (MAC), key exchange methods, and public key algorithm. When configuring SSH server to strict mode, the aforementioned security methods only use approved algorithms as detailed in the NIST 800-181A specification and the user can connect to the switch via SSH in strict mode only.

To enable strict security mode, run the following:

            

            
switch (config) # ssh server security strict
        

The no form of the command disables strict security mode.

Make sure to configure the SSH server to work with minimum version 2 since 1 is vulnerable to security breaches.

To configure min-version to strict mode, run:

            

            
switch (config) # ssh server min-version 2
        

By default, the switches support LDAP encryption SSL version 3 or TLS1.0 up to TLS1.2. The only banned algorithm is MD5 which is not allowed per NIST 800-131a. In strict mode, the switch supports encryption with TLS1.2 only with the following supported ciphers:

• DHE-DSS-AES128-SHA256

• DHE-RSA-AES128-SHA256

• DHE-DSS-AES128-GCM-SHA256

• DHE-RSA-AES128-GCM-SHA256

• DHE-DSS-AES256-SHA256

• DHE-RSA-AES256-SHA256

• DHE-DSS-AES256-GCM-SHA384

• DHE-RSA-AES256-GCM-SHA384

• ECDH-ECDSA-AES128-SHA256

• ECDH-RSA-AES128-SHA256

• ECDH-ECDSA-AES128-GCM-SHA256

• ECDH-RSA-AES128-GCM-SHA256

• ECDH-ECDSA-AES256-SHA384

• ECDH-RSA-AES256-SHA384

• ECDH-ECDSA-AES256-GCM-SHA384

• ECDH-RSA-AES256-GCM-SHA384

• ECDHE-ECDSA-AES128-SHA256

• ECDHE-RSA-AES128-SHA256

• ECDHE-ECDSA-AES128-GCM-SHA256

• ECDHE-RSA-AES128-GCM-SHA256

• ECDHE-ECDSA-AES256-SHA384

• ECDHE-RSA-AES256-SHA384

• ECDHE-ECDSA-AES256-GCM-SHA384

• ECDHE-RSA-AES256-GCM-SHA384

• AES128-SHA256

• AES128-GCM-SHA256

• AES256-SHA256

• AES256-GCM-SHA384

To enable LDAP strict mode, run the following:

            

            
switch (config) # ldap ssl mode {start-tls | ssl}