Juniper EX Series Switches Network Device Management Security Technical Implementation Guide

Successful identification and authentication must not automatically give an entity full access to a network device or security domain. The lack of authorization-based access control could result in the immediate compromise and unauthorized access to sensitive information. All DoD systems must be properly configured to incorporate access control methods that do not rely solely on authentication for authorized access. Authorization is the process of determining whether an entity, once authenticated, is permitted to access a specific asset or set of resources. Information systems use access control policies and enforcement mechanisms to implement this requirement. Authorization procedures and controls must be implemented to ensure each authenticated entity also has a validated and current authorization. Some network devices are pre-configured with security groups. Other network devices enable operators to create custom security groups with custom permissions. For example, an ISSM may require read-only access to audit the network device. Operators may create an audit security group, define permissions and access levels for members of the group, and then assign the ISSM’s user persona to the audit security group. This is still considered privileged access, but the ISSM’s security group is more restrictive than the network administrator’s security group. Network devices that rely on AAA brokers for authentication and authorization services may need to identify the available security groups or access levels available on the network devices and convey that information to the AAA operator. Once the AAA broker identifies the user persona on the centralized directory service, the user’s security group memberships can be retrieved. The AAA operator may need to create a mapping that links target security groups from the directory service to the appropriate security groups or access levels on the network device. Once these mappings are configured, authorizations can happen dynamically, based on each user’s directory service group membership.

To prevent unauthorized connection of devices, unauthorized transfer of information, or unauthorized tunneling (i.e., embedding of data types within data types), organizations must disable unused or unnecessary physical and logical ports/protocols on information systems. Network devices are capable of providing a wide variety of functions and services. Some of the functions and services provided by default may not be necessary to support essential organizational operations. Additionally, it is sometimes convenient to provide multiple services from a single component (e.g., email and web services); however, doing so increases risk over limiting the services provided by any one component. To support the requirements and principles of least functionality, the network device must support the organizational requirements providing only essential capabilities and limiting the use of ports, protocols, and/or services to only those required, authorized, and approved. Some network devices have capabilities enabled by default; if these capabilities are not necessary, they must be disabled. If a particular capability is used, then it must be documented and approved.

Passwords need to be protected at all times, and encryption is the standard method for protecting passwords. If passwords are not encrypted, they can be plainly read (i.e., clear text) and easily compromised. Network devices must enforce cryptographic representations of passwords when storing passwords in databases, configuration files, and log files. Passwords must be protected at all times; using a strong one-way hashing encryption algorithm with a salt is the standard method for providing a means to validate a password without having to store the actual password. Performance and time required to access are factors that must be considered, and the one-way hash is the most feasible means of securing the password and providing an acceptable measure of password security. If passwords are stored in clear text, they can be plainly read and easily compromised. In many instances, verifying the user knows a password is performed using a password verifier. In its simplest form, a password verifier is a computational function that is capable of creating a hash of a password and determining if the value provided by the user matches the stored hash.

Unapproved mechanisms that are used for authentication to the cryptographic module are not validated and therefore cannot be relied upon to provide confidentiality or integrity, and DOD data may be compromised. Network devices utilizing encryption are required to use FIPS-compliant mechanisms for authenticating to cryptographic modules. FIPS 140-2 is the current standard for validating that mechanisms used to access cryptographic modules utilize authentication that meets DOD requirements. However, authentication algorithms must configure security processes to use only FIPS-approved and NIST-recommended authentication algorithms. Use only AES Counter (CTR) cipher block chaining modes in compliance with CVE-2008-5161, plugin 70658 based on vendor guidance in KB20853. This prevents certain plaintext attacks in OpenSSH.

Terminating an idle session within a short time period reduces the window of opportunity for unauthorized personnel to take control of a management session enabled on the console or console port that has been left unattended. In addition, quickly terminating an idle session will also free up resources committed by the managed network element. Terminating network connections associated with communications sessions includes, for example, de-allocating associated TCP/IP address/port pairs at the operating system level, or de-allocating networking assignments at the application level if multiple application sessions are using a single, operating system-level network connection. This does not mean that the device terminates all sessions or network access; it only ends the inactive session and releases the resources associated with that session.

This requirement is intended to address the confidentiality and integrity of system information at rest (e.g., network device rule sets) when it is located on a storage device within the network device or as a component of the network device. This protection is required to prevent unauthorized alteration, corruption, or disclosure of information when not stored directly on the network device. Files on the network device or on removable media used by the device must have their permissions set to allow read or write access to those accounts that are specifically authorized to access or change them. Note that different administrative accounts or roles will have varying levels of access. File permissions must be set so that only authorized administrators can read or change their contents. Whenever files are written to removable media and the media removed from the device, the media must be handled appropriately for the classification and sensitivity of the data stored on the device.

Without authenticating devices, unidentified or unknown devices may be introduced, thereby facilitating malicious activity. Bidirectional authentication provides stronger safeguards to validate the identity of other devices for connections that are of greater risk. A local connection is any connection with a device communicating without the use of a network. A network connection is any connection with a device that communicates through a network (e.g., local area or wide area network, internet). A remote connection is any connection with a device communicating through an external network (e.g., the internet). Because of the challenges of applying this requirement on a large scale, organizations are encouraged to only apply the requirement to those limited number (and type) of devices that truly need to support this capability.

Unapproved mechanisms that are used for authentication to the cryptographic module are not verified and therefore cannot be relied upon to provide confidentiality or integrity, and DOD data may be compromised. Nonlocal maintenance and diagnostic activities are those activities conducted by individuals communicating through a network, either an external network (e.g., the internet) or an internal network. Currently, HMAC is the only FIPS-approved algorithm for generating and verifying message/data authentication codes in accordance with FIPS 198-1. Products that are FIPS 140-2 validated will have an HMAC that meets specification; however, the option must be configured for use as the only message authentication code used for authentication to cryptographic modules. Separate requirements for configuring applications and protocols used by each application (e.g., SNMPv3, SSHv2, HTTPS, and other protocols and applications that require server/client authentication) are required to implement this requirement. Where SSH is used, the SSHv2 protocol suite is required because it includes Layer 7 protocols such as SCP and SFTP, which can be used for secure file transfers. Use only AES Counter (CTR) cipher block chaining modes in compliance with CVE-2008-5161, plugin 70658 based on vendor guidance in KB20853. This prevents certain plaintext attacks in OpenSSH.

This requires the use of secure protocols instead of their unsecured counterparts, such as SSH instead of telnet, SCP instead of FTP, and HTTPS instead of HTTP. If unsecured protocols (lacking cryptographic mechanisms) are used for sessions, the contents of those sessions will be susceptible to eavesdropping, potentially putting sensitive data (including administrator passwords) at risk of compromise and potentially allowing hijacking of maintenance sessions. Use only CTR cipher block chaining modes in compliance with CVE-2008-5161, plugin 70658 based on vendor guidance in KB20853. This prevents certain plaintext attacks in OpenSSH.

Centralized management of authentication settings increases the security of remote and nonlocal access methods. This control is particularly important protection against the insider threat. With robust centralized management, audit records for administrator account access to the organization's network devices can be more readily analyzed for trends and anomalies. The alternative method of defining administrator accounts on each device exposes the device configuration to remote access authentication attacks and system administrators with multiple authenticators for each network device.

The aggregation of log data kept on a syslog server can be used to detect attacks and trigger an alert to the appropriate security personnel. The stored log data can used to detect weaknesses in security that enable the network IA team to find and address these weaknesses before breaches can occur. Reviewing these logs, whether before or after a security breach, are important in showing whether someone is an internal employee or an outside threat.

Network devices running an unsupported operating system lack current security fixes required to mitigate the risks associated with recent vulnerabilities.

Preventing nonprivileged users from executing privileged functions mitigates the risk that unauthorized individuals or processes may gain unnecessary access to information or privileges. Privileged functions include, for example, establishing accounts, performing system integrity checks, or administering cryptographic key management activities. Nonprivileged users are individuals that do not possess appropriate authorizations.