Red Hat Enterprise Linux 10 Security Technical Implementation Guide

The debug-shell requires no authentication and provides root privileges to anyone who has physical access to the machine. While this feature is disabled by default, masking it adds an additional layer of assurance that it will not be enabled via a dependency in systemd. This also prevents attackers with physical access from trivially bypassing security on the machine through valid troubleshooting configurations and gaining root access when the system is rebooted.

Changes to any software components can have significant effects on the overall security of the operating system. This requirement ensures the software has not been tampered with and has been provided by a trusted vendor.

All software packages must be signed with a cryptographic key recognized and approved by the organization.

Verifying the authenticity of software prior to installation validates the integrity of the software package received from a vendor.

Changes to any software components can have significant effects on the overall security of the operating system. This requirement ensures the software has not been tampered with and has been provided by a trusted vendor.

All software packages must be signed with a cryptographic key recognized and approved by the organization.

Verifying the authenticity of software prior to installation validates the integrity of the software package received from a vendor.

Placing "/var/log/audit" in its own partition enables better separation between audit files and other system files and helps ensure that auditing cannot be halted due to the partition running out of space.

The "/tmp" partition is used as temporary storage by many programs. Placing "/tmp" in its own partition enables the setting of more restrictive mount options, which can help protect programs that use it.

Placing "/var/log" in its own partition enables better separation between log files and other files in "/var/".

Previous versions of software components that are not removed from the information system after updates have been installed may be exploited by some adversaries.

It is detrimental for operating systems to provide, or install by default, functionality exceeding requirements or mission objectives. These unnecessary capabilities are often overlooked and therefore, may remain unsecure. They increase the risk to the platform by providing additional attack vectors.

The telnet service provides an unencrypted remote access service, which does not provide for the confidentiality and integrity of user passwords or the remote session. If a privileged user were to log in using this service, the privileged user password could be compromised.

Removing the "telnet-server" package decreases the risk of accidental (or intentional) activation of the telnet service.

It is detrimental for operating systems to provide, or install by default, functionality exceeding requirements or mission objectives. These unnecessary capabilities or services are often overlooked and therefore, may remain unsecured. They increase the risk to the platform by providing additional attack vectors.

Operating systems 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 (e.g., key missions, functions).

The tuned package contains a daemon that tunes the system settings dynamically. It does so by monitoring the usage of several system components periodically. Based on that information, components will then be put into lower or higher power savings modes to adapt to the current usage. The tuned package is not needed for normal operating system operations.

It is detrimental for operating systems to provide, or install by default, functionality exceeding requirements or mission objectives. These unnecessary capabilities are often overlooked and therefore, may remain unsecure. They increase the risk to the platform by providing additional attack vectors.

If Trivial File Transfer Protocol (TFTP) is required for operational support (such as transmission of router configurations), its use must be documented with the information system security manager, restricted to only authorized personnel, and have access control rules established.

The FTP service provides an unencrypted remote access that does not provide for the confidentiality and integrity of user passwords or the remote session. If a privileged user were to log in using this service, the privileged user password could be compromised. Secure Shell (SSH) or other encrypted file transfer methods must be used in place of this service.

Removing the "vsftpd" package decreases the risk of accidental activation.

Satisfies: SRG-OS-000074-GPOS-00042, SRG-OS-000095-GPOS-00049

Network Security Services (NSS) is a set of libraries designed to support cross-platform development of security-enabled client and server applications. Install the "nss-tools" package to install command-line tools to manipulate the NSS certificate and key database.

The "firewalld" package provides an easy and effective way to block/limit remote access to the system via ports, services, and protocols.

Remote access services, such as those providing remote access to network devices and information systems, that lack automated control capabilities increase risk and make remote user access management difficult at best.

Remote access is access to DoW nonpublic information systems by an authorized user (or an information system) communicating through an external, nonorganizational-controlled network. Remote access methods include, for example, dial-up, broadband, and wireless.

RHEL 10 functionality (e.g., Secure Shell [SSH]) must be capable of taking enforcement action if the audit reveals unauthorized activity. Automated control of remote access sessions allows organizations to ensure ongoing compliance with remote access policies by enforcing connection rules of remote access applications on a variety of information system components (e.g., servers, workstations, notebook computers, smartphones, and tablets).

Satisfies: SRG-OS-000096-GPOS-00050, SRG-OS-000297-GPOS-00115, SRG-OS-000298-GPOS-00116, SRG-OS-000480-GPOS-00232

Failure to restrict network connectivity only to authorized systems permits inbound connections from malicious systems. It also permits outbound connections that may facilitate exfiltration of DoW data.

RHEL 10 incorporates the "firewalld" daemon, which allows for many different configurations. One of these configurations is zones. Zones can be used in a deny-all, allow-by-exception approach. The default "drop" zone will drop all incoming network packets unless it is explicitly allowed by the configuration file or is related to an outgoing network connection.

Inaccurate time stamps make it more difficult to correlate events and can lead to an inaccurate analysis. Determining the correct time a particular event occurred on a system is critical when conducting forensic analysis and investigating system events. Sources outside the configured acceptable allowance (drift) may be inaccurate.

Synchronizing internal information system clocks provides uniformity of time stamps for information systems with multiple system clocks and systems connected over a network.

Not exposing the management interface of the chrony daemon on the network diminishes the attack space.

Satisfies: SRG-OS-000096-GPOS-00050, SRG-OS-000095-GPOS-00049

The USBGuard-daemon is the main component of the USBGuard software framework. It runs as a service in the background and enforces the USB device authorization policy for all USB devices. The policy is defined by a set of rules using a rule language described in the "usbguard-rules.conf" file. The policy and the authorization state of USB devices can be modified during runtime using the USBGuard tool.

The system administrator (SA) must work with the site information system security officer (ISSO) to determine a list of authorized peripherals and establish rules within the USBGuard software framework to allow only authorized devices.

Satisfies: SRG-OS-000378-GPOS-00163, SRG-OS-000690-GPOS-00140

Without the capability to generate audit records, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

If auditing is enabled late in the startup process, the actions of some startup processes may not be audited. Some audit systems also maintain state information only available if auditing is enabled before a given process is created.

Audit records can be generated from various components within the information system (e.g., module or policy filter).

The list of audited events is the set of events for which audits are to be generated. This set of events is typically a subset of the list of all events for which the system is capable of generating audit records.

DoW has defined the list of events for which RHEL 10 will provide an audit record generation capability as the following:

1) Successful and unsuccessful attempts to access, modify, or delete privileges, security objects, security levels, or categories of information (e.g., classification levels).

2) Access actions, such as successful and unsuccessful login attempts, privileged activities or other system-level access, starting and ending time for user access to the system, concurrent logins from different workstations, successful and unsuccessful accesses to objects, all program initiations, and all direct access to the information system.

3) All account creations, modifications, disabling, and terminations.

4) All kernel module load, unload, and restart actions.

Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000471-GPOS-00215

The "policycoreutils-python-utils" package is required to operate and manage an SELinux environment and its policies. It provides utilities such as "semanage", "audit2allow", "audit2why", "chcat", and "sandbox".

The organization must identify authorized software programs and permit execution of authorized software. The process used to identify software programs that are authorized to execute on organizational information systems is commonly referred to as allowlisting.

Using an allowlist provides a configuration management method for allowing the execution of only authorized software. Using only authorized software decreases risk by limiting the number of potential vulnerabilities. Verification of allowlisted software occurs prior to execution or at system startup.

User home directories/folders may contain information of a sensitive nature. Nonprivileged users should coordinate any sharing of information with a system administrator through shared resources.

RHEL 10 ships with many optional packages. One such package is a file access policy daemon called "fapolicyd". This is a userspace daemon that determines access rights to files based on attributes of the process and file. It can be used to either blocklist or allowlist processes or file access.

Proceed with caution with enforcing the use of this daemon. Improper configuration may render the system nonfunctional. The "fapolicyd" API is not namespace aware and can cause issues when launching or running containers.

Satisfies: SRG-OS-000370-GPOS-00155, SRG-OS-000368-GPOS-00154

The organization must identify authorized software programs and permit execution of authorized software. The process used to identify software programs that are authorized to execute on organizational information systems is commonly referred to as allowlisting.

Using an allowlist provides a configuration management method for allowing the execution of only authorized software. Using only authorized software decreases risk by limiting the number of potential vulnerabilities. Verification of allowlisted software occurs prior to execution or at system startup.

User home directories/folders may contain information of a sensitive nature. Nonprivileged users should coordinate any sharing of information with a system administrator through shared resources.

RHEL 10 ships with many optional packages. One such package is a file access policy daemon called "fapolicyd". The "fapolicyd" is a userspace daemon that determines access rights to files based on attributes of the process and file. It can be used to either block list or allowlist processes or file access.

Proceed with caution with enforcing the use of this daemon. Improper configuration may render the system nonfunctional. The "fapolicyd" application programming interface (API) is not namespace aware and can cause issues when launching or running containers.

Satisfies: SRG-OS-000368-GPOS-00154, SRG-OS-000370-GPOS-00155

The information system ensures that even if the information system is compromised, that compromise will not affect credentials stored on the authentication device.

The daemon program for pcsc-lite and the MuscleCard framework is pcscd. It is a resource manager that coordinates communications with smart card readers and smart cards and cryptographic tokens that are connected to the system.

The use of Personal Identity Verification (PIV) credentials facilitates standardization and reduces the risk of unauthorized access.

The DoW has mandated the use of the common access card (CAC) to support identity management and personal authentication for systems covered under Homeland Security Presidential Directive (HSPD) 12, as well as making the CAC a primary component of layered protection for national security systems.

Satisfies: SRG-OS-000375-GPOS-00160, SRG-OS-000376-GPOS-00161

Without verification of the security functions, security functions may not operate correctly, and the failure may go unnoticed. Security function is defined as the hardware, software, and/or firmware of the information system responsible for enforcing the system security policy and supporting the isolation of code and data on which the protection is based.

Security functionality includes, but is not limited to, establishing system accounts, configuring access authorizations (e.g., permissions, privileges), setting events to be audited, and setting intrusion detection parameters.

RHEL 10 installation media ships with an optional file integrity tool called Advanced Intrusion Detection Environment (AIDE). AIDE is highly configurable at install time. This requirement assumes the "aide.conf" file is under the "/etc" directory.

File integrity tools use cryptographic hashes for verifying that file contents and directories have not been altered. These hashes must be FIPS 140-3-approved cryptographic hashes.

RHEL 10 installation media ships with an optional file integrity tool called Advanced Intrusion Detection Environment (AIDE). AIDE is highly configurable at install time. This requirement assumes the "aide.conf" file is under the "/etc" directory.

ACLs can provide permissions beyond those permitted through the file mode and must be verified by the file integrity tools.

The "rsyslogd" is a system utility providing support for message logging. Support for both internet and Unix domain sockets enables this utility to support local and remote logging. Couple this utility with "gnutls" (which is a secure communications library implementing the Secure Sockets Layer [SSL], Transport Layer Security [TLS], and Datagram TLS [DTLS] protocols), to create a method to securely encrypt and off-load auditing.

Satisfies: SRG-OS-000479-GPOS-00224, SRG-OS-000051-GPOS-00024

Information stored in one location is vulnerable to accidental or incidental deletion or alteration.

Off-loading is a common process in information systems with limited audit storage capacity.

RHEL 10 installation media provides "rsyslogd", a system utility providing support for message logging. Support for both internet and Unix domain sockets enables this utility to support both local and remote logging. Coupling this utility with "gnutls" (a secure communications library implementing the Secure Sockets Layer [SSL], Transport Layer Security [TLS], and Datagram TLS [DTLS] protocols) creates a method to securely encrypt and off-load auditing.

The rsyslog provides three ways to forward message: the traditional User Datagram Protocol (UDP) transport, which is extremely lossy but standard; the plain TCP-based transport, which loses messages only during certain situations but is widely available; and the Reliable Event Logging Protocol (RELP) transport, which does not lose messages but is currently available only as part of the rsyslogd 3.15.0 and above.

Examples of each configuration:

UDP *.* @remotesystemname
TCP *.* @@remotesystemname
RELP *.* :omrelp:remotesystemname:2514

Note that a port number was given as there is no standard port for RELP.

Information stored in one location is vulnerable to accidental or incidental deletion or alteration.

Off-loading is a common process in information systems with limited audit storage capacity.

RHEL 10 installation media provides "rsyslogd", a system utility providing support for message logging. Support for both internet and Unix domain sockets enables this utility to support both local and remote logging. Coupling this utility with "gnutls" (a secure communications library implementing the Secure Sockets Layer (SSL), Transport Layer Security (TLS), and Datagram TLS (DTLS) protocols) creates a method to securely encrypt and off-load auditing.

The "rsyslog" supported authentication modes include:
- anon - Anonymous authentication.
- x509/fingerprint - Certificate fingerprint authentication.
- x509/certvalid - Certificate validation only.
- x509/name - Certificate validation and subject name authentication.

Satisfies: SRG-OS-000342-GPOS-00133, SRG-OS-000479-GPOS-00224

Information stored in one location is vulnerable to accidental or incidental deletion or alteration.

Off-loading is a common process in information systems with limited audit storage capacity.

RHEL 10 installation media provides "rsyslogd", a system utility providing support for message logging. Support for both internet and Unix domain sockets enables this utility to support both local and remote logging. Coupling this utility with "gnutls" (a secure communications library implementing the Secure Sockets Layer [SSL], Transport Layer Security [TLS], and Datagram TLS [DTLS] protocols) creates a method to securely encrypt and off-load auditing. When this utility is coupled with the omfwd module, it can use the ossl network stream driver, which leverages the OpenSSL library for Transport Layer Security (TLS) to securely encrypt and off-load auditing.

Satisfies: SRG-OS-000342-GPOS-00133, SRG-OS-000479-GPOS-00224

Cron logging can be used to trace the successful or unsuccessful execution of cron jobs. It can also be used to spot intrusions into the use of the cron facility by unauthorized and malicious users.

Without establishing what type of events occurred, along with the source, location, and outcome, it would be difficult to establish, correlate, and investigate the events leading up to an outage or attack.

Audit record content that may be necessary to satisfy this requirement includes, for example, time stamps, source and destination addresses, user/process identifiers, event descriptions, success/fail indications, filenames involved, and access control or flow control rules invoked.

Associating event types with detected events in audit logs provides a means of investigating an attack, recognizing resource utilization or capacity thresholds, or identifying an improperly configured RHEL 10 system.

Satisfies: SRG-OS-000062-GPOS-00031, SRG-OS-000037-GPOS-00015, SRG-OS-000038-GPOS-00016, SRG-OS-000039-GPOS-00017, SRG-OS-000040-GPOS-00018, SRG-OS-000041-GPOS-00019, SRG-OS-000042-GPOS-00021, SRG-OS-000051-GPOS-00024, SRG-OS-000054-GPOS-00025, SRG-OS-000122-GPOS-00063, SRG-OS-000254-GPOS-00095, SRG-OS-000255-GPOS-00096, SRG-OS-000337-GPOS-00129, SRG-OS-000348-GPOS-00136, SRG-OS-000349-GPOS-00137, SRG-OS-000350-GPOS-00138, SRG-OS-000351-GPOS-00139, SRG-OS-000352-GPOS-00140, SRG-OS-000353-GPOS-00141, SRG-OS-000354-GPOS-00142, SRG-OS-000358-GPOS-00145, SRG-OS-000365-GPOS-00152, SRG-OS-000392-GPOS-00172, SRG-OS-000475-GPOS-00220

The "audispd-plugins" package provides plugins for the real-time interface to the audit subsystem, "audispd". These plugins can do such things as relay events to remote machines or analyze events for suspicious behavior.

The "postfix" package provides the mail command required to allow sending email notifications of unauthorized configuration changes to designated personnel.

If unrestricted mail relaying is permitted, unauthorized senders could use this host as a mail relay to send spam or for other unauthorized activity.

Without protection of the transmitted information, confidentiality and integrity may be compromised because unprotected communications can be intercepted and read or altered.

This requirement applies to internal and external networks and all types of information system components from which information can be transmitted (e.g., servers, mobile devices, notebook computers, printers, copiers, scanners, and facsimile machines). Communication paths outside the physical protection of a controlled boundary are exposed to the possibility of interception and modification.

Protecting the confidentiality and integrity of organizational information can be accomplished by physical means (e.g., employing physical distribution systems) or by logical means (e.g., employing cryptographic techniques). If physical means of protection are employed, logical means (cryptography) do not have to be employed, and vice versa.

Satisfies: SRG-OS-000423-GPOS-00187, SRG-OS-000424-GPOS-00188, SRG-OS-000425-GPOS-00189, SRG-OS-000426-GPOS-00190

This package includes utilities to make encrypted connections and transfer files securely to Secure Shell (SSH) servers.

"GnuTLS" is a secure communications library implementing the Secure Sockets Layer (SSL), Transport Layer Security (TLS), and Datagram TLS (DTLS) protocols and technologies around them. It provides a simple C language application programming interface (API) to access the secure communications protocols as well as APIs to parse and write X.509, PKCS #12, OpenPGP, and other required structures. This package contains command line TLS client and server and certificate manipulation tools.

Centralized cryptographic policies simplify applying secure ciphers across an operating system and the applications that run on that operating system. Use of weak or untested encryption algorithms undermines the purposes of using encryption to protect data.

Satisfies: SRG-OS-000033-GPOS-00014, SRG-OS-000396-GPOS-00176, SRG-OS-000393-GPOS-00173, SRG-OS-000394-GPOS-00174

Without cryptographic integrity protections, information can be altered by unauthorized users without detection.

Remote access (e.g., Remote Desktop Protocol [RDP]) is access to DoW nonpublic information systems by an authorized user (or an information system) communicating through an external, nonorganizational-controlled network. Remote access methods include, for example, dial-up, broadband, and wireless.

Cryptographic mechanisms used for protecting the integrity of information include, for example, signed hash functions that use asymmetric cryptography. This enables distribution of the public key to verify the hash information while maintaining the confidentiality of the secret key used to generate the hash.

RHEL 10 incorporates systemwide crypto policies by default. The SSH configuration file has no effect on the ciphers, MACs, or algorithms unless specifically defined in the "/etc/sysconfig/sshd" file. The employed algorithms can be viewed in the "/etc/crypto-policies/back-ends/openssh.config" file.

Satisfies: SRG-OS-000033-GPOS-00014, SRG-OS-000125-GPOS-00065, SRG-OS-000250-GPOS-00093, SRG-OS-000393-GPOS-00173, SRG-OS-000394-GPOS-00174, SRG-OS-000423-GPOS-00187

Without cryptographic integrity protections, information can be altered by unauthorized users without detection.

Remote access (e.g., Remote Desktop Protocol [RDP]) is access to DoW nonpublic information systems by an authorized user (or an information system) communicating through an external, nonorganizational-controlled network. Remote access methods include, for example, dial-up, broadband, and wireless.

Cryptographic mechanisms used for protecting the integrity of information include, for example, signed hash functions that use asymmetric cryptography. This enables distribution of the public key to verify the hash information while maintaining the confidentiality of the secret key used to generate the hash.

RHEL 10 incorporates systemwide crypto policies by default. The SSH configuration file has no effect on the ciphers, MACs, or algorithms unless specifically defined in the "/etc/sysconfig/sshd" file. The employed algorithms can be viewed in the "/etc/crypto-policies/back-ends/openssh.config" file.

Satisfies: SRG-OS-000125-GPOS-00065, SRG-OS-000250-GPOS-00093

Overriding the systemwide cryptographic policy makes the behavior of the Libreswan service violate expectations and makes system configuration more fragmented.

Centralized cryptographic policies simplify applying secure ciphers across an operating system and the applications that run on that operating system. Use of weak or untested encryption algorithms undermines the purposes of using encryption to protect data.

Satisfies: SRG-OS-000396-GPOS-00176, SRG-OS-000393-GPOS-00173, SRG-OS-000394-GPOS-00174

The "/etc/group" file contains information regarding groups that are configured on the system. Protection of this file is important for system security.

The "/etc/group-" file is a backup file of "/etc/group", and as such contains information regarding groups that are configured on the system. Protection of this file is important for system security.

The "/etc/gshadow" file contains group password hashes. Protection of this file is critical for system security.

The "/etc/gshadow-" file is a backup of "/etc/gshadow", and as such contains group password hashes. Protection of this file is critical for system security.

The "/etc/passwd" file contains information about the users that are configured on the system. Protection of this file is critical for system security.

The "/etc/passwd-" file is a backup file of "/etc/passwd", and as such contains information about the users that are configured on the system. Protection of this file is critical for system security.

The "/etc/shadow" file stores password hashes. Protection of this file is critical for system security.

The "/etc/shadow-" file is a backup file of "/etc/shadow", and as such contains the list of local system accounts and password hashes. Protection of this file is critical for system security.

Only authorized personnel should be aware of errors and the details of the errors. Error messages are an indicator of an organization's operational state or can identify the RHEL 10 system or platform. Additionally, personally identifiable information (PII) and operational information must not be revealed through error messages to unauthorized personnel or their designated representatives.

The structure and content of error messages must be carefully considered by the organization and development team. The extent to which the information system is able to identify and handle error conditions is guided by organizational policy and operational requirements.

Only authorized personnel should be aware of errors and the details of the errors. Error messages are an indicator of an organization's operational state or can identify the RHEL 10 system or platform. Additionally, personally identifiable information (PII) and operational information must not be revealed through error messages to unauthorized personnel or their designated representatives.

The structure and content of error messages must be carefully considered by the organization and development team. The extent to which the information system is able to identify and handle error conditions is guided by organizational policy and operational requirements.

If RHEL 10 allowed any user to make changes to software libraries, those changes might be implemented without undergoing the appropriate testing and approvals that are part of a robust change management process.

This requirement applies to RHEL 10 with software libraries that are accessible and configurable, as in the case of interpreted languages. Software libraries also include privileged programs that execute with escalated privileges.

If RHEL 10 allowed any user to make changes to software libraries, those changes might be implemented without undergoing the appropriate testing and approvals that are part of a robust change management process.

This requirement applies to RHEL 10 with software libraries that are accessible and configurable, as in the case of interpreted languages. Software libraries also include privileged programs that execute with escalated privileges.

If RHEL 10 allowed any user to make changes to software libraries, those changes might be implemented without undergoing the appropriate testing and approvals that are part of a robust change management process.

This requirement applies to RHEL 10 with software libraries that are accessible and configurable, as in the case of interpreted languages. Software libraries also include privileged programs that execute with escalated privileges.

Service configuration files enable or disable features of their respective services, which if configured incorrectly can lead to insecure and vulnerable configurations. Therefore, service configuration files should be owned by the correct group to prevent unauthorized changes.

If an unauthorized or modified device is allowed to exist on the system, the system may perform unintended or unauthorized operations.

Service configuration files enable or disable features of their respective services, which if configured incorrectly can lead to insecure and vulnerable configurations. Therefore, service configuration files must be owned by the correct group to prevent unauthorized changes.

Unauthorized disclosure of audit records can reveal system and configuration data to attackers, thus compromising its confidentiality.

Satisfies: SRG-OS-000057-GPOS-00027, SRG-OS-000058-GPOS-00028, SRG-OS-000059-GPOS-00029, SRG-OS-000206-GPOS-00084

Unauthorized disclosure of audit records can reveal system and configuration data to attackers, thus compromising its confidentiality.

Satisfies: SRG-OS-000057-GPOS-00027, SRG-OS-000058-GPOS-00028, SRG-OS-000059-GPOS-00029, SRG-OS-000206-GPOS-00084

Only authorized personnel should be aware of errors and the details of the errors. Error messages are an indicator of an organization's operational state or can identify the RHEL 10 system or platform. Additionally, personally identifiable information (PII) and operational information must not be revealed through error messages to unauthorized personnel or their designated representatives.

The structure and content of error messages must be carefully considered by the organization and development team. The extent to which the information system is able to identify and handle error conditions is guided by organizational policy and operational requirements.

Satisfies: SRG-OS-000057-GPOS-00027, SRG-OS-000058-GPOS-00028, SRG-OS-000059-GPOS-00029, SRG-OS-000206-GPOS-00084

The "/etc/audit/" directory contains files that ensure the proper auditing of command execution, privilege escalation, file manipulation, and more. Protection of this directory is critical for system security.

If RHEL 10 allowed any user to make changes to software libraries, those changes might be implemented without undergoing the appropriate testing and approvals that are part of a robust change management process.

This requirement applies to RHEL 10 with software libraries that are accessible and configurable, as in the case of interpreted languages. Software libraries also include privileged programs that execute with escalated privileges.

If RHEL 10 allowed any user to make changes to software libraries, those changes might be implemented without undergoing the appropriate testing and approvals that are part of a robust change management process.

This requirement applies to RHEL 10 with software libraries that are accessible and configurable, as in the case of interpreted languages. Software libraries also include privileged programs that execute with escalated privileges.

Only authorized personnel should be aware of errors and the details of the errors. Error messages are an indicator of an organization's operational state or can identify the RHEL 10 system or platform. Additionally, personally identifiable information (PII) and operational information must not be revealed through error messages to unauthorized personnel or their designated representatives.

The structure and content of error messages must be carefully considered by the organization and development team. The extent to which the information system is able to identify and handle error conditions is guided by organizational policy and operational requirements.

Local initialization files are used to configure the user's shell environment upon login. Malicious modification of these files could compromise accounts upon login.

The "/etc/group" file contains information regarding groups that are configured on the system. Protection of this file is important for system security.

The "/etc/gshadow" file contains group password hashes. Protection of this file is critical for system security.

If the "/etc/passwd" file is writable by a group-owner or the world, the risk of its compromise is increased. The file contains the list of accounts on the system and associated information, and protection of this file is critical for system security.

The "/etc/shadow-" file is a backup file of "/etc/shadow", and as such contains the list of local system accounts and password hashes. Protection of this file is critical for system security.

Files without a valid group owner may be unintentionally inherited if a group is assigned the same group identifier (GID) as the GID of the files without a valid group owner.

The "/etc/shadow" file contains the list of local system accounts and stores password hashes. Protection of this file is critical for system security. Failure to give ownership of this file to "root" provides the designated owner with access to sensitive information, which could weaken the system security posture.

Protecting audit information also includes identifying and protecting the tools used to view and manipulate log data; therefore, protecting audit tools is necessary to prevent unauthorized operation on audit information.

RHEL 10 systems providing tools to interface with audit information will leverage user permissions and roles identifying the user accessing the tools, and the corresponding rights the user enjoys, to make access decisions regarding the access to audit tools.

Audit tools include, but are not limited to, vendor-provided and open source audit tools needed to successfully view and manipulate audit information system activity and records. Audit tools include custom queries and report generators.

Satisfies: SRG-OS-000256-GPOS-00097, SRG-OS-000257-GPOS-00098, SRG-OS-000258-GPOS-00099

The "umask" controls the default access mode assigned to newly created files. A "umask" of "077" limits new files to mode "600" or less permissive. Although "umask" can be represented as a four-digit number, the first digit representing special access modes is typically ignored or required to be "0".

This requirement applies to the globally configured system defaults and the local interactive user defaults for each account on the system.

Setting the most restrictive default permissions ensures that when new accounts are created, they do not have unnecessary access.

Excessive permissions on local interactive user home directories may allow unauthorized access to user files by other users.

The "root" group is a highly privileged group. Furthermore, the group owner of this file should not have any access privileges anyway.

The "nodev" mount option causes the system to not interpret character or block special devices. Executing character or block special devices from untrusted file systems increases the opportunity for nonprivileged users to attain unauthorized administrative access.

The only legitimate location for device files is the "/dev" directory located on the root partition, with the exception of chroot jails if implemented.

The "noexec" mount option causes the system to not execute binary files. This option must be used for mounting any file system not containing approved binary files, as they may be incompatible. Executing files from untrusted file systems increases the opportunity for nonprivileged users to attain unauthorized administrative access.

The "noexec" mount option causes the system to not execute binary files. This option must be used for mounting any file system not containing approved binary files, as they may be incompatible. Executing files from untrusted file systems increases the opportunity for nonprivileged users to attain unauthorized administrative access.

Protecting audit information also includes identifying and protecting the tools used to view and manipulate log data. Therefore, protecting audit tools is necessary to prevent unauthorized operation on audit information.

RHEL 10 systems providing tools to interface with audit information will leverage user permissions and roles identifying the user accessing the tools, and the corresponding rights the user enjoys, to make access decisions regarding the access to audit tools.

Audit tools include, but are not limited to, vendor-provided and open source audit tools needed to successfully view and manipulate audit information system activity and records. Audit tools include custom queries and report generators.

Satisfies: SRG-OS-000256-GPOS-00097, SRG-OS-000257-GPOS-00098, SRG-OS-000258-GPOS-00099

In the event of a system failure, RHEL 10 must preserve any information necessary to determine cause of failure and return to operations with least disruption to system processes.

Without establishing what type of events occurred, along with the source, location, and outcome, it would be difficult to establish, correlate, and investigate the events leading up to an outage or attack.

If option "local_events" is not set to "yes", only events from the network will be aggregated.

Without auditing of these events, it may be harder or impossible to identify what an attacker did after an attack.

Without the capability to generate audit records, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

If auditing is enabled late in the startup process, the actions of some startup processes may not be audited. Some audit systems also maintain state information only available if auditing is enabled before a given process is created.

Audit records can be generated from various components within the information system (e.g., module or policy filter).

Allocating an "audit_backlog_limit" of sufficient size is critical in maintaining a stable boot process. With an insufficient limit allocated, the system is susceptible to boot failures and crashes.

Satisfies: SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000254-GPOS-00095, SRG-OS-000341-GPOS-00132, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215

If action is not taken when storage volume reaches 75 percent utilization, the auditing system may fail when the storage volume reaches capacity.

To ensure RHEL 10 systems have a sufficient storage capacity in which to write the audit logs, RHEL 10 must be able to allocate audit record storage capacity.

The task of allocating audit record storage capacity is usually performed during initial installation of RHEL 10.

Satisfies: SRG-OS-000341-GPOS-00132, SRG-OS-000342-GPOS-00133

If action is not taken when storage volume reaches 95 percent utilization, the auditing system may fail when the storage volume reaches capacity.

Without establishing what type of events occurred, along with the source, location, and outcome, it would be difficult to establish, correlate, and investigate the events leading up to an outage or attack.

Audit record content that may be necessary to satisfy this requirement includes, for example, time stamps, source and destination addresses, user/process identifiers, event descriptions, success/fail indications, filenames involved, and access control or flow control rules invoked.

Enriched logging aids in making sense of who, what, and when events occur on a system. Without this, determining root cause of an event will be much more difficult.

If security personnel are not notified immediately when storage volume reaches 75 percent utilization, they are unable to plan for audit record storage capacity expansion.

SSH provides several logging levels with varying amounts of verbosity. "DEBUG" is specifically not recommended other than strictly for debugging SSH communications because it provides so much data that it is difficult to identify important security information. "INFO" or "VERBOSE" level is the basic level that only records login activity of SSH users. In many situations, such as incident response, it is important to determine when a particular user was active on a system. The logout record can eliminate users who disconnected, which helps narrow the field.

Without generating audit records that are specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

Audit records can be generated from various components within the information system (e.g., module or policy filter).

When a user logs on, the auid is set to the uid of the account that is being authenticated. Daemons are not user sessions and have the loginuid set to -1. The auid representation is an unsigned 32-bit integer, which equals 4294967295. The audit system interprets -1, 4294967295, and "unset" in the same way.

The system call rules are loaded into a matching engine that intercepts each syscall made by all programs on the system. Therefore, it is very important to use syscall rules only when absolutely necessary because these affect performance. More rules lead to poorer performance. The performance can be helped, however, by combining syscalls into one rule whenever possible.

Satisfies: SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000458-GPOS-00203, SRG-OS-000462-GPOS-00206, SRG-OS-000463-GPOS-00207, SRG-OS-000471-GPOS-00215, SRG-OS-000474-GPOS-00219, SRG-OS-000466-GPOS-00210, SRG-OS-000468-GPOS-00212, SRG-OS-000064-GPOS-00033

Without generating audit records specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

Audit records can be generated from various components within the information system (e.g., module or policy filter).

When a user logs on, the auid is set to the uid of the account being authenticated. Daemons are not user sessions and have the loginuid set to -1. The auid representation is an unsigned 32-bit integer, which equals 4294967295. The audit system interprets -1, 4294967295, and "unset" in the same way.

The system call rules are loaded into a matching engine that intercepts each system call made by all programs on the system. Therefore, it is very important to use system call rules only when absolutely necessary because these affect performance. More rules lead to poorer performance. The performance can be helped, however, by combining system calls into one rule whenever possible.

Satisfies: SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215, SRG-OS-000466-GPOS-00210

Without generating audit records that are specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

Audit records can be generated from various components within the information system (e.g., module or policy filter).

When a user logs on, the auid is set to the uid of the account that is being authenticated. Daemons are not user sessions and have the loginuid set to -1. The auid representation is an unsigned 32-bit integer, which equals 4294967295. The audit system interprets -1, 4294967295, and "unset" in the same way.

The system call rules are loaded into a matching engine that intercepts each system call made by all programs on the system. Therefore, it is very important to use system call rules only when absolutely necessary because these affect performance. More rules lead to poorer performance. The performance can be helped, however, by combining system calls into one rule whenever possible.

Satisfies: SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000468-GPOS-00212, SRG-OS-000471-GPOS-00215, SRG-OS-000463-GPOS-00207, SRG-OS-000465-GPOS-00209

Without generating audit records specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

Audit records can be generated from various components within the information system (e.g., module or policy filter).

When a user logs on, the auid is set to the uid of the account being authenticated. Daemons are not user sessions and have the loginuid set to -1. The auid representation is an unsigned 32-bit integer, which equals 4294967295. The audit system interprets -1, 4294967295, and "unset" in the same way.

The system call rules are loaded into a matching engine that intercepts each system call made by all programs on the system. Therefore, it is very important to use system call rules only when absolutely necessary because these affect performance. More rules lead to poorer performance. The performance can be helped, however, by combining system calls into one rule whenever possible.

Satisfies: SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215, SRG-OS-000463-GPOS-00207, SRG-OS-000465-GPOS-00209

Without generating audit records that are specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

Audit records can be generated from various components within the information system (e.g., module or policy filter).

When a user logs on, the auid is set to the uid of the account that is being authenticated. Daemons are not user sessions and have the loginuid set to -1. The auid representation is an unsigned 32-bit integer, which equals 4294967295. The audit system interprets -1, 4294967295, and "unset" in the same way.

The system call rules are loaded into a matching engine that intercepts each syscall made by all programs on the system. Therefore, it is very important to use syscall rules only when absolutely necessary because these affect performance. More rules lead to poorer performance. The performance can be helped, however, by combining syscalls into one rule whenever possible.

Satisfies: SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215, SRG-OS-000064-GPOS-00033, SRG-OS-000458-GPOS-00203, SRG-OS-000461-GPOS-00205

Without generating audit records that are specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

Audit records can be generated from various components within the information system (e.g., module or policy filter).

When a user logs on, the auid is set to the uid of the account that is being authenticated. Daemons are not user sessions and have the loginuid set to -1. The auid representation is an unsigned 32-bit integer, which equals 4294967295. The audit system interprets -1, 4294967295, and "unset" in the same way.

The system call rules are loaded into a matching engine that intercepts each syscall made by all programs on the system. Therefore, it is very important to use syscall rules only when absolutely necessary because these affect performance. More rules lead to poorer performance. The performance can be helped, however, by combining syscalls into one rule whenever possible.

Satisfies: SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215, SRG-OS-000471-GPOS-00216, SRG-OS-000477-GPOS-00222

Without generating audit records specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

Audit records can be generated from various components within the information system (e.g., module or policy filter).

When a user logs on, the auid is set to the uid of the account being authenticated. Daemons are not user sessions and have the loginuid set to -1. The auid representation is an unsigned 32-bit integer, which equals 4294967295. The audit system interprets -1, 4294967295, and "unset" in the same way.

The system call rules are loaded into a matching engine that intercepts each system call made by all programs on the system. Therefore, it is very important to use system call rules only when absolutely necessary because these affect performance. More rules lead to poorer performance. The performance can be helped, however, by combining system calls into one rule whenever possible.

Satisfies: SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215

Without generating audit records specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

Audit records can be generated from various components within the information system (e.g., module or policy filter).

When a user logs on, the auid is set to the uid of the account being authenticated. Daemons are not user sessions and have the loginuid set to -1. The auid representation is an unsigned 32-bit integer, which equals 4294967295. The audit system interprets -1, 4294967295, and "unset" in the same way.

The system call rules are loaded into a matching engine that intercepts each system call made by all programs on the system. Therefore, it is very important to use system call rules only when absolutely necessary because these affect performance. More rules lead to poorer performance. The performance can be helped, however, by combining system calls into one rule whenever possible.

Satisfies: SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215

Without generating audit records specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

Audit records can be generated from various components within the information system (e.g., module or policy filter).

When a user logs on, the auid is set to the uid of the account that is being authenticated. Daemons are not user sessions and have the loginuid set to -1. The auid representation is an unsigned 32-bit integer, which equals 4294967295. The audit system interprets -1, 4294967295, and "unset" in the same way.

The system call rules are loaded into a matching engine that intercepts each system call made by all programs on the system. Therefore, it is very important to use system call rules only when absolutely necessary because these affect performance. More rules lead to poorer performance. The performance can be helped, however, by combining system calls into one rule whenever possible.

Satisfies: SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215

Without generating audit records specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

Audit records can be generated from various components within the information system (e.g., module or policy filter).

When a user logs on, the auid is set to the uid of the account being authenticated. Daemons are not user sessions and have the loginuid set to -1. The auid representation is an unsigned 32-bit integer, which equals 4294967295. The audit system interprets -1, 4294967295, and "unset" in the same way.

The system call rules are loaded into a matching engine that intercepts each system call made by all programs on the system. Therefore, it is very important to use system call rules only when absolutely necessary because these affect performance. More rules lead to poorer performance. The performance can be helped, however, by combining system calls into one rule whenever possible.

Satisfies: SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215

Without generating audit records specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

Audit records can be generated from various components within the information system (e.g., module or policy filter).

When a user logs on, the auid is set to the uid of the account being authenticated. Daemons are not user sessions and have the loginuid set to -1. The auid representation is an unsigned 32-bit integer, which equals 4294967295. The audit system interprets -1, 4294967295, and "unset" in the same way.

The system call rules are loaded into a matching engine that intercepts each system call made by all programs on the system. Therefore, it is very important to use system call rules only when absolutely necessary because these affect performance. More rules lead to poorer performance. The performance can be helped, however, by combining system calls into one rule whenever possible.

Satisfies: SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215

Without generating audit records specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

Audit records can be generated from various components within the information system (e.g., module or policy filter).

When a user logs on, the auid is set to the uid of the account being authenticated. Daemons are not user sessions and have the loginuid set to -1. The auid representation is an unsigned 32-bit integer, which equals 4294967295. The audit system interprets -1, 4294967295, and "unset" in the same way.

The system call rules are loaded into a matching engine that intercepts each system call made by all programs on the system. Therefore, it is very important to use system call rules only when absolutely necessary because these affect performance. More rules lead to poorer performance. The performance can be helped, however, by combining system calls into one rule whenever possible.

Satisfies: SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215

Without generating audit records specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

Audit records can be generated from various components within the information system (e.g., module or policy filter).

When a user logs on, the auid is set to the uid of the account being authenticated. Daemons are not user sessions and have the loginuid set to -1. The auid representation is an unsigned 32-bit integer, which equals 4294967295. The audit system interprets -1, 4294967295, and "unset" in the same way.

The system call rules are loaded into a matching engine that intercepts each system call made by all programs on the system. Therefore, it is very important to use system call rules only when absolutely necessary because these affect performance. More rules lead to poorer performance. The performance can be helped, however, by combining system calls into one rule whenever possible.

Satisfies: SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215, SRG-OS-000466-GPOS-00210, SRG-OS-000755-GPOS-00220

Without generating audit records specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

Audit records can be generated from various components within the information system (e.g., module or policy filter).

When a user logs on, the auid is set to the uid of the account being authenticated. Daemons are not user sessions and have the loginuid set to -1. The auid representation is an unsigned 32-bit integer, which equals 4294967295. The audit system interprets -1, 4294967295, and "unset" in the same way.

The system call rules are loaded into a matching engine that intercepts each system call made by all programs on the system. Therefore, it is very important to use system call rules only when absolutely necessary because these affect performance. More rules lead to poorer performance. The performance can be helped, however, by combining system calls into one rule whenever possible.

Satisfies: SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215

Without generating audit records specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

Audit records can be generated from various components within the information system (e.g., module or policy filter).

When a user logs on, the auid is set to the uid of the account being authenticated. Daemons are not user sessions and have the loginuid set to -1. The auid representation is an unsigned 32-bit integer, which equals 4294967295. The audit system interprets -1, 4294967295, and "unset" in the same way.

The system call rules are loaded into a matching engine that intercepts each system call made by all programs on the system. Therefore, it is very important to use system call rules only when absolutely necessary because these affect performance. More rules lead to poorer performance. The performance can be helped, however, by combining system calls into one rule whenever possible.

Satisfies: SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215

Without generating audit records that are specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

Audit records can be generated from various components within the information system (e.g., module or policy filter).

When a user logs on, the auid is set to the uid of the account that is being authenticated. Daemons are not user sessions and have the loginuid set to -1. The auid representation is an unsigned 32-bit integer, which equals 4294967295. The audit system interprets -1, 4294967295, and "unset" in the same way.

The system call rules are loaded into a matching engine that intercepts each syscall made by all programs on the system. Therefore, it is very important to use syscall rules only when absolutely necessary because these affect performance. More rules lead to poorer performance. The performance can be helped, however, by combining syscalls into one rule whenever possible.

Satisfies: SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215

Misuse of the "poweroff" command may cause availability issues for the system.

Misuse of the shutdown command may cause availability issues for the system.

The changing of file permissions could indicate that a user is attempting to gain access to information that would otherwise be disallowed. Auditing discretionary access control (DAC) modifications can facilitate the identification of patterns of abuse among both authorized and unauthorized users.

Satisfies: SRG-OS-000037-GPOS-00015, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215

The actions taken by system administrators must be audited to keep a record of what was executed on the system, as well as for accountability purposes. Editing the "sudoers" file may be a sign of an attacker trying to establish persistent methods to a system. Auditing the editing of the "sudoers" files mitigates this risk.

Satisfies: SRG-OS-000004-GPOS-00004, SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000304-GPOS-00121, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000470-GPOS-00214, SRG-OS-000471-GPOS-00215, SRG-OS-000239-GPOS-00089, SRG-OS-000240-GPOS-00090, SRG-OS-000241-GPOS-00091, SRG-OS-000303-GPOS-00120, SRG-OS-000466-GPOS-00210, SRG-OS-000476-GPOS-00221

In addition to auditing new user and group accounts, these watches will alert the system administrator(s) to any modifications. Any unexpected users, groups, or modifications should be investigated for legitimacy.

Satisfies: SRG-OS-000004-GPOS-00004, SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000304-GPOS-00121, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000470-GPOS-00214, SRG-OS-000471-GPOS-00215, SRG-OS-000239-GPOS-00089, SRG-OS-000240-GPOS-00090, SRG-OS-000241-GPOS-00091, SRG-OS-000303-GPOS-00120, SRG-OS-000466-GPOS-00210, SRG-OS-000476-GPOS-00221

In addition to auditing new user and group accounts, these watches will alert the system administrator(s) to any modifications. Any unexpected users, groups, or modifications should be investigated for legitimacy.

Satisfies: SRG-OS-000004-GPOS-00004, SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000304-GPOS-00121, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000470-GPOS-00214, SRG-OS-000471-GPOS-00215, SRG-OS-000239-GPOS-00089, SRG-OS-000240-GPOS-00090, SRG-OS-000241-GPOS-00091, SRG-OS-000303-GPOS-00120, SRG-OS-000466-GPOS-00210, SRG-OS-000476-GPOS-00221, SRG-OS-000274-GPOS-00104, SRG-OS-000275-GPOS-00105, SRG-OS-000276-GPOS-00106, SRG-OS-000277-GPOS-00107

Without generating audit records specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

Satisfies: SRG-OS-000392-GPOS-00172, SRG-OS-000470-GPOS-00214, SRG-OS-000473-GPOS-00218

Without generating audit records that are specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

Audit records can be generated from various components within the information system (e.g., module or policy filter).

When a user logs on, the auid is set to the uid of the account that is being authenticated. Daemons are not user sessions and have the loginuid set to -1. The auid representation is an unsigned 32-bit integer, which equals 4294967295. The audit system interprets -1, 4294967295, and "unset" in the same way.

The system call rules are loaded into a matching engine that intercepts each syscall made by all programs on the system. Therefore, it is very important to use syscall rules only when absolutely necessary because these affect performance. More rules lead to poorer performance. The performance can be helped, however, by combining syscalls into one rule whenever possible.

Satisfies: SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215, SRG-OS-000064-GPOS-00033, SRG-OS-000466-GPOS-00210, SRG-OS-000458-GPOS-00203

Without generating audit records that are specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

Audit records can be generated from various components within the information system (e.g., module or policy filter).

When a user logs on, the auid is set to the uid of the account that is being authenticated. Daemons are not user sessions and have the loginuid set to -1. The auid representation is an unsigned 32-bit integer, which equals 4294967295. The audit system interprets -1, 4294967295, and "unset" in the same way.

The system call rules are loaded into a matching engine that intercepts each syscall made by all programs on the system. Therefore, it is very important to use syscall rules only when absolutely necessary because these affect performance. More rules lead to poorer performance. The performance can be helped, however, by combining syscalls into one rule whenever possible.

Satisfies: SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215, SRG-OS-000466-GPOS-00210, SRG-OS-000467-GPOS-00211, SRG-OS-000468-GPOS-00212

Having a nondefault grub superuser username makes password-guessing attacks less effective.

Any password, no matter how complex, can eventually be cracked; therefore, passwords need to be changed periodically. If the operating system does not limit the lifetime of passwords and force users to change their passwords, there is the risk that the operating system passwords could be compromised.

Setting the password maximum age ensures users are required to periodically change their passwords. Requiring shorter password lifetimes increases the risk of users writing down the password in a convenient location subject to physical compromise.

If local interactive users are not assigned a valid home directory, there is no place for the storage and control of files they should own.

Temporary accounts are privileged or nonprivileged accounts that are established during pressing circumstances, such as new software or hardware configuration or an incident response, where the need for prompt account activation requires bypassing normal account authorization procedures. If any inactive temporary accounts are left enabled on the system and are not manually removed or automatically expired within 72 hours, the security posture of the system will be degraded and exposed to exploitation by unauthorized users or insider threat actors.

Temporary accounts are different from emergency accounts. Emergency accounts, also known as "last resort" or "break glass" accounts, are local login accounts enabled on the system for emergency use by authorized system administrators to manage a system when standard login methods are failing or not available. Emergency accounts are not subject to manual removal or scheduled expiration requirements.

The automatic expiration of temporary accounts may be extended as needed by the circumstances, but it must not be extended indefinitely. A documented permanent account should be established for privileged users who need long-term maintenance accounts.

Satisfies: SRG-OS-000123-GPOS-00064, SRG-OS-000002-GPOS-00002

Inactive identifiers pose a risk to systems and applications because attackers may exploit an inactive identifier and potentially obtain undetected access to the system.

Disabling inactive accounts ensures accounts that may not have been responsibly removed are not available to attackers who may have compromised their credentials.

Owners of inactive accounts will not notice if unauthorized access to their user account has been obtained.

Satisfies: SRG-OS-000118-GPOS-00060, SRG-OS-000590-GPOS-00110

If local interactive users are not assigned a valid home directory, there is no place for the storage and control of files they should own.

Increasing the time between a failed authentication attempt and reprompting to enter credentials helps to slow a single-threaded brute-force attack.

The shorter the password, the lower the number of possible combinations that must be tested before the password is compromised.

Password complexity, or strength, is a measure of the effectiveness of a password in resisting attempts at guessing and brute-force attacks. Password length is one factor of several that helps to determine strength and how long it takes to crack a password. Use of more characters in a password helps to increase exponentially the time and/or resources required to compromise the password.

RHEL 10 uses "pwquality" as a mechanism to enforce password complexity. Configurations are set in the "etc/security/pwquality.conf" file.

The "minlen", sometimes noted as minimum length, acts as a "score" of complexity based on the credit components of the "pwquality" module. By setting the credit components to a negative value, those components will not only be required but will not count toward the total "score" of "minlen". This will enable "minlen" to require a 15-character minimum.

The DoW minimum password requirement is 15 characters.

Use of a complex password helps to increase the time and resources required to compromise the password. Password complexity, or strength, is a measure of the effectiveness of a password in resisting attempts at guessing and brute-force attacks.

Password complexity is one factor of several that determines how long it takes to crack a password. The more complex the password, the greater the number of possible combinations that must be tested before the password is compromised.

Requiring a minimum number of lowercase characters makes password guessing attacks more difficult by ensuring a larger search space.

Use of a complex password helps to increase the time and resources required to compromise the password. Password complexity, or strength, is a measure of the effectiveness of a password in resisting attempts at guessing and brute–force attacks.

Password complexity is one factor of several that determines how long it takes to crack a password. The more complex the password, the greater the number of possible combinations that must be tested before the password is compromised.

Requiring a minimum number of different characters during password changes ensures that newly changed passwords should not resemble previously compromised ones.

Note that passwords that are changed on compromised systems will still be compromised.

Use of a complex password helps to increase the time and resources required to compromise the password.

Password complexity, or strength, is a measure of the effectiveness of a password in resisting attempts at guessing and brute-force attacks.

Password complexity is one factor of several that determines how long it takes to crack a password. The more complex a password is, the greater the number of possible combinations that must be tested before the password is compromised.

Satisfies: SRG-OS-000072-GPOS-00040, SRG-OS-000730-GPOS-00190

Use of a complex password helps to increase the time and resources required to compromise the password.

Password complexity, or strength, is a measure of the effectiveness of a password in resisting attempts at guessing and brute-force attacks.

Password complexity is one factor of several that determines how long it takes to crack a password. The more complex a password is, the greater the number of possible combinations that must be tested before the password is compromised.

Use of a complex password helps to increase the time and resources required to compromise the password. Password complexity, or strength, is a measure of the effectiveness of a password in resisting attempts at guessing and brute-force attacks.

If RHEL 10 allows the user to select passwords based on dictionary words, this increases the chances of password compromise by increasing the opportunity for successful guesses and brute-force attacks.

Satisfies: SRG-OS-000480-GPOS-00225, SRG-OS-000072-GPOS-00040

Use of a complex password helps to increase the time and resources required to compromise the password. Password complexity, or strength, is a measure of the effectiveness of a password in resisting attempts at guessing and brute-force attacks.

Password complexity is one factor of several that determines how long it takes to crack a password. The more complex the password, the greater the number of possible combinations that must be tested before the password is compromised.

Satisfies: SRG-OS-000072-GPOS-00040, SRG-OS-000071-GPOS-00039, SRG-OS-000070-GPOS-00038, SRG-OS-000266-GPOS-00101, SRG-OS-000078-GPOS-00046, SRG-OS-000480-GPOS-00225, SRG-OS-000069-GPOS-00037

By limiting the number of failed login attempts, the risk of unauthorized system access via user password guessing, also known as brute-forcing, is reduced. Limits are imposed by locking the account.

Satisfies: SRG-OS-000329-GPOS-00128, SRG-OS-000021-GPOS-00005

By limiting the number of failed login attempts, the risk of unauthorized system access via user password guessing, otherwise known as brute-forcing, is reduced. Limits are imposed by locking the account.

Satisfies: SRG-OS-000329-GPOS-00128, SRG-OS-000021-GPOS-00005

Having lockouts persist across reboots ensures that account is unlocked only by an administrator. If the lockouts did not persist across reboots, an attacker could reboot the system to continue brute force attacks against the accounts on the system.

If an account has an empty password, anyone could log in and run commands with the privileges of that account. Accounts with empty passwords should never be used in operational environments.

Operating system management includes the ability to control the number of users and user sessions that use an operating system. Limiting the number of allowed users and sessions per user is helpful in reducing the risks related to denial-of-service (DoS) attacks.

This requirement addresses concurrent sessions for information system accounts and does not address concurrent sessions by single users via multiple system accounts. The maximum number of concurrent sessions should be defined based on mission needs and the operational environment for each system.

The "su" program allows commands to be run with a substitute user and group ID. It is commonly used to run commands as the root user. Limiting access to such commands is considered a good security practice.

Satisfies: SRG-OS-000373-GPOS-00156, SRG-OS-000312-GPOS-00123

If the "sudoers" file is not configured correctly, any user defined on the system can initiate privileged actions on the target system.

Without reauthentication, users may access resources or perform tasks for which they do not have authorization.

When operating systems provide the capability to escalate a functional capability, it is critical that the organization requires the user to reauthenticate when using the "sudo" command.

If the value is set to an integer less than "0", the user's time stamp will not expire, and the user will not have to reauthenticate for privileged actions until the user's session is terminated.

Satisfies: SRG-OS-000373-GPOS-00156, SRG-OS-000373-GPOS-00157, SRG-OS-000373-GPOS-00158

Without reauthentication, users may access resources or perform tasks for which they do not have authorization.

When operating systems provide the capability to escalate a functional capability, it is critical that the user reauthenticate.

Satisfies: SRG-OS-000373-GPOS-00156, SRG-OS-000373-GPOS-00157, SRG-OS-000373-GPOS-00158

If the pam_faillock.so module is not loaded, the system will not correctly lock out accounts to prevent password guessing attacks.

Enabling Pluggable Authentication Module (PAM) password complexity permits enforcement of strong passwords and consequently makes the system less prone to dictionary attacks.

Unapproved mechanisms that are used for authentication to the cryptographic module are not verified; therefore, they cannot be relied on to provide confidentiality or integrity, and DoW data may be compromised.

RHEL 10 systems using encryption are required to use FIPS-compliant mechanisms for authenticating to cryptographic modules.

FIPS 140-3 is the current standard for validating that mechanisms used to access cryptographic modules use authentication that meets DoW requirements. This allows for Security Levels 1, 2, 3, or 4 for use on a general-purpose computing system.

Satisfies: SRG-OS-000073-GPOS-00041, SRG-OS-000120-GPOS-00061

Unapproved mechanisms that are used for authentication to the cryptographic module are not verified and therefore cannot be relied on to provide confidentiality or integrity, and DoW data may be compromised.

RHEL 10 systems using encryption are required to use FIPS-compliant mechanisms for authenticating to cryptographic modules.

FIPS 140-3 is the current standard for validating that mechanisms used to access cryptographic modules use authentication that meets DoW requirements. This allows for Security Levels 1, 2, 3, or 4 for use on a general-purpose computing system.

Satisfies: SRG-OS-000073-GPOS-00041, SRG-OS-000120-GPOS-00061

The system must use a strong hashing algorithm to store the password.

Passwords must 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.

Satisfies: SRG-OS-000073-GPOS-00041, SRG-OS-000120-GPOS-00061

Passwords must 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. Passwords that are encrypted with a weak algorithm are no more protected than if they are kept in plain text.

This setting ensures user and group account administration utilities are configured to store only encrypted representations of passwords. Additionally, the "crypt_style" configuration option ensures the use of a strong hashing algorithm that makes password cracking attacks more difficult.

Display of a standardized and approved use notification before granting access to the operating system ensures privacy and security notification verbiage used is consistent with applicable federal laws, Executive Orders, directives, policies, regulations, standards, and guidance.

System use notifications are required only for access via login interfaces with human users and are not required when such human interfaces do not exist.

The banner must be formatted in accordance with applicable DoW policy. Use the following verbiage for operating systems that can accommodate banners of 1300 characters:

"You are accessing a U.S. Government (USG) Information System (IS) that is provided for USG-authorized use only.

By using this IS (which includes any device attached to this IS), you consent to the following conditions:

-The USG routinely intercepts and monitors communications on this IS for purposes including, but not limited to, penetration testing, COMSEC monitoring, network operations and defense, personnel misconduct (PM), law enforcement (LE), and counterintelligence (CI) investigations.

-At any time, the USG may inspect and seize data stored on this IS.

-Communications using, or data stored on, this IS are not private, are subject to routine monitoring, interception, and search, and may be disclosed or used for any USG-authorized purpose.

-This IS includes security measures (e.g., authentication and access controls) to protect USG interests--not for your personal benefit or privacy.

-Notwithstanding the above, using this IS does not constitute consent to PM, LE or CI investigative searching or monitoring of the content of privileged communications, or work product, related to personal representation or services by attorneys, psychotherapists, or clergy, and their assistants. Such communications and work product are private and confidential. See User Agreement for details."

Satisfies: SRG-OS-000023-GPOS-00006, SRG-OS-000228-GPOS-00088

Display of a standardized and approved use notification before granting access to the operating system ensures privacy and security notification verbiage used is consistent with applicable federal laws, Executive Orders, directives, policies, regulations, standards, and guidance.

System use notifications are required only for access via login interfaces with human users and are not required when such human interfaces do not exist.

Satisfies: SRG-OS-000023-GPOS-00006, SRG-OS-000228-GPOS-00088

The "noexec" mount option causes the system not to execute binary files. This option must be used for mounting any file system not containing approved binary as they may be incompatible. Executing files from untrusted file systems increases the opportunity for nonprivileged users to attain unauthorized administrative access.

When an NFS server is configured to use RPCSEC_SYS, a selected userid and groupid are used to handle requests from the remote user. The userid and groupid could mistakenly or maliciously be set incorrectly. The RPCSEC_GSS method of authentication uses certificates on the server and client systems to more securely authenticate the remote mount request.

The "nosuid" mount option causes the system not to execute "setuid" and "setgid" files with owner privileges. This option must be used for mounting any file system not containing approved "setuid" and "setguid" files. Executing files from untrusted file systems increases the opportunity for nonprivileged users to attain unauthorized administrative access.

The "nodev" mount option causes the system to not interpret character or block special devices. Executing character or block special devices from untrusted file systems increases the opportunity for nonprivileged users to attain unauthorized administrative access.

The only legitimate location for device files is the "/dev" directory located on the root partition, with the exception of chroot jails if implemented.

The "nosuid" mount option causes the system to not execute "setuid" and "setgid" files with owner privileges. This option must be used for mounting any file system not containing approved "setuid" and "setguid" files. Executing files from untrusted file systems increases the opportunity for nonprivileged users to attain unauthorized administrative access.

The "noexec" mount option causes the system to not execute binary files. This option must be used for mounting any file system not containing approved binary files, as they may be incompatible. Executing files from untrusted file systems increases the opportunity for nonprivileged users to attain unauthorized administrative access.

The "nodev" mount option causes the system to not interpret character or block special devices. Executing character or block special devices from untrusted file systems increases the opportunity for nonprivileged users to attain unauthorized administrative access.

The only legitimate location for device files is the "/dev" directory located on the root partition, with the exception of chroot jails if implemented.

The "noexec" mount option causes the system to not execute binary files. This option must be used for mounting any file system not containing approved binary files, as they may be incompatible. Executing files from untrusted file systems increases the opportunity for nonprivileged users to attain unauthorized administrative access.

The "nodev" mount option causes the system to not interpret character or block special devices. Executing character or block special devices from untrusted file systems increases the opportunity for nonprivileged users to attain unauthorized administrative access.

The only legitimate location for device files is the "/dev" directory located on the root partition, with the exception of chroot jails if implemented.

The "nosuid" mount option causes the system to not execute "setuid" and "setgid" files with owner privileges. This option must be used for mounting any file system not containing approved "setuid" and "setguid" files. Executing files from untrusted file systems increases the opportunity for nonprivileged users to attain unauthorized administrative access.

Setting the SELinux policy to "targeted" or a more specialized policy ensures the system will confine processes that are likely to be targeted for exploitation, such as network or system services.

Note: During the development or debugging of SELinux modules, it is common to temporarily place nonproduction systems in "permissive" mode. In such temporary cases, SELinux policies should be developed, and once work is completed, the system should be reconfigured to "targeted".

Without verification of the security functions, security functions may not operate correctly and the failure may go unnoticed. Security function is defined as the hardware, software, and/or firmware of the information system responsible for enforcing the system security policy and supporting the isolation of code and data on which the protection is based.

Security functionality includes, but is not limited to, establishing system accounts, configuring access authorizations (i.e., permissions, privileges), setting events to be audited, and setting intrusion detection parameters.

This requirement applies to operating systems performing security function verification/testing and/or systems and environments that require this functionality.

Satisfies: SRG-OS-000445-GPOS-00199, SRG-OS-000134-GPOS-00068

If a public host key file is modified by an unauthorized user, the SSH service may be compromised.

Kerberos authentication for SSH is often implemented using Generic Security Service Application Program Interface (GSSAPI). If Kerberos is enabled through SSH, the SSH daemon provides a means of access to the system's Kerberos implementation. Vulnerabilities in the system's Kerberos implementations may be subject to exploitation.

OpenSSH uses the first occurrence of a keyword it sees, and drop-in files are read in lexicographical order at the start of the configuration. Red Hat recommends using drop-in files rather than changing base configuration files.

Configuring the "IgnoreUserKnownHosts" setting for the SSH daemon provides additional assurance that remote login via SSH will require a password, even in the event of misconfiguration elsewhere.

OpenSSH uses the first occurrence of a keyword it sees, and drop-in files are read in lexicographical order at the start of the configuration. Red Hat recommends using drop-in files rather than changing base configuration files.

If other users have access to modify user-specific SSH configuration files, they may be able to log in to the system as another user.

OpenSSH uses the first occurrence of a keyword it sees, and drop-in files are read in lexicographical order at the start of the configuration. Red Hat recommends using drop-in files rather than changing base configuration files.

When X11 forwarding is enabled, there may be additional exposure to the server and client displays if the sshd proxy display is configured to listen on the wildcard address. By default, sshd binds the forwarding server to the loopback address and sets the hostname part of the "DISPLAY" environment variable to localhost. This prevents remote hosts from connecting to the proxy display.

OpenSSH uses the first occurrence of a keyword it sees, and drop-in files are read in lexicographical order at the start of the configuration. Red Hat recommends using drop-in files rather than changing base configuration files.

Without the use of multifactor authentication, the ease of access to privileged functions is greatly increased. Multifactor authentication requires using two or more factors to achieve authentication. A privileged account is defined as an information system account with authorizations of a privileged user. A DoW common access card (CAC) with DoW-approved PKI is an example of multifactor authentication.

OpenSSH uses the first occurrence of a keyword it sees, and drop-in files are read in lexicographical order at the start of the configuration. Red Hat recommends using drop-in files rather than changing base configuration files.

Satisfies: SRG-OS-000105-GPOS-00052, SRG-OS-000106-GPOS-00053, SRG-OS-000107-GPOS-00054, SRG-OS-000108-GPOS-00055

Even though the communications channel may be encrypted, an additional layer of security is gained by extending the policy of not logging directly on as root. In addition, logging in with a user-specific account provides individual accountability of actions performed on the system and helps to minimize direct attack attempts on root's password.

OpenSSH uses the first occurrence of a keyword it sees, and drop-in files are read in lexicographical order at the start of the configuration. Red Hat recommends using drop-in files rather than changing base configuration files.

SSH environment options potentially allow users to bypass access restriction in some configurations.

OpenSSH uses the first occurrence of a keyword it sees, and drop-in files are read in lexicographical order at the start of the configuration. Red Hat recommends using drop-in files rather than changing base configuration files.

Terminating an idle SSH 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. Quickly terminating an idle SSH session will also free up resources committed by the managed network element.

Terminating network connections associated with communications sessions includes, for example, deallocating associated TCP/IP address/port pairs at the operating system level and deallocating networking assignments at the application level if multiple application sessions are using a single operating system-level network connection. This does not mean the operating system terminates all sessions or network access; it only ends the inactive session and releases the resources associated with that session.

RHEL 10 uses "/etc/ssh/sshd_config" for configurations of OpenSSH. Within the sshd_config, the product of the values of "ClientAliveInterval" and "ClientAliveCountMax" are used to establish the inactivity threshold. The "ClientAliveInterval" is a timeout interval in seconds after which if no data has been received from the client, sshd will send a message through the encrypted channel to request a response from the client. The "ClientAliveCountMax" is the number of client alive messages that may be sent without sshd receiving any messages back from the client. If this threshold is met, sshd will disconnect the client. For more information on these settings and others, refer to the sshd_config man pages.

OpenSSH uses the first occurrence of a keyword it sees, and drop-in files are read in lexicographical order at the start of the configuration. Red Hat recommends using drop-in files rather than changing base configuration files.

Satisfies: SRG-OS-000163-GPOS-00072, SRG-OS-000279-GPOS-00109

The "shosts.equiv" files are used to configure host-based authentication for the system via Secure Shell (SSH). Host-based authentication is not sufficient for preventing unauthorized access to the system, as it does not require interactive identification and authentication of a connection request, or for the use of two-factor authentication.

Without identifying and authenticating devices, unidentified or unknown devices may be introduced, thereby facilitating malicious activity.

Peripherals include, but are not limited to, such devices as flash drives, external storage, and printers.

Satisfies: SRG-OS-000114-GPOS-00059, SRG-OS-000378-GPOS-00163

Failure to restrict system access to authenticated users negatively impacts operating system security.

A session timeout lock is a temporary action taken when a user stops work and moves away from the immediate physical vicinity of the information system but does not log out because of the temporary nature of the absence. Rather than relying on the user to manually lock their operating system session prior to vacating the vicinity, operating systems must be able to identify when a user's session has idled and take action to initiate the session lock.

The session lock is implemented at the point where session activity can be determined and/or controlled.

Implementing session settings will have little value if a user is able to manipulate these settings from the defaults prescribed in the other requirements of this implementation guide.

Satisfies: SRG-OS-000028-GPOS-00009, SRG-OS-000030-GPOS-00011

A session timeout lock is a temporary action taken when a user stops work and moves away from the immediate physical vicinity of the information system but does not log out because of the temporary nature of the absence. Rather than relying on the user to manually lock their operating system session prior to vacating the vicinity, the GNOME desktop can be configured to identify when a user's session has idled and take action to initiate the session lock. Therefore, users should not be allowed to change session settings.

Satisfies: SRG-OS-000029-GPOS-00010, SRG-OS-000031-GPOS-00012

A session timeout lock is a temporary action taken when a user stops work and moves away from the immediate physical vicinity of the information system but does not log out because of the temporary nature of the absence. Rather than relying on the user to manually lock their operating system session prior to vacating the vicinity, the GNOME desktop can be configured to identify when a user's session has idled and take action to initiate the session lock. Therefore, users should not be allowed to change session settings.

Satisfies: SRG-OS-000029-GPOS-00010, SRG-OS-000031-GPOS-00012

Unlike text-based keyfiles, the binary database is impossible to check through most automated and all manual means; therefore, to evaluate dconf configuration, both must be true at the same time. Configuration files must be compliant, and the database must be more recent than those keyfiles, which gives confidence that it reflects them.

A locally logged-in user who presses Ctrl-Alt-Del when at the console can reboot the system. If accidentally pressed, as could happen in the case of a mixed operating system environment, this can create the risk of short-term loss of systems' availability due to unintentional reboot.

Leaving the user list enabled is a security risk because it allows anyone with physical access to the system to enumerate known user accounts without authenticated access to the system.

This requirement applies to wireless peripheral technologies (e.g., wireless mice, keyboards, displays, etc.) used with RHEL 10 systems. Wireless peripherals (e.g., Wi-Fi/Bluetooth/IR keyboards, mice and pointing devices, and near field communications [NFC]) present a unique challenge by creating an open, unsecured port on a computer.

Wireless peripherals must meet DoW requirements for wireless data transmission and be approved for use by the authorizing official. Even though some wireless peripherals, such as mice and pointing devices, do not ordinarily carry information that must be protected, modification of communications with these wireless peripherals may be used to compromise the RHEL 10 operating system.

Satisfies: SRG-OS-000095-GPOS-00049, SRG-OS-000300-GPOS-00118

Automatically mounting file systems permits easy introduction of unknown devices, thereby facilitating malicious activity.

Satisfies: SRG-OS-000114-GPOS-00059, SRG-OS-000378-GPOS-00163

ExecShield uses the segmentation feature on all x86 systems to prevent execution in memory higher than a certain address. It writes an address as a limit in the code segment descriptor, to control where code can be executed, on a per-process basis. When the kernel places a process's memory regions such as the stack and heap higher than this address, the hardware prevents execution in that address range. This is enabled by default on the latest Red Hat and Fedora systems if supported by the hardware.

Terminating an idle SSH 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 SSH session will also free up resources committed by the managed network element.

Terminating network connections associated with communications sessions includes, for example, deallocating associated TCP/IP address/port pairs at the operating system level and deallocating 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 operating system terminates all sessions or network access; it only ends the inactive session and releases the resources associated with that session.

RHEL 10 uses "/etc/ssh/sshd_config" for configurations of OpenSSH. Within the "sshd_config", the product of the values of "ClientAliveInterval" and "ClientAliveCountMax" are used to establish the inactivity threshold.

The "ClientAliveInterval" is a timeout interval in seconds after which if no data has been received from the client, sshd will send a message through the encrypted channel to request a response from the client.

The "ClientAliveCountMax" is the number of client alive messages that may be sent without sshd receiving any messages back from the client. If this threshold is met, sshd will disconnect the client.

For more information on these settings and others, refer to the sshd_config man pages.

Satisfies: SRG-OS-000163-GPOS-00072, SRG-OS-000279-GPOS-00109, SRG-OS-000395-GPOS-00175

A locally logged-on user who presses Ctrl-Alt-Delete when at the console can reboot the system. If accidentally pressed, as could happen in the case of a mixed operating system environment, this can create the risk of short-term loss of availability of systems due to unintentional reboot.

In a graphical user environment, risk of unintentional reboot from the Ctrl-Alt-Delete sequence is reduced because the user will be prompted before any action is taken.

Using interactive or recovery boot, the console user could disable auditing, firewalls, or other services, weakening system security.

Poisoning writes an arbitrary value to freed pages, so any modification or reference to that page after being freed or before being initialized will be detected and prevented. This prevents many types of use-after-free vulnerabilities at little performance cost. It also prevents data leakage and detection of corrupted memory.

Kernel page-table isolation is a kernel feature that mitigates the Meltdown security vulnerability and hardens the kernel against attempts to bypass kernel address space layout randomization (KASLR).

Satisfies: SRG-OS-000433-GPOS-00193, SRG-OS-000095-GPOS-00049

Preventing unauthorized information transfers mitigates the risk of information, including encrypted representations of information, produced by the actions of prior users/roles (or the actions of processes acting on behalf of prior users/roles) from being available to any current users/roles (or current processes) that obtain access to shared system resources (e.g., registers, main memory, hard disks) after those resources have been released back to information systems. The control of information in shared resources is also commonly referred to as object reuse and residual information protection.

This requirement generally applies to the design of an information technology product, but it can also apply to the configuration of information system components that are, or use, such products. This can be verified by acceptance/validation processes in DoW or other government agencies.

There may be shared resources with configurable protections (e.g., files in storage) that may be assessed on specific information system components.

Setting the "kernel.perf_event_paranoid" kernel parameter to "2" prevents attackers from gaining additional system information as a nonprivileged user.

Satisfies: SRG-OS-000132-GPOS-00067, SRG-OS-000138-GPOS-00069

Exposing kernel pointers (through procfs or "seq_printf()") exposes kernel writable structures, which may contain functions pointers. If a write vulnerability occurs in the kernel, allowing write access to any of this structure, the kernel can be compromised. This option disallows any program without the CAP_SYSLOG capability to get the addresses of kernel pointers by replacing them with "0".

Satisfies: SRG-OS-000132-GPOS-00067, SRG-OS-000433-GPOS-00192

By enabling the "fs.protected_symlinks" kernel parameter, symbolic links are permitted to be followed only when outside a sticky world-writable directory, or when the user identifier (UID) of the link and follower match, or when the directory owner matches the symlink's owner. Disallowing such symlinks helps mitigate vulnerabilities based on insecure file systems accessed by privileged programs, avoiding an exploitation vector exploiting unsafe use of open() or creat().

Satisfies: SRG-OS-000312-GPOS-00122, SRG-OS-000312-GPOS-00123, SRG-OS-000324-GPOS-00125

Disabling CAN protects the system against exploitation of any flaws in its implementation.

It is detrimental for operating systems to provide, or install by default, functionality exceeding requirements or mission objectives. These unnecessary capabilities or services are often overlooked and therefore, may remain unsecured. They increase the risk to the platform by providing additional attack vectors.

Failing to disconnect unused protocols can result in a system compromise.

The TIPC is a protocol that is specially designed for intra-cluster communication. It can be configured to transmit messages either on User Datagram Protocol (UDP) or directly across Ethernet. Message delivery is sequence guaranteed, loss free, and flow controlled. Disabling TIPC protects the system against exploitation of any flaws in its implementation.

Unrestricted usage of ptrace allows compromised binaries to run ptrace on other processes of the user. The attacker can then steal sensitive information from the target processes (e.g., SSH sessions, web browser, etc.) without any additional assistance from the user (i.e., without resorting to phishing).

A core dump includes a memory image taken at the time the operating system terminates an application. The memory image could contain sensitive data and is generally useful only for developers or system operators trying to debug problems.

Enabling core dumps on production systems is not recommended; however, there may be overriding operational requirements to enable advanced debugging. Permitting temporary enablement of core dumps during such situations must be reviewed through local needs and policy.

A core dump includes a memory image taken at the time the operating system terminates an application. The memory image could contain sensitive data and is generally useful only for developers trying to debug problems.

Kernel core dumps may contain the full contents of system memory at the time of the crash. Kernel core dumps consume a considerable amount of disk space and may result in denial of service by exhausting the available space on the target file system partition. Unless the system is used for kernel development or testing, there is little need to run the kdump service.

Without the use of multifactor authentication, the ease of access to privileged functions is greatly increased. Multifactor authentication requires using two or more factors to achieve authentication. A privileged account is defined as an information system account with authorizations of a privileged user. The DoW Common Access Card (CAC) with DoW-approved public key infrastructure (PKI) is an example of multifactor authentication.

Satisfies: SRG-OS-000375-GPOS-00160, SRG-OS-000105-GPOS-00052, SRG-OS-000106-GPOS-00053, SRG-OS-000107-GPOS-00054, SRG-OS-000108-GPOS-00055

If the private key is discovered, an attacker can use the key to authenticate as an authorized user and gain access to the network infrastructure.

The cornerstone of the PKI is the private key used to encrypt or digitally sign information.

If the private key is stolen, this will lead to the compromise of the authentication and nonrepudiation gained through PKI because the attacker can use the private key to digitally sign documents and pretend to be the authorized user.

Both the holders of a digital certificate and the issuing authority must protect the computers, storage devices, or whatever they use to keep the private keys.

To mitigate the risk of unauthorized access to sensitive information by entities that have been issued certificates by DoW-approved PKIs, all DoW systems (e.g., web servers and web portals) must be properly configured to incorporate access control methods that do not rely solely on the possession of a certificate for access.

Successful authentication must not automatically give an entity access to an asset or security boundary. Authorization procedures and controls must be implemented to ensure each authenticated entity also has a validated and current authorization. Authorization is the process of determining whether an entity, once authenticated, is permitted to access a specific asset. Information systems use access control policies and enforcement mechanisms to implement this requirement.

This requirement prevents attackers with physical access from trivially bypassing security on the machine and gaining root access. Such accesses are further prevented by configuring the bootloader password.

Without mapping the certificate used to authenticate to the user account, the ability to determine the identity of the individual user or group will not be available for forensic analysis.

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 or restrict unused or unnecessary physical and logical ports/protocols on information systems.

Operating systems 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., VPN and IPS); however, doing so increases risk over limiting the services provided by one component.

To support the requirements and principles of least functionality, the operating system 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 to conduct official business.

Satisfies: SRG-OS-000096-GPOS-00050, SRG-OS-000297-GPOS-00115

Network interfaces in promiscuous mode allow for the capture of all network traffic visible to the system. If unauthorized individuals can access these applications, it may allow them to collect information such as login IDs, passwords, and key exchanges between systems.

If the system is being used to perform a network troubleshooting function, the use of these tools must be documented with the information systems security officer (ISSO) and restricted to authorized personnel only.

Inaccurate time stamps make it more difficult to correlate events and can lead to an inaccurate analysis. Determining the correct time a particular event occurred on a system is critical when conducting forensic analysis and investigating system events. Sources outside the configured acceptable allowance (drift) may be inaccurate.

Synchronizing internal information system clocks provides uniformity of time stamps for information systems with multiple system clocks and systems connected over a network.

Depending on the infrastructure being used, the "pool" directive may not be supported.

Authoritative time sources include the United States Naval Observatory (USNO) time servers, a time server designated for the appropriate DoW network (NIPRNet/SIPRNet), and/or the Global Positioning System (GPS).

Satisfies: SRG-OS-000355-GPOS-00143, SRG-OS-000356-GPOS-00144, SRG-OS-000359-GPOS-00146, SRG-OS-000785-GPOS-00250

To provide availability for name resolution services, multiple redundant name servers are mandated. A failure in name resolution could lead to the failure of security functions requiring name resolution, which may include time synchronization, centralized authentication, and remote system logging.

Denial of service (DoS) is a condition when a resource is not available for legitimate users. When this occurs, the organization either cannot accomplish its mission or must operate at degraded capacity.

Managing excess capacity ensures that sufficient capacity is available to counter flooding attacks. Employing increased capacity and service redundancy may reduce the susceptibility to some DoS attacks. Managing excess capacity may include, for example, establishing selected usage priorities, quotas, or partitioning.

Satisfies: SRG-OS-000420-GPOS-00186, SRG-OS-000142-GPOS-00071

Source-routed packets allow the source of the packet to suggest that routers forward the packet along a different path than configured on the router, which can be used to bypass network security measures. This requirement applies only to the forwarding of source-routed traffic, such as when IPv4 forwarding is enabled and the system is functioning as a router.

Accepting source-routed packets in the IPv4 protocol has few legitimate uses. It must be disabled unless it is absolutely required.

Satisfies: SRG-OS-000420-GPOS-00186, SRG-OS-000142-GPOS-00073

The presence of "martian" packets (which have impossible addresses) as well as spoofed packets, source-routed packets, and redirects, could be a sign of nefarious network activity. Logging these packets enables this activity to be detected.

Satisfies: SRG-OS-000420-GPOS-00186, SRG-OS-000142-GPOS-00075

ICMP redirect messages are used by routers to inform hosts that a more direct route exists for a particular destination. These messages modify the host's route table and are unauthenticated. An illicit ICMP redirect message could result in a man-in-the-middle attack.

This feature of the IPv4 protocol has few legitimate uses. It must be disabled unless absolutely required.

Satisfies: SRG-OS-000420-GPOS-00186, SRG-OS-000142-GPOS-00077

Enabling reverse path filtering drops packets with source addresses that should not have been able to be received on the interface on which they were received. It must not be used on systems that are routers for complicated networks but is helpful for end hosts and routers serving small networks.

Satisfies: SRG-OS-000420-GPOS-00186, SRG-OS-000142-GPOS-00079

Some routers will send responses to broadcast frames that violate RFC-1122, which fills up a log file system with many useless error messages. An attacker may take advantage of this and attempt to flood the logs with bogus error logs. Ignoring bogus ICMP error responses reduces log size, although some activity would not be logged.

Satisfies: SRG-OS-000420-GPOS-00186, SRG-OS-000142-GPOS-00081

ICMP redirect messages are used by routers to inform hosts that a more direct route exists for a particular destination. These messages contain information from the system's route table, possibly revealing portions of the network topology.

The ability to send ICMP redirects is only appropriate for systems acting as routers.

Satisfies: SRG-OS-000420-GPOS-00186, SRG-OS-000142-GPOS-00083

An illicit router advertisement message could result in a man-in-the-middle attack.

Satisfies: SRG-OS-000420-GPOS-00186, SRG-OS-000142-GPOS-00085

Source-routed packets allow the source of the packet to suggest that routers forward the packet along a different path than configured on the router, which can be used to bypass network security measures. This requirement applies only to the forwarding of source-routed traffic, such as when forwarding is enabled and the system is functioning as a router.

Satisfies: SRG-OS-000420-GPOS-00186, SRG-OS-000142-GPOS-00087

An illicit router advertisement message could result in a man-in-the-middle attack.

Satisfies: SRG-OS-000420-GPOS-00186, SRG-OS-000142-GPOS-00089

Source-routed packets allow the source of the packet to suggest that routers forward the packet along a different path than configured on the router, which can be used to bypass network security measures. This requirement applies only to the forwarding of source-routed traffic, such as when forwarding is enabled and the system is functioning as a router.

Accepting source-routed packets in the IPv6 protocol has few legitimate uses. It must be disabled unless it is absolutely required.

Satisfies: SRG-OS-000420-GPOS-00186, SRG-OS-000142-GPOS-00091

To ensure that DNS resolver settings are respected, a DNS mode in Network Manager must be configured. The following are common DNS values in "NetworkManager.conf [main]":

- default: NetworkManager will update "/etc/resolv.conf" to reflect the nameservers provided by currently active connections.
- none: NetworkManager will not modify "/etc/resolv.conf". Used when DNS is managed manually or by another service.
- systemd-resolved: Uses "systemd-resolved" to manage DNS.
- dnsmasq: Enables the internal "dnsmasq" plugin.

Satisfies: SRG-OS-000420-GPOS-00186, SRG-OS-000142-GPOS-00091

Without the capability to restrict the roles and individuals that can select which events are audited, unauthorized personnel may be able to prevent the auditing of critical events. Misconfigured audits may degrade the system's performance by overwhelming the audit log. Misconfigured audits may also make it more difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

An operating system release is considered "supported" if the vendor continues to provide security patches for the product. With an unsupported release, it will not be possible to resolve security issues discovered in the system software.

Red Hat offers the Extended Update Support (EUS) add-on to a Red Hat Enterprise Linux subscription, for a fee, for customers who wish to standardize on a specific minor release for an extended period.

End-of-life dates for Red Hat Linux 10 releases are as follows:
- Current end of Full Support for Red Hat Linux 10 is 31 May 2030.
- Current end of Maintenance Support for Red Hat Linux 10 is 31 May 2035.
- Current end of Extended Life Cycle Support (ELS) for Red Hat Linux 9 is 31 May 2038.

Without generating audit record specific to the security and mission needs of the organization, it would be difficult to establish, correlate, and investigate the events relating to an incident or identify those responsible for one.

Audit records can be generated from various components within the information system (e.g., module or policy filter).

When a user logs on, the auid is set to the uid of the account being authenticated. Daemons are not user sessions and have the loginuid set to -1. The auid representation is an unsigned 32-bit integer, which equals 4294967295. The audit system interprets -1, 4294967295, and "unset" in the same way.

The system call rules are loaded into a matching engine that intercepts each system call made by all programs on the system. Therefore, it is very important to use system call rules only when absolutely necessary because these affect performance. More rules lead to poorer performance. The performance can be helped, however, by combining system calls into one rule whenever possible.

Satisfies: SRG-OS-000037-GPOS-00015, SRG-OS-000042-GPOS-00020, SRG-OS-000062-GPOS-00031, SRG-OS-000392-GPOS-00172, SRG-OS-000462-GPOS-00206, SRG-OS-000471-GPOS-00215, SRG-OS-000466-GPOS-00210