Guide to the Secure Configuration of Alibaba Cloud Linux 2
Rules, Groups, and Values defined within the XCCDF Benchmark
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Set SSH MaxSessions limit
The <code>MaxSessions</code> parameter specifies the maximum number of open sessions permitted from a given connection. To set MaxSessions edit <code>/etc/ssh/sshd_config</code> as follows: <pre>Ma...Rule Medium Severity -
Ensure SSH MaxStartups is configured
The MaxStartups parameter specifies the maximum number of concurrent unauthenticated connections to the SSH daemon. Additional connections will be dropped until authentication succeeds or the Login...Rule Medium Severity -
Use Only FIPS 140-2 Validated Ciphers
Limit the ciphers to those algorithms which are FIPS-approved. Counter (CTR) mode is also preferred over cipher-block chaining (CBC) mode. The following line in <code>/etc/ssh/sshd_config</code> de...Rule Medium Severity -
Use Only FIPS 140-2 Validated MACs
Limit the MACs to those hash algorithms which are FIPS-approved. The following line in <code>/etc/ssh/sshd_config</code> demonstrates use of FIPS-approved MACs: <pre>MACs hmac-sha2-512,hmac-sha2-2...Rule Medium Severity -
X Window System
The X Window System implementation included with the system is called X.org.Group -
Disable X Windows
Unless there is a mission-critical reason for the system to run a graphical user interface, ensure X is not set to start automatically at boot and remove the X Windows software packages. There is u...Group -
Remove the X Windows Package Group
By removing the xorg-x11-server-common package, the system no longer has X Windows installed. If X Windows is not installed then the system cannot boot into graphical user mode. This prevents the s...Rule Medium Severity -
Verify and Correct File Permissions with RPM
The RPM package management system can check file access permissions of installed software packages, including many that are important to system security. Verify that the file permissions of system ...Rule High Severity -
Ensure /dev/shm is configured
The <code>/dev/shm</code> is a traditional shared memory concept. One program will create a memory portion, which other processes (if permitted) can access. If <code>/dev/shm</code> is not configur...Rule Low Severity -
Ensure PAM Displays Last Logon/Access Notification
To configure the system to notify users of last logon/access using <code>pam_lastlog</code>, add or correct the <code>pam_lastlog</code> settings in <code>/etc/pam.d/postlogin</code> to include <co...Rule Low Severity -
Restrict unprivileged access to the kernel syslog
Enforce restrictions on unprivileged users reading the kernel syslog via dmesg(8). The configuration that was used to build kernel is available at <code>/boot/config-*</code>. To check the con...Rule Medium Severity -
Disable mutable hooks
Ensure kernel structures associated with LSMs are always mapped as read-only after system boot. The configuration that was used to build kernel is available at <code>/boot/config-*</code>. To ...Rule Medium Severity -
Type of hostname to record the audit event
Type of hostname to record the audit eventValue -
Ensure Log Files Are Owned By Appropriate Group
The group-owner of all log files written by <code>rsyslog</code> should be <code>root</code>. These log files are determined by the second part of each Rule line in <code>/etc/rsyslog.conf</code> a...Rule Medium Severity -
Ensure No World-Writable Files Exist
It is generally a good idea to remove global (other) write access to a file when it is discovered. However, check with documentation for specific applications before making changes. Also, monitor f...Rule Medium Severity -
Ensure All Files Are Owned by a Group
If any file is not group-owned by a group present in /etc/group, the cause of the lack of group-ownership must be investigated. Following this, those files should be deleted or assigned to an appro...Rule Medium Severity -
Verify Permissions on group File
To properly set the permissions of/etc/group, run the command:$ sudo chmod 0644 /etc/group
Rule Medium Severity -
Verify Permissions on passwd File
To properly set the permissions of/etc/passwd, run the command:$ sudo chmod 0644 /etc/passwd
Rule Medium Severity -
Verify Permissions on /var/log/syslog File
To properly set the permissions of/var/log/syslog, run the command:$ sudo chmod 0640 /var/log/syslog
Rule Medium Severity -
Updating Software
The <code>yum</code> command line tool is used to install and update software packages. The system also provides a graphical software update tool in the <b>System</b> menu, in the <b>Administration...Group -
Verify that System Executable Have Root Ownership
<pre>/bin /sbin /usr/bin /usr/sbin /usr/local/bin /usr/local/sbin</pre> All these directories should be owned by the <code>root</code> user. If any directory <i>DIR</i> in these directories is foun...Rule Medium Severity -
Ensure SELinux is Not Disabled
The SELinux state should be set to <code>enforcing</code> or <code>permissive</code> at system boot time. In the file <code>/etc/selinux/config</code>, add or correct the following line to configur...Rule High Severity -
Configure System to Forward All Mail through a specific host
Set up a relay host that will act as a gateway for all outbound email. Edit the file <code>/etc/postfix/main.cf</code> to ensure that only the following <code>relayhost</code> line appears: <pre>re...Rule Medium Severity -
SSH is required to be installed
Specify if the Policy requires SSH to be installed. Used by SSH Rules to determine if SSH should be uninstalled or configured.<br> A value of 0 means that the policy doesn't care if OpenSSH server ...Value -
Verify Permissions on SSH Server config file
To properly set the permissions of/etc/ssh/sshd_config, run the command:$ sudo chmod 0600 /etc/ssh/sshd_config
Rule Medium Severity -
Set SSH Client Alive Interval
SSH allows administrators to set a network responsiveness timeout interval. After this interval has passed, the unresponsive client will be automatically logged out. <br> <br> To set this t...Rule Medium Severity -
Disable Compression Or Set Compression to delayed
Compression is useful for slow network connections over long distances but can cause performance issues on local LANs. If use of compression is required, it should be enabled only after a user has ...Rule Medium Severity -
Software Integrity Checking
Both the AIDE (Advanced Intrusion Detection Environment) software and the RPM package management system provide mechanisms for verifying the integrity of installed software. AIDE uses snapshots of ...Group -
Verify File Hashes with RPM
Without cryptographic integrity protections, system executables and files can be altered by unauthorized users without detection. The RPM package management system can check the hashes of installed...Rule High Severity -
Verify Integrity with AIDE
AIDE conducts integrity checks by comparing information about files with previously-gathered information. Ideally, the AIDE database is created immediately after initial system configuration, and t...Group -
Configure Periodic Execution of AIDE
At a minimum, AIDE should be configured to run a weekly scan. To implement a daily execution of AIDE at 4:05am using cron, add the following line to <code>/etc/crontab</code>: <pre>05 4 * * * root ...Rule Medium Severity -
Configure BIND to use System Crypto Policy
Crypto Policies provide a centralized control over crypto algorithms usage of many packages. BIND is supported by crypto policy, but the BIND configuration may be set up to ignore it. To check tha...Rule High Severity -
Configure System Cryptography Policy
To configure the system cryptography policy to use ciphers only from the <code><xccdf-1.2:sub idref="xccdf_org.ssgproject.content_value_var_system_crypto_policy" use="legacy"></xccdf-1.2:sub></code...Rule High Severity -
Disk Partitioning
To ensure separation and protection of data, there are top-level system directories which should be placed on their own physical partition or logical volume. The installer's default partitioning sc...Group -
GNOME Desktop Environment
GNOME is a graphical desktop environment bundled with many Linux distributions that allow users to easily interact with the operating system graphically rather than textually. The GNOME Graphical D...Group -
Configure GNOME Login Screen
In the default GNOME desktop, the login is displayed after system boot and can display user accounts, allow users to reboot the system, and allow users to login automatically and/or with a guest ac...Group -
Configure GNOME Screen Locking
In the default GNOME3 desktop, the screen can be locked by selecting the user name in the far right corner of the main panel and selecting <b>Lock</b>. <br> <br> The following sections deta...Group -
Ensure Users Re-Authenticate for Privilege Escalation - sudo !authenticate
The sudo <code>!authenticate</code> option, when specified, allows a user to execute commands using sudo without having to authenticate. This should be disabled by making sure that the <code>!authe...Rule Medium Severity -
Explicit arguments in sudo specifications
All commands in the sudoers file must strictly specify the arguments allowed to be used for a given user. If the command is supposed to be executed only without arguments, pass "" as an argument in...Rule Medium Severity -
Ensure SMEP is not disabled during boot
The SMEP is used to prevent the supervisor mode from executing user space code, it is enabled by default since Linux kernel 3.0. But it could be disabled through kernel boot parameters. Ensure tha...Rule Medium Severity -
Ensure gpgcheck Enabled In Main yum Configuration
The <code>gpgcheck</code> option controls whether RPM packages' signatures are always checked prior to installation. To configure yum to check package signatures before installing them, ensure the ...Rule High Severity -
Protect Accounts by Configuring PAM
PAM, or Pluggable Authentication Modules, is a system which implements modular authentication for Linux programs. PAM provides a flexible and configurable architecture for authentication, and it sh...Group -
Password Hashing algorithm for pam_unix.so
Specify the system default encryption algorithm for encrypting passwords. Defines the hashing algorithm to be used in pam_unix.so.Value -
Limit Password Reuse: password-auth
Do not allow users to reuse recent passwords. This can be accomplished by using the <code>remember</code> option for the <code>pam_pwhistory</code> PAM module. <br> <br> On systems with n...Rule Medium Severity -
Ensure PAM Enforces Password Requirements - Minimum Digit Characters
The pam_pwquality module's <code>dcredit</code> parameter controls requirements for usage of digits in a password. When set to a negative number, any password will be required to contain that many ...Rule Medium Severity -
Ensure PAM Enforces Password Requirements - Minimum Uppercase Characters
The pam_pwquality module's <code>ucredit=</code> parameter controls requirements for usage of uppercase letters in a password. When set to a negative number, any password will be required to contai...Rule Medium Severity -
Set PAM''s Password Hashing Algorithm
The PAM system service can be configured to only store encrypted representations of passwords. In "/etc/pam.d/system-auth", the <code>password</code> section of the file controls which PAM modules ...Rule Medium Severity -
Set Account Expiration Parameters
Accounts can be configured to be automatically disabled after a certain time period, meaning that they will require administrator interaction to become usable again. Expiration of accounts after in...Group -
Set Account Expiration Following Inactivity
To specify the number of days after a password expires (which signifies inactivity) until an account is permanently disabled, add or correct the following line in <code>/etc/default/useradd</code>:...Rule Medium Severity -
Set Password Expiration Parameters
The file <code>/etc/login.defs</code> controls several password-related settings. Programs such as <code>passwd</code>, <code>su</code>, and <code>login</code> consult <code>/etc/login.defs</code> ...Group
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