Guide to the Secure Configuration of Alibaba Cloud Linux 3
Rules, Groups, and Values defined within the XCCDF Benchmark
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Enable GSSAPI Authentication
Sites setup to use Kerberos or other GSSAPI Authenticaion require setting sshd to accept this authentication. To enable GSSAPI authentication, add or correct the following line in <code>/etc/ssh/...Rule Medium Severity -
Enable PAM
UsePAM Enables the Pluggable Authentication Module interface. If set to “yes” this will enable PAM authentication using ChallengeResponseAuthentication and PasswordAuthentication in addition to PAM...Rule Medium Severity -
Enable Use of Strict Mode Checking
SSHs <code>StrictModes</code> option checks file and ownership permissions in the user's home directory <code>.ssh</code> folder before accepting login. If world- writable permissions are found, lo...Rule Medium Severity -
Enable SSH Warning Banner
To enable the warning banner and ensure it is consistent across the system, add or correct the following line in <code>/etc/ssh/sshd_config</code>: <pre>Banner /etc/issue.net</pre> Another sectio...Rule Medium Severity -
Enable Encrypted X11 Forwarding
By default, remote X11 connections are not encrypted when initiated by users. SSH has the capability to encrypt remote X11 connections when SSH's <code>X11Forwarding</code> option is enabled. <br> ...Rule High Severity -
Limit Users' SSH Access
By default, the SSH configuration allows any user with an account to access the system. There are several options available to limit which users and group can access the system via SSH. It is recom...Rule Unknown Severity -
Enable SSH Print Last Log
Ensure that SSH will display the date and time of the last successful account logon. <br> The default SSH configuration enables print of the date and time of the last login. The appropriate configu...Rule Medium Severity -
Force frequent session key renegotiation
The <code>RekeyLimit</code> parameter specifies how often the session key of the is renegotiated, both in terms of amount of data that may be transmitted and the time elapsed.<br> To decrease the d...Rule Medium Severity -
Ensure SSH LoginGraceTime is configured
The <code>LoginGraceTime</code> parameter to the SSH server specifies the time allowed for successful authentication to the SSH server. The longer the Grace period is the more open unauthenticated ...Rule Medium Severity -
Set SSH Daemon LogLevel to VERBOSE
The <code>VERBOSE</code> parameter configures the SSH daemon to record login and logout activity. To specify the log level in SSH, add or correct the following line in <code>/etc/ssh/sshd_config<...Rule Medium Severity -
Set SSH authentication attempt limit
The <code>MaxAuthTries</code> parameter specifies the maximum number of authentication attempts permitted per connection. Once the number of failures reaches half this value, additional failures ar...Rule Medium Severity -
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 -
Enable Use of Privilege Separation
When enabled, SSH will create an unprivileged child process that has the privilege of the authenticated user. To enable privilege separation in SSH, add or correct the following line in the <code>/...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 -
Verify and Correct Ownership with RPM
The RPM package management system can check file ownership permissions of installed software packages, including many that are important to system security. After locating a file with incorrect per...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 -
Set Interactive Session Timeout
Setting the <code>TMOUT</code> option in <code>/etc/profile</code> ensures that all user sessions will terminate based on inactivity. The value of TMOUT should be exported and read only. The <code>...Rule Medium 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 -
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 -
Verify that All World-Writable Directories Have Sticky Bits Set
When the so-called 'sticky bit' is set on a directory, only the owner of a given file may remove that file from the directory. Without the sticky bit, any user with write access to a directory may ...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 -
Action for auditd to take when disk errors
'The setting for disk_error_action in /etc/audit/auditd.conf, if multiple values are allowed write them separated by pipes as in "syslog|single|halt", for remediations the first value will be taken'Value -
Number of log files for auditd to retain
The setting for num_logs in /etc/audit/auditd.confValue -
Size remaining in disk space before prompting space_left_action
The setting for space_left (MB) in /etc/audit/auditd.confValue -
Action for auditd to take when disk space just starts to run low
The setting for space_left_action in /etc/audit/auditd.confValue -
Verify nftables Service is Disabled
nftables is a subsystem of the Linux kernel providing filtering and classification of network packets/datagrams/frames and is the successor to iptables. The <code>nftables</code> service can be dis...Rule Medium Severity -
Disable DCCP Support
The Datagram Congestion Control Protocol (DCCP) is a relatively new transport layer protocol, designed to support streaming media and telephony. To configure the system to prevent the <code>dccp</...Rule Medium Severity -
Appropriate Action Must be Setup When the Internal Audit Event Queue is Full
The audit system should have an action setup in the event the internal event queue becomes full. To setup an overflow action edit <code>/etc/audit/auditd.conf</code>. Set <code>overflow_action</cod...Rule Medium Severity -
Write Audit Logs to the Disk
To configure Audit daemon to write Audit logs to the disk, setwrite_logs
toyes
in/etc/audit/auditd.conf
. This is the default setting.Rule Medium Severity -
DHCP
The Dynamic Host Configuration Protocol (DHCP) allows systems to request and obtain an IP address and other configuration parameters from a server. <br> <br> This guide recommends configuring...Group -
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 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 -
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 GNOME3 DConf User Profile
By default, DConf provides a standard user profile. This profile contains a list of DConf configuration databases. The user profile and database always take the highest priority. As such the DConf ...Rule High Severity -
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 -
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 -
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 -
Enable Kernel Parameter to Use TCP Syncookies on Network Interfaces
To set the runtime status of the <code>net.ipv4.tcp_syncookies</code> kernel parameter, run the following command: <pre>$ sudo sysctl -w net.ipv4.tcp_syncookies=1</pre> To make sure that the settin...Rule Medium 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
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