Guide to the Secure Configuration of SUSE Linux Enterprise 15
Rules, Groups, and Values defined within the XCCDF Benchmark
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Inspect and Activate Default Rules
View the currently-enforced <code>iptables</code> rules by running the command: <pre>$ sudo iptables -nL --line-numbers</pre> The command is analogous for <code>ip6tables</code>. <br> <br> ...Group -
Ensure IPv6 is disabled through kernel boot parameter
To disable IPv6 protocol support in the Linux kernel, add the argument <code>ipv6.disable=1</code> to the default GRUB2 command line for the Linux operating system. Configure the default Grub2 kern...Rule Low Severity -
Configure Accepting Router Advertisements on All IPv6 Interfaces
To set the runtime status of the <code>net.ipv6.conf.all.accept_ra</code> kernel parameter, run the following command: <pre>$ sudo sysctl -w net.ipv6.conf.all.accept_ra=0</pre> To make sure that th...Rule Medium Severity -
Configure Accepting Default Router in Router Advertisements on All IPv6 Interfaces
To set the runtime status of the <code>net.ipv6.conf.all.accept_ra_defrtr</code> kernel parameter, run the following command: <pre>$ sudo sysctl -w net.ipv6.conf.all.accept_ra_defrtr=0</pre> To mak...Rule Unknown Severity -
Configure Denying Router Solicitations on All IPv6 Interfaces
To set the runtime status of the <code>net.ipv6.conf.all.router_solicitations</code> kernel parameter, run the following command: <pre>$ sudo sysctl -w net.ipv6.conf.all.router_solicitations=0</pre...Rule Unknown Severity -
Disable Kernel Parameter for Accepting Source-Routed Packets on IPv6 Interfaces by Default
To set the runtime status of the <code>net.ipv6.conf.default.accept_source_route</code> kernel parameter, run the following command: <pre>$ sudo sysctl -w net.ipv6.conf.default.accept_source_route=...Rule Medium Severity -
Configure Denying Router Solicitations on All IPv6 Interfaces By Default
To set the runtime status of the <code>net.ipv6.conf.default.router_solicitations</code> kernel parameter, run the following command: <pre>$ sudo sysctl -w net.ipv6.conf.default.router_solicitation...Rule Unknown Severity -
Disable Accepting Packets Routed Between Local Interfaces
To set the runtime status of the <code>net.ipv4.conf.all.accept_local</code> kernel parameter, run the following command: <pre>$ sudo sysctl -w net.ipv4.conf.all.accept_local=0</pre> To make sure t...Rule Medium Severity -
Verify User Who Owns /etc/nftables Directory
To properly set the owner of/etc/nftables, run the command:$ sudo chown root /etc/nftables
Rule Medium Severity -
Disable Kernel Parameter for Accepting Source-Routed Packets on all IPv4 Interfaces
To set the runtime status of the <code>net.ipv4.conf.all.accept_source_route</code> kernel parameter, run the following command: <pre>$ sudo sysctl -w net.ipv4.conf.all.accept_source_route=0</pre> ...Rule Medium Severity -
Enable Kernel Parameter to Log Martian Packets on all IPv4 Interfaces
To set the runtime status of the <code>net.ipv4.conf.all.log_martians</code> kernel parameter, run the following command: <pre>$ sudo sysctl -w net.ipv4.conf.all.log_martians=1</pre> To make sure t...Rule Unknown Severity -
Prevent Routing External Traffic to Local Loopback on All IPv4 Interfaces
To set the runtime status of the <code>net.ipv4.conf.all.route_localnet</code> kernel parameter, run the following command: <pre>$ sudo sysctl -w net.ipv4.conf.all.route_localnet=0</pre> To make su...Rule Medium Severity -
Enable Kernel Parameter to Use Reverse Path Filtering on all IPv4 Interfaces by Default
To set the runtime status of the <code>net.ipv4.conf.default.rp_filter</code> kernel parameter, run the following command: <pre>$ sudo sysctl -w net.ipv4.conf.default.rp_filter=1</pre> To make sure...Rule Medium Severity -
Configure Kernel to Rate Limit Sending of Duplicate TCP Acknowledgments
Make sure that the system is configured to limit the maximal rate for sending duplicate acknowledgments in response to incoming TCP packets that are for an existing connection but that are invalid ...Rule Medium 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 -
Install nftables Package
nftables provides a new in-kernel packet classification framework that is based on a network-specific Virtual Machine (VM) and a new nft userspace command line tool. nftables reuses the existing Ne...Rule Medium Severity -
Wireless Networking
Wireless networking, such as 802.11 (WiFi) and Bluetooth, can present a security risk to sensitive or classified systems and networks. Wireless networking hardware is much more likely to be include...Group -
Deactivate Wireless Network Interfaces
Deactivating wireless network interfaces should prevent normal usage of the wireless capability. <br> <br> Configure the system to disable wireless network interfaces by issuing the follo...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 that system commands directories have root as a group owner
System commands are stored in the following directories: by default: <pre>/bin /sbin /usr/bin /usr/sbin /usr/local/bin /usr/local/sbin </pre> All these directories should have <code>root</code...Rule Medium Severity -
Verify Group Who Owns /etc/crypttab File
To properly set the group owner of/etc/crypttab, run the command:$ sudo chgrp root /etc/crypttab
Rule Medium Severity -
Verify Group Who Owns System.map Files
The System.map files are symbol map files generated during the compilation of the Linux kernel. They contain the mapping between kernel symbols and their corresponding memory addresses. These files...Rule Low Severity -
Verify User Who Owns /etc/crypttab File
To properly set the owner of/etc/crypttab, run the command:$ sudo chown root /etc/crypttab
Rule Medium Severity -
Verify User Who Owns System.map Files
The System.map files are symbol map files generated during the compilation of the Linux kernel. They contain the mapping between kernel symbols and their corresponding memory addresses. These files...Rule Low Severity -
Ensure All Files Are Owned by a User
If any files are not owned by a user, then the cause of their lack of ownership should be investigated. Following this, the files should be deleted or assigned to an appropriate user. Locate the m...Rule Medium Severity -
Verify Group Who Owns Backup passwd File
To properly set the group owner of/etc/passwd-, run the command:$ sudo chgrp root /etc/passwd-
Rule Medium Severity -
Verify Group Who Owns /etc/shells File
To properly set the group owner of/etc/shells, run the command:$ sudo chgrp root /etc/shells
Rule Medium Severity -
Verify User Who Owns Backup group File
To properly set the owner of/etc/group-, run the command:$ sudo chown root /etc/group-
Rule Medium Severity -
Verify Who Owns /etc/shells File
To properly set the owner of/etc/shells, run the command:$ sudo chown root /etc/shells
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 /etc/shells File
To properly set the permissions of/etc/shells, run the command:$ sudo chmod 0644 /etc/shells
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 -
Verify that Shared Library Directories Have Root Group Ownership
System-wide shared library files, which are linked to executables during process load time or run time, are stored in the following directories by default: <pre>/lib /lib64 /usr/lib /usr/lib64 </pr...Rule Medium Severity -
Verify that Shared Library Directories Have Root Ownership
System-wide shared library files, which are linked to executables during process load time or run time, are stored in the following directories by default: <pre>/lib /lib64 /usr/lib /usr/lib64 </pr...Rule Medium Severity -
Verify Group Who Owns /etc/sysctl.d Directory
To properly set the group owner of/etc/sysctl.d, run the command:$ sudo chgrp root /etc/sysctl.d
Rule Medium Severity -
Verify the system-wide library files in directories "/lib", "/lib64", "/usr/lib/" and "/usr/lib64" are group-owned by root.
System-wide library files are stored in the following directories by default: <pre>/lib /lib64 /usr/lib /usr/lib64 </pre> All system-wide shared library files should be protected from unauthorised ...Rule Medium Severity -
Disable Mounting of cramfs
To configure the system to prevent the <code>cramfs</code> kernel module from being loaded, add the following line to the file <code>/etc/modprobe.d/cramfs.conf</code>: <pre>install cramfs /bin/fa...Rule Low Severity -
Disable Mounting of udf
To configure the system to prevent the <code>udf</code> kernel module from being loaded, add the following line to the file <code>/etc/modprobe.d/udf.conf</code>: <pre>install udf /bin/false</pre>...Rule Low Severity -
Add noexec Option to /boot
The <code>noexec</code> mount option can be used to prevent binaries from being executed out of <code>/boot</code>. Add the <code>noexec</code> option to the fourth column of <code>/etc/fstab</code...Rule Medium Severity -
Verify that local /var/log/messages is not world-readable
Files containing sensitive informations should be protected by restrictive permissions. Most of the time, there is no need that these files need to be read by any non-root user To properly set the...Rule Medium Severity -
Restrict Access to Kernel Message Buffer
To set the runtime status of the <code>kernel.dmesg_restrict</code> kernel parameter, run the following command: <pre>$ sudo sysctl -w kernel.dmesg_restrict=1</pre> To make sure that the setting is...Rule Low Severity -
Disable loading and unloading of kernel modules
To set the runtime status of the <code>kernel.modules_disabled</code> kernel parameter, run the following command: <pre>$ sudo sysctl -w kernel.modules_disabled=1</pre> To make sure that the settin...Rule Medium Severity -
Prevent applications from mapping low portion of virtual memory
To set the runtime status of the <code>vm.mmap_min_addr</code> kernel parameter, run the following command: <pre>$ sudo sysctl -w vm.mmap_min_addr=65536</pre> To make sure that the setting is persi...Rule Medium Severity -
Configure the deny_execmem SELinux Boolean
By default, the SELinux boolean <code>deny_execmem</code> is disabled. This setting should be configured to <xccdf-1.2:sub idref="xccdf_org.ssgproject.content_value_var_deny_execmem" use="legacy"><...Rule Medium Severity -
Disable Core Dumps
A core dump file is the memory image of an executable program when it was terminated by the operating system due to errant behavior. In most cases, only software developers legitimately need to acc...Group -
Restrict Exposed Kernel Pointer Addresses Access
To set the runtime status of the <code>kernel.kptr_restrict</code> kernel parameter, run the following command: <pre>$ sudo sysctl -w kernel.kptr_restrict=<xccdf-1.2:sub idref="xccdf_org.ssgproject...Rule Medium Severity -
Uninstall mcstrans Package
The <code>mcstransd</code> daemon provides category label information to client processes requesting information. The label translations are defined in <code>/etc/selinux/targeted/setrans.conf</cod...Rule Low Severity -
Verify Group Who Owns /etc/selinux Directory
To properly set the group owner of/etc/selinux, run the command:$ sudo chgrp root /etc/selinux
Rule Medium Severity -
Verify User Who Owns /etc/selinux Directory
To properly set the owner of/etc/selinux, run the command:$ sudo chown root /etc/selinux
Rule Medium Severity -
Verify Permissions On /etc/selinux Directory
To properly set the permissions of/etc/selinux, run the command:$ sudo chmod 0755 /etc/selinux
Rule Medium Severity
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