Guide to the Secure Configuration of Debian 10
Rules, Groups, and Values defined within the XCCDF Benchmark
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Enable seccomp to safely compute untrusted bytecode
This kernel feature is useful for number crunching applications that may need to compute untrusted bytecode during their execution. By using pipes ...Rule Medium Severity -
Enable use of Berkeley Packet Filter with seccomp
Enable tasks to build secure computing environments defined in terms of Berkeley Packet Filter programs which implement task-defined system call fi...Rule Medium Severity -
Enable different security models
This allows you to choose different security modules to be configured into your kernel. The configuration that was used to build kernel is availab...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...Rule Medium Severity -
Enable Yama support
This enables support for LSM module Yama, which extends DAC support with additional system-wide security settings beyond regular Linux discretionar...Rule Medium Severity -
Enable SLUB debugging support
SLUB has extensive debug support features and this allows the allocator validation checking to be enabled. The configuration that was used to buil...Rule Medium Severity -
Enable TCP/IP syncookie support
Normal TCP/IP networking is open to an attack known as SYN flooding. It is denial-of-service attack that prevents legitimate remote users from bein...Rule Medium Severity -
Unmap kernel when running in userspace (aka KAISER)
Speculation attacks against some high-performance processors can be used to bypass MMU permission checks and leak kernel data to userspace. This ca...Rule Medium Severity -
Disable x86 vsyscall emulation
Disabling it is roughly equivalent to booting with vsyscall=none, except that it will also disable the helpful warning if a program tries to use a ...Rule Low Severity -
Kernel GCC plugin configuration
Contains rules that check the configuration of GCC plugins used by the compilerGroup -
Configure Syslog
The syslog service has been the default Unix logging mechanism for many years. It has a number of downsides, including inconsistent log format, lac...Group -
Ensure rsyslog is Installed
Rsyslog is installed by default. Thersyslogpackage can be installed with the following command:$ apt-get install rsyslog
Rule Medium Severity -
Enable rsyslog Service
The <code>rsyslog</code> service provides syslog-style logging by default on Debian 10. The <code>rsyslog</code> service can be enabled with the f...Rule Medium Severity -
Configure Logwatch on the Central Log Server
Is this system the central log server? If so, edit the file/etc/logwatch/conf/logwatch.confas shown below.Group -
Ensure Proper Configuration of Log Files
The file <code>/etc/rsyslog.conf</code> controls where log message are written. These are controlled by lines called <i>rules</i>, which consist of...Group -
User who owns log files
Specify user owner of all logfiles specified in/etc/rsyslog.conf.Value -
Ensure Rsyslog Authenticates Off-Loaded Audit Records
Rsyslogd is a system utility providing support for message logging. Support for both internet and UNIX domain sockets enables this utility to suppo...Rule Medium Severity -
Ensure Rsyslog Encrypts Off-Loaded Audit Records
Rsyslogd is a system utility providing support for message logging. Support for both internet and UNIX domain sockets enables this utility to suppo...Rule Medium Severity -
Configure rsyslogd to Accept Remote Messages If Acting as a Log Server
By default, <code>rsyslog</code> does not listen over the network for log messages. If needed, modules can be enabled to allow the rsyslog daemon t...Group -
net.ipv6.conf.all.router_solicitations
Accept all router solicitations?Value -
Ensure Rsyslog Encrypts Off-Loaded Audit Records
Rsyslogd is a system utility providing support for message logging. Support for both internet and UNIX domain sockets enables this utility to suppo...Rule Medium Severity -
Ensure Log Files Are Owned By Appropriate User
The owner of all log files written by <code>rsyslog</code> should be <code>adm</code>. These log files are determined by the second part of each ...Rule Medium Severity -
Ensure System Log Files Have Correct Permissions
The file permissions for all log files written by <code>rsyslog</code> should be set to 640, or more restrictive. These log files are determined by...Rule Medium Severity -
systemd-journald
systemd-journald is a system service that collects and stores logging data. It creates and maintains structured, indexed journals based on logging ...Group -
Enable systemd-journald Service
The <code>systemd-journald</code> service is an essential component of systemd. The <code>systemd-journald</code> service can be enabled with the ...Rule Medium Severity -
Ensure All Logs are Rotated by logrotate
Edit the file <code>/etc/logrotate.d/syslog</code>. Find the first line, which should look like this (wrapped for clarity): <pre>/var/log/message...Group -
Ensure logrotate is Installed
logrotate is installed by default. The <code>logrotate</code> package can be installed with the following command: <pre> $ apt-get install logrotat...Rule Medium Severity -
Ensure Logrotate Runs Periodically
The <code>logrotate</code> utility allows for the automatic rotation of log files. The frequency of rotation is specified in <code>/etc/logrotate....Rule Medium Severity -
net.ipv4.conf.default.secure_redirects
Enable to prevent hijacking of routing path by only allowing redirects from gateways known in routing table. Disable to refuse acceptance of secure...Value -
Enable rsyslog to Accept Messages via TCP, if Acting As Log Server
The <code>rsyslog</code> daemon should not accept remote messages unless the system acts as a log server. If the system needs to act as a central l...Rule Unknown Severity -
Enable rsyslog to Accept Messages via UDP, if Acting As Log Server
The <code>rsyslog</code> daemon should not accept remote messages unless the system acts as a log server. If the system needs to act as a central l...Rule Unknown Severity -
Rsyslog Logs Sent To Remote Host
If system logs are to be useful in detecting malicious activities, it is necessary to send logs to a remote server. An intruder who has compromised...Group -
Remote Log Server
Specify an URI or IP address of a remote host where the log messages will be sent and stored.Value -
Ensure Logs Sent To Remote Host
To configure rsyslog to send logs to a remote log server, open <code>/etc/rsyslog.conf</code> and read and understand the last section of the file,...Rule Medium Severity -
Network Configuration and Firewalls
Most systems must be connected to a network of some sort, and this brings with it the substantial risk of network attack. This section discusses th...Group -
firewalld
The dynamic firewall daemon <code>firewalld</code> provides a dynamically managed firewall with support for network “zones” to assign a level of tr...Group -
Inspect and Activate Default firewalld Rules
Firewalls can be used to separate networks into different zones based on the level of trust the user has decided to place on the devices and traffi...Group -
Strengthen the Default Ruleset
The default rules can be strengthened. The system scripts that activate the firewall rules expect them to be defined in configuration files under t...Group -
IPSec Support
Support for Internet Protocol Security (IPsec) is provided with Libreswan.Group -
iptables and ip6tables
A host-based firewall called <code>netfilter</code> is included as part of the Linux kernel distributed with the system. It is activated by default...Group -
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 analog...Group -
Verify ip6tables Enabled if Using IPv6
Theip6tablesservice can be enabled with the following command:$ sudo systemctl enable ip6tables.service
Rule Medium Severity -
Verify iptables Enabled
Theiptablesservice can be enabled with the following command:$ sudo systemctl enable iptables.service
Rule Medium Severity -
Set Default ip6tables Policy for Incoming Packets
To set the default policy to DROP (instead of ACCEPT) for the built-in INPUT chain which processes incoming packets, add or correct the following l...Rule Medium Severity -
Strengthen the Default Ruleset
The default rules can be strengthened. The system scripts that activate the firewall rules expect them to be defined in the configuration files <co...Group -
Set Default iptables Policy for Incoming Packets
To set the default policy to DROP (instead of ACCEPT) for the built-in INPUT chain which processes incoming packets, add or correct the following l...Rule Medium Severity -
net.ipv6.conf.default.accept_ra_defrtr
Accept default router in router advertisements?Value -
Set Default iptables Policy for Forwarded Packets
To set the default policy to DROP (instead of ACCEPT) for the built-in FORWARD chain which processes packets that will be forwarded from one interf...Rule Medium Severity -
Restrict ICMP Message Types
In <code>/etc/sysconfig/iptables</code>, the accepted ICMP messages types can be restricted. To accept only ICMP echo reply, destination unreachabl...Group -
Log and Drop Packets with Suspicious Source Addresses
Packets with non-routable source addresses should be rejected, as they may indicate spoofing. Because the modified policy will reject non-matching ...Group
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