Guide to the Secure Configuration of Debian release 8 (Jessie)
https://fedorahosted.org/scap-security-guide
Providing system administrators with such guidance informs them how to securely configure systems under their control in a variety of network roles. Policy makers and baseline creators can use this catalog of settings, with its associated references to higher-level security control catalogs, in order to assist them in security baseline creation. This guide is a catalog, not a checklist, and satisfaction of every item is not likely to be possible or sensible in many operational scenarios. However, the XCCDF format enables granular selection and adjustment of settings, and their association with OVAL and OCIL content provides an automated checking capability. Transformations of this document, and its associated automated checking content, are capable of providing baselines that meet a diverse set of policy objectives. Some example XCCDF Profiles, which are selections of items that form checklists and can be used as baselines, are available with this guide. They can be processed, in an automated fashion, with tools that support the Security Content Automation Protocol (SCAP).
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Revision History
Current version: 0.0.1
- draft (as of 2015-12-11)
Platforms
- cpe:/o:debianproject:debian:8
Table of Contents
Checklist
IntroductiongroupThe purpose of this guidance is to provide security configuration recommendations and baselines for the Debian operating system. Recommended settings for the basic operating system are provided, as well as for many network services that the system can provide to other systems. The guide is intended for system administrators. Readers are assumed to possess basic system administration skills for Unix-like systems, as well as some familiarity with Debian's documentation and administration conventions. Some instructions within this guide are complex. All directions should be followed completely and with understanding of their effects in order to avoid serious adverse effects on the system and its security. |
General PrinciplesgroupThe following general principles motivate much of the advice in this guide and should also influence any configuration decisions that are not explicitly covered. |
Encrypt Transmitted Data Whenever PossiblegroupData transmitted over a network, whether wired or wireless, is susceptible to passive monitoring. Whenever practical solutions for encrypting such data exist, they should be applied. Even if data is expected to be transmitted only over a local network, it should still be encrypted. Encrypting authentication data, such as passwords, is particularly important. Networks of Debian machines can and should be configured so that no unencrypted authentication data is ever transmitted between machines. |
Minimize Software to Minimize VulnerabilitygroupThe simplest way to avoid vulnerabilities in software is to avoid installing that software. On Debian, the Package Manager (originally apt https://www.debian.org/doc/manuals/debian-faq/ch-pkgtools.en.html) allows for careful management of the set of software packages installed on a system. Installed software contributes to system vulnerability in several ways. Packages that include setuid programs may provide local attackers a potential path to privilege escalation. Packages that include network services may give this opportunity to network-based attackers. Packages that include programs which are predictably executed by local users (e.g. after graphical login) may provide opportunities for trojan horses or other attack code to be run undetected. The number of software packages installed on a system can almost always be significantly pruned to include only the software for which there is an environmental or operational need. |
Run Different Network Services on Separate SystemsgroupWhenever possible, a server should be dedicated to serving exactly one network service. This limits the number of other services that can be compromised in the event that an attacker is able to successfully exploit a software flaw in one network service. |
Configure Security Tools to Improve System RobustnessgroupSeveral tools exist which can be effectively used to improve a system's resistance to and detection of unknown attacks. These tools can improve robustness against attack at the cost of relatively little configuration effort. In particular, this guide recommends and discusses the use of Iptables for host-based firewalling, SELinux for protection against vulnerable services, and a logging and auditing infrastructure for detection of problems. |
Least Privilegegroup
Grant the least privilege necessary for user accounts and software to perform tasks.
For example, |
How to Use This GuidegroupReaders should heed the following points when using the guide. |
Installationgroup |
PartitioninggroupSeparating various locations of the file systems in different partitions allows a more restrictive segregation, distinctly from one location to another. Moreover, some native restrictions can be made by partitioning, such as no hard link between different filesystems, and reduce the corruption impact to the affected filesystem instead of the entire system. The last gain is to allow a differenciated usage of storage media, depending on the operational needs (speed, resilience, etc.). references: Filesystem Hierarchy Standard |
Systemgroup |
Verify Permissions on Important Files and DirectoriesgroupPermissions for many files on a system must be set restrictively to ensure sensitive information is properly protected. This section discusses important permission restrictions which can be verified to ensure that no harmful discrepancies have arisen. |
Verify Permissions on Files with Local Account Information and CredentialsgroupThe default restrictive permissions for files which act as
important security databases such as |
Permissionsgroup |
Service managementgroupThe following sections contain information on security-relevant choices about software services that may be installed or blacklisted on the operating system. |
Deprecated servicesgroupSome deprecated software services impact the overall system security due to their behavior (leak of confidentiality in network exchange, usage as uncontrolled communication channel, risk associated with the service due to its old age, etc. |
Generic required servicesgroupSome services need to be deployed in order to ensure basic verifications and reporting on GNU/Linux operating systems. Each of these service take part in the administrability of the system. |