ISP-Guru

If you do a lot of Linux installs, and have a local mirror repo, you’re probably used to changing your /etc/yum.repos.d/ files to reflect your mirror after every install, and after some upgrades. You can make this more efficient and less painful by rebuilding the release RPM to point to your local mirror. This way, anyone who installs from your mirror will come back to your mirror for updates.

This is a trivial process, but none of the places I’ve worked have done it. If you do this, care must be taken to prevent the next update of the mirror from clobbering your customized release.

I’m going to demonstrate how to do it in CentOS, but RedHat and Fedora are similar, of course.

First, go to a computer with your distro freshly installed. Install the additional package rpm-build, then install the rpmrebuild package from http://sourceforge.net/project/showfiles.php?group_id=57523.

Now, update your /etc/yum.repos.d files to point to your local mirror, and then check their syntax using the yum check-update command. Assuming it works, you’re ready to rebuild your release rpm. (The centos-release, fedora-release, etc. package owns your repository files) The command to rebuild a CentOS release file is: rpmrebuild centos-release. It will confirm that you want to include the updated files, then it will ask if you want to change the release number (the default is no, so I stick with that). Once you accept these, it will tell you where it puts your newly-repackaged RPM.

Simply overwrite the original RPM in your repo with this one, and the next person who installs from your repo will have your customizations already included.

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This is the third and final installment in the RHCSS Study series. With this installment, especially since it is a newish technology that can be difficult to wrap your head around at first, I recommend studying the course objectives listed below along with one or more of these fine publications:

RHS 429: SELinux Policy Administration

Unit 1 - Introduction to SELinux

* Discretionary Access Control vs. Mandatory Access Control
* SELinux History and Architecture Overview
* Elements of the SELinux security model:
o user identity and role
o domain and type
o sensitivity and categories
o security context
* SELinux Policy and Red Hat’s Targeted Policy
* Configuring Policy with Booleans
* Archiving
* Setting and Displaying Extended Attributes
* Hands-on Lab: Understanding SELinux

Unit 2 - Using SELinux

* Controlling SELinux
* File Contexts
* Relabeling Files and Filesystems
* Mount options
* Hand-on Lab: Working with SELinux

Unit 3 - The Red Hat Targeted Policy

* Identifying and Toggling Protected Services
* Apache Security Contexts and Configuration Booleans
* Name Service Contexts and Configuration Booleans
* NIS Client Contexts
* Other Services
* File Context for Special Directory Trees
* Troubleshooting and avc Denial Messages
* setroubleshootd and Logging
* Hands-on Lab: Understanding and Troubleshooting the Red Hat Targeted Policy

Unit 4 - Introduction to Policies

* Policy Overview and Organization
* Compiling and Loading the Monolithic Policy and Policy Modules
* Policy Type Enforcement Module Syntax
* Object Classes
* Domain Transition
* Hands-on Lab: Understanding policies

Unit 5 - Policy Utilities

* Tools available for manipulating and analyzing policies
o apol
o seaudit and seaudit_report
o checkpolicy
o sepcut
o sesearch
o sestatus
o audit2allow and audit2why
o sealert
o avcstat
o seinfo
o semanage and semodule
o Man pages
* Hands-on Lab: Exploring Utilities

Unit 6 - User and Role Security

* Role-based Access Control
* Multi Category Security
* Defining a Security Administrator
* Multi-Level Security
* The strict Policy
* User Identification and Declaration
* Role Identification and Declaration
* Roles in Use in Transitions
* Role Dominance
* Hands-on Lab: Implementing User and Role Based Policy Restrictions

Unit 7 - Anatomy of a Policy

* Policy Macros
* Type Attributes and Aliases
* Type Transitions
* When and How do Files Get Labeled
* restorecond
* Customizable Types
* Hands-on Lab: Building Policies

Unit 8 - Manipulating Policies

* Installing and Compiling Policies
* The Policy Language
* Access Vector
* SELinux logs
* Security Identifiers - SIDs
* Filesystem Labeling Behavior
* Context on Network Objects
* Creating and Using New Booleans
* Manipulating Policy by Example
* Macros
* Enableaudit
* Hands-on Lab: Compiling Policies

Unit 9 - Project

* Best practices
* Create File Contexts, Types and Typealiases
* Edit and Create Network Contexts
* Edit and Create Domains
* Hands-on Lab: Editing and Writing Policy

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XenSource published an interesting comparison of VMware ESX against XenEnterprise. It appears to be a rebuttal of an earlier VMware report, and places them neck and neck in terms of hypervisor performance. Take a look:

A Comparison of Commercial Hypervisors

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In the first installment of this series, I discussed the overall structure of Red Hat’s advanced certifications (beyond RHCE — RHCSS, RHCDS, and RHCA), and listed the objectives for the first exam of the RHCSS certification, the Network Services exam. By the way, all Red Hat exams cost $749, or $549 if purchased with the corresponding class. Most classes are four days, with the exams scheduled on Friday, and most classes cost $2,898, with the exception of the clustering and storage class, which is $3,998, probably due to the additional cost of enterprise-class storage hardware for the labs.

In my humble opinion, these exams are far too expensive. I think the “certificate of expertise” exams, which together comprise the advanced certs, should cost $250 each. This way the two next-step certs (exam-only, of course) end up each costing approximately what the RHCE costs, and the RHCA ends up being $1,250. There is something to be said for the current lack of study materials for these exams outside of Red Hat’s official curriculum — this places a premium on those who obtain the cert, because you know they either took the official approved course or they know their stuff. They didn’t cram for free, because there’s nowhere to cram.

Here are the objectives for the second exam in the RHCSS series:

RH423 Red Hat Enterprise Directory Services and Authentication
Course Outline

1. Introduction to Directory Services
* What is a directory?
* LDAP: models, schema, and attributes
* Object classes
* LDIF
2. The LDAP Naming Model
* Directory information trees and Distingued Names
* X.500 and “Internet” naming suffixes
* Planning the directory hierarchy
3. Red Hat Directory Server: Basic Configuration
* Installation and setup of Red Hat Directory Server
* Using the Red Hat Console
* Using logging to monitor Red Hat Directory Server activity
* Backing up and restoring the directory
* Basic performance tuning with indexes
4. Red Hat Directory Server: Authentication and Security
* Configuring TLS security
* Using access control instructions (ACI’s)
* ACI’s and the Red Hat Console
5. Searching and Modifying the LDAP Directory
* Using command line utilities to search the directory
* Search filter syntax
* Updating the directory
* Using graphical LDAP client utilities
6. Linux User Authentication with NSS and PAM
* Understanding authentication and authorization
* Name service switch (NSS)
* Advanced pluggable authentication modules (PAM) configuration
7. Centralized User Authentication with LDAP
* Central account management with LDAP
* Using migration scripts to migrate existing data into an LDAP server
* LDAP user authentication
8. Kerberos and LDAP
* Introduction to Kerberos
* Configuring the Kerberos key distribution center (KDC) and clients
* Configuring LDAP to support Kerberos
* Access control with Simple Authentication and Security Layer (SASL)
9. Directory Referrals and Replication
* Referrals and replication
* Single master configuration
* Multiple master configuration
* Planning for directory server availability
10. Authenticating Windows Clients
* Windows networking overview
* Configuring a Samba primary domain controller (PDC) using LDAP
11. Windows Domain Authentication and Linux Clients
* Active Directory servers
* Linux as a client
* Active Directory and NSS
* OpenLDAP
* Winbind

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Beyond RHCE, Red Hat offers “certificates of expertise” which, when stacked together, become advanced certifications.

The RHCSS, Red Hat Certified Security Specialist, requires three exams:

The RHCDS, Red Hat Certified Datacenter Specialist, requires three exams:

The RHCA, the ultimate commercial-facing certification in the Red Hat family (there are further certs available for trainers and those conducting examinations, but to me those fall into the “academic” classification). RHCA requires five exams: the three from the RHCDS cert, one from the RHCSS cert, and one additional:

For now, let’s focus on the RHCSS, and more granularly on the first exam of the trifecta required for the RHCSS, the Network Services exam. Since there is an overwhelming lack of curriculum, study guides, etc., online or in print, I present here the objectives from Red Hat’s own course description, as well as links to books that will most certainly aid in your studying, as well as being permanent references on the relevant topics.

RHS333: Red Hat Enterprise Security: Network Services

What you will learn:

RHS333 goes beyond the essential security coverage offered in the RHCE curriculum and delves deeper into the security features, capabilities, and risks associated with the most commonly deployed services. Among the topics covered in this four-day, hands-on course are the following:

1. The Threat Model and Protection Methods
* Internet threat model and the attacker’s plan
* System security and service availability
* An overview of protection mechanisms
2. Basic Service Security
* SELinux
* Host-based access control
* Firewalls using Netfilter and iptables
* TCP wrappers
* xinetd and service limits
3. Cryptography
* Overview of cryptographic techniques
* Management of SSL certificates
* Using GnuPG
4. Logging and NTP
* Time synchronization with NTP
* Logging: syslog and its weaknesses
* Protecting log servers
5. BIND and DNS Security
* BIND vulnerabilities
* DNS Security: attacks on DNS
* Access control lists
* Transaction signatures
* Restricting zone transfers and recursive queries
* DNS Topologies
* Bogus servers and blackholes
* Views
* Monitoring and logging
* Dynamic DNS security
6. Network Authentication: RPC, NIS, and Kerberos
* Vulnerabilities
* Network-managed users and account management
* RPC and NIS security issues
* Improving NIS security
* Using Kerberos authentication
* Debugging Kerberized Services
* Kerberos Cross-Realm Trust
* Kerberos Encryption
7. Network File System
* Overview of NFS versions 2, 3, and 4
* Security in NFS versions 2 and 3
* Improvements in security in NFS4
* Troubleshooting NFS4
* Client-side mount options
8. OpenSSH
* Vulnerabilities
* Server configuration and the SSH protocols
* Authentication and access control
* Client-side security
* Protecting private keys
* Port-forwarding and X11-forwarding issues
9. Electronic Mail with Sendmail
* Vulnerabilities
* Server topologies
* Email encryption
* Access control and STARTTLS
* Anti-spam mechanisms
10. Postfix
* Vulnerabilities
* Security and Postfix design
* Configuring SASL/TLS
11. FTP
* Vulnerabilities
* The FTP protocol and FTP servers
* Logging
* Anonymous FTP
* Access control
12. Apache security
* Vulnerabilities
* Access control
* Authentication: files, passwords, Kerberos
* Security implications of common configuration options
* CGI security
* Server side includes
* suEXEC
13. Intrusion Detection and Recovery
* Intrusion risks
* Security policy
* Detecting possible intrusions
* Monitoring network traffic and open ports
* Detecting modified files
* Investigating and verifying detected intrusions
* Recovering from, reporting, and documenting intrusions

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