Using KDC Proxy to authenticate users

How to authenticate users with Kerberos when port 88 is not available in a DMZ? Use an HTTPS server as a proxy. IPA comes with an integrated KDC Proxy and it’s simple to make use of it. A typical use case is a cross-domain trust with AD, where the Linux clients are not allowed to directly talk to AD because of firewall and/or security policy restrictions. Another use-case is where clients in a DMZ are not allowed to directly communicate ….Read More

Using DNSSEC with (Free) IPA

The DNS infrastructure contains a growing number of critical information such as services records pointing to authentication services, TLSA records, SSH fingerprints and the like. DNSSEC signs this information, the client can trust the information DNS sends. It protects against forged information through cache poisoning. This article shows how to achieve a DNSSEC protected DNS environment with the help of FreeIPA This article was taking some time to write as I wanted to see how it behaves in the long ….Read More

Using MTA-STS to enhance email transport security and privacy

Overview SMTP is broken by design. It comes from a time when communication partners trusted each other and the NSA was intercepting facsimiles and phone calls instead of internet traffic. To enhance privacy, in 2002 RFC 3208 was added to the SMTP protocol. Unfortunately STARTTLS is only optional, it is not allowed to only accept encrypted connections. The RFC states: A publicly-referenced SMTP server MUST NOT require the use of the STARTTLS extension in order to deliver mail locally. That ….Read More

Centrally manage SELinux user mapping with (Free)IPA

SELinux allows to confine users with SELinux user mappings. This article covers some basics about the confinement of users and shows how to manage them in central way with the help of (Free)IPA. It will greatly enhance your systems security. SELinux is available and enabled on all Red Hat based distributions such as RHEL, CentOS and Fedora. for the basics please have a look at article. Before proceeding with the examples in this article: ensure your system is running in ….Read More

Leveraging Network-Bound Disk Encryption at Enterprise Scale

Network-Bound Disk Encryption (NBDE) adds scaling to LUKS by automated disk unlocking on system startup. Why should I encrypt disks? If you dont want to see your corporate and private data leaked, you should do so as an additional security measure. Use cases There are basically two use cases for disk encryption. The first one is to prevent data leaks when a device gets stolen or lost (mobile computers, unsecured server rooms etc.). Theft of devices is usually not a ….Read More

Blueborne – How to disable Bluetooth in Fedora

Yesterday 2017-09-13 Redhat released infomation about the mitigation of the Blueborne vulnerability in RHEL: For Fedora the new updates are probably still in the build queue and/or being QAed by the community. For a quick fix, you can disable Bluetooth similar than in RHEL: Stopping Bluetooth related service systemctl stop bluetooth.service systemctl disable bluetooth.service systemctl mask bluetooth.service Disable the Kernel modules echo “install bnep /bin/true” >> /etc/modprobe.d/disable-bluetooth.conf echo “install bluetooth /bin/true” >> /etc/modprobe.d/disable-bluetooth.conf echo “install btusb /bin/true” >> /etc/modprobe.d/disable-bluetooth.conf ….Read More

Signing Linux Kernel Modules and enforce to load only signed Modules

Introduction With the enforcement of loading only signed Linux Kernel Modules you can greatly enhance the security of your Systems. There are basically two methods of enforcement: Secure (UEFI) Boot and the other is a grub parameter. When using Secure boot you can sign own (or 3rd party) Kernel modules by yourself and add your public key as a MOK (Machine Owner Key) in UEFI. When not using Secure Boot, you can not load self signed modules due to the ….Read More

Audit your systems for security compliance with OpenSCAP

Introduction to (Open)SCAP SCAP stands for Security Content Automation Protocol. It is an open standard which defines methods for security policy compliance, vulnerability management and measurement etc. This article focuses on the operating system compliance part of SCAP. It comes originally from the US National Institute of Standards and Technology (NIST) to provide a way for US government agencies to audit its systems for regulatory compliance. OpenSCAP is a NIST validated open source implementation of SCAP. Why should I make ….Read More