security

SELinux Concepts – but for humans

SELinux has been an annoyance for me since the early days of Fedora and Red Hat bringing it into the distribution and enabling by default (see this blog post, for example, from 2004 about Fedora 3).

Over the years, I’ve tried to learn it, make it useful, and find benefits in using it, but somehow those were never enough and I keep falling back on the disabling it. But on the other hand, my understanding of how SELinux works slowly is growing. The video in this blog post helped a lot.

And now I’m glad to add another useful resource to the “SELinux for mere mortals” collection. The blog mostly focuses on the terminology in the SELinux domain, and what means what. It’s so simple and straight-forward, that it even uses examples of HTML and CSS – something I’ve never seen before. If you are making your way through the “how the heck do I make sense of SELinux” land, check it out. I’m sure it’ll help.

Fixing outdated Let’s Encrypt (zope.interface error)

I’ve started using Let’s Encrypt for the SSL certificates a while back. I installed it on all the web servers, irrelevant of the need for SSL, just to have it there, when I need it (thanks to this Ansible role). One of those old web servers needed an SSL certificate recently, so I thought it’d be no problem to generate one.

But I was wrong. The letsencrypt-auto tool got outdated and was failing to execute, throwing some Python exception about missing zope.interface module. A quick Google search brought this StackOverflow discussion, with the exact issue I was having.

Traceback (most recent call last):
  File "/root/.local/share/letsencrypt/bin/letsencrypt", line 7, in <module>
    from certbot.main import main
  File "/root/.local/share/letsencrypt/local/lib/python2.7/dist-packages/certbot/main.py", line 12, in <module>
    import zope.component
  File "/root/.local/share/letsencrypt/local/lib/python2.7/dist-packages/zope/component/__init__.py", line 16, in <module>
    from zope.interface import Interface
ImportError: No module named interface

However, the solution didn’t fix the problem for me:

unset PYTHON_INSTALL_LAYOUT
/opt/letsencrypt/letsencrypt-auto -v

Even pulling the updated version from the GitHub repository didn’t solve it.

After poking around for a while more, I found this bug report from the last year, which solved my problem.

I recommend:

Running rm -rf /root/.local/share/letsencrypt. This removes your installation of letsencrypt, but keeps all configuration files, certificates, logs, etc.

Make sure you have an up to date copy of letsencrypt-auto. It can be found here.

Run letsencrypt-auto again.

If you get the same behavior, you can try installing zope.interface manually by running:

/root/.local/share/letsencrypt/bin/pip install zope.interface

Hopefully, next time I’ll remember to search my blog’s archives …

Update (May 31, 2017): check out my brother’s follow up post with even better way of fixing this issue.

Dissecting an SSL certificate

Julia Evans does it again. If you ever wanted to understand SSL certificates, her post “Dissecting an SSL certificate” is for you. This part made me smile:

Picking the right settings for your SSL certificates and SSL configuration on your webserver is confusing. As far as I understand it there are about 3 billion settings. Here is an example of an SSL Labs result for mail.google.com. There is all this stuff like OLD_TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305_SHA256 on that page (for real, that is a real thing.). I’m happy there are tools like SSL Labs that help mortals make sense of all of it.

Google and HTTPS

Here are some interesting news on the subject of Google and HTTPS:

In support of our work to implement HTTPS across all of our products (https://www.google.com/transparencyreport/https/) we have been operating our own subordinate Certificate Authority (GIAG2), issued by a third-party. This has been a key element enabling us to more rapidly handle the SSL/TLS certificate needs of Google products.

As we look forward to the evolution of both the web and our own products it is clear HTTPS will continue to be a foundational technology. This is why we have made the decision to expand our current Certificate Authority efforts to include the operation of our own Root Certificate Authority. To this end, we have established Google Trust Services (https://pki.goog/), the entity we will rely on to operate these Certificate Authorities on behalf of Google and Alphabet.

The process of embedding Root Certificates into products and waiting for the associated versions of those products to be broadly deployed can take time. For this reason we have also purchased two existing Root Certificate Authorities, GlobalSign R2 and R4. These Root Certificates will enable us to begin independent certificate issuance sooner rather than later.

We intend to continue the operation of our existing GIAG2 subordinate Certificate Authority.

If you need a bit of help putting this into perspective, this Hacker News thread has your back:

You can now have a website secured by a certificate issued by a Google CA, hosted on Google web infrastructure, with a domain registered using Google Domains, resolved using Google Public DNS, going over Google Fiber, in Google Chrome on a Google Chromebook. Google has officially vertically integrated the Internet.

Immutable Infrastructure with AWS and Ansible

Immutable infrastructure is a very powerful concept that brings stability, efficiency, and fidelity to your applications through automation and the use of successful patterns from programming. The general idea is that you never make changes to running infrastructure. Instead, you ensure that all infrastructure is created through automation, and to make a change, you simply create a new version of the infrastructure, and destroy the old one.

“Immutable Infrastructure with AWS and Ansible” is a, so far, three part article series (part 1, part 2, part 3), that shows how to use Ansible to achieve an immutable infrastructure on the Amazon Web Services cloud solution.

It covers everything starting from the basic setup of the workstation to execute Ansible playbooks and all the way to AWS security (users, roles, security groups), deployment of resources, and auto-scaling.