Engineering and technology notes

Server Name Indication

Jovan Stosic February 23, 2020

Server Name Indication (SNI) is an extension to the Transport Layer Security (TLS) computer networking protocol by which a client indicates which hostname it is attempting to connect to at the start of the handshaking process. This allows a server to present multiple certificates on the same IP address and TCP port number and hence allows multiple secure (HTTPS) websites (or any other service over TLS) to be served by the same IP address without requiring all those sites to use the same certificate. It is the conceptual equivalent to HTTP/1.1 name-based virtual hosting, but for HTTPS. The desired hostname is not encrypted in the original SNI extension, so an eavesdropper can see which site is being requested.

https://en.wikipedia.org/wiki/Server_Name_Indication

Certbot `–reuse-key` flag does not preserve public key – Help – Let’s Encrypt Community Support

Jovan Stosic February 23, 2020

According to the documentation, it is possible to tell certbot to reuse the same private key that already exists in the current certificate. Thus I have been running the following command to renew certificates:

certbot renew
–rsa-key-size 4096
–no-self-upgrade
–dns-route53
–noninteractive
–reuse-key
–post-hook ‘systemctl reload nginx.service’

Nevertheless, the cert.pem is modified after this operation – when diffing it with its version before renewal. I would expect it not to change at all since the private key is being reused.

I need to reuse the same public key in order to avoid pinning issues with IOS, is there a way to actually preserve it?

https://community.letsencrypt.org/t/certbot-reuse-key-flag-does-not-preserve-public-key/101049

How to recreate let’s encrypt certificate with public key from the past? – Help – Let’s Encrypt Community Support

Jovan Stosic February 23, 2020

9I’m going to be working on this much-delayed feature next week, but I agree with the suggestion to use another ACME client for now. Right now the only way to do this with Certbot is to create a CSR using the old key and then use --csr (which won’t work with certbot renew, so it’s less convenient).

sudo certbot certonly –csr /etc/letsencrypt/csr/csr-certbot.pem

https://community.letsencrypt.org/t/how-to-recreate-lets-encrypt-certificate-with-public-key-from-the-past/60096

Nagios

Jovan Stosic February 22, 2020

Nagios /ˈnɑːɡiːoʊs/, now known as Nagios Core, is a free and open-source computer–software application that monitors systems, networks and infrastructure. Nagios offers monitoring and alerting services for servers, switches, applications and services. It alerts users when things go wrong and alerts them a second time when the problem has been resolved.

Ethan Galstad and a group of developers originally wrote Nagios as NetSaint. As of 2015 they actively maintain both the official and unofficial plugins. Nagios is a recursive acronym: “Nagios Ain’t Gonna Insist On Sainthood” – “sainthood” makes reference to the original name NetSaint, which changed in response to a legal challenge by owners of a similar trademark. “Agios” (or “hagios”) also transliterates the Greek word άγιος, which means “saint”.

Nagios was originally designed to run under Linux, but it also runs well on other Unix variants. It is free software licensed under the terms of the GNU General Public License version 2 as published by the Free Software Foundation.

https://en.wikipedia.org/wiki/Nagios

Gray’s Anatomy

Jovan Stosic February 21, 2020

Gray’s Anatomy is an English written textbook of human anatomy originally written by Henry Gray and illustrated by Henry Vandyke Carter. Earlier editions were called Anatomy: Descriptive and Surgical, Anatomy of the Human Body and Gray’s Anatomy: Descriptive and Applied, but the book’s name is commonly shortened to, and later editions are titled, Gray’s Anatomy. The book is widely regarded as an extremely influential work on the subject, and has continued to be revised and republished from its initial publication in 1858 to the present day. The latest edition of the book, the 41st, was published in September 2015.

https://en.wikipedia.org/wiki/Gray%27s_Anatomy