Webserver Basics
13 Mar, 2024
Webserver
The term web server can refer to hardware or software, or both of them working together.
On the hardware side, a web server is a computer that stores web server software and a website’s component files (for example, HTML documents, images, CSS stylesheets, and JavaScript files). A web server connects to the Internet and supports physical data interchange with other devices connected to the web.
On the software side, a web server includes several parts that control how web users access hosted files. At a minimum, this is an HTTP server. An HTTP server is software that understands URLs (web addresses) and HTTP (the protocol your browser uses to view webpages). An HTTP server can be accessed through the domain names of the websites it stores, and it delivers the content of these hosted websites to the end user’s device.
MDN (2024)
Static Webserver
A static web server, or stack, consists of a computer (hardware) with an HTTP server (software). We call it “static” because the server sends its hosted files as-is to your browser.
MDN (2024)
Dynamic Webserver
A dynamic web server consists of a static web server plus extra software, most commonly an application server and a database. We call it “dynamic” because the application server updates the hosted files before sending content to your browser via the HTTP server. :::aside::: MDN (2024) :::
HTTP servers
- Apache was the market leader in the past. Today, nginx and Apache are the most used webservers (Engine Ex). As we do not need PHP, which is part of Apache, we are going to use nginx as webserver for our course. :::aside
- Webserver Survey
- Wikipedia Webserver
- Wikipedia Nginx :::
SSH - Public Key Cryptography
If you want to use git, ssh or mail encryption you need to understand how public key cryptography works.
After working through this guide you should be able to
- understand when to use a private and when to use a public key
- generate a key pair for use in ssh and git
History
In the 1970ies several cryptographers invented public-key cryptography independently of each other. With the low computing power available then it could not be used in practice. Since the 1990ies it is used widely in ssh, e-mail encryption and SSL/TLS.
Basic idea
is to have an assymetric encryption system: two different keys are used: a public key for encryption and a private key for decryption.
- This system has some important consequences: Only Alice can ever read the encrypted message.
- Alice needs to keep here private key private, but can publish her public key anywhere: on the web, in an e-mail signature, on her business card.
We will be using public key cryptography for ssh and maybe git. For these systems the keys are stored in a folder .ssh in your home directory.
id_rsa- your private key is stored in~/.ssh/id_rsaid_rsa.pub- your public key is also in~/.ssh/id_rsa
The directory .ssh can also contain two other important files: config and authorized_keys.
But first: how do you get a key pair?
Generating keys
Decide which e-mail address you want to use. Type this in the terminal:
ssh-keygen -C exampleme@example.com -t rsaPress enter to accept the default key save location. Do not use a passphrase.
After key generation is complete, you’ll have output that looks like this:
Generating public/private rsa key pair.
Enter file in which to save the key (/home/student/.ssh/id_rsa):
Created directory '/home/student/.ssh'.
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in /home/student/.ssh/id_rsa.
Your public key has been saved in /home/student/.ssh/id_rsa.pub.
The key fingerprint is:
88:54:ab:11:fe:5a:c3:7s:14:37:28:8c:1d:ef:2a:8d exampleme@example.comNow check if your two keys are really stored in ~/.ssh/id_rsa and ~/.ssh/id_rsa.pub!
Using keys with ssh
- If you want to use these keys for logging in to a server without using a password, you have to copy over your public key to the server.
- On the server your public key must be stored in
~/.ssh/authorized_keys, then ssh will let you log in without giving a password
The authorized_keys file can contain several public keys:
ssh-rsa AAAAB3NzaC...2EAAAABI== alice@plus.ac.at
ssh-rsa AAAAB8NzaC...DVj3R4Ww== bob@plus.ac.atReferences
