“Passkeys and the WebAuthn specification were intended to make public key cryptography accessible to average users, rather than just the domain of the tech-savvy. If done right, they could seriously improve security on the Web.” @Drbruced summarises why passkeys are such a good idea in theory and explains where current implementations of the technology fall down in practice.
Tag: security
A hacker’s perspective: social media account takeover prevention guide
“If you watched the SEC Twitter account hack that moved markets yesterday and wondered how to prevent account takeover for your personal, business, or high profile social media account, here’s an Account Takeover Prevention Guide for you and/or your organization.” @racheltobac neatly summarises the steps you should take to prevent the hijacking of your online accounts.
Install and configure SSH on Debian or Ubuntu
SSH is a protocol that enables secure connections over unsecured networks. It supports the use of asymmetric encryption for user authentication. Private keys are kept locally, while public keys are stored on the remote machine.
The following configuration disables root logins on the remote machine. Only users belonging to the group ssh-users may establish a connection. Access to the remote machine is tied to the local user’s private key.
In this example, the name of the remote machine is debian-server, which has the address 192.168.1.10 on the network. sid is a user on debian-server, whereas bookworm is a user on the local machine. Choose an encryption passphrase to secure the private key that you will generate in Step 5.
On the remote machine
Step 1
Install the secure shell server with the following command:
$ sudo apt install --yes openssh-server
Step 2
If you are using ufw as a host-based firewall
Configure ufw to allow connections to the secure shell server.
$ sudo ufw limit ssh
If you are using firewalld as a host-based firewall
Configure firewalld to allow connections to the secure shell server.
$ sudo -- bash -c 'firewall-cmd --zone=public --add-service=ssh --permanent && firewall-cmd --reload && firewall-cmd --info-zone=public'
Step 3
Restrict access to the remote machine to members of a specific group. Start by creating the group ssh-users.
$ sudo addgroup --system ssh-users
Add the user sid to the group ssh-users.
$ sudo adduser sid ssh-users
On the local machine
Step 4
Install the secure shell client with the following command.
$ sudo apt install openssh-client
Step 5
Generate a new key pair for the local user bookworm:
$ cd ~/.ssh && ssh-keygen -t ed25519 -o -a 100
Save the key pair to the directory /home/bookworm/.ssh/. Choose a name that facilitates easy identification.
Enter file in which to save the key (/home/bookworm/.ssh/id_ed25519): id_ed25519-debian-server
The use of an appropriate passphrase to secure the private key is mandatory.
Step 6
Create the file ~/.ssh/config to configure the secure shell client.
$ nano ~/.ssh/config
Add the follwing minimal entry for the host debian-server.
Host debian-server
Hostname 192.168.1.10
IdentityFile ~/.ssh/id_ed25519-debian-server
IdentitiesOnly yes
Step 7
Deploy the public key with the following command.
$ ssh-copy-id -i ~/.ssh/id_ed25519-debian-server.pub sid@debian-server
When prompted to confirm the authenticity of the host debian-server, type yes and press [Enter].
The authenticity of host 'debian-server (192.168.1.10)' can't be established. ED25519 key fingerprint is SHA256:C9RxLLVbvFwVJc0L4JHzcuHQSaPHJZe/GrRDvqy6rAG. This key is not known by any other names. Are you sure you want to continue connecting (yes/no/[fingerprint])?
Step 8
Log into the remote machine.
$ ssh -i ~/.ssh/id_ed25519-debian-server sid@debian-server
In the next step, enter the passphrase for your private key.
Enter passphrase for key '/home/bookworm/.ssh/id_ed25519-debian-server':
Step 9
On the remote machine, download a file to harden the ssh server. You are encouraged to inspect its contents.
$ sudo -- bash -c 'wget -P /etc/ssh/sshd_config.d/ --show-progress https://edafe.de/debian/sshd_config.conf'
Activate the modifications on the remote machine.
$ sudo systemctl restart ssh.service
Step 9
On the local machine, open a new terminal window and run the following command.
$ ssh -i ~/.ssh/id_ed25519-debian-server sid@debian-server
In the next step, enter the passphrase for your private key.
Enter passphrase for key '/home/bookworm/.ssh/id_ed25519-debian-server':
Display the active configuration for the remote ssh server and verify its settings, paying particular attention to options for maxauthtries, permitrootlogin and passwordauthentication.
$ sudo sshd -T
All done!
For more in-depth information, please see stribika’s post-Snowden advice on hardening OpenSSH server installations.
The book SSH The Secure Shell by Daniel Barrett, Richard Silverman and Robert Byrnes is still useful today and has information on other clever stuff you can do with SSH.
The process of security
“Security is a process, not a product. Products provide some protection, but the only way to effectively do business in an insecure world is to put processes in place that recognize the inherent insecurity in the products.” Bruce Schneier acknowledges that in information technology perfect security probably doesn’t exist.
Trust the process, Tina!
What’s in a PR statement: LastPass breach explained
“LastPass likely could have prevented this if they were more concerned about keeping their users secure than about saving their face. Their statement is also full of omissions, half-truths and outright lies. As I know that not everyone can see through all of it, I thought that I would pick out a bunch of sentences from this statement and give some context that LastPass didn’t want to mention.” Wladimir Palant helps to decode what LastPass had to say about their latest security breach.
Scaring people into supporting backdoors
“Beware the Four Horsemen of the Information Apocalypse: terrorists, drug dealers, kidnappers, and child pornographers. Seems like you can scare any public into allowing the government to do anything with those four.” Bruce Schneier re-emphasises the need for strong encryption as a matter of personal and national security.
Die AAA-Bürger
“So wie Alibaba und Amazon wissen, wofür sich ihre Nutzer interessieren und was sie als Nächstes kaufen könnten, will der chinesische Staat aus den Datenspuren seiner Bürger ableiten, wie sie sich in der Vergangenheit verhalten haben und in der Zukunft verhalten könnten und sie nach einem Punktesystem entsprechend bewerten. Wer zum Beispiel über das Internet gesunde Babynahrung bestellt, soll Pluspunkte erhalten. Wer sich hingegen Pornos ansieht oder zu viel Zeit mit Computerspielen verbringt, muss mit Abzügen rechnen.” Da trifft es sich gut, daß Felix Lee nichts zu verbergen hat und ein solcher Umgang mit Nutzerdaten überhaupt nur in China in Erwägung gezogen wird…
With thanks to Michael August.
Wie, Du bist nicht bei Whatsapp?
“Wer Whatsapp liebt, sollte besser nicht weiterlesen, oder vielleicht gerade dann, denn Liebe macht ja bekanntlich oft blind.” Boris Pohler, selbst Lehrer und Vater von zwei Kindern, bennent den Preis für die Verwendung des weit verbreiteten Dienstes und erklärt, warum jeder Nutzer gegen deutsches Recht verstößt.