• fschl dotfiles
  • Questions this repos tries to answer
    • Security
      • Hardening ssh
      • GnuPG
      • Managing logins & passphrases
      • Backup Secure Keys
      • thumb drive setup
      • building kali linux iso [0/7]
  • [0/4]

fschl dotfiles

Things that make my linux life more comfortable, portable and secure. For debian, or debian-based distros. using i3wm.org on the desktop.

Questions this repos tries to answer

• How long does it take for you to set up a machine?
• Do you have backups?
• Are you using a password manager?
• How do you transport your secrets?

• Can you get things done without your computer?

  • Rescue+Recover friends laptops/computers
  • panic-ops using a friends laptop

Security

Hardening ssh

• https://blog.g3rt.nl/upgrade-your-ssh-keys.html
• https://stribika.github.io/2015/01/04/secure-secure-shell.html
• https://wiki.mozilla.org/Security/Guidelines/OpenSSH#OpenSSH_client
• see `/etc/ssh/ssh_config` and `.ssh/config`

add this to `~/.ssh/config`:

# Ensure KnownHosts are unreadable if leaked - it is otherwise easier to know which hosts your keys have access to.
HashKnownHosts yes
# Host keys the client accepts - order here is honored by OpenSSH
HostKeyAlgorithms ssh-ed25519-cert-v01@openssh.com,ssh-rsa-cert-v01@openssh.com,ssh-ed25519,ssh-rsa,ecdsa-sha2-nistp521-cert-v01@openssh.com,ecdsa-sha2-nistp384-cert-v01@openssh.com,ecdsa-sha2-nistp256-cert-v01@openssh.com,ecdsa-sha2-nistp521,ecdsa-sha2-nistp384,ecdsa-sha2-nistp256

KexAlgorithms curve25519-sha256@libssh.org,ecdh-sha2-nistp521,ecdh-sha2-nistp384,ecdh-sha2-nistp256,diffie-hellman-group-exchange-sha256
MACs hmac-sha2-512-etm@openssh.com,hmac-sha2-256-etm@openssh.com,umac-128-etm@openssh.com,hmac-sha2-512,hmac-sha2-256,umac-128@openssh.com
Ciphers chacha20-poly1305@openssh.com,aes256-gcm@openssh.com,aes128-gcm@openssh.com,aes256-ctr,aes192-ctr,aes128-ctr

generating keys

# RSA keys are favored over ECDSA keys when backward compatibility ''is required'',
# thus, newly generated keys are always either ED25519 or RSA (NOT ECDSA or DSA).
$ ssh-keygen -t rsa -b 8192 -f ~/.ssh/id_rsa_host_$(date +%Y-%m-%d) -C "Key to HOST for user-xyz"

# ED25519 keys are favored over RSA keys when backward compatibility ''is not required''.
# This is only compatible with OpenSSH 6.5+ and fixed-size (256 bytes).
$ ssh-keygen -t ed25519 -f ~/.ssh/id_ed25519_host_$(date +%Y-%m-%d) -C "Key to HOST for user-xyz"

GnuPG

• https://wiki.mozilla.org/Security/Key_Management
• https://keyring.debian.org/creating-key.html
• https://wiki.debian.org/Subkeys

`~/.gnupg/gpg.conf`:

personal-digest-preferences SHA512 SHA384
cert-digest-algo SHA256
default-preference-list SHA512 SHA384 AES256 ZLIB BZIP2 ZIP Uncompressed
keyid-format 0xlong

Managing logins & passphrases

• use a secure, cross-platform, cloudless password manager, e.g keepassXC

Backup Secure Keys

• get 2 USB thumb drives
• on each, create 2 partitions (ext4, you will never use them on any windows device anyway)
• https://wiki.archlinux.org/index.php/Dm-crypt/Device_Encryption

Nowadays it's mere chance to find a USB thumb drive with less than 4GB storage. Though, you want a dedicated drive to transport your password database, ssh keys and GPG keys. Those don't require more than a couple MB. So what to do with the remaining space?

Scenarios:

• You visit friends, only have your keys with you and you have to check your mails, assist a colleague in some network/ops emergency or just securely look up some confidential information.
• A family member calls: their HDD just died and you are asked to quickly help out on recovery.

Boot into a safe environment, having all your credentials available in a secure manner. Have a bootable forensics toolbox around to quickly get going in a familiar setup.

Solution: multi-boot!

thumb drive setup

3 partitions: boot+isos, luks encrypted, unencrypted partition for non-sensitive data

building kali linux iso [0/7]

• https://docs.kali.org/downloading/kali-linux-live-usb-install
• add encrypted persistence https://docs.kali.org/downloading/kali-linux-live-usb-persistence
• add kali meta packages https://www.kali.org/news/kali-linux-metapackages/
• https://docs.kali.org/development/live-build-a-custom-kali-iso
• customize live image contents https://live-team.pages.debian.net/live-manual/html/live-manual/customizing-contents.en.html#517
• add LUKS Nuke support https://www.kali.org/tutorials/nuke-kali-linux-luks/
• OPTIONAL add PowerShell https://www.kali.org/tutorials/installing-powershell-on-kali-linux/

TODO [0/4]

• explain setup, ideas, practises
• add HOWTO
• seperate sources.list setup for server/desktop/laptop
• move to ansible for easier modularization of setup