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424 lines
13 KiB
Markdown
424 lines
13 KiB
Markdown
<!--
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Title: How to configure hardened Raspberry Pi OS server
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Description: Learn how to configure hardened Raspberry Pi OS server.
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Author: Sun Knudsen <https://github.com/sunknudsen>
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Contributors: Sun Knudsen <https://github.com/sunknudsen>
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Reviewers:
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Publication date: 2020-11-27T10:00:26.807Z
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Listed: true
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-->
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# How to configure hardened Raspberry Pi OS server
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[](https://www.youtube.com/watch?v=6R8uKdstnts "How to configure hardened Raspberry Pi OS server - YouTube")
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## Requirements
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- [Raspberry Pi](https://www.raspberrypi.org/)
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- Power adapter, keyboard and HDMI cable (and SD card reader if computer doesn’t have one built-in)
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- Linux or macOS computer
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## Caveats
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- When copy/pasting commands that start with `$`, strip out `$` as this character is not part of the command
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- When copy/pasting commands that start with `cat << "EOF"`, select all lines at once (from `cat << "EOF"` to `EOF` inclusively) as they are part of the same (single) command
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## Guide
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### Step 1: create SSH key pair (on computer)
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When asked for file in which to save key, enter `pi`.
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When asked for passphrase, use output from `openssl rand -base64 24` (and store passphrase in password manager).
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```console
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$ mkdir -p ~/.ssh
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$ cd ~/.ssh
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$ ssh-keygen -t rsa -C "pi"
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Generating public/private rsa key pair.
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Enter file in which to save the key (/Users/sunknudsen/.ssh/id_rsa): pi
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Enter passphrase (empty for no passphrase):
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Enter same passphrase again:
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Your identification has been saved in pi.
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Your public key has been saved in pi.pub.
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The key fingerprint is:
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SHA256:NZkr0Bmu6tpQfDp2GHTIPyBz253uZk/gOmoqzEszGM0 pi
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The key's randomart image is:
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+---[RSA 3072]----+
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| . |
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| . . o o o |
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| o * o + = |
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| o * * + o o |
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|. E = * S . |
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|.. . * + o |
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|++. * . o . |
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|ooo=.o.oo. |
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| o+++..+... |
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+----[SHA256]-----+
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$ cat pi.pub
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ssh-rsa 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 pi
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```
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### Step 2: generate heredoc (the output of following command will be used at [step 10](#step-10-configure-pi-ssh-authorized-keys))
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```shell
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cat << EOF
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cat << "_EOF" > /home/pi/.ssh/authorized_keys
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$(cat ~/.ssh/pi.pub)
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_EOF
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EOF
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```
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### Step 3: download latest version of [Raspberry Pi OS Lite](https://www.raspberrypi.org/software/operating-systems/)
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### Step 4: clone "Raspberry Pi OS Lite" to SD card
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> WARNING: DO NOT RUN THE FOLLOWING COMMANDS AS-IS.
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Run `diskutil list` to find disk ID of SD card to override with "Raspberry Pi OS Lite" (`disk2` in the following example).
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Replace `diskn` and `rdiskn` with disk ID of SD card (`disk2` and `rdisk2` in the following example) and `2020-12-02-raspios-buster-armhf-lite.img` with current image.
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```console
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$ diskutil list
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/dev/disk0 (internal, physical):
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#: TYPE NAME SIZE IDENTIFIER
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0: GUID_partition_scheme *500.3 GB disk0
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1: EFI EFI 209.7 MB disk0s1
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2: Apple_APFS Container disk1 500.1 GB disk0s2
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/dev/disk1 (synthesized):
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#: TYPE NAME SIZE IDENTIFIER
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0: APFS Container Scheme - +500.1 GB disk1
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Physical Store disk0s2
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1: APFS Volume Macintosh HD - Data 340.9 GB disk1s1
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2: APFS Volume Preboot 85.9 MB disk1s2
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3: APFS Volume Recovery 529.0 MB disk1s3
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4: APFS Volume VM 3.2 GB disk1s4
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5: APFS Volume Macintosh HD 11.3 GB disk1s5
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/dev/disk2 (internal, physical):
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#: TYPE NAME SIZE IDENTIFIER
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0: FDisk_partition_scheme *15.9 GB disk2
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1: Windows_FAT_32 boot 268.4 MB disk2s1
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2: Linux 15.7 GB disk2s2
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$ sudo diskutil unmount /dev/diskn
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disk2 was already unmounted or it has a partitioning scheme so use "diskutil unmountDisk" instead
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$ sudo diskutil unmountDisk /dev/diskn (if previous step fails)
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Unmount of all volumes on disk2 was successful
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$ sudo dd bs=1m if=/Users/sunknudsen/Downloads/2020-12-02-raspios-buster-armhf-lite.img of=/dev/rdiskn
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1772+0 records in
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1772+0 records out
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1858076672 bytes transferred in 40.449002 secs (45936280 bytes/sec)
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$ sudo diskutil unmountDisk /dev/diskn
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Unmount of all volumes on disk2 was successful
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```
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### Step 5: log in as pi (using keyboard) and change password using `passwd`
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> Heads-up: default password is `raspberry`.
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### Step 6: configure Wi-Fi (if not using ethernet)
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```shell
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sudo raspi-config
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```
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Select “System Options”, then “Wireless LAN”, choose country, then select “OK”, enter “SSID”, enter passphrase.
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### Step 7: enable SSH
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```shell
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sudo raspi-config
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```
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Select “Interface Options”, then “SSH”, then “Yes”, then “OK” and finally “Finish”.
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When asked if you wish to reboot, select “No”.
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### Step 8: find IP of Raspberry Pi (see `eth0` if using ethernet or `wlan0` if using Wi-Fi)
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```shell
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ip a
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```
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### Step 9: log in to Raspberry Pi over SSH
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Replace `10.0.1.248` with IP of Raspberry Pi.
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When asked for password, enter password from [step 5](#step-5-log-in-as-pi-using-keyboard-and-change-password-using-passwd).
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```shell
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ssh pi@10.0.1.248
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```
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### Step 10: configure pi SSH authorized keys
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#### Create `.ssh` folder
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```shell
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mkdir -p /home/pi/.ssh
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```
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#### Create `/home/pi/.ssh/authorized_keys` using heredoc generated at [step 2](#step-2-generate-heredoc-the-output-of-following-command-will-be-used-at-step-10)
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```shell
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cat << "_EOF" > /home/pi/.ssh/authorized_keys
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ssh-rsa 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 pi
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_EOF
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```
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### Step 11: log out
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```shell
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exit
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```
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### Step 12: log in to Raspberry Pi over SSH (using `pi` private key)
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Replace `10.0.1.248` with IP of Raspberry Pi.
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When asked for password, enter password from [step 1](#step-1-create-ssh-key-pair-on-computer).
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```shell
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ssh pi@10.0.1.248 -i ~/.ssh/pi
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```
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### Step 13: disable pi Bash history
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```shell
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sed -i -E 's/^HISTSIZE=/#HISTSIZE=/' ~/.bashrc
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sed -i -E 's/^HISTFILESIZE=/#HISTFILESIZE=/' ~/.bashrc
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echo "HISTFILESIZE=0" >> ~/.bashrc
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source ~/.bashrc
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```
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### Step 14: switch to root
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```shell
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sudo su -
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```
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### Step 15: disable root Bash history
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```shell
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echo "HISTFILESIZE=0" >> ~/.bashrc
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source ~/.bashrc
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```
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### Step 16: set root password
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When asked for password, use output from `openssl rand -base64 24` (and store password in password manager).
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```shell
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passwd
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```
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### Step 17: uninstall sudo
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```shell
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apt remove -y sudo
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```
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### Step 18: disable root login and password authentication
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```shell
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sed -i -E 's/^(#)?PermitRootLogin (prohibit-password|yes)/PermitRootLogin no/' /etc/ssh/sshd_config
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sed -i -E 's/^(#)?PasswordAuthentication yes/PasswordAuthentication no/' /etc/ssh/sshd_config
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systemctl restart ssh
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```
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### Step 19: disable Bluetooth and Wi-Fi
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> Heads-up: will take effect after reboot.
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#### Disable Bluetooth
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```shell
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echo "dtoverlay=disable-bt" | tee -a /boot/config.txt
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systemctl disable hciuart
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```
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#### Disable Wi-Fi (if using ethernet)
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```shell
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echo "dtoverlay=disable-wifi" | tee -a /boot/config.txt
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```
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### Step 20: update APT index and upgrade packages
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#### Update APT index
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```shell
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apt update
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```
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#### Upgrade packages
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```shell
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apt upgrade -y
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```
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### Step 21: install and configure Vim
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#### Install Vim
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```shell
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apt install -y vim
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```
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#### Configure Vim
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```shell
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cat << "EOF" > ~/.vimrc
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set encoding=UTF-8
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set termencoding=UTF-8
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set nocompatible
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set backspace=indent,eol,start
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set autoindent
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set tabstop=2
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set shiftwidth=2
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set expandtab
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set smarttab
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set ruler
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set paste
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syntax on
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EOF
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```
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### Step 22: set timezone (the following is for Montreal time)
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See [https://en.wikipedia.org/wiki/List_of_tz_database_time_zones](https://en.wikipedia.org/wiki/List_of_tz_database_time_zones) for available timezones.
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```shell
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timedatectl set-timezone America/Montreal
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```
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### Step 23: configure sysctl (if network is IPv4-only)
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> Heads-up: only run the following if network is IPv4-only.
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```shell
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cp /etc/sysctl.conf /etc/sysctl.conf.backup
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cat << "EOF" >> /etc/sysctl.conf
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net.ipv6.conf.all.disable_ipv6 = 1
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net.ipv6.conf.default.disable_ipv6 = 1
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net.ipv6.conf.lo.disable_ipv6 = 1
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EOF
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sysctl -p
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```
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### Step 24: install iptables-persistent
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When asked to save current IPv4 or IPv6 rules, answer `Yes`.
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```shell
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apt install -y iptables-persistent
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```
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### Step 25: configure iptables
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```shell
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iptables -N SSH_BRUTE_FORCE_MITIGATION
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iptables -A SSH_BRUTE_FORCE_MITIGATION -m recent --name SSH --set
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iptables -A SSH_BRUTE_FORCE_MITIGATION -m recent --name SSH --update --seconds 300 --hitcount 10 -m limit --limit 1/second --limit-burst 100 -j LOG --log-prefix "iptables[ssh-brute-force]: "
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iptables -A SSH_BRUTE_FORCE_MITIGATION -m recent --name SSH --update --seconds 300 --hitcount 10 -j DROP
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iptables -A SSH_BRUTE_FORCE_MITIGATION -j ACCEPT
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iptables -A INPUT -i lo -j ACCEPT
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iptables -A INPUT -p tcp --dport 22 --syn -m conntrack --ctstate NEW -j SSH_BRUTE_FORCE_MITIGATION
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iptables -A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
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iptables -A OUTPUT -o lo -j ACCEPT
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iptables -A OUTPUT -p tcp --dport 53 -m state --state NEW -j ACCEPT
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iptables -A OUTPUT -p udp --dport 53 -m state --state NEW -j ACCEPT
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iptables -A OUTPUT -p tcp --dport 80 -m state --state NEW -j ACCEPT
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iptables -A OUTPUT -p udp --dport 123 -m state --state NEW -j ACCEPT
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iptables -A OUTPUT -p tcp --dport 443 -m state --state NEW -j ACCEPT
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iptables -A OUTPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
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iptables -P FORWARD DROP
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iptables -P INPUT DROP
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iptables -P OUTPUT DROP
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```
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If network is IPv4-only, run:
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```shell
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ip6tables -P FORWARD DROP
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ip6tables -P INPUT DROP
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ip6tables -P OUTPUT DROP
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```
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If network is dual stack (IPv4 + IPv6) run:
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```shell
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ip6tables -A INPUT -i lo -j ACCEPT
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ip6tables -A INPUT -p ipv6-icmp --icmpv6-type destination-unreachable -j ACCEPT
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ip6tables -A INPUT -p ipv6-icmp --icmpv6-type packet-too-big -j ACCEPT
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ip6tables -A INPUT -p ipv6-icmp --icmpv6-type time-exceeded -j ACCEPT
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ip6tables -A INPUT -p ipv6-icmp --icmpv6-type parameter-problem -j ACCEPT
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ip6tables -A INPUT -p ipv6-icmp --icmpv6-type router-advertisement -m hl --hl-eq 255 -j ACCEPT
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ip6tables -A INPUT -p ipv6-icmp --icmpv6-type neighbor-solicitation -m hl --hl-eq 255 -j ACCEPT
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ip6tables -A INPUT -p ipv6-icmp --icmpv6-type neighbor-advertisement -m hl --hl-eq 255 -j ACCEPT
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ip6tables -A INPUT -p ipv6-icmp --icmpv6-type redirect -m hl --hl-eq 255 -j ACCEPT
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ip6tables -A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
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ip6tables -A OUTPUT -o lo -j ACCEPT
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ip6tables -A OUTPUT -p ipv6-icmp --icmpv6-type destination-unreachable -j ACCEPT
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ip6tables -A OUTPUT -p ipv6-icmp --icmpv6-type packet-too-big -j ACCEPT
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ip6tables -A OUTPUT -p ipv6-icmp --icmpv6-type time-exceeded -j ACCEPT
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ip6tables -A OUTPUT -p ipv6-icmp --icmpv6-type parameter-problem -j ACCEPT
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ip6tables -A OUTPUT -p ipv6-icmp --icmpv6-type router-solicitation -m hl --hl-eq 255 -j ACCEPT
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ip6tables -A OUTPUT -p ipv6-icmp --icmpv6-type neighbour-solicitation -m hl --hl-eq 255 -j ACCEPT
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ip6tables -A OUTPUT -p ipv6-icmp --icmpv6-type neighbour-advertisement -m hl --hl-eq 255 -j ACCEPT
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ip6tables -A OUTPUT -p tcp --dport 53 -m state --state NEW -j ACCEPT
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ip6tables -A OUTPUT -p udp --dport 53 -m state --state NEW -j ACCEPT
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ip6tables -A OUTPUT -p tcp --dport 80 -m state --state NEW -j ACCEPT
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ip6tables -A OUTPUT -p udp --dport 123 -m state --state NEW -j ACCEPT
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ip6tables -A OUTPUT -p tcp --dport 443 -m state --state NEW -j ACCEPT
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ip6tables -A OUTPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
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ip6tables -P FORWARD DROP
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ip6tables -P INPUT DROP
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ip6tables -P OUTPUT DROP
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```
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### Step 26: log out and log in to confirm iptables didn’t block SSH
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#### Log out
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```shell
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exit
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exit
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```
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#### Log in
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Replace `10.0.1.248` with IP of Raspberry Pi.
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When asked for password, enter password from [step 1](#step-1-create-ssh-key-pair-on-computer).
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```shell
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ssh pi@10.0.1.248 -i ~/.ssh/pi
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```
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#### Switch to root
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When asked, enter root password.
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```shell
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su -
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```
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### Step 27: make iptables rules persistent
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```shell
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iptables-save > /etc/iptables/rules.v4
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ip6tables-save > /etc/iptables/rules.v6
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```
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👍
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