Updated guide to ed25519, Debian 11 and nftables

This commit is contained in:
Sun Knudsen 2022-01-08 07:42:53 -05:00
parent 9db6a0ffbf
commit 81e2853f89
No known key found for this signature in database
GPG Key ID: 02C43AD072D57783

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@ -36,33 +36,33 @@ $ mkdir ~/.ssh
$ cd ~/.ssh
$ ssh-keygen -t rsa -C "pi"
Generating public/private rsa key pair.
Enter file in which to save the key (/Users/sunknudsen/.ssh/id_rsa): pi
$ ssh-keygen -t ed25519 -C "pi"
Generating public/private ed25519 key pair.
Enter file in which to save the key (/Users/sunknudsen/.ssh/id_ed25519): pi
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in pi.
Your public key has been saved in pi.pub.
The key fingerprint is:
SHA256:NZkr0Bmu6tpQfDp2GHTIPyBz253uZk/gOmoqzEszGM0 pi
SHA256:U3hEUQC0GAyCOPaks1Xv04ouoN9ezwtfK4CnUxKqAms pi
The key's randomart image is:
+---[RSA 3072]----+
| . |
| . . o o o |
| o * o + = |
| o * * + o o |
|. E = * S . |
|.. . * + o |
|++. * . o . |
|ooo=.o.oo. |
| o+++..+... |
+--[ED25519 256]--+
|... .o..oo=+. |
|+. o ..o + |
|..+ . o o o |
| o o. . o |
| +. o. S |
|.o. o +o o |
|oo. =+.o . |
|=E ooo *.. . |
|o...=o =o. |
+----[SHA256]-----+
$ cat pi.pub
ssh-rsa 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 pi
ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIHLwQ2fk5VvoKJ6PNdJfmtum6fTAIn7xG5vbFm0YjEGY pi
```
### Step 2: generate heredoc (the output of following command will be used at [step 10](#step-10-configure-pi-ssh-authorized-keys))
### Step 2: generate heredoc (the output of following command will be used at [step 11](#step-11-configure-pi-ssh-authorized-keys))
```shell
cat << EOF
@ -78,47 +78,48 @@ EOF
> WARNING: DO NOT RUN THE FOLLOWING COMMANDS AS-IS.
Run `diskutil list` to find disk ID of SD card to overwrite with “Raspberry Pi OS Lite” (`disk2` in the following example).
Run `diskutil list` to find disk ID of SD card to overwrite with “Raspberry Pi OS Lite” (`disk4` in the following example).
Replace `diskn` and `rdiskn` with disk ID of SD card (`disk2` and `rdisk2` in the following example) and `2021-03-04-raspios-buster-armhf-lite.img` with current image.
Replace `diskn` and `rdiskn` with disk ID of SD card (`disk4` and `rdisk4` in the following example) and `2021-10-30-raspios-bullseye-armhf-lite.img` with current image.
```console
$ diskutil list
/dev/disk0 (internal, physical):
/dev/disk0 (internal):
#: TYPE NAME SIZE IDENTIFIER
0: GUID_partition_scheme *500.3 GB disk0
1: EFI EFI 209.7 MB disk0s1
2: Apple_APFS Container disk1 500.1 GB disk0s2
0: GUID_partition_scheme 500.3 GB disk0
1: Apple_APFS_ISC 524.3 MB disk0s1
2: Apple_APFS Container disk3 494.4 GB disk0s2
3: Apple_APFS_Recovery 5.4 GB disk0s3
/dev/disk1 (synthesized):
/dev/disk3 (synthesized):
#: TYPE NAME SIZE IDENTIFIER
0: APFS Container Scheme - +500.1 GB disk1
0: APFS Container Scheme - +494.4 GB disk3
Physical Store disk0s2
1: APFS Volume Macintosh HD - Data 340.9 GB disk1s1
2: APFS Volume Preboot 85.9 MB disk1s2
3: APFS Volume Recovery 529.0 MB disk1s3
4: APFS Volume VM 3.2 GB disk1s4
5: APFS Volume Macintosh HD 11.3 GB disk1s5
1: APFS Volume Macintosh HD 15.3 GB disk3s1
2: APFS Snapshot com.apple.os.update-... 15.3 GB disk3s1s1
3: APFS Volume Preboot 328.4 MB disk3s2
4: APFS Volume Recovery 815.1 MB disk3s3
5: APFS Volume Data 458.6 GB disk3s5
6: APFS Volume VM 2.1 GB disk3s6
/dev/disk2 (internal, physical):
/dev/disk4 (external, physical):
#: TYPE NAME SIZE IDENTIFIER
0: FDisk_partition_scheme *15.9 GB disk2
1: Windows_FAT_32 boot 268.4 MB disk2s1
2: Linux 15.7 GB disk2s2
0: FDisk_partition_scheme *15.9 GB disk4
1: Windows_NTFS Untitled 15.9 GB disk4s1
$ sudo diskutil unmount /dev/diskn
disk2 was already unmounted or it has a partitioning scheme so use "diskutil unmountDisk" instead
disk4 was already unmounted or it has a partitioning scheme so use "diskutil unmountDisk" instead
$ sudo diskutil unmountDisk /dev/diskn (if previous step fails)
Unmount of all volumes on disk2 was successful
Unmount of all volumes on disk4 was successful
$ sudo dd bs=1m if=$HOME/Downloads/2021-03-04-raspios-buster-armhf-lite.img of=/dev/rdiskn
1772+0 records in
1772+0 records out
1858076672 bytes transferred in 40.449002 secs (45936280 bytes/sec)
$ sudo dd bs=1m if=$HOME/Downloads/2021-10-30-raspios-bullseye-armhf-lite.img of=/dev/rdiskn
1864+0 records in
1864+0 records out
1954545664 bytes transferred in 37.454965 secs (52183887 bytes/sec)
$ sudo diskutil unmountDisk /dev/diskn
Unmount of all volumes on disk2 was successful
Unmount of all volumes on disk4 was successful
```
### Step 5: log in as pi (using keyboard) and change password using `passwd`
@ -160,47 +161,15 @@ ip a
### Step 9: log in to Raspberry Pi over SSH
Replace `10.0.1.248` with IP of Raspberry Pi.
Replace `10.0.1.181` with IP of Raspberry Pi.
When asked for passphrase, enter passphrase from [step 5](#step-5-log-in-as-pi-using-keyboard-and-change-password-using-passwd).
```shell
ssh pi@10.0.1.248
ssh pi@10.0.1.181
```
### Step 10: configure pi SSH authorized keys
#### Create `.ssh` directory
```shell
mkdir ~/.ssh
```
#### Create `~/.ssh/authorized_keys` using heredoc generated at [step 2](#step-2-generate-heredoc-the-output-of-following-command-will-be-used-at-step-10)
```shell
cat << "_EOF" > ~/.ssh/authorized_keys
ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABgQDCzQpX9uqDP8L2gSZNJxYEi04Y1pZWz28v4zANY5dU6M35OFzXZcRcBqi2ZxiQofgxRrX9QlAcmcPFz8/CkpPw2WgQTflm+46ZrVEZcwwGwJsJwm7QVLQLd44/xtejEvMjzsuYDjJ1q4WhEvMSleTfOrix4yP0mjn83Zk1l6AMxR5J8DDumiHsGSYfcp+1XS9x4r4HP0mS2RpIy3rcoxLoJaYEKvVTj9qdvPMK7SDymZcvuBsgObEARVr77q4qhUfTP+xR91hHNEYD9FnCHF3qQBzlTlmTwpwhH6vOdWE3uUXCug9Ugw42Zj3PW0zd5rQ7EEpD9SDLbUqajpn2M5AlhkS9OrLpnIptocetRKNI9HzyAV1KqdNiQeL7/59d4y+HuZ9y032SaNzR1fw0nYMoHzTN9d+zPvziDZ183/pwtEXZNVVGzYO1r56n3S4vLx8YCpYqiHYVQVDF8aweoHYs3dAGAfPxmQ85+45UKpFR18XSGCqCO2fwbyTGDhkxCzU= pi
_EOF
```
### Step 11: log out
```shell
exit
```
### Step 12: log in
Replace `10.0.1.248` with IP of Raspberry Pi.
When asked for passphrase, enter passphrase from [step 1](#step-1-create-ssh-key-pair-on-macos).
```shell
ssh pi@10.0.1.248 -i ~/.ssh/pi
```
### Step 13: disable pi Bash history
### Step 10: disable pi Bash history
```shell
sed -i -E 's/^HISTSIZE=/#HISTSIZE=/' ~/.bashrc
@ -210,46 +179,59 @@ history -c; history -w
source ~/.bashrc
```
### Step 14: configure pi `.vimrc`
### Step 11: configure pi SSH authorized keys
#### Create `.ssh` directory
```shell
cat << "EOF" > ~/.vimrc
set encoding=UTF-8
set termencoding=UTF-8
set nocompatible
set backspace=indent,eol,start
set autoindent
set tabstop=2
set shiftwidth=2
set expandtab
set smarttab
set ruler
set paste
syntax on
EOF
mkdir ~/.ssh
```
### Step 15: switch to root
#### Create `~/.ssh/authorized_keys` using heredoc generated at [step 2](#step-2-generate-heredoc-the-output-of-following-command-will-be-used-at-step-11)
```shell
cat << "_EOF" > ~/.ssh/authorized_keys
ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIHLwQ2fk5VvoKJ6PNdJfmtum6fTAIn7xG5vbFm0YjEGY pi
_EOF
```
### Step 12: log out
```shell
exit
```
### Step 13: log in
Replace `10.0.1.181` with IP of Raspberry Pi.
When asked for passphrase, enter passphrase from [step 1](#step-1-create-ssh-key-pair-on-macos).
```shell
ssh pi@10.0.1.181 -i ~/.ssh/pi
```
### Step 14: switch to root
```shell
sudo su -
```
### Step 15: disable root Bash history
```shell
echo "HISTFILESIZE=0" >> ~/.bashrc
history -c; history -w
source ~/.bashrc
```
### Step 16: disable pi sudo `nopassword` “feature”
```shell
rm /etc/sudoers.d/010_*
```
### Step 17: disable root Bash history
```shell
echo "HISTFILESIZE=0" >> ~/.bashrc
history -c; history -w
source ~/.bashrc
```
### Step 18: set root password
### Step 17: set root password
When asked for password, use output from `openssl rand -base64 24` (and store password in password manager).
@ -260,26 +242,7 @@ Retype new password:
passwd: password updated successfully
```
### Step 19: configure root `.vimrc`
```shell
cat << "EOF" > ~/.vimrc
set encoding=UTF-8
set termencoding=UTF-8
set nocompatible
set backspace=indent,eol,start
set autoindent
set tabstop=2
set shiftwidth=2
set expandtab
set smarttab
set ruler
set paste
syntax on
EOF
```
### Step 20: disable root login and password authentication
### Step 18: disable root login and password authentication
```shell
sed -i -E 's/^(#)?PermitRootLogin (prohibit-password|yes)/PermitRootLogin no/' /etc/ssh/sshd_config
@ -287,9 +250,9 @@ sed -i -E 's/^(#)?PasswordAuthentication yes/PasswordAuthentication no/' /etc/ss
systemctl restart ssh
```
### Step 21: disable Bluetooth and Wi-Fi
### Step 19: disable Bluetooth and Wi-Fi
> Heads-up: will take effect after reboot.
> Heads-up: step will take effect after reboot.
#### Disable Bluetooth
@ -303,63 +266,9 @@ echo "dtoverlay=disable-bt" >> /boot/config.txt
echo "dtoverlay=disable-wifi" >> /boot/config.txt
```
### Step 22: update APT index, install `iptables-persistent` and Vim and upgrade system
### Step 20: configure sysctl (if network is IPv4-only)
#### Update APT index
```shell
apt update
```
#### Install `iptables-persistent` and Vim
When asked to save current IPv4 or IPv6 rules, answer “Yes”.
```shell
apt install -y iptables-persistent vim
```
#### Upgrade packages
> Heads-up: if asked which version of `/etc/ssh/sshd_config` to keep, select “keep the local version currently installed”.
```shell
apt upgrade -y
```
### Step 23: reboot
```shell
systemctl reboot
```
### Step 24: log in
Replace `10.0.1.248` with IP of Raspberry Pi.
When asked for passphrase, enter passphrase from [step 1](#step-1-create-ssh-key-pair-on-macos).
```shell
ssh pi@10.0.1.248 -i ~/.ssh/pi
```
### Step 25: switch to root
```shell
sudo su -
```
### Step 26: set timezone (the following is for Montreal time)
See https://en.wikipedia.org/wiki/List_of_tz_database_time_zones
```shell
timedatectl set-timezone America/Montreal
```
### Step 27: configure sysctl (if network is IPv4-only)
> Heads-up: only run the following if network is IPv4-only.
> Heads-up: only run following if network is IPv4-only.
```shell
cp /etc/sysctl.conf /etc/sysctl.conf.backup
@ -371,70 +280,64 @@ EOF
sysctl -p
```
### Step 28: configure firewall
### Step 21: enable nftables and configure firewall rules
#### Enable nftables
```shell
iptables -N SSH_BRUTE_FORCE_MITIGATION
iptables -A SSH_BRUTE_FORCE_MITIGATION -m recent --name SSH --set
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]: "
iptables -A SSH_BRUTE_FORCE_MITIGATION -m recent --name SSH --update --seconds 300 --hitcount 10 -j DROP
iptables -A SSH_BRUTE_FORCE_MITIGATION -j ACCEPT
iptables -A INPUT -i lo -j ACCEPT
iptables -A INPUT -p tcp --dport 22 --syn -m conntrack --ctstate NEW -j SSH_BRUTE_FORCE_MITIGATION
iptables -A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
iptables -A OUTPUT -o lo -j ACCEPT
iptables -A OUTPUT -p tcp --dport 53 -m state --state NEW -j ACCEPT
iptables -A OUTPUT -p udp --dport 53 -m state --state NEW -j ACCEPT
iptables -A OUTPUT -p tcp --dport 80 -m state --state NEW -j ACCEPT
iptables -A OUTPUT -p udp --dport 123 -m state --state NEW -j ACCEPT
iptables -A OUTPUT -p tcp --dport 443 -m state --state NEW -j ACCEPT
iptables -A OUTPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
iptables -P FORWARD DROP
iptables -P INPUT DROP
iptables -P OUTPUT DROP
systemctl enable nftables
systemctl start nftables
```
#### Configure firewall rules
```shell
nft flush ruleset
nft add table ip firewall
nft add chain ip firewall input { type filter hook input priority 0 \; policy drop \; }
nft add rule ip firewall input iif lo accept
nft add rule ip firewall input iif != lo ip daddr 127.0.0.0/8 drop
nft add rule ip firewall input tcp dport ssh accept
nft add rule ip firewall input ct state established,related accept
nft add chain ip firewall forward { type filter hook forward priority 0 \; policy drop \; }
nft add chain ip firewall output { type filter hook output priority 0 \; policy drop \; }
nft add rule ip firewall output oif lo accept
nft add rule ip firewall output tcp dport { http, https } accept
nft add rule ip firewall output udp dport { domain, ntp } accept
nft add rule ip firewall output ct state established,related accept
```
If network is IPv4-only, run:
```shell
ip6tables -P FORWARD DROP
ip6tables -P INPUT DROP
ip6tables -P OUTPUT DROP
nft add table ip6 firewall
nft add chain ip6 firewall input { type filter hook input priority 0 \; policy drop \; }
nft add chain ip6 firewall forward { type filter hook forward priority 0 \; policy drop \; }
nft add chain ip6 firewall output { type filter hook output priority 0 \; policy drop \; }
```
If network is dual stack (IPv4 + IPv6) run:
```shell
ip6tables -A INPUT -i lo -j ACCEPT
ip6tables -A INPUT -p ipv6-icmp --icmpv6-type destination-unreachable -j ACCEPT
ip6tables -A INPUT -p ipv6-icmp --icmpv6-type packet-too-big -j ACCEPT
ip6tables -A INPUT -p ipv6-icmp --icmpv6-type time-exceeded -j ACCEPT
ip6tables -A INPUT -p ipv6-icmp --icmpv6-type parameter-problem -j ACCEPT
ip6tables -A INPUT -p ipv6-icmp --icmpv6-type router-advertisement -m hl --hl-eq 255 -j ACCEPT
ip6tables -A INPUT -p ipv6-icmp --icmpv6-type neighbor-solicitation -m hl --hl-eq 255 -j ACCEPT
ip6tables -A INPUT -p ipv6-icmp --icmpv6-type neighbor-advertisement -m hl --hl-eq 255 -j ACCEPT
ip6tables -A INPUT -p ipv6-icmp --icmpv6-type redirect -m hl --hl-eq 255 -j ACCEPT
ip6tables -A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
ip6tables -A OUTPUT -o lo -j ACCEPT
ip6tables -A OUTPUT -p ipv6-icmp --icmpv6-type destination-unreachable -j ACCEPT
ip6tables -A OUTPUT -p ipv6-icmp --icmpv6-type packet-too-big -j ACCEPT
ip6tables -A OUTPUT -p ipv6-icmp --icmpv6-type time-exceeded -j ACCEPT
ip6tables -A OUTPUT -p ipv6-icmp --icmpv6-type parameter-problem -j ACCEPT
ip6tables -A OUTPUT -p ipv6-icmp --icmpv6-type router-solicitation -m hl --hl-eq 255 -j ACCEPT
ip6tables -A OUTPUT -p ipv6-icmp --icmpv6-type neighbour-solicitation -m hl --hl-eq 255 -j ACCEPT
ip6tables -A OUTPUT -p ipv6-icmp --icmpv6-type neighbour-advertisement -m hl --hl-eq 255 -j ACCEPT
ip6tables -A OUTPUT -p tcp --dport 53 -m state --state NEW -j ACCEPT
ip6tables -A OUTPUT -p udp --dport 53 -m state --state NEW -j ACCEPT
ip6tables -A OUTPUT -p tcp --dport 80 -m state --state NEW -j ACCEPT
ip6tables -A OUTPUT -p udp --dport 123 -m state --state NEW -j ACCEPT
ip6tables -A OUTPUT -p tcp --dport 443 -m state --state NEW -j ACCEPT
ip6tables -A OUTPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
ip6tables -P FORWARD DROP
ip6tables -P INPUT DROP
ip6tables -P OUTPUT DROP
nft add table ip6 firewall
nft add chain ip6 firewall input { type filter hook input priority 0\; policy drop\; }
nft add rule ip6 firewall input iif lo accept
nft add rule ip6 firewall input iif != lo ip6 daddr ::1 drop
nft add rule ip6 firewall input meta l4proto ipv6-icmp icmpv6 type { destination-unreachable, packet-too-big, time-exceeded, parameter-problem } accept
nft add rule ip6 firewall input meta l4proto ipv6-icmp icmpv6 type { nd-router-advert, nd-neighbor-solicit, nd-neighbor-advert, nd-redirect } ip6 hoplimit 255 accept
nft add rule ip6 firewall input tcp dport ssh accept
nft add rule ip6 firewall input ct state established,related accept
nft add chain ip6 firewall forward { type filter hook forward priority 0\; policy drop\; }
nft add chain ip6 firewall output { type filter hook output priority 0\; policy drop\; }
nft add rule ip6 firewall output oif lo accept
nft add rule ip6 firewall output meta l4proto ipv6-icmp icmpv6 type { destination-unreachable, packet-too-big, time-exceeded, parameter-problem } accept
nft add rule ip6 firewall output meta l4proto ipv6-icmp icmpv6 type { nd-router-advert, nd-neighbor-solicit, nd-neighbor-advert } ip6 hoplimit 255 accept
nft add rule ip6 firewall output tcp dport { http, https } accept
nft add rule ip6 firewall output udp dport { domain, ntp } accept
nft add rule ip6 firewall output ct state related,established accept
```
### Step 29: log out and log in to confirm firewall didnt block SSH
### Step 22: log out and log in to confirm firewall is not blocking SSH
#### Log out
@ -445,23 +348,59 @@ exit
#### Log in
Replace `10.0.1.248` with IP of Raspberry Pi.
Replace `10.0.1.181` with IP of Raspberry Pi.
```shell
ssh pi@10.0.1.248 -i ~/.ssh/pi
ssh pi@10.0.1.181 -i ~/.ssh/pi
```
### Step 30: switch to root
### Step 23: switch to root
```shell
sudo su -
```
### Step 31: make firewall rules persistent
### Step 24: make firewall rules persistent
```shell
iptables-save > /etc/iptables/rules.v4
ip6tables-save > /etc/iptables/rules.v6
cat << "EOF" > /etc/nftables.conf
#!/usr/sbin/nft -f
flush ruleset
EOF
```
```shell
nft list ruleset >> /etc/nftables.conf
```
### Step 25: set timezone
See https://en.wikipedia.org/wiki/List_of_tz_database_time_zones
```shell
timedatectl set-timezone America/Montreal
```
### Step 26: disable swap
```shell
systemctl disable dphys-swapfile
```
### Step 27: update APT index and upgrade system
#### Update APT index
```shell
apt update
```
#### Upgrade packages
```shell
apt upgrade -y
```
👍