SSH/Public Key Authentication

RSA

#################### CLIENT SIDE ####################
# generating a new ssh key and adding it to the ssh client
# https://gist.github.com/shahedhossain/7d91028ba1eb9c56049ea421a12e76fd

# ssh key generation for chorke
ssh-keygen -t rsa -b 4096 -C "user@rpi.chorke.org"
# Generating public/private rsa key pair.
# Enter a file in which to save the key (/Users/user/.ssh/id_rsa): [Press enter]
# Enter passphrase (empty for no passphrase): [Type a passphrase]
# Enter same passphrase again: [Type passphrase again]

# rpi_chorke_rsa add to ~/.ssh/config
Host rpi.chorke.org
     HostName 139.59.51.80
     # PreferredAuthentications publickey
     IdentityFile ~/.ssh/rpi_chorke_rsa
     Port 4321

# copy root/misc public key to ~/.ssh/authorized_keys for each users
ssh-copy-id -i ~/.ssh/rpi_chorke_rsa.pub root@139.59.51.80 -p 4321
ssh-copy-id -i ~/.ssh/rpi_chorke_rsa.pub misc@139.59.51.80 -p 4321

#################### SERVER SIDE ####################
# for disable password authentication
# & enable public key authentication
# edit by /etc/ssh/sshd_config
PasswordAuthentication no
PubkeyAuthentication yes

# after edit save & exit restart sshd
# to update sshd configuration
# systemctl restart sshd
service sshd restart

#################### CLIENT SIDE ####################
# root user public key
ssh root@rpi.chorke.org
# Enter passphrase for key '/Users/user/.ssh/rpi_chorke_rsa':

# misc user public key
ssh misc@rpi.chorke.org
# Enter passphrase for key '/Users/user/.ssh/rpi_chorke_rsa':

#################### CLIENT SIDE ####################
# root user password disabled
ssh root@139.59.51.80 -p 4321
# root@139.59.51.80: Permission denied (publickey,gssapi-keyex,gssapi-with-mic).

# misc user password disabled
ssh misc@139.59.51.80 -p 4321
# user@139.59.51.80: Permission denied (publickey,gssapi-keyex,gssapi-with-mic).

RSA » Temp Key

---

TMP_PUBLIC_KEY=$(mktemp -u)
TMP_PRIVATE_KEY=$(mktemp -u)
ssh-keygen -t rsa -b 4096 -C "academia@chorke.org" -N "" -q -f ${TMP_PRIVATE_KEY}
ssh-keygen -y -f ${TMP_PRIVATE_KEY} > ${TMP_PUBLIC_KEY}

export SSH_PRIVATE_KEY="$(cat ${TMP_PRIVATE_KEY})"
export SSH_PUBLIC_KEY="$(cat ${TMP_PUBLIC_KEY})"
rm ${TMP_PRIVATE_KEY} ${TMP_PUBLIC_KEY}

echo && echo "${SSH_PRIVATE_KEY}"
echo && echo "${SSH_PUBLIC_KEY}" && echo

EdDSA

ssh-keygen -t ed25519 -C "<mail.id>@chorke.org"
ssh-keygen -t ed25519 -C "<mail.id>@chorke.org" -f ~/.ssh/id_ed25519
ssh-keygen -t ed25519 -C "<mail.id>@chorke.org" -f ~/.ssh/cid.chorke.org_ed25519

chmod 600 ~/.ssh/id_ed25519
chmod 644 ~/.ssh/id_ed25519.pub

chmod 600 ~/.ssh/cid.chorke.org_ed25519
chmod 644 ~/.ssh/cid.chorke.org_ed25519.pub

EdDSA » Temp Key

---

TMP_PUBLIC_KEY=$(mktemp -u)
TMP_PRIVATE_KEY=$(mktemp -u)
ssh-keygen -t ed25519 -C "academia@chorke.org" -N "" -q -f ${TMP_PRIVATE_KEY}
ssh-keygen -y -f ${TMP_PRIVATE_KEY} > ${TMP_PUBLIC_KEY}

export SSH_PRIVATE_KEY="$(cat ${TMP_PRIVATE_KEY})"
export SSH_PUBLIC_KEY="$(cat ${TMP_PUBLIC_KEY})"
rm ${TMP_PRIVATE_KEY} ${TMP_PUBLIC_KEY}

echo && echo "${SSH_PRIVATE_KEY}"
echo && echo "${SSH_PUBLIC_KEY}" && echo

Too Many Auth

too many authentication failures issue ssh -o PreferredAuthentications=password ${USER}@academia.local ssh -o IdentityAgent=none ${USER}@academia.local ssh -o IdentitiesOnly=yes ${USER}@academia.local

Host *.local IdentityAgent none IdentitiesOnly yes PreferredAuthentications password

Host 10.19.83.* IdentityAgent none IdentitiesOnly yes PreferredAuthentications password

Immutable » Authorization » Key

Linux » Immutable » authorized_keys
sudo chattr +i /home/academia/.ssh/authorized_keys #Immutable sudo chattr -i /home/academia/.ssh/authorized_keys # Mutable

Playground

cat << EXE | sudo bash sed 's|#PasswordAuthentication yes|PasswordAuthentication no|' -i /etc/ssh/sshd_config sed 's|#PubkeyAuthentication yes|PubkeyAuthentication yes|' -i /etc/ssh/sshd_config sed 's|#PermitEmptyPasswords no|PermitEmptyPasswords no|' -i /etc/ssh/sshd_config sed 's|#PermitRootLogin yes|PermitRootLogin no|' -i /etc/ssh/sshd_config systemctl restart ssh EXE		cat << EXE | sudo bash sshd -T | grep -i PasswordAuthentication sshd -T | grep -i PubkeyAuthentication sshd -T | grep -i PermitEmptyPasswords sshd -T | grep -i PermitRootLogin systemctl status ssh EXE

References

SSH server » Ubuntu » Change the default port Fedora SSH Client Public Key Authentication SSH Keys » RSA, DSA, ECDSA vs EdDSA Raspberry Pi Public Key Authentication Bastion SSH Tunneling