SSH - Legacy Devices

Network, Security, SSH, System
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Intro

sometime, one have to access to old and legacy devices. they may do not support the current ciphers and key algorithms, so, we have to modify the “.ssh/config” File or provide some additional cli arguments.

If you have todo this regualary, you may wanna extend the current parameters with the legacy ones like this:

Backup old config

you never know ;)

mv /etc/ssh/ssh_config /etc/ssh/ssh_config-$(date "+%s")

Install Updated Version

you have to copy/paste as root

cat << 'EOF' > /etc/ssh/ssh_config
# Host *
#   ForwardAgent no
#   ForwardX11 no
#   PasswordAuthentication yes
#   HostbasedAuthentication no
#   GSSAPIAuthentication no
#   GSSAPIDelegateCredentials no
#   BatchMode no
#   CheckHostIP no
#   AddressFamily any
#   ConnectTimeout 0
#   StrictHostKeyChecking ask
#   IdentityFile ~/.ssh/id_rsa
#   IdentityFile ~/.ssh/id_dsa
#   IdentityFile ~/.ssh/id_ecdsa
#   IdentityFile ~/.ssh/id_ed25519
#   Port 22
#   Ciphers aes128-ctr,aes192-ctr,aes256-ctr,aes128-cbc,3des-cbc
#   MACs hmac-md5,hmac-sha1,[email protected]
#   EscapeChar ~
#   Tunnel no
#   TunnelDevice any:any
#   PermitLocalCommand no
#   VisualHostKey no
#   ProxyCommand ssh -q -W %h:%p gateway.example.com
#   RekeyLimit 1G 1h
#   UserKnownHostsFile ~/.ssh/known_hosts.d/%k
Host *
    SendEnv LANG LC_*
    KexAlgorithms 	+diffie-hellman-group1-sha1
    HostKeyAlgorithms	+ssh-dss
    Ciphers		+aes128-cbc
EOF

and now, you should be able to connect to even older devices via ssh.

Any Comments ?

sha256: b12d621fb74e731a54162a3f4c63f8d0853bddbb5504c50bcabeccaace597612