Passwordless SSH HowTo: Difference between revisions

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It's possible to use SSH to connect to your LWP directly. To connect to any LWP from outside the university network we require 2 factor authentication. This is achieved by requiring a password and a ssh key to login.<br>
It's possible to use SSH to connect from one LWP to another without using a password.<br>
We have a login server available to access your home directory, so you don't have to leave your own PC turned on. It's not a big machine, so don't use it to do your work on or you'll bother other users trying to access their files.<br>
We have a login server available to access your home directory, so you don't have to leave your own PC turned on. It's not a big machine, so don't use it to do your work on or you'll bother other users trying to access their files.<br>
<br>
<br>
The login server '''ssh-hostkeys''':<br>
The login server '''ssh-hostkeys''':<br>
256 SHA256:AJ8LcLyE0+my7uUW24A5iZ4Sr/7wU/KdK6l72A69T80 '''ssh.lwp.rug.nl''' (ECDSA)<br>
2048 SHA256:BqwCk82bRDxY3YLkumDcr8d0RKExSCX+zbsgdDyfF4w '''ssh.lwp.rug.nl''' (RSA)<br>
2048 SHA256:Zg6Z6ULOPP/991wsBe0ioMD2lENX4ewYMgTS90Hky/M '''ssh.lwp.rug.nl''' (RSA)<br>
256 SHA256:MfSPCbM20GbH+zMDUAEFzk80vTxF2890ch2EQJjEi3o '''ssh.lwp.rug.nl''' (ED25519)<br>
256 SHA256:YeSHwEfASFD5EckDwl2X2rbmhDtZ12+5HCOzvG9n6BI '''ssh.lwp.rug.nl''' (ED25519)<br>
256 SHA256:Fck7jcOsqDtqcCFncx144z2tt12oMWXD4Jiz0LJbapw '''ssh.lwp.rug.nl''' (ECDSA)<br>
<br>
<br>
== Connecting to the LWP from home with SSH.==
== Connecting to another LWP with SSH.==
You can replace '''ssh.lwp.rug.nl''' with the hostname of the machine you're trying to connect to.<br>
Replace '''ssh.lwp.rug.nl''' with the hostname or ip-address of the machine you're trying to connect to.<br>
If you already have a ssh key pair you want to use, you can skip creating a new key pair.<br>
===Add your p-number to the allowed users list===
=== Create a new SSH key pair ===
Add your p-number to the file /etc/users_allowed_ssh.
Create a key pair using the following command:
===Create a new SSH key pair===
Create a key pair using the following command:<br>
   ssh-keygen -t rsa -b 4096 -C "LWP" -f ~/.ssh/lwp_rsa
   ssh-keygen -t rsa -b 4096 -C "LWP" -f ~/.ssh/lwp_rsa
If you don't work with linux you can go to https://vlwp.rug.nl/, login with your RUG account and do it there.<br>
''Note: You can enter any comment with the “-C” option, e.g. username@hostname, so you can easily see what you're using the key for. The “-C” option is not mandatory.''<br>


''Note: You can enter a comment with the “-C” option, e.g. username@hostname, so you can easily see what you're using the key for. The “-C” option is not mandatory.''
===Add your public key to the authorized_keys file===
To allow your account to login to the LWP you'll have to add your public key to a authorized_keys file:<br>
  cat ~/.ssh/lwp_rsa.pub >> ~/.ssh/authorized_keys
''Note: This can only be done if you're logged in to a LWP; Use https://vlwp.rug.nl/ if you are not physically on a LWP.


#2 Add your public key to the login server.
===Set up your own LWP===
This can only be done from a LWP!
Use a USB drive to transfer your key pair to your own system securely.<br>
To set up your account for use with lwp-ssh.service.rug.nl you'll first have to login to any LWP and access the login server from there:
  cp ~/.ssh/lwp_rsa* /media/'''<your usb device>'''/
ssh lwp-ssh.service.rug.nl
Copy your key pair to your home directory:<br>
cat ~/.ssh/s1234567_lwp_rsa.pub >> /var/lwp/ssh/s1234567/authorized_keys
  mkdir ~/.ssh
 
  cp /media/'''<your usb device>'''/lwp_rsa* ~/.ssh/
#3 Set up your own system
Set the correct permissions:<br>
Copy your key pair to a USB drive to take home. Don't use e-mail unless you're able to encrypt it!
  chmod 0700 ~/.ssh
 
  chmod 0600 ~/.ssh/lwp_rsa
On your own system, copy your key pair to wherever you find convenient (I assume the default here). Set the correct permissions and connect to the login server using the following commands:
Try the connection:
chmod 0700 ~/.ssh
  ssh -i ~/.ssh/lwp_rsa '''<username>'''@ssh.lwp.rug.nl or hostname or ip-address
chmod 0600 ~/.ssh/s1234567_lwp_rsa
Make your life easier by creating a '''~/.ssh/config''' file and adding the following:
ssh -k -i ~/.ssh/s1234567_lwp_rsa s1234567@lwp-ssh.service.rug.nl
  host other-lwp
 
  user '''<username>'''
Or you can configure your ~/.ssh/config file and connect with one simple command. Add the following lines (with your own information) to ~/.ssh/config:
  IdentityFile ~/.ssh/lwp_rsa
  host lwp-ssh
  user s1234567
  IdentityFile ~/.ssh/s1234567_lwp_rsa
  ForwardX11 yes
  ForwardX11 yes
  HostName lwp-ssh.service.rug.nl
  HostName ssh.lwp.rug.nl or hostname or ip-address
Then connect with:
Then connect with:
  ssh lwp-ssh
  ssh other-lwp
 
and you should find yourself in your home directory.
Enter your password and you should find yourself in your home dir.

Latest revision as of 12:40, 28 August 2023

It's possible to use SSH to connect from one LWP to another without using a password.
We have a login server available to access your home directory, so you don't have to leave your own PC turned on. It's not a big machine, so don't use it to do your work on or you'll bother other users trying to access their files.

The login server ssh-hostkeys:
2048 SHA256:BqwCk82bRDxY3YLkumDcr8d0RKExSCX+zbsgdDyfF4w ssh.lwp.rug.nl (RSA)
256 SHA256:MfSPCbM20GbH+zMDUAEFzk80vTxF2890ch2EQJjEi3o ssh.lwp.rug.nl (ED25519)
256 SHA256:Fck7jcOsqDtqcCFncx144z2tt12oMWXD4Jiz0LJbapw ssh.lwp.rug.nl (ECDSA)

Connecting to another LWP with SSH.

Replace ssh.lwp.rug.nl with the hostname or ip-address of the machine you're trying to connect to.

Add your p-number to the allowed users list

Add your p-number to the file /etc/users_allowed_ssh.

Create a new SSH key pair

Create a key pair using the following command:

 ssh-keygen -t rsa -b 4096 -C "LWP" -f ~/.ssh/lwp_rsa

If you don't work with linux you can go to https://vlwp.rug.nl/, login with your RUG account and do it there.
Note: You can enter any comment with the “-C” option, e.g. username@hostname, so you can easily see what you're using the key for. The “-C” option is not mandatory.

Add your public key to the authorized_keys file

To allow your account to login to the LWP you'll have to add your public key to a authorized_keys file:

 cat ~/.ssh/lwp_rsa.pub >> ~/.ssh/authorized_keys

Note: This can only be done if you're logged in to a LWP; Use https://vlwp.rug.nl/ if you are not physically on a LWP.

Set up your own LWP

Use a USB drive to transfer your key pair to your own system securely.

 cp ~/.ssh/lwp_rsa* /media/<your usb device>/

Copy your key pair to your home directory:

 mkdir ~/.ssh
 cp /media/<your usb device>/lwp_rsa* ~/.ssh/

Set the correct permissions:

 chmod 0700 ~/.ssh
 chmod 0600 ~/.ssh/lwp_rsa

Try the connection: 

 ssh -i ~/.ssh/lwp_rsa <username>@ssh.lwp.rug.nl or hostname or ip-address

Make your life easier by creating a ~/.ssh/config file and adding the following: 

host other-lwp
user <username>
IdentityFile ~/.ssh/lwp_rsa
ForwardX11 yes
HostName ssh.lwp.rug.nl or hostname or ip-address

Then connect with: 

ssh other-lwp

and you should find yourself in your home directory.

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