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| − | =Installation=
| + | [[Category:Linux]] |
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| − | By default Debian | Ubuntu doesn't include any SSH server.
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| − | <syntaxhighlight lang="bash">
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| − | apt-get install ssh openssh-server
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| − | </syntaxhighlight>
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| | | | |
| | + | =SSH client= |
| | | | |
| | | | |
| | + | ==Linux== |
| | | | |
| − | =SSH server configuration= | + | ===Standard login=== |
| − | | |
| − | | |
| − | Edit the configuration file:
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| | | | |
| | <syntaxhighlight lang="bash"> | | <syntaxhighlight lang="bash"> |
| − | vim /etc/ssh/sshd_config
| + | # syntax |
| − | </syntaxhighlight>
| + | ssh user@server -p portNumber |
| | | | |
| − | | + | # example |
| − | ==X11 forwarding==
| + | ssh root@daxiongmao.eu -p 4422 |
| − | | |
| − | In the configuration file, uncomment and set:
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| − | <syntaxhighlight lang="bash">
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| − | ForwardAgent yes
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| − | ForwardX11 yes
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| − | ForwardX11Trusted yes
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| | </syntaxhighlight> | | </syntaxhighlight> |
| | | | |
| | | | |
| − | '''Enable | Disable the forwarding:'''
| + | ===Using RSA key=== |
| | | | |
| − | <syntaxhighlight lang="bash">
| + | Key points: |
| − | # This server doesn’t have a XServer. Therefore do not forward graphical data.
| + | * The key must belongs to the current user |
| − | X11Forwarding no
| + | * The key rights must be "500" |
| − | </syntaxhighlight>
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| | | | |
| | | | |
| − | ==Port(s) number==
| + | Then you can log-in using the following command: |
| − | | |
| − | You can listen on multiple port. Just do the following:
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| | | | |
| | <syntaxhighlight lang="bash"> | | <syntaxhighlight lang="bash"> |
| − | Port 22
| + | ssh -i Guillaume_OpenSSH.private -p 2200 guillaume@dev.daxiongmao.eu |
| − | Port 2200
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| | </syntaxhighlight> | | </syntaxhighlight> |
| | | | |
| | + | Where: |
| | + | * '''-i''' ''myFile'' = the private key you have to use |
| | + | * '''-p''' ''port'' = specific port number (if not default 22) |
| | | | |
| − | Security psycho mode:
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| | | | |
| − | <syntaxhighlight lang="bash">
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| − | # The default port SSH is 22. You may want to change that port to another one so your server will be more discreet.
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| − | # NB: if your server is hosted the provider might need access for maintenance purposes.
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| − | Port XXXXX
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| − | </syntaxhighlight>
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| | | | |
| − | | + | ===X11 forwarding=== |
| − | | |
| − | ==Restart SSH server== | |
| | | | |
| | <syntaxhighlight lang="bash"> | | <syntaxhighlight lang="bash"> |
| − | /etc/init.d/ssh restart
| + | ssh -X guillaume@nuc-media-center |
| | </syntaxhighlight> | | </syntaxhighlight> |
| | | | |
| | | | |
| − | | + | ♦ Note that the remote computer have X11 installed and X11 applications. |
| − | | |
| − | =Firewall=
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| − | | |
| − | See [[Firewall#SSH]]
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| − | | |
| − | | |
| − | | |
| − | =SSH server configuration - Authentication by Linux user login / password=
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| − | | |
| − | ==Principle==
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| − | | |
| − | This is the default authentication system.
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| − | | |
| − | | |
| − | Each user that has a '''local account on the server''' and member is allowed to access the SSH server with its login / password.
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| − | | |
| − | [[File:SSH server default auth.png|none|SSH default authentication system]]
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| − | | |
| − | | |
| − | | |
| − | ==Configuration changes==
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| − | | |
| − | <syntaxhighlight lang="bash">
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| − | vim /etc/ssh/sshd_config
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| − | </syntaxhighlight>
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| − | | |
| − | | |
| − | ===Protocol and password enforcement===
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| − | | |
| − | <syntaxhighlight lang="bash">
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| − | Protocol 2 # only use SSH v2
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| − | PermitRootLogin no # Avoid root connections
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| − | PermitEmptyPassword no # Forbidden user with empty passwords
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| − | </syntaxhighlight>
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| − | | |
| − | | |
| − | ===Login time===
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| − | | |
| − | <syntaxhighlight lang="bash">
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| − | # Time to log
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| − | LoginGraceTime 30
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| − | </syntaxhighlight>
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| − | | |
| − | | |
| − | ==Restart SSH server==
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| − | | |
| − | <syntaxhighlight lang="bash">
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| − | /etc/init.d/ssh restart
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| − | </syntaxhighlight>
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| − | | |
| − | | |
| − | | |
| − | | |
| − | | |
| − | =SSH server configuration - Authentication with RSA keys=
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| − | | |
| − | | |
| − | ==Introduction==
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| − | | |
| − | If you’d like to increase the authentication process you can use authentication by private/public key.
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| − | * Generate new private / public keys on your own computer
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| − | * Put the public key on the remote SSH server
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| − | * Only the person with the private key can be authenticate on the server
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| − | | |
| − | | |
| − | [[File:SSH_server_RSA_keys.png|none|SSH RSA authentication]]
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| − | | |
| − | | |
| − | | |
| − | For instance, this is how hosting company such as OVH can log on your system.
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| − | | |
| − | | |
| − | | |
| − | '''Security improvement: remove password authentication'''
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| − | | |
| − | When the key authentication is working you can remove the default access by login / password.
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| − | Then, only people with a valid private/public key pair can log in.
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| − | | |
| − | That way, there is no way for brute-force attacks to be successful, so your system is more secure.
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| − | | |
| − | | |
| − | | |
| − | ==Declare the public key on the server==
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| − | | |
| − | | |
| − | You have to:
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| − | * '''log in''' to your SSH server with the '''user that’s gonna use this key'''
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| − | * Go to '''user's home''' directory
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| − | * Create a '''.ssh''' folder (if there was none before).
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| − | | |
| − | <syntaxhighlight lang="bash">
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| − | cd ~
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| − | mkdir .ssh
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| − | cd .ssh
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| − | </syntaxhighlight>
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| − | | |
| − | | |
| − | Add the new ''public'' key to the list of allowed keys:
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| − | | |
| − | <syntaxhighlight lang="bash">
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| − | vim authorized_key2
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| − | </syntaxhighlight>
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| − | | |
| − | | |
| − | Prefix your key with:
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| − | * RSA: ssh-rsa
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| − | * DSA: ssh-dss
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| − | | |
| − | Then paste the public key in one line - the public key mustn't be change or separated in 2 lines!
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| − | | |
| − | | |
| − | <syntaxhighlight lang="bash">
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| − | # Example:
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| − | ssh-rsa AAAAB3NzaC1yc2EA[...]Lg5whU0zMuYE5IZu8ZudnP6ds= myname@example.com
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| − | ssh-dss AAAAB3NzaC1yc2EA[...]Lg5whU0zMuYE5IZu8ZudnP6ds= myname@example.com
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| − | </syntaxhighlight>
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| − | | |
| − | | |
| − | Adjust file rights, the ''authorized_keys2'' file must be write/readable only by that user
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| − | | |
| − | <syntaxhighlight lang="bash">
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| − | chmod 640 authorized_keys2
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| − | cd ..
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| − | chmod 700 .ssh
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| − | </syntaxhighlight>
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| − | | |
| − | | |
| − | ==Configuration changes==
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| − | | |
| − | <syntaxhighlight lang="bash">
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| − | vim /etc/ssh/sshd_config
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| − | </syntaxhighlight>
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| − | | |
| − | | |
| − | ===Allow empty password===
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| − | | |
| − | <syntaxhighlight lang="bash">
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| − | PermitEmptyPassword yes # allow empty password in favor of RSA keys
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| − | </syntaxhighlight>
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| − | | |
| − | | |
| − | | |
| − | ==Restart SSH server==
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| − | | |
| − | <syntaxhighlight lang="bash">
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| − | /etc/init.d/ssh restart
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| − | </syntaxhighlight>
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| − | =SSH server - Authentication using LDAP server=
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| − | | |
| − | Requirement: [[LDAP server]]
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| − | | |
| − | | |
| − | ==Principle==
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| − | | |
| − | The idea is to use a LDAP server to manage users and groups to ease the maintenance and administration.
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| − | | |
| − | * Only 1 group of users is allowed to connect
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| − | | |
| − | * Access can be dynamically and easily granted
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| − | | |
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| − | [[File:SSH_server_LDAP_user.png|none|SSH LDAP server authentication]]
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| − | ==Configuration==
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| − | !! TO BE DONE !!
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| − | =How-to generate private / public keys=
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| − | ==Linux==
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| − | ===Create key===
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| − | | |
| − | 1. Log-in with the user you want to use.
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| − | | |
| − | | |
| − | 2. Generate a pair of authentication keys. '''Do not enter a passphrase'''
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| − | | |
| − | <syntaxhighlight lang="bash">
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| − | # Generating public/private rsa key pair
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| − | ssh-keygen -t rsa
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| − | </syntaxhighlight>
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| − | | |
| − | >> Enter file in which to save the key: /home/''user''/'''.ssh'''/id_rsa
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| − | | |
| − | Log sample:
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| − | <syntaxhighlight lang="bash">
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| − | Created directory '/home/a/.ssh'.
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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 /home/a/.ssh/id_rsa.
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| − | Your public key has been saved in /home/a/.ssh/id_rsa.pub.
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| − | The key fingerprint is:
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| − | 3e:4f:05:79:3a:9f:96:7c:3b:ad:e9:58:37:bc:37:e4
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| − | </syntaxhighlight>
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| − | | |
| − | | |
| − | ===Convert OpenSSH key to Windows Putty===
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| − | | |
| − | See: http://meinit.nl/using-your-openssh-private-key-in-putty
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| − | | |
| − | ==Windows==
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| − | | |
| − | You can generate private / public keys with '''PuttyGen''' = Putty key generator.
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| − | | |
| − | | |
| − | [[File:SSH_putty_key_generator.png|none|puttyGen first step]]
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| − | | |
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| − | When the keys are OK, you have to enter a key pass-phrase. Your pass-phrase must be:
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| − | * long (> 15 characters)
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| − | * hard to guess
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| − | * with letters + signs + numbers
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| − | | |
| − | '''Reminder'''
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| − | | |
| − | how to choose your passphrase and protect it: http://www.alcf.anl.gov/resource-guides/user-authentication-policies
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| − | [[File:SSH_putty_key_generator_2.png|none|PuttyGen 2nd step]]
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| − | Then, save your keys!
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| − | You should be the only one to access the save location.
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| − | =Fail2ban=
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| − | | |
| − | see [[Fail2ban#SSH_configuration]]
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| − | =SSH client=
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| − | | |
| − | | |
| − | ==Linux==
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| − | ===Standard login===
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| − | | |
| − | <syntaxhighlight lang="bash">
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| − | # syntax
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| − | ssh user@server -p portNumber
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| − | | |
| − | # example
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| − | ssh root@daxiongmao.eu -p 4422
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| − | </syntaxhighlight>
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| − | | |
| − | | |
| − | ===Using RSA key===
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| | [[File:Putty_SSH_access_4.png|none|Putty SSH login step 4]] | | [[File:Putty_SSH_access_4.png|none|Putty SSH login step 4]] |
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| − | =References=
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| − |
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| − | Source:
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| − | * Public / private key theory: http://en.wikipedia.org/wiki/Public_Key_Cryptography
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| − | * http://www.howtoforge.com/ssh_key_based_logins_putty
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| − | Windows - putty software: http://www.chiark.greenend.org.uk/~sgtatham/putty/download.html
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| − | How to transform a SSH key into Windows Putty: http://meinit.nl/using-your-openssh-private-key-in-putty
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