Added SSH to Services chapter

docs/services.rst

@@ -1336,6 +1336,156 @@ After commit the resulting configuration will look like:
        }
    }
 
+SSH
+---
+
+Secure Shell (SSH_) is a cryptographic network protocol for operating network
+services securely over an unsecured network.[1] The standard TCP port for SSH
+is 22. The best known example application is for remote login to computer
+systems by users.
+
+SSH provides a secure channel over an unsecured network in a client-server
+architecture, connecting an SSH client application with an SSH server. Common
+applications include remote command-line login and remote command execution,
+but any network service can be secured with SSH. The protocol specification
+distinguishes between two major versions, referred to as SSH-1 and SSH-2.
+
+The most visible application of the protocol is for access to shell accounts
+on Unix-like operating systems, but it sees some limited use on Windows as
+well. In 2015, Microsoft announced that they would include native support for
+SSH in a future release.
+
+SSH was designed as a replacement for Telnet and for unsecured remote shell
+protocols such as the Berkeley rlogin, rsh, and rexec protocols. Those protocols
+send information, notably passwords, in plaintext, rendering them susceptible
+to interception and disclosure using packet analysis. The encryption used by
+SSH is intended to provide confidentiality and integrity of data over an
+unsecured network, such as the Internet.
+
+Configuration
+^^^^^^^^^^^^^
+
+Enabling SSH only requires you to add ``service ssh port NN``, where 'NN' is
+the port you want SSH to listen on. By default, SSH runs on port 22.
+
+.. code-block:: sh
+
+  set service ssh port 22
+
+Options
+*******
+
+* Listening address - Specify the IPv4/IPv6 listening address for connection
+  requests. Multiple ``listen-address`` nodes can be defined.
+
+  :code:`set service ssh listen-address <address>`
+
+* Allow ``root`` login, this can be set to allow ``root`` logins on SSH
+  connections, however it is not advisable to use this setting as this bears
+  serious security risks. The default system user posesses all required
+  privileges.
+
+  :code:`set service ssh allow-root`
+
+* Allowed ciphers - A number of allowed ciphers can be specified, use multiple
+  occurances to allow multiple ciphers.
+
+  :code:`set service ssh ciphers <cipher>`
+
+  Available ciphers:
+
+ * `3des-cbc`
+ * `aes128-cbc`
+ * `aes192-cbc`
+ * `aes256-cbc`
+ * `aes128-ctr`
+ * `aes192-ctr`
+ * `aes256-ctr`
+ * `arcfour128`
+ * `arcfour256`
+ * `arcfour`
+ * `blowfish-cbc`
+ * `cast128-cbc`
+
+* Disable password authentication - If SSH key authentication is set up,
+  password-based user authetication can be disabled. This hardens security!
+
+  :code:`set service ssh disable-password-authentication`
+
+* Disable host validation - Disable the host validation through reverse DNS
+  lookups.
+
+  :code:`set service ssh disable-host-validation`
+
+* MAC algorithms - Specifies the available MAC (message authentication code)
+  algorithms. The MAC algorithm is used in protocol version 2 for data
+  integrity protection. Multiple algorithms can be entered.
+
+  :code:`set service ssh macs <macs>`
+
+  Supported MACs:
+
+ * `hmac-md5`
+ * `hmac-md5-96`
+ * `hmac-ripemd160`
+ * `hmac-sha1`
+ * `hmac-sha1-96`
+ * `hmac-sha2-256`
+ * `hmac-sha2-512`
+ * `umac-64@openssh.com`
+ * `umac-128@openssh.com`
+ * `hmac-md5-etm@openssh.com`
+ * `hmac-md5-96-etm@openssh.com`
+ * `hmac-ripemd160-etm@openssh.com`
+ * `hmac-sha1-etm@openssh.com`
+ * `hmac-sha1-96-etm@openssh.com`
+ * `hmac-sha2-256-etm@openssh.com`
+ * `hmac-sha2-512-etm@openssh.com`
+ * `umac-64-etm@openssh.com`
+ * `umac-128-etm@openssh.com`
+
+
+Key Authentication
+##################
+
+It is highly recommended to use SSH Key authentication. By default there is
+only one user (``vyos``), and you can assign any number of keys to that user.
+You can generate a ssh key with the ``ssh-keygen`` command on your local
+machine, which will (by default) save it as ``~/.ssh/id_rsa.pub`` which is in
+three parts:
+
+ ``ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAA...VByBD5lKwEWB username@host.example.com``
+
+Only the type (``ssh-rsa``) and the key (``AAAB3N...``) are used. Note that
+the key will usually be several hundred characters long, and you will need to
+copy and paste it. Some terminal emulators may accidentally split this over
+several lines. Be attentive when you paste it that it only pastes as a single
+line. The third part is simply an identifier, and is for your own reference.
+
+
+**Assign SSH Key to user**
+
+Under the user (in this example, ``vyos``), add the public key and the type.
+The `identifier` is simply a string that is relevant to you.
+
+.. code-block:: sh
+
+  set system login user vyos authentication public-keys 'identifier' key "AAAAB3Nz...."
+  set system login user vyos authentication public-keys 'identifier' type ssh-rsa"
+
+You can assign multiple keys to the same user by changing the identifier. In
+the following example, both Unicron and xrobau will be able to SSH into VyOS
+as the ``vyos`` user using their own keys.
+
+.. code-block:: sh
+
+  set system login user vyos authentication public-keys 'Unicron' key "AAAAB3Nz...."
+  set system login user vyos authentication public-keys 'Unicron' type ssh-rsa
+  set system login user vyos authentication public-keys 'xrobau' key "AAAAQ39x...."
+  set system login user vyos authentication public-keys 'xrobau' type ssh-rsa
+
+
+
 TFTP
 ----
 
@@ -1383,6 +1533,7 @@ The resulting configuration will look like:
 .. _`Cisco Discovery Protocol`: https://en.wikipedia.org/wiki/Cisco_Discovery_Protocol
 .. _`Foundry Discovery Protocol`: https://en.wikipedia.org/wiki/Foundry_Discovery_Protocol
 .. _`Multicast DNS`: https://en.wikipedia.org/wiki/Multicast_DNS
+.. _SSH: https://en.wikipedia.org/wiki/Secure_Shell
 .. _SNMP: https://en.wikipedia.org/wiki/Simple_Network_Management_Protocol
 .. _SNMPv2: https://en.wikipedia.org/wiki/Simple_Network_Management_Protocol#Version_2
 .. _SNMPv3: https://en.wikipedia.org/wiki/Simple_Network_Management_Protocol#Version_3