1. Overview

No current version of OpenSSH currently natively supports moonshot, but patches are available for v5.3 and v5.9 of OpenSSH to fix the issues that stop it from working. Ultimately we hope that these patches will become a standard part of OpenSSH, so that OpenSSH will work without any extra work being necessary.

2. Compatibility

2.1. Key

In the tables below, the following icons have the following meanings:

•  - This version of the software has been tested and verified as supporting Moonshot.
•  - This version of the software has been tested and verified as not supporting Moonshot.
•  - This version of the software has not yet been tested thoroughly and its status is not known. Let us know if you have tried it and whether it worked or not!

2.2. Compatibility List

Note that accessing supported versions of this software requires a Moonshot compatible client - see the next section for details on which clients are supported.

OS version	Compatible?	Packages Available?	Notes
CentOS 6			Using our pre-compiled package. Re-compiling instructions available.
CentOS 7			Using our pre-compiled package.
Debian 7			Using our pre-compiled package.
Debian 8			Building instructions available.
RHEL 6			Using our pre-compiled package. Re-compiling instructions available.
RHEL 7			Using our pre-compiled package.
Scientific Linux 6			Using our pre-compiled package. Re-compiling instructions available.
Scientific Linux 7			Using our pre-compiled package.
Ubuntu 12.04 LTS			Using our pre-compiled package for Debian 7
Ubuntu 14.04 LTS			Building instructions available.

3. Installation & Configuration Instructions

How you set up a Moonshot-enabled version of the OpenSSH server will differ depending on your OS. See the relevant pages for your particular distribution:

• CentOS 6
• CentOS 7
• Debian 7
• Debian 8
• RHEL 6
• RHEL 7
• Scientific Linux 6
• Scientific Linux 7

4. Client Compatibility

The following clients are known to work with this server software using Moonshot authentication (click on the link to see further information about enabling Moonshot in that client):

• OpenSSH Client

5. Next Steps

Once you have installed the software, what happens next?

5.1. Configuration Instructions

Once installed, the Moonshot-enabled OpenSSH server will still need a few quick tweaks in order to turn on the Moonshot support.

1. Ensure that the certificates referenced in /etc/radsec.conf can be read by the SSH user:

   $ su - --shell=/bin/bash sshd
   $ cat path_to_ca.pem
   $ cat path_to_client.pem
   $ cat path_to_client.key

   If they cannot be read by the SSH user, add the SSH user to the group that can read the certificates.

2. Configure the OpenSSH server to use Moonshot by editing /etc/ssh/sshd_config. Check the following lines are present and uncommented:

   GSSAPIAuthentication yes
   GSSAPIKeyExchange yes
   GSSAPIStrictAcceptorCheck yes
   

   GSSAPIStrictAcceptorCheck

   If your SSH server has a different hostname to the one given publicly (for example. you have CNAME entries you give to your users instead of the internal name), you should turn GSSAPIStrictAcceptorCheck off. Disabling the check defaults it to yes.

3. Restart the OpenSSH server

4. Configure the OpenSSH Client.

5.2. Account Mapping

5.2.1. Mapping to an account specified in a SAML attribute

Moonshot uses Shibboleth libraries to parse RADIUS and SAML attributes - SAML assertions can be embedded inside RADIUS responses by the IdP, allowing an IdP to exercise a very fine-grained authorisation policy. One potential use of this is to allow the Moonshot IdP to specify which account the user should log in to your SSH server as. To do this, it passes across a username in a SAML attribute and your server maps that to a local user account (via local-login-user).

1. Edit /etc/shibboleth/shibboleth2.xml and insert the following lines if they don't exist (note that this should go directly after the opening <SPConfig ... clockSkew="180"> stanza:

   <Extensions>
   	<Library path="plugins.so" fatal="true" />
   </Extensions>

2. Edit /etc/shibboleth/attribute-map.xml and find the SAML attribute that the Moonshot IdP will be sending you that contains the username.

   Example

   We want to map from the incoming SAML2 representation of "eduPersonEntitlement"

   <Attribute name="urn:oid:1.3.6.1.4.1.5923.1.1.1.7" id="entitlement"/>

3. Change the id of the attribute to "local-login-user".

   Example

   We change the attribute defining the SAML2 representation of "eduPersonEntitlement" such that its id becomes "local-login-user"

   <Attribute name="urn:oid:1.3.6.1.4.1.5923.1.1.1.7" id="local-login-user"/>

   In the standard Moonshot distribution, SSH will look for local-login-user to determine who to authenticate the user as. This attribute mapping will be managed by the XML assertion in the FreeRADIUS reply for a successful authentication.

5.2.2. Mapping to an account specified in a RADIUS attribute

Moonshot uses Shibboleth libraries to parse RADIUS and SAML attributes. Like the above SAML option, Moonshot can parse a RADIUS attribute (such as the User-Name attribute) and your server maps that to a local user account (via local-login-user).

1. Edit /etc/shibboleth/shibboleth2.xml and insert the following lines if they don't exist (note that this should go directly after the opening <SPConfig ... clockSkew="180"> stanza:

   <Extensions>
   	<Library path="plugins.so" fatal="true" />
   </Extensions>

2. Then find the line <AttributeExtractor type="XML" ...> further down in the file, duplicate it and modify the duplicate as follows:

   <AttributeExtractor type="GSSAPI" validate="true" reloadChanges="false" path="attribute-map.xml">

   You may want to store your GSSAPI attributes in a separate file. In this case, amend the path above to the new file.

3. Edit /etc/shibboleth/attribute-map.xml and find the first attribute line that does not use an AttributeDecoder.

   Example

   We will duplicate the incoming SAML2 representation of "eduPersonEntitlement"

   <Attribute name="urn:oid:1.3.6.1.4.1.5923.1.1.1.7" id="entitlement"/>

4. Duplicate the line. The name format for GSSAPI attributes is somewhat different. It does not use the OID namespace; instead it uses the IETF namespace. The attribute name is also different.

   Example

   We change the attribute defining the SAML2 representation of "eduPersonEntitlement" such that its id becomes "local-login-user" and it uses a different namespace

   <GSSAPIAttribute name="urn:ietf:params:gss:radius-attribute 1" id="local-login-user"/>

   The numeral 1 in the name of the attribute refers to RADIUS attribute 1, which is the User-Name. A more extensive compendium of attribute numbers is available at IANA's number registry.

   In the standard Moonshot distribution, SSH will look for local-login-user to determine who to authenticate the user as. This attribute mapping will be managed by the XML assertion in the FreeRADIUS reply for a successful authentication.

5.2.3. Further mapping options

To Come!