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Setting up FreeRADIUS

This section describes how to set up FreeRADIUS for an IdP. It assumes that you have already executed the configuration steps for the eduroam SP configuration of FreeRADIUS. We will expand that configuration to turn FreeRADIUS into a simple IdP. N.B.: even if you are going to have an IdP-only installation, the eduroam SP configuration for FreeRADIUS is still the exact same. You just don't define any own Access Point clients in clients.conf.

...

We suggest to create an own certificate. FreeRADIUS makes this very easy by providing an automatic script for that purpose. Execute the

Code Block

/etc/raddb/certs/bootstrap

...

The file /etc/raddb/eap.conf defines how EAP authentication is to be executed. The shipped configuration file is not adequate for eduroam use; it enabled EAP-MD5 and LEAP, for example; which are not suitable as eduroam EAP types. Use the following content for eap.conf instead. It enables PEAP and TTLS:

Code Block

eap {
                default_eap_type = peap
                timer_expire     = 60
                ignore_unknown_eap_types = no
                cisco_accounting_username_bug = no

                tls {
                        certdir = ${confdir}/certs
                        cadir = ${confdir}/certs
                        private_key_password = whatever
                        private_key_file = ${certdir}/server.key
                        certificate_file = ${certdir}/server.pem
                        CA_file = ${cadir}/ca.pem
                        dh_file = ${certdir}/dh
                        random_file = /dev/urandom
                        fragment_size = 1024
                        include_length = yes
                        check_crl = no
                        cipher_list = "DEFAULT"
                }

                ttls {
                        default_eap_type = mschapv2
                        copy_request_to_tunnel = yes
                        use_tunneled_reply = yes
                        virtual_server = "eduroam-inner-tunnel"
                }

                peap {
                        default_eap_type = mschapv2
                        copy_request_to_tunnel = yes
                        use_tunneled_reply = yes
                        virtual_server = "eduroam-inner-tunnel"
                }

                mschapv2 {
                }

        }

A common question regarding this definition is: "why is TLS also configured? I don't want it, can I disable it?" The answer is: the TTLS and PEAP sections depend on the tls stanza for the definition of which server certificates to use. You cannot delete the stanza, but that doesn't mean you can't effectively disable TLS: the tls stanza contains the ca_file parameter. Only clients with a TLS client certificate from this CA will be accepted. We have just created a brand-new CA with the "bootstrap" script. Simply don't issue nor distribute any client certificates from this CA, then nobody will be able to log in with EAP-TLS.

Another question is regarding the mschapv2 section. For all practical purposes, the easy answer is that it is a piece of magic and needs to be there for PEAP to work. If you are curious regarding the gory details, please let us know.

Note that one parameter for both the ttls and peap stanza is "virtual_server = eduroam-inner-tunnel". This means that the inner EAP authentication will be carried out in this other virtual server, which we will define later.

...

Virtual server eduroam: enable EAP

...

Compared to the eduroam SP config, you simply need to additionally mention the "eap" module in both the authorize and authenticate stanza. It will then look like the following: 

Code Block

authorize {
       auth_log
       suffix
       eap
}

authenticate {
       eap
}

...

Virtual server eduroam-inner-tunnel

...

When the eap module has started with an authentication, it will first establish a TLS tunnel; this is done by enabling the module in the previous "eduroam" virtual server. After the TLS tunnel is established, the content (i.e. the tunneled authentication) is processed separately in this new virtual server. Create the file in /etc/raddb/sites-enabled/eduroam-inner-tunnel and give it the following content:

Code Block

server eduroam-inner-tunnel {

authorize {
        auth_log
        eap
        files
        mschap
        pap
}

authenticate {
        Auth-Type PAP {
                pap
        }
        Auth-Type MS-CHAP {
                mschap
        }
        eap
}

post-auth {
        reply_log
        Post-Auth-Type REJECT {
                reply_log
        }

}
}

Let's revisit the modules which this virtual server executes one after another:

  • auth_log: logs the incoming packet to the file system. This is needed to fulfill the eduroam SP logging requirements. Note that this log *may* contain the user's cleartext password if TTLS-PAP is used. You can log the packet with omitted User-Password attribute if you prefer; see the "Goodies" section for more details).
  • eap: if the EAP authentication contains another EAP instance inside, the module will decode it. This is the case for PEAP.
  • files: this module tries to find out the authoritative password for the user by looking up the username in the file
  • mschap: this module is in effect only if PEAP-MSCHAPv2 or TTLS-MSCHAPv2 is used. It will mark the packet as to be authenticated with MS-CHAP algorithms later.
  • pap: this module is in effect only if TTLS-PAP is used. It will mark the packet as to be authenticated with PAP alogrithms later.
  • reply_log: logs the reply packet to the file system

...

User database: flat file

...

By default, the "files" module will use information in the file

Code Block

/etc/raddb/users

for authenticating users. This file has a straightforward format

Code Block

icecold@group1.aq       Cleartext-Password := "snowwhite"

otheruser@group1.aq     Cleartext-Password := "swordfish"

...

Local authentication for your realm

...

In the SP configuration, all requests were unconditionally forwarded to upstream. We will need to revisit the file "proxy.conf" and mark one realm to NOT proxy. In this example, we will use "@group1.aq" as the local authentication realm. Simply add the following stanza immediately preceeding the "DEFAULT" realm:

Code Block

realm group1.aq {
        nostrip
}

Since the stanza doesn't contain a server pool to proxy to, this realm won't be proxied and instead authenticated locally. This stanza works only for users who correctly use the full username format "user123@group1.aq" for their eduroam login.

If the IdP and SP are colocated, it is possible to *locally* also accept users who erronuously omitted their realm (just "user123"). This requires further configuration, but it is strongly discouraged, because it will give such users a "halfways-working" experience: they will be able to use eduroam when on their own IdP's campus, because no routing information needs to be evaluated, but their account will fail at all other locations. Therefore, this guide does not include instructions for that kind of setup.

...

Processing incoming requests

...

As an eduroam IdP, your users can go to other eduroam hotspots around the globe. They will still be authenticated at your server. In these roaming cases, your upstream FLR servers will send Access-Requests to your server. Surprisingly, it is very simple to configure that: these upstream servers are simply clients - just like an Access Point. So, simply add client stanzas for your FLR servers into clients.conf:

Code Block

 client antarctica-flr-1 {
        ipaddr                          = 172.20.1.2
        netmask                         = 32
        secret                          = secretstuff
        require_message_authenticator   = no
        shortname                       = antarctica-flr-1
        nastype                         = other
        virtual_server                  = eduroam
}

That's it! Now your server is prepared for eduroam IdP operation! You can add users to your "database" by amending the "users" file; if you do, you will unfortunately have to restart FreeRADIUS so that it picks up the change.

...

Goodies

...

Omitting User-Password in inner authentication logs

By default, the "detail" modules log every attribute as it was received. For inner authentications with TTLS-PAP, this means that the attribute "User-Password" with the user's perceived password will be logged. This is often considered harmful. You can deactivate it by blacklisting the attribute in the auth_log module in /etc/raddb/modules/auth_log:

Code Block

detail auth_detail {
  ...
  suppress {
    User-Password
  }}

adding VLAN assignment attributes

You can mark every user with a VLAN where he should be put into. This is done by assigning "reply items" to the user in the authentication database. In our flat file example, reply attributes are in a separate line, indented by a tab. To put our two example users into VLANs 17 and 42, respectively, the entries would look like the following:

Code Block

icecold@group1.aq       Cleartext-Password := "snowwhite"
			Tunnel-Type             := VLAN,
			Tunnel-Medium-Type      := IEEE-802,
			Tunnel-Private-Group-ID := 17

otheruser@group1.aq     Cleartext-Password := "swordfish"
			Tunnel-Type             := VLAN,
			Tunnel-Medium-Type      := IEEE-802,
			Tunnel-Private-Group-ID := 42

Using MySQL as user database backend

Mandating or forbidding use of anonymous outer identity. Note that in newer versions of FreeRADIUS (>3.0.14) there is a new tls-config section that allows you to configure the common TLS configuration without configuring the TLS EAP type. The config above is backwards compatable, but if you want to take advantage of the new section you can replace the name of the "tls" block above with "tls-config tls-common" and then reference it from each EAP type with "tls = tls-common" (the example eap config shows you how to do this).

Another question is regarding the mschapv2 section. For all practical purposes, the easy answer is that it is a piece of magic and needs to be there for PEAP to work. If you are curious regarding the gory details, please let us know.

Note that one parameter for both the ttls and peap stanza is "virtual_server = eduroam-inner-tunnel". This means that the inner EAP authentication will be carried out in this other virtual server, which we will define later.

Virtual server eduroam: enable EAP, make Operator-Name conditional

Compared to the eduroam SP config, you need to additionally mention the "eap" module in both the authorize and authenticate stanza of the file /etc/raddb/sites-enabled/eduroam so that your server can process EAP requests from your own userbase.

You should also make sure to only tag those incoming requests with the Operator-Name attribute which actually originate from your own WiFi gear - as an IdP, your own users roaming elsewhere will also be processed, but they should not carry your own Operator-Name. For the purposes of this wiki, let's assume that you are connected to one FLR server, and it is defined in your clients.conf with the shortname "antarctica-flr-1" (see below for the exact definition).

It will then look like the following: 

Code Block
authorize {
                if ("%{client:shortname}" != "antarctica-flr-1") {
                   update request {
                           Operator-Name := "1yourdomain.tld"
                            # the literal number "1" above is an important prefix! Do not change it!
                   }
                }
                auth_log
                suffix
                eap
        }

authenticate {
       eap
}
Virtual server eduroam-inner-tunnel

When the eap module has started with an authentication, it will first establish a TLS tunnel; this is done by enabling the module in the previous "eduroam" virtual server. After the TLS tunnel is established, the content (i.e. the tunneled authentication) is processed separately in this new virtual server. Create the file in /etc/raddb/sites-enabled/eduroam-inner-tunnel and give it the following content:

Code Block
server eduroam-inner-tunnel {

authorize {
        auth_log
        eap
        files
        mschap
        pap
}

authenticate {
        Auth-Type PAP {
                pap
        }
        Auth-Type MS-CHAP {
                mschap
        }
        eap
}

post-auth {
        reply_log
        Post-Auth-Type REJECT {
                reply_log
        }

}
}

Let's revisit the modules which this virtual server executes one after another:

  • auth_log: logs the incoming packet to the file system. This is needed to fulfill the eduroam SP logging requirements. Note that this log *may* contain the user's cleartext password if TTLS-PAP is used. You can log the packet with omitted User-Password attribute if you prefer; see the "Goodies" section for more details).
  • eap: if the EAP authentication contains another EAP instance inside, the module will decode it. This is the case for PEAP.
  • files: this module tries to find out the authoritative password for the user by looking up the username in the file
  • mschap: this module is in effect only if PEAP-MSCHAPv2 or TTLS-MSCHAPv2 is used. It will mark the packet as to be authenticated with MS-CHAP algorithms later.
  • pap: this module is in effect only if TTLS-PAP is used. It will mark the packet as to be authenticated with PAP alogrithms later.
  • reply_log: logs the reply packet to the file system
User database: flat file

By default, the "files" module will use information in the file

Code Block
/etc/raddb/users

for authenticating users. This file has a straightforward format

Code Block
icecold@group1.aq       Cleartext-Password := "snowwhite"

otheruser@group1.aq     Cleartext-Password := "swordfish"
Local authentication for your realm

In the SP configuration, all requests were unconditionally forwarded to upstream. We will need to revisit the file "proxy.conf" and mark one realm to NOT proxy. In this example, we will use "@group1.aq" as the local authentication realm. Simply add the following stanza immediately preceeding the "DEFAULT" realm:

Code Block
realm group1.aq {
        nostrip
}

Since the stanza doesn't contain a server pool to proxy to, this realm won't be proxied and instead authenticated locally. This stanza works only for users who correctly use the full username format "user123@group1.aq" for their eduroam login.

If the IdP and SP are colocated, it is possible to *locally* also accept users who erronuously omitted their realm (just "user123"). This is NOT permitted by the eduroam policy (read 6.3.2 bullet 6 under AAA Servers of the current service definition document: "The outer EAP identities (and with it, RADIUS User-Name attributes) for the IdP MUST be in the format of arbitrary@realm"). Allowing this also requires further configuration and it is strongly discouraged, because it will give such users a "halfways-working" experience: they will be able to use eduroam when on their own IdP's campus, because no routing information needs to be evaluated, but their account will fail at all other locations. Therefore, this guide does not include instructions for that kind of setup.

Processing incoming requests

As an eduroam IdP, your users can go to other eduroam hotspots around the globe. They will still be authenticated at your server. In these roaming cases, your upstream FLR servers will send Access-Requests to your server. Surprisingly, it is very simple to configure that: these upstream servers are simply clients - just like an Access Point. So, simply add client stanzas for your FLR servers into clients.conf:

Code Block
 client antarctica-flr-1 {
        ipaddr                          = 172.20.1.2
        netmask                         = 32
        secret                          = secretstuff
        require_message_authenticator   = yes
        shortname                       = antarctica-flr-1
        nastype                         = other
        virtual_server                  = eduroam
}
CUI for eduroam IdP

To use the Chargeable-User-Identity (CUI) you must already use the Operator-Name attribute. This documentation is only for FreeRADIUS 3.0.X release.

Modify the log module

Edit "eduroam_cui_log" file in the mods-available/ subdirectory and add the following lines to your virtual inner server :

Code Block
...
linelog cui_inner_log {
#    filename = syslog
    filename = ${logdir}/radius.log
    format = ""
    reference = "inner_auth_log.%{%{reply:Packet-Type}:-format}"
    inner_auth_log {
        Access-Accept = "%t : eduroam-inner-auth#VISINST=%{request:Operator-Name}#USER=%{User-Name}#CSI=%{%{Calling-Station-Id}:-Unknown Caller Id}#NAS=%{%{Called-Station-Id}:-Unknown Access Point}#CUI=%{%{%{reply:Chargeable-User-Identity}:-%{outer.reply:Chargeable-User-Identity}}:-Local User}#RESULT=OK#"
        Access-Reject = "%t : eduroam-inner-auth#VISINST=%{request:Operator-Name}#USER=%{User-Name}#CSI=%{%{Calling-Station-Id}:-Unknown Caller Id}#NAS=%{%{Called-Station-Id}:-Unknown Access Point}#CUI=%{%{%{reply:Chargeable-User-Identity}:-%{outer.reply:Chargeable-User-Identity}}:-Local User}#RESULT=FAIL#"
    }
}


Use policy and module in your eduroam-inner-tunnel virtual server

Add 'cui-inner' (policy already defined, you don't need to change it) and 'cui_inner_log' in post-auth section :

Code Block
server eduroam-inner-tunnel {
...
		post-auth {
				reply_log
				cui_inner_log
				cui-inner
				Post-Auth-Type REJECT {
					reply_log
					cui_inner_log
				}
		}
...
}


That's it! Now your server is prepared for eduroam IdP operation! You can add users to your "database" by amending the "users" file; if you do, you will unfortunately have to restart FreeRADIUS so that it picks up the change.

Goodies

Omitting User-Password in inner authentication logs

By default, the "detail" modules log every attribute as it was received. For inner authentications with TTLS-PAP, this means that the attribute "User-Password" with the user's perceived password will be logged. This is often considered harmful. You can deactivate it by blacklisting the attribute in the auth_log module in /etc/raddb/modules/auth_log:

Code Block
detail auth_detail {
  ...
  suppress {
    User-Password
  }}

adding VLAN assignment attributes

You can mark every user with a VLAN where he should be put into. This is done by assigning "reply items" to the user in the authentication database. In our flat file example, reply attributes are in a separate line, indented by a tab. To put our two example users into VLANs 17 and 42, respectively, the entries would look like the following:

Code Block
icecold@group1.aq       Cleartext-Password := "snowwhite"
			Tunnel-Type             := VLAN,
			Tunnel-Medium-Type      := IEEE-802,
			Tunnel-Private-Group-ID := 17

otheruser@group1.aq     Cleartext-Password := "swordfish"
			Tunnel-Type             := VLAN,
			Tunnel-Medium-Type      := IEEE-802,
			Tunnel-Private-Group-ID := 42

Using SQL as user database backend

Using a flat file as in our example scales very poorly. You can use arbitrary database backends instead; the FreeRADIUS documentation can give you an overview. If you wish to use SQL, changing our example configuration is very easy: simply replace the "files" line in eduroam-inner-tunnel:authorize with "sql". You'll need to specify the connection details for your SQL backend in the corresponding module ( /etc/raddb/modules/sql ).

The schema which FreeRADIUS uses to store user information is similarly structured to the "users" file: a table radcheck holds the check items (i.e. the username and password), and the radreply table contains the reply items (for example VLAN memberships, as explained above).

Mandating or forbidding use of anonymous outer identity

eduroam at large supports anonymous outer identities for user logins. It is at the discretion of eduroam IdPs whether they want to

  • mandate that their users use an anonymous outer identity
  • forbid their users to  use an anonymous outer identity
  • be agnostic in that respect

Configuring any one of the three choices is done with only a few lines of configuration. The easiest choice is being agnostic: no configuration is necessary, since there is no link between the inner and outer User-Name attribute in FreeRADIUS.

If you want to mandate the use of anonymous outer identities, the recommended way is using the identity "@realm" (i.e. the part left of the @ sign should be empty). You can enforce that only this outer User-Name is allowed to proceed to EAP authentication by adding the following to the authenticate section:

Code Block
if ( User-Name != "@realm" ) {
      fail
}

If you want to forbid usage of anonymous outer identities, you can do this by comparing the two presented User-Name attributes of the outer and inner authentication. You can only do this in the eduroam-inner-tunnel virtual server obviously, since only that server has access to the inner identity. Put the following into the "authenticate" section of eduroam-inner-tunnel:

Code Block
if ( User-Name != outer.User-Name ) {
     fail
}
More information

Eduroam-in-a-box web configuration tool:http://eduroam.sourceforge.net