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.
Adding IdP support in FreeRADIUS needs several steps to be executed:
- a TLS server certificate needs to be created for EAP methods to work
- the desired EAP types need to be configured.
- the virtual server eduroam needs to be instructed to do tunneled EAP authentication
- a user database needs to be linked to the FreeRADIUS instance to authenticate the users
- a realm needs to be marked as to-be-authenticated-locally in the configuration
- the server needs to be prepared to process incoming requests *from* the upstream FLR server
These steps are explained in detail below. For the user database, this example will use a "flat file" with usernames and passwords. The Goodies section contains examples for MySQL and other types of backend databases.
TLS server certificate
While it is possible to buy and install a commercial TLS certificate, this is neither necessary (the trust settings of web-browser stores don't apply for EAP, so there are no "recognised" CAs) nor prudent (a commercial CA issues many certificates, and uncautious users might be tempted to accept other certificates from that same CA).
We suggest to create an own certificate. FreeRADIUS makes this very easy by providing an automatic script for that purpose. Execute the
/etc/raddb/certs/bootstrap
script. It will generate certificates which are suited for EAP authentication, and name them so that the server can find them immediately without further configuration. Later, for the supplicant configuration, you will need to include the generated CA certificate into your supplicant configurations.
EAP type configuration
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:
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:
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:
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
/etc/raddb/users
for authenticating users. This file has a straightforward format
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:
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:
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:
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:
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
More information
Eduroam-in-a-box web configuration tool:http://eduroam.sourceforge.net