# Certificate Documentation

This directory contains scripts to create the server certificates.  To
make a set of default (i.e. test) certificates, simply type:

```
$ ./bootstrap
```

The `openssl` command will be run against the sample configuration
files included here, and will make a self-signed certificate authority
(i.e. root CA), and a server certificate.  This "root CA" should be
installed on any client machine needing to do EAP-TLS, PEAP, or
EAP-TTLS.

The Extended Key Usage (EKU) fields for "TLS web server" will be
automatically included in the server certificate.  Without those
extensions many clients will refuse to authenticate to FreeRADIUS.

The root CA and the "XP Extensions" file also contain a
crlDistributionPoints attribute. Many systems need this to be present
in order to validate the RADIUS server certificate. The RADIUS server
must have the URI defined but the CA need not have...however it is
best practice for a CA to have a revocation URI. Note that whilst the
Windows Mobile client cannot actually use the CRL when doing 802.1X it
is recommended that the URI be an actual working URL and contain a
revocation format file as there may be other OS behaviour at play and
future OSes that may do something with that URI.

For Windows, you will need to import the `p12` and/or the `der` format
of the certificates.  Linux systems need the `pem` format.

In general, you should use self-signed certificates for 802.1X (EAP)
authentication.  When you list root CAs from other organisations in
the `ca_file`, you permit them to masquerade as you, to authenticate
your users, and to issue client certificates for EAP-TLS.

If you already have CA and server certificates, rename (or delete)
this directory, and create a new `certs` directory containing your
certificates.  Note that the `make install` command will **not**
over-write your existing `raddb/certs` directory.


## New Installations of FreeRADIUS

We suggest that new installations use the test certificates for
initial tests, and then create real certificates to use for normal
user authentication.  See the instructions below for how to create the
various certificates.  The old test certificates can be deleted by
running the following command:

```
$ make destroycerts
```

Then, follow the instructions below for creating real certificates.

If you do not want to enable EAP-TLS, PEAP, or EAP-TTLS, then delete
the relevant sub-sections from the `raddb/mods-available/eap` file.
See the comments in that file for more information.


## Making a root Certificate

We recommend using a private certificate authority (CA).  While it can
be difficult to install this CA on multiple client machines, it is (in
general) more secure.

```
$ vi ca.cnf
```

Edit `default_days` to set the desired lifetime of the CA certificate.

Edit the `input_password` and `output_password` fields to be the
password for the CA certificate.

Edit the `[certificate_authority]` section to have the correct values
for your country, state, etc.

Create the CA certificate:

```
$ make ca.pem
```

Then the `DER` format needed by Windows:

```
$ make ca.der
```


## Making a Server Certificate

The following steps will let you create a server certificate for use
with TLS-based EAP methods, such as EAP-TLS, PEAP, and TTLS.  Follow
similar steps to create an `inner-server.pem` file, for use with
EAP-TLS that is tunneled inside of another TLS-based EAP method.

```
$ vi server.cnf
```

Edit `default_days` to set the lifetime of the server certificate.
The maximum for this is 825 for compatibility with all client devices.

Edit the `input_password` and `output_password` fields to be the
password for the server certificate.

Edit the `[server]` section to have the correct values for your
country, state, etc.  Be sure that the `commonName` field here is
different from the `commonName` for the CA certificate.

Create the server certificate:

```
$ make server
```


### Making a certificate for a public CA

If you wish to use an existing certificate authority, you can
create a certificate signing request for the server certificate, edit
`server.cnf` as above, and run the following command.

```
$ make server.csr
```

This step creates a "Certificate Signing Request" suitable for
submission to a public CA.


## Making a Client certificate

Client certificates are used by EAP-TLS, and optionally by EAP-TTLS
and PEAP.  The following steps outline how to create a client
certificate that is signed by the CA certificate created above.  You
will have to have the password for the CA certificate in the
`input_password` and `output_password` fields of the `ca.cnf` file.

```
$ vi client.cnf
```

Edit `default_days` to set the lifetime of the client certificate.

Edit the `input_password` and `output_password` fields to be the
password for the client certificate.  You will have to give these
passwords to the end user who will be using the certificates.

Edit the `[client]` section to have the correct values for your
country, state, etc.  Be sure that the `commonName` field here is
the `User-Name` which will be used for logins!

```
$ make client
```

The users certificate will be in `emailAddress.pem`,
e.g. `user@example.com.pem`.

To create another client certificate, just repeat the steps for
making a client certificate, being sure to enter a different login
name for `commonName`, and a different password.


## Performance

EAP performance for EAP-TLS, TTLS, and PEAP is dominated by SSL
calculations.  That is, a normal system can handle PAP
authentication at a rate of 10k packets/s.  However, SSL involves
RSA calculations, which are very expensive.  To benchmark your system,
do:

```
$ openssl speed rsa
```

or

```
$ openssl speed rsa2048
```

to test 2048 bit keys.

The number that is printed is the **maximum** number of
authentications per second which can be done for EAP-TLS (or TTLS,
or PEAP).  In practice, you will see results much lower than this
number, i.e. the actual EAP-TLS performance may be half of the
number printed here.

The reason is that EAP requires many round-trip packets, whereas
`openssl speed rsa2048` only does RSA calculations, and nothing else.


## Compatibility

The certificates created using this method are known to be compatible
with ALL operating systems.  Some common issues are:

* iOS and macOS have requirements on certificates.  See:
  https://support.apple.com/en-us/HT210176

* Many systems require certain OIDs in the certificates
  (`id-kp-serverAuth` for `TLS Web server authentication`).
  If the certificate does not contain these fields, the system
  will stop doing EAP.  The most visible effect is that the client
  starts EAP, gets a few Access-Challenge packets, and then a little
  while later re-starts EAP.  If this happens, see the FAQ, and the
  comments in `raddb/mods-available/eap` for how to fix it.

* All systems requires the root certificates to be on the client PC.
  If it doesn't have them, you will see the same issue as above.

* Windows XP post SP2 has a bug where it has problems with
  certificate chains.  i.e. if the server certificate is an
  intermediate one, and not a root one, then authentication
  will silently fail, as above.

* Some versions of Windows CE cannot handle 4K RSA certificates.
  They will (again) silently fail, as above.

* In none of these cases will Windows give the end user any
  reasonable error message describing what went wrong.  This leads
  people to blame the RADIUS server.  That blame is misplaced.

* Certificate chains of more than 64K bytes are known to not work.
  This is partly a problem in FreeRADIUS.  However, most clients cannot
  handle 64K certificate chains.  Most Access Points will shut down the
  EAP session after about 50 round trips, while 64K certificate chains
  will take about 60 round trips.  So don't use large certificate
  chains.  They will only work after everyone upgrades everything in the
  network.

* All other operating systems are known to work with EAP and
  FreeRADIUS.  This includes Linux, the BSDs, macOS, iOS, Android,
  Solaris, Symbian, along with all known embedded systems, phones,
  WiFi devices, etc.


## Security Considerations

The default certificate configuration files uses SHA256 for message
digests for security.
