EAP-TLS authentication support for PPP
======================================

1. Intro

    The Extensible Authentication Protocol (EAP; RFC 3748) is a
    security protocol that can be used with PPP.  It provides a means
    to plug in multiple optional authentication methods.

    Transport Level Security (TLS; RFC 2246) provides for mutual 
    authentication, integrity-protected ciphersuite negotiation and 
    key exchange between two endpoints.  It also provides for optional
    MPPE encryption.

    EAP-TLS (RFC 2716) incapsulates the TLS messages in EAP packets,
    allowing TLS mutual authentication to be used as a generic EAP
    mechanism. It also provides optional encryption using the MPPE
    protocol.

    This patch provide EAP-TLS support to pppd.
    This authentication method can be used in both client or server
    mode.

2. Building

    To build pppd with EAP-TLS support, OpenSSL (http://www.openssl.org)
    is required. Any version from 0.9.7 should work.
    
    Configure, compile, and install as usual. 

3. Configuration

    On the client side there are two ways to configure EAP-TLS:

	1. supply the appropriate 'ca', 'cert' and 'key' command-line parameters

	2. edit the /etc/ppp/eaptls-client file.
    Insert a line for each system with which you use EAP-TLS.
    The line is composed of this fields separated by tab:

      - Client name 
		The name used by the client for authentication, can be *
      - Server name
		The name of the server, can be *
      - Client certificate file 
		The file containing the certificate chain for the 
		client in PEM format
      - Server certificate file
		If you want to specify the certificate that the 
		server is allowed to use, put the certificate file name.
		Else put a dash '-'.
      - CA certificate file
		The file containing the trusted CA certificates in PEM
		format.
      - Client private key file
		The file containing the client private key in PEM format.


    On the server side edit the /etc/ppp/eaptls-server file.
    Insert a line for each system with which you use EAP-TLS.
    The line is composed of this fields separated by tab:

      - Client name
                The name used by the client for authentication, can be *
      - Server name
                The name of the server, can be *
      - Client certificate file
                If you want to specify the certificate that the
                client is allowed to use, put the certificate file name.
                Else put a dash '-'.
      - Server certificate file
		The file containing the certificate chain for the
                server in PEM format
      - CA certificate file
                The file containing the trusted CA certificates in PEM
                format.
      - Client private key file
                The file containing the server private key in PEM format.
      - addresses
		A list of IP addresses the client is allowed to use.


    OpenSSL engine support is included starting with v0.95 of this patch. 
    Currently the only engine tested is the 'pkcs11' engine (hardware token
    support). To use the 'pksc11' engine:
      - Use a special private key fileiname in the /etc/ppp/eaptls-client file:
          <engine>:<identifier>
        e.g.
          pkcs11:123456

      - The certificate can also be loaded from the 'pkcs11' engine using
        a special client certificate filename in the /etc/ppp/eaptls-client file:
          <engine>:<identifier>
        e.g.
          pkcs11:123456

      - Create an /etc/ppp/openssl.cnf file to load the right OpenSSL engine prior
        to starting 'pppd'. A sample openssl.cnf file is

        openssl_conf = openssl_def

        [ openssl_def ]
        engines = engine_section

        [ engine_section ]
        pkcs11 = pkcs11_section

        [ pkcs11_section ]
        engine_id = pkcs11
        dynamic_path = /usr/lib64/openssl/engines/engine_pkcs11.so
        MODULE_PATH = /usr/lib64/libeTPkcs11.so
        init = 0

      - There are two ways to specify a password/PIN for the PKCS11 engine:
          - inside the openssl.cnf file using
              PIN = your-secret-pin
            Note The keyword 'PIN' is case sensitive!
          - Using the 'password' in the ppp options file.
        From v0.97 of the eap-tls patch the password can also be supplied
        using the appropriate 'eaptls_passwd_hook' (see plugins/passprompt.c
        for an example).


4. Options

      These pppd options are available:

	  ca <ca-file>
			Use the CA public certificate found in <ca-file> in PEM format
	  cert <cert-file>
			Use the client public certificate found in <cert-file> in PEM format
			or in engine:engine_id format
	  key <key-file>
			Use the client private key found in <key-file> in PEM format
			or in engine:engine_id format
      crl-dir <dir>
        	Use CRL files from dir. It contains CRL files in PEM
		format and each file contains a CRL. The files are looked up 
		by the issuer name hash value. Use the c_rehash utility 
		to create necessary links.
      need-peer-eap
		If the peer doesn't ask us to authenticate or doesn't use eap
		to authenticate us, disconnect.

      Note: 
        password-encrypted certificates can be used as of v0.94 of this 
        patch. The password for the eap-tls.key file is specified using 
        the regular
          password ....
        statement in the ppp options file, or by using the appropriate
        plugin which supplies a 'eaptls_passwd_hook' routine.

5. Connecting

    If you're setting up a pppd server, edit the EAP-TLS configuration file 
    as written above and then run pppd with the 'auth' option to authenticate
    the client. The EAP-TLS method will be used if the other eap methods can't
    be used (no secrets).

    If you're setting up a client, edit the configuration file and then run
    pppd with 'remotename' option to specify the server name. Add the 
    'need-peer-eap' option if you want to be sure the peer ask you to
    authenticate (and to use eap) and to disconnect if it doesn't.

6. Notes

   This is experimental code.
   Send suggestions and comments to Jan Just Keijser <janjust@nikhef.nl>