Wednesday, February 7, 2018

New feature: OCSP and OCSP stapling support for TLS and EAP

New Radiator version 4.20 introduces support for OCSP and OCSP stapling for TLS based EAP methods (such as EAP-TLS, EAP-TTLS, and EAP-PEAP) and RadSec (TLS encryption for RADIUS over TCP).

OCSP (Online Certificate Status Protocol) is a method for checking certificates' revocation status online and is used as an alternative for CRL (Certificate Revocation List) files. Whereas CRL files needs to be updated every now and then, OCSP uses queries sent to CA (Certificate Authority) to obtain the latest revocation status.

Radiator uses OCSP to query and verify that EAP supplicant's or RadSec peer's certificate has not been revoked and can provide OCSP staple to EAP supplicants and RadSec peers to verify that Radiator's own certificate has not been revoked. More info about OCSP and OCSP staple can be found from the references at the end.

In order to use OCSP with Radiator, following conditions needs to be met:
  • Radiator version 4.20 or later
  • X.509 certificates and CA used support OCSP
  • OpenSSL library version 1.0.0 or later
  • Perl Net::SSLeay library version 1.83 or later
  • Perl LWP::UserAgent library
  • (Optional) Perl HTTP::Async library for asynchronous OCSP queries (supported only with EAP-TLS)

In this blog post, we show two configuration examples how to enable and test OCSP support.

We use demo certificates bundled with Radiator which do support OCSP.
You can check whether your X.509 certificate contains OCSP URL with the commands shown below.

Test client certificate:
% cd path/to/radiator-distribution
% openssl x509 -noout -issuer -subject -ocsp_uri -in certificates/cert-clt.pem
issuer= /C=AU/ST=Victoria/L=Melbourne/O=OSC Demo Certificates/OU=Test Certificate Section/CN=OSC Test CA (do not use in production)/emailAddress=mikem@open.com.au
subject= /C=AU/ST=Victoria/L=Melbourne/O=OSC Demo Certificates/OU=Test Certificate Section/CN=testUser
http://127.0.0.1:8008

Test server certificate:
% cd path/to/radiator-distribution
% openssl x509 -noout -issuer -subject -ocsp_uri -in certificates/cert-srv.pem
issuer= /C=AU/ST=Victoria/L=Melbourne/O=OSC Demo Certificates/OU=Test Certificate Section/CN=OSC Test CA (do not use in production)/emailAddress=mikem@open.com.au
subject= /C=AU/ST=Victoria/L=Melbourne/O=OSC Demo Certificates/OU=Test Certificate Section/CN=test.server.some.company.com
http://127.0.0.1:8008

For testing OCSP, we run OCSP responder provided by OpenSSL library.
Normally, CA who has signed the certificates runs OCSP responder on the Internet.

OCSP responder is run with a command shown below (pass phrase for all demo certificates is "whatever"):
% cd path/to/radiator-distribution/certificates
% openssl ocsp -rsigner root-CA-crt.pem -rkey root-CA-key.pem -index root-CA-idx.txt -port 8008 -CA root-CA-crt.pem -text
Enter pass phrase for root-CA-key.pem:
Waiting for OCSP client connections...

Leave OCSP responder running on http://127.0.0.1:8008/ and waiting for OCSP queries from Radiator.

EAP-TLS OCSP configuration example



Radiator configuration which enables OCSP queries and OCSP stapling for EAP-TLS (there is a similar example config in goodies/eap_tls.cfg):
Foreground
LogStdout
LogDir        .
DbDir         .
# User a lower trace level in production systems:
Trace         4
LogFile       %L/radiator.log

AuthPort 1812
AcctPort 1813

<Client DEFAULT>
      Secret radius
</Client>

<Handler>
      <AuthBy FILE>
            # Users must be in this file to get anywhere
            Filename %D/users
            
            EAPType                   TLS
            EAPTLS_CAFile             %D/certificates/demoCA/cacert.pem
            EAPTLS_CertificateFile    %D/certificates/cert-srv.pem
            EAPTLS_CertificateType    PEM
            EAPTLS_PrivateKeyFile     %D/certificates/cert-srv.pem
            EAPTLS_PrivateKeyPassword whatever
            EAPTLS_MaxFragmentSize    1200
            
            # Online Certificate Status Protocol (OCSP) related
            # configuration parameters

            # Provide OCSP staple for EAP-TLS clients asking for it.
            EAPTLS_OCSPStapling

            # Check OCSP status of EAP-TLS client certificates during TLS handshake
            EAPTLS_OCSPCheck

            # Check OCSP status of EAP-TLS client certificates asynchronous after TLS handshake
            # but before authenticating and authorizing the client.
            #EAPTLS_OCSPAsyncCheck

            # Reject EAP-TLS client certificate when OCSP responder is unavailable or OCSP status query fails.
            # By default, only a valid OCSP status response can reject EAP-TLS client certificate.
            EAPTLS_OCSPStrict

            # Use specified OCSP URI for OCSP queries instead of OCSP URI in EAP-TLS client certificate.
            #EAPTLS_OCSPURI

            # If OCSP query to OCSP URI fails, mark OCSP responder failed for 10 minutes.
            EAPTLS_OCSPFailureBackoffTime 600

            # Cache OCSP statuses for 1 hour (defaults to 20 minutes)
            EAPTLS_OCSPCacheTime 3600

            # Cache OCSP status for max 2000 different certificates (defaults to 1000 entries)
            EAPTLS_OCSPCacheSize 2000

            AutoMPPEKeys
      </AuthBy>
</Handler>

wpa_supplicant / eapol_test configuration for EAP-TLS which requires OCSP staple:
network={
      ssid="my8021xwpa"
      key_mgmt=WPA-EAP
      eap=TLS
      identity="testUser"
      ca_cert="./certificates/demoCA/cacert.pem"
      client_cert="./certificates/client-crt.pem"
      private_key="./certificates/client-key.pem"
      private_key_passwd="whatever"
      ocsp=2
}

RadSec OCSP configuration example


Besides TLS based EAP methods, OCSP can also be used with RadSec peerings, either with or without OCSP stapling.



Radiator configuration for RadSec client enables OCSP stapling (there is a similar example config in goodies/radsec-client.cfg):
Foreground
LogStdout
LogDir        .
DbDir         .
# User a lower trace level in production systems:
Trace         4

<Client DEFAULT>
      Secret mysecret
</Client>

<Handler>
      <AuthBy RADSEC>
            ReconnectTimeout        10
            NoreplyTimeout          5
            KeepaliveTimeout        30
            KeepaliveNoreplyTimeout 2
            UseStatusServerForFailureDetect

            UseTLS
            TLS_CAFile             %D/certificates/demoCA/cacert.pem
            TLS_CertificateFile    %D/certificates/cert-clt.pem
            TLS_CertificateType    PEM
            TLS_PrivateKeyFile     %D/certificates/cert-clt.pem
            TLS_PrivateKeyPassword whatever

            # Online Certificate Status Protocol (OCSP) related
            # configuration parameters

            # Request OCSP staple from RadSec server.
            TLS_OCSPStapling

            # Alternatively, check OCSP status of RadSec server certificates during TLS handshake.
            #TLS_OCSPCheck

            # Reject RadSec server certificate when OCSP staple or
            # OCSP responder is unavailable or OCSP status query
            # fails. By default, only a valid OCSP status
            # response can reject RadSec server certificate.
            TLS_OCSPStrict

            <Host localhost>
            </Host>
      </AuthBy>
</Handler>

Radiator configuration for RadSec server which enables OCSP queries and OCSP stapling (there is a similar example config in goodies/radsec-server.cfg):
Foreground
LogStdout
LogDir        .
DbDir         .
# User a lower trace level in production systems:
Trace         4

# Don't listen on any UDP ports
AuthPort
AcctPort

# Listen for AuthBy RADSEC connections from RadSec clients
<ServerRADSEC>
      UseTLS
      TLS_CAFile ./certificates/demoCA/cacert.pem
      TLS_CertificateFile ./certificates/cert-srv.pem
      TLS_CertificateType PEM
      TLS_PrivateKeyFile ./certificates/cert-srv.pem
      TLS_PrivateKeyPassword whatever

      TLS_RequireClientCert
      # Accept any peer with valid cert signed by demoCA for demo
      TLS_ExpectedPeerName .+

      # Online Certificate Status Protocol (OCSP) related
      # configuration parameters

      # Provide OCSP staple for RadSec client requesting it.
      TLS_OCSPStapling

      # Check OCSP status of RadSec client certificates during TLS handshake.
      TLS_OCSPCheck

      # Reject RadSec client certificate when OCSP staple or OCSP
      # responder is unavailable or OCSP status query fails. By
      # default, only a valid OCSP status response can reject RadSec
      # client certificate.
      TLS_OCSPStrict

      # Use specified OCSP URI for OCSP queries instead of OCSP URI in RadSec client certificate.
      #TLS_OCSPURI

      # If OCSP query to OCSP URI fails, mark OCSP responder failed for 10 minutes.
      TLS_OCSPFailureBackoffTime 600

      # Cache OCSP statuses for 1 hour (defaults to 20 minutes)
      TLS_OCSPCacheTime 3600

      # Cache OCSP status for max 2000 different certificates (defaults to 1000 entries)
      TLS_OCSPCacheSize 2000
</ServerRADSEC>

<Handler>
      <AuthBy FILE>
            Filename ./users
      </AuthBy>
</Handler>

Radiator acting as RadSec client (AuthBy RADSEC) will connect to Radiator acting as RadSec server (ServerRADSEC) and will request OCSP staple to be returned during TLS handshake. Server will get OCSP response for its own certificate and return it as OCSP staple to the client and when the client has sent its certificate, the server will query its revocation status with OCSP before accepting it.

References