How to Handle a Certificate Revocation List

A certificate revocation list (CRL) contains outdated or compromised certificates from a Certificate Authority. You have four ways to handle CRLs.

• If your CA organization does not issue CRLs, you can instruct IKE to ignore CRLs in your /etc/inet/ike/config file. This option is shown in Step 6 in How to Configure IKE With Certificates Signed by a CA.

• IKE can access the CRLs from a URI (uniform resource indicator) whose address is embedded in the public key certificate from the CA.

• IKE can access the CRLs from an LDAP server whose DN (directory name) entry is embedded in the public key certificate from the CA.

• You can provide the CRL as an argument to the ikecert certrldb command.

The following procedure describes how to instruct IKE to use CRLs from a central distribution point.

1. Display the certificate that you received from the CA.

   # ikecert certdb -lv certspec

   -l

   Lists certificates in the IKE certificate database.

   -v

   Lists the certificates in verbose mode. Use this option with care.

   certspec

   Is a pattern that matches a certificate in the IKE certificate database.

   For example, the following certificate was issued by Sun Microsystems. Details have been altered.

   # ikecert certdb -lv example-protect.sun.com Certificate Slot Name: 0 Type: dsa-sha1 (Private key in certlocal slot 0) Subject Name: <O=Sun Microsystems Inc, CN=example-protect.sun.com> Issuer Name: <CN=Sun Microsystems Inc CA (Cl B), O=Sun Microsystems Inc> SerialNumber: 14000D93 Validity: Not Valid Before: 2002 Jul 19th, 21:11:11 GMT Not Valid After: 2005 Jul 18th, 21:11:11 GMT Public Key Info: Public Modulus (n) (2048 bits): C575A…A5 Public Exponent (e) ( 24 bits): 010001 Extensions: Subject Alternative Names: DNS = example-protect.sun.com Key Usage: DigitalSignature KeyEncipherment [CRITICAL] CRL Distribution Points: Full Name: URI = #Ihttp://www.sun.com/pki/pkismica.crl#i DN = <CN=Sun Microsystems Inc CA (Cl B), O=Sun Microsystems Inc> CRL Issuer: Authority Key ID: Key ID: 4F … 6B SubjectKeyID: A5 … FD Certificate Policies Authority Information Access

   Notice the CRL Distribution Points data. The URI entry indicates that this organization's CRL is available on the web. The DN entry indicates that the CRL is also available on an LDAP server. You can use one of these two options.

2. To use the URI, add the keyword use_http to the host's /etc/inet/ike/config file.

   For example, the ike/config file would appear similar to the following:

   # Use CRL from organization's URI use_http …

   You can also use a web proxy by adding the keyword proxy in the ike/config file. The proxy keyword takes a URL as an argument, as in the following:

   proxy "http://proxy1:8080"

   IKE retrieves the CRL and caches the CRL until the certificate expires.

3. To use LDAP, use the LDAP server as an argument to the ldap-list keyword in the host's /etc/inet/ike/config file.

   Your organization provides the name of the LDAP server. The entry in the ike/config file would appear similar to the following:

   # Use CRL from organization's LDAP ldap-list "ldap1.sun.com:389,ldap2.sun.com" …

   IKE retrieves the CRL and caches the CRL until the certificate expires.

Example—Pasting a CRL Into the Local certrldb Database

If the PKI organization's CRL is not available from a central distribution point, you can add the PKI organization's CRL manually to the local certrldb database. Follow the PKI organization's instructions for extracting the CRL, then add the CRL to the database with the ikecert certrldb –a command.

# ikecert certrldb -a
Press the Return key
Paste the CRL from the PKI organization
Press the Return key
Press <Control>-D to enter the CRL into the database