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Configuring CA

Configuring CA

This chapter describes how to configure certification authority (CA) interoperability, which is provided in support of the IPSec. CA interoperability allows the PIX Firewall and CAs to communicate so that your PIX Firewall can obtain and use digital certificates from the CA.

For CA background information, see "About CA." For the CA interoperability examples, see "CA Configuration Examples."

For a complete description of the IPSec-related commands used in this chapter, see "Command Reference." For a complete description of the non-IPSec commands used in this chapter, refer to the "Command Reference" chapter within the Configuration Guide for the Cisco Secure PIX Firewall Version 6.0.

This chapter includes the following sections:

Configuring CA


Note   Be sure that the PIX Firewall clock is set to GMT, month, day, and year before configuring CA. Otherwise, the CA may reject or allow certificates based on an incorrect timestamp. Cisco's PKI protocol uses the clock to make sure that a CRL is not expired.


Note   The lifetime of a certificate and the Certificate Revocation List (CRL) is checked in GMT time. If you are using IPSec with certificates, set the PIX Firewall clock to GMT to ensure that CRL checking works correctly.


Note   You need to have a CA available to your network before you configure CA. The CA must support Cisco's PKI protocol, the certificate enrollment protocol.

Follow these steps to enable your PIX Firewall to interoperate with a CA and obtain your PIX Firewall certificate(s):


Step 1   Configure the PIX Firewall host name:

hostname newname

 

For example:

hostname mypixfirewall

 

In this example, "mypixfirewall" is the name of a unique host in the domain.

Step 2   Configure the PIX Firewall domain name:

domain-name name

 

For example:

domain-name example.com

 

Step 3   Generate the PIX Firewall RSA key pair(s):

ca generate rsa key key_modulus_size

 

For example:

ca generate rsa key 512

 

In this example, one general purpose RSA key pair is to be generated. The other option is to generate two special-purpose keys. The selected size of the key modulus is 512.

Step 4   (Optional) View your RSA key pair(s):

show ca mypubkey rsa

 

The following is sample output from the show ca mypubkey rsa command:

show ca mypubkey rsa

 
% Key pair was generated at: 15:34:55 Aug 05 1999
 
Key name: mypixfirewall.example.com
 Usage: General Purpose Key
 Key Data:
  305c300d 06092a86 4886f70d 01010105 00034b00 30480241 00c31f4a ad32f60d
  6e7ed9a2 32883ca9 319a4b30 e7470888 87732e83 c909fb17 fb5cae70 3de738cf
  6e2fd12c 5b3ffa98 8c5adc59 1ec84d78 90bdb53f 2218cfe7 3f020301 0001
 

Step 5   Declare a CA:

ca identity ca_nickname ca_ipaddress [:ca_script_location] [ldap_ip address]

 

For example:

ca identity myca.example.com 209.165.202.130

 

In this example, 209.165.202.130 is the IP address of the CA. The CA name is myca.example.com.

Step 6   Configure the parameters of communication between the PIX Firewall and the CA:

ca configure ca_nickname ca | ra retry_period retry_count [crloptional]

 

For example:

ca configure myca.example.com ca 1 20 crloptional

 

If the PIX Firewall does not receive a certificate from the CA within 1 minute (default) of sending a certificate request, it will resend the certificate request. The PIX Firewall will continue sending a certificate request every 1 minute until a certificate is received or until 20 requests have been sent. With the keyword crloptional included within the command statement, other peer's certificates can still be accepted by your PIX Firewall even if the CRL is not accessible to your PIX Firewall.

Step 7   Authenticate the CA by obtaining its public key and its certificate:

ca authenticate ca_nickname [fingerprint]

 

For example:

ca authenticate myca.example.com 0123 4567 89AB CDEF 0123

 

The fingerprint (0123 4567 89AB CDEF 0123 in the example) is optional and is used to authenticate the CA's public key within its certificate. The PIX Firewall will discard the CA certificate if the fingerprint that you included in the command statement is not equal to the fingerprint within the CA's certificate.

You also have the option to manually authenticate the public key by simply comparing the two fingerprints after you receive the CA's certificate rather than entering it within the command statement.

Step 8   Request signed certificates from your CA for all of your PIX Firewall's RSA key pairs. Before entering this command, contact your CA administrator because they will have to authenticate your PIX Firewall manually before granting its certificate(s).

ca enroll ca_nickname challenge_password [serial] [ipaddress]

 

For example:

ca enroll myca.example.com mypassword1234567 serial ipaddress

 

The keyword mypassword1234567 in the example is a password, which is not saved with the configuration. The options "serial" and "ipaddress" are included, which indicates the PIX Firewall unit's serial number and IP address will be included in the signed certificate.

The ca enroll command requests as many certificates as there are RSA key pairs. You will only need to perform this command once, even if you have special usage RSA key pairs.

Step 9   Verify that the enrollment process was successful using the show ca certificate command:

show ca certificate

 

The following is sample output from the show ca certificate command including a PIX Firewall general purpose certificate and the RA and CA public-key certificates:

Subject Name
    Name: mypixfirewall.example.com
IP Address: 192.150.50.110
  Status: Available
  Certificate Serial Number: 36f97573
  Key Usage: General Purpose
 
RA Signature Certificate
  Status: Available
  Certificate Serial Number: 36f972f4
  Key Usage: Signature
 
CA Certificate
  Status: Available
  Certificate Serial Number: 36f972e5
  Key Usage: Not Set
 
RA KeyEncipher Certificate
  Status: Available
  Certificate Serial Number: 36f972f3
  Key Usage: Encryption
 

Step 10   Save your configuration:

ca save all

write memory

 

What to Do Next

After you configure CA interoperability, configure IKE and then IPSec. For IKE configuration, see "Configuring IKE." For IPSec configuration, see "Configuring IPSec."


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Posted: Mon Jun 10 16:44:00 PDT 2002
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