KB ID 0001312

Problem

Following on from Part Two, now we have an offline Root CA, and a CRL server, our next step is defined by our PKI design, are we three tier, or two tier? (Look in Part One for a definition).

Solution

As previously mentioned, Microsoft just treats Intermediate CAs and Issuing CA’s as the same thing (SubCAs). So the next step is identical for either. But I would suggest one difference, If I was deploying an Intermediate CA, I would have “LoadDefaultTemplates=0” in the CAPolicy.inf file, and for an Issuing server I would not, (that’s just my personal preference).

I’m going to continue this piece for a two tier PKI deployment. And my next SubCA will be an Issuing CA.

Create your SubCA CAPolicy.inf file and save it to C:\Windows

[box]

[Version]
Signature="$Windows NT$"
[PolicyStatementExtension]
Policies=InternalPolicy
[InternalPolicy]
OID= 1.2.3.4.1455.67.89.5
Notice="Legal Policy Statement"
URL=http://pki.cabench.com/pki/cps.txt
[Certsrv_Server]
RenewalKeyLength=2048
RenewalValidityPeriod=Years
RenewalValidityPeriodUnits=15
CRLPeriod=weeks
CRLPeriodUnits=1
CRLDeltaPeriod=Days
CRLDeltaPeriodUnits=0

[/box]

Launch Server Manager > Manage > Add Roles and Features.

Role Based > Next > Select the Local Server >Next > Active Directory Certificate Services > Add Features > Next.

No additional Features are Needed > Next > Next > Select Certification Authority > Optional*: Select Certificate Authority Web Enrolment > Next.

*Note: This gives you the nice registration website for certificates.

Next > Install > Close.

Configure Active Directory Certificate Services.

Next > Select ‘Certification Authority’ and ‘ Certificate Authority Web Enrolment’, if you selected it above > Next > Enterprise CA > Next.

Subordinate CA > Next > Create New Private Key > Next > Change the Hash algorithm to SHA256 > Next.

Give the CA a sensible Name > Next > Select ‘Save certificate request to a file on the target machine’ > Next.

Next > Next > Install > Close.

Note: The warning is fine, we haven’t installed the certificate yet, that’s our next step

Copy your certificate request file, (ending .req) and put it on your floppy drive. 

Note: I’m aware we are in the 21st century! I’m using virtual floppy drives.

Present the floppy drive to your offline Root CA and execute the following command;

[box]certreq -submit “A:\filename.req“[/box]

When prompted with the CA name > OK > Take a note of the RequestID you need this in a moment. (Leave the command window open!)

Open the Certificate Services Management Console > Server-name > Pending Requests > Locate your request > Issue the certificate.

Back at command line issue the following command;

[box]certreq -retrieve {RequestID} “A:\SubCA.crt“[/box]

When prompted with the CA name > OK.

Check the certificate has appeared on your floppy drive, and present that back to your SubCA server > Open the Certificate Services Management console > Server-name > All Tasks > Install CA Certificate > Locate the cert  > Open.

Start the Service (If it errors at this point you may have a problem with your CRL server see the following link for a temporary workaround until you can fix the CRL).

Certificate Services – Disable CRL Checking

Troubleshooting: Open an MMC Snap-in and Add the Enterprise PKI snap-in to point you towards problems.

At this point I like to copy the Sub CA Cert to C:\Windows\Sytem32\Certsrv\CertEnroll. You should see the CRL for the SubCA already there (and maybe a delta CRL like the image below).

Now we are going to publish those into AD, open an administrative command window and issue the following commands;

[box]

cd  C:\Windows\Sytem32\Certsrv\CertEnroll
certutil -dspublish -f SubCA.crt SubCA
certutil –addstore –f root SubCA.crt
certutil –addstore –f root SubCA.crl
certutil -dspublish  SubCA.crl

[/box]

 

Restart Certificate Services;

[box]

net stop certsvc
net start certsvc

[/box]

Back in Certificate Services > Properties > Extension > Remove the http and file entries. NOT the ldap or the one that’s pointing to C:\Windows.

With CRL Distribution Point showing > Add > Type in http://pki.{your-domain}/pki/<CaName><CRLNameSuffix><DeltaCRLAllowed>.crl 

Note: You can add the variables in to avoid typing them, DON’T FORGET to put .crl on the end!

OK.

With your new URL selected, tick;

• Include in CRLs. Clients use this to find DeltaCRL locations.
• Include in the CDP extension of issued certificates.

Apply > OK > Services will Restart.

Once Again, click Add, this time type in the UNC path to your hidden PKI share on your CRL Server, e.g.

\\pki.{your-domain}\pki$\<CaName><CRLNameSuffix><DeltaCRLAllowed>.crl

Note: You can add the variables in to avoid typing them, DON’T FORGET to put .crl on the end!

OK.

With your UNC path selected, tick;

• Publish CRLs to this location.
• Publish Delta CRLs to this location.

Apply  > OK > Services will restart.

That’s your PKI environment stood up and ready to go, you may also want to setup OCSP, see the following article;

Microsoft Certificate Services Configuring OCSP

You can now issue certificates, some of the things you might want to consider setting up are;

Windows Server 2012 – Enable LDAPS

Deploying Certificates via ‘Auto Enrollment’

Windows Server 2012 – Secure RDP Access with Certificates

Install and Configure Certificate Enrolment Policy Web Service

Related Articles, References, Credits, or External Links

NA