Setup Your Own Certificate Authority (CA) on Linux and Use it in a Windows Environment

In this previous post, I deployed a test IIS Server and used a self signed SSL Certificate to encrypt the HTTP traffic. I am sure everyone have seen this page in Internet Explorer:

When I clicked “View Certificate”, I saw the following:

We can see that certificate is issued by the same entity as the site-name itself. We can also see that the Root CA is not trusted. Since this is a self-signed Certificate, you are the Root CA in a manner of speaking. My goal is to get rid of that message and to become a “trusted” Certificate Authority (CA) in my local Windows Environment.

Choosing a free Certificate Authority software

If we take a look at this wikipedia page, we will see the following list of available software:

• DogTag
• EJBCA
• gnoMint
• OpenCA
• OpenSSL, which is really an SSL/TLS library, but comes with tools allowing its use as a simple certificate authority.
• r509
• XCA

There is actually one more that I ran into, it’s called tinyCA.

Using OpenSSL Commands to Setup a CA

DogTag, EJBCA, and OpenCA were full blown Public-Key Infrastructure (PKI) applications and I didn’t need all of the extra functionally. There are a lot of examples on how to setup your own CA with openssl:

• Creating a Certificate Authority and signing the SSL certificates using openssl
• Become your own SSL Certificate Authority

I have done that before and when you are managing a lot of different certificates the process is not very scalable. Also, if you don’t keep doing it, you have to re-trace your steps to remember how the setup works. There is also a Perl script that is included to ease the CA setup, that script is called CA.pl. Depending on your Linux distribution you have find the right package that contains that script. Here is where I found it on my Fedora install:

[elatov@klaptop ~]$ yum provides "*/CA.pl*"
Loaded plugins: langpacks, presto, refresh-packagekit, remove-with-leaves
1:openssl-perl-1.0.1c-7.fc18.x86_64 : Perl scripts provided with OpenSSL
Repo        : fedora
Matched from:
Filename    : /etc/pki/tls/misc/CA.pl
Filename    : /usr/share/man/man1/CA.pl.1ssl.gz

You can check out examples from “CA.pl - friendlier interface for OpenSSL certificate programs on how to use the Perl script; here is a very high level overview:

#Generate CA Certificate
CA.pl -newca

#Generate a Certificate Signing Request (CSR)
CA.pl -newreq

#Sign the CSR with your CA key
CA.pl -sign

TinyCA

This time around I wanted a pretty GUI that will handle all of the openssl commands for me and store the certificate database as well. Maybe I am getting lazy? or hopefully efficient. Among the other applications, TinyCA stood out the most. I found many guides on how to use it:

• Create your own Certificate Authority with TinyCA
• Create your own CA with TinyCA2 (part 1)
• Create your own Certificate Authority with TinyCA2 and Debian Squeeze

As I started to install the software I noticed that it wasn’t part of the Fedora repositories:

[elatov@klaptop ~]$ yum search tinyca
Loaded plugins: langpacks, presto, refresh-packagekit, remove-with-leaves
Warning: No matches found for: tinyca
No Matches found

That didn’t stop me; I downloaded the application and installed it manually. After setting up my Root CA, the application crashed with the following error:

Use of uninitialized value $mday in concatenation (.) or string at /usr/share/perl5/Time/Local.pm line 116, <gen11> line 3.
Day '' out of range 1..31 at /usr/local/tinyca2/lib/OpenSSL.pm line 1050.

I found this bug and the issue was with a later version of openssl (which I had on my Fedora 18 install). The fix was included in Debian based distributions. However I was running Fedora and I didn’t want to keep patching the software manually, if it kept having issues. So I decided to try out gnomint.

Install Gnomint and Create a Root CA Certificate

Luckily Gnomint was part of the Fedora packages, so a simple:

yum install gnomint

Took care of all my troubles. Then running gnomint launched the GUI for me:

Then I clicked on “Add Autosigned CA certificate” and it showed me the “New CA” dialog:

Here is what I entered for my new CA certificate:

Then if you click “Next” you will see the “New CA Properties” window:

Choose what you think is necessary; the higher the bit count the better the encryption is. Click “Next” and you will be asked to provide the “CRL Distribution Point”. This is included with the Root CA Certificate. If a certificate is revoked, people can check for that at this “Destribution Point”/Link. I won’t be a public CA, so I left this blank:

I then clicked “OK” and my new Root CA Certificate was created:

Generate a new Certificate Request and Sign it with your Root CA Certificate in Gnomint

At this point we can generate a Certificate Signing Request (CSR) by clicking on “Add CSR”:

After “Inheriting CA Fields” we can click “Next” and fill out the Request:

I went ahead and requested for a “wildcard” (*.domain.com) certificate just to have one certificate cover my test windows domain. This way I can import one Certificate on both of my IIS servers. Clicking “Next” will take us to the Encryption details, I left the defaults here (I know with Windows as long as it’s above 2048 bits then it should work):

Clicking “OK” created the CSR:

To “Sign” the CSR, just right click on it and select “Sign”:

and the following window will show up:

Click “Next” and it will ask you to choose the CA to sign with:

After clicking “Next” we choose how long the certificate is valid for and what it can be used for:

The defaults were fine with me, clicking “OK” finished the process and I now had a signed certificate:

Check out the Gnomint Database

Save your database in gnomint and a file called ~/.gnomint/default.gnomint will be created. That is just an sqlite3 database, so we can check out the contents to make sure it looks good. So go ahead and open up the database:

[elatov@klaptop .gnomint]$ sqlite3 default.gnomint
SQLite version 3.7.13 2012-06-11 02:05:22
Enter ".help" for instructions
Enter SQL statements terminated with a ";"
sqlite>

Next list the available tables:

sqlite> .tables
ca_crl         ca_properties  certificates
ca_policies    cert_requests  db_properties

Lastly check out the certificates table:

sqlite> select * from certificates;
1|1|01|root-cert-elatov.local|1366488033|1555790433||-----BEGIN CERTIFICATE-----
xxx
-----END CERTIFICATE-----
|1|-----BEGIN RSA PRIVATE KEY-----
xxx
-----END RSA PRIVATE KEY-----
|C=US,ST=Colorado,L=Boulder,O=Home,OU=Me,CN=root-cert-elatov.local|C=US,ST=Colorado,L=Boulder,O=Home,OU=Me,CN=root-cert-elatov.local|0|:||39:3F:52:E5:F4:4F:F1:7F:48:73:A4:73:EB:F3:E0:C6:5A:4A:68:E8|39:3F:52:E5:F4:4F:F1:7F:48:73:A4:73:EB:F3:E0:C6:5A:4A:68:E8
2|0|02|*.elatov.local|1366489069|1524255469||-----BEGIN CERTIFICATE-----
yyy
-----END CERTIFICATE-----
|1|-----BEGIN RSA PRIVATE KEY-----
yyy
-----END RSA PRIVATE KEY-----
|C=US,ST=Colorado,L=Boulder,O=Home,OU=Me,CN=*.elatov.local|C=US,ST=Colorado,L=Boulder,O=Home,OU=Me,CN=root-cert-elatov.local|1|:1:|||39:3F:52:E5:F4:4F:F1:7F:48:73:A4:73:EB:F3:E0:C6:5A:4A:68:E8

That looks good to me.

Export the Signed Certificate in PKCS #12 Format from Gnomint

Now we need upload our signed Certificate to our IIS server to make sure it works okay. First, let go ahead and export the certificate from Gnomint. This is done by right clicking on our Cerficate and selecting “Export”:

After that, you will be presented to choose the format of the certificate. Choose “Both Parts”:

After clicking “Next”, you can choose to save the exported file on your computer. I called the file wild-elatov-local.pfx and stored it on my Desktop:

After clicking “Save”, you will be asked to password protect the file:

Click “OK” and you will now have the exported certificate in PKCS #12 format.

Confirm the Contents of a PKCS #12 Format Certificate

We can just use the openssl utility to quickly check out the contents of the certificate:

[elatov@klaptop Desktop]$ openssl pkcs12 -info -in wild-elatov-local.pfx
Enter Import Password:
MAC Iteration 1
MAC verified OK
PKCS7 Encrypted data: pbeWithSHA1And40BitRC2-CBC, Iteration 425
Certificate bag
Bag Attributes
    localKeyID: 61 0B C1 4D 47 04 88 1F B9 1D 28 4D 99 18 CC 3C E0 75 2E 94
    friendlyName: C=US,ST=Colorado,L=Boulder,O=Home,OU=Me,CN=*.elatov.local
subject=/C=US/ST=Colorado/L=Boulder/O=Home/OU=Me/CN=*.elatov.local
issuer=/C=US/ST=Colorado/L=Boulder/O=Home/OU=Me/CN=root-cert-elatov.local
-----BEGIN CERTIFICATE-----
xxx
-----END CERTIFICATE-----
PKCS7 Data
Shrouded Keybag: pbeWithSHA1And3-KeyTripleDES-CBC, Iteration 299
Bag Attributes
    localKeyID: 61 0B C1 4D 47 04 88 1F B9 1D 28 4D 99 18 CC 3C E0 75 2E 94
    friendlyName: C=US,ST=Colorado,L=Boulder,O=Home,OU=Me,CN=*.elatov.local
Key Attributes: <no Attributes>
Enter PEM pass phrase:
Verifying - Enter PEM pass phrase:
-----BEGIN ENCRYPTED PRIVATE KEY-----
xxx
-----END ENCRYPTED PRIVATE KEY-----

The Export password and the PEM password are the same one that we used during the “Export” process from Gnomint. The above looks good: the Issuer is correct and so is the subject.

Import the PKCS #12 Certificate into the IIS Server

Upload the .pfx file to the IIS server:

Then start up IIS manager:

inetmgr

Then click on “Server Certificates”:

After you double click on “Server Certificate” you will see a list of current certificates, I only have the self signed certificate:

Now click on “Import” from the top left and the Import Certificate Dialogue will show up. Hit “Browse” and point to our certificate and enter the Export password:

After you click “OK” you will see the newly import Certificate:

Now if you click on “Default Web Site” you can click on “Bindings” from the left pane:

Then select the “https” binding:

Lastly select “Edit” and select the newly imported SSL certificate:

To test out the new Certificate, open up the browser to the same site and you will still see the same “ssl” warning, but if you click on “View Certificate” you will see the following:

We can see that the “Issue By” and the “Issue To” fields look correct.

Add Your Own Root CA to Trusted Root Certification Authorities on the DC Server

Now that we our own CA we need to import it to our Domain Controller and push it to any machine that is part of our domain. This way any computer part of the Domain will trust our SSL certificates. First we need to export our Root CA from Gnomint.

Export Root CA Certificate from Gnomint

To export the Root CA Certificate we just have to do the same thing as with the regular Certificate. Right click on the Certificate and select “Export”. During the Export process choose “Public Only” for the format:

If all is well you should see a succesful export:

Confirm Contents of the Root CA .PEM File

We will again use openssl to check the contents of SSL certificate:

[elatov@klaptop Desktop]$ openssl x509 -in root-ca-elatov-local.pem -text -noout
Certificate:
    Data:
        Version: 3 (0x2)
        Serial Number: 1 (0x1)
    Signature Algorithm: sha1WithRSAEncryption
        Issuer: C=US, ST=Colorado, L=Boulder, O=Home, OU=Me, CN=root-cert-elatov.local
        Validity
            Not Before: Apr 20 20:00:33 2013 GMT
            Not After : Apr 20 20:00:33 2019 GMT
        Subject: C=US, ST=Colorado, L=Boulder, O=Home, OU=Me, CN=root-cert-elatov.local
        Subject Public Key Info:
            Public Key Algorithm: rsaEncryption
                Public-Key: (2048 bit)
                Modulus:
                    00:d0:2f:05:bd:2a:4c:f0:3c:23:e7:00:b9:67:d9:
                Exponent: 65537 (0x10001)
        X509v3 extensions:
            X509v3 Basic Constraints: critical
                CA:TRUE
            X509v3 Key Usage: critical
                Certificate Sign, CRL Sign
            X509v3 Subject Key Identifier:
                39:3F:52:E5:F4:4F:F1:7F:48:73:A4:73:EB:F3:E0:C6:5A:4A:68:E8
            X509v3 Authority Key Identifier:
                keyid:39:3F:52:E5:F4:4F:F1:7F:48:73:A4:73:EB:F3:E0:C6:5A:4A:68:E8

    Signature Algorithm: sha1WithRSAEncryption
         42:d1:be:db:42:ab:50:25:d2:bd:47:fc:05:f5:01:81:75:27:

All of the above looks good to me.

Import the Root CA into the Windows DC Server

Upload the Root CA Certificate to the DC Server and then launch the “Group Policy Management” console:

gpmc.msc

Next let’s expand the following hierarchy: Forest -> Domains -> “elatov.local” -> “Group Policy Objects”:

Then right click on “Defaul Domain Policy” and select “Edit” and you will see the following:

Now let’s expand the hierarchy as follows: “Default Domain Policy” -> “Computer Configuration” -> “Policies” -> “Windows Settings” -> “Security Settings” -> “Public Key Policies” -> “Trusted Root Certification Authorities”:

Right click on “Trusted Root Certification Authorities” and select “Import”, then point to the Root CA:

After clicking “Next” it will let you know that it will add the certificate into the “Trusted Root Certifications Authorities”:

Lastly click “Next” and then “Finish” and you will the following message:

And in the end you will see your root CA imported:

Now you can close the GPO consoles.

Get the new Group Policies to the Windows Clients

Now that we have added our Root CA Certificate to our Group Policy, we need to update the policy on the client. Open up a command prompt on the Windows 7 client and run:

C:\Windows\system32>gpupdate /force
Updating Policy...

User Policy update has completed successfully.
Computer Policy update has completed successfully.

Or you can log out and log back in as well.

Confirm the Root CA Certificate is on the Domain Joined Windows Client

Now that we have synced the new Group Policies from our Domain controller, we should see our Root CA. On the windows client run:

certmgr.msc

and the “Certificate Manager” will start up:

If you expand “Trusted Root Certification Authorities” -> “Certificates”, you should your Root CA in there:

Now going to the site: shows me the following page without any warnings:

And checking out the SSL certificate we see the following:

It’s trusted and I feel so much safer.