Secure Authentication between Zimbra and AD
Secure Authentication between Zimbra and AD (self-signed certificate)
How to configure authentication with Active Directory using SSL.
Before everything else, make sure that the non-ssl AD authentication is working, by following that article.
1. Review the following article to familiarize yourself with the authentication with AD from Zimbra side in AdminUI. The only difference is that in the "Active Directory Settings" , the Use SSL: tick box is selected:
2. Copy the Zimbra CA file to the DC:
- Use tools such as WinScp to copy the /opt/zimbra/ssl/zimbra/ca/ca.pem file to the DC.
- Copy the ca.pem file in a directory and rename it to ca.crt.
3. Install the Zimbra certificate authority (CA) on the domain controller:
- Start->Run > Type mmc. This will open the Microsoft Management Console.
- Click "File" > "Add/Remove Snap-In..." to open the "Add Standalone Snap-in" dialog.
- From the Available snap-ins on the left, select "Certificates" and press "Add".
- Select "Computer account" and press "Next".
- Select "Local computer" and press "Finish"
- Click "Ok" to close the "Add/Remove Snap-in" dialog.
Once the "Certificates snap-in" is open, expand the "Certificates" node under "Trusted Root Certification Authorities". Right-click on the "Certificates" node, select "All Tasks" -> "Import...", and import the Certificate Authority (in my case "ca.crt") you copied from Zimbra. Accept the default location: Trusted Root Certification Authorities
3. The next step is to create a csr. For this purpose we will use Microsoft's certreq utility. To generate csr, we need to create a *.inf file. Below is a sample *.inf file you ca use. Make sure that the "Subject" line contains the FQDN of the AD server.
- Open a text editor and paste the following text, including the beginning and ending tags, into the file. Make sure no CR/LF character is added to the "Subject =" line when you copy and paste the text. Remove if any:
;----------------- request.inf ----------------- [Version] Signature="$Windows NT$" [NewRequest] Subject = "CN=mail.example.com, OU=Organizational_Unit, O=Organization, L=City, S=State, C=Country" ; Replace mail.example.com with the FQDN of your AD server's FQDN. ; Replace the remaining Subject attributes. KeySpec = 1 KeyLength = 2048 HashAlgorithm = SHA256 Exportable = TRUE MachineKeySet = TRUE SMIME = False PrivateKeyArchive = FALSE UserProtected = FALSE UseExistingKeySet = FALSE ProviderName = "Microsoft RSA SChannel Cryptographic Provider" ProviderType = 12 RequestType = PKCS10 KeyUsage = 0xa0 [EnhancedKeyUsageExtension] OID=220.127.116.11.18.104.22.168.1 ; this is for Server Authentication ;-----------------------------------------------
- Update the Subject attributes with appropriate values. For example: CN=mail.example.com
4. Once you have a inf file, generate a Certificate Signing Request (CSR) using certreq.
certreq -new ad.inf ad.csr
5. Sign the certificate.
openssl x509 -req -days 365 -in ad.csr -CA ca.crt -CAkey /opt/zimbra/ssl/zimbra/ca/ca.key -set_serial 01 -out ad.crt
6. Accept the Certificate After you get your signed certificate, you will need to "Accept" it using the certreq utility:
certreq -accept ad.crt
This will install the cert in the Windows certificate store and it will be available to those services and products that make use of the Windows certificate store. These products include but are not limited to: IIS, Exchange, Active Directory (LDAPS), Terminal Services and Microsoft Management Console (MMC).
7. Install the certificate.
From n Step 2, open the "Certificates snap-in", expand the "Certificates" node under "Personal". Right-click on the "Certificates" node, select "All Tasks" -> "Import...", and import the "ad.crt".
8. Restart AD server
To make sure the SSL is working, we can use ldp.exe. Click Start> Run > type ldp.exe and open it. At top left, click on "Connection" > "Connect...".