Cool Solution - Creation and management of user and Windows certificates
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Users and Windows computers within the UCS domain can be supplied with a custom certificate using the UMC. The private and public part of the certificate will be stored in the filesystem of the Domaincontroller Master, while the public part will be also imported into the LDAP. The certificates can then be used for e.g. authentication, signing e-mails, or securing connections to the Windows computer.
This documentation guide you through the installation of the user and windows certificate extension on your system and creating individual certificates. Certificates are created as DER and PEM files.
The software is designed to operate on the UCS DC Master. To install the packages you need to enable the Cool Solution repository at first.
There has been a change in the certification mechanism introduced with Errata 213 for UCS 4.1. Please ensure that you are at least on this Errata level before following the next steps.
Next, you must install the package univention-ldap-usercert on the DC Master server and should install the package on every additional DC Backup servers. This can be achieved by using either the UMC module Package management or invoke the following command:
Additionally you must install the packages univention-usercert on the DC Master. Optionally, you can also install univention-windowscert for the creation of certificates for windows clients. Again you can either use the UMC module Package management or the command line:
univention-install univention-usercert univention-windowscert
During the installation, new UCR variables will be created (see below) and the Univention directory listener daemon will be restarted.
If not run automatically, check if joinscripts must be executed.
Managing user certificates
To create a user certificate, open the [Options] tab in the user's LDAP object and select "Public key infrastructure account".
Now save and reopen the user object and switch to the User Certificate tab and select "Create/Revoke User Certificate".
When saving, the certificate is created and saved in the directory provided in ssl/usercert/certpath in a subdirectory with the user's UID. By default, only the user itself and the group entered in ssl/usercert/admingroup have read permission on the files. It is recommended to create a file share of the folder containing the certificates, so users can access them remotely.
Note: Optionally, the standard valid time of the certificate can be overwritten here. If the field is left blank, the standard valid time from the UCR variable ssl/usercert/days will be used.
When a certificate is to be revoked, it is sufficient to untick "Create/Revoke User Certificate". The certificate files are removed from the LDAP, but not deleted from the filesystem. If the UCS root CA was used to sign the user's certificate, an entry is made into the Certificate Revocation List specified by /etc/univention/ssl/ucsCA/crl/.
When a certificate needs to be renewed, it is sufficient to tick "Renew User Certificate" and save the changes made. The old certificate will then be revoked and a new one will be created with the settings from the former certificate.
Managing windows computer certificates
To create a computer certificate, open the Certificate tab on the computer's LDAP option and select "Create/Revoke Certificate".
When a certificate is to be revoked, it is sufficient to untick "Create/Revoke Certificate". The certificate files are removed from the LDAP, but not deleted from the filesystem. If the UCS root CA was used to sign the computer's certificate, an entry is made into the Certificate Revocation List specified by /etc/univention/ssl/ucsCA/crl/.
When a certificate needs to be renewed, it is sufficient to tick "Renew Certificate" and save the changes made. The old certificate will then be revoked and a new one will be created with the settings from the former certificate.
It is also possible to upload certificates for users and windows computers in the UMC. In this case, the certificates have to be DER encoded before the upload. If you have a PEM encoded certificate, you can convert your certificate to DER with
openssl on the commadline:
openssl x509 -in /path/to/certificate.PEM -out /path/to/certificate.DER -outform DER
UCR variables and their functionality
During the installation, several new UCR variables will be created. They are as follows:
|UCR variable||Default value||Description|
|ssl/usercert/UID/extensionsfile||<empty>||Apply the custom settings only to users named here.|
|ssl/usercert/admingroup||DC Backup Hosts||Besides the owner of the certificate, this group has read permissions on the certificate files.|
|ssl/usercert/ca||ucsCA||Folder where the Root CA files are stored (located in ssl/usercert/sslbase).|
|ssl/usercert/certldapmapping/cn||uid||Maps, which identifier from the user's CN is mapped with the user certificate.|
|ssl/usercert/certldapmapping/email||mailPrimaryAddress||Maps, which e-mail address is mapped with the user certificate.|
|ssl/usercert/certldapmapping/locality||l||Maps, which location is mapped with the user certificate.|
|ssl/usercert/certldapmapping/organization||o||Maps, which organization is mapped with the user certificate.|
|ssl/usercert/certldapmapping/organizationalunit||<empty>||Maps, which business unit is mapped with the user certificate.|
|ssl/usercert/certldapmapping/state||<empty>||Maps, which state is mapped with the user certificate.|
|ssl/usercert/certpath||/etc/univention/ssl/user||Default path where the user certificates are saved in a UID labeled subdirectory.|
|ssl/usercert/days||1825||Default time that a certificate is valid. Can be overwritten in the user's UMC object.|
|ssl/usercert/default/country||Defaults to Root CA's country||By default, no LDAP mapping exists for this variable, the value from ssl/country will be used.|
|ssl/usercert/default/email||Defaults to Root CA's e-mail||By default, no LDAP mapping exists for this variable, the value from ssl/email will be used.|
|ssl/usercert/default/locality||Defaults to Root CA's location||By default, no LDAP mapping exists for this variable, the value from ssl/locality will be used.|
|ssl/usercert/default/organization||Defaults to Root CA's organization||By default, no LDAP mapping exists for this variable, the value from ssl/organization will be used.|
|ssl/usercert/default/organizationalunit||Defaults to Root CA's business unit||By default, no LDAP mapping exists for this variable, the value from ssl/organizationalunit will be used.|
|ssl/usercert/default/state||Defaults to Root CA's state||By default, no LDAP mapping exists for this variable, the value from ssl/state will be used.|
|ssl/usercert/extensionsfile||<empty>||Overwrite the default openSSL settings with custom settings.|
|ssl/usercert/ldapimport||yes||If set to yes/true, the public certificate is imported into the LDAP.|
|ssl/usercert/passwordchars||<empty>||Any number can be entered here to specify the password length.|
|ssl/usercert/pkcs12/chain||yes||Whether the PKCS12 chain is saved in the certificate.|
|ssl/usercert/sslbase||/etc/univention/ssl/||SSL root directory.|
|ssl/windowscert/UID/extensionsfile||<empty>||Apply the custom settings only to computers named here.|
|ssl/windowscert/admingroup||DC Backup Hosts||Besides the owner of the certificate, this group has read permissions on the certificate files.|
|ssl/windowscert/ca||ucsCA||Certificate to sign the computer certificate with.|
|ssl/windowscert/certldapmapping/cn||cn||Maps, which identifier from the computer's CN is mapped with the computer certificate.|
|ssl/windowscert/certldapmapping/email||<empty>||Maps, which e-mail address is mapped with the computer certificate.|
|ssl/windowscert/certldapmapping/locality||<empty>||Maps, which location is mapped with the user certificate.|
|ssl/windowscert/certldapmapping/organization||<empty>||Maps, which organization is mapped with the user certificate.|
|ssl/windowscert/certldapmapping/organizationalunit||<empty>||Maps, which business unit is mapped with the user certificate.|
|ssl/windowscert/certldapmapping/state||<empty>||Maps, which state is mapped with the user certificate.|
|ssl/windowscert/certpath||/etc/univention/ssl/windows-hosts||Path where the certificates are saved. Only the computer account and the group in ssl/windowscert/admingroup can access this directory.|
|ssl/windowscert/days||1825||Default time that a certificate is valid. Can be overwritten in the computers's UMC object.|
|ssl/windowscert/extensionsfile||<empty>||Overwrite the default openSSL settings with custom settings.|
|ssl/windowscert/ldapimport||yes||Whether the public certificate should be imported automatically.|
|ssl/windowscert/passwordchars||<empty>||Any number can be entered here to specify the password length.|
|ssl/windowscert/pkcs12/chain||yes||Whether the PKCS12 chain is saved in the certificate.|
|ssl/windowscert/sslbase||/etc/univention/ssl/||Base directory where all SSL certificates are saved.|
Apache and SSL certificates
It is possible to configure the Apache webserver so that only users with a valid certificate, imported in the user web browser, can access a webpage or directory using HTTPS.
To configure this, either expand an existing site or create a new one in
Attention: When expanding an existing site, please make sure that the file is not managed by a UCR template, as it may be overwritten when corresponding UCR variables are changed! Either expand the template file (handle with care!) or create a new site!
Put the following code into the site file:
# Revocation list SSLCARevocationFile /etc/univention/ssl/ucsCA/crl/crl.pem # Protected directory <Directory /var/www/statistik> Options Indexes FollowSymLinks MultiViews Order allow,deny allow from all SSLVerifyClient require SSLVerifyDepth 5 SSLCACertificateFile /etc/univention/ssl/ucsCA/CAcert.pem SSLCACertificatePath /etc/univention/ssl/ucsCA/ SSLOptions +FakeBasicAuth SSLRequireSSL </Directory>
If a new site is created, the site must be enabled with
After activating a new site, or expanding an existing one, the Apache webserver must be reloaded:
invoke-rc.d apache2 reload
Handling of revoked certificates
Apache only checks the certificate revocation list when the service is reloaded. It is adviced to create a cronjob using UCR that reloads the service on a daily basis:
ucr set \ cron/reload-apache2/command="invoke-rc.d apache2 reload" \ cron/reload-apache2/time="0 0 * * *"
The above cronjob reloads Apache once a day at midnight.
There is a version of this article for UCS 4.0.