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Host and Service Certificates

Host and service certificates are used to securely identify your system and to establish encrypted connections between services and clients in the OSG. Host certificates can be used by any service running on your system. In contrast, service certificates are used to identify specific services on your machine. For example, HTCondor-CE typically uses a host certificate while RSV, Gratia, Tomcat, and Apache httpd use service certificates. Technically, the primary difference between a host certificate and service certificate is in the common name (CN) field of the certificate. A host certificate's CN contains the hostname (e.g. while a service certificate will prepend a service name to the hostname (e.g. http/ for an Apache httpd service certificate).

Since October 2015 the OSG has run its own OSG CA service that handled host and service certificate requests. At the end of May 2018, this service will be retired; see the policy details here. To replace the OSG CA service, we suggest using one or more of the following services depending on your site's needs:


Certificates issued from the OSG CA before the service retirement will still be valid until they expire. Therefore, we recommend that you request certificates for any currently existing or planned hosts and services prior to retirement.

After reading this document you should be able to apply for and install a host or service certificate on a grid resource. This document does not explain how to apply for a grid user certificate. To learn how to apply for a grid user certificate click here instead!

Before Starting

Before requesting a new host or service certificate, you should use openssl to check if you have a valid certificate already. If so, you may safely skip this document:

[email protected] $ openssl x509 -in /etc/grid-security/hostcert.pem -subject -issuer -dates -noout
subject= /DC=org/DC=opensciencegrid/O=Open Science Grid/OU=Services/
issuer=/DC=org/DC=cilogon/C=US/O=CILogon/CN=CILogon OSG CA 1
notBefore=Jan  4 21:08:09 2010 GMT
notAfter=Jan  4 21:08:09 2011 GMT

Requesting InCommon Host Certificates

Many institution in the United States already subscribe to InCommon and offer certificate services. If your institution is in the list of InCommon subscribers, continue with the instructions below. If your institution is not in the list and Let's Encrypt certificates do not meet your needs, please contact us.

  1. Generate a Certificate Signing Request (CSR) and private key:

    [email protected] # openssl req -nodes -new -newkey rsa:2048 -sha256 -out req.pem -keyout hostkey.pem

    When prompted, use your institution's information for the Country, State or Province, Locality (city), and Organization Name fields then the hostname for the Common Name field.


    Your institution may require more information in the request. Try using the CSR generated above in your initial request.

  2. Set the permissions on the private key:

    [email protected] # chmod 0600 hostkey.pem
  3. Find your institution-specific InCommon contact (e.g. UW-Madison InCommon contact) and submit the CSR that you generated above, asking for the certificate to be signed by the InCommon IGTF CA

  4. After the certificate has been issued by your institution, download it on its intended host and copy over the key you generated above.
  5. Verify that the issuer CN field is InCommon IGTF Server CA:

    $ openssl x509 -in <PATH TO CERTIFICATE> -noout -issuer
    issuer= /C=US/O=Internet2/OU=InCommon/CN=InCommon IGTF Server CA
  6. Install the host or service certificate

Requesting Host Certificates Using Let's Encrypt

Let's Encrypt is a free, automated, and open CA frequently used for web services; see the security team's position on Let's Encrypt for more details. Let's Encrypt can be used to obtain host certificates as an alternative to InCommon if your institution does not have an InCommon subscription.

The letsencrypt software (AKA certbot) can be obtained from the EPEL 7 yum repo:

[email protected] # yum install certbot

If you have any service running on port 80, you will have to disable it temporarily to obtain certificates, as letsencrypt needs to bind on it temporarily in order to verify the host. For instance, if you already have an HTCondor-CE set up with the HTCondor-CE View service running, stop the HTCondor-CE View service, as it listens on port 80.

Run the following command to obtain the host certificate with Let's Encrypt:

[email protected] # certbot certonly --standalone --email <ADMIN_EMAIL> -d <HOST>

Set up hostcert/hostkey links:

[email protected] # ln -s /etc/letsencrypt/live/*/cert.pem /etc/grid-security/hostcert.pem
[email protected] # ln -s /etc/letsencrypt/live/*/privkey.pem /etc/grid-security/hostkey.pem
[email protected] # chmod 0600 /etc/letsencrypt/archive/*/privkey*.pem

Before the host certificate expires, you can renew it with:

[email protected] # certbot renew

To automate renewal monthly with a cron job; for example you can create /etc/cron.d/certbot-renew with the following contents:

* * 1 * * root certbot renew

Requesting Host/Service Certificates Using the Command Line

The OSG PKI Command Line Clients are tested to work on Python version 2.4+. They have not been tested on Python version 3. In order to proceed you will also need:

  • an X.509 user certificate
  • Grid Admin privileges

As with all OSG software installations, there are some one-time (per host) steps to prepare in advance:


If you would like to request a host or service certificate without obtaining Grid Admin privileges, see this section.

Requesting Grid Admin privileges

A Grid Admin is a person associated with a Virtual Organization (VO) that has been given privileges to automatically approve host certificate requests for a given domain and any sub-domain. For example, a Grid Admin for the domain would be able to approve host or service certificate requests for,,, etc.

If you do not have Grid Admin privileges, you can request them here after obtaining your user certificate.

Installing the OSG PKI command line client

The scripts needed to request host or service certificates are contained in the osg-pki-tools RPM. Install it by running the following:

[email protected] # yum install osg-pki-tools

Please refer to this documentation for full documentation of the osg-pki-tools.

Validating your X.509 user certificate

Make sure you can create a valid grid proxy with voms-proxy-init or grid-proxy-init. For example :

[email protected] $ voms-proxy-init 
Enter GRID pass phrase for this identity:
Your identity: /DC=org/DC=opensciencegrid/O=Open Science Grid/OU=Services=People/CN=Alain Roy 424511
Creating temporary proxy ................................................................................. Done
Contacting [/DC=org/DC=opensciencegrid/O=Open Science Grid/OU=Services/] "GLOW" Done
Creating proxy ..................................................................... Done

Your proxy is valid until Fri Dec  2 01:32:47 2011

Requesting host certificates

The osg-gridadmin-cert-request script only supports requesting host certificates that are in the same domain. The certificates are stored with the format of <hostname>.pem and the corresponding key is stored as <hostname>-key.pem. For example:

  • To request a host certificate for

    [email protected] $ osg-gridadmin-cert-request -H
  • To request a host certificate for with Subject Alternative Names (SANs), use the -a flag for each SAN:

    [email protected] $ osg-gridadmin-cert-request -H -a -a
  • To request more than one host certificate, you can provide a file with one host per line and optional SANs separated with spaces. The following example would request three certificates; one for, one for, and one for with the SANs and

    If the above contents were saved to hostfile, run the following command to request multiple certificates:

    [email protected] $ osg-gridadmin-cert-request -f hostfile

Installing host certificates

Finally, install the certificate in the default location /etc/grid-security/:

[email protected] # cp ./ /etc/grid-security/hostcert.pem
[email protected] # chmod 444 /etc/grid-security/hostcert.pem
[email protected] # cp ./ /etc/grid-security/hostkey.pem
[email protected] # chmod 400 /etc/grid-security/hostkey.pem

Requesting and installing a service certificate

Requesting service certificates

To request a service certificate, use the same osg-gridadmin-cert-request command used to request host certificates but prepend the service name, <SERVICE>, to the requested hostname:

[email protected] $ osg-gridadmin-cert-request -H <SERVICE>/


All methods for requesting host certificates can also be used to request service certificates

Installing service certificates

Since a single host can run multiple services, service certificates must be placed in their own directory.

  1. Create a directory indicating the name of the service, <SERVICE>, under /etc/grid-security/.

    [email protected] # mkdir /etc/grid-security/<SERVICE>
  2. Copy and rename the service certificate and key to the <SERVICE> directory that you created above:

    [email protected] # cp ./<SERVICE> /etc/grid-security/<SERVICE>/<SERVICE>cert.pem
    [email protected] # cp ./<SERVICE> /etc/grid-security/<SERVICE>/<SERVICE>key.pem

    For example, the service certificate for an Apache httpd service should be installed in /etc/grid-security/http:

    [email protected] # cp ./ /etc/grid-security/http/httpcert.pem
    [email protected] # cp ./ /etc/grid-security/http/httpkey.pem
  3. Set the appropriate permissions on the service certificate and key

    [email protected] # chmod 444 /etc/grid-security/<SERVICE>/<SERVICE>cert.pem
    [email protected] # chmod 400 /etc/grid-security/<SERVICE>/<SERVICE>key.pem
  4. Set the ownership of the directory and its underlying files to the Unix user, indicated as <USER>, who runs the service:

    [email protected] # chown -R <USER>:<USER> /etc/grid-security/<SERVICE>/

    For example, both the Apache and Tomcat services are run by the tomcat user:

    [email protected] # chown -R tomcat:tomcat /etc/grid-security/http/

Requesting Host/Service Certificate Using OIM

If you do not have Grid Admin privileges, please use OIM to request any host or service certificates that you may need. The OSG PKI Certificate Request & Management System can be found at: Alternatively, you can request Grid Admin privileges here after obtaining your user certificate.

Frequently Asked Questions

Can I use any host to request a certificate for a different host?

YES, you can use any host to create a certificate request as long as the hostname for the certificate is a fully qualified domain name.

May I reuse my host certificate as a service certificate?

NO! For security reasons, please do not use clones of your host certificate for additional certificates even though it's technically possible.

How do I renew a host/service certificate?

There is no separate procedure. Simply ask for a new certificate the same way you asked for it the previous time.

I get a "GSS authentication failure" when users try to authenticate with my site?

You likely used an alias for the host instead of the fully qualified domain name when you generated the certificate request. This can cause the GSS authentication failures similar to the following when a user tries to authenticate to the host after your certificate is installed:

GSS authentication failure 
GSS Major Status: General failure 
GSS Minor Status Error Chain: 
Error during delegation: Delegation protocol violation 
Failure: GSS failed Major:000d0000 Minor:00000001 Token:00000000 

How can I check if I have a host certificate installed already?

By default the host certificate key pair will be installed in /etc/grid-security/hostcert.pem and /etc/grid-security/hostkey.pem. You can use openssl to access basic information about the certificate:

[email protected] # openssl x509 -in /etc/grid-security/hostcert.pem -subject -issuer -dates -noout
subject= /DC=org/DC=opensciencegrid/O=Open Science Grid/OU=Services/
issuer= /DC=org/DC=cilogon/C=US/O=CILogon/CN=CILogon OSG CA 1
notBefore=Apr  8 00:00:00 2013 GMT
notAfter=May 17 12:00:00 2014 GMT

How can I check the expiration time of my installed host certificate?

If you installed the Certificates Script Package you can use grid-cert-info to retrieve information about the certificate:

[email protected] # grid-cert-info -file /etc/grid-security/hostcert.pem -startdate -enddate
Jan  4 21:08:41 2010 GMT
Jan  4 21:08:41 2011 GMT

Alternatively you can use openssl:

[email protected] # openssl x509 -in /etc/grid-security/hostcert.pem -dates -noout
notBefore=Jan  4 21:08:41 2010 GMT
notAfter=Jan  4 21:08:41 2011 GMT