This document describes how to get host certificates. For instructions on how to get user certificates, see the User Certificates document.
Host certificates are X.509 certificates that are used to securely identify servers and to establish encrypted connections between services and clients. In the OSG, some grid resources (e.g., HTCondor-CE, XRootD, GridFTP) require host certificates. If you are unsure if your host needs a host certificate, please consult the installation instructions for the software you are interested in installing.
To acquire a host certificate, you must submit a request to a Certificate Authority (CA). We recommend requesting host certificates from one of the following CA services:
- InCommon: an IGTF-accredited CA for services that interact with the WLCG; requires a subscription, generally held by an institution
- Let's Encrypt: a free, automated, and open CA frequently used for web services; see the security team's position on Let's Encrypt for more details
- If neither of the above options work for your site, the OSG also accepts all IGTF-accredited CAs.
Use this page to learn how to request and install host certificates on an OSG resource.
Before requesting a new host certificate, use
openssl to check if your host already has a valid certificate, i.e. the
present is between
notAfter dates and times.
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/CN=host.opensciencegrid.org 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
If you are using OpenSSL 1.1, you may notice minor formatting differences.
Requesting InCommon IGTF Host Certificates¶
Many institutions 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, Let's Encrypt certificates do not meet your needs, and you do not have access to another IGTF CA subscription, please contact us.
As with all OSG software installations, there are some one-time (per host) steps to prepare in advance:
- Ensure the host has a supported operating system
- Obtain root access to the host
- Prepare the required Yum repositories
From a host that meets the above requirements, follow the instructions below to request a new host certificate:
[email protected] # yum install osg-pki-tools
Generate a Certificate Signing Request (CSR) and private key using the
[email protected] $ osg-cert-request --hostname <HOSTNAME> \ --country <COUNTRY> \ --state <STATE> \ --locality <LOCALITY> \ --organization <ORGANIZATION>
You may also add DNS Subject Alternative Names (SAN) to the request by specifying any number of
--altname <SAN>. For example, the following generates a CSR for
[email protected] $ osg-cert-request --hostname test.opensciencegrid.org \ --country US \ --state Wisconsin \ --locality Madison \ --organization 'University of Wisconsin' \ --altname foo.opensciencegrid.org \ --altname bar.opensciencegrid.org
If successful, the CSR will be named
<HOSTNAME>.reqand the private key will be named
<HOSTNAME>-key.pem. Additional options and descriptions can be found here.
Find your institution-specific InCommon contact (e.g. UW-Madison InCommon contact), submit the CSR that you generated above, and request a 1-year
IGTF Server Certificatefor
- After the certificate has been issued by your institution, download it on its intended host and copy over the key you generated above.
Verify that the issuer
InCommon IGTF Server CA:
$ openssl x509 -in <PATH TO CERTIFICATE> -noout -issuer issuer= /C=US/O=Internet2/OU=InCommon/CN=InCommon IGTF Server CA
Install the host certificate and key:
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.
certbotpackage (available from the EPEL 7 repository):
[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 Let's Encrypt 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:
Renewing Let's Encrypt host certificates¶
Before the host certificate expires, you can renew it with the following command:
[email protected] # certbot renew
To automate the renewal process, you need to choose between using a cron job (SL6 and SL7 hosts) and a systemd timer (SL7 hosts only). The two sections below outline both methods for automatically renewing your certificate.
Automating renewals using cron¶
To automate a monthly renewal with a cron job; you can create
/etc/cron.d/certbot-renew with the following
* * 1 * * root certbot renew
Automating renewals using systemd timers¶
To automate a monthly renewal using systemd, you'll need to create two files. The first is a service file that tells systemd how to invoke certbot. The second is to generate a timer file that tells systemd how often to run the service. The steps to setup the timer are as follows:
Create a service file called
/etc/systemd/system/certbot.servicewith the following contents
[Unit] Description=Let's Encrypt renewal [Service] Type=oneshot ExecStart=/usr/bin/certbot renew --quiet --agree-tos
Once the certbot service is working correctly, you will need to create the timer file. Create the timer file at
/etc/systemd/system/certbot.timer) with the following contents:
[Unit] Description=Twice daily renewal of Let's Encrypt's certificates [Timer] OnCalendar=0/12:00:00 RandomizedDelaySec=1h Persistent=true [Install] WantedBy=timers.target
Update the systemd manager configuration:
[email protected] # systemctl daemon-reload
Start and enable the certbot service and timer:
You can verify that the timer is active by running
Verify that the service has started correctly by running
systemctl status certbot.service. The timer may fail
without warnings if the service does not run correctly.
Requesting Service Certificates¶
Previously, the OSG recommended using separate X.509 certificates, called "service certificates", for each grid service on a host. This practice has become less popular as sites have separated SSL-requiring services to their own hosts.
In the case where your host is only running a single service that requires a service certificate, we recommend using your host certificate as your service certificate. Ensure that the ownership of the host certificate and key are appropriate for the service you are running.
If you are running multiple services that require host certificates, we recommend requesting a certificate whose
<service>-hostname and has the hostname in the list of subject alternative names.
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 signing request as long as the hostname for the certificate is a fully qualified domain name.
How do I renew a host certificate?¶
For Let's Encrypt certificates, see this section
For other certificates, there is no separate renewal procedure. Instead, request a new certificate using one of the methods above.
How can I check if I have a host certificate installed already?¶
By default the host certificate key pair will be installed in
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/CN=host.opensciencegrid.org 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?¶
Use the following
openssl command to find the dates that your host certificate is valid:
[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
- CILogon documentation for requesting InCommon certificates
Useful OpenSSL commands (from NCSA) - e.g. how to convert the format of your certificate.
Another Let's Encrypt setup reference Under Getting your host certificate, we follow the first "Setting up" section.