Grid certificates

< Getting started with SweGrid

Introduction to certificates

In order to get access to computer and storage resources on the grid or SweStore you must have a valid (grid) certificate. This certificate is used instead of a username and password when accessing the resource. The resource have a certificate that tells you that you have contacted the right resource. This is exactly the same mechanism used when you use a web browser to contact your bank.

A certificate is the similar to a passport in real-life. In the same way you have prove your credentials when you acquire a passport the same is true for a certificate. A third party, the Certificate Authority or CA, that both you and the resource trust has to vouch for your identity and sign your certificate.

A certificate consist of a public key, some user information and a signature of the CA. In addition to the certificate you have a private key. The private key is secret and should be kept as secure as possible.

For more information regarding certificates and public key cryptography:

http://en.wikipedia.org/wiki/Public-key_cryptography

http://en.wikipedia.org/wiki/Public_key_certificate

http://www.nordugrid.org/documents/certificate_howto.html

• The grid certificate and the private key are stored in your web browser and/or located in ~/.globus at the host(s) from where you will be accessing the resource:

     usercert.pem
     userkey.pem

• The certificate contains your public key, your name and organization and a signature by the CA. It is does not contain any username.
• The certificate is valid for 13 month and should be renewed yearly.
• The private key should be handled with great care. It should only be readable by you (i.e. ``chmod 400 userkey.pem). Store the key on trusted computers and transfer the key between computers using encryption (using for example scp).
• The private key is encrypted using a passphrase. Anyone that can decrypt the private key will be able to authenticate as you to grid resources. This is similar to the private key in SSH. You must choose a strong passphrase for the private key. This passphrase must not be used anywhere else. You must never ever give away the passphrase to somebody else.
• You should not share the certificate with someone. It's personal.

For more information regarding certificates and public key cryptography:

http://en.wikipedia.org/wiki/Public-key_cryptography http://en.wikipedia.org/wiki/Public_key_certificate

Requesting a certificate

Certificates are issued by a Certificate Authority or CA. For swedish users there are two CA:s that can issue certificates, Terena and Nordugrid. The Terena CA is preferred if it is available for your university or research group, but many sites has not enabled this service yet. The Nordugrid CA can also be used but requires more manual work by all parties.

Requesting membership in the SweGrid VO

To be able to use the SweGrid or Swestore resources a membership in the SweGrid VO and a corresponding group is required. To apply for membership, make sure that the Nordugrid CA and your certificate is installed in the browser.

The NorduGrid CA cert can be installed by clicking on the following link. Make sure you check all the boxes in the dialog shown.

When certifcates have been installed in the browser go to the following URL:

https://voms.ndgf.org:8443/voms/swegrid.se

and follow the instructions. In a couple of hours you will be added to the SweGrid VO.

To be added to the correct SNIC project send a mail to support@swegrid.se and specify your DN as shown in the Terena portal or from the arcproxy --info command and which SNIC-project to be added to.

To be added to the correct Swestore allocation send a mail to swestore-support@snic.vr.se and specify your DN as shown in the Terena portal or from the arcproxy --info command and which Swestore allocation to be added to.

Proxy certificates

Authentication on the grid is done using special short lived proxy certificates. There are several tools available for creating, checking and destroying these proxy certificates.

Creating a proxy certificate

To create a short lived proxy that can be used for authentication with grid services, the arcproxy command can be used. A 12 hour (default) proxy is created in the following example:

$ arcproxy
Your identity: /O=Grid/O=NorduGrid/OU=lunarc.lu.se/CN=Kalle Kula
Enter pass phrase for /home/kalle/.globus/userkey.pem:
.++++++
.....++++++
Proxy generation succeeded
Your proxy is valid until: 2011-03-11 03:00:14

The proxy file itself will be created in the /tmp directory with the format x509up_uid, where uid is the user id number for your account.

In some cases a longer lived proxy will be needed. This is achieved using the --constraint switch. A 24-hour can be created by issuing the following command:

$ arcproxy --constraint="validityPeriod=24H"
Your identity: /O=Grid/O=NorduGrid/OU=lunarc.lu.se/CN=Kalle Kula
Enter pass phrase for /home/kalle/.globus/userkey.pem:
....++++++
.....++++++
Proxy generation succeeded
Your proxy is valid until: 2011-03-11 15:03:19

Checking proxy lifetime

The remaining lifetime of a proxy certificate can be checked using the arcproxy command with the --info switch.

$ arcproxy --info
Subject: /O=Grid/O=NorduGrid/OU=lunarc.lu.se/CN=Kalle Kula/CN=1567862803
Identity: /O=Grid/O=NorduGrid/OU=lunarc.lu.se/CN=Kalle Kula
Time left for proxy: 11 hours 55 minutes
Proxy path: /tmp/x509up_u500
Proxy type: X.509 Proxy Certificate Profile RFC compliant restricted proxy

In this example the proxy certificate is valid for 11 hours 55 minutes more.

Destroying a proxy certificate

A proxy can be destroyed with the -r or --remove switch.

$ arcproxy -r

or

$ arcproxy --remove

VOMS certificates

To use the SweStore national storage resources a membership in a virtual organisation, VO, is required. When accessing the storage resources a special grid proxy certificate is required which indicates VO membership. The special proxy certificate requires that it is signed by the virtual organisation management server, VOMS. To enable this signing process, configuration files have to be added to the system. First a $HOME/.voms/vomses file with the following contents must be added:

"swegrid.se" "voms.ndgf.org" "15009" "/O=Grid/O=NorduGrid/CN=host/voms.ndgf.org" "swegrid.se"

Next the file /etc/grid-security/vomsdir/swegrid.se/voms.ndgf.org.lsc with the following contents:

/O=Grid/O=NorduGrid/CN=host/voms.ndgf.org
/O=Grid/O=NorduGrid/CN=NorduGrid Certification Authority

Creating a VOMS proxy

VOMS proxies in ARC1 can be created using the arcproxy command and the -S or --voms switches as shown in the following example:

$ arcproxy -S swegrid.se:/swegrid.se/ops
Your identity: /O=Grid/O=NorduGrid/OU=lunarc.lu.se/CN=Kalle Kula
Enter pass phrase for /home/kalle/.globus/userkey.pem:
.....++++++
............++++++
Contacting VOMS server (named swegrid.se): voms.ndgf.org on port: 15009
Proxy generation succeeded
Your proxy is valid until: 2011-03-10 23:33:06