asetkey - Add a key from a keytab to an AFS KeyFile

asetkey add <kvno> <keyfile> <principal>

asetkey delete <kvno>

asetkey list

The asetkey command is used to add a key to an AFS KeyFile from a Kerberos keytab. It is similar to bos addkey except that it must be run locally on the system where the KeyFile is located and it takes the new key from a Kerberos 5 keytab rather than prompting for the password.

asetkey delete can be used to delete a key (similar to bos removekeys), and asetkey list will list the keys in a KeyFile (similar to bos listkeys).

asetkey is used when authentication for an AFS cell is provided by a Kerberos 5 KDC rather than kaserver. The key for the CWafs or CWafs/CIcell nameCW principal in the Kerberos 5 KDC must match the key stored in the AFS KeyFile on all AFS database servers and file servers. This is done by creating a keytab containing that key using the standard Kerberos commands (generally the CWktadd function of the kadmin command) and then, on each AFS database server and file server, adding that key to the KeyFile with asetkey add. The kvno chosen should match the kvno in the Kerberos KDC (checked with kvno or the CWgetprinc function of kadmin). principal should be the name of the AFS principal in the keytab, which must be either CWafs or CWafs/CIcell nameCW.

In cells that use the Update Server to distribute the contents of the /etc/openafs/server directory, it is conventional to run asetkey add only on the control machine and then let the Update Server propagate the new KeyFile to all other systems.

AFS currently only supports des-cbc-crc:v4 Kerberos keys. Make sure, when creating the keytab with CWktadd, you pass CW-e des-cbc-crc:v4 to force the encryption type. Otherwise, AFS authentication may not work.

As soon as a new keytab is created with CWktadd, new AFS service tickets will use the new key. However, tokens formed from those service tickets will only work if the new key is present in the KeyFile on the AFS file server. There is therefore an outage window between when the new keytab is created and when the key had been added to the KeyFile of all AFS servers with asetkey, during which newly obtained AFS tokens will not work properly.

All of the KeyFile entries must match the key in the Kerberos KDC, but each time CWktadd is run, it creates a new key. Either the Update Server must be used to distribute the KeyFile to all servers or the same keytab must be used with asetkey on each server.

The following commands create a new keytab for the principal CWafs and then import the key into the KeyFile. Note the kvno in the output from CWktadd.

    % kadmin
    Authenticating as principal rra/admin@stanford.edu with password.
    Password for rra/admin@stanford.edu:
    kadmin:  ktadd -k /tmp/afs.keytab -e des-cbc-crc:v4 afs
    Entry for principal afs with kvno 3, encryption type DES cbc mode
    with CRC-32 added to keytab WRFILE:/tmp/afs.keytab.
    kadmin:  exit
    % asetkey 3 /tmp/afs.keytab afs

You may want to use CWafs/CIcell nameCW instead of CWafs, particularly if you may have multiple AFS cells for a single Kerberos realm.

The issuer must be able to read (for asetkey list) and write (for asetkey add and asetkey delete) the KeyFile, normally /etc/openafs/server/KeyFile. In practice, this means that the issuer must be the local superuser CWroot on the AFS file server or database server. For asetkey add, the issuer must also be able to read the specified keytab file.

KeyFile(5), bos_addkey(8), bos_listkeys(8), bos_removekey(8), kadmin(8), kvno(1)

Copyright 2006 Russ Allbery <rra@stanford.edu>

This documentation is covered by the IBM Public License Version 1.0. This man page was written by Russ Allbery for OpenAFS.