=head1 NAME

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

=head1 SYNOPSIS

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<div class="synopsis">

B<asetkey> add <I<kvno>> <I<keyfile>> <I<principal>>

B<asetkey> add <I<kvno>> <I<key>>

B<asetkey> add <I<type>> <I<kvno>> <I<subtype>> <I<key>>

B<asetkey> add <I<type>> <I<kvno>> <I<subtype>> <I<keyfile>> <I<princ>>

B<asetkey> delete <I<kvno>>

B<asetkey> delete <I<type>> <I<kvno>>

B<asetkey> delete <I<type>> <I<kvno>> <I<subtype>>

B<asetkey> list

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</div>

=head1 DESCRIPTION

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

B<asetkey delete> can be used to delete a key (similar to B<bos
removekeys>), and B<asetkey list> will list the keys in a KeyFile
and the keys in a KeyFileExt (similar to B<bos listkeys>, but more
fully featured, since B<bos listkeys> cannot list the contents of
a KeyFileExt).

B<asetkey> is used when authentication for an AFS cell is provided by a
Kerberos 5 KDC rather than the deprecated B<kaserver>.
The key for the C<afs> or
C<afs/I<cell name>> principal in the Kerberos 5 KDC must match the key
stored in the AFS KeyFileExt 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 C<ktadd> function of the B<kadmin>
command) and then, on each AFS database server and file server, adding
that key to the KeyFileExt with B<asetkey add>.  The I<kvno> chosen should
match the kvno in the Kerberos KDC (checked with B<kvno> or the
C<getprinc> function of B<kadmin>).  I<principal> should be the name of
the AFS principal in the keytab, which must be either C<afs> or
C<afs/I<cell name>>.

=head1 CAUTIONS

Historically, AFS only supported des-cbc-crc:v4 Kerberos keys.  In environments
which have not been upgraded to use the rxkad-k5 extension, when
creating the keytab with C<ktadd>, you must pass C<-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 C<ktadd>, 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 KeyFileExt 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 KeyFileExt of all AFS
servers with B<asetkey>, during which newly obtained AFS tokens will not
work properly.

All of the KeyFileExt entries must match the key in the Kerberos KDC, but
each time C<ktadd> is run, it creates a new key.  Some secure mechanism
must be used to distribute the KeyFileExt to all servers,
or the same keytab must be used with B<asetkey> on each server.

=head1 EXAMPLES

In a cell which is using the rxkad-k5 extension, the following commands
create a new keytab for the principal C<afs/I<cell name>> and then import
its keys into the KeyFileExt.  Note the kvno in the output from C<ktadd>.
The values 18, 17, and 16 are the assigned numbers corresponding to the
kerberos enctypes in the keytab.  These numbers can be determined from your
system's krb5 headers.

    % kadmin
    Authenticating as principal kaduk/admin@ZONE.MIT.EDU with password.
    Password for kaduk/admin@ZONE.MIT.EDU:
    kadmin:  ktadd -k /tmp/afs.keytab afs/disarray.mit.edu
    Entry for principal afs/disarray.mit.edu with kvno 4, encryption type
    aes256-cts-hmac-sha1-96 added to keytab WRFILE:/tmp/afs.keytab.
    Entry for principal afs/disarray.mit.edu with kvno 4, encryption type
    aes128-cts-hmac-sha1-96 added to keytab WRFILE:/tmp/afs.keytab.
    Entry for principal afs/disarray.mit.edu with kvno 4, encryption type
    des3-cbc-sha1 added to keytab WRFILE:/tmp/afs.keytab.
    kadmin:  exit
    % asetkey add rxkad_krb5 4 18 /tmp/afs.keytab afs/disarray.mit.edu
    % asetkey add rxkad_krb5 4 17 /tmp/afs.keytab afs/disarray.mit.edu
    % asetkey add rxkad_krb5 4 16 /tmp/afs.keytab afs/disarray.mit.edu

=head1 PRIVILEGE REQUIRED

The issuer must be able to read (for B<asetkey list>) and write (for
B<asetkey add> and B<asetkey delete>) the KeyFileExt, normally
F</usr/afs/etc/KeyFileExt>.  In practice, this means that the issuer must be
the local superuser C<root> on the AFS file server or database server.
For B<asetkey add>, the issuer must also be able to read the specified
keytab file.

=head1 HISTORICAL COMPATIBILITY

A modern AFS cell should be using the rxkad-k5 extension, or risks
terribly insecure operation (complete cell compromise for $100 in
1 day).  The keys used for rxkad-k5 operation are stored in the
KeyFileExt.  Cells not using the rxkad-k5 extension (i.e., stock
rxkad) use keys of the des-cbc-crc encryption type, which are stored
in the KeyFile.

B<asetkey> retains the functionality needed to support stock rxkad
operation, but its use is disrecommended.  A bare 8-byte hex key
can be added with

    % asetkey add I<kvno> I<key>

I<key> should be an 8 byte hex representation.  An example using
a kvno of 3:

    % asetkey add 3 80b6a7cd7a9dadb6

The following commands create a new keytab for the principal C<afs>
and then import the key into the KeyFile.  Note the kvno in the
output from C<ktadd>.

    % 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 add 3 /tmp/afs.keytab afs

You may want to use C<afs/I<cell name>> instead of C<afs>, particularly if
you may have multiple AFS cells for a single Kerberos realm.

=head1 SEE ALSO

L<KeyFile(5)>,
L<KeyFileExt(5)>,
L<bos_addkey(8)>,
L<bos_listkeys(8)>,
L<bos_removekey(8)>,
kadmin(8),
kvno(1)

=head1 COPYRIGHT

Copyright 2006 Russ Allbery <rra@stanford.edu>
Copyright 2013,2015 Massachusetts Institute of Technology

This documentation is covered by the IBM Public License Version 1.0.  This
man page was written by Russ Allbery for OpenAFS and updated for the
rxkad-k5 extension by Benjamin Kaduk.
