I have problems setting krb5 auth with an xrootd service. The following user principal

KVNO Timestamp         Principal
---- ----------------- --------------------------------------------------------
   3 01/01/70 01:00:00 [log in to unmask]

obtains the ticket-granting ticket (krgbt) by doing: kinit -kt ./cta-adm-HOST.keytab [log in to unmask]

and then issues admin commands on a host called cta-adm.scd.rl.ac.uk and these commands need to be authorised by an
XRootD service (the XRootD instance name is cta  and the systemd name is cta-frontend.service) running on another host
called cta-front01.scd.rl.ac.uk. The krb5 auth for this service is configured as

sec.protocol krb5 /etc/cta/cta-frontend.krb5.keytab [log in to unmask]
sec.protbind * only sss krb5

where the contents of /etc/cta/cta-frontend.krb5.keytab are

KVNO Timestamp         Principal
---- ----------------- --------------------------------------------------------
   3 01/01/70 01:00:00 [log in to unmask]

However, any attempt to issue admin commands result in the following error on the xrootd log of this cta service

210513 13:58:45 32387 XrootdXeq: User authentication failed; Seckrb5: Unable to extract client name;; No translation available for requested principal ([log in to unmask])

This is thrown by this part of the code in XrdSeckrb5/XrdSecProtocolkrb5.cc

// Decode the credentials and extract client's name
   if (!rc)
      {if ((rc = krb5_rd_req(krb_context, &AuthContext, &inbuf,
                             krb_keytab, NULL, &Ticket)))
           iferror = (char *)"Unable to authenticate credentials;";
       else if ((rc = krb5_aname_to_localname(krb_context,
                                  sizeof(CName)-1, CName)))
             iferror = (char *)"Unable to extract client name;";

Do you know what is the problem?

Many thanks.


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