krb5_keytab_intro(3)        HeimdalKerberos5library       krb5_keytab_intro(3)

NAME
       krb5_keytab_intro - The keytab handing functions

Kerberos Keytabs
       See the library functions here: Heimdal Kerberos 5 keytab handling
       functions

       Keytabs are long term key storage for servers, their equvalment of
       password files.

       Normally the only function that useful for server are to specify what
       keytab to use to other core functions like krb5_rd_req()
       krb5_kt_resolve(), and krb5_kt_close().

   Keytab names
       A keytab name is on the form type:residual. The residual part is
       specific to each keytab-type.

       When a keytab-name is resolved, the type is matched with an internal
       list of keytab types. If there is no matching keytab type, the default
       keytab is used. The current default type is FILE.

       The default value can be changed in the configuration file
       /etc/krb5.conf by setting the variable [defaults]default_keytab_name.

       The keytab types that are implemented in Heimdal are:

       •ile store the keytab in a file, the type's name is FILE . The
         residual part is a filename. For compatibility with other Kerberos
         implemtation WRFILE and JAVA14 is also accepted. WRFILE has the same
         format as FILE. JAVA14 have a format that is compatible with older
         versions of MIT kerberos and SUN's Java based installation. They
         store a truncted kvno, so when the knvo excess 255, they are truncted
         in this format.

       •eytab store the keytab in a AFS keyfile (usually
         /usr/afs/etc/KeyFile ), the type's name is AFSKEYFILE. The residual
         part is a filename.

       •emory The keytab is stored in a memory segment. This allows
         sensitive and/or temporary data not to be stored on disk. The type's
         name is MEMORY. Each MEMORY keytab is referenced counted by and
         opened by the residual name, so two handles can point to the same
         memory area. When the last user closes using krb5_kt_close() the
         keytab, the keys in they keytab is memset() to zero and freed and can
         no longer be looked up by name.

   Keytab example
       This is a minimalistic version of ktutil.

       int
       main (int argc, char **argv)
       {
           krb5_context context;
           krb5_keytab keytab;
           krb5_kt_cursor cursor;
           krb5_keytab_entry entry;
           krb5_error_code ret;
           char *principal;

           if (krb5_init_context (&context) != 0)
               errx(1, 'krb5_context');

           ret = krb5_kt_default (context, &keytab);
           if (ret)
               krb5_err(context, 1, ret, 'krb5_kt_default');

           ret = krb5_kt_start_seq_get(context, keytab, &cursor);
           if (ret)
               krb5_err(context, 1, ret, 'krb5_kt_start_seq_get');
           while((ret = krb5_kt_next_entry(context, keytab, &entry, &cursor)) == 0){
               krb5_unparse_name(context, entry.principal, &principal);
               printf('principal: %s0, principal);
               free(principal);
               krb5_kt_free_entry(context, &entry);
           }
           ret = krb5_kt_end_seq_get(context, keytab, &cursor);
           if (ret)
               krb5_err(context, 1, ret, 'krb5_kt_end_seq_get');
           ret = krb5_kt_close(context, keytab);
           if (ret)
               krb5_err(context, 1, ret, 'krb5_kt_close');
           krb5_free_context(context);
           return 0;
       }

Version 1.5.2                     11 Jan 2012             krb5_keytab_intro(3)