[krbdev.mit.edu #7296] issues in handling special characters in KDC ldap plugin code

[Greg Hudson via RT]

More work on this issue is required.  Some notes from my work so far:

* Bug #1: krb5_ldap_put_principal() is not encoding the unparsed 
principal name for use as a DN, so putting a principal with DN-special 
characters tends to fail.

* Bug #2: krb5_ldap_name_to_policydn() uses ldap_filter_correct() to 
quote special characters.  But the special characters for a filter 
expression are not the same as the special characters for a DN.

* The patch here corrects bug #1 and tries to correct bug #2 by adding 
some of the special DN characters to ldap_filter_correct().  But it 
doesn't get all of them.

* If ldap_filter_correct() is amended to quote all of the special 
characters for DNs, iteration over policies and principals still 
produces incorrect results.  For instance, a policy named "<test*>", 
encoded to "\\3ctest\\2a\\3e" by our code for use as a DN, comes back as 
"\\3Ctest*\\3E" in iteration.  The iteration code is using 
ldap_get_values() to extract the cn of the policy entry.  I have not yet 
determined why the LDAP code represents the string that way or how best 
to work around it (maybe using ldap_get_values_len?)