SSO login and username case sensitivity

[GOLLSCHEWSKY, Tim]

Hi guys,

We've been experimenting with putty v0.61 and windows SSO authentication.  e.g.  You
log into windows with username "tim" and when then load up putty and try and
connect to a RHEL6 machine, it passes along my Windows GSSAPI credentials and
automatically logs me in to the RHEL6 box.

SSSD has been configured to talk to Active Directory like so:

   [domain/KRB5DOMAIN]
   enumerate = True
   ldap_id_use_start_tls = False
   cache_credentials = True
   id_provider = ldap
   auth_provider = krb5
   chpass_provider = krb5
   debug_level = 1

   ldap_schema = rfc2307bis
   ldap_force_upper_case_realm = True
   ldap_user_object_class = user
   ldap_group_object_class = group
   ldap_user_home_directory = unixHomeDirectory
   ldap_user_name = msSFU30Name
   ldap_user_member_of = msSFU30PosixMemberOf
   ldap_group_member = msSFU30PosixMember

   access_provider = ldap
   ldap_uri = ldap://xxxx/
   ldap_search_base = xxx
   ldap_user_search_base = xxx
   ldap_group_search_base = xxx
   ldap_sasl_mech = gssapi
   ldap_sasl_authid = xxx
   ldap_krb5_keytab = xxx
   ldap_krb5_init_creds = true
   ldap_tls_cacertdir = /etc/openldap/cacerts
   krb5_realm = xxx
   krb5_kpasswd = xxx
   krb5_server = xxx

What we're finding is Windows for some reason stores the username in UPPERCASE and
passes the uppercase value in the GSSAPI credentials.  However the username attribute in
AD (msSFU30Name) stores the username in lowercase, which is the standard for Unix
usernames and something we are very comfortable with.

Because the username comparison is case-sensitive, the user is denied access.  If we
hard-code the login name in putty to be lowercase it works, so I'm pretty sure the
GSSAPI auth is working.

So, my question is: Is there a way to make the username comparison to LDAP
case-insensitive?  Or do we need to update our AD/LDAP to uppercase all the msSFU30Name
attributes?  Or is there another option?

I understand usernames should be compared case-sensitive to be POSIX compliant.  I've
just been asked to see if I can get this to work.

BTW I've been browsing trac and it looks like you were considering a
"force_lowercase_names" config option at one point.  Is this still under
consideration?   https://fedorahosted.org/sssd/ticket/246

Best regards,

Tim Gollschewsky.

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